Self-calibrating frequency standard system

• US 5,697,082 A
• Filed: 09/08/1995
• Issued: 12/09/1997
• Est. Priority Date: 10/01/1993
• Status: Expired due to Fees

• Current Assignee: Rockwell International Corporation
• Original Assignee: Rockwell International Corporation
• Inventors: El-Ghoroury, Hussein S., Greer, Steven Craig
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Corrielus, Jean B.
• Application Number:
  US08/525,111
• Time in Patent Office: 823 Days
• Field of Search: 375/358, 375/359, 375/357, 455/13.2, 455/51.1, 455/255, 455/256, 455/257, 455/258, 455/259, 331/44, 331/47, 368/47, 368/184
• US Class Current: 455/255
• CPC Class Codes: G04G 7/00 Synchronisation radio-controlled time-pieces G04R
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation

Abstract

A system for self-calibrating a clock of a communication terminal for use with communication systems in which a central communication node generates time base correction signals for the terminal clock includes a terminal oscillator which generates an oscillator frequency that includes an error amount. An oscillator calibration filter generates a frequency error estimate amount. Circuitry is provided for subtracting the frequency error estimate amount generated by the calibration filter from the oscillator frequency error amount. Circuitry is provided for applying the time base correction signals to the calibration filter to thereby modify the frequency error estimate amount generated by the calibration filter based upon the time base correction signals generated by the communication central node.

Claims

1. A system for self-calibrating a communication terminal oscillator for use with a satellite, the satellite generating time base correction signals for the communication terminal oscillator, the communication terminal oscillator generating an oscillator frequency that includes an unknown error amount, the system comprising:

a Kalman filter for generating a frequency error estimate amount;

means for subtracting said frequency error estimate amount from the oscillator frequency;

means for applying the satellite time base correction signals to said Kalman filter to change said frequency error estimate amount generated by said Kalman filter based upon the satellite time base correction signals; and

said means for applying the satellite time base correction signals to said Kalman filter includes;

means for converting said Kalman filter frequency error estimate amount to a Kalman filter time error estimate amount; and

means for changing said Kalman filter time error estimate amount based on the satellite generated time base correction signals to generate a changed time error input amount to said Kalman filter.

2. A system for self-calibrating a communication terminal oscillator for use with a satellite, the satellite generating time base correction signals for the communication terminal oscillator, the communication terminal oscillator generating an oscillator frequency that includes an unknown error amount, the system comprising:

means for converting the oscillator frequency to a terminal time amount for controlling an up-link signal for transmission from the terminal to the satellite;

means for changing said terminal time amount based on the satellite generated time based correction signals;

a Kalman filter for generating a frequency error estimate amount;

means for subtracting said frequency error estimate amount from the oscillator frequency;

means for applying the satellite time base correction signals to said Kalman filter to change said frequency error estimate amount generated by said Kalman filter based upon the satellite time base correction signals; and

said means for applying the satellite time base correction signals to said Kalman filter includes;

means for converting said Kalman filter frequency error estimate amount to a Kalman filter time error estimate amount; and

means for changing said Kalman filter time error estimate amount based on the satellite generated time base correction signals to generate a changed time error input amount to said Kalman filter.

3. A system for self-calibrating a communication terminal oscillator for use in communication systems in which a central communication node generates time base correction signals for the terminal oscillator, the terminal oscillator generating an oscillator frequency that includes an unknown error amount, the system comprising:

an oscillator calibration filter for generating a frequency error estimate amount;

means for subtracting said frequency error estimate amount from the oscillator frequency;

means for applying the central communication node time base correction signals to said oscillator calibration filter to change said frequency error estimate amount generated by said oscillator calibration filter based upon the central communication node time base correction signals; and

said means for applying the central communication node time base correction signals to said oscillator calibration filter includes;

means for converting said oscillator calibration filter frequency error estimate amount to an oscillator calibration filter time error estimate amount; and

means for changing said oscillator calibration filter time error estimate amount based on the central communication node generated time base correction signals to generate a changed time error input amount to said oscillator calibration filter.

4. The system of claim 3 and further including:

means for converting the oscillator frequency to a terminal time based amount for controlling the signal for transmission from the terminal to the central communication node; and

means for changing said terminal time based amount based on the central communication node generated time based correction signals.

5. The system of claim 3 wherein said oscillator calibration filter includes a Kalman filter.