Commercial and Military Innovation at a Crossroads for Radar and Wireless Networking Applications
by Tony Fischetti, Principal Technology Architect, MACOM
From the modern battlefield to commercial wireless infrastructure, bandwidth demands are growing exponentially. In the aerospace and defense (A&D) market, these demands are being driven by the need for low-latency communication and enhanced situational awareness and responsiveness among warfighters deployed across ground, sea and air domains, serviced by sophisticated radar systems deployed in manned and unmanned vehicles, operations centers and outposts.
In the commercial market, bandwidth demands are fueling the development of ultra-high speed 5G wireless infrastructure and small-satellite (small-sat) constellations targeted to comprise an end-to-end global network accessible from anywhere on the planet, enabling previously unimaginable data throughput speeds and network elasticity. This emerging network architecture holds the promise to immerse people, autonomous vehicles, machines and infrastructure in a unified, flexible mesh network that enables near real-time connectivity.
At their essence, the RF communication imperatives for A&D and commercial markets aren’t dissimilar — their common goal is to deliver data across the widest possible space in the fastest possible time. But the research and development engines that fuel these initiatives have converged in recent years. Where previously advanced RF and semiconductor technology consistently flowed from A&D to the commercial domain, accelerating innovation in commercial RF applications and volume scale manufacturing techniques have brought these respective development paths to a crossroads.
Aligned Interests in AESA Radar
The recent and rapid advancements in commercial RF technology development are attributable in large part to design methodologies that promote higher levels of component integration and innovative packaging techniques. This, in turn, enables more RF content to fit within a given form factor, and helps to facilitate the miniaturization of RF systems.
In the radar domain, DARPA’s Arrays at Commercial Timescale (ACT) program embodies A&D’s embrace of commercial innovation in an effort to streamline development and manufacturing cycles and reduce costs for next-generation radar, electronic warfare and communications systems. It aims to establish a common modular architecture for future radar systems by leveraging best practices established in the commercial domain.
The ACT program’s testbed features an advanced Multifunction Phased Array Radar (MPAR) architecture underpinned by Scalable Planar Array (SPAR™) Tiles comprising an active electronically scanned array (AESA) populated with hundreds to thousands of transmit and receive (T/R) elements. SPAR Tile technology leverages higher level RF assemblies, surface mount RF components and commercial manufacturing efficiencies to deliver a 5X cost reduction compared to legacy brick array architectures.
Together, the A&D and commercial markets stand to reap significant benefits from their combined efforts in AESA radar. The considerable cost savings made possible with the MPAR technology architecture promises to fuel the propagation of lower cost AESA radar for next-generation military and civil air traffic control infrastructure. In the commercial domain where AESA radar is implemented today in autonomous vehicles, and commercial airline collision avoidance and maritime guidance systems, MPAR technology sets a clear path forward for cost-effective massive MIMO 5G wireless infrastructure build-outs.
MMICs & Miniaturization
Within the radar system, MMICs have likewise followed a similar trajectory from A&D development to commercial commoditization. Here again, DARPA initiatives including the Microwave/Millimeterwave Monolithic Integrated Circuits (MIMIC) program and Microwave Analog Front End Technology (MAFET) program paved the way for the industry’s first multi-watt MMICs, designed and fabricated in-house at significant expense by the major defense contractors.
Flash forward to today, commercial fabs like IBM Global Foundries and TowerJazz are producing MMICs in huge volumes at low cost structures. What’s more, commercial RF component suppliers are transitioning from 32nm to 14nm and onward to 7nm and 3nm process nodes. This progression to smaller geometries has begun to enable 3 dimensional MMIC “stacking” whereby small form factor MMICs can be paralleled upward rather than outward.
With 3D MMIC stacking, planar AESA systems like MPARs benefit from higher integration that, in turn, enables small system footprints and/or increased RF content. This is especially important for AESA-based commercial 5G wireless systems, where the size of the antennas is heavily dependent on the frequency of the system. As we progress from 32nm down to 3nm, we can scale up the frequency levels through sub-6 GHz and onward to much higher millimeter wave (mmW) frequencies while still maintaining a high level of integration.
GaN Goes Mainstream
At the semiconductor layer, Gallium Nitride (GaN) was similarly borne of DARPA-funded programs aimed at developing compound semiconductors for higher output power, higher efficiency and higher frequency operation. At the time, GaN was an emerging technology, the economics of which were skewed toward military radar and electronic warfare programs that could afford performance at any cost. The perceived power density advantages of GaN on Silicon Carbide (GaN on SiC) versus GaN on Silicon (GaN on Si) distinguished GaN on SiC as the beneficiary of this early development, despite the immense attendant expense.
Today, thanks to intensive R&D and sustained investment led by the commercial RF market, GaN on Si has emerged as the clear winner over GaN on SiC in attributes ranging from cost structure to manufacturing capacity and supply chain flexibility. And industry data has demonstrated that GaN on Si delivers comparable and in many cases superior performance in key attributes like power efficiency, thermal conductivity and reliability. GaN on Si-based devices are also well suited for low-cost, space-saving plastic packaging, providing a compelling alternative to ceramic-packaged devices without compromising RF performance or reliability.
With GaN on Si ramping to commercial volume production, commercial 4G LTE and 5G wireless basestation infrastructure will benefit from GaN-caliber performance at LDMOS cost structures. In parallel, the A&D market will exploit cost-effective GaN on Si for the vast majority of RF-based military applications, with the exception of a handful of niche applications where a slight incremental gain in performance may be worth the cost penalty of GaN on SiC.
Department of Defense (DoD) agencies like DARPA will of course continue to lead the development of groundbreaking technologies that will one day find their way into commercial RF applications. But the strong need to invest in cutting-edge technologies is counterbalanced by an equally strong need to reduce strains on the defense budget, hence the DoD’s Better Buying Power (BBP) initiative aimed at improving efficiency and productivity in defense spending. This is intended to enable more rapid development and acquisition of high-performance A&D systems, at reduced costs.
The commercial sector has proven more than capable of absorbing the R&D burden from the A&D domain. Deep-pocketed companies like Intel, Apple and Alphabet devote billions of dollars annually to R&D programs targeted at high-revenue market opportunities, including RF-enabled technologies that in years past would have resided in the strict purview of the A&D market.
Take for example Intel’s choreographed drone demonstration during the 2016 Super Bowl halftime show. The speed and agility with which Intel was able to develop the software, navigation, GPS, and controller hardware to synchronize a fleet of 300 drones was eye-opening amongst market watchers in the fast-growing autonomous vehicle industry.
Meanwhile, commercial spaceflight company SpaceX routinely launches rockets and payloads into space, and has pioneered a new class of first-stage rockets that can be safely guided back to earth and re-used for subsequent launches. The cost savings enabled by this capability has surely resonated among NASA engineers.
This advanced rocket technology will be instrumental for deploying low-cost, mass-produced small-sats for commercial connectivity applications. Indeed, SpaceX and other commercial ventures are moving ahead with plans to develop and deploy small-sat constellations that could one day facilitate a low-cost global Internet service capable of delivering high-speed broadband to even the most remote regions of the world.
It’s easy to envision how commercially-developed, radar-enabled drone, rocket and small-sat technology could one day make inroads within the A&D domain, in the same way that so many A&D RF technologies have flowed downstream into the commercial mainstream. As commercial R&D investments in RF technology ramp up in parallel with continued innovation in radar, ICs and semiconductors, it will be exciting to see where and how A&D and commercial technologies intersect in the years ahead.