Multi-channel receiver with improved AGC

• US 20080268798A1
• 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 7,769,357 B2
• Time in Patent Office: Days
• US Class Current: 455/127.2
• CPC Class Codes: H03G 3/3078 Circuits generating control signals for digitally modulated signals

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 method for processing one or more received signals of a plurality of possible received signals, the method comprising:

(a) generating, based on a gain control signal, an output signal from the one or more received signals;

(b) generating an intensity value in response to the output signal;

(c) for each possible received signal, determining whether or not to demodulate the output signal using a demodulator corresponding to the possible received signal;

(d) generating a setpoint value in response to the determinations of step (c); and

(e) adaptively updating the gain control signal based on changes in the intensity value, wherein updates in the gain control signal result in the intensity value approximating the setpoint value.

2. The method of claim 1, wherein the one or more received signals comprise at least two received signals.

3. The method of claim 1, wherein:

step (c) further comprises generating, for each possible received signal, a flag indicating whether the possible received signal is or is not present in a form sufficient for demodulation; and

step (d) comprises selecting the setpoint value from a plurality of setpoint values in response to the plurality of flags in combination.

4. The method of claim 3, 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;

step (c) comprises generating three flags corresponding to the possible COFDM signal and the two possible TDM signals, respectively; and

step (d) comprises selecting the setpoint value by indexing the table with a pointer having a value formed from concatenating the three flags.

5. The method of claim 3, further comprising:

(f) generating, in response to the output signal, a signal strength signal for each possible received signal;

(g) processing the flag and the signal strength signal for each possible received signal to determine if the possible received signal is fading or not fading;

(h) selecting, 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

(i) selecting a step size from the selected plurality of step sizes, wherein the gain control signal is updated based on the selected step size.

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

7. The method of claim 3, wherein each setpoint value of the plurality of setpoint values has at least one corresponding control signal value, and further comprising the step of generating at least one control signal in response to the at least one control signal value corresponding to the selected setpoint value.

8. The method of claim 7, wherein additional circuitry within the receiver is selectively enabled and disabled by the at least one control signal.

9. The method of claim 7, wherein the output signal is digitized by an analog-to-digital converter having a resolution controlled by the at least one control signal.

10. The method of claim 1, wherein the gain control signal is updated based on a selected step size proportional to a difference in magnitude between the setpoint value and the intensity value.

11. The method of claim 10, wherein the selected step size is chosen from a plurality of step sizes.

12. The method of claim 1, further comprising, for each determination of step (c) to demodulate the output signal, the step of demodulating the output signal using the demodulator corresponding to the possible received signal.

13. A method for processing one or more received signals of a plurality of possible received signals, the method comprising:

(a) generating, based on a gain control signal, an output signal from the one or more received signals;

(b) generating an intensity value in response to the output signal;

(c) for each possible received signal, (i) determining whether or not to demodulate the output signal using a demodulator corresponding to the possible received signal and (ii) generating a flag in accordance with the determination;

(d) generating a signal strength signal for each possible received signal;

(e) selecting 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;

(f) selecting a step size from the selected plurality of step sizes; and

(g) adaptively updating the gain control signal based on change in the intensity value and the selected step size.

14. The method of claim 13, wherein the one or more received signals comprise at least two received signals.

15. The method of claim 13, further comprising the step of processing the flag and the signal strength signal for each possible received signal to determine if the possible received signal is fading or not fading, wherein the plurality of step sizes is selected from the larger plurality of step sizes based on whether at least one of the possible received signals is fading.

16. The method of claim 15, wherein step (e) comprises selecting, 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.

17. The method of claim 13, further comprising the step of selecting 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.

18. The method of claim 17, wherein the selected step size is proportional to a difference in magnitude between the setpoint value and the intensity value.

19. The method of claim 17, 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;

step (c) comprises generating three flags corresponding to the possible COFDM signal and the two possible TDM signals, respectively; and

the setpoint value is selected by indexing the table with a pointer having a value formed from concatenating the three flags.

20. The method of claim 13, further comprising, for each determination of step (c) to demodulate the output signal, the step of demodulating the output signal using the demodulator corresponding to the possible received signal.