초록 ▼

A receiver for a direct sequence spread-spectrum communication system of the type in which a transmitter mixes a clocked pseudo-random sequence with a modulated carrier for spreading the carrier energy across a wide band of frequencies, comprises a resident clock-driven pseudo-random code generator

A receiver for a direct sequence spread-spectrum communication system of the type in which a transmitter mixes a clocked pseudo-random sequence with a modulated carrier for spreading the carrier energy across a wide band of frequencies, comprises a resident clock-driven pseudo-random code generator for locally generating an essentially identical, spectrum despreading code sequence; means for clocking the resident code generator at a nominal frequency which is offset in a predetermined sense from the clock frequency of the transmitted code sequence such that the phase of the locally generated code sequence tends to slide in one direction with respect to the phase of the transmitted code sequence; detection means for determining whether the locally generated and the transmitted code sequence are phase aligned or misaligned and for sensing their actual, incipient and/or predicted departures from a phase aligned state, and phase control means for adjusting the clock frequency for the resident code generator whenever such a departure is sensed, thereby shifting the phase of the locally generated code sequence in the opposite direction with respect to the transmitted code sequence by an amount which tends to restore the two code sequences to a phase aligned state.

대표청구항 ▼

A receiver for a direct-sequence spread-spectrum communication system; said system having a transmitter for mixing a predetermined cyclical psuedo-random pulse code sequence with a data modulated carrier signal for spreading said carrier across a substantial frequency spectrum such that said modulat

A receiver for a direct-sequence spread-spectrum communication system; said system having a transmitter for mixing a predetermined cyclical psuedo-random pulse code sequence with a data modulated carrier signal for spreading said carrier across a substantial frequency spectrum such that said modulated carrier is transmitted to said receiver as a spread-spectrum carrier, said predetermined code sequence being stepped through a repetitive phase cycle at a substantially constant clock frequency; said receiver comprising pseudo-random pulse code generator means for locally generating a cyclical pseudo-random pulse code sequence which is essentially identical to said predetermined code sequence; clock means for supplying clock pulses for stepping said locally generated code sequence through a repetitive phase cycle at a nominal frequency which is offset from said constant clock frequency, whereby said locally generated code sequence tends to slide in one direction into and out of phase alignment with respect to said predetermined code sequence; mixer means having one input coupled to said transmitter and another input coupled to said code generator means for mixing and spread-spectrum carrier with said locally generated code sequence, whereby said mixer means recovers a despread carrier signal from said spread-spectrum carrier when said locally generated code sequence is phase aligned with said predetermined code sequence; phase control means coupled between said clock means and said code generator means for regulating the frequency at which said locally generated code sequence is stepped; and circuit means coupled between said mixer means and said phase control code sequence slides into phase alignment with said predetermined code sequence for intermittently triggering said phase control means to phase shift said clock pulses, such that said locally generated code sequence is intermittently phase shifted to counteract its tendency to slide out of phase alignment with said predetermined code sequence, thereby substantially preserving the phase alignment of said locally generated and predetermined code sequences.