Reference oscillator

• US 7,098,749 B2
• Filed: 07/28/2005
• Issued: 08/29/2006
• Est. Priority Date: 05/16/2001
• Status: Expired due to Fees

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Wireless Corporation (Kyocera Corporation)
• Inventors: Forrester, Tim
• Primary Examiner(s): KINKEAD, ARNOLD M
• Application Number:
  US11/193,593
• Publication Number:
  US 20050264370A1
• Time in Patent Office: 397 Days
• Field of Search: 331/176, 331/66, 331/16, 331/1.R, 331/18, 331/158
• US Class Current: 331/176
• CPC Class Codes: H03J 1/0008 using a central processing unit, e.g. a microprocessor digital tuning in general H03J5/0245
• CPC Class Codes: H03J 7/04 where the frequency control is accomplished by varying the electrical characteristics of a non-mechanically adjustable element or where the nature of the frequency controlling element is not significant
• CPC Class Codes: H03L 1/026 by using a memory for digitally storing correction values H03L1/025 takes precedence

Abstract

A receiver uses an adaptive algorithm to tune a low-cost crystal oscillator according to a temperature compensation profile so as to produce a precision master reference frequency despite temperature, initial tolerance, and aging effects. An automatic frequency control system also tunes the crystal oscillator. The adaptive algorithm adjusts the temperature compensation profile for the crystal oscillator according to the adjustments made by the automatic frequency control should a received signal'"'"'s quality factor exceed that associated with the temperature compensation profile.

Claims

1. A method of providing a reference frequency signal, comprising:

storing temperature correction information for a reference oscillator;

associating and storing a stored quality factor in association with the stored temperature correction information;

receiving current temperature data;

generating a current correction signal by correlating the current temperature data with the stored temperature correction information;

tuning the reference oscillator using the current correction signal, the reference oscillator outputting the reference frequency signal;

determining a frequency offset in the reference frequency signal;

generating updated temperature correction information based on the frequency offset;

receiving a signal and associating a received signal quality factor for the received signal;

comparing the received signal quality factor with the stored quality factor; and

modifying the stored temperature correction information responsive to the comparing step.

2. The method according to claim 1, further comprising storing the updated temperature correction information.

3. The method according to claim 2, wherein the updated temperature correction information is stored only if the received signal quality factor exceeds the stored quality factor.

4. The method according to claim 3, wherein the stored quality factor is reduced proportionally to the passage of time.

5. The method according to claim 1, wherein the received signal quality factor is determined by the carrier-to-noise ratio of the received signal.

6. The method according to claim 2, further comprising determining whether the received signal is a valid signal;

and

wherein the updated temperature correction information is only stored if the received signal is a valid signal.

7. The method according to claim 6, wherein the received signal is determined to be a valid signal if it is a pilot signal of a base station.

8. The method according to claim 1, further comprising:

receiving a strong signal;

determining an initial frequency offset in the reference frequency signal based on the strong signal; and

calibrating initial temperature correction information based on the initial frequency offset.

9. A circuit for generating a reference frequency signal in a wireless communication device comprising:

a reference oscillator;

a memory configured to store temperature correction information for the reference oscillator, the memory further configured to store a stored quality factor associated with the stored temperature correction information;

logic circuitry coupled to the reference oscillator and configured to receive current temperature data and generate a current correction signal by correlating the current temperature data with the stored temperature correction information, wherein the reference oscillator is tuned using the current correction signal and outputs the reference frequency signal; and

a computational engine including an adaptive algorithm executed by the logic circuitry, the adaptive algorithm configured to determine a frequency offset in the reference frequency signal and generate updated temperature correction information based on the frequency offset;

wherein the adaptive algorithm is further configured to receive a signal and associating a received signal quality factor for the received signal, compare the received signal quality factor with the stored quality factor, and modify the stored temperature correction information responsive to the comparison.

10. The device according to claim 9, wherein the memory is further configured to store the updated temperature correction information.

11. The device according to claim 10, wherein the updated temperature correction information is stored only if the received signal quality factor exceeds the stored quality factor.