The sensor- and signal-processing challenges of electronic warfare

In terms of jamming for missile defense, anti-air munitions tend to use either infrared or radar for guidance once they’ve launched. Jammers on the radio, microwave, and infrared spectra can disrupt these signals. EW can also take advantage of tactical control of the electromagnetic spectrum to detect, analyze, and track potential threats. It’s a key part of modern situational awareness, as well as providing information for diplomatic insights or presenting options for possible offense before an attack arrives.

Sensors and signal processing technologies are essential systems on a variety of vehicles and in a variety of environments, including ground stations, aircraft, and ships. The BAE Systems Electronic Systems segment in Nashua, N.H., separates electronic warfare technology into four categories: electronic support (ES) or signal detection, electronic protection (EP), electronic attack (EA) or jamming, and mission support.

Another key element is quick response capabilities (QRC), which includes identifying new threats, or distorting or delaying the response to a signal. Electronic warfare contains offensive and defensive capacities, from preemptive targeting and spoofing, to countermeasures against adversary EW.

The U.S. Army C5ISR Center at Aberdeen Proving Ground, Md., shows some examples of what is considered cutting edge in electronic warfare with recent efforts to revitalize conversation around the subject, according to a Breaking Defense interview with Bill Taylor, cyber technology division chief at the C5ISR Center, and other researchers.

“Our ability to be able to detect those RF emissions, sense them, understand them at a rapid speed at the pace of operation is challenging,” Taylor says.

The U.S. Air Force celebrated the inaugural flight last year of new Gulfstream G550 business jets equipped with legacy electronic warfare systems from the EC-130H aircraft in an effort to modernize the EW-focused Compass Call fleet. L3Harris Technologies in Melbourne, Fla., is the lead the systems integration along with BAE Systems working on the EW suite, while Gulfstream provides the aircraft expertise and facilities. The changes to the fleet will include an open-systems architecture to make it easier to plug-in new EQ payloads to the aircraft as needed.

Meanwhile, experts from the Northrop Grumman Corp. Mission Systems segment in Linthicum, Md., worked on moving an electronic attack system to surface warships. They aim to find a balance of radio frequency versus available power and cooling, the organization’s Mike Meaney, vice president of land and maritime sensors, told C4ISRNET.

“On smaller ships sizes, we know it’s of great interest to the Navy to put this soft-kill capability with unlimited bullets on almost every ship that they have because the incredible protection electronic warfare offers you,” Meaney said. “We know that they’re interested in doing that, so we’re off on our own trying to develop what we think would make sense to go do in anticipation of the Navy having a requirement to do a scaled-down version of it.”

The system they’re talking about in particular is the Surface Electronic Warfare Improvement Program Block III (SEWIP). It shows a variety of offensive EW capabilities, including electronic attack against incoming anti-ship missiles. Integrated with the rest of the SEWIP system, it can provide Signals Intelligence, cover some of ESM [Electronic Support Measures) mission currently done by the Block II project, provide new and advanced communication waveforms and ways to connect to other ships and platforms, and function as simple versions of radar.

The Army is working on fielding several other new EW capabilities using the increase in processing power. The Electronic Warfare Planning and Management Tool for visualization is nearing maturity, as are the Terrestrial Layer Systems for EW and cyber. The former is a mission planning tool that maps out the military and commercial electromagnetic environment, while the latter is a planned vehicle-mounted platform.

“In addition to typical aerospace interfaces such as discrete I/O, analog sensors, and low-speed serial interfaces, customers are looking for high-speed interfaces -- multi-channel, high-definition video links, 10 gigabit or higher communication links,” says Emil Kheyfets, director of military and aerospace product line and director of engineering at Aitech Defense Systems in Chatsworth, Calif. “Modern aerospace electronics systems must be able to receive, send and process large amount of data from high resolution sensors and from other systems.”

The cyber domain is a source of some confusion in the industry, and it’s important to differentiate it here from the protection of ally online systems from digital attack, or “cyber security.” There is some debate over why cyber is considered a separate domain of warfare, while the electromagnetic spectrum is not, C4ISR.net points out.

The Navy, for instance, blends both with a new airborne electronic jammer, Rear Adm. John Meier, commander of Naval Air Force Atlantic, noted in April 2021.

“Now with the ability to do phased array, advanced jamming techniques, we really start to blur the lines, I think, between what we would consider traditional jamming with cyber warfare,” he said.

The Next Generation Jammer, mounted on a EA-18G Growler aircraft, covers all three portions of the electromagnetic spectrum. Referred to as radio frequency-enabled cyber, this type of combined technology comes in response to adversaries “moving a lot of their stuff onto wired networks,” said Bryan Clark, a senior fellow and director of the Center for Defense Concepts and Technology at the Hudson Institute, quoted by C4ISRNET.

