Ultra-low phase noise 100 MHz crystal oscillator & residual phase noise measurement systems

In this thesis, an ultra-low phase noise 100 MHz crystal oscillator is presented that demonstrates a phase noise of around -140 dBc/Hz at a 100 Hz offset. The architecture and each of its constituent components are described in detail. The oscillator performance was measured for three separate amplifier designs, including a differential amplifier in a quad parallel configuration. A method for measuring the flicker noise corner of the amplifiers using an LC resonator is also described and it is shown how the placement of an attenuator between the resonator and the input of the amplifier in an oscillator loop can be used as a simple way to reduce phase noise degradation in certain circumstances.

A set of digitally-controlled phase shifter and attenuator devices are presented that are designed to be used in the 100 MHz crystal oscillator and other applications. These are passive devices that utilise mechanical RF relays to switch in microstrip delay line elements in the case of the phase shifter, and resistive attenuator networks in the case of the attenuator, to minimise flicker noise. The complete design procedures for producing these devices are described in detail.

Finally, a low-cost residual phase noise measurement system is described that uses cross-correlation techniques to reduce the internal system noise floor. The system is designed primarily for characterising the residual phase noise performance of low power amplifiers operating at 100 MHz and exhibits a noise floor of -177 dBc/Hz when measuring a device operating at 0 dBm. A set of efficient digital signal processing algorithms is also presented, which includes the ability to vary the resolution bandwidth for different frequency bands in a single measurement.