Wideband high dynamic range distortion measurement

This paper presents an intermodulation distortion measurement system based on automated feedfoward cancellation that achieves 95 dB of broadband dynamic range. A single tone cancellation formula is developed requiring only the power of the probing signal and the power of the combined probe and cancellation signal to predict the required phase shift for cancellation. This formula is applied to a two path feedfoward cancellation system, combined with the DUT probe path in a bridge configuration. The dynamic range and cancellation capabilities of this system are confirmed by measuring the passive intermodulation distortion generated by a low PIM microwave chip termination. The cancellation method extends the intermodulation distortion measurement dynamic range by at least 20 dB.