“Security threats are happening through all phases of the life cycle of an embedded system,” said Aitech's Kheyfets. “Cyber attacks to gain access to servers or steal design information as well as take control of embedded systems or retrieve classified information are among the top threats.”

Those can include “from operational and data concerns to protecting design IP, as well as GPS service jamming or spoofing, wireless communication jamming or interception,” he said.

Sensors and signal processing for electronic warfare covers a broad spectrum of abilities. Multi-intelligence signal processing also can include artificial intelligence (AI) and machine learning, according to BAE Systems. Their algorithms collect geospatial signals intelligence from a wide swath of domains. They digitally identify and exploit acoustic, radar, communications, navigation, and optical signals.

Christopher Rappa, chief technologist at BAE Systems, notes three major recent changes: a more widely accessible ability to bring custom electronics to edge processing; open interface design; and AI and machine learning. New digital engineering paradigms like digital modeling, digital engineering, and better software paradigms like containerization and cloud-native computing on top of hardware have enabled bringing electronics to the edge much faster.

For BAE Systems, this also looks like partnerships with other companies like Intel, as well as various foundries and digital IP block providers. Two projects in particular, push in this direction: the $5 million DARPA T-MUSIC, which explores integrating mixed-mode RF analog and digital electronics into advanced onshore semiconductor manufacturing processes; and the $5 million Wideband Adaptive RF Protection (WARP) research project.

“These are both examples of us pushing tech further for higher speed electronics as well as better rejection of bad signals,” BAE Systems'

Rappa said.

The work of Mercury Systems in Andover, Mass., on digital RF memory (DRFM) systems shows some of the challenges in signal processing today as well. DRFM systems — usually broadband RF hardware, high-speed digitization modules and low-latency FPGA processing boards — can deceive adversaries’ radar pulses such as those used on missiles.

“There is a game of cat-and-mouse where seeker developers create smarter, higher functioning hardware, while DRFM developers counter the smarter seeker via test/training in anechoic chambers, open-air ranges and/or in laboratories,” says Joseph Styzens, product manager at Mercury.

“The evolution of test and training requires the ability to exercise platforms over wider instantaneous bandwidths (IBWs), narrower pulse widths, and denser operating environments with time-coincident emitters. Additionally, there is a continuous need for our platforms to be reprogrammed quickly with new waveforms or they need to learn how to adapt to the environment,” Styzens says.

In test and training. Styzens says he is seeing changes from limited IBWs and single-target returns to those that can sift through a variety of incoming information at once. For example, a proven traditional architecture for test and training might be a DRFM with 1 GHz of IBW per channel, which detects the frequency and then tunes the system.

"This tuning takes time that is no longer available with newer, faster platforms,” Styzens said. “These systems incorporate features for a mock environment such as simulating weather, inserting targets and applying jammers. For each target or EA return, additional channels are needed, increasing the amount of software, firmware and hardware. Newer, more advanced platforms recognize the traditional approaches and immediately discard returned information as false.”

Technology like RF systems-in packages (RFSiPs) offer many more channels than before, and the newest architectures can cover several staring RF channels which dynamically cover large swaths of frequencies.

“Merging the RFSiP with commercially available RF devices, whether discrete or integrated into the RFSiP, disrupts and transforms sensor chains,” Styzens said. “If we’re savvy in our architectural decisions, we can do things not previously possible in test and training, such as provide wider IBWs, multiple time-coincident emitters, direct-to-digital wideband staring, very narrow pulses in dense environments, with cognitive EW.”

For BAE Systems's Rappa, an important distinction lately in how BAE Systems thinks about electronic warfare sensors and signal processing is that they use more custom intellectual property blocks, which can be unique to specific EW or signals needs. No longer does each organization have to buy everyone from one “parts catalog,” he said.

As the digital landscape changes, EW today needs to improve its processing efficiency with broader bandwidth sensors and the ability to switch rapidly between different sensors. Relatively new tactics, such as one pilot controlling a swarm of drones, may include EW capabilities. So, how does this work?

An important distinction between EW and radar systems architectures is that EW systems operate bidirectionally much more often, says Denis Smetana, senior manager of DSP products at the Curtiss-Wright Corp. Defense Systems segment in Ashburn, Va. EW signals need to move as quickly as possible, which calls for low latency, he says.

Many of these capabilities are built on the Sensor Open Systems Architecture (SOSA) Reference Architecture, which defines modules, hardware elements and software elements according to SOSA open-systems guidelines. They provide a framework through which new waveforms or techniques can be introduced relatively quickly.

"Today’s backplane design must support the routing of high speed I/O signals,” Kheyfets said. “SOSA requirements help to simplify backplanes designs, since a standardized architecture reduces the number of possible VPX cards slot profiles and pinouts.”

The most critical component of an EW system at the plug-in card level is the front-end sensor processor, usually a tuner or field-programmable gate array (FPGA) card. This distributes sensor I/O data to other downstream plug-in cards.

