New Electronics 13 September 2011

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13 September 2011

GPGPUS IN EMBEDDED APPS • CUTTING CABLES • HW/SW CODESIGN UPDATE

Securing supplies of rare earth elements

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Contents Vol 44 No 16

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Interview

Seeing the light Few people can reasonably claim to have been there at the start of an industry. We talk with a plastic electronics pioneer

Scarcity value

Got a problem? See if the Forum can help you solve it

Rare earth elements are vital to the electronics industry, but one country supplies 97% of the world’s needs

Comment

Cover Story 16

Defence

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Breaking performance barriers High performance computing capability is becoming available to military embedded applications developers EDA 7

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Brave new world As hardware becomes more complex and software dominates design, the eda sector is entering into a new world Micros

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GPGPUs set to enter the mainstream General purpose graphic processing units are set to play a greater role in embedded systems applications 31

RF & Microwave

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Cutting cables WIth demand growing for wireless links, what options are available to the design engineer? Engineering MAnagement

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Go with the flow 36

Design flow developments are enabling more capable signal processing and communications systems

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UK electronics companies can help to reverse the decline in interest in electronics careers News

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Working group to produce strategic report on the prospects for the UK’s electronics system sector IBM researchers are working on cognitive chips; devices that look to emulate the brain’s abilities The shortlist for this year’s BEEAs shows once again that UK industry is creating innovative solutions

Technology Watch

Material swirl

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Apparently humble, capacitors can be considered as one of the first nanotechnology products

Efficiency drive 39

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Moving on from a focus on peak efficiency, power supply design is now a more holistic process

13 September 2011

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www.newelectronics.co.uk/forum Your electronics community discussion board Group Editor: Graham Pitcher Web Editor: Chris Shaw Deputy Web Editor: Laura Hopperton Contributing Editors: David Boothroyd, Chris Edwards, Louise Joselyn, Roy Rubenstein Art Editor: Martin Cherry Illustrator: Phil Holmes Key Account Director: Tricia Bodsworth Classified Sales: James Slade Circulation Manager: Chris Jones ([email protected]) Production Controller: Nicki McKenna Publisher: Peter Ring Executive Director: Ed Tranter Represented in Japan by: Shinano International: Kazuhiko Tanaka, Akasaka Kyowa Bldg, 1-6-14 Akasaka, Minato-Ku, Tokyo 107-0052 Tel: +81(0)3 3584 6420 New Electronics: Tel: 01322 221144 Fax: 01322 221188 www.newelectronics.co.uk email: [email protected]

ISSN 0047-9624 New Electronics, incorporating Electronic Equipment News and Electronics News, is published twice monthly by Findlay Media Ltd, Hawley Mill, Hawley Road, Dartford, Kent, DA2 7TJ Copyright 2011 Findlay Media. Annual subscription (22 issues) for readers in the UK is £106, overseas is £161, and airmail is £197. Origination by CTT, Walthamstow, London E17 6BU Printed in England by Wyndeham Heron Ltd, Heybridge, CM9 4NW

Investing in the future Convincing students of the value of a career in the electronics industry

nterest in engineering as a career has been declining for some years. A number of reasons have been suggested, ranging from the fact that engineering is just ‘too hard’ via no jobs and poor salaries to other sectors being ‘sexier’. What to do about it has been a harder problem to solve, but one which has been grasped by the UK Electronics Skills Foundation (UKESF, www.ukesf.org). It has started with modest ambitions; demonstrating to a limited number of pre university students that there are, indeed, prospects in the electronics industry. This has been followed by a summer school in which a selection of current electronics students – UKESF scholars – received targeted presentations outlining what is expected of them by prospective employers. The journey, as they say, starts with the first step. The issue of graduate skills continues to bubble up; employers have commented with regularity over the years that the graduates they employ don’t have the necessary ‘soft’ skills: ranging from numeracy to interpersonal relations to team working. Solving this problem requires universities to refocus their teaching, something that may encounter a

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degree of resistance. Nevertheless, UKESF believes it can make change happen. Reversing the decline of interest in electronics engineering will take time and effort, but what will help is broad support from the electronics industry. There’s a range of things which can be done, such as helping to finance a student to go to university or providing someone with work experience. Why not see how you can support the UKESF’s work? Congratulations to all those who have made the shortlist for the British Engineering Excellence Awards. Once again, the Awards have shown that UK engineering is providing innovative solutions to problems in a range of markets.

Moving on? If you change jobs or your company moves, please contact [email protected] to continue receiving your free copy of New Electronics

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Graham Pitcher, Group Editor ([email protected])

13 September 2011

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E lectro n i c Syste m s Secto r News

Electronics systems on report Working group to plot the future for the UK’s electronics systems sector. Graham Pitcher reports.

The Government has commissioned the NMI to produce a strategic report into the future of the UK’s electronics systems community. The work will examine opportunities for the sector and ways in which recommendations can be supported. The work will be chaired by ex ARM executive Jamie Urquhart, pictured, who will be joined by a

group of industry leaders. He hopes the report will publish in advance of the target of Q2 2012. According to Urquhart: “The UK has a broad spread of companies who are largely invisible, but whose technology appears in exciting products. The report gives the opportunity to take a longer term view again.” In one respect, the report appears to be a reprise of the work undertaken by the Electronics Innovation and Growth Team, which produced a 10 year plan in 2005. But Urquhart said: “It’s a matter of understanding what we have and how to give the sector a more strategic direction.” However, he accepted the challenge would be how to create action. Mark Prisk, minister for business and enterprise, said the report would help the Government to understand how it can improve the sector’s competitiveness. “Electronic systems are prevalent in new markets and virtually every business sector. The UK’s strength in this sector gives the potential to make an even bigger impact on global markets.” To participate, contact: [email protected]

Glue to build chip ‘towers’ 3M and IBM plan to develop adhesives that can be used to package semiconductors into silicon ‘towers’. Using this new class of materials, the companies believe it will be possible to build devices comprising up to 100 separate chips. Such stacking would allow for much higher levels of integration. As an example, the companies suggest processors could be tightly packed with memory and networking elements to create a silicon ‘brick’ that would be significantly faster than current parts, in turn, enabling more powerful end user products. Bernie Meyerson, IBM’s vp of research, said: “Our scientists are aiming to develop materials that will allow us to package tremendous amounts of computing power into a new form factor – a silicon ‘skyscraper.’ We believe we can create a new class of semiconductors that offers more speed and capabilities while they keep power usage low.” www.ibm.com

Looking to the future Leaders from UK electronics companies are backing the efforts of the UK Electronics Skills Foundation (UKESF) to better prepare graduates for an electronics career. Selected students from UK universities, called UKESF Scholars, attended professional development sessions designed to complement their academic studies. Indro Mukerjee, chair of the UKESF’s strategic advisory board, explained the course. “These students will be learning things which take

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them beyond their academic subjects; things related to a career in the electronics industry.” Tom Dell, studying for an MEng in Electronic Engineering at the University of Southampton, said: “My summer placement with Aptina Imaging gave me a fantastic insight into the semiconductor industry. The workshop has built on this by introducing me to some of the management skills I need to develop.” Tony King-Smith, vp of marketing with Imagination Technologies, said: “We’re helping students to get the right skills and to find out what it’s like to work in industry.” www.ukesf.org

Spin waves verified Experiments performed by researchers in Sweden have verified theories about nanoscale spin waves. The move is said to pave the way for microwave technology to be replaced by components that are smaller, cheaper and require fewer resources. The work is likely to open up research into the new field known of magnonics. Professor Johan Åkerman of the University of Gothenburg, said: “Our results will signal the start of a rapid development of magnonic components and circuits. These components are powered by simple direct current, which is then converted into spin waves in the microwave region. The frequency of these waves can be directly controlled by the current. This will make completely new functions possible.”

Tantalum shortage? Buyers of electronic components have been warned in a recent report that they could have difficulty sourcing tantalum following the recent closure of a number of mines. The report, from Merchant Research and Consulting, claims global tantalum supply has been cut by 40%. In its pure form, tantalum forms one of two conducting plates on which charge is stored in capacitors. Its oxide is an excellent insulator, preventing current leakage between the plates. • For more on rare earth elements, see the cover story on p16

Graphene based flash Work by a team from the University of California Los Angeles, along with researchers from Samsung, suggests that a combination of graphene and silicon may extend flash’s lifespan beyond the 22nm node. “We’re not totally replacing silicon, but using graphene as the storage layer,” said UCLA researcher Augustin Hong. “We’re using graphene to help extend the capabilities of the conventional technology.” The graphene flash prototypes can be read from and written to using less power than conventional flash and can store data more stably over time, even when miniaturised. Simulation suggests the devices could scale to the 10nm node.

13 September 2011

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News Cognitive Chips

Learning from experience IBM starts work on cognitive chips which learn through experience. Graham Pitcher reports. IBM researchers are developing a range of experimental devices designed to emulate the brain’s perception, action and cognition abilities. The technology could result in computers which consume much less power and take up less volume than current devices. The goal of the SyNAPSE project is to create a system that not only analyses complex information from multiple sources, but which can also rewire itself dynamically as it interacts with the environment. The devices, called cognitive computers, are expected to learn through experience, to find correlations and create hypotheses. IBM is combining principles from nanoscience, neuroscience and supercomputing as part of the initiative, which has received $21million in funding. Project leader Dharmendra Modha claimed: “This is a major initiative to move beyond the von Neumann paradigm that has been ruling computer architecture for more than half a century.” The first cognitive computing prototypes, inspired by neurobiology, form a ‘neurosynaptic core’, with integrated memory (synapses), computation (neurons) and communication (axons). Two prototypes have been created so far: both have been made using a 45 nm SOI-CMOS and contain 256 neurons. While one core contains 262,144 programmable synapses, the other contains 65,536 learning synapses. The long term goal is said to be a system with 10billion neurons and 100trillion synapses, which consumes 1kW and which occupies less than two litres. www.ibm.com

Tektronix claims new test category Tektronix has launched what it claims to be the first device in a new category of test equipment. Called the mixed domain oscilloscope, the devices in the MDO4000 series combine the functionality of oscilloscopes and spectrum analysers in one box. Roy Siegel, general manager of Tektronix’ scopes business, said the mixed domain oscilloscope ‘is the biggest development in test technology for 20 years’. “It’s about providing designers with more test time, rather than them spending time learning to use new equipment. It’s the only device that allows the engineer to look at analogue, digital and rf signals.” According to Tektronix, the device’s functionality goes beyond that of a spectrum analyser by allowing users to capture time correlated analogue, digital and rf signals across one rf, four analogue and 16 digital channels. RF input frequency extends to 6GHz and there is a capture bandwidth of at least 1GHz at all centre frequencies. This, says the company, is 100 times wider than provided by a typical spectrum analyser. The MDO4000 also allows users to see the rf spectrum of a signal at any point within a long acquisition to see how the spectrum changes over time or with device state. www.tek.com

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Co g n itive Ch i ps News

Solar cell efficiency boost

Energy harvesting cpus?

