GAIN CONTROL METHODS AND SYSTEMS IN AN AMPLIFIER ASSEMBLY

• US 20040104771A1
• Filed: 01/30/2003
• Published: 06/03/2004
• Est. Priority Date: 12/02/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Burns, Lawrence M., Dauphinee, Leonard
• Granted Patent: US 6,798,286 B2
• Time in Patent Office: Days
• US Class Current: 330/129
• CPC Class Codes: G01R 31/2607 Circuits therefor G01R31/2642 takes precedence
• CPC Class Codes: G01R 31/30 Marginal testing, e.g. by varying supply voltage testing computers during standby operation or idle time G06F11/22
• CPC Class Codes: G01R 31/31723 Hardware for routing the test signal within the device under test to the circuits to be tested, e.g. multiplexer for multiple core testing, accessing internal nodes routing the test signal to or from the device under test G01R31/31926
• CPC Class Codes: H01L 22/20 Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H03F 3/211 using a combination of several amplifiers H03F3/60 takes precedence
• CPC Class Codes: H03G 2201/307 being radio frequency signal
• CPC Class Codes: H03G 3/3036 in high-frequency amplifiers or in frequency-changers H03G3/3052, H03G3/32, H03G3/34 take precedence
• 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
• CPC Class Codes: H04N 5/4446 IF amplifier circuits specially adapted for B&W TV RF amplifiers in general H03F3/189
• CPC Class Codes: H04N 5/52 Automatic gain control
• CPC Class Codes: H04N 7/102 Circuits therefor, e.g. noise reducers, equalisers, amplifiers H04N7/108 takes precedence

Abstract

A Variable Gain Amplifier (VGA) amplifies an input signal according to a gain, to produce an amplified signal. A detector module detects a power indicative of a power of the amplified signal. A comparator module compares the detected power to a high threshold, a low threshold and a target threshold intermediate the high and low thresholds. A controller module changes the gain of the VGA so as to drive the detected power in a direction toward the middle threshold when the comparator module indicates the detected power is not between the high and low thresholds.

Claims

1. An Automatic Gain Control (AGC) method, comprising:

(a) amplifying an input signal according to a gain, to produce an amplified output signal;

(b) detecting a power of the amplified output signal;

(c) determining if the detected power is between a high threshold and a low threshold; and

(d) changing the gain so as to drive the detected power in a direction toward a target threshold between the high and low thresholds when the detected power is determined in step (c) to be not between the high and low thresholds.

2. The method of claim 1, wherein step (d) comprises changing the gain until the detected power crosses the target threshold.

3. The method of claim 1, further comprising:

(e) not changing the gain when the detected power is determined to be between the high and low thresholds in step (c).

4. The method of claim 1, further comprising:

(e) repeating steps (c) and (d) at predetermined time intervals.

5. The method of claim 1, wherein step (d) comprises changing the gain according to a ramp function.

6. The method of claim 1, wherein step (d) comprises changing the gain smoothly and continuously according to a ramp function.

7. The method of claim 1, wherein step (a) comprises amplifying the input signal with a variable gain stage only.

8. The method of claim 1, wherein:

step (a) comprises amplifying the input signal with a variable gain stage and a fixed gain stage; and

step (d) comprises changing the gain of the variable gain stage only.

9. The method of claim 1, wherein step (d) comprises:

decreasing the gain when it is determined in step (c) that the detected power is above the high threshold; and

increasing the gain when it is determined in step (c) that the detected power is below the low threshold.

10. The method of claim 1, wherein the input signal includes multiple frequency channels, and the amplified output signal includes the multiple frequency channels, and wherein step (b) includes detecting a combined power of the multiple frequency channels in the amplified output signal.

11. The method of claim 1, wherein the input signal is a television signal.

12. An Automatic Gain Control (AGC) system, comprising:

a Variable Gain Amplifier (VGA) configured to amplify an input signal according to a gain, to produce an amplified signal;

a detector configured to detect a power indicative of a power of the amplified signal;

a comparator module configured to compare the detected power to a high threshold, a low threshold and a target threshold intermediate the high and low thresholds; and

a controller module configured to change the gain of the VGA so as to drive the detected power in a direction toward the target threshold when the comparator module indicates the detected power is not between the high and low thresholds.

13. The system of claim 12, wherein the controller module is configured to change the gain of the VGA until the comparator module indicates that the detected power crosses the target threshold.

14. The system of claim 12, wherein the controller module is configured to not change the gain when the comparator module indicates the detected power is between the high and low thresholds.

15. The system of claim 12, wherein the detector, comparator and controller module are configured to repeat their respective functions at predetermined time intervals.

16. The system of claim 12, further comprising a ramp generator configured to generate a ramp signal, wherein the controller module is configured to change the gain as a function of the ramp signal.

17. The system of claim 16, wherein the gain change is smooth and continuous responsive to the ramp signal.

18. The system of claim 12, wherein the VGA includes a plurality of gain stages arranged in parallel with one another, the VGA gain being an aggregate of individual gains of the plurality of gain stages.

19. The system of claim 12, further comprising a fixed gain amplifier following the VGA, the power detector being coupled to an output of the fixed gain amplifier.

20. The system of claim 12, wherein the controller module is configured to:

decrease the gain when the comparator module indicates that the detected power is above the high threshold; and

increase the gain when the comparator module indicates that the detected power is below the low threshold.

21. The system of claim 12, wherein the input signal includes multiple frequency channels, and the amplified output signal includes the multiple frequency channels, and wherein the detector is configured to detect a combined power of the multiple frequency channels in the amplified output signal.

22. The system of claim 12, wherein the input signal is a television signal.