Interchannel Interference Due to Klystron Pulling

In a recent paper 1 the problem of interchannel interference produced by echoes in an FM system was treated. The mathematical development in that paper can be used to calculate the distortion that arises when a Klystron oscillator is connected to an antenna through a transmission line of appreciable length. In the system we study, the composite signal wave (the "baseband signal") from a group of carrier telephone channels in frequency division multiplex is applied to the repeller of a Klystron and thereby modulates the frequency of the Klystron output wave. If the antenna does not match the transmission line perfectly, the output frequency is altered slightly by an amount proportional to the mismatch. This effect, known as "pulling," results in intermodulation between the individual telephone channels. In this study, the composite signal will be simulated by a random noise signal of appropriate bandwidth and power. It is assumed that some particular message channel is idle; i.e., there is no noise energy in the corresponding frequency band (which is relatively narrow in comparison with the bandwidth of the composite signal). If the system were perfect, no power would be received in this idle channel at the output of the FM detector. In the following work, the intermodulation noise falling into this channel because of the "pulling effect" will be computed. This leads to "Lewin's integral," so called, which is tabulated herein.