Belgian research centre imec, Plextronics and Solvay have developed an organic polymer based single junction solar cell with an efficiency of 6.9%. The cell, which combines imec’s scalable inverted device architecture and Plextronics’ polymers, is said to offer new levels of cell efficiency. The dedicated inverted bulk heterojunction architecture developed by imec has brought a 0.5% improvement in device performance over standard architectures used for organic solar cells. A buffer layer has been included in the active layer to optimise light management. This, combined with Plextronics’ low band gap p-type polymer with a fullerene derivate, has resulted in the highest efficiency yet reported for inverted architectures, which are being developed as a way to extend the lifetime of organic solar cells. www.imec.be

Qonverge SoCs sampling Freescale is now sampling the PSC9130/31 and PSC9132 SoCs from its Qonverge family, aimed at femtocell and picocell applications respectively. The PSC9130/31 femtocell SoCs support eight to 16 simultaneous users, while the PSC9132 will handle up to 64 simultaneous users. Each part features the StarCore SC3850 dsp, as well as the Power Architecture e500 mpu core. While the 9130/31 have one of each, the 9132 boasts two dsp cores and dual e500s. However, all parts can offloading Layer 2 processing and above to the mpu cores, delivering ‘significant efficiency advantages’. www.freescale.com

Variant RO-MIL-2212A RO-MIL-2212B Dimensions (wxdxh): Weight:

A $1.75million research project underway at a US university could enable energy efficient, battery free computing devices with substantially more processing power. The initiative, which involves scientists from Virginia Commonwealth University and the Universities of Michigan and California, aims to realise a low energy computing device. Supriyo Bandyopadhyay, professor of electrical and computer engineering at Virginia, and his team are hoping to build processors that can produce their own energy through energy harvesting. He believes that if transistors are replaced with nanomagnets that can also process digital information, heat dissipation could be reduced by up to 10,000 times. “This type of digital computing system could be ideal for medical devices, such as processors ... that monitor brain signals to warn of impending seizures. This processor would run by harvesting energy only from the patient’s head movements.”

Input Output 28V 12V 10A 28V 15V 8A 76.3 x 38.2 x 10.2mm 60g max

Variant RO-MIL-2213A RO-MIL-2213B Dimensions (wxdxh): Weight:

Input Output 28V 3.3V 20A 28V 5V 20A 76.3 x 38.2 x 10.2mm 60g max

Independent British Founded 1956 Quite unique in this day and age

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www.newelectronics.co.uk/forum here are some live forum topics. do you have an answer? • ASIC/SoC/FPGA Can someone explain exactly what back-annotation and forward annotation means in a SAIF file? • EDA/Board Level Design How do I combine Spice, IBIS, S-parameter, package and pc-board models? • Embedded Software Development Can you recommend electronic & communication engineering softwares under Linux environment? • Legislation New CE Mark Directive and the RoHS Recast e-book • Micros Can you suggest an mcu seriesthat can be programmed serially? • Mixed Signal & Analogue What's the difference between PWM and PDM? • Power Current mode/voltage mode; what's the difference? • Test & Measurement Network analyser measurement query • Other Technologies Can anyone tell me which type of Schmitt trigger is suitable for my design?

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Most popular News

Technology BEEAS 2011 Shortlist announced

Serving up a new approach

Findlay Media has announced the shortlist for the 2011 British Engineering Excellence Awards (BEEAs). The shortlist was selected by a panel of judges drawn from a cross section of electronic and engineering design disciplines.

Social networking pioneer Facebook is leading efforts to address data centre energy consumption with the launch of the Open Compute project. While the goal of the project is to develop an open forum to drive data centre efficiency, the initiative has grown out of Facebook's desire to be as green as it can.

DRAM manufacturers must transition process nodes downward, warns IHS

Issues and solutions for variation aware custom IC design

DRAM manufacturers risk major losses if they do not transition to more efficient 3x/2x nanometre process technologies, according to IHS iSuppli. The technologies are already employed by leading memory suppliers at a time when prices in the dynamic random access memory industry are diving to low levels.

In today's highly competitive semiconductor industry, profitability hinges largely on advantageous design performance, high yield and rapid time to market. As leading edge designs push into smaller process nodes, this is becoming even more evident.

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Implantable chip could ease treatment of cancer Researchers are developing an electronic sensor chip that could be implanted in patients to monitor tumours. The implanted chip has been designed by a team of technicians from the Technical University, Munich, to determine the oxygen content in tissue fluid, then send data wirelessly to physicians.

Video Watch that capacitor RMS ripple current rating! In this Power Tip, Robert Kollman discusses a mistake often made by designers: putting too much ripple current into a capacitor, a move that may shorten its lifetime.

ADVANCED NAND TECHNOLOGY FROM TOSHIBA As demand for memory becomes more focused on higher densities, single packages and smaller chip sizes, you need cutting edge, reliable technology from the industry leaders. Toshiba’s line up of MLC NAND products includes the world’s first 32nm 128GB e•MMC™. These embedded NAND flash multichip BGA packaged memories with an integrated controller minimise development and ease integration into system designs. For industrial applications requiring increased endurance in longer product life cycles, our SLC NAND products are available with capacities up to 64Gbit in 43nm. And, our advanced process technology innovations mean that we will soon be introducing 32nm SLC NAND and 24nm MLC NAND based e•MMC™. For further information on our complete range of NAND technology, visit www.toshiba-components.com/memory

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News B r iti s h E n g i n e e r i n g E xc e lle n c e Awar ds

Excellence exemplified BEEAs shortlist shows UK engineering is in good shape. Graham Pitcher reports. Entries to the 2011 British Engineering Excellence Awards have once again shown that UK engineering design is in good shape. At the judging session on 1 September, the judges whittled down the entries to create a shortlist with 53 entries from 48 companies and individuals. Now, it is only a short wait until the winners are announced on 13 October at the Awards Luncheon, being held at Shakespeare’s Globe Theatre in London.

Findlay Media established the British Engineering Excellence Awards in 2009 to demonstrate the quality of engineering design within the UK. The Awards are not only designed to emphasise innovation and effectiveness, but also to provide a benchmark of excellence from which the industry can learn and from which it can build. Colin Brown, chairman of the judges, said: “The British Engineering Excellence Awards are the

opportunity to showcase our best products and solutions. To receive one of the Awards is a massive endorsement to any company or individual and is public confirmation of superiority. To win overall is to be world leading and there can be no higher accolade. As a proud Chartered Engineer, I am confident not only in the abilities of the UK’s engineering sector, but also in its world class skill and innovation.” Winners of the British Engineering Excellence Awards will be included in the 25 October issue of New Electronics and on the BEEAs website. www.beeas.co.uk

The following companies have been shortlisted for the 2011 British Engineering Excellence Awards. Congratulations to all of the shortlisted companies

Consultancy of the Year, sponsored by Prototype Projects ByteSnap Magna Parva Plextek Triteq Vocis Design Engineer of the Year, sponsored by Mouser Electronics Shaun Addy, Cubewano Robert Elliott, ARM Steve Naday, Dexela Design Team of the Year, sponsored by element 14 Aber Instruments, Futura Design Team Artemis Intelligent Power, Wind Turbine Transmission Design Team IHC Engineering Business, Saipem J-Lay Tower Team Nexeon, Silicon Anode Design Team Pelamis Wave Power,

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13 September 2011

P2 Wave Energy Converter Team TDK-Lambda, EFE400M Design Team Electronic Product of the Year, sponsored by Digi-Key Bridgeworks, SANSlide ISDI/University of Lincoln, DynAMITe Imager Oxford Digital, Simulink-2-TINY RF Engines, ChannelCore FLEX Triteq, Eykona Wound Imaging System Wolfson Microelectronics, WM5100 Green Product of the Year, sponsored by National Instruments Ashwoods Automotive, Hybrid Drive System e2v technologies, ProWave Vermiculite Processing System Enecsys, Duo Solar PV Micro Inverter HT Products, LS-R Calibrated Reference Leak TDK-Lambda, GWS250

Mechanical Product of the Year, sponsored by igus (UK) Aceon Battery Technology, Solar Docking Station Cybaman Technologies, Cybaman Replicator Edwards Vacuum, GXS Dry Screw Vacuum Pump Fireco, Freedor Libralato Holdings, Pure Hybrid Powertrain MAS Design, Pacific IF folding bicycle Mechatronic Product of the Year Artemis Intelligent Power, Digital Displacement Wind Turbine Transmission CTR Future, TMX90 Laser Machine Magna Parva, COPMA System Rail-Ability, Rail-Reach 500-900 RF Golf, RF Golf Ball System Specialised Imaging, Tracker 2

Small Company of the Year, sponsored by D Young and Co LLP Huxley Bertram Engineering ICS Electronics Oxford Digital Oxford Technical Solutions Peratech Race Technology Sprint Electric Start Up of the Year, sponsored by Cambridge Consultants Cambridge CMOS Sensors Neul Redtail Telematics TBS Cubed Young Design Engineer of the Year, sponsored by RS Components Daniel Campling, Undergraduate Will Deacon, ARM Adam James, Xtrac Darren Jones, Fireco

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Interview Professor Donal Bradley