SOSA-standard plug-in card profiles (PICPs) also support rear-panel fiber or coaxial cable interfaces, which remove many cable management problems, since they enable cabling within the sensor-processing chassis. That’s another design element that makes them well-suited for EW. There’s no need to disconnect cables when replacing a plug-in card, which reduces wear and tear and simplifies maintenance, says Curtiss-Wright's Smetana.

One recent development is the addition optical or coax connectors on the backplane to VITA 66 and VITA 67 provisions, as opposed to the previously common front-panel connections to cables leading to the sensors. Today it's common to see analog sensors and smart sensors with optical backhauls -- sometimes in the same system.

The SOSA technical standard also takes into account the flexibility needed to work with a wide range of antennae and sensor front ends.

Open standards, SOSA, and C5ISR

The SOSA Consortium, part of the Open Group in San Francisco, is an important part of the conversation today. SOSA defines accompanying quality attributes, such as modularity, portability, securability, and scalability, for the underlying reference architectures.

“The choices we provide are limited to maximize reuse, but they are there to allow for growth,” says Judy Cerenzia, vice president of forum operations, The Open Group. “Whether it is the way a SOSA Slot Profile is constructed or the number and type of protocols used in an AMPS string.”

Decision-makers in the aerospace electronics industry in regard to open standards and electronic warfare in the past year today have to consider whether open standards will prevent them from providing the best options, whether it will allow for innovation, and what it will cost, Cerenzia said.

For Mercury, SOSA aligned product development takes advantage of enhanced performance and reduced power consumption to adhere to the U.S. Department of Defense’s MOSA mandate, says Mercury's Styzens. “The SOSA technical standard reduces development risks and helps ensure significantly longer operational life cycles with benefits including reconfigurability, easier insertion of new technology and the repurposing of hardware, firmware and software.”

This also helps meet that goal of moving sensing closer to the edge, says BAE Systems's Rappa. “When you take things like a SOSA approach and can have different sensors of different modalities or different intelligence types, classically the program broke down because you had one sensor of one type going into a processor and the dissemination and processing of that data went into a central processing facility. By us being able to have better software and hardware architectures we can connect data from different sources closer to the edge.”

Doing that with the mission systems integrator or weapons system integrator means being more responsive and more relevant in the field. This is also where “smart algorithms” (artificial intelligence or not) also can be good close to the edge.

Mercury's Styzens points out that a few new products that use SOSA standards as part of their improved performance. The Avionics Modular Mission Platform (AMMP) draws 50 percent less power than current-generation avionics computers while delivering 40 time more performance. The SOSA-aligned, single-slot 3U VPX Models 5585 and 5586 are open architecture 3U products that feature high-bandwidth memory (HBM) that integrates memory directly on the module’s FPGA chip and shows a 20 times increase in memory bandwidth over traditional DDR4 memory, he said.

Rappa pointed out that it’s important not to make SOSA compliance the only design consideration when working on products with non-standard sizes, though. He specified a case where one might need to break a 15-slot SOSA rack into four boxes for size and space needs. Or, the box might need to sit next to a hot amplifier.

“If you want to put electronics on a wing tip or in the top of the tail, you can’t put a piece of rack mounted equipment there. Even within the same aircraft there’s not one size fits all,” he said.

“There will always be cases where a proprietary optimized system provides better SWaP than an open standard option,” Cerenzia said. "The drawback is the proprietary system is not useful in other applications.” 

Relatedly, Rappa says his organization is looking for and seeing more demand for different blocks from different IP in the same product, some from major suppliers, some from an electronic design automation providers, some from a foundry. BAE Systems is using interfaces that offer modularity at very tight levels of integration at the chip level to fit all of these together.

"The ecosystem of collaboration is integrated on the nano scales,” Rappa said.

What does the future hold for signal processing in electronic warfare? Some Army researchers are working on atomic sensors, although Breaking Defense cautions that this is still in the early stages of research. The Army is also looking for ways to extend EW across longer distances, to detect adversary electromagnetic sensors, and methods to tell whether ally EW attacks (which are often silent) did what they were intended to do.

Development times have moved from years to months, Rappa noted. “If you’re playing this cat-and-mouse game against countermeasures, if you’re going to be responsive, your timeline always has to be faster than your competitor. What I predict is that will move from us talking about development timelines and integrations and updates as major upgrades to this timeline being so fast that it’s almost real time. Every time your plane lands new capabilities are being added to it. It's taking what it learns and applying that. It’s going to surpass our ability to think about designs.”

He added that it may take anywhere from five to 50 years to get to that point. Overall, though, he says to look forward to better power efficiency and more cooperative communications, perhaps with allies coming up with new waveforms to talk around new source of noise.. That type of development will need to happen at the “speed of the sensor.”