Simple and Accurate Measurement of Loaded Q Factor of Microwave Oscillators using Thermal Noise Injection

A new measurement method to determine the loaded Q factor of microwave oscillators is described. Thermal noise power is injected into the test oscillator and single sideband phase noise is measured simultaneously. The resulting phase noise plot contains all information which is needed to determine the loaded Q in a very simple manner. The test oscillator can be considered as a black box. In the paper a detailed comparision is drawn with the injection locking method and the load pulling method.