Communications system using time position modulation and correlation slope demodulation

摘要

An angle modulation radio communications system having privacy and security characteristics. The system utilizes two or more communication units, one at the transmitting terminal and the other at the receiving terminal of identical functional construction and each having a transceiver module, an antenna and a phase reversal modulator-demodulator module between the transceiver module and the antenna. Complex phase reversal modulation of the transmitted carrier is accomplished which produces a constant amplitude spread spectrum frequency-modulated carrier from which the modulation is not recoverable without a proper code in an autocorrelation process. The modulator-correlator module is bidirectional in operation, and because of its interposition between the antenna and the receiver module, the modulator-correlator spreads the spectrum of any electromagnetic wave signals supplied by it to the transmitting antenna and also spreads the spectrum of any signals received by the antenna not included in accordance with the proper code. Therefore, the units of the system present a very high degree of signal frequency selectivity and rejection of any electromagnetic wave radiation not having the proper code. Pseudo-random code phase reversal modulation suppresses the carrier and the intelligence signal power is in the form of frequency perturbations of the pseudo noise code modulation.