100 MHz crystal oscillator with extremely low phase noise

In this paper, the performance of a newly developed 100 MHz crystal oscillator is reported. The oscillator has been designed to provide extremely low phase noise for applications such as Doppler radar and low noise PLL systems. It utilizes a fifth overtone SC cut quartz crystal resonator, with the entire oscillator contained in a low profile, 1 inch high by 2 inch square, package. This oscillator is presently available as an off the shelf product. Performance of this oscillator is discussed, with particular emphasis on phase noise. Theoretical and practical considerations for the achievement of low phase noise are discussed, as well as actual measured phase noise results in this device. It is shown that flicker of frequency phase noise dominates the spectrum at low frequencies (<500 Hz), with values of L(f)=140 dBC⊗f=100 Hz in some units. This result corresponds to unloaded Q values for the resonator very near the material limit (Q-1.6×10¹³/f₀)