Calculating digital FM spectra by means of autocorrelation

It is noted that in sharp contrast to the task of calculating the power spectrum for a general digital FM scheme, the autocorrelation can easily be obtained. By considering a class of FM schemes having a time-limited autocorrelation function, truncation is avoided, and by applying a Fourier transformation, power spectral densities are easily obtained. A method is applied that takes these properties into account. A powerful tool is thus available for investigating different parameters within the considered digital FM modulation format. Inherent in the developed method is that only specific modulation indexes can be used and that numerical noise occurs. This is thought to be of minor importance since attractive schemes can be identified for further processing.