Phase transient response measurements using automatic frequency estimation

A method of measuring the phase transient response of a device under test automatically provides a flattened phase transient response without any user intervention. The method comprises the steps of calculating an instantaneous phase waveform based on an instantaneous voltage waveform that represents an output signal of the device under test as it steps from a first frequency to a second frequency, calculating an instantaneous frequency waveform based on the instantaneous phase waveform, automatically estimating the second frequency based on the instantaneous frequency waveform without any user intervention, and flattening the instantaneous phase waveform based on the estimate of the second frequency.