GaAs W-band IMPATT diodes for very low-noise oscillators

W-band single-drift flat-profile IMPATT diodes were fabricated from GaAs MBE material and tested in a full-height waveguide resonant cavity with resonant cap. A quasi-optical parabolic Fabry-Perot resonator was used to determine the FM noise of the GaAs IMPATT oscillator. With a minimum noise measure of 20 dB at power levels around 20 mW, IMPATT diode oscillators can compete well with oscillators using Gunn devices. The (N/C)_FM=-82 dBc measured at 100 kHz frequency off-carrier and at Q_EX=95 is comparable to the value obtained from Gunn devices. The maximum available output power of 270 mW, however, markedly exceeds that of Gunn oscillators.