Analysis of Multiplex Error in FM/FM and PAM/FM/FM Telemetry

The primary object of the work described in this paper is to establish and delineate a procedure for the calculation of certain errors associated with the performance of FM/FM and/or PAM/FM/FM multiplex telemetry systems. The errors considered are those that are produced in a channel of the multiplex resulting from arbitrary frequency and phase selective networks, and those resulting from the interference of adjacent channel sidebands with respect to an arbitrary channel center frequency separation. To find these errors, a straightforward spectral analysis and synthesis is developed for practical models of standard FM/FM and PAM/FM/FM systems. Expressions are obtained for the outputs of a multiplex for given inputs, and for non-linear distortion and adjacent channel interference, in terms of the conventional parameters of such systems. This method of analysis is entirely quantitative, and an effort has been made to develop it from a definite theoretical basis. Because the FM process is nonlinear, and since the purpose of this investigation has been the evaluation of system performance rather than analytical insight per se, automatic digital computation is contemplated throughout. Nevertheless, it has been found that the results of the work involved in 1) the justification of a system model, 2) the derivations of functions defining the operations of the components of the model, 3) programming the functions for numerical analysis, and finally 4) performing relatively economical experimental numerical adjustments of the model parameters, lead to a valuable physical appreciation of the system behavior with respect to prescribed conditions.