Seeing the light Graham Pitcher talks to a researcher who was ‘there at the start’ of the plastic electronics industry. ew people can reasonably claim to have been ‘there at the start’ of an materials and conjugated polymers. There are a lot of similarities,” he said, industry; Professor Donal Bradley was. His PhD at the University of “but Samsung’s success has shown there is real opportunity.” Cambridge’s Cavendish Laboratory focused on conjugated polymers; There has also been the awareness that plastic electronics technology work that would result in the establishment of Cambridge Display Technology could be used for things other than displays. “There has been a lot of work on (CDT) and a new industry – broadly categorised as ‘plastic electronics’. transistors, for example by Plastic Logic,” Prof Bradley pointed out. “And there So what was the attraction? “If you wanted to work in solid state at that has been an increase in interest in lighting applications, where the technology time,” he said, “it was all about low dimension semiconductors and the use of used to make displays can be applied to create larger area elements.” molecular beam epitaxy to create intricate structures. But people were also Prof Bradley admits that getting plastic electronics technology out of the beginning to think about using organic materials for semiconductors.” lab remains a challenge. “Part of the reason is that the UK has lost a lot of the Prof Bradley explained that he had always been larger companies that would have had an interest in interested in chemistry, as well as physics. “The these developments.” “There is exceptionally interface between the two seemed an interesting area in He said it is easier for Japanese companies, such as which to work, but I was coming at the problem from the strong university activity Sony, to pull technology through. “But there’s also the organic semiconductor side, rather than from the point scale of investment needed to commercialise the in the UK, but other of view of III-V materials.” technology,” he added. “Samsung is spending billions of Early work in organic materials research focused on parts of the world are dollars to improve device performance, while LG is the development and synthesis of conducting spending $3billion on an oled tv plant. The UK has seen catching up” materials that might act as metal replacements. “We start ups, but that is difficult to translate into major scale thought they would be better, weigh less and have activity and those companies tend to be bought.” better processability,” he recalled. “But we were also thinking about making Attempts to bring scale to the problem are being made through the optical switches with non linear properties.” establishment of plastic electronics Centres of Excellence; Prof Bradley is His PhD focused on how to process polymers in order to make ‘interesting director of one such centre located at Imperial College. “We also have hopes structures’. “I was looking to better understand physical properties,” he for Technology and Innovation Centres (TICs), but the level of investment explained, “understanding how charge was transported and some emission and support doesn’t look so encouraging in terms of them being able to properties.” But work by others had shown that organic materials could act as make a major impact.” leds and that sent Prof Bradley off in a new direction; into an area in which, he Nevertheless, Prof Bradley believes the UK remains a world leader in said, there ‘wasn’t a lot going on’. plastic electronics, at least for the moment. “There is exceptionally strong That new direction saw him working with CDT cofounders Richard Friend university activity in the UK, but other parts of the world are catching up. The and Jeremy Burroughes. “Richard had been looking to do organic transistors,” UK is still well placed and is one of the nations that people mention as a leader. Prof Bradley noted, “and organic leds came out of a discovery that involved But we can’t afford to be complacent because there are a lot of strong groups Richard, Jeremy and myself.” in other places who are forging ahead.” The resulting patent application described ‘an electroluminescent device Looking forward, Prof Bradley is turning his attention to photonics. “I’m comprising a semiconductor layer in the form of a thin dense polymer film ...’. researching organic materials as gain media for lasers. I’m also doing a lot of Prof Bradley was the corresponding author for the 1990 paper, published in work with metal oxide systems, using solution based approaches with a range Nature, that reported the discovery of conjugated polymer of fabrication methods. Zinc oxide and GaInZnO are very attractive options for electroluminescence. This paper – the most cited paper in molecular displays, where we’re looking to repace polysilicon.” electronic materials history – is believed to have launched plastic electronics. Prof Bradley believes UK science has had a good decade in terms of But plastic electronics has had a long gestation period. “The technology has funding in a period of change. “But we are being asked to justify more directly only been shown to be commercial in the last couple of years,” he said, “mostly the connection between investment in science and the impact of the work. I through the use of an active matrix oled in the Samsung Galaxy phone.” don’t think that’s a negative thing, but we have to be careful that we don’t Ironically, that technology derives from work originally performed by neglect the fundamental components of science in order to do more applied Kodak. “Our work has gone on in parallel, focusing on solution processed science. We need to preserve our strengths while looking for opportunities.”

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www.newelectronics.co.uk

13 September 2011 15

Rare earth elements are vital to the electronics industry, but one country supplies 97% of the world’s needs. By David Boothroyd. hat do ics, lasers, optical fibres, capacitors, displays and headphones have in common? Answer: they are all electronic products that depend on one or more of the rare earth elements. And that list is far from complete. There are 17 rare earth elements, all vital to the electronics industry in some form. Yet, despite their name, some rare earth elements are relatively plentiful: cerium is, apparently, as abundant as copper. They are regarded as ‘rare’ because deposits of these elements are generally not exploitable commercially. Though typically used in relatively small quantities per product, a major worry has emerged recently about the guaranteed continuation of their supply – some 97% of rare earths are currently supplied by China. Over the last few years, China has been reducing its exports of rare earths and recently cut back more drastically, by around 70%. And an ominous note was sounded when China completely halted supplies to Japan after a row about Japan’s arrest of a Chinese boat captain. He was released and supplies resumed. Squabbles aside, the prediction is that, within a few years, China will need its entire output of rare earths to satisfy its own domestic demand. So action is being taken to avoid the drastic scenario of the supply of rare earths simply coming to a halt (see below). If it did, it is astonishing how many electronic products we use every day would become either much more difficult – even impossible – to make or much more expensive. Take one of the most widely used rare earths – neodymium. It was first used to generate the light in green laser pointers, but then it was found that, when mixed with iron and boron, neodymium makes magnets that are weight for weight 12 times stronger than conventional iron magnets. Result: neodymium magnets are used in in-ear headphones, microphones, loudspeakers and hard disk drives, as well in hybrid cars and generators. Where low mass is important, they are vital: for example, in laptops, they provide finer control in the motors that spin the hard disk and the arm that

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Courtesy: Ames Laboratory

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Scarcity

Gschneider: “There is a serious lack of technically trained personnel to bring the entire rare earth industry ... up to full speed.”

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Rar e Earth E le m e nts Cover Story

value

writes and reads data to and from it, allowing much more information to be stored in the same area. In its Critical Materials Strategy, the US Department of Energy (DoE) estimates new uses of neodymium, in products like wind turbines and electric cars, could make up 40% of demand in an already overstretched market, which is why any shortages would be critical. Most of the rare earths vital to electronics are less well known: erbium is one example, a crucial ingredient in optical fibres. For long distance optical fibre transmission, amplification is vital and is achieved with the help of erbium. Embedded within short sections of the optical fibre, excitable ions of erbium are pushed into a high energy state by irradiating them with a laser. Light signals travelling down the fibre stimulate the erbium ions to release their stored energy as more light of precisely the correct wavelength, amplifying the signals. Tellurium is an element that could see a huge increase in demand because in 2009, solar cells made from thin films of cadmium telluride became the first to outdo silicon panels in terms of the cost of generating a Watt of electricity. Until now, there has been little interest in tellurium, but if it leads to significantly cheaper solar power, demand will rocket and that is why the DoE anticipates potential shortages by 2025. Hafnium is another rare earth proving itself vital to the semiconductor industry; hafnium oxide is a highly effective electrical insulator. It outperforms the standard transistor material, silicon dioxide, in reducing leakage current, while switching 20% faster. It has been a major factor in enabling the industry to move to ever smaller process nodes. Also central to semiconductors is tantalum, key to billions of capacitors used worldwide in products like smartphones and tablet computers. In its pure form, this metal forms one of two conducting plates on which charge is stored. As an oxide, it is an excellent insulator, preventing current leakage between the plates, and is also self healing, reforming to plug any current leakage. One of the most widely used rare earths is indium, which we all spend a lot of time looking at. The alloy indium tin oxide (ITO) provides the rare combination of both electrical conductivity and optical transparency, which makes it perfect for flat screen displays and tvs, where it forms the see through front electrode controlling each pixel. A layer of ITO on a smartphone’s screen gives it the touch sensitive conductivity to which we have been accustomed in the last few years. Mixed with other metals, indium becomes a light collector and can be used to create new kinds of solar cells, together with copper and selenium.

Courtesy: MIT

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Jaffe: “The magnetic properties of pure metals and relatively simple alloys have been thoroughly explored and there is nothing as good as rare earth magnets.”

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Rar e Earth E le m e nts Cover Story

According to the US Geological Survey, the Elk Creek Carbonatite in Nebraska is potentially the ‘largest global resource of niobium and rare earth elements’. Courtesy: Quantum Rare Earth Development

Another rare earth valuable for its magnetic properties is dysprosium. When mixed with terbium and iron, it creates the alloy Terfenol D, which changes shape in response to a magnetic field; a property known as magnetostriction. Dysprosium can also handle heat; while magnets made from a pure neodymium-iron-boron alloy lose magnetisation at more than 300°C, adding a small amount of dysprosium solves the problem. This make the element invaluable in magnets used in devices such as turbines and hard disk drives. Other rare earths include: technetium, used in medical imaging; lanthanum and cerium, the main components of a ‘mischmetal’ (an alloy of rare earth elements) used to create the negative electrode in nickel metal hydride batteries – and cerium also helps to polish disk drives and monitor screens; yttrium, important in microwave communication, and yttrium iron garnets act as resonators in frequency meters; and europium and terbium. The last have been used for decades to produce images in colour tvs, thanks to their phosphorescent properties – terbium for yellow-green and europium for blue and red. More recently, energy saving compact fluorescent light bulbs have used them to generate the same warm light as the incandescent tungsten bulbs they replaced. Is there a single reason why the rare earths have proved so valuable for such a range of technologies? The answer is no – it is more a result of each element’s particular physical characteristics, notably the electron configuration of the atoms, according to one of the world’s leading experts, Karl Gschneidner, a senior metallurgist at the DoE’s Ames Laboratory. “Some of the properties are quite similar; basically, their chemical properties. That is why they are difficult to separate from each other in their ores and that is why they are mixed together in the ores. But many of the physical properties vary quite a bit from one another, especially those which depend upon the 4f electron (a particular electron shell in the configuration of the atom), that is the magnetic, optical and electronic properties. Even some of the physical properties, which are not directly connected to the 4f electrons, vary considerably. For example the melting points vary from 798°C for cerium to 1663°C for lutetium.”

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What makes the rare earths so special is the way they can react with other elements to get results that neither could achieve alone, especially in the areas of magnets and phosphors, as Robert Jaffe, a Professor of Physics at MIT, explains. “The result is high field strength, high coercivity, light weight magnets, clearly valuable in tiny devices where magnetically stored information has to be moved around, like hard disk read/write operations. The magnetic properties of pure metals and relatively simple alloys have been thoroughly explored and there is nothing as good as rare earth magnets. Two paradigms for magnetic material are NeBFe (neodymium-boron-iron) and SmCo (samarium-cobalt), with the former most popular now. “In phosphors, europium, terbium and others absorb high frequency light and then re emit the light in regions of the spectrum that are very useful in manipulation of colour, hence their use in flat panel displays and compact fluorescent lights.” Another example is neodymium oxide, which can be added to crt glass to enhance picture brightness by absorbing yellow light waves. Neodymium has a strong absorption band centred at 580nm, which helps clarify the eye’s discrimination between reds and greens. Given how vital they are for the electronics industry and other technologies – by one estimate, £3trillion worth of industries depend on them – it is remarkable that the world has been so complacent about sourcing rare earths, allowing a single country to virtually monopolise the supply. But that is now changing. For example, the Mountain Pass mine in California is being reactivated by Molycorp Minerals in a $781million project, having been mothballed in 2002. Others include the Nolans and Mount Weld Projects in Australia, a site at Hoidas Lake in Canada and projects in Russia and Malaysia. In Elk Creek, Nebraska, Quantum Rare Earth Development is drilling to look for supplies and has called on President Obama to move aggressively to create a stockpile of rare earths. Another associated problem is the lack of people with rare earth expertise, as Gschneidner says. “There is a serious lack of technically trained personnel to bring the entire rare earth industry – from mining to OEMs – up to full speed in the next few years. Before the disruption of the US rare earth industry, about 25,000 people were employed in all aspects. Today, there are only about 1500.” Despite these moves, it could be years before supplies are enhanced significantly. For the longer term, there are prospects of better sources emerging. Just a couple of months ago, scientists from the University of Tokyo announced they had found the minerals in the floor of the Pacific Ocean in such high density that a single square kilometre of ocean floor could provide 20% of current annual world consumption. Two regions near Hawaii and Tahiti might contain as much as 100billion tonnes. The team was led to the sea floor because they reasoned that many rock samples on land containing metallic elements were originally laid down as ocean sediments. “It seems natural to find rare earth element rich mud on the sea floor,” they said. A final extraordinary fact about rare earths is that, despite their importance, we have hardly bothered to recycle them. In an age where metals like aluminium, copper, lead and tin have recycling rates of between 25% and 75%, it is estimated that only 1% of rare earths are recycled. If we do not correct that quickly, over the next few years at least, rare earths could live up to their name with a vengeance.

