A Compact Extremely High Frequency MPM Power Amplifier

The development of a compact radio frequency (RF) vacuum power amplifier for high-resolution airborne radar is described. The amplifier, a microwave power module (MPM), operates in the upper millimeter-wave frequency band of 231.5-235 GHz providing a peak output power of 32 W. Common with previous extremely high frequency MPM development at Electron Devices, the {G} -band MPM consists of a periodic permanent magnet focused serpentine waveguide traveling wave tube (TWT) and a miniaturized 20-kV electronic power conditioner. Input drive to the MPM for saturation is around 10 mW. Low-loss chemical vapor deposition diamond WR-4.3 windows serve as the input and output ports of the TWT. Due to the high duty of the radar application, a four-stage TWT collector is employed for beam energy recovery. The MPM operates from a 270- \text{V}_{\sf {dc}} power source. Two MPM configurations have been constructed: a single integrated unit for laboratory testing and a split-package configuration for integration in a standard electro-optical/infrared gimbal. The split-package flight test unit has a maximum prime power requirement of 176 W, corresponding to an overall amplifier efficiency of 9%. The radar sensor has been flown on a modified DC-3 test bed with high-resolution real-time video imagery obtained under cloud-obscured operating conditions.