From an electronic warfare (EW) perspective, offensive or defensive, in most engagements we do not control the pace or band of the electromagnetic spectrum operations. Rather, our systems react to the emitters or target systems’ capabilities, operations and locations. We must address as many of the emitters as possible to maximize the benefit to the warfighter, both effectiveness and lifecycle cost. Emitters of interest for our EW systems span communications, radars and unintended radiation sources; a subset are passive sensors, with no intended radiation at all. In many cases, radar and communications systems have moved higher in frequency over the decades, while legacy systems maintain persistence in the lower frequency bands. Our EW systems must detect, identify, locate, intercept, report and sometimes engage these sources of intended and unintended emissions, regardless of frequency.
The limiting factor for our adversaries is the efficiency and cost of the electronics. This, ultimately, controls the growth of emitters to higher frequencies. This growth necessitates a wideband EW system, or series of systems, that must address threats from VHF through mmWave, sometimes in the same mission. The proliferation of 5G high-band communication systems and automotive radar drives the efficiency and cost of high frequency electronics at a commercial scale. This creates a dilemma for EW systems: the volume driving this commercial scale generates tremendous increases in radar and communications network performance at mmWave frequencies on an almost annual basis. EW systems must operate in extreme environmental conditions, where automotive radar and 5G communications operate in comparably moderate conditions. Further, our adversaries have access to the same commercial electronics we do, with the ability to leverage the commercial scale to build and deploy high performance systems that threaten our warfighters’ ability to dominate the electromagnetic spectrum.
Higher band radars have better performance because they provide better range and Doppler resolution and require tightly integrated electronics. Radar systems will operate in higher bands when possible, where less congestion and noise impact the ambient noise floor. For a “threat radar,” these parameters translate to more accurate “weapons quality” tracks on aircraft, projectiles and UAVs. Radars with advanced high frequency electronics and apertures are becoming land mobile, meaning they can be moved rapidly and do not require hardened installations. The uncertainty of the location of these threat radars at any given time necessitates the effectiveness of EW systems to protect our assets from engagement.
From an electronic support measures (ESM and often referred to as ISR) perspective, we see the density of higher frequency emitters growing. Our adversaries can now develop radar and communications systems using commercial scale electronics to proliferate emitter density to the point where every platform must be equipped with a high performing EW system to maintain persistent awareness of the emitters on the battlefield. This awareness maximizes opportunities for electronic attack (EA) engagements or self-protection. Without addressing the higher frequency bands in this environment, our ability to maintain spectrum dominance erodes. This uncertain future necessitates investment in DoD-quality, high frequency electronics.
Since the end of World War II, the United States has maintained technological advantage over our adversaries as a deterrence and to provide technological overmatch when conflict arises. That technological advantage has waned in recent decades, partly because of the massive influx of commercial investment in electronics, manufactured mostly outside the United States, and the relative decline of investments in DoD electronics. High performance electronics designed and fabricated at scale offshore further intensifies the dilemma for EW systems. In 2019, Intel’s R&D investments alone were nearly 40x DARPA’s investment in the Electronics Technology program element of the DoD Budget Estimates, which makes pivotal investments in breakthrough technologies for national security. Today, our adversaries have open and commercial access to these technologies. Among the top 10 foundries by revenue in the world, a small percentage can produce International Traffic in Arms (ITAR) regulated parts for use in DoD systems. Recent efforts, such as DARPA’s Electronics Resurgence and OSD’s MINSEC initiatives, are addressing part of the dilemma.
DIVERGENT MILITARY AND COMMERCIAL REQUIREMENTS
There will always be divergence between DoD and commercial electronics requirements. In some cases, DoD electronics will require non-commercial sources, while continuing to use commercial off-the-shelf (COTS) electronics where possible. Certainly, the DoD will not be able to drive its unique requirements into commercial nodes and foundries at the volumes of commercial production. The primary differences between the two sets of requirements are:
Operating thermal environment - Broadly known temperature grades for active electronics are 0°C to 45°C for commercial, -20°C to 85°C for industrial and -55°C to 125°C for military. Some DoD applications exceed the military operational range, making commercial parts far out of reach for most DoD environments, with the exception of very few high grade automotive components. Due to the economies of scale in commercial electronics, the relatively small quantities of DoD systems prevent commercial investment and continued attention.
Figure 1 A future ideal radar warning receiver will cover all radar bands, to include the new 5G mmWave bands.
Bandwidth - International regulatory agencies control the spectrum used by 5G and automotive radar, for good reason. Next-generation EW systems ideally operate over all these bands to counter as many emitters as possible with a single system. The alternative of employing multiple banded systems, each intended for a different band or emitter type, applies pressure on the size, weight and power consumed by the solution. Figure 1 illustrates the challenge, showing current and planned frequency allocations for 5G, including the recent FCC auctions allocating spectrum at mmWave (i.e., auctions 101, 102 and 103). A future ideal radar warning receiver must cover low frequency radars through 5G frequencies. All components, from the front-end electronics to the transceiver and digital processing, contribute to the identification of signals, either instantaneously over a wide band or by tuning across a wide band. Current 5G and automotive applications are standardized by the spectral regulatory framework and are optimized for narrower bandwidths, preventing these electronic components from being used in broadband EW systems.