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Technology Watch Introduction

Capacity for change apacitors, like almost all other passive components, are generally treated with a little less respect than they deserve. They may not have the high profile of the microprocessor, for example, but nevertheless play a central role in electronic design. Capacitor manufacturers are faced with many challenges, but probably the hardest to address is the need to make those targeted at consumer products ever smaller: the 01005 case size – measuring 0.4 x 0.2mm in case you’re wondering – is an example. Dealing with the physical dimensions is one problem; developing the devices in a range of capacitances and voltage ratings is entirely another. Higher capacitance is achieved by having greater surface area on which to hold charge, but how do you get a bigger surface area when you are having to put that into a smaller volume? Many of the decisions involved in capacitor design are trade offs; if we do this, we can’t do that; so which is the most important? Even if you solve the problems from a technical perspective, manufacturers then have to address the commercial aspects. Shortages of vital materials, such as tantalum, can pull the rug from under you very quickly. The fact that companies can not only solve these problems, but also make the devices reliably and in huge volumes, is testament to their ingenuity. The sheer range of capacitor types is daunting; thousands and thousands of variants from hundreds of manufacturers, ranging from 01005 case sizes to oil drum like electrolytics. Each is a work of art, even though most are regarded simply as ‘jelly beans’. As we note in the article in this issue’s Technology Watch, it is possible to think of capacitor design – certainly at the 01005 scale – as a branch of nanotechnology. That puts the capacitor in a different light.

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Graham Pitcher, Editor, New Electronics

If you go to the Digi-Key website and search for capacitors, you’ll see a choice of more than 175,000 parts. That’s a huge number and each part suits a particular need. Digi-Key is pleased to partner with New Electronics to look at the prospects for one of the industry’s unsung heroes: the capacitor. Mark Larson, President, Digi-Key

As an extension of its commitment to providing top quality product, Digi-Key is pleased to partner with New Electronics to provide relevant, useful information to UK engineers.

www.newelectronics.co.uk

13 September 2011 21

Material swirl ew passive components exist in the sheer variety of forms that the capacitor has taken. Simple in principle, the design of the capacitor involves a number of tradeoffs that make it impossible to satisfy all possible uses with just a few types of product. It is possible to regard capacitor design as being the original nanotechnology because of the way in which it relies on achieving a chemically complex construction over very small dimensions – and that research is continuing as manufacturers try to squeeze more energy into a tiny space. Engineers have used an incredible variety of materials to realise new capacitor types, often relying on their detailed molecular structure to improve charge storage, only to discover that commodities prices have made their products uncompetitive. A simple – and very poor – capacitor consists of two parallel conductive plates, held a certain distance apart by a dielectric insulator with a relative permittivity of …r. The capacitance of the device is defined as the plate area divided by their distance apart, multiplied by the relative permittivity and the permittivity of free space, …0. To increase the capacitance of a device defined in this way means either increasing the area of its plates or the relative permittivity of the dielectric material or reducing the distance between the plates – or a combination of all three. Capacitor design is all about making the surface area of the plates as large as possible and then packing those plates into a very small volume. A typical construction is a metallic foil separated by a very thin dielectric material, such as a polymer film. The foil and dielectric sandwich is wound into a tight spool, to maximise the energy storage density. But

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Fig 1: Typical construction of a ceramic capacitor

Substrate

Barrier

External

Termination electrode

this approach is limited by the availability of very thin dielectric films with suitable breakdown characteristics. Texturing the foil is key to increasing surface area without increasing the volume of the capacitor at the same time. The energy such a device can store is defined as half of its capacitance multiplied by the applied voltage squared. Increasing energy storage, then, means increasing its capacitance, as discussed, or increasing the voltage applied. But there is a limit to how far you can drive the voltage; beyond a certain field strength, defined by the voltage applied and the thickness of the dielectric material, the dielectric will break down and start to conduct. Trade offs like these control a device’s practical ability to store energy, so some will offer very high voltage using film capacitors, whereas others will have high volumetric efficiency in terms of energy storage, but will collapse under a high applied voltage. King of the capacitor market today is the ceramic capacitor. In 2008, nine out of every ten capacitors shipped were

Internal electrode

The multilayer ceramic capacitor remains the most popular device, with a wide range of applications on pcbs

ceramic and most of those were based on the chip like design of the multilayer ceramic capacitor (MLCC) (see fig 1). However, because they have relatively low capacitances and are often scattered around PCBs for filtering and decoupling, they accounted for only 40% of the capacitor market’s dollar value. There are two main classes of dielectric used in ceramic capacitors. Generally based on simple oxides, Class I dielectrics offer poor volumetric efficiency, but offer comparatively stable performance over temperature. Class II materials generally offer much higher dielectric constants, but at the cost of less predictable performance with changes in temperature. For example, barium titanate (BaTiO3) has become one of the most commonly used dielectrics in Class II capacitors, thanks to its ferroelectricity. However, changes in temperature cause the crystal structure of BaTiO3 to alter, which causes dramatic shifts in the dielectric constant (see fig 2). Manufacturers typically use solid solutions of BaTiO3 with dopants based on

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Technology Watch Capacitors

Apparently humble, capacitors can be considered as one of the first nanotechnology products. Chris Edwards finds out more.

Fig 2: BaTiO3 exhibits strange dielectric behaviour with temperature change 14 000

Dielectric constant

12 000 10 000

Rhombohedral

Orthorhombic

Tetragonal

Cubic

8000 6000 4000 2000 0 -160

-120

-80

strontium, calcium, zirconium, tin and rare earths. These broaden the dielectric constant peaks of the core BaTiO3. Alternatives to BaTiO3 include ‘relaxor’ dielectrics, which gain their properties from a nanostructure of tiny polar regions surrounded by a non polar matrix. This results in permittivity values that are frequency dependent, which is how these materials get the name ‘relaxor’. The presence of lead in many candidate materials, however, limits the use of relaxors to specialist applications, such as capacitors for high temperature systems. One of the biggest changes in the construction of MLCCs has come not so much in the dielectric chemistry and nanostructure, but rather in the electrode materials. MLCCs are typically made by folding a flexible tape of electrode and dielectric into a sandwich that is then sintered at high temperature to remove any solvents and then forms a dense chip capacitor. The trouble with this co-firing process is that it risks the electrode metals reacting with the complex dielectric. Precious metals do not react

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-40

0 Temperature °C

40

80

nearly as readily as base metals, so were favoured in MLCCs for many years. However, the use of metals such as platinum and palladium in automotive catalyst converters brought capacitor makers into conflict with car makers for sources of these metals. Car makers had the benefit of being able to switch much more readily between metals when the price of one increased too far than capacitor manufacturers, who would be forced to swallow often sudden cost changes or risk becoming uncompetitive. By the end of the internet bubble at the end of the 1990s, the price of palladium had risen tenfold in less than ten years, before plummeting again. These dramatic price swings convinced MLCC makers to push harder on alternatives to precious metals, such as nickel. Doping with rare earths has helped to limit the reaction between the nickel and oxygen in the dielectric layers and has boosted overall device lifetime, particularly at high temperatures. The volumetric efficiency of MLCCs has gradually increased, with customers in

120

160

While barium titanate is one of the most widely used Class II dielectrics in ceramic capacitors, its properties need to be modified through the addition of dopants

response choosing to move to smaller case sizes. Whereas the 2012 case size dominated in the mid 1990s, manufacturers have shifted to the 1005, with smaller packages such as the 0603 and 0402 gaining in popularity. And the almost microscopic 01005 is beginning to see usage in volume. One factor limiting the size of MLCCs lies in the porosity of any ceramic, which keeps the breakdown voltage relatively low. So manufacturers are now looking at the use of glassy dielectrics to try to improve volumetric efficiency and to increase the breakdown voltage. The other main capacitor in general use is the electrolytic, split between the aluminium and tantalum families. The electrolytic technology dates back to the end of the 19th Century, when Charles Pollak received a patent for an aluminium electrolytic capacitor based on a borax electrolyte. Pollak discovered that a very high capacitance formed between a very thin aluminium oxide layer deposited on the electrode and an electrolyte solution. The downside was that the electrolyte would eat away at the electrode when power was removed. Borax turned out to work as an electrolyte without destroying the electrode. The reliability of electrolytics has improved dramatically over the years, but the components still need some care and attention. For example, the oxide layer can degrade if the capacitor is not used for long periods, although it is possible to rejuvenate the oxide with a sustained voltage. The chemistry of the electrolytic means the capacitor can only be used in one polarity. Reversing the polarity destroys the oxide layer – the resulting gas expelled at high temperature will often rupture the package.

13 September 2011 23

Reversing the polarity of an electrolytic capacitor destroys the oxide layer – the resulting gas expelled at high temperature will often rupture the package.

Aluminium electrolytic capacitor technology is now seen as mature, although some improvements are being made to their chemistry. Tantalum based devices, meanwhile, have seen more extensive changes in the past decade. These typically offer higher capacitance in a smaller space and tighter tolerances than their aluminium cousins, although they are not available with capacitances as high as the largest aluminium products. But tantalums are not without their problems; not least being the core metal’s scarcity. During the internet boom of the late 1990s, tantalum prices soared because of the capacitors’ use in computers and mobile phones. Capacitor makers attempted to secure supplies in the face of increasing demand and tied themselves into contracts that quickly became punitive after spot market prices tumbled in the wake of the 2001 bust. Tantalum prices have risen and fallen with other commodities since then, seeing a smaller but significant peak in 2009. Although similar problems have afflicted ceramics because of the use of precious metals in electrodes, many manufacturers have decided that the tantalum capacitor is too volatile in terms of price to be a good choice where alternatives exist. As a result, designers have shifted to using high capacity MLCCs, squeezing tantalums into a smaller niche where aluminium products cannot fit. Despite their better space efficiency, tantalums have traditionally suffered a big drawback compared with aluminium products: relatively high effective series resistance. This is due to the poor conductivity of the manganese oxide used in the cathode. A move towards polymer cathodes has helped reduce this

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A comparison of electrostatic, electrolytic and double layer capacitors. Double layer devices use a porous carbon based electrode material, whose structure provides a surface area of the order of 1000m²/g

Fig 3: A comparison of simple, electrolytic and double layer supercapacitors

A

Al2O3

+

–

+

–

V

V

E

E d

Electrostatic

resistance, although aluminium chemistries have joined this trend: to improve overall efficiency and to avoid the shortcircuit failure mode of electrolytics. Polymer cathode materials help with one other problem: the tantalum capacitor’s explosive nature. The manganese oxide that forms the cathode in a standard tantalum capacitor can release oxygen as it heats and that allows tantalum to burn – sometimes with catastrophic results. Conductive polymers do not release oxygen as readily as manganese oxide, although they will shortcircuit, and sometimes more readily than the metal oxide versions. This is because there is a limited self healing mechanism with manganese oxide that protects against local shortcircuits, at least up to a point. An alternative that has appeared in recent years is the niobium capacitor, chosen because niobium has a higher

d Electrolytic

ignition temperature than tantalum and because it is up to 100 times more abundant than tantalum, which should keep its price under closer control. Niobium has been used in ceramic capacitors, but problems with the way in which its oxide forms delayed the introduction of solid electrolytic designs. Chemical treatments have made it possible to build stable devices. Chemistry has taken the capacitor into the realm dominated by batteries, using a combination of reversible chemical changes and electrostatics to boost energy storage. Supercapacitors, also known as ultracapacitors or electrochemical double layer capacitors, have a double layer construction of two non reactive porous carbon electrodes immersed in an organic electrolyte (see fig 3). When a voltage is applied to the plates, the potential on the positively charged plate attracts the negatively

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Technology Watch Capacitors

Chemistry has taken the capacitor into the realm dominated by batteries, using a combination of reversible chemical changes and electrostatics to boost energy storage.

