No abstract

Ultra-high Q, X-band resonators, used in a frequency discriminator for stabilization of a low-noise signal generator, can provide a means of obtaining significant reduction in phase noise levels. Resonator unloaded Qs on the order of 500 K can be obtained in sapphire dielectric resonator (DR) operating on a low-order (i.e. TE(01)) mode at 77 K and employing high-temperature superconducting (HTS) films installed in the DR enclosure covers. Rigorous analysis for the determination of resonator frequency, modes, and unloaded Q have been carried out using mode matching techniques. Trade-off studies have been performed to select resonator dimensions for the optimum mode yielding highest unloaded Q and widest spurious mode separation. Field distributions within the resonator have been computed to enable practical excitation of the required mode. The results of both analysis and prototype device evaluation experiments are compared for resonators fabricated using enclosures consisting of conventional, metal sidewalls and covers employing HTS films as a function of cover conductivity.

Theory which predicts the behavior of magnetostatic volume wave propagation in yttrium iron garnet films with the magnetic bias field applied at an arbitrary angle was developed. Measurements performed with the bias field applied in the plane transverse to the propagation direction and the plane defined by the film normal and the direction of propagation, yielded results which were in good agreement with the theory. A variable nondispersive delay line, obtained by varying the direction of the bias field applied to an approximately constant forward volume wave delay line, was demonstrated. The time delay of this device was adjustable over a ±20% delay range and had a bandwidth of ∼150 MHz at x band.

No abstract

X-band Q factors of IO5 to lo9 have been obtained for sapphire dielectric resonators operated at temperatures in the range 4K to 77K. Based on considerations of exceptionally high Q and moderate signal handing capability, resonator use as a microwave signal generator reference element should allow realization of short-term frequency stabilities unattainable using alternative technologies.In this paper, we will report on recent results obtained at Westinghouse using sapphire dielectric resonators for AFC stabilization of an X-band, SAWR VCO-based source. The resonators are operated on a low order (%I) mode and employ high temperature superconducting films in the metal enclosure covers in order to obtain unloaded Q-factors of 3X105 to 5X105.Signal source flicker-of-frequency noise characterized by Sy(100H~)=SXlO-~~/f or L( 100Hz)=-96dBc/Hz and noise floor levels of -165dBckIz have been measured at X=band.While these results constitute state-of-the art performance, the measured values for flicker-of frequency noise is lOdB poorer than anticipated, based on the large value (72uVMz) of discriminator sensitivity obtained. Possible causes for current limitations in signal near-carrier spectral performance include resonator short-term frequency fluctuations resulting from environmentally-induced effects and/or frequencydrive (AM-to-FM) effects. Resonator vibration sensitivities (force ap lied parallel to enclosure covers) on the order of 1x10-5 per g have been measured.