Assured supply chain - GlobalFoundries’ recent decision to stop development of a 7 nm CMOS production process sent shivers through the DoD supply chain. One of the few capable on-shore, advanced node CMOS foundries made a cost-driven decision to discontinue development, leaving DoD with no on-shore trusted source. This event blunted hopes of a small geometry CMOS, on-shore capability with the potential for trusted production. While relying on non-trusted and offshore foundries for high frequency DoD electronics will reduce cost, it leaves our ability to maintain critical supply chains to foreign corporate profit and loss decisions, political circumstances and, in case of a military or “trade war” conflict, the possibility of a complete embargo or shutdown in supply.
Secure supply chain and counterfeit parts - ITAR and Export Administration Regulations, while preventing the export of DoD technology, also help prevent malicious actors from participating in the fabrication of hardware going into DoD systems. In 2015, Bloomberg reported malicious hardware was found on Supermicro motherboards in DoD data centers, CIA drones and Navy warships. The chips were allegedly inserted at factories in China, though the story has not reached any conclusion. This scenario highlights the risk of not only board-level malicious hardware trojans, but also chip-level trojans even more difficult, if not impossible, to discover.
Obsolescence - The upgrade cycle of high volume commercial products, such as mobile smartphones and personal computers, is high. DoD systems will use the same component for decades beyond the day the manufacturer discontinues it, forcing “lifetime buys” and costly redesigns to prevent obsolescence, even when a redesign cycle is not necessary for any other reason. A commercial foundry will not continue manufacturing electronics nodes only used in decades old, low volume systems.
Figure 2 The F-22 Raptor development began in 1986 and is expected to fly for another decade or more. Source: BAE Systems.
As an example of the obsolescence challenge, the F-22 Raptor’s development began in 1986, and the AN/ALR-94 EW suite, one of the most technologically advanced systems on the F-22, was first delivered in 1999 (see Figure 2).1 Now, 21 years later, with 183 F-22s in service, the Air Force continuously faces the need for modernization to keep pace with adversary capabilities. As part of its mid-life upgrade, F-22 sensor modernization is due in the middle part of this decade. The F-22 is expected to be superseded by a sixth-generation tactical fighter sometime within the next two decades, underscoring that the fighter’s electronics are required to operate between two and four decades.
ASSURING MISSION SUCCESS
How do we solve the EW system dilemma? There is no single answer. To start, there are areas of common technical ground where development will benefit both DoD and COTS systems.
Modern mixed-signal nodes, such as 7 to 14 nm CMOS, 90 nm SiGe and the DARPA T-MUSIC 45 nm SiGe on-shore foundry, are driving higher frequency performance and higher computing capability for less size and power. However, having higher power densities, these nodes in the extreme temperature environment of DoD systems require exquisite cooling approaches, further increasing overall power consumption. We need continued advancement of high operating temperature electronics requiring less cooling, such as mixed-signal SiC that can operate at very high junction temperatures, reducing the need for active cooling. Future military operating temperatures may exceed 225°C, for which there are currently no mature solutions. If your organization has technology to offer, the DoD wants to see it.
Figure 3 A mid-frequency phased array using connectorized electronics becomes intractable as arrays move to mmWave and higher frequencies.
The rapid growth of multichannel phased arrays and extension into mmWave bands drives the integration of electronics into smaller packages. Heterogeneous packaging enables interconnects between ICs of different nodes, with each node optimized for its function, eliminating transmission lines on the carrier circuit board. As we push to higher frequency bands, the loss between die within the package becomes more critical. DoD systems require higher yield, lower loss heterogeneous packages to minimize the footprint of high frequency transceivers. As phased arrays move to mmWave and higher bands, circuit board and cable connections between the antenna elements and front-end electronics will be a non-starter to achieve the required electrical performance and size (see Figure 3).
The tighter integration of electronics enables the realization of high channel count, element-level digital phased arrays, adding low probability of intercept communications, massive MIMO, directional EA and multiband ESM to the radar functions. High input/output, reconfigurable logic devices, such as the xilinx VU13P, may aggregate hundreds of channels to form beams; however, they have grossly oversized logic and IP cores that go unused, unnecessarily increasing size, weight and power (SWaP). Reconfigurable beamforming ASICs are needed to reduce the SWaP of multifunction digital phased arrays.
ASICs are driving down the cost, size and power consumption of commercial systems. The rapid upgrade cycle of commercial electronics will require modification of these ASICs over time and occasional redesign into new nodes when the benefit outweighs the cost. Similarly, on DoD systems, incremental upgrades are costly but less frequent. A standing capability to rapidly upgrade and modify ASICs for incremental improvements is favorable for both DoD and commercial markets.
Attention to these areas of common ground among commercial and DoD markets will benefit both. With careful attention to detail and prudent design decisions, the innovators of DoD electronics will be able to leverage some, although not all, of the technologies being developed at commercial scale.n
REFERENCE
- Military Periscope, “AN/ALR-94 Electronic Warfare Suite,” www.militaryperiscope.com/weapons/sensorselectronics/electronic-support-measureselectronic-warfare/analr-94-electronic.