+ + + – – +

– – + + +

+ + – + + – –

–

–

+ – + –

–

–

– +

–

–

+

– +

+ – –

–

+ – – +

– – –– + – + +

Electrode

–

+ – – +

Separator Activated carbon

Double layer

charged ions, and vice versa. This creates two separate layers of capacitive storage, one at each plate. These high capacity devices benefit from massive plate areas, thanks to the use of a porous carbon based electrode material whose structure provides a surface area of the order of 1000m²/g. Supercapacitors also benefit from the distance between the plate and the stored charge – the charge separation distance – being less than 1nm, controlled by the size of the ions in the electrolyte. The combination of large surface area and very small charge separation gives the supercapacitor its increased capacitance relative to conventional parts. Although supercapacitors are electrochemical devices, relying on the polarisation of an electrolyte, there’s no chemical reaction involved in the energy storage mechanism. This means it is highly reversible, enabling

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supercapacitors to be charged and discharged hundreds of thousands of times, as well as quickly. Supercapacitors also have low equivalent series resistances, which allows them to give up their energy very quickly to create very large currents. Supercapacitors are also less likely to be affected by temperature than chemical batteries, since they’re not reliant on a chemical reaction that could be slowed by low temperatures. The parts have been used in applications that need to be charged in seconds and then discharged over minutes, for example in power tools and toys. They are also used in uninterruptible power systems, where the ultracapacitor provides the power for short outages, or as a bridge to a generator set or other continuous back-up power supply. This combination of characteristics makes supercapacitors an attractive supplement to, or perhaps future replacement for, chemical batteries. Supercapacitors can be used to take over the short term heavy current delivery necessary to drive a starter motor to turn over a car engine or to provide fast load smoothing in applications with very irregular current demands. Supercapacitors are getting a lot of attention in vehicle applications. An MIT team points out that the devices have a greater power rating than a conventional lead-acid battery, superior charging and discharging characteristics, and can be fully discharged without being damaged. There is a downside: the discharge profile of a supercapacitor has a significant drawback when it comes to safety. Vehicle makers are concerned about what could happen if an electric vehicle breaks down and the driver decides to open up the bonnet and have a

poke around to see what is wrong. A spanner in the wrong place could lead to a very sudden and fatal discharge through the driver – something that is less likely to happen with a conventional battery pack. So, if they are used, supercapacitors will need much more protection to prevent accidental discharge. Self discharge is also a problem. An array of supercapacitors could not be used to hold the bulk of an electric vehicle’s energy because it would need to be topped up regularly when parked for long periods. At the other end of the power scale, developers are investigating using supercapacitors to provide peak currents in handheld devices, such as in mobile phones and wireless modems during transmission or polling. Supercapacitors are likely to be a good match for the kind of ‘bursty’ power demands of such intermittent high current demands. Their ability to reduce the peak power demands on the chemical battery are also likely to extend its lifetime, a critical factor in consumer electronics devices, although there is a tradeoff between the energy lost through self discharge and the problems caused by continual battery charging. Improvements in materials science and nanotechnology are not just likely to lead to better forms of individual capacitor families, but also point to a possible crossover between different technologies. For example, improvements in polymer and glass composite design could lead to capacitors that have the high volume production advantages of a ceramic construction, but with the properties associated with an electrolytic. Despite their humble appearance, there is still plenty of evolution to come in the world of the capacitor.

13 September 2011 25

Efficiency drive he question of efficiency is never far away when looking at power supply design, even though it might be trumped by cost when the final choice is made. For years, however, efficiency has been about a single number: the peak efficiency at a favourable load point. The trend now is to look at power supply efficiency from a more holistic point of view. This is particularly true of the server environment where a focus on the idea of the green data centre – or at least one that is nowhere near as heavy on energy consumption – has taken hold. Air conditioning is one of the reasons why data centre energy consumption is so high. One option is to use less of it and run the equipment at a higher temperature. Naturally, this will have an effect on the reliability of the components, not least the temperature sensitive components in the power supply, such as the large electrolytic capacitors. This may force manufacturers to look at components that offer longer lifetimes in hot conditions.

T

Point of load conversion A further trend is the gradual, albeit slow, adoption of 380V distribution around the racks, converting down to 48V only at the blade level, from where the PCB level voltages are distributed. Even there, the PCB voltages may go into reverse in response to the problems of feeding high current at low voltages to large processors and SoCs. These devices are increasingly likely to sport on chip or within package voltage regulators so that the number of power pins that a device needs can be reduced. Then there is the question of what peak efficiency means in the context of a

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complete system. This level of performance is often only seen when the load is a very high proportion of the maximum output. Because the power supply may have been specified with a certain level of headroom and because the computer itself may only be expected to run at high load for short periods of time, the actual delivered efficiency can be a long way short of the peak. Attention has now shifted to real world use and how well power supplies stand up to loads of 50% or less. This is having a knock on effect on the architecture of the power supplies themselves. Today, in servers and similar

systems, power factor corrected (PFC) rectifiers have pretty much replaced their uncorrected predecessors. A simple rectifier circuit has very high peak current consumption and imposes high harmonic distortion on the input, bringing the power factor down as low as 0.5. The PFC converter introduces much faster switching, usually under pulse width modulation (PWM) control, to reduce the peak current level. Typically, the PFC converter takes the form of a full-bridge rectifier, followed by a boost converter, which contains the PWMcontrolled switch itself, an inductor and an output diode. There are two ways to control the switching. One is continuous conduction mode (CCM), in which the current in the inductor need not be zero when the switch is turned on. This causes the diode to experience reverse recovery. Switching this MOSFET on and off regulates the current, which is smoothed using a large capacitor. Under the alternative scheme, called boundary conduction mode (BCM), the inductor current is allowed to fall to zero before the MOSFET is turned on. This results in soft switching and so reverse recovery does not occur in the diode. However, the technique tends to result in higher conduction losses through the MOSFET and diode because the peak inductor current tends to be higher than with CCM switching. BCM also relies on variable-frequency switching so that the inductor current can be allowed to fall to zero. Typically, BCM wins in designs of up to around 300W, but the distinction is not clear cut. The arrival of silicon carbide diodes has made it possible to improve the efficiency of CCM because

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Technology Watch Power Supply Efficiency

Chris Edwards finds a growing focus on holistic power supply design.

Fig 1: Bridged and bridgeless power factor correction circuits Boost converter section

VAC

Bridged

these diodes have very much lower reverse recovery losses than conventional materials, although they are more expensive. Some silicon diodes can also cut reverse-recovery losses, but sometimes at the cost of higher conduction losses. The diodes in the full-bridge rectifier itself can experience large losses, particularly as they may be slowrecovery parts. This is where the ‘bridgeless’ PFC topology comes in. MOSFET switches are used in place of two of the diodes and allow a reworking of the bridge-boost converter topology. With the switches replacing half of the bridge, it is possible to remove the boost diode that follows the inductor in a traditional circuit. The bridge diodes themselves perform roughly the same job. As this topology looks a little like two boost converters glued together, sharing a common inductor, the bridge seems to have disappeared, providing the source of the term ‘bridgeless’. Higher overall

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efficiency results from a reduction in the number of semiconductor devices in the inductor-charging current path from three to two. However, the bridgeless-PFC topology is more complex outside the power path as the switching modules need to be able to perform current sensing and input voltage sensing. This, in turn, is driving the development of digital, rather than analogue, control. There is a further complication, however: some of the power losses that would normally be handled by diodes in a bridge rectifier now have to be transferred to the power MOSFETs, leading to higher junction temperatures and an increase in transistor size and cost. Noise is also a problem with the conventional bridgeless-PFC topology as there is now no low-frequency path to the output. This leads to an increase in common-mode electromagnetic interference (EMI) from the charging and discharging of parasitic capacitances.

Bridgeless

By replacing diodes with MOSFET switches, the bridgless topology offers higher overall efficiency, due to the reduction in the number of semiconductor devices in the inductorcharging current path

The result is that practical bridgelessPFC converters tend to be more complex than the basic theoretical topology. In response to the idea of approaching power design within a large system as a holistic problem, one PFC technology that is becoming more common is the boostfollower PFC. It can help increase overall efficiency within a larger system just as long as downstream converters are designed to deal with it. In this topology, the output voltage is allowed to change with the input voltage. This method increases the overall efficiency of the PFC converter, but it demands that any downstream DC/DC converters are able to operate over a wider input voltage range – which might be 200V to 400V. This, in turn, restricts the topologies that can be used. Within the DC/DC converters themselves, the topologies have moved to more complex forms of switched conversion, such as quasi-resonant operation or multiphase conversion.

13 September 2011 27

Technology Watch Power Supply Efficiency

While the more phases there are means the more control you have over the efficiency curve, each phase costs money in terms of additional control circuitry and power transistors

Fig 2: A multiphase converter L

iL1

iL

iout iC

Vg + –

+

Phase I Vout

C

Phase I

steadily pushing that number up, although the increase in output capacitance needed for a smaller number of phases can negate some of the cost saving. As efficiency at lower loads becomes more important, it can make sense to soak up the cost of the extra active components. Sometimes, even the current from one phase is too much. This is where pulse-skipping or burst mode comes in. In burst mode, the switching circuit is only activated when the output voltage starts to move out of regulation, effectively skipping some of the switching cycles that would have happened if it were left to run as normal.

Phase II L

iL2

– Phase III

Phase II

Phase IV L

iL3

Phase III

iL = iL1 = iL2 = iL3 = iL4 L

iL4

Phase IV

These switchers tend to operate at high frequencies, so switching losses are the ones that need to be tamed. As a result, the quasi-resonant approach takes advantage of soft switching to reduce recovery losses. The quasi-resonant converter gets its name from having the switching frequency determined not by the natural oscillations of an inductorbased circuit but by a digital PWM controller. On their own, quasi-resonant and similar topologies do not fare so well with widely varying loads, such as a server blade that can suddenly come out of idle, process heavily for a few minutes and then go back into a quiescent state. This is where the multiphase converter comes in: it splits the task of converting from one voltage to another among several parallel circuits.

