Method and system for DC compensation and AGC

• US 8,331,892 B2
• Filed: 03/05/2009
• Issued: 12/11/2012
• Est. Priority Date: 03/29/2008
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Kadous, Tamer A., Yao, Iwen, Wang, Jibing, Jing, Weihong, Li, Yong
• Primary Examiner(s): LE, DINH THANH
• Application Number:
  US12/398,285
• Publication Number:
  US 20100184397A1
• Time in Patent Office: 1,377 Days
• Field of Search: 455/312, 455/232.1, 455/324, 455/266, 455/296, 455/245.1, 455/305
• US Class Current: 455/234.1
• CPC Class Codes: H03G 3/3068 Circuits generating control signals for both R.F. and I.F. stages
• CPC Class Codes: H03G 3/3078 Circuits generating control signals for digitally modulated signals
• CPC Class Codes: H04L 25/061 providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of dc offset removal of dc offset in coupling arrangements H04L25/029, H04L25/0296

Abstract

A technique for performing AGC and DC compensation in a receiver. The receiver comprises an energy estimator for generating an estimate of the level of a received signal; an RF device to apply gain to the received signal; an AGC for controlling the RF device gain based on the energy estimation; a first DC compensation loop for finely adjusting the DC component of the received signal in fast or slow tracking mode (FTM or STM); and a second DC compensation loop for coarsely adjusting the DC component of the received signal. Three modes of AGC operations: In Acquisition, iterations of FTM fine DC adjustment, short energy estimation, and RF device gain adjustment are performed during signal timing detection. In Connected, long energy estimation, RF device gain adjustment, and STM fine and coarse DC adjustments are performed during superframe preamble. In Sleep, FTM fine DC adjustment, short energy estimation, and RF device gain adjustment are performed during superframe preamble.

Claims

1. An apparatus for processing a received radio frequency (RF) signal, comprising:

an RF device for processing the received RF signal to generate a downconverted signal;

an energy estimator coupled to the RF device for providing a signal related to an energy estimate of the received RF signal;

an automatic gain control (AGC) module comprising the energy estimator and a digital variable gain amplifier (DVGA), the DVGA of the AGC module for controlling the gain of the RF device based on the energy estimate signal;

a fine DC compensation module coupled to the RF device for performing fine adjustment of a DC component in the downconverted received signal, wherein a signal output from the DVGA of the AGC module controls the fine DC compensation module to perform the fine adjustment;

a coarse DC compensation module coupled to the RF device for performing coarse adjustment of the DC component in the downconverted received signal, wherein a signal output from the DVGA of the AGC module controls the coarse DC compensation module to perform the coarse adjustment;

an analog-to-digital converter (ADC) coupled to the RF device for converting the downconverted received signal from an analog domain to a digital domain; and

a digital gain module coupled to the ADC and adapted to adjust the level of the downconverted received signal in the digital domain,

wherein the AGC module is adapted to control the digital gain module based on the energy estimate signal.

2. The apparatus of claim 1, wherein the RF device comprises a low noise amplifier (LNA).

3. The apparatus of claim 1, wherein the RF device comprises a mixer.

4. The apparatus of claim 1, wherein the AGC module controls the gain of the RF device in a predetermined set of gains.

5. The apparatus of claim 1, wherein the fine DC compensation module performs fine adjustment of the DC component in the downconverted received signal in a fast tracking mode (FTM) or slow tracking mode (STM).

6. The apparatus of claim 1, wherein the fine DC compensation module performs fine adjustment of the DC component in the downconverted received signal in the digital domain.

7. The apparatus of claim 1, wherein the coarse DC compensation module performs coarse adjustment of the DC component in the downconverted received signal in the analog domain.

8. The apparatus of claim 3, further comprising a controller coupled to the coarse DC compensation module and adapted to configure the coarse DC compensation module based on a series of measurements of DC level from the AGC module corresponding to a series of gain states, when the RF received signal is not present.

