Formerly, microwave emissions accompanying hypervelocity impacts were confirmed experimentally. In this paper, two kinds of analyses, output waveform analysis and spectral analysis, are discussed for the purpose of clarifying the mechanism of microwave emissions. In output waveform analysis, the microwave pulse is simulated on the basis of a microcrack model in consideration of discharge current, and is compared with the experimental pulse in terms of the pulse shape. In spectral analysis, the amplitude and phase of the waveform is calculated in frequency domain to examine the characteristics of emissions. It is indicated that the spectral amplitude is nearly flat and the phase has coherency.