Relation between power spectrum and phase spectrum of oscillators

The single-sideband to carrier power ratio L(f) and the phase fluctuations spectral density S¿¿(f) are two convenient means of characterising the spectral purity of oscillators, and, for low-modulation indices, numerically S¿¿ = 2L, the letter briefly reviews the fundamental concepts and extends the above relationship to any modulation depth. Theoretical results for frequency modulation by bandlimited white Gaussian noise are presented. Computations are discussed and dimensional aspects have been checked experimentally.