On the Load-Pull Effect in MMIC Oscillator Measurements

Low phase-noise MMIC oscillators are key components for microwave and mm-wave systems. As a consequence, phase-noise measurements of these circuits have become a subject of growing interest and importance. This paper demonstrates that MMIC oscillator circuits with their relatively low Q factors are prone to specific measurement errors. Caused by a load-pull effect, the measurement system can become part of the oscillator, which yields phase-noise data significantly below reality. Special care has to be taken in order to avoid such phenomena.