Operating a Frequency Synthesizer

• US 20130099829A1
• Filed: 10/20/2011
• Published: 04/25/2013
• Est. Priority Date: 10/20/2011
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Renesas Mobile Corporation (Renesas Electronics Corporation)
• Inventors: Xu, Liangge, Kaukovuori, Kristian Jouni, VILANDER, Ari
• Granted Patent: US 8,666,012 B2
• Time in Patent Office: Days
• US Class Current: 327/106
• CPC Class Codes: H03L 2207/50 All digital phase-locked loop
• CPC Class Codes: H03L 7/085 concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal H03L7/10 takes precedence; circuits for comparing the phase or frequency of two mutually-independent oscillations H03D13/00
• CPC Class Codes: H03L 7/087 using at least two phase detectors or a frequency and phase detector in the loop
• CPC Class Codes: H03L 7/113 using frequency discriminator
• CPC Class Codes: H03L 7/16 Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop

Abstract

An apparatus and method for operating a frequency synthesizer wherein a value of an first control signal associated with a fine frequency feedback loop connected to a signal generator is monitored, and a second control signal associated with a medium or coarse frequency feedback loop connected to the signal generator is adjusted based on the monitoring. The first and second control signals are then output to control the frequency synthesizer.

Claims

1. An apparatus comprising:

a controller configured to;

monitor a value of a first control signal associated with a first feedback loop which is connected to a signal generator, the first control signal being indicative of relatively fine frequency adjustments for the signal generator;

based on the monitoring of the first control signal, to adjust a value of a second control signal associated with a second feedback loop connected to the signal generator, the second control signal being indicative of relatively less fine frequency adjustments for the signal generator; and

provide an output signal for controlling a frequency of a signal generated by the signal generator, the output signal being based on the first and second control signals.

2. The apparatus of claim 1, wherein the controller is configured to adjust a value of the first control signal based on the monitoring.

3. The apparatus of claim 2, wherein the controller is configured to adjust values of the first and second control signals such that a change in the frequency of the signal generated by the signal generator associated with the adjustment of the value of the second control signal is compensated, at least partially, by a change in the frequency of the signal generated by the signal generator associated with the adjustment of the value of the first control signal.

4. The apparatus of claim 1, wherein the apparatus comprises a memory configured to store data indicative of one or more values of the second control signal.

5. The apparatus of claim 4, wherein the controller is configured to retrieve data indicative of one of said one or more values of the second control signal from the memory and provide the output signal based on the retrieved data.

6. The apparatus of claim 4, wherein the controller is configured to store data indicative of a value of the second control signal at a first point in time in the memory, and retrieve data indicative of a value of the second control signal at a second point in time from the memory.

7. The apparatus of claim 1, comprising:

a signal generator;

a first feedback loop connected to the signal generator and configured to provide a first control signal indicative of relatively fine frequency adjustments for the signal generator to the controller; and

a second feedback loop connected to the signal generator and configured to provide a second control signal indicative of relatively less fine frequency adjustments for the signal generator to the controller.

8. The apparatus of claim 7, wherein the first feedback loop comprises a fine frequency tuning feedback loop.

9. The apparatus of claim 7, wherein the first feedback loop comprises a phase detector configured to determine a phase difference between an input reference signal and the output of the signal generator.

10. The apparatus of claim 7, wherein the second feedback loop comprises one or more of a coarse frequency calibration feedback loop and at least one medium frequency calibration feedback loop.

11. The apparatus of claim 7, wherein the second feedback loop comprises a counter configured to determine a frequency difference between an input reference signal and the output of the signal generator.

12. The apparatus of claim 1, wherein the first and second control signals comprise digital words.

13. A method comprising:

monitoring a value of a first control signal associated with a first feedback loop which is connected to a signal generator, the first control signal being indicative of relatively fine frequency adjustments for the signal generator;

adjusting, based on the monitoring of the first control signal, a value of a second control signal associated with a second feedback loop connected to the signal generator, the second control signal being indicative of relatively less fine frequency adjustments for the signal generator; and

providing an output signal for controlling a frequency of a signal generated by the signal generator, the output signal being based on the first and second control signals.

14. The method of claim 13, comprising adjusting a value of the first control signal based on the monitoring.

15. The method of claim 14, comprising adjusting values of the first and second control signals such that a change in the frequency of the signal generated by the signal generator associated with the adjustment of the value of the second control signal is compensated, at least partially, by a change in the frequency of the signal generated by the signal generator associated with the adjustment of the value of the first control signal.

16. The method of claim 13, comprising storing data indicative of one or more values of the second control signal in a memory.

17. The method of claim 16, comprising retrieving data indicative of one of said one or more values of the second control signal from the memory and providing the output signal based on the retrieved data.

18. The method of claim 16, comprising storing data indicative of a value of the second control signal at a first point in time in the memory, and retrieving data indicative of a value of the second control signal at a second point in time from the memory.

19. The method of claim 13, comprising determining a phase difference between an input reference signal and the output of the signal generator whereby to generate the first control signal.

20. The method of claim 13, comprising determining a frequency difference between an input reference signal and the output of the signal generator whereby to generate the second control signal.