Phase characterization of two-tone intermodulation distortion

An automated setup for the characterization of phase asymmetries in nonlinear microwave circuits under two-tone excitation is presented. The method includes a novel approach to generate two synchronized tones with the same amplitude and phase using an arbitrary-waveform signal generator. Special attention is devoted to the evaluation of two-tone IMD impairments as a consequence of memory effects and assesses its dependence on their separation in frequency. Experimental results over a HEMT amplifier exhibiting phase asymmetries are compared with standard two-tone measurements and show that the accuracy of this procedure is good, with negligible non-systematic errors.