PERFORMANCE COMPARISON OF AND RING RESONATOR BASED OSCILLATORS

Abstract

Transistor oscillators with planar micro strip resonators as frequency determining elements are widely used as stable sources for microwave systems because of their easier implementation and lower cost. This thesis is concerned with the development of oscillators using different micro strip resonators. Two negative resistance oscillators are designed and implemented. First oscillator is designed using λg/2 resonator. Short circuited stubs at source are used for the purpose of device instability. Short circuited stubs also induce instability at other undesired frequencies which causes wideband oscillations. The problem of wideband instability is solved by removing the short circuited stubs at source and directly grounding the device. Oscillator has measured output power of 4 dbm at carrier frequency of 3.72 GHz with phase noise of -40dBc/Hz at offset of 100 KHz. In this case, resonator is over coupled, in order to select optimum terminating impedance point in unstable region of device, which causes reduction of Quality factor of resonator. Second oscillator is designed using circular ring resonator. Device is directly grounded and over coupled circular ring resonator is used. Resonator is over coupled in order to select optimum terminating impedance in unstable region of device. This circuit has measured output power of 1.1dBm at carrier frequency of 3.89 GHz with phase noise of -45dBc/Hz at offset of 100 KHz. A comparison of general characteristics of above mentioned oscillators will be presented in this work.