Microwave oscillators incorporating cryogenic sapphire dielectricresonators

摘要

Progress is reported on efforts to develop a commercially-viablenhigh purity X-band signal source incorporating a cryogenic sapphirendielectric resonator. The resonator design is of the whispering galleryntype to take advantage of the excellent electromagnetic fieldnconfinement offered by this geometry. Complications resulting from thenhigh spurious mode density of this type of resonator have beenneliminated by developing a very accurate and complete mode analysisnprogram which fully incorporates the dielectric anisotropies of thensapphire ring. This program allows the design of a window in thenfrequency domain where no unwanted modes exist, with accurate placementnof the desired mode at the center of this region. Preliminary evaluationnof the phase noise properties of simple oscillators incorporating thesenresonators have been performed. For example, in a dual-oscillatorncomparison of two oscillators operating near 13 GHz phase noise valuesnof L(f)=-55 dBc/Hz, -145 dBc/Hz and -161 dBc/Hz were obtained for offsetnfrequencies of 1 Hz, 1 kHz and 10 kHz, respectively