Fast processors, FPGAs fuel radar/EW signal processing performance

1Radar and Electronic Warfare (EW) designers' thirst for more and more data is driving innovation at the signal processing level as embedded computing suppliers work magic with FPGAs and processors to create intelligent, fast sensor networks.

The need to know where and when the enemy will strike is no less important today than when the allies cracked the allegedly unbreakable German Enigma code during World War II. The only difference today is the sophistication of the technology on either side. Modern Electronic Warfare (EW) systems can detect, collect, and catalog just about every signal, while radar systems being developed today will be able to track dismounted personnel, small objects at sea, as well as enemy fighters. To make these capabilities possible, embedded computing wizards are packing as much processing power as possible at the payload level on the platform, right next to the sensor. They mix together components such as GPGPUs, multicore processors, FPGAs, and complex software algorithms in different configurations designed to meet the low Size, Weight, and Power (SWaP) requirements demanded by their military customers.

Sensor technology and the need for greater bandwidth are driving military electronics designs, especially in radar and electronic warfare applications, says Ray Alderman, Executive Director of VITA. “What the processor and sensor technology enables us to do is absolutely incredible. Every aircraft has a signature. When we hit an enemy aircraft with radar we can figure out where it came from, destroy that location, then figure out where it is going and eliminate that destination as well. The only problem with increasing bandwidth on the sensors is the ability to stream data over the RF links is still poor. Therefore, the focus going forward is to move the processor next to the sensor.”

“Department of Defense (DoD)-oriented customers want to be able to perform data exploitation onboard platforms to provide immediate actionable intelligence to the warfighter – avoiding delays and bottlenecks encountered when sending large amounts of data to a ground station,” says Paul Monticciolo, Chief Technology Officer at Mercury Systems in Chelmsford, MA.

“In the past Intelligence, Surveillance, and Reconnaissance (ISR) systems were aimed at finding that particular truck or plane in an area of interest; now they are required to have the capability to pick individuals out of a crowd,” says Vincent Chuffart, Embedded Computing Specialist at Kontron in Poway, CA. “Today’s sensor systems can detect everything, so integrators want to process that sensor data and extract all they can out of it at the sensor level before they transmit it to the warfighter.” Kontron puts a lot into small form factor designs such as 3U VPX to handle the high-speed processing and meet SWaP requirements, he continues. There is a trend toward smaller and cooler systems, especially with the vast majority of upgrades in front of us being just a refresh of existing equipment, Chuffart adds.

“Users are trying to detect and decode complex radar or communication signals so they need more channels and these channels need to be accommodated simultaneously,” says Rodger Hosking, Vice President at Pentek in Upper Saddle River, NJ. “An example would be a communication system that listens to multiple radios or communicates with multiple radios at the same time or a system that requires wider signal bandwidths for radar. Once these signals are digitized, higher data rates are required to move the data, which puts a bigger load on the DSP engine to accommodate the data so it can keep up in real time.” A higher level of system performance is required through more sophisticated signal processing techniques, higher-speed A/D converters to capture wideband signals, and faster FPGAs to do signal processing and process algorithms at higher rates, he adds.

Harnessing commercial processor technology

Embedded computing companies are leveraging commercial processor technology – whether from Intel, NVIDIA, or other companies – to drive the performance of radar and electronic warfare systems. “FPGAs and GPGPUs are excellent for front-end sensor processing, but the SWaP characteristics of multicore processors are enabling us to provide the type of performance and analysis of data that is typically done in a ground station,” Monticciolo says. “Some companies are working with mobile-class processors, but when you start doing massive correlations and graph-type processing, you need the performance of a multicore processor in a server-class solution. This also guarantees code portability – being able to run the same code on a 1U server in the ground station and in a small embedded processing system up on the platform.” Mercury has a high-performance embedded computing solution with their PowerStream technology performing radar processing onboard the Navy’s Aegis-class ships.

