Next-generation radar systems are critical to providing situational awareness of the entire networked battlefield. Active Electronically Steered Array (AESA) antennas have revolutionized the performance of modern radars, communication and electronic warfare systems by greatly reducing the maintenance costs and failure rates, enhancing scanning speed and accuracy, more resistant to interference and providing multifunction capability.
Active electronically scanned array (AESA) radar systems operating in bands from UHF to X-band can produce very high-pulsed powers for surveillance applications or multiple simultaneous beams for shorter distance targeting and acquisition applications.
They contain a number of solid-state transmit/receive (T/R) modules that are combined at the antenna input. This array architecture enables simultaneous functions ranging from radar surveillance and fire control to jamming and advanced data link communications. Multifunction AESA versatility also enables dramatic improvements in target tracking, they allow for high-precision, multi-target tracking spanning both short- and long-range threats. The maturity, production ability and low risk of the GaN-based Radar Modular Assemblies are underpinning development of next generation radar system.
The EM systems like Transmit and receive (T/R) modules are assembled with monolithic microwave integrated circuits (MMICs) and large discrete (off-chip) magnetic components such as circulators, isolators, and inductors. These components use magnetic materials that exploit unique physics and functionality not available in electronic components. For example Circulators in T/R modules use magnetic materials to efficiently control the flow of electrical signals between the antenna terminal, transmit power amplifier, and receiver low noise amplifier.
However, current magnetic components such as circulators, inductors, and isolators, are bulky and cannot be integrated with miniaturized electronic circuitry. High packing densities achievable on MMICs, the result of decades of investment in scalability and integration of elements such as transistors, resistors, and capacitors on semiconductor chips, are not achievable with current magnetic components. As such, critical magnetic components must be assembled off-chip, which adversely affects cost, size, weight, and power (C-SWaP) and constrains RF system design.
DARPA launched Magnetic Miniaturized and Monolithically Integrated Components (M3IC) program in 2016 with a goal to achieve circulators, isolators, and gyrators that can be integrated into standard semiconductor processes and replace discrete devices. This will reduce the size, weight, and power (SWaP) of magnetic components, enhance their functionality and offer new mechanisms for the control and manipulation of electromagnetic (EM) systems for communications, radar, and electronic warfare (EW).
For instance, tighter integration of electronic and magnetic components could yield smaller radar systems, higher bandwidth communication over longer ranges, improved jam resistance, and more resilient EW systems. The miniaturization and lighter-weight system design of T/R modules shall allow AESA systems to be placed onto smaller operational platforms – such as unmanned aerial vehicles (UAVs) – that would otherwise be unable to provide critical sensor data in the battlefield.
DARPA’s announced funding for Metamagnetics for Magnetic, Miniaturized, and Monolithically Integrated Component (M3IC) program. Mike Hunnewell, director of business development, said in a statement, ” the research will focus on integrating miniaturized magnetic components into the microelectronics mix, with the goal to catalyze chip-based innovations in radar and other radio frequency (RF) systems. The program will span over the next five years and will hopefully open a pathway to more capable electromagnetic systems.”
The M3IC program planned to develop integrated magnetic components on semiconductor substrates to reduce size and enable new functionality for DoD electromagnetic systems. In order to meet the program goals, the M3IC program will overcome three primary technical challenges.
The M3IC program is divided into three technical areas: integration of magnetic materials and systems with semiconductor technology; accurate and efficient modeling of magnetic phenomena from the molecular to the component system level; and exploitation of magnetic phenomena in innovative component designs relevant to EM systems that are important to DoD.
The first technical challenge to integrating magnetic components is growing and patterning high quality, uniform, thick, and temperature-stable magnetic films on standard semiconductor substrates while preserving the properties of both the magnetic material and the semiconductor circuitry. This will require techniques that address the mismatch in both the lattice constant and the coefficient of thermal expansion between the magnetic film and the semiconductor substrate.
The second technical challenge is that existing field and circuit modeling software is incapable of accurately predicting the impact on system performance of nonlinear, non-reciprocal and time dependent magnetic phenomena. Currently, modeling capability exists in both domains, but coupling the models across the widely separated time and length scales is a cumbersome, device specific, manual process.
Therefore the second goal of the program is capturing this nonlinear, non-reciprocal, and time-varying behavior at the micro-scale, and translating that behavior into its system-level impact. These enhanced modeling codes will enable efficient and accurate a priori design and optimization of integrated magnetic components and discrete nonlinear devices that leverage these magnetic phenomena, such as frequency-selective limiters (FSL) which use the nonlinear excitation of magnetic spin waves to attenuate unwanted signals above a threshold power, and signal to noise enhancers (SNE) which use the same phenomenon to boost desired signals above a threshold power while simultaneously suppressing unwanted noise.
The third technical challenge is that FSLs, SNEs, and other DoD-relevant nonlinear and nonreciprocal magnetic components demonstrated to date are bulky due to the requirement for large bias magnets, and have marginal performance that restricts their use despite their potential for improving system survivability.
To meet the challenge of reducing size and increasing performance, the M3IC program will explore ways to control and optimize the interaction between the EM fields and magnetic materials, first through an empirical campaign, and ultimately incorporating new design tools and improvements in integrated magnetic materials todeliver new and improved functionality and performance in smaller form factors.
The success of the M3IC program will create the capability for seamless co-design of integrated magnetic materials and semiconductors that will enable reduced size, increased bandwidth, and improved stability and power efficiency in EM systems.
