Non-steady-state photoelectromotive force effect in the presence of periodical and linear phase shift was investigated both theoretically and experimentally. It was shown that superposition of oscillating and linear movements of the interference pattern leads to the appearance of the sharp peak in the frequency dependence of the photoelectromotive force output current when the frequency of periodical modulation matches the frequency of the linear phase shift. We demonstrated experimentally that this effect can be used for determination of a Doppler frequency shift between signal and reference beam.