Processor for Multiple, Continuous, Spread Spectrum Signals

A circuit is described which accepts the linear sum of several continuous (CW) direct sequence, spread spectrum signals, and outputs a sequence of narrow pulses, each of which contains all the available energy of one of the input signals over some longer predetermined interval of time. The circuit reduces the problem of continuously processing several simultaneous signals to a sequential pulse processing operation, effectively timesharing the same single set of circuitry. Both amplitude and phase information is preserved through the processing technique, allowing implementation in coherent and noncoherent system architectures. In addition to optimum performance and circuit economy, the circuit offers a high degree of design flexibility, particularly in the area of critical timing and interface with digital signal processors. This circuit can be applied directly to a Global Positioning System (GPS) processor. The design of a GPS receiver/processor utilizing this scheme is presented in this paper. Other unique features of the design include using high throughput vector processors to perform rapid doppler frequency search and carrier/code synchronization. A GPS acquisition time which is much shorter than most conventional approaches can then be achieved.