9. An apparatus for processing a received radio frequency (RF) signal, comprising:

an RF device for processing the received RF signal to generate a downconverted signal;

an energy estimator coupled to the RF device for providing a signal related to an energy estimate of the received RF signal;

an automatic gain control (AGC) module comprising the energy estimator and a digital variable gain amplifier (DVGA), the DVGA of the AGC module for controlling the gain of the RF device based on the energy estimate signal;

a fine DC compensation module coupled to the RF device for performing fine adjustment of a DC component in the downconverted received signal, wherein a signal output from the DVGA of the AGC module controls the fine DC compensation module to perform the fine adjustment;

a coarse DC compensation module coupled to the RF device for performing coarse adjustment of the DC component in the downconverted received signal, wherein a signal output from the DVGA of the AGC module controls the coarse DC compensation module to perform the coarse adjustment;

a signal processing module coupled to the RF device for detecting timing information in the downconverted received signal; and

a controller coupled to the signal processing module, wherein in response to the signal processing module not detecting the timing information in the downconverted received signal, the controller is adapted to perform one or more iterations of the following sequential operations;

instruct the fine DC compensation module to perform a fine adjustment in a fast tracking mode (FTM) of the DC component in the downconverted received signal;

instruct the energy estimator to generate an energy estimate of the received RF signal; and

instruct the AGC module to control the gain of the RF device based on the energy estimate signal.

10. The apparatus of claim 9, wherein in response to the signal processing module detecting the timing information in the downconverted received signal, the controller is adapted to perform a predetermined number of one or more iterations of the following sequential operations:

instruct the fine DC compensation module to perform a fine adjustment in the FTM of the DC component in the downconverted received signal;

instruct the energy estimator to generate an energy estimate of the received RF signal; and

instruct the AGC module to control the gain of the RF device based on the energy estimate signal.

11. An apparatus for processing a received radio frequency (RF) signal, comprising:

an RF device for processing the received RF signal to generate a downconverted signal;

an energy estimator coupled to the RF device for providing a signal related to an energy estimate of the received RF signal;

an automatic gain control (AGC) module comprising the energy estimator and a digital variable gain amplifier (DVGA), the DVGA of the AGC module for controlling the gain of the RF device based on the energy estimate signal;

a fine DC compensation module coupled to the RF device for performing fine adjustment of a DC component in the downconverted received signal, wherein a signal output from the DVGA of the AGC module controls the fine DC compensation module to perform the fine adjustment;

a coarse DC compensation module coupled to the RF device for performing coarse adjustment of the DC component in the downconverted received signal, wherein a signal output from the DVGA of the AGC module controls the coarse DC compensation module to perform the coarse adjustment;

a signal processing module coupled to the RF device for detecting timing information in the downconverted received signal; and

a controller coupled to the signal processing module and adapted to perform the following sequential operations;

instruct the energy estimator to generate an energy estimate of the received RF signal in a timing relationship with the downconverted received signal; and

instruct the AGC module to control the gain of the RF device based on the energy estimate signal in the timing relationship with the downconverted received signal.

12. The apparatus of claim 11, wherein the controller is further adapted to perform the following operations:

instruct the fine DC compensation module to perform a fine adjustment in a slow tracking mode (STM) of the DC component in the downconverted received signal in the timing relationship with the downconverted received signal; and

instruct the coarse DC compensation module to perform a coarse adjustment of the DC component in the downconverted received signal in the timing relationship with the downconverted received signal.

13. The apparatus of claim 12, wherein the timing relationship comprises a time interval for the signal processing module to process at least a portion of a superframe preamble of the downconverted received signal.

14. An apparatus for processing a received radio frequency (RF) signal, comprising:

an RF device for processing the received RF signal to generate a downconverted signal;

an energy estimator coupled to the RF device for providing a signal related to an energy estimate of the received RF signal;

an automatic gain control (AGC) module comprising the energy estimator and a digital variable gain amplifier (DVGA), the DVGA of the AGC module for controlling the gain of the RF device based on the energy estimate signal;

a fine DC compensation module coupled to the RF device for performing fine adjustment of a DC component in the downconverted received signal, wherein a signal output from the DVGA of the AGC module controls the fine DC compensation module to perform the fine adjustment;

a coarse DC compensation module coupled to the RF device for performing coarse adjustment of the DC component in the downconverted received signal, wherein a signal output from the DVGA of the AGC module controls the coarse DC compensation module to perform the coarse adjustment;

a signal processing module coupled to the RF device for detecting timing information in the downconverted received signal; and

a controller coupled to the signal processing module and adapted to perform the following operations if the DC component of the downconverted received signal exceeds a predetermined threshold;

instruct the fine DC compensation module to perform a fine adjustment in a slow tracking mode (STM) of the DC component in the downconverted received signal in a timing relationship with the downconverted received signal; and

instruct the coarse DC compensation module to perform a coarse adjustment of the DC component in the downconverted received signal in the timing relationship with the downconverted received signal.

