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VCXO temperature compensation circuit

  • US 6,559,731 B2
  • Filed: 03/06/2001
  • Issued: 05/06/2003
  • Est. Priority Date: 03/17/2000
  • Status: Expired due to Term
First Claim
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1. A method of controlling the output frequency of a voltage controlled crystal oscillator (VCXO) which is controlled by a VCXO control signal, the method comprising the steps of:

  • (a) during a first period, receiving frequency correction information from a first source, and using this frequency correction information to control the output frequency of the VCXO;

    (b) during the first period, determining a plurality of VCXO compensation values which correspond to respective predefined temperature regions, and which are indicative of a linear relationship between the VCXO control signal and temperature in the region concerned, the step of determining the compensation values during the first period comprising;

    (e) measuring the current temperature;

    (f) determining whether the current temperature corresponds to one of a predetermined set of temperature values, the set of temperature values defining the temperature regions; and

    , if so, (g) storing the current temperature value and a corresponding VCXO control signal;

    (h) determining whether the current temperature value is adjacent in the set of temperature values to a temperature value previously stored in step (g), and, if so, (i) determining the difference between the currently stored VCXO control signal and a VCXO control signal previously stored in step (g); and

    , (j) storing the difference value as the compensation value representing that particular temperature region;

    (c) storing the compensation values; and

    , (d) during a second period when the frequency correction information from the first source is not available, determining the temperature range in which the VCXO is operating and using the corresponding stored compensation value to determine the VCXO control signal, thereby controlling the output frequency of the VCXO.

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