Compact, efficient, high-power millimeter-wave power boosters
High-power millimeter-wave amplifiers are required for various new and emerging applications, such as point-to-multi-point wireless high-data-rate communications over multi-km ranges for residences and businesses. Driven largely by these requirements, both civilian and defense-related, researchers over the last decade have dramatically increased the power and bandwidth of a variety of vacuum electronic amplifiers in the millimeter-wave regime. The Naval Research Laboratory (NRL) has played a key role in the development of the science and technology that has made possible this increased performance. One attractive class of devices to arise from these efforts is the power booster, a relatively low-gain but very high-power amplifier that can produce significantly higher power than state-of-the-art amplifiers driven by comparable electron beams. At Ka band, NRL power boosters have produced from 1.5 to 4 kW of peak power from electron beams of ∼20 kV and up to 600 mA. The 3–5 dB gain of these amplifiers allows compact designs and high interaction efficiency. For example, with a multistage depressed collector the 4 kW output power device can achieve a power added efficiency of >40%.