Vincent Harris, University Distinguished Professor and William Lincoln Smith Chair Professor, electrical and computer engineering and chemical engineering, received in collaboration with Quorvo an $8M grant (2017-2019) from the Defense Advanced Research Projects Agency for a project, “MAgnetics on GaN for Next GEneration T/R Systems (MAGNETS),” which involves the Integration of active and passive elements in GaN-based transmit and receive modules.
Modern radars, communications and Jammers are based on GaN technology. Radio frequency amplifiers made with GaN are five times more powerful than the ones in radars using traditional semiconductors, the Raytheon Company reported.
ECE Professors Receive Award from DARPA MTO
ECE Assistant Professor Matteo Rinaldi (with Co-PI Professor Nicol McGruer) has received a $2,682,990 award from DARPA MTO to develop a magnetic-free “Microelectromechanical Resonant Circulator (MIRC)” orders of magnitude smaller than any existing implementation of circulators available to date, fully compatible with lithographic fabrication processes used to manufacture Radio Frequency (RF) integrated circuits.
The proposed MIRC is capable of achieving the linearity, bandwidth, insertion loss, isolation and power consumption levels required for many civilian and military applications at a chip-scale size, enabling RF systems to simultaneously transmit and receive at the same frequency (STAR), doubling spectrum efficiency.
Which is one of the key enabling features for the development of the Internet of People in which billions of virtual and physical objects are wirelessly connected together to create large networks of empowered people interacting securely with adaptive and resilient environments.
This project is part of the DARPA Signal Processing at RF (SPAR) program which seeks to design, build and demonstrate RF signal processing components that can remove in-band interferers from the desired receive signal prior to the receiver electronics.
The components developed under the SPAR program will not only achieve the desired levels of signal isolation, but will also have the low noise and high linearity required of components operating directly at the RF front-end. SPAR will significantly improve interferer resistance while augmenting spectrum efficiency, which will allow radio and radar operation in increasingly congested and contested RF environments. Furthermore, SPAR will enable RF systems to simultaneously transmit and receive at the same frequency (STAR), doubling spectrum efficiency.
In this collaborative project, led by Prof. Rinaldi, the Northeastern university team will work with a team from the University of Texas at Austin (sub-contractor) led by Prof. Andrea Alu’.
Krishnaswamy and his student develop miniaturized circulator
They have also developed miniaturized circulator that allows the transmitter and receiver share a single antenna. Circulators are normally used in conventional communication circuits to allow transmitter and receiver share the same antenna. A standard RF circulator is a three-port ferromagnetic passive device used to control the direction of signal flow in a circuit. In simple terms, magnetic fields are used to channel electromagnetic flow in a specific direction, thereby providing two-way communications on the same frequency channel by allowing, for example, two transmitters to use the same antenna. The downside, according to the researchers, is the bulk and weight of a standard circulator.
But circulators built in this manner are often expensive and too bulky to insert into a smartphone. Plus, the magnetic fields they use would disrupt other functions if ever placed within an electronic device. To overcome that limitation, Reiskarimian implanted silicon transistors on the face of a CMOS chip in an arrangement that reroutes signals as they are captured by both the transmitter and the receiver in order to avoid interference. “You essentially want the signals to kind of circulate in a clockwise sense,” Krishnaswamy says.
“For now, the new chip does not have a high enough broadcasting power level to connect to a mobile network. It’s in the neighborhood of 10 to 100 milliwatts, which is about where a Wi-Fi network typically starts, but mobile operates at higher levels. There are a few ways that Krishnaswamy is already planning to try to bolster the power level, such as by rearranging the components of the chip or choosing different hardware to build it,” reports Amy Nordrum in IEEE spectrum.
Columbia University in New York integrate magnetic materials into standard CMOS process
Non-reciprocal components are predominantly realized using magneto-optical materials, which are incompatible with integrated-circuit fabrication processes. For this reason, non-reciprocal components today are bulky, expensive and do not find widespread deployment. The ability to integrate magnetic-free non-reciprocal components in modern semiconductor processes would enable exciting frontiers for communications and sensing.
Researchers at Columbia University in New York have developed a potential solution to this problem without any magnetic materials. Not only is the research reported in Nature Communications non-magnetic, it can supposedly also be integrated into a standard CMOS process. Moreover, the proposed technology can also operate well into the millimeter-wave bands, possibly enabling two-way communication for upcoming 5G telecommunication services.
“We exploit the fact that conductivity in semiconductors provides a modulation index several orders of magnitude larger than permittivity. While directly associated with loss in static systems, we show that properly synchronized conductivity modulation enables loss-free, compact and extremely broadband non-reciprocity, “write the authors. Our approach is inspired by staggered commutated N-path switched capacitor filters, which were recently shown to exhibit non-reciprocal phase shift, and is based on adding suitably synchronized conductance modulation sections to transmission lines.
We apply these concepts to obtain a wide range of responses, from isolation to gyration and circulation, and verify our findings by realizing a millimeter-wave (25 GHz) circulator fully integrated in complementary metal-oxide-semiconductor technology.” According to Harish Krishnaswamy, lead of the research project, the mm-wave circulator enables mm-wave wireless full-duplex communications. This could revolutionize emerging 5G cellular networks, wireless links for virtual reality, and automotive radar.
Beyond opening important directions for wireless communications and radar technology, these principles are also directly extendable to nanophotonic components, and pave the way to the realization of magnet-free photonic topological insulators for strong topological protection and one-way transport.
As this is a new approach, there are many factors to consider before this technology can be considered viable. Evaluation of environmental behavior, power handling, frequency behavior, and device characterization are all necessary steps before this technology can be leveraged in devices.