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Method and apparatus for determining the frequency of a radio signal during periods of stability and monitoring communications with a radio receiver

  • US 7,046,964 B1
  • Filed: 12/06/2004
  • Issued: 05/16/2006
  • Est. Priority Date: 05/21/2001
  • Status: Expired due to Term
First Claim
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1. A method of determining stability of frequency and frequency of a frequency-stable electrical signal, the method comprising:

  • counting amplitude transitions of an electrical signal during a primary sampling period;

    counting the amplitude transitions of the electrical signal during each of at least two secondary sampling periods, wherein the secondary sampling periods are shorter than the primary sampling period and at least one of the secondary sampling periods partially overlaps, in time, the primary sampling period;

    comparing counts of the amplitude transitions of two of the secondary sampling periods to each other to produce a difference;

    comparing the difference to a threshold and determining that the frequency of the electrical signal is unstable if the difference exceeds the threshold; and

    if the difference does not exceed the threshold, determining the frequency of the electrical signal from an accumulated count of the amplitude transitions accumulated during the primary sampling period.

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