Microwave oscillator design is based on the principle of generating a negative resistance to
compensate for the losses of the resonator. Several circuit combinations, including one- and two port
oscillators, are possible. In this discussion, we will first evaluate the conditions of oscillation or the Colpitts and Clapp-Gouriet oscillator. We will then evaluate a 19-GHz SiGe-based oscillator by assuming values, backed up by available S parameters and dc I-V curves, that we assigned to the nonlinear BFP520 model. So far it has been difficult to obtain completedocumentation on modeling for the SiGe transistors, but our approximation appears to be justified. Next, we will evaluate a ceramic-resonator-based oscillator and show its performance.Going up to higher frequencies, we will introduce a 47-GHz lumped-resonator oscillator and a VCO at the same frequency that uses GaAsFETs as varactors. In all cases, we will give athorough treatment of the circuits and their performance.