“On Intel Architecture, the advent of AVX and the coming of AVX2 with a fused multiply-add pipeline are significantly improving the applicability of Intel devices to signal processing applications, as is the increasing performance of the integrated GPUs,” says Peter Thompson, Senior Business Development Manager for high-performance embedded computing at GE Intelligent Platforms in Huntsville, AL. “Now that NVIDIA is shipping Kepler GPUs, we are seeing significantly better performance per watt than the previous generation Fermi offered. GPUDirect is helping us to reduce sensor-to-processor latency, and opening up some new applications such as EW that are time sensitive. The interconnects are keeping pace too – PCI Express Gen 3, 40 GbE, and 56 Gbps InfiniBand are starting to become available or are already out there, and are allowing us to keep the processing pipelines fed.”

“For many EW and DSP applications, our customers have found that the Intel Core i7 processor provides them with the right balance of performance and SWaP,” says Ben Klam, Vice President of Engineering at Extreme Engineering Solutions (X-ES) in Madison, WI. “The Intel Advanced Vector Extensions (AVX) supported by the Intel Core i7 processor provides excellent DSP performance with support for operations on 256-bit vectors.”

Managing power consumption and signal integrity

Processors do enable amazing applications, but also create serious headaches for embedded system designers with the heat they generate. Cooling the systems and keeping their power consumption low can be quite complex, especially as system designs trend toward smaller form factors.

“Two big challenges faced by embedded signal processing designers are power consumption and signal integrity,” says Denis Smetana, Product Marketing Manager for FPGA products at Curtiss-Wright Controls Defense Solutions in Ashburn, VA. “Devices continue to run faster, which requires more power. With so many high-speed signals, more exotic PWB material needs to be used along with special handling of high-speed traces and more detailed signal integrity and power integrity analysis. The super high-speed signaling is running the processors so fast that a lot of heat is being dissipated and as geometries keep getting smaller, leakage current gets bigger as a percentage of total power. And leakage current is very sensitive to temperature. This results in a significant power increase as temperature rises. Software/firmware also is needed to be able to utilize the larger processing performance.”

“There are some applications with DSP performance requirements that exceed the capability of the Intel Core i7 processor where customers add GPGPUs or FPGAs into the mix, but the cost is high,” Klam explains. “GPGPUs typically consume more power than embedded General Purpose Processors (GPPs), which in turn creates more heat that has to be dissipated. GPGPUs are driven by the consumer market, so product obsolescence can be a big problem for long-life embedded systems. And development is much more complex – software development in the case of GPGPUs and VHDL and software development in the case of FPGAs. We are also seeing a lot of demand for systems that require something smaller than 3U VPX can support,” Klam says. “We have developed a small form factor system, the XPand6000 Series, that utilizes COTS components – COM Express, PMC/XMC, and SSDs – to enable customers to rapidly prototype and deploy small form factor solutions.”

FPGAs and the front end

For the front end of signal processing solutions – where the signals are received by the embedded computing system – designers far and wide sing the praises of today’s FPGAs, whether Xilinx or Altera, for enabling the capabilities of modern radar and electronic warfare platforms.

“We are seeing people wanting to put more components of their radar systems in an FPGA,” says Jeff Milrod, CEO of Bittware in Concord, NH. “Altera’s Stratix technology is supporting this by placing a lot of floating-point capability in the front end. That way the system can aggressively integrate full imaging and even identify areas of interest before it sends data to the ground. FPGAs are needed because the rates are so high, now everybody seems to want direct RF conversion – so they get gigahertz sample rates flying and then handle them in the FPGAs.”

Compared with a GPP, the FPGAs are much better suited for real-time embedded systems. The GPP, while very fast, is not well connected to I/O and does not do real-time data processing as well as an FPGA. Pentek’s Onyx 71720 software radio module is used in radar, UAV, and communication signal processing applications and is based on the Xilinx Virtex-7 FPGA, used in radar and communication signal processing applications.

“FPGAs will continue to dominate digital signal processing for a myriad of reasons: mainly processor technology isolation and control of one’s own IP – the critical element in any real-time, signal processing platform,” says Doug Patterson, Vice President of the Military & Aerospace Sector at Aitech in Chatsworth, CA. Aitech’s military-grade 3U CompactPCI, 3U VPX, 6U VPX, and 6U VMEbus systems leverage FPGAs for radar and fire-control applications.

