Development of a Very Low Phase Noise Solid State Source At 35 GHz for ESR Spectroscopy

The selection of a solid state oscillator configuration to replace a 35 GHz klystron in a Varian E-110 ESR spectrometer is covered. The theory behind the transmission cavity stabilized Gunn diode oscillator is developed in detail. The microwave oscillator design utilizes a TE011 circular cylindrical cavity with a rectangular waveguide output. The Gunn diode is positioned in a coaxial line which is strongly coupled to the cavity. A novel electronic frequency tuning solution (and its design) involving the use of piezoelectric ceramics as motion transducers to tune the stabilizing cavity is presented. Phase noise specification, theory in oscillators, cavity discriminator measurement theory, and measurement procedure are detailed. The oscillator\u27s output power is 100 mW over the 1 GHz mechanical tuning bandwidth. Its phase noise was measured to be 125 dBc/Hz in one unit and -132 dBc/Hz in another unit. This performance is documented along with comparison to theory and an extensive phase noise literature search