Frequency Modulation Error Calculation

Abstract

In a frequency modulation process, small amplitude sidebands near the deviation limits are sometimes distorted or lost. The problems and expense of preserving these lessor sidebands are often great, and spectrum space must be reserved for them. To date there appears to have been no clear statement of their importance in terms of data accuracy. This paper presents a numerical calculation of the errors accrued in a demodulated signal after truncation of the FM spectrum obtained with sinusoidal modulation. It is shown that the error increases for decreasing bandwidth. Error is evaluated for several bandwidths, and relationships to power outside the band are noted. Applications include specification of bandwidth for a given error in demodulated signal. The use of a limiter is assumed.