Realizing Ultra-Low Phase Noise 100MHz Crystal Oscillator Utilizing Modified Leeson Model

This paper presents the design and implementation of an ultra-low phase noise 100MHz crystal oscillator, along with the development and simplification of its noise theory. Specific circuit designs and noise measurements are provided. The noise theory encompasses the oscillator's primary noise sources, offering a treatment approach ranging from oscillator nonlinearity to local linearization. The design incorporates a low-noise sustaining and buffer amplifier, electrical tuning circuitry, and resonator selection. Phase noise measurements demonstrate a performance of −173dBc/Hz at 1kHz offsets, matching the highest phase noise index currently attainable (NEL's 100 MHz Reference OCXO). Furthermore, the analysis reveals that reducing dominant noise in various frequency bands away from the carrier is an effective strategy for achieving ultra-low phase noise.