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Lock detector for feedback loops

  • US 4,860,321 A
  • Filed: 09/13/1985
  • Issued: 08/22/1989
  • Est. Priority Date: 09/13/1985
  • Status: Expired due to Term
First Claim
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1. A receiver employing matched filter detection of signals modulated with data symbols having a data symbol period, comprising:

  • means for matched filter detection and coherent demodulation of said signal, said means comprising a phase lock loop for tracking the phase of said signal;

    means for providing an estimate of the signal amplitude;

    means for calculating a lock detector statistic value, said value being normalized by an estimate of the signal amplitude to reduce its sensitivity to variations in the signal amplitude;

    testing means responsive to said lock detector statistic value for determining whether said loop is tracking said signal at a false frequency or time offset, said means being operable over a wide signal to noise ratio (SNR) range over the entire frequency bandwidth at the input to said matched filter detection means and over the entire data symbol period; and

    means responsive to said testing means for providing an indicator that the receiver is tracking at a false frequency or time estimate.

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