Oscilloscope based two-port measurement system using error-corrected modulated signals

A technique to accurately measure modulated wideband signals in a two-port context is presented. The technique uses a four channel high frequency digital sampling oscilloscope to perform in-situ correction of both amplitude and phase of the modulated stimulus signal. An advantage of the proposed technique is that no assumption about the group delay has to be made. The technique is demonstrated in a source-pull system. The results clearly demonstrate the necessity of using error-correction in tuner based setups due to the large variations in group-delay over the measurement bandwidth.