Voltage frequency control of a superconducting cavity stabilized oscillator (for atomic frequency standard)

A simple electrical tuning method for a superconducting cavity is described. Tuning is achieved by a reflection-type varactor phase shifter coupled loosely by a directional coupler to the transmission line which conducts the RF power to the cavity. The tuning section is outside of the cryogenic environment, and the tuning characteristics can be adjusted simply by changing the coupling coefficient of the coupler. The general characteristics of the method are discussed. The tuning properties of a superconducting cavity stabilized oscillator (SCSO), using a superconducting cavity as a frequency discriminator, are then calculated. The calculations are confirmed by preliminary experiments using a manual phase shifter in the 9.2-GHz SCSO. Tuning ranges similar to commercial precision quartz crystal oscillators can be easily obtained.<
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