15. An apparatus for processing a received radio frequency (RF) signal, comprising:

an RF device for processing the received RF signal to generate a downconverted signal;

an energy estimator coupled to the RF device for providing a signal related to an energy estimate of the received RF signal;

an automatic gain control (AGC) module comprising the energy estimator and a digital variable gain amplifier (DVGA), the DVGA of the AGC module for controlling the gain of the RF device based on the energy estimate signal;

a fine DC compensation module coupled to the RF device for performing fine adjustment of a DC component in the downconverted received signal, wherein a signal output from the DVGA of the AGC module controls the fine DC compensation module to perform the fine adjustment;

a coarse DC compensation module coupled to the RF device for performing coarse adjustment of the DC component in the downconverted received signal, wherein a signal output from the DVGA of the AGC module controls the coarse DC compensation module to perform the coarse adjustment;

a signal processing module coupled to the RF device for detecting timing information in the downconverted received signal; and

a controller coupled to the signal processing module and adapted to perform a predetermined one or more iterations of the following sequential operations;

instruct the fine DC compensation module to perform a fine adjustment in a fast tracking mode (FTM) of the DC component in the downconverted received signal in a timing relationship with the downconverted received signal;

instruct the energy estimator to generate an energy estimate of the received RF signal in the timing relationship with the downconverted received signal; and

instruct the AGC module to control the gain of the RF device based on the energy estimate signal in the timing relationship with the downconverted received signal.

16. The apparatus of claim 15, wherein the timing relationship comprises a time interval for the signal processing module to process at least a portion of a superframe preamble of the downconverted received signal.

17. A method of processing a received radio frequency (RF) signal for adjusting a programmable power gain, comprising:

generating a signal related to an energy estimate of the received RF signal;

controlling the programmable power gain by amplifying a digital variable gain based on the energy estimate signal;

downconverting the received RF signal;

adjusting a DC component of the downconverted signal in a relatively fine manner, wherein the amplified digital variable gain controls the adjustment in the relatively fine manner;

adjusting the DC component of the downconverted signal in a relatively coarse manner, wherein the amplified digital variable gain controls the adjustment in the relatively coarse manner;

performing one or more iterations of the following sequential operations prior to detecting timing information in the downconverted signal;

adjusting the DC component of the downconverted signal in the relatively fine manner and in a fast tracking mode (FTM),

generating the signal related to the energy estimate of the received RF signal, and controlling the programmable power gain based on the energy estimate signal; and

detecting the timing information in the downconverted signal.

18. The method of claim 17, further comprising performing a predetermined number of one or more iterations of the following sequential operations after detecting the timing information in the downconverted signal:

adjusting the DC component of the downconverted signal in the relatively fine manner and in the FTM;

generating the signal related to the energy estimate of the received RF signal; and

controlling the programmable power gain based on the energy estimate signal.

19. A method of processing a received radio frequency (RF) signal for adjusting a programmable power gain, comprising:

generating a signal related to an energy estimate of the received RF signal;

controlling the programmable power gain by amplifying a digital variable gain based on the energy estimate signal;

downconverting the received RF signal;

adjusting a DC component of the downconverted signal in a relatively fine manner, wherein the amplified digital variable gain controls the adjustment in the relatively fine manner;

adjusting the DC component of the downconverted signal in a relatively coarse manner, wherein the amplified digital variable gain controls the adjustment in the relatively coarse manner;

detecting timing information in the downconverted signal;

generating the signal related to the energy estimate of the received RF signal in a timing relationship with the downconverted signal; and

controlling the programmable power gain based on the energy estimate signal in the timing relationship with the downconverted signal.

20. The method of claim 19, further comprising:

adjusting the DC component of the downconverted signal in the relatively fine manner and in a slow tracking mode (STM) in a timing relationship with the downconverted signal; and

adjusting the DC component of the downconverted signal in the relatively coarse manner in the timing relationship with the downconverted signal.

21. The method of claim 20, wherein the timing relationship comprises a time interval for processing at least a portion of a superframe preamble of the downconverted signal.

22. A method of processing a received radio frequency (RF) signal for adjusting a programmable power gain, comprising:

generating a signal related to an energy estimate of the received RF signal;

controlling the programmable power gain by amplifying a digital variable gain based on the energy estimate signal;

downconverting the received RF signal;

adjusting a DC component of the downconverted signal in a relatively fine manner, wherein the amplified digital variable gain controls the adjustment in the relatively fine manner;

adjusting the DC component of the downconverted signal in a relatively coarse manner, wherein the amplified digital variable gain controls the adjustment in the relatively coarse manner;

detecting timing information in the downconverted signal; and

performing a predetermined number of one or more iterations of the following sequential operations;

adjusting the DC component of the downconverted signal in the relatively fine manner and in a fast tracking mode (FTM) in a timing relationship with the downconverted signal;

generating the signal related to the energy estimate of the received RF signal in the timing relationship with the downconverted signal; and

controlling the programmable power gain based on the energy estimate signal in the timing relationship with the downconverted signal.