FPGAs process everything very fast and enable radar/EW integrators to have more control, to adapt and change their applications based on mission results, says Jane Donaldson, President of Annapolis Microsystems, in Annapolis, MD. “A major drawback with FPGAs for many is the expense of programming in VHDL, which adds labor costs and lengthens the design cycle,” she continues. To reduce time to market and development costs on their WILDFIRE FPGA boards, Annapolis engineers use their CoreFire solution to program FPGAs. It enables software programmers working on GPPs to also program FPGAs, Donaldson adds.

“The combination of FPGAs with SBCs, GPGPUs, and multicore processors in one system is how requirements are trending,” Smetana says. “For example, on the front end, FPGAs are well suited for parallel processing of sensor data, but then may feed the data to GPGPUs for additional parallel processing or multicore processors for sequential processing.” Curtiss-Wright is working with Tektronix to improve performance for wideband, low-latency processing for Digital Radio Frequency Memory (DRFM), electronic warfare, signal intelligence, and electronic countermeasure applications. Under the collaboration, Curtiss-Wright’s CHAMP-WB (“Wideband”) board will work with the Tektronix ADC/DAC FMC module, the TADF-4300, to become the CHAMP-WB-DRFM utilizing a Xilinx Virtex-7 FPGA.

FPGAs embracing ARM and OpenCL

“In the future we see embedded systems generally moving toward embracing ARM processor technology,” Milrod says. “There is a huge user community and infrastructure, it is quite efficient, and the performance continues to improve dramatically with 64-bit now emerging. Although currently there is no ARM COTS community in the military, interest in these designs is exploding in the Linux world and could very well catch on in military designs. Both Altera and Xilinx are integrating ARM into all their FPGAs from now on. At BittWare, we’ve started to integrate them onto our high-end VPX boards. The ARM can handle housekeeping functions while the massive bulk processing onboard is handled by the FPGAs and/or floating point coprocessors such as our Anemone many-core processor that is based on Adapteva’s Epiphany architecture.

“One standard that is getting interest in the defense community is the OpenCL framework,” Milrod says. “Altera has made a big push with it and they’ve really driven OpenCL on their FPGA designs. Within the defense community we’ve seen attention for OpenCL because some designers are dissatisfied with inefficiencies of running on GPUs, and then the difficulties they have when porting GPGPUs to FPGAs.”

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Sidebar 1: Radar signal capture and collection speed enhanced by new software tool
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Software challenges

Managing processors and the heat and power they generate is only part of the difficulty in creating complex signal processing solutions. “Integrating new, untested technologies while developing new, critical application software drains budgets and saps our customers’ resources and energy,” Patterson says. “Serial buses and parallel buses operate very differently, especially when time-critical messages must occur in order and in phase. Multiple serial buses can easily become out of sync and message passing becomes tricky with RTOS overhead to sort out the time sync issues. Command/response buses with tight, time-aware and synchronized higher-level data protocols are critical in real-time process control systems.”

“Radar and EW systems are so complicated with so many levels that one of our biggest challenges lies in offering software board support packages that work with various types of middleware,” Pentek’s Hosking says. “Often the code and middleware don’t interact well and don’t do what people expect them to do. This is the biggest challenge we face – providing tools that enable our customers to efficiently develop their unique and highly complex applications under popular operating systems like Windows, Linux, and VxWorks.”

Software solutions also help radar display processing engineers to combine “graphical data with real-time radar data and to create pictures using standard commercial technology,” says David Johnson, Managing Director for Cambridge Pixel in Royston, England. “The amount of data being processed and displayed is more complex than ever, so to create complex pictures of graphical data, we use high-end graphics chips from companies such as AMD and NVIDIA. We present a representation of the data generated by the front-end processors that makes sense – taking multiple layers of radar data, map data, chart data, and other sensor data fused together in one composite display. The system integrator decides how he wants the ISR information displayed.” Cambridge Pixel’s standard product – the SPx Radar Development Library – is a collection of software modules that can be used for radar displays as well as recording or tracking systems, he adds.

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Sidebar 2: Radar/EW Signal Processing companies
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