Method and system for automatic gain control during signal acquisition

• US 20070232251A1
• Filed: 04/03/2006
• Published: 10/04/2007
• Est. Priority Date: 04/03/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Krishnamoorthi, Raghuraman, Li, Linbo, Murthy, Vinay
• Granted Patent: US 7,702,046 B2
• Time in Patent Office: Days
• US Class Current: 455/160.100
• CPC Class Codes: H03G 3/3052 in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/32, H03G3/34 take precedence

Abstract

The disclosure is directed to a mobile communication device that includes automatic gain control (AGC) circuitry and operates in either a tracking mode or an acquisition mode. A received signal is sampled n times to calculate an energy estimate that is used to set the gain control values within the AGC circuitry. The value of n varies depending on whether the handset is operating in the acquisition mode or the tracking mode. Acquisition mode is typically considered to be the mode prior to coarse timing acquisition, also referred to as frame acquisition.

Claims

1. A mobile communications device comprising:

a receiver configured to receive a broadcast signal from a wireless broadcast network, and operate in either an acquisition mode or a tracking mode; and

automatic gain control circuitry configured to set a gain control value based on a first number of samples of the received broadcast signal when the receiver is operating in the acquisition mode and on a second number of samples of the received broadcast signal when the receiver is operating in the tracking mode.

2. The mobile communications device of claim 1, wherein the first number of samples is less than the second number of samples.

3. The mobile communications device of claim 1, wherein the received broadcast signal comprises a plurality of OFDM symbols.

4. The mobile communications device of claim 3, wherein the second number of samples comprises substantially one of the plurality of OFDM symbols.

5. The mobile communications device of claim 3, wherein the first number of samples comprises a fraction of one of the plurality of OFDM symbols.

6. The mobile communications device of claim 5, wherein the first number of samples comprises one sixteenth or less of one of the plurality of OFDM symbols.

7. The mobile communications device of claim 1, wherein the received broadcast signal includes a TDM pilot signal.

8. The mobile communications device of claim 7, further comprising:

a processor configured to operate the receiver in the acquisition mode if the TDM pilot signal has not been acquired and operated the receiver in the tracking mode once the TDM pilot signal has been acquired.

9. The mobile communications device of claim 1, wherein the automatic gain control circuitry is further configured to determine an energy estimate of the received broadcast signal.

10. The mobile communications device of claim 1, wherein the automatic gain control circuitry is further configured to set the gain control value based on an energy estimate of the first number of samples when the receiver is operated in the acquisition mode.

11. The mobile communications device of claim 1, wherein the automatic gain control circuitry is further configured to set the gain control value based on an energy estimate of the second number of samples when the receiver is operated in the tracking mode.

12. The mobile communications device of claim 1, wherein the gain control value comprises a plurality of values.

13. The mobile communications device of claim 1, wherein the gain control value includes an analog control value and a digital control value.

14. A method for automatic gain control in a mobile communications device, comprising:

receiving a broadcast signal from a wireless broadcast network;

operating in either an acquisition mode or a tracking mode; and

setting a gain control value based on a first number of samples of the received broadcast signal when operating in the acquisition mode and on a second number of samples of the received broadcast signal when operating in the tracking mode.

15. The method of claim 14, wherein the first number of samples is less than the second number of samples.

16. The method of claim 14, wherein the received broadcast signal comprises a plurality of OFDM symbols.

17. The method of claim 16, wherein the second number of samples comprises substantially one of the plurality of OFDM symbols.

18. The method of claim 14, wherein the received broadcast signal includes a TDM pilot signal.

19. The method of claim 14, further comprising:

operating the receiver in the acquisition mode if the TDM pilot signal has not been acquired; and

operating the receiver in the tracking mode once the TDM pilot signal has been acquired.

20. The method of claim 14, further comprising:

determining an energy estimate of the received broadcast signal.

21. The method of claim 20 further comprising:

determining an error signal which represents a power difference between the energy estimate and a desired reference level.

22. The method of claim 14, wherein the gain control value comprises a plurality of values.

23. A wireless communications device having a receiver configured to receive a broadcast signal from a wireless broadcast network, and operate in either an acquisition mode or a tracking mode, the device comprising:

means for setting a gain control value based on a first number of samples of the received broadcast signal when the receiver is operating in the acquisition mode and on a second number of samples of the received broadcast signal when the receiver is operating in the tracking mode.

24. A mobile communications device comprising:

a receiver configured to receive a broadcast signal from a wireless broadcast network, and operate in either an acquisition mode or a tracking mode; and

automatic gain control circuitry configured to set a gain control value periodically at a first rate when the receiver is operating in the acquisition mode and periodically at a second rate when the receiver is operating in the tracking mode.

25. The mobile communications device of claim 24, wherein the first rate is more frequent than the second rate.

26. A computer-readable medium encoded with a computer program for automatic gain control in a mobile communications device, which upon execution cause one or more processors to:

receive a broadcast signal from a wireless broadcast network;

operate in either an acquisition mode or a tracking mode; and

set a gain control value based on a first number of samples of the received broadcast signal when operating in the acquisition mode and on a second number of samples of the received broadcast signal when operating in the tracking mode.

27. The computer-readable medium of claim 26, wherein the first number of samples is less than the second number of samples.

28. The computer-readable medium of claim 26, wherein the received broadcast signal comprises a plurality of OFDM symbols.

29. The computer-readable medium of claim 28, wherein the second number of samples comprises substantially one of the plurality of OFDM symbols.

30. The computer-readable medium of claim 26, wherein the received broadcast signal includes a TDM pilot signal.