Though microwave emissions in association with hypervelocity impacts have been confirmed experimentally, the emission characteristics and the emission mechanism have not yet been made clear. For example, whether the emission is noise or a coherent signal is not known. In this paper, two kinds of analyses, output waveform analysis and spectral analysis, are discussed. Regarding output waveform analysis, microwave pulses are simulated on the basis of a microcrack model in consideration of discharge current, and are compared with experimental pulses in terms of the pulse shape and width. Regarding spectral analysis, the intensity and phase of waveforms are calculated in the frequency domain to examine the frequency characteristics. The spectral intensity is nearly flat and the phase has coherency. Accordingly, the microwave emission is not noise but a sequence of independent pulses.