Абстракт
The structure of a signal reflected from a vibrating surface is studied in the case when the vibration amplitude is comparable to or significantly greater than the wavelength of the probing electromagnetic wave. It is shown that the
relations between the amplitudes of the highest harmonics makes it possible to calculate the vibration amplitude in situations when it is longer than the probe wavelength. Criteria are obtained that make it possible to choose the
harmonics of the reflected signal to uniquely determine the vibration amplitude. It is shown that the effect of energy redistribution between a large number of harmonics of the reflected signal, which occurs with an increasing phase
modulation index, leads to a decrease in their amplitude by about 1.75.