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Radar has long been the “backbone” technology of military electronics. It is the means by which an adversary’s troops and their movements can be detected from a distance, and has served as a reliable early-warning system for decades—whether on the ground or onboard ships and aircraft.

RadarRadar technology is ever-evolving and improving along with enhancements to RF/microwave components and developments in signal-processing components, such as digital signal processors (DSPs) and field-programmable gate arrays (FPGAs). It is also teaming with another technology, unmanned aerial vehicles (UAVs), to provide remote vision for military surveillance as yet another electronic asset meant to save lives in the modern military.

Of course, creating a remote-controlled UAV with a radar system, or even an on-board camera system, is no trivial task. Radar systems have traditionally relied on high-power pulsed signals to illuminate targets, which makes generating signals of sufficient amplitude with batteries on a UAV a challenge. The weight of the radar system is also a concern, since it must juggle the tradeoff between weight and transmit power to make it a viable subsystem onboard a UAV, or even an unmanned ground vehicle (UGV).

Then there is the matter of transferring intelligence on the radar returns from the drone to a remote operator, knowing that an adversary will be doing everything to interrupt and intercept those wireless signals. Wireless radio links must be secure, and they must also contain sufficient bandwidth for communications and control signals—as well as video signals for seeing what the drone “sees,” if the UAV is equipped with a monitoring camera.

Military interest in radar-equipped UAVs is so strong that research efforts analyzing the design challenges of creating UAVs with remote-controlled radar systems are spreading. For example, work at the University of Denver’s Unmanned Systems Research Institute has included the development of a fully working prototype, with antenna, amplifier, processor, transmitter/receiver, and wireless data link. The prototype weighs 230 g and consumes only 4.5 W power. It is designed to operate from an on-board lithium-polymer (LiPo) battery capable of supplying +11 V dc.

This prototype system was initially developed to serve the Federal Aviation Administration (FAA) and air-traffic-control applications. Consumer and commercial interest in UAVs is so great that there is concern among FAA officials about excessive airborne congestion and in-flight accidents, especially if UAVs are left solely to the control of their remote operators. Adding radar technology to commercial UAVs can prevent them from crashing into each other or, more importantly, into manned aircraft.

The University of Denver’s prototype is one example of what can be done with radar technology when limited to small size, low weight, and battery power. The same approach can be used for military purposes, to keep an “eye” on an adversary, and on troop movements from a remote distance, as has been done with various satellites.

One of the key enabling technologies for military UAV radar systems will be gallium-nitride (GaN) transistors and integrated-circuit (IC) amplifiers capable of producing the pulsed power levels needed at radar frequencies. Until now, GaN devices have been designed into circuits with the assumption that high bias power is available. Running on batteries will be a challenge for UAV radars.

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