Coherent multi-tone stimulus-response measurements with a VNA

Fast spectrum analysis in FFT mode is simultaneously performed with a modern VNA at the input and output ports of a DUT. The stimulus signal is a wideband repetitive multi-tone. The Spectrum Analyzer coherent mode of the VNA takes into account the repetition rate of the test signal. It adjusts its Fourier transform grid to match the stimulus tones. This coherent mode allows deterministic image rejection. The consequence is faster and more accurate multi tones measurements. Practical examples of NPR and ACPR measurements are given.