HRL Laboratories, LLC has received an award from the Defense Advanced Research Project Agency (DARPA) to develop and demonstrate high-efficiency monolithic microwave integrated circuits (MMICs) for radio frequency (RF) bands in the 50 to 110-GHz frequency range. The goal of the program is to demonstrate 71-76 GHz power amplifiers that convert more than 40% of DC power into RF power. Current state-of-the-art MMIC power amplifiers operating in this frequency band can convert only a little more than 25% of DC power into RF power. The key novelty of HRL’s approach is building MMICs using the highest frequency gallium nitride (GaN) high-electron-mobility transistor (HEMT). The superior combination of high fT>300 GHz, high fMAX>500 GHz and breakdown voltage achieved with HRL’s GaN HEMT is crucial for improving efficiency at frequencies exceeding 30 GHz. For the proposed GaN MMIC process, HRL recently reported a record power-added efficiency of 59% measured at a frequency of 32 GHz, and a record noise figure of 1 dB measured at a frequency of 37 GHz. These results were reported at the IEEE’s 2016 International Electron Devices Meeting and Compound Semiconductor Integrated Circuit Symposium, respectively.
The higher-efficiency of MMICs developed under this effort will reduce prime power requirements for the radios’ RF front ends by a factor of more than 1.6. It will also reduce the radios’ heat rejection requirements by a factor of more than 2 over the current technology.
This project could potentially enable insertion of E-band millimeter-wave radios in solar-powered unmanned aerial vehicles (UAVs) that can beam uninterrupted internet service over vast remote areas that currently have no service. E-band radio bands in the 71 to 76 GHz and 81 to 86 GHz ranges are attractive for power- and weight-constrained UAVs because their high operating frequency enables achievement of high directivity RF beams using small light antennas. They also can potentially support terabits-per-second data rates due to their large 6-GHz operating bandwidth. The weaknesses of current state-of-the-art E-band MMICs is that they convert only 25% of DC power into RF power—adding to UAV weight—and larger solar panels are required to provide power for gigabit-rate RF links. The proposed improvement in efficiency would reduce solar panel area required to power an E-band radio by several square meters.
The principal investigator of this project, Dr. Miro Micovic, led the team that pioneered HRL’s development of high-frequency gallium nitride (GaN) transistors and high-frequency GaN MMIC processes.
HRL Laboratories, LLC, Malibu, California (hrl.com) is a corporate research-and-development laboratory owned by The Boeing Company and General Motors specializing in research into sensors and materials, information and systems sciences, applied electromagnetics, and microelectronics. HRL provides custom research and development and performs additional R&D contract services for its LLC member companies, the U.S. government, and other commercial companies.
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