Method and apparatus for decoding a phase encoded signal
First Claim
1. A receiver, comprising:
- receiving means;
a correlator coupled to said receiving means, said correlator having a first output comprising a real correlation signal and a second output comprising an imaginary correlation signal;
said real correlation signal comprising a series of bits corresponding to a first correlation value;
said imaginary correlation signal comprising a series of bits corresponding to a second correlation value;
a sector lookup table comprising a plurality of addresses, each of said sector lookup table addresses comprising a plurality of bits corresponding to a portion of said bits of said real correlation signal and a portion of said bits of said imaginary correlation signal, said sector lookup table having an output comprising a phase sector signal; and
a comparator having a first input comprising said phase sector signal and a second input comprising a previous phase sector signal, said comparator having an output comprising a sector difference signal.
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Abstract
An apparatus and method for receiving spread spectrum signals, and, further, for decoding phase encoded information from such signals, requires correlation of input signals into real and imaginary components and determination of the phase angles of the received signal. A transmitter can divide an input signal into a plurality of data streams, independently modulate these streams, and then superpose the plurality of resultants for transmission. A receiver can receive the superposed signal and separate it into real and imaginary parts. In one embodiment, the receiver uses a plurality of spread spectrum codes to generate a plurality of real correlation signals and a plurality of imaginary correlation signals. A transmitter may also generate a differentially phase encoded signal. Phase encoding of a signal generally involves the imposition of known phase changes in the transmitted signal at selected intervals. Decoding of the phase changes at the receiver allows recognition of the phase encoded information. Differential phase encoding, specifically, involves the imposition of a selected phase upon the signal to be transmitted, giving consideration to a prior phase of the signal. In other embodiments, a receiver uses the generated real and imaginary correlation signals to determine a sector of a phase angle of a received signal. This sector can be compared with a previously generated sector, the resultant being an indication of the differential phase encoding performed at the transmitter.
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Citations
14 Claims
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1. A receiver, comprising:
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receiving means; a correlator coupled to said receiving means, said correlator having a first output comprising a real correlation signal and a second output comprising an imaginary correlation signal; said real correlation signal comprising a series of bits corresponding to a first correlation value; said imaginary correlation signal comprising a series of bits corresponding to a second correlation value; a sector lookup table comprising a plurality of addresses, each of said sector lookup table addresses comprising a plurality of bits corresponding to a portion of said bits of said real correlation signal and a portion of said bits of said imaginary correlation signal, said sector lookup table having an output comprising a phase sector signal; and a comparator having a first input comprising said phase sector signal and a second input comprising a previous phase sector signal, said comparator having an output comprising a sector difference signal. - View Dependent Claims (2, 3, 4, 5)
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6. A method for receiving, comprising the steps of:
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receiving an input; correlating said input to produce a real correlation signal and an imaginary correlation signal, said real correlation signal comprised of a series of bits corresponding to a first correlation value and said imaginary correlation signal comprised of a series of bits corresponding to a second correlation value; forming an address from a plurality of bits, said plurality of bits corresponding to a portion of said bits of said real correlation signal and a portion of said bits of said imaginary correlation signal; applying said address to a sector lookup table to retrieve a sector value therefrom; and comparing said sector value with a previous sector value to produce a sector difference signal. - View Dependent Claims (7, 8, 9, 10)
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11. A receiver, comprising:
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receiving means; a plurality of correlators coupled to said receiving means, each correlator having a first output comprising a real correlation signal, a second output comprising an imaginary correlation signal, and a third output comprising a unified correlation signal; a Best-of-M detector having as inputs said unified correlation signal from each of said plurality of correlators, said Best-of-M detector having an output comprising a selection signal; a real correlation signal multiplexor having as inputs said real correlation signal from each of said plurality of correlators and said selection signal from said Best-of-M detector, said real correlation signal multiplexor having an output comprising a selected real correlation signal, said selected real correlation signal comprising a series of bits corresponding to a real correlation value; an imaginary correlation signal multiplexor having as inputs said imaginary correlation signal from each of said plurality of correlators and said selection signal from said Best-of-M detector, said imaginary correlation signal multiplexor having an output comprising a selected imaginary correlation signal, said selected imaginary correlation signal comprising a series of bits corresponding to an imaginary correlation value; and a sector lookup table comprising a plurality of addresses, each said sector lookup table address comprising a plurality of bits corresponding to a portion of said bits of said selected real correlation signal and a portion of said bits of said selected imaginary correlation signal, said sector lookup table having an output comprising a phase sector signal. - View Dependent Claims (12)
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13. A method for receiving, comprising the steps of:
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receiving an input; correlating said input with a plurality of spread spectrum codes to produce a plurality of real correlation signals, a plurality of imaginary correlation signals, and a plurality of unified correlation signals; determining a unified correlation signal representing a highest degree of correlation; selecting a real correlation signal corresponding to said determined unified correlation signal, said selected real correlation signal comprising a series of bits corresponding to a real correlation value; selecting an imaginary correlation signal corresponding to said determined unified correlation signal, said selected imaginary correlation signal comprising a series of bits corresponding to an imaginary correlation value; forming an address from a plurality of bits comprising a portion of said bits of said selected real correlation signal and a portion of said bits of said selected imaginary correlation signal; and applying said address to a sector lookup table to retrieve a sector value therefrom. - View Dependent Claims (14)
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Specification