Low phase noise quartz BAW oscillator for space applications

A low phase noise, 5 MHz, quartz BAW oscillator has been developed for space applications. Considerable effort has been made to optimize the quartz resonator design used in this oscillator. Both SC and LD resonator cuts have been studied. Although promising results have been achieved with LD cut resonators, the best results have been achieved with 5 MHz, fifth overtone, SC cut resonators. Single sideband phase noise of -133/f ³ dBC/Hz for offsets from 0.1 to 2 Hz (equivalent to σ_y(τ) = 7E-14, for τ = 1 sec) has been achieved. This performance is within a factor of two of what is generally accepted as the theoretical phase noise limit for BAW quartz oscillators at this frequency. Details of resonator design, and circuitry are discussed, and phase noise data are presented. Although the results presented have been achieved using commercial electronic parts in the oscillator, the fundamental oscillator architecture is such that it can be implemented using readily available space qualified parts.