Novel varactor-tuned millimetre-wave Gunn oscillator

A novel design of varactor-tuned millimetre-wave second-harmonic Gunn oscillator is reported in which a varactor is mounted in a secondary cavity resonant at the fundamental frequency of the Gunn diode. This has the advantage that the varactor does not significantly load the Gunn diode at the output second-harmonic frequency, and enables the oscillator to produce the maximum possible output power from the diode while still offering varactor tuning and high Q.