Oscillator Load Pull Measurements Using a Computer Controlled Tuner

The standard " Load Pull Test" provides one of the most important specifications for microwave oscillators, which is the maximum change in frequency and power for a constant VSWR of the load at all phases. The way this method is commonly used however delivers reliable results only for the frequency pulling. In power pulling it bears systematic errors due to the variation of coupling factor of the couplers used to measure the oscillator power with load impedance. A specific Load Pul1 routine, developed using a computerized tuner permits to eliminate this systematic error and delivers more reliable results. The method has been tested on most types of oscillators: DRO, YTO and VCO. Detailed results on the accuracy of the impedance synthesis capability of the tuners are also presented.