Wide-band mechanically tunable W-band (75-110 GHz) CW Gunn diode oscillator

Experimental results are presented for a wide-band mechanically tunable CW Gunn diode oscillator in the 75 to 110 GHz range. A variable height radial mode resonator emersed in full height WR-10 (0.100 x 0.050 in.) rectangular waveguide produced a continuous tuning range of almost 20 GHz. Corresponding output power of +10 dBm + or - dB was obtained when an adjustable waveguide short, located approximately 5/4 lambda g behind the diode, was simultaneously optimized at each frequency. The FM noise spectra for an oscillator tuned to 94 GHz was in agreement with recently published results: typical measured noise deviation over the video range 0 to 2 kHz off the carrier frequency was less than 30 Hz rms, single sideband, referenced to a 1 Hz bandwidth at 1 kHz off carrier and exhibited a 1/f sub m dependency in this region. The best CW results obtained thus far were an output power of +18.3 dBm at 94 GHz with 1.27 percent conversion efficiency.