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System with automatic compensation for aging and temperature of a crystal oscillator

  • US 5,659,884 A
  • Filed: 02/10/1995
  • Issued: 08/19/1997
  • Est. Priority Date: 02/10/1995
  • Status: Expired due to Fees
First Claim
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1. A radio frequency circuit with compensation for temperature and aging of a crystal oscillator using a reference frequency, comprising:

  • a crystal;

    a tuning device responsive to a frequency correction value for tuning the frequency of oscillation of said crystal to a desired frequency of operation;

    an oscillator circuit connected to said crystal and said tuning device for causing said crystal to oscillate at said radio frequency;

    a temperature sensing device for providing a temperature reading;

    a memory containing a plurality of frequency-temperature correction values and an aging correction value; and

    a controller for reading said temperature reading from said temperature sensing device, for reading said aging correction value from said memory, for reading a said frequency-temperature correction value from said memory for said temperature reading, for combining said aging correction value and said frequency-temperature correction value to provide said frequency correction value, for applying said frequency correction value to said tuning device, for determining a frequency difference between the frequency of said oscillator and said reference frequency, for changing said frequency correction value by a first predetermined amount and providing said frequency correction value to said oscillator if said frequency difference is greater than a first predetermined value, for determining whether said frequency difference is greater than a second predetermined value if said frequency difference is less than said first predetermined value, for changing said frequency correction value by a second predetermined amount and providing said frequency correction value to said oscillator if said frequency difference is greater than said second predetermined value, and for updating said aging correction value in said memory to compensate for said frequency difference if said frequency difference is less than said second predetermined value by determining an updated aging correction value from said frequency correction value and storing said updated aging correction value as said aging correction value.

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