Numerical calculation of spectra for digital FM signals

Two methods for calculating digital FM spectra are outlined. One of them, which is quite general, yields power spectra with very high accuracy, even when the spectrum is small, that is, less than -100 dB. The calculations that must be performed, however, are extensive. The other method can be used for modulation indices of the order h = 1/2, 3/2, etc. and is extremely rapid. A powerful tool for studying the effect of changing different parameters in a digital FM scheme is thus obtained. The result is of only limited accuracy (greater than approximately -80 dB). The power spectra for digital FM schemes are shown.