Transmission systems - An introduction to frequency modulation

An account is given of the carrier configurations, capacities and techniques employed in frequency modulation. Attention is given to the derivation of a relationship between the modulation index (which is established by the Bessel functions), deviation, and the modulating frequency. It is possible, on the basis of knowledge of the deviation and the top modulating frequency, to calculate the modulation index. The Bessel functions are then used to determine the sideband frequency pattern produced. A technique known as 'modulation emphasis' is used where the lower channel frequencies are attenuated more than the higher ones.