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A multiphase converter (see fig 2) might have four or five phases, all of which are active at full load. As the processor slows, the load reduces and the power supply – if it is intelligent enough – can start to drop phases. This reduces the impact of switching losses, as they will start to dominate at lower loads, and better matches power supply output to the load. When dealing with multiphase converters, it is not entirely straightforward to work out many phases are needed. While the more phases there are means the more control you have over the efficiency curve, each phase costs money in terms of additional control circuitry and power transistors. In general, the rule of thumb is that each phase should deliver around 25A. Improvements in technology are

When specifying a multiphase converter, designers should work to the general rule that each phase should deliver around 25A

What happens next? When the load is powered down completely, there is the question of what happens to the front-end power supply. If left to run, it will tick over, but waste most of the energy that it delivers. This situation is particularly problematic for battery chargers, which will run until the cells are fully charged and then switch off. Through improvements in efficiency, a quiescent charger might draw 500mW. This can be brought down further, to less than 100mW, by moving to active control over the actual power supply circuit – using a digital controller on a separate circuit to disable power to the main switching circuit when there is no load detected. From simply pursuing peak efficiency, what happens on the load side is now the dominant factor in power supply design. That is likely to lead to greater levels of interaction between the equipment and the power supply architecture as designers try to eke greater performance out of their circuits.

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Company Announcement A lte ra

Altera Transceiver Toolkit Craig Davis Product Marketing Manager, Altera Europe, describes a comprehensive debug tool for FPGA based transceiver links PGAs are currently used extensively in data communication systems, the benefits of reprogrammability, fast development cycles and abundant features such as transceivers and DSP blocks allow any communication protocol to be implemented, some are already included as complete or partial hard-IP blocks (such as PCIe or 10G Ethernet). FPGA designers face several issues when debugging these communication interfaces, being able to verify the equalisation settings with data flowing through the links and checking that the bit error rate (BER) is within the limits of the protocol specification. You can verify the system in three ways: you can just run it, test it with an oscilloscope or bit error rate tester, alternatively you can use a test suite that thoroughly test the link integrity. Altera’s Transceiver Toolkit is one such tool. The Transceiver Toolkit is a part of the Quartus II design software and performs testing of transceiver links in hardware. It is a series of reference designs that will thoroughly test the transceiver and relay the results to a monitoring program: the Altera System Console. The design blocks consist of pseudo-random binary sequence (PRBS) generators and checkers connected to low-latency transceiver PHY blocks all coupled to a control block that communicates to the toolkit software through a JTAG interface. With these blocks you can generate test patterns and control all aspects of the transceiver setup. There are several use models for the toolkit; it can be used to quickly test the transceivers to see if you have link continuity, it can optimise

F

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Figure 1: A screenshot of Altera’s high-speed communication link analysis toolkit. Figure 2: The EyeQ link analysis circuitry in an Altera Stratix V FPGA transceiver

the analogue settings (drive strength, equalisation settings) of your link by performing a PMA settings sweep, coupled with the EyeQ circuitry in the transceivers it can generate a bit error rate contour eye diagram. The EyeQ circuitry can be run constantly or periodically within the FPGA while live data traffic is being communicated to verify that the receiver is sampling in the most optimum phase. The EyeQ circuitry is shown in Figure 2. The most common usage is either testing of the analogue settings computed from link simulation or by brute force methods obtaining the optimum settings for the link (automatically testing combinations of settings). Then by examining the BER contour the amount of margin for a given BER can be obtained. Transceiver link design and the associated debugging can take a significant proportion of time and effort of any design project. The careful design of transceiver links for low BER from the outset can drastically reduce the amount of time spent in the design and debug phase. When you are in the debug and verification phase of the design the use of an in-circuit validation tool such as the Transceiver Toolkit can help optimise transceiver links and validate that the system operates with a low bit error rate.

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Defe n c e Sector Focus

Breaking performance barriers High performance computing comes to the military embedded market. By William Pilaud. hen military customers discuss new embedded radar, communications intelligence (comint), signal intelligence (sigint) and situational awareness systems, they are demanding the levels of performance provided by the High Performance Computing (HPC) systems used in demanding commercial applications. To meet the real time needs of these applications, HPC technology is migrating to ruggedised, compact packaging that meets the size, weight, power and cost (SWaP-C) constraints of deployed military platforms. The result is High Performance Embedded Computing (HPEC) systems that can be built using open standard OpenVPX modules and deployed in standard military system chassis. Embedded COTS vendors are now aggregating and packaging the heterogeneous HPEC environment – comprising single board computers (sbcs), fpgas and general purpose gpus (gpgpus) – to meet the needs of these advanced applications. The benefits of HPC type technologies, developed originally for enterprise back office environments, are being brought to

W

The RME9CC, a 12 slot 3U OpenVPX chassis, supports the development of military embedded systems and offers switch fabric support for up to 6.25Gbaud

the military environment, thanks to COTS packaging and integration techniques. In essence, it is now possible to take supercomputer levels of processing performance – that, only recently, required rooms full of equipment – and migrate that to rugged open standard 3U and 6U OpenVPX boards integrated into a 19in deployable rack.

The dual Nvidia gpus on the VPX6-490 each feature 240 CUDA cores

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Application example HPEC allows the compute technology and performance levels typically associated with HPC to be applied to the most demanding processing problems

using open architecture rugged hardware. A key element of these systems is high performance interfaces, such as Serial RapidIO (sRIO) and PCI Express. One recent application that serves as an example of how HPEC brings HPC technology into traditional embedded defence and aerospace applications space is a situational awareness system that combines clusters of gpgpus, Intel processor based sbcs, Intel processor based dsp modules and leading edge commercial fpgas to deliver real time visual sensor information into helmet displays. In this HPEC system, data from the platform’s external visual sensors (which may comprise a wide number of different sensor types) is aggregated and, depending on which direction an individual user’s vision is oriented, the system can deliver the appropriate visual data to that user’s helmet display with smooth, realistic imagery. This challenging application requires several teraflops of processing power and many gigabytes per second of bandwidth. This represents levels of performance that were essentially unachievable in a SWaP-C constrained platform as recently as two years ago. GPGPU technology, now with 240 cores in a single processor, has become increasingly dense and delivers significantly improved power/Watt, making these processors – originally designed for graphics and game applications – more attractive for rugged embedded situational awareness applications, such as this vision system. This HPEC system uses a combination of Intel and Freescale general purpose processors, as well as fpgas with sRIO interconnects between the different modules. sRIO is an ideal

13 September 2011 31

Sector Focus Defe n c e

fabric for an HPEC architecture because, while it looks very much like high speed Ethernet or Infiniband connections to the general purpose processors, it provides a low latency, high bandwidth interconnect that fpgas can use to stream data directly into the processors. In this system, the gpgpus provide data processing and data stitching between the sensors, while sRIO enables the sensor data to be sent directly into each gpgpu to handle the visualisation streams in parallel and perform processing functions such as pixel correlation. The HPEC system’s sbcs manage the sRIO interconnects, the fpgas handle the application’s demanding algorithms and the gpgpus handle the sensor data analysis. Using today’s embedded boards, such a system can be deployed in multiple compact rugged racks and might comprise up to 18 6U OpenVPX boards. More than half of these would be gpgpu processor boards, delivering in excess of 7Tflops of compute power. OpenVPX enables the gpgpus to be connected in a point to point fashion and SRIO, which provides the OpenVPX data plane bus fabric, handles interconnects to all the subsystems. Advanced second generation Intel Core i7 based OpenVPX dsp boards, such as CurtissWright’s CHAMP AV8, are a good match for gpgpu processors, which are typically Intel based. IDT’s PCI Express to sRIO bridge chip enables these Intel based boards to communicate using sRIO. Common building blocks Radar, comint, sigint and situational awareness systems access the same key building blocks and can appear quite similar at the component level. The base HPEC platforms developed for applications such as situational awareness are likely to be adapted to address many other types of defence and aerospace SWaP-Cconstrained opportunities because they can deliver a large amount of computing power in a

The Core-i7 based CHAMP-AV8 is a 6U OpenVPX multiprocessing dsp engine

very small space. As the types of sensors used on military platforms become more generic, an HPEC platform can serve as the central processor which, when coupled with the appropriate software, can be used to satisfy many different mission requirements. To bring HPEC to the military market CurtissWright has developed individual HPEC components so that system integrators can scale their HPEC system to any level the application requires. Today, system builders can access 5GHz (about 500Mbyte/s) per serdes connection, with 16x5 serdes connections on one module. Curtiss-Wright expects to see a migration to 10GHz serdes in the near future. As fpgas continue to get faster – they are expected to exceed 10GHz serdes – the market will start to look at faster transmission approaches, such as fibre optics. As these processors feature more cores, the

Continuum HPEC certification To help support the use of HPEC systems in demanding military applications, Curtiss-Wright has established the Continuum HPEC Certification process. This process of testing and ongoing product management not only ensures the interoperability of each hardware module in an HPEC system, but also that modules are architected with feature sets aimed specifically at operating within HPEC systems. Under the scheme, key enabling software components are supported, board support packages releases are coordinated and regression tested at least twice per year. All modules are validated using a HPEC test suite to ensure functionality in large node systems with demanding data flows.

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ability to cool the components becomes ever more challenging. For rugged deployed HPEC systems, OpenVPX boards cooled with air flow through technology will make it possible to bring these higher performance technologies into space constrained applications. Embedded radar/comint/sigint/situational awareness HPEC systems are designed to handle large amounts of streaming digital, optical or analogue data. To handle this data, HPEC systems use fpga technologies as high speed sensor inputs. FPGAs provide high speed interfaces, not only to the backplane, but also to standard FMC mezzanine card (VITA 57) interfaces. This rich set of high speed I/O integrates into a sRIO dataplane. sRIO provides an ideal sensor interface into scalable large HPC clusters. The sRIO dataplane interface can reside on the backplane or it can be wired between boxes, so customers can scale the system to whatever size necessary for their application. This approach enables customers to select the number of sRIO enabled COTS OpenVPX processing elements needed to support the appropriate amount of sensor inputs for their application, rather than having to build all system components from scratch. Author profile: William Pilaud is Continuum HPEC systems architect with Curtiss-Wright Embedded Computing. www.cwembedded.com

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T R US TED SOFTWA RE F OR D EFE N CE For nearly 30 years the world’s leading defence companies have trusted Green Hills Software’s secure and reliable high performance software for mission-critical and safety-critical applications. From the Joint Tactical Radio System, through naval anti-surface missiles, to the F-35 Lightning II and Eurofighter Typhoon, Green Hills Software has been delivering proven and secure underpinning technology. To find out how the world’s most secure and reliable operating system and software can take the risk out of your defence project, visit www.ghs.com/s4d

Copyright © 2011 Green Hills Software. Green Hills Software and the Green Hills logo are registered trademarks of Green Hills Software. All other product names are trademarks of their respective holders. U.S. Navy photo by Mass Communication Specialist 2nd Class James R. Evans/Released.

Brave new world As hardware becomes more complex and software dominates design teams, the eda sector is entering into a new world. By Graham Pitcher. here is a school of thought that believes hardware/software codesign is tomorrow’s technology – and always will be. But is that really the case? The technique has been around since the mid 1990s, when the first attempts were made to enable software design teams to start work before silicon came back from the fab. Two factors resulted in that initial work falling by the wayside: time to market was nowhere near as important as it is today; and the ratio of software to hardware in a project was small. Today, things have changed significantly. Time to market – and, more accurately – time to volume is critical and software is the dominant part of an SoC design, with software engineers often representing 70% of the design team. Yet tools to deal with the changing face of design have yet to appear. And it appears that some parts of the electronics world are beginning to get impatient.

