Spread spectrum adaptive code tracker
First Claim
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1. Apparatus including correlators for acquiring and tracking a spread spectrum signal having a predetermined spread spectrum code so as to suppress noise in correlators not containing the signal comprising:
- means for receiving said spread spectrum signal;
a set of prime correlators each defining a correlator channel and each having two inputs, one input thereof coupled to said receiving means such that said prime correlators are connected in parallel thereto;
means for supplying a set of phase delayed replicas of said code to the other inputs of said prime correlators;
means for ascertaining the degree of correlation in each of said prime correlators and for generating an adaptive correlation channel weight which rises with increasing correlation and decreases with decreasing correlation in the corresponding channel thus to provide continuously variable weights;
means for multiplying the output of each prime correlator with the corresponding adaptively generated weight;
means coupled to the outputs of said multipliers for developing an error signal;
means for applying said error signal to said means for ascertaining the degree of correlation in each of said prime correlators such that said weight rises and decreases can be generated; and
means for identifying by the channel weights which correlation channel is the most likely to have an associated replica in-phase with said spread spectrum code.
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Abstract
A pseudo-noise code-tracking spread spectrum receiver able to quickly acquire and track incoming signals includes an adaptive weighting system for the outputs of parallel-fed correlator channels in which the weighting system automatically detects the degree of correlation in each channel, sets the detector characteristic to increase the weight for a correlator channel exhibiting a high degree of correlation, and decreases to zero the weights on all others.
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11 Claims
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1. Apparatus including correlators for acquiring and tracking a spread spectrum signal having a predetermined spread spectrum code so as to suppress noise in correlators not containing the signal comprising:
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means for receiving said spread spectrum signal; a set of prime correlators each defining a correlator channel and each having two inputs, one input thereof coupled to said receiving means such that said prime correlators are connected in parallel thereto; means for supplying a set of phase delayed replicas of said code to the other inputs of said prime correlators; means for ascertaining the degree of correlation in each of said prime correlators and for generating an adaptive correlation channel weight which rises with increasing correlation and decreases with decreasing correlation in the corresponding channel thus to provide continuously variable weights; means for multiplying the output of each prime correlator with the corresponding adaptively generated weight; means coupled to the outputs of said multipliers for developing an error signal; means for applying said error signal to said means for ascertaining the degree of correlation in each of said prime correlators such that said weight rises and decreases can be generated; and means for identifying by the channel weights which correlation channel is the most likely to have an associated replica in-phase with said spread spectrum code. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for decreasing the signal acquisition and tracking time for parallel correlator spread spectrum receivers comprising the steps of ascertaining the degree of correlation for each of said correlators and thus the degree of correlation for the associated correlator channel, generating a weight directly proportional to the degree of correlation in the corresponding channel, said weight being continuously variable, and multiplying this output of each of said correlators with the corresponding generated weight, whereby said parallel correlator spread spectrum receivers are provided with adaptive continuously variable weights which narrow the receiver response upon an initial in-phase correlation in any one of said channels, thereby to suppress noise in correlators not containing the signal.
Specification