Ultra Low Phase Noise Microwave Oscillators

This thesis presents the findings of research into low phase noise oscillators. Four design approaches have been developed with the common aim of achieving ultra low phase noise performance. The main body is split into four chapters which detail each design starting with a 1.5 GHz dielectric resonator oscillator, a 16 GHz distributed Bragg resonator oscillator with parallel amplifiers used in the feedback loop, the development of the feedforward technique for use in a low noise oscillator before finishing with the latest measurements of a 5 MHz crystal oscillator.
The development of a 1.5 GHz dielectric resonator oscillator is presented in Chapter 3 which details the design process of each part and the assembly of the complete oscillator in a metal enclosure. The design of the coupling probes, resonator enclosure and the phase shifting circuits are presented. This chapter ends with the presentation and discussion of ultra low oscillator phase noise measurements.
In the fourth chapter the design of the feedback circuit to be used with a 16 GHz distributed Bragg resonator cavity is presented as well as research into the coupling mechanisms used with this resonator. Initial oscillator phase noise measurements are presented.
A new technique is introduced in Chapter 5 using a feedforward amplifier in an oscillator to suppress the flicker noise introduced by the sustaining amplifier. A derivation of design equations are presented as well as measurements of a 100 MHz oscillator showing that a variable gain feedforward amplifier can be used in the feedback loop without the need for external power limiting circuits.
The sixth and final technical chapter presents state of the art measurements of a 5MHz crystal oscillator. This chapter includes the design of an electronic phase shifter as well as measurements of the individual parts of the oscillator.