Multi-channel receiver with improved AGC

• US 20080267326A1
• Filed: 04/25/2007
• Published: 10/30/2008
• Est. Priority Date: 04/25/2007
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Wang, Zhenyu, Yu, Jinguo, Lai, Yhean-Sen, Song, Jie
• Granted Patent: US 7,809,343 B2
• Time in Patent Office: Days
• US Class Current: 375/345
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT

Abstract

An improved multi-channel receiver for satellite broadcast applications or the like. In an exemplary embodiment, an AGC loop, under the control of an AGC processor, controls the gain of an analog sub-receiver adapted to simultaneously receive multiple signals to achieve a desired AGC setpoint signal intensity from the sub-receiver. Multiple digital demodulators, coupled to the sub-receiver by an analog-to-digital converter (ADC), demodulate the multiple received signals. The AGC controller, based upon which of the received signals are being demodulated, selects the desired AGC setpoint from a table of setpoints. The AGC controller may also provide selective power control to circuitry in the receiver and select the resolution of the ADC. The controller updates the AGC loop with step values selected from a group of values by an AGC control algorithm. Different groups of step values may be used by the controller depending on whether the signals are fading or not.

Claims

1. A receiver comprising:

a gain section adapted to generate, based on a gain control signal, an output signal from one or more received signals of a plurality of possible received signals;

a power detector adapted to generate an intensity value in response to the output signal;

a demodulator, for each possible received signal, adapted to determine whether or not to demodulate the output signal; and

a controller adapted to (1) generate a setpoint value in response to the determinations of the plurality of demodulators and (2) adaptively update the gain control signal based on changes in the intensity value to result in the intensity value approximating the setpoint value.

2. The receiver of claim 1, wherein:

each demodulator is adapted to generate a flag indicating whether the corresponding possible received signal is or is not present in a form sufficient for demodulation; and

the controller is adapted to select the setpoint value from a plurality of setpoint values in response to the plurality of flags in combination.

3. The receiver of claim 2, wherein:

the plurality of possible received signals comprise a possible COFDM signal and two possible TDM signals;

the plurality of setpoint values are stored in a table having at least eight entries;

the demodulators are adapted to generate three flags corresponding to the possible COFDM signal and the two possible TDM signals, respectively; and

the controller is adapted to select the setpoint value by indexing the table with a pointer having a value formed from concatenating the three flags.

4. The receiver of claim 2, wherein:

the demodulators are adapted to generate, in response to the output signal, a signal strength signal for each possible received signal;

the controller is adapted to (1) process the flag and the signal strength signal for each possible received signal to determine if the possible received signal is fading or not fading, (2) select, based on whether at least one of the possible received signals is fading, a plurality of step sizes from a larger plurality of step sizes, and (3) select a step size from the selected plurality of step sizes, wherein the gain control signal is updated based on the selected step size.

5. The receiver of claim 4, wherein the selected step size is proportional to a difference in magnitude between the setpoint value and the intensity value.

6. The receiver of claim 2, wherein:

each setpoint value of the plurality of setpoint values has at least one corresponding control signal value; and

the controller is adapted to generate at least one control signal in response to the at least one control signal value corresponding to the selected setpoint value.

7. The receiver of claim 6, further comprising additional circuitry adapted to be selectively enabled and disabled by the at least one control signal.

8. The receiver of claim 6, further comprising an analog-to-digital converter adapted to digitize the output signal, wherein the analog-to-digital converter has a resolution controlled by the at least one control signal.

9. The receiver of claim 1, wherein the controller is adapted to update the gain control signal based on a selected step size proportional to a difference in magnitude between the setpoint value and the intensity value.

10. The receiver of claim 9, wherein the controller is adapted to choose the selected step size from a plurality of step sizes.

11. The receiver of claim 1, wherein each demodulator is adapted to demodulate the output signal based on the corresponding determination to demodulate the output signal.

12. A receiver comprising:

a gain section adapted to generate, based on a gain control signal, an output signal from one or more received signals of a plurality of possible received signals;

a power detector adapted to generate an intensity value in response to the output signal;

a demodulator, for each possible received signal, adapted to (i) determine whether or not to demodulate the output signal, (ii) generate a flag in accordance with the determination, and iii) generate a signal strength signal for the possible received signal; and

a controller adapted to (1) select a plurality of step sizes from a larger plurality of step sizes in response to the plurality of flags and the plurality of signal strength signals, (2) select a step size from the selected plurality of step sizes, and (3) adaptively update the gain control signal based on change in the intensity value and the selected step size.

13. The receiver of claim 12, wherein the controller is adapted to (i) process the flag and the signal strength signal for each possible received signal to determine if the possible received signal is fading or not fading and (ii) select the plurality of step sizes from the larger plurality of step sizes based on whether at least one of the possible received signals is fading.

14. The receiver of claim 13, wherein the controller is adapted to select, as the selected plurality of step sizes, 1) a first plurality of step sizes from the larger plurality of step sizes if at least one of the possible received signals is fading and 2) a second plurality of step sizes from the larger plurality of step sizes if none of the possible received signals is fading.

15. The receiver of claim 12, wherein the controller is adapted to select a setpoint value from a plurality of setpoint values in response to the plurality of flags in combination, wherein the updating of the gain control signal results in the intensity value approximating the setpoint value.

16. The receiver of claim 15, wherein the selected step size is proportional to a difference in magnitude between the setpoint value and the intensity value.

17. The receiver of claim 15, wherein:

the plurality of possible received signals comprise a possible COFDM signal and two possible TDM signals;

the plurality of setpoint values are stored in a table having at least eight entries;

the demodulators are adapted to generate three flags corresponding to the possible COFDM signal and the two possible TDM signals, respectively; and

the controller is adapted to select the setpoint value by indexing the table with a pointer having a value formed from concatenating the three flags.

18. The receiver of claim 12, each demodulator is adapted to demodulate the output signal based on the corresponding determination to demodulate the output signal.