Performance comparison of λg/2 and ring resonator based oscillators

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, smaller size and lower cost. In this paper, two negative resistance oscillators are discussed using different micro strip resonators. First oscillator is designed using λg/2 resonator. Oscillator has measured output power of 4.4 dBm at carrier frequency of 3.7 GHz with phase noise of -44.01dBc/Hz at offset of 100 KHz. Second oscillator is designed using circular ring resonator. This circuit has measured output power of 1.1dBm at carrier frequency of 3.89 GHz with phase noise of -46.24dBc/Hz at offset of 100 KHz. In both cases, 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. A comparison of general characteristics of above mentioned oscillators is presented in this paper.