Quasi-optical power combining of solid state sources in K/sub a/-band

Planar arrays of HEMTs (high electron mobility transistors) have been fabricated and tested at 37 GHz. The square arrays, consisting of 9 or 16 devices, have been mounted in a Fabry-Perot interferometer, which provides frequency locking. Measured power output and frequency spectra are presented and compared with analytical predictions. Output power is in the milliwatt range, and the line width of a typical array is about 50 kHz. The investigation has centered on using a semiconfocal Fabry-Perot resonator, with the array of sources placed on the planar reflector of the resonator. The curved reflector is partially reflecting to couple power out of the quasi-optical cavity. Source selection, quasi-optical cavity design and characteristics, and calculation of the circuit parameters for the oscillator interconnection grid are discussed.<>