RF Bandwidth of Frequency-Division Multiplex Systems Using Frequency Modulation

The radio-frequency energy distribution of a Frequency-Division-Multiplex, Frequency-Modulated Multichannel telephony system is evaluated. An estimate is obtained of the intermodulation noise generated when this spectrum is passed through an "ideal" bandpass filter with very sharp cutoff. From this it is possible to specify the minmum bandwidth of such a filter in terms of required system performance. This result provides a useful guide to the bandwidth over which control of group-delay and attenuation is necessary.