Amplification for X-band radar systems must be efficient and clean, because a variety of signal waveforms are used in that frequency range for commercial, civil, and military applications. X-band frequencies usually range from 7 to 11 GHz or 8 to 12 GHz and sub-bands in between; radars may operate with continuous-wave (CW) or pulsed waveforms for defense tracking, air traffic control, and weather monitoring. In an amplifier such as the model BMCAP99109-1500 from Comtech PST, high power is achieved with high gain and low phase noise to maintain the integrity of radar waveforms in both forward (transmit) and reverse (receive) directions. The linear Class AB amplifier is based on GaN power-transistor technology and delivers 1500 W of peak output power from 9 to 10 GHz in both directions.
The rugged solid-state amplifier (see figure) must balance several parameters for effective airborne use. The amplifier runs on an aircraft power supply of +28 VDC and 12.5 A. It provides its high levels of power without overheating (or heating equipment around it) and is designed for operating altitudes to 30,000 ft. It works in 0 to 95% non-condensing humidity and meets MIL-STD-810F requirements for operating shock and vibration. It can boost pulsed signals with pulse widths from 0.25 to 100 μs with only 0.015 dB/μs pulse droop using as much as 62 dB of gain with only ±2-dB gain variation. The amplifier maintains fast pulses with accuracy, supporting 50-ns pulse rise/fall times.
The GaN amplifier requires some mass for thermal management and weighs 5.5 lbs. in a metal housing measuring 9.6 × 6.6 × 2.00 in. with SMA input and sample-port connectors and Type TNC output connector. X-band is a widely used radar frequency band, by military forces, for weather forecasters, and even by civilian authorities for traffic control by detecting the speeds of vehicles on public roads. Because radar returns reflected from a target may be low in amplitude, such an amplifier must maintain low distortion so that high accuracy can be achieved in any kind of radar reading.