Pseudo-random-number-code-detection and tracking system
First Claim
1. A pseudo-random-number code detection and tracking system comprisingmeans for receiving a transmitted coded signal;
- means for generating a local coded feedback signal;
detector means having non-linear response characteristics responsive to said coded received signal and to said local coded signal and including means for comparing said received and local signals to produce an error signal when said received and local signals are not aligned;
means responsive to said error signal for controlling the operation of said local coded feedback signal generating means to vary the characteristics of said local coded feedback signal so as to cause said signals to become aligned and, thereby, to minimize said error signal;
control means, responsive to the statistical characteristics of said error signal, capable of dynamically changing the non-linear response characteristics of said detector means so that said response is substantially linear over a firt selected range of the error signal levels and is substantially constant over a second selected range of error signal levels, whereby said local coded signal and said received coded signal remain substantially aligned over a controllable range of error signal levels; and
wherein said control means includes means for dynamically varying said second selected range.
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Abstract
A pseudo-random-number code detection and tracking system using a closed loop system wherein a detector having a non-linear response characteristic is responsive to a coded received signal and to a locally generated coded signal to produce an error signal. The error is used to control the characteristics of the local signal so as to cause the signals to become aligned. Means are further provided to dynamically control the non-linear response characteristics of the detector so that the coded received signal and coded local signal remain aligned over a controllable range of error signal levels. Thus, a relatively large range can be used during an acquisition operation and a relatively narrower range during the tracking operation.
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Citations
14 Claims
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1. A pseudo-random-number code detection and tracking system comprising
means for receiving a transmitted coded signal; -
means for generating a local coded feedback signal; detector means having non-linear response characteristics responsive to said coded received signal and to said local coded signal and including means for comparing said received and local signals to produce an error signal when said received and local signals are not aligned; means responsive to said error signal for controlling the operation of said local coded feedback signal generating means to vary the characteristics of said local coded feedback signal so as to cause said signals to become aligned and, thereby, to minimize said error signal; control means, responsive to the statistical characteristics of said error signal, capable of dynamically changing the non-linear response characteristics of said detector means so that said response is substantially linear over a firt selected range of the error signal levels and is substantially constant over a second selected range of error signal levels, whereby said local coded signal and said received coded signal remain substantially aligned over a controllable range of error signal levels; and
wherein said control means includes means for dynamically varying said second selected range. - View Dependent Claims (2, 4, 5, 6)
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3. A system in accordance with 2 wherein said digital means includes
means for limiting said error signal; - and
up-down counter means responsive to said limited error signal.
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7. A pseudo-random-number code detection and tracking system comprising
means for receiving a transmitted coded signal; -
means for generating a local coded feedback signal; detector means having non-linear response characteristics responsive to said coded received signal and to said local coded signal, said detector means including shift register means for time shifting said coded feedback signal to provide a first plurality of time-shifted coded feedback signal components advanced in time and a second plurality of timeshifted coded feedback signal components delayed in time; means responsive to said first and second plurality of time-shifted signals components for providing dynamically selective attenuations thereof; and means for combining said selectively attenuated time-shifted signal components to produce said time-shifted coded feedback signals. - View Dependent Claims (8)
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9. A pseudo-random-number code detection and tracking system comprising
means for receiving a transmitted coded signal; -
means for generating a local coded feedback signal; detector means having non-linear response characteristics responsive to said coded received signal and to said local coded signal, said detector means including shift register means for time shifting said coded feedback signal to provide a first plurality of time-shifted coded feedback signal components advanced in time and a second plurality of time-shifted coded feedback signal components delayed in time; means for comparing each of said time-shifted signal components with said received signal to produce a plurality of comparison signal components; means for dynamically controlling the non-linear response characteristics of said detector means including means for controlling the level of each of said comparison signal components in accordance with a selected non-linear response characteristic of said detector means; and means for combining selectively controlled comparison signal components. - View Dependent Claims (10, 11, 12, 13)
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14. A pseudo-random-number code detection and tracking system comprising
means for receiving a transmitted coded signal; -
means for generating a local coded feedback signal; detector means having non-linear response characteristics responsive to said coded received signal and to said local coded signal, said detector means including first and second matched filter means for comparing in parallel a plurality of time-shifted components of the in-phase component and the quadrature component, respectively, of said received signal with a plurality of time-shifted components of the in-phase component and the quadrature component, respectively, of said coded feedback signal to produce a plurality of time-shifted parallel in-phase and quadrature comparison signal components, respectively; first and second means for serially combining said parallel time-shifted in-phase comparison signals and said parallel time-shifted quadrature comparison signals, respectively, to produce a combined serial in-phase comparison signal and a combined serial quadrature comparison signal, respectively; first and second digital recirculating filter means responsive to said combined serial in-phase and quadrature comparison signals, respectively, to produce a filtered combined serial in-phase comparison signal and a filtered combined serial quadrature comparison signal, respectively; first and second means for squaring said combined serial in-phase and quadrature comparison signals, respectively; means for combining said squared combined serial in-phase and quadrature comparison signals to produce a filtered serial comparison signal; means for multiplying said serial comparison signal by serial weight factors selected in accordance with a predetermined non-linear response characteristics of said detector means to produce a weighted serial comparison signal, and means for integrating said weighted serial comparison signal to produce said error signal.
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Specification