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At this year’s Design Automation Conference, executives from Freescale and Intel made calls for the eda world to develop the tools needed to help them address future challenges. Michal Siwinski, Cadence’s senior director of product management for system realisation, said: “Freescale wants a parallel path between hardware and software development, while Intel wants a higher level of intent. We believe in both approaches and are breaking some technology that allows for codesign. In general terms, we’re seeing a healthy interest in the number of discussions and decisions about technology that allows software development to start earlier. These discussions are not only about tools for new programs, but also for use in existing products, where modifications need to be made and software adjusted.”

Siwinski: “Hardware/ software codevelopment systems will be the first step, but it won’t stop there.” Jim Kenney, director of marketing for Mentor Graphics’ emulation division, has significant experience of this area. He noted the launch in 1996 of Seamless, a product intended to allow users to address hardware/software integration issues early in the design cycle. “It allowed

Fig 1: Cadence’s system and software realisation flow Concept

SoC development

Architectural level development (pre RTL)

Prototype level development (post RTL) Product

System development suite Virtual system platform

Architectural intent

Incisive verification platform

Verification computing platform

Rapid prototyping platform

Verification IP C to silicon compiler Path to silicon

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Research & Development EDA

people to move things from hardware to software to see the effect. But nobody wanted it; they didn’t appear to want tools that helped them to experiment.” Kenney believes this was more a people related issue than a technology one. “Some things were obviously hardware, some obviously software. An architect would sit down and make a decision about the rest. Often, the decisions had already been made.” Siwinski believes a lot of technologies are often ahead of their time. “Virtual prototyping was a great technology, but the market wasn’t ready. Today, software is driving the market, so having devices available is important. Software can represent 75% of a design team, something that wasn’t the case 10 years ago. But eda vendors have to decide whether to offer a point tool or something engineers will use as part of their RTL to GDS design flow.” In Kenney’s opinion, hardware/software codesign is all about how to take advantage of multiple processor cores. “But tools aren’t keeping up with those needs; hardware designers can put more cores on silicon than software developers can take full advantage of.” Lurking behind the call for hardware/ software codesign tools is the cost of a respin: not only the physical cost of getting new samples manufactured, but also the lost market opportunities. “When a chip comes back from the fab,” Kenney said, “the first thing the customer

Kenney: “The first thing the customer wants to do is to run software on the hardware.” wants to do is to run software on the hardware. But, just as important, they want a complete working environment. They want to boot the operating system and, in the case of a graphics chip, want to see it draw something. “If they have been able to run verification and diagnostics against a hardware representation, they will know it’s a silicon problem if the chip doesn’t work.” Siwinski believes a potential solution may come from providing a higher level of abstraction. “Certain elements need to be at a lower level,” he claimed, “but even if you choose the architecture, you can tweak at that lower level. If you can shift the balance of the work to a higher level, say with Transaction Level Modelling, there will be a similar level of intent for modelling software and developing hardware. In this way, there will be effective design of new

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products and parameterisation of derivatives.” In Siwinski’s model, design of a chip starts with the creation of a specification. “It tells you what the product should do, the graphics expectations, power consumption and so on. As the design proceeds, more hardware/software partition decisions can be made. Once there is a good idea about what the chip looks like, the first sets of models can be developed and work on software can begin in parallel.” He also believes there needs to be better understanding between the software and hardware teams. “We’re seeing some of this happening and it’s not because engineering teams have worked out how to do it; it’s because management has decided that it can’t wait for an engineering led solution.” Kenney also sees a challenge in emulation. “Many more software engineers want to use emulation. The problem is that emulation runs at a few MHz; software engineers want to run at GHz rates. Our challenge is to get software developers to run on something much slower than they would like; we have to drag them over and show them the benefits. “Software people want a target to run on and to be able to hit ‘run’. We’re working to make emulators look more like target hardware.” Concluding, Siwinksi said he believes the fact that software is the critical factor will change automation for the better. “Hardware/software codevelopment systems will be the first step, but it won’t stop there.” www.cadence.com www.mentor.com

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GPUs set to enter the General purpose graphic processing units are set to play a greater role in embedded systems applications. By Aurelius Wosylus.

Wosylus: “GPUs are sometimes better able to handle parallel and data intensive tasks.” ntil recently, demand for more processor performance has been met by faster clocking, more bit width and ever smaller fabrication nodes. The introduction of multicore x86 devices has also helped to boost performance while keeping power consumption at a reasonable level. Yet even multicore processors are not always suitable for use in applications where you want to process large quantities of data as quickly as possible. In imaging diagnostics – such as MRI and CT, for example – it may take some time for multicore based solutions to produce final images, depending on the volume of data involved and the processing complexity.This is contrary to the needs of medical professionals, for example, who want image data to be processed as quickly as possible and displayed at high resolution. Alongside diagnostics, simulation is one of the most ambitious medical uses for cpus. Virtual microscopy, used in pharmaceutical research, is one example. Here, complex algorithms are used to simulate molecules and the way in which they react with one another. These applications share high performance demands; high enough that even the latest

U

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multicore devices cannot meet them. While it is possible to combine a number of multicore processors in a high performance cluster, the cost of purchasing and operating that kind of supercomputer, plus its infrastructure, is huge. An alternative approach can be found in high performance general purpose graphics processing unit (gpgpu) technology and tools, allowing the massive parallel computing power of modern graphics cards to be harnessed by embedded systems developers. GPU technology is developing rapidly, driven in particular by the demands of the consumer market. The ability of gpus to handle more frames per second at higher resolution and to provide uniform programming interfaces has created interest in using this technology in data processing applications. At the data level, there is not much difference between computing and displaying virtual worlds for games and the visualisation of raw data from a variety of sources, such as an ultrasound or coronary examination.

But GPUs are sometimes better able to handle parallel and data intensive tasks, for instance. Being restricted to specific problems enables them to be designed so that most of their transistors are devoted to computing operations and not to control and caching, as is the case with cpus. Computer scientists have led the way in using the huge parallel computing power of modern graphics cards. However, such a degree of parallelism made the algorithms extremely complex, restricting its appeal to idealists and specialists. With the introduction of development environments, such as AMD’s Accelerated Parallel Processing software development kit, and programming environments like OpenCL as an accompaniment to OpenGL, developers can now access the performance of modern gpus. Diagnostic speed can be multiplied simply by

PCI Express compatibility With a gpu clock of 850MHz and 1Gbyte of 1200MHz GDDR5 ram, the Radeon HD 5770 is a PCI Express capable card which uses AMD Stream technology to accelerate Open GL 3.2 and DirectX 11 applications. It also supports OpenCL 1.0 and DirectCompute 11. For high end 3d rendering applications – in medical imaging and simulation, for example – up to four graphics cards can be coupled using AMD’s CrossFireX technology. Two displays can be driven independently on the two dual link DVI-i interfaces with a resolution of up to 2560 x 1600 pixels. AMD’s Eyefinity multidisplay technology allows simultaneous operation of three monitors with different resolutions, frame rates, colour models and video overlays, as well as allowing several monitors to be combined to create one large display.

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E m b e d d e d Des i g n Micros

mainstream using the parallel computing power of modern gpus. Combined with high resolution and loss free imaging, this performance can produce incredible visualisation results. GPGPU enabled high performance systems also have cost benefits; and not just because it is less expensive to set up powerful graphics units as coprocessors on a standard embedded platform. Until recently, graphics card technology had one downside: short product life. The problem facing embedded systems developers was the lack of high end embedded graphics with long term availability. AMD has overcome this with the introduction of the ATI Radeon HD 5770 graphics card and the Radeon E6760 embedded discrete gpu (see boxes). This will help to provide medical apparatus OEMs with the design security they need for their graphics hardware. In addition, OEMs can benefit from integration of the gpu: a PCI Express capable x16 graphics card (PEG) can be used in a variety of embedded platforms, from a standard server board to a high end PICMG 1.3 backplane configuration. The Radeon E6760 gpu is also available in the MXM form factor. Graphics intensive applications are not the only ones that might benefit from high

GPU features 480 processing elements AMD’s Radeon E6760 gpu has been developed for use in embedded applications requiring compute intensive gpgpu functionality. With 480 processing elements, the E6760 gpu has a peak single precision floating point performance of 576Gflops, suiting it to use in such applications as ultrasound, radar and video imaging. The E6760 gpgpu is enabled by the OpenCL programming language and by AMD’s Stream Software Development Kit. The E6760 gpu, which supports up to six independent displays, HDMI 1.4 stereoscopic video and DisplayPort 1.2, can be paired with the forthcoming AMD A-Series accelerated processing unit to provide additional graphics capability and parallel computing power.

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Unlike PEG cards, MMX modules mount parallel to the carrier board, so the height of the embedded design is relatively unaffected. MXM modules build on the same advantages that have led to the success of computer on modules: a standardised footprint, a standard pinout and assembly concept and suitability as add on components.

processing capability; the graphics unit’s stream processors can take a huge workload off the multicore cpus when handling different data streams. Combining these processor units in shader units enables vector processing in addition to scalar operations. This potential can be accessed through standard programming platforms and APIs, such as OpenCL or

DirectCompute, simplifying and speeding application development. In terms of cost of ownership, gpgpu solutions are designed to be cost efficient because systems enhanced by modular gpus do not require multicore processors distributed over a number of server boards in order to produce measurable savings. Exchanging a gpu is also less complicated than replacing an entire board. And a gpu can be replaced in the future by a compatible and more powerful model without altering the system configuration significantly. There are many reasons for using high end graphics hardware in medical embedded systems and the long term availability of solutions does away with the short term availability obstacle. The belief is that gpgpu technology will increasingly become mainstream, cutting the time needed to develop new applications. To secure the advantages in the offing, it is well worth starting to think about implementing the technology. Author profile: Aurelius Wosylus is regional sales manager Europe with AMD’s embedded business unit. www.amd.com

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Co m m u n i cati o n Des i g n RF & Microwave

Cutting cables With demand for wireless links growing, what options are available? By Graham Pitcher. ables are, in almost every application, yesterday’s technology; if it isn’t wireless, it’s almost not worth considering. If you’ve decided that cables should go, what is the best solution for your product? There’s a range of options available to design engineers, but one thing is certain: one size doesn’t fit all. Designers have two broad choices – to go with ISM based solutions or to take the GSM route. And if you are thinking about ISM, there is a further split between point to point and mesh networks. John Sharples, managing director of Low Power Radio Solutions (LPRS), said demand for wireless connectivity is booming. “We have passed the tipping point. Everyone now expects everything to be wireless; consumers don’t want to plug things in and the same goes for the equipment market.” One of the main drivers in this market is cost, but Sharples contends that other factors, such as device quality and reliability are more important. He also believes the availability of low cost wireless connectivity is leading to overcomplicated designs. “We’ve got to the point where designers are including functionality without considering whether there’s a market for the product. We are always telling engineers

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Sharples: “We have passed the tipping point. Everyone now expects everything to be wireless.”

