Application of the phase-locked loop to telemetry as a discriminator or tracking filter

This paper studies a system of FM detection suggested by work done in optimum-demodulation theory, and a summary of the problems of ordinary discriminators is made so that possible improvement may be demonstrated readily. This summary points out an important defect of FM discriminators which affects the data accuracy of the telemeter but which is rarely recognized. The system study deals with generalized optimum filtering for transient signals applicable to commutated signals and operators such as discrimination. The solution for particular applications with respect to the phase-locked loop or optimum-demodulation system is offered. With these applications available, noise and transient signals are studied to see how the system fits the practical system. Normalized charts are made which may be applied to any standard telemetering channel that may be designed. A comparison of this system with ordinary discriminators shows a large threshold improvement and a reduction in over-all system error. Graphs of the comparison of these effects are also included. Heuristic suggestions of application are offered for further study.