Abstract :
Pulse systems offer the advantage of time-division multiplexing. Synchronous and asynchronous systems are compared and many further methods are mentioned. A novel method of reducing redundancy by functional multiplexing (CODEP) is disclosed. Special signals like synchronization pulses, channel markers, code switching signals, etc., have to be added to the combined pulse train prior to the final carrier modulation process. When comparing the various possible combinations of pulse modulation, multiplexing and carrier modulation to find the most efficient system, the limitations in power radiation have to be considered, average power or peak power limitation being the most usual specifications. Noise and disturbance characterize the transmission medium. Passive and active interceptions may also influence the selection of an optimum system. Passive interceptions include the typical radar reflections, but also ionospheric recording, fault location, etc. Active interceptions comprise all types of repeaters. Regenerative repeating is the most important method for the elimination of cumulative disturbances over long distance communication systems. Important problems arise at the receiver where noise and information carrying signals arrive in a closely mixed form. Apart from special detection methods there are several operations which may be adopted in the frequency domain (comb filter) and time domain (gating, integration, correlation) to improve the separation of signals from noise. Error detection and correction systems, together with prediction methods, may further improve the system quality. Brief reference is made to the various destinations terminating any pulse communication system. Future possibilities are mentioned.