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to think carefully about their designs and to not design in unwanted functionality.” Looking to broaden its wireless portfolio, LPRS has recently signed a deal with Czech company Microrisc to distribute the IQRF product range in the UK. This move complements LPRS’ easyRadio line. The IQRF transceiver The easyRadio Advanced range of transmitters and transceivers is one of the module is a small board latest additions to LPRS’ industrial communication portfolio said to feature all the circuitry needed to support rf communication. According to Sharples, LPRS has been aware Operating in either the 868 or 916MHz ISM of Microrisc’s development of the IQRF portfolio bands, the board includes a PIC microcontroller for a couple of years. “Our first question was to and operating system with 80 basic ask whether we could do it ourselves. We could, instructions. Low power consumption has been but we didn’t want to reinvent the wheel. Over an important design parameter and Microrisc the last two years, the IQRF product range has claims the device will draw no more than 1mA developed substantially and we decided at the when running, 24mA when transmitting and beginning of 2011 that it had matured to the 13mA when receiving, with many parameters point where we could take it to market. We were software selectable. With a maximum bit rate of confident that it was the right product for us to 115kbit/s, the device can transmit over address markets we couldn’t before.” Sectors distances of up to 700m using an rf output where Sharples has high expectations include power of 3.5mW. A range of development tools is smart metering, smart grids and street lighting. also available. “IQRF is the right product at the right time,” Sharples noted: “The IQRF range supports Sharples enthused. “It’s not ZigBee, although it mesh networking and is more competitive with can work with it. It’s a great product for someone ZigBee.” And it is the contrast with ZigBee which who thinks they need ZigBee, but what they Sharples is keen to highlight. “When we get actually need is a mesh networking device.” asked for a networking product, the customer often asks whether we have ZigBee products. GSM for M2M While ZigBee has a lot of good points, it’s not What if the ISM band doesn’t meet your needs? always the right answer; you have to get ‘under The other option is to take the GSM route, an the skin’ of the application in order to approach advocated by cellular M2M specialist understand the requirements. But neither is the Cinterion. IQRF range right for everything.” Starting life as part of Siemens Wireless,

13 September 2011 39

Co m m u n i cati o n Des i g n RF & Microwave

Cinterion launched the first GSM data module for M2M applications in 1995. Spun out of Siemens, the company was acquired by Gemalto and is now run, according to UK manager Mark Foster, as a ‘company within a company’. “We have an industrially focused road map focused on telematics, smart metering, health, remote maintenance and security,” he explained. “Our modules fit into open architectures and can support Java as an on board OS or work with an external microcontroller.” The M2M market originally developed around GSM communications, but the network operators didn’t really focus that closely on the opportunities. But, according to Cinterion’s UK channel manager Neil Bosworth, that’s changing. “Operators are tuning in more. They ignored M2M before because it was a small market compared with handset traffic. Now, they all have M2M activities because there are more machines than people.” And he said the approach is suited to all kinds of data rate. “Most M2M applications transmit only around 100byte of data per day.” While the 2G network would seem to be the obvious environment for M2M links, Foster said there was a drive to the use of 3G. “It’s being driven by the need for connectivity, rather than data rate. Another reason is that, in some countries, the future of the 2G network is suspect, so developers want confidence and are turning to 3G.” Bosworth added: “But there is still a lot of

The IQRF range allows mesh networks to be created that transmit data at up to 115kbit/s over distances of up to 700m

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Cinterion offers a range of modules to support GSM, GPRS, EDGE, UMTS and HSPA based communication

network available to 2G; for example, a lot of smart metering applications are using the 2G network.” But why should a developer use GSM in this application, rather than ISM? Bosworth continued: “The trouble with ISM is the equipment operator has to use a ZigBee based approach and doesn’t have control over the backhaul. A smart meter could use ISM to link to a wireless router, but that link would not be under the control of the utility company. By using GSM, the utility company is assured of a secure link.”

Cinterion’s BGS2, part of the company’s value range, is said to be the smallest 2G wireless module available in the lga format. The BGS2 is available in two options: quad band (850/900/ 1800/1900MHz) GPRS class 10; and dual band (900/1800MHz) GPRS class 8. All modules come with full type approval. Both options can download data at up to 85.6kbit/s, with the maximum uplink rate of 42.8kbit/s and 21.4kbit/s respectively. The module is suitable for use in remote health care. Cinterion believes devices ranging from blood pressure measurement and scales to glucose meters and spirometers will benefit from the ability to transmit data via the mobile network. It’s easy LPRS continues to expand its point to point easyRadio portfolio, with the latest addition being the easyRadio Advanced range of transmitters and transceivers. These parts allow developers to change many of the parameters of the radio to suit specific requirements. Multiple channels and frequencies are supported, with a choice of FSK and ASK modulation. Available in 433 to 434MHz and 868 to 920MHz options, easyRadio Advanced allows users to program transmission frequency, output power, serial data rate and bandwidth. www.lprs.co.uk www.cinterion.com

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Go with the flow Design flow developments are enabling more capable signal processing and communications systems. By Joy Lin.

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Fig 1: Model-based design Research

Requirements

Design Supervisory logic Algorithms

Implementation C, C++ mcu

Vhdl, Verilog dsp

fpga

Integration

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asic

With Model-Based Design, system engineers can model the behaviour of digital, analogue and rf components Lin: “System and perform design tradeoffs in simulation, which can be difficult or engineers can impossible using paper based design focus on reviews. Algorithm developers can then reuse and elaborate the same models design to build and test more detailed designs. innovation to Later in the development process, achieve higher these models can become the design artefacts from which hardware performance.” engineers generate HDL code. At that time, system level models and tests can be reused as a test bench to validate the performance of the HDL implementation and the final hardware against engineer needs to break down the high level the model level results. functional block diagram into its digital and rf components. Model-Based Design means these Defining requirements components can be combined into one model Modern signal processing and communications that allows for design trade offs to be made and systems are characterised by complex and for system performance to be analysed to interconnected digital, analogue, mixed signal, ensure that it meets the high level requirements. radar and rf subsystems. At the Optimal design trade off often comes from beginning of a project, years of hands on experience in the digital and rf requirements are often incomplete domains or from heritage design. Model-Based or conflict, so the first step is to Design relies less on heritage knowledge and use the high level requirements to more on system level simulation. derive well defined function level The model can be used as a set of executable requirements, which can then be specifications, with model level test vectors used portioned into relevant as the acceptance criteria. Often, the process of subsystems. creating the models and running simulations As an example, an ISM band uncovers requirement errors at the beginning of transceiver may be required to a project, when they are less expensive and handle frequencies from 862MHz easier to fix. The time and effort that engineers to 928MHz and from 431MHz to invest in creating the executable models at the 464MHz, with data rates ranging requirement stage will pay significant dividends from 1kbit/s to 300kbit/s, various in the latter stages of the design process. receiver sensitivity specifications Aerospace companies who use Model-Based (bit error rate, BER) and Design typically reduce their verification time by intermediate frequencies. 90%, primarily because bugs are typically To implement these discovered and removed in the design and requirements, the system simulation stage, instead of at the test stage. Test and verification

ontinuity in the design flow is becoming critical if engineers are to meet tighter budget and time constraints when developing next generation signal processing and communications systems. Traditionally, system engineers, algorithm developers and hardware engineers use different tools, which can introduce gaps in the workflow. However, with Model-Based Design, engineers use a common set of models in an extensible environment to define requirements, develop algorithms, implement or target hardware and test and verify their designs. Requirements analysis and high level design tradeoffs have often been done on paper, with Excel or with expensive prototyping hardware. Algorithm implementation in C or a hardware description language (HDL) is done manually, as is testing and verification. This process often requires several iterations between the algorithm design team and the C and HDL teams, due to unclear requirements and design documentation or inherent design difficulties.

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System Design E n g i n e e r i n g M anag e m e nt

Tradeoff studies Engineers can perform simulations early in development and make effective tradeoffs in designs that include both digital and analogue/rf components, while ensuring the various design options satisfy system level requirements. To study how best to meet the system level BER requirement, engineers can explore design options by swapping in different types of IF receiver architecture and modulation and demodulation schemes in one tool environment. Simulating the models can also eliminate guess work from the link budget design and analysis. Instead of relying on heritage design to understand what would be adequate margins in each phase, effective frequency margins can be lowered because gains and losses at each stage can be better understood via simulation. In the past, a system level tool was used to create an overall representation of the design. This tool was different and disconnected from those used for detailed modelling and exploration of system algorithms. Recent advances in algorithm modelling tools help engineers to build and maintain an integrated model that captures overall system complexity and the interaction of various subsystems. Verifying implementation A key benefit of building models and running simulations of executable system specifications is that those models can then help engineers to improve the efficiency and the quality of results

of the final system implementation. As a signal processing or communications system design proceeds, an early elaboration stage is identification of those portions of the design which can be implemented on a fixed point dsp, a microcontroller, an fpga or an asic. To do so, engineers convert early floating point designs to fixed point, but this conversion is a major challenge. Previously, engineers would take floating point system models and recode major portions of the design in fixed point C or HDL, resulting in delays, bugs, flaws and wastage of time and resources. Rather than writing or rewriting the algorithm in C and converting it manually to fixed point, Model-Based Design tools support automatic fixed point conversion. In many cases, engineers can build and maintain a single polymorphic reference model that can run in floating or fixed point modes, as needed. Verifying that an implementation meets the design requirements has traditionally been an iterative process. C or HDL code – either written manually or generated automatically – is delivered to design engineers, who must write tests to evaluate the code, isolate errors and issue change requests until the implementation matches the design. In Model-Based Design, the models used to design algorithms can also be used to generate C or HDL code. Verification can be completed through cosimulation of the system level models with the final C or HDL design. At this stage, system level

models are reused as the test bench. This reuse saves time writing test bench code and creating test vectors. Close coupling between design, implementation and verification not only saves time when compared to coding manually, but also helps to minimise implementation errors. Conclusion With Model-Based Design, engineers use models as a golden reference that links every part of the development process – requirements, design, implementation and testing. Creating models at the start of the process saves more time at every subsequent stage through reuse or elaboration of design elements or by identifying errors when it takes time and money to fix them. By reusing models, system engineers can focus on design innovation to achieve higher performance. Several recent advancements – including multidomain modelling, stream processing algorithms with full integration to the system level models, fixed point design and C and HDL code generation and verification – streamline, integrate and automate many critical steps in the design of complex signal processing and communications systems. Author profile: Joy Lin is The Mathworks’ aerospace and defence industry marketing manager. www.mathworks.com

Fig 2: Radar model with target detection Trigger Out 1

In1

Out 1

In1

Out 1

In1 Out 1

In1

Out 1

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In1 d

rf transmitter

Aircraft

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In1 Out 1 Signal amplitude 1

In1

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link budget (dB) Input pulse Tx gain Tx antenna gain Path loss Target return Rx kTB Rx noise figure Total

-30.0 52.3 40.0 -172.0 -29.9 130.0 -7.9 -17.5

Tx amplitude (dB)

Tx pulse Rx amplitude = Tx amplitude – path loss + aircraft return = Tx amplitude – 10log10(AircraftDistance4) + 10log10(AircraftCrossSection(lambda2)/4n3)

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13 September 2011 43

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