A small sapphire tuning wedge device is used in a technique for solving a mode-purity problem associated with a sapphire dielectric-ring resonator that is part of a cryogenic microwave frequency discriminator. Such a resonator is typically used to stabilize the frequency and ensure the spectral purity of a microwave signal generator by frequency multiplication from a 5-MHz quartz-crystal oscillator. NASA Tech Brief. 8.5" x 11"
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