Ultra-Low Phase Noise 100 MHz Crystal Oscillator

This paper describes an ultra-low phase noise 100 MHz crystal oscillator with a phase noise of around -140 dBc/Hz at a 100 Hz offset. The oscillator includes digitally-controlled phase shifter and attenuator elements, which allow for a flexible approach in the oscillator design and a low residual noise quad parallel differential amplifier. The effect of using an attenuator in the oscillator loop to improve phase noise is also explored.