23. The method of claim 22, wherein the timing relationship comprises a time interval for processing at least a portion of a superframe preamble of the downconverted signal.

24. An apparatus for processing a received radio frequency (RF) signal for adjusting a programmable power gain, comprising:

means for generating a signal related to an energy estimate of the received RF signal;

means for controlling the programmable power gain by amplifying a digital variable gain based on the energy estimate signal;

means for downconverting the received RF signal;

means for adjusting a DC component of the downconverted signal in a relatively fine manner, wherein the amplified digital variable gain controls the adjustment in the relatively fine manner;

means for adjusting the DC component of the downconverted signal in a relatively coarse manner, wherein the amplified digital variable gain controls the adjustment in the relatively coarse manner;

means for controlling the following in a sequential order prior to detecting timing information in the downconverted signal;

means for adjusting the DC component of the downconverted signal in the relatively fine manner and in a fast tracking mode (FTM),

means for generating the signal related to the energy estimate of the received RF signal, and

means for controlling the programmable power gain based on the energy estimate signal; and

means for detecting the timing information in the downconverted signal.

25. An apparatus for processing a received radio frequency (RF) signal for adjusting a programmable power gain, comprising:

means for generating a signal related to an energy estimate of the received RF signal;

means for controlling the programmable power gain by amplifying a digital variable gain based on the energy estimate signal;

means for downconverting the received RF signal;

means for adjusting a DC component of the downconverted signal in a relatively fine manner, wherein the amplified digital variable gain controls the adjustment in the relatively fine manner;

means for adjusting the DC component of the downconverted signal in a relatively coarse manner, wherein the amplified digital variable gain controls the adjustment in the relatively coarse manner;

means for detecting timing information in the downconverted signal; and

means for controlling the following in a timing relationship with the downconverted signal after the timing information in the downconverted signal is detected;

means for generating the signal related to the energy estimate of the received RF signal in the timing relationship with the downconverted signal; and

means for controlling the programmable power gain based on the energy estimate signal in the timing relationship with the downconverted signal.

26. The apparatus of claim 25, wherein the controlling means additionally controls the following in the timing relationship with the downconverted signal after the timing information in the downconverted signal is detected:

means for adjusting the DC component of the downconverted signal in the relatively fine manner and in a slow tracking mode (STM); and

means for adjusting the DC component of the downconverted signal in the relatively coarse manner.

27. An apparatus for processing a received radio frequency (RF) signal for adjusting a programmable power gain, comprising:

means for generating a signal related to an energy estimate of the received RF signal;

means for controlling the programmable power gain by amplifying a digital variable gain based on the energy estimate signal;

means for downconverting the received RF signal;

means for adjusting a DC component of the downconverted signal in a relatively fine manner, wherein the amplified digital variable gain controls the adjustment in the relatively fine manner;

means for adjusting the DC component of the downconverted signal in a relatively coarse manner, wherein the amplified digital variable gain controls the adjustment in the relatively coarse manner;

means for detecting timing information in the downconverted signal; and

means for controlling a predetermined one or more iterations of the following in a timing relationship with the downconverted signal;

means for adjusting the DC component of the downconverted signal in the relatively fine manner and in a fast tracking mode (FTM);

means for generating the signal related to the energy estimate of the received RF signal; and

means for controlling the programmable power gain based on the energy estimate signal.

28. A computer readable program product for processing a received radio frequency (RF) signal for adjusting a programmable power comprising a computer-readable medium having instructions stored thereon, the instructions being executable by one or more processors and comprising:

instructions for generating a signal related to an energy estimate of the received RF signal;

instructions for controlling the programmable power gain by amplifying a digital variable gain based on the energy estimate signal;

instructions for downconverting the received RF signal;

instructions for adjusting a DC component of the downconverted signal in a relatively fine manner, wherein the amplified digital variable gain controls the adjustment in the relatively fine manner;

instructions for adjusting the DC component of the downconverted signal in a relatively coarse manner, wherein the amplified digital variable gain controls the adjustment in the relatively coarse manner;

instructions for detecting timing information in the downconverted signal;

instructions for generating the signal related to the energy estimate of the received RF signal in a timing relationship with the downconverted signal; and

instructions for controlling the programmable power gain based on the energy estimate signal in the timing relationship with the downconverted signal.