Pseudo noise code and data transmission method and apparatus

摘要

Pseudo noise ranging codes, having a predetermined chipping rate, and a pair of binary data sources, each having a bit rate no greater than one tenth the chipping rate, quadriphase, digitally modulate a suppressed carrier wave having a first frequency. Two additional binary data sources, each having a bit rate that is not restricted by the chipping rate of the first carrier, quadriphase, digitally modulate a suppressed carrier wave having a second frequency. The first and second frequencies are only slightly displaced so that there is overlap in the frequency bands which modulate the two carriers. The two suppressed carrier waves are linearly combined and transmitted from a first station to a second station so that the amplitude of the transmitted first wave is controlled so as not to degrade the detectability of the second wave at the second station. At the second station, the information modulated on the second carrier is coherently detected to recover the two signals modulated on the second carrier. The binary signals modulated on the first carrier are recovered by a pair of matched filters at the second station; the filters respectively include means for deriving the pseudo noise codes transmitted from the first station. The two pseudo noise codes derived at the second station are mixed with the received signal to increase the amplitudes of the two data sources modulating the first wave above the amplitude of the second wave.