Apparatus and method for stabilized phase detection for binary signal tracking loops
First Claim
1. A stabilized phase detector for a signal tracking loop to track an incoming signal in the presence of gain level changes and imbalance using two local reference signals, comprising:
- (a) mixer means for multiplying the incoming signal with the two local reference signals to form first and second product signals;
(b) first bandpass detector means for forming an error signal from the first product signal for tracking the incoming signal;
(c) second bandpass detector means for forming an error signal from the second product signal for tracking the incoming signal;
(d) means for forming a composite error signal from the error signals from said first and second bandpass detector means; and
(e) switching means comprising;
(1) first switching means for alternately interconnecting the two local reference signals to said mixer means; and
(2) second switching means for alternately interconnecting the error signals from said first and second bandpass detector means to said means for forming to thereby compensate for gain imbalance and level drift in said bandpass detector means.
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Abstract
A new and improved apparatus and method for phase detection in binary signal tracking loops wherein two bandpass detectors are alternately interchanged between electrical connection with two local code reference tracking signals in order to cancel any adverse effect of gain imbalance in the bandpass detectors and direct current offset or drift. The incoming signal is multiplied with the two local reference signals in a mixer circuit to form first and second product signals which are each separately provided to two bandpass detectors to form error signals. A dither generator controls a first switching circuit to alternately interconnect the two local reference signals to the mixer circuit during the step of multiplying and also controls a second switching circuit to alternately interconnect the error signals to a summing circuit to form a composite error signal representing a difference in levels of the two error signals from the detectors. The detectors are thus time shared in multiplex fashion between the two local reference signals.
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Citations
17 Claims
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1. A stabilized phase detector for a signal tracking loop to track an incoming signal in the presence of gain level changes and imbalance using two local reference signals, comprising:
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(a) mixer means for multiplying the incoming signal with the two local reference signals to form first and second product signals; (b) first bandpass detector means for forming an error signal from the first product signal for tracking the incoming signal; (c) second bandpass detector means for forming an error signal from the second product signal for tracking the incoming signal; (d) means for forming a composite error signal from the error signals from said first and second bandpass detector means; and (e) switching means comprising; (1) first switching means for alternately interconnecting the two local reference signals to said mixer means; and (2) second switching means for alternately interconnecting the error signals from said first and second bandpass detector means to said means for forming to thereby compensate for gain imbalance and level drift in said bandpass detector means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of phase detection with bandpass detector means to track an incoming signal in the presence of gain level changes and imbalance using two local reference signals, comprising the steps of:
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(a) multiplying the incoming signal with the two local reference signals in two mixers to form first and second product signals; (b) forming a first error signal from the first product signal for tracking the incoming signal; (c) forming a second error signal from the second product signal for tracking the incoming signal; (d) forming a composite error signal from the error signals by; (1) alternately interconnecting the two local reference signals to the two mixers during said step of multiplying to thereby multiplex the two local reference signals in the first and second product signals; and (2) alternately interconnecting the first and second error signals to thereby demultiplex same and thereby compensate for gain imbalance and level drift in said bandpass detector means. - View Dependent Claims (14, 15, 16, 17)
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Specification