Technique for measuring phase accuracy and amplitude profile of continuous-phase modulated signals

A method and apparatus for determining the phase and amplitude accuracy of continuous-phase-modulated signals is described. The modulated RF signal generated by the transmitter unit under test is down-converted to a relatively low intermediate frequency which is filtered and sampled by a high sampling rate analog-to-digital converter. A digital signal processor processes the digital signals to produce measured amplitude and phase functions of the modulated transmitter signal. From the measured values of amplitude and phase, ideal amplitude and phase functions of the transmitter signal are synthesized mathematically. The synthesized functions are compared to the measured functions to determine instantaneous amplitude and phase errors as a function of time