Spectra of Low-Deviation Frequency-Modulated Waves

For non-Gaussian frequency modulation of a sinusoidal carrier, a general method for the calculation of the spectral density is not available. As has been shown by Blachman, we treat here low-deviation frequency modulation by a general stationary low-pass random process and show that, to first order, the modulated wave has a single-pole spectrum. We also present a higher order estimate for the spectrum, which differs from that of Blachman and appears more satisfactory.