Methods and apparatus for automatic gain control in broadband tuners

• US 7,577,414 B2
• Filed: 01/27/2005
• Issued: 08/18/2009
• Est. Priority Date: 01/27/2005
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Mehr, Iuri
• Primary Examiner(s): Le; Thanh C
• Application Number:
  US11/044,710
• Publication Number:
  US 20060166633A1
• Time in Patent Office: 1,664 Days
• Field of Search: 455/226.1, 455/226.2, 455/226.4, 455/232.1, 455/234.1, 455/234.2, 455/245.1, 455/250.1, 455/254, 375/345
• US Class Current: 455/234.1
• CPC Class Codes: H03G 2201/706 being quality indicator, e.g. BER,C/I
• 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: H04B 1/26 for superheterodyne receivers multiple frequency-changing H03D7/16

Abstract

In one aspect, an automatic gain control (AGC) for applying a variable gain to a broadband signal is provided. The AGC comprises a variable gain amplifier adapted to receive the broadband signal as an input, the variable gain amplifier configured to apply a variable gain to the broadband signal based on a value of a gain signal to provide an amplified broadband signal, and a controller to provide the gain signal to the variable gain amplifier, the controller adapted to determine the value of the gain signal based on at least one characteristic of the amplified broadband signal. In a further aspect, the one or more characteristic is a power characteristic of the broadband signal that facilitates control of the broadband signal within a desired power range.

Claims

1. An automatic gain control (AGC) for applying a variable gain to a broadband signal, the AGC comprising:

a variable gain amplifier adapted to receive the broadband signal as an input, the variable gain amplifier configured to apply a variable gain to the broadband signal based on a value of a gain signal to provide an amplified broadband signal; and

a controller to provide the gain signal to the variable gain amplifier, the controller adapted to determine the value of the gain signal based on at least one power characteristic of the amplified broadband signal,

wherein the controller includes at least one first power detector adapted to detect a first power characteristic to generate at least one sensed value and at least one second power detector adapted to detect a second power characteristic having peak values of the broadband signal, wherein the controller includes a default reference that is adjusted based at least on a first number of peak values of the broadband signal exceeding a first threshold during a predetermined time interval to determine the at least one reference value, and wherein the controller includes a comparator configured to provide an error signal indicative of a difference between the at least one sensed value and at the least one reference value.

2. The AGC of claim 1, wherein the at least one first power characteristic includes at least one of elements chosen from a set consisting of root mean square (RMS) values, envelope values, and peak values of the amplified broadband signal.

3. The AGC of claim 1, wherein the first power characteristic is an envelope of the broadband signal.

4. The AGC of claim 1, wherein the controller includes a gain mapper configured to determine the gain signal based on the error signal provided by the comparator.

5. The AGC of claim 4, wherein the controller includes a fast interferer detector coupled to the at least one second power detector, the fast interferer providing a fast interferer signal to the gain mapper when a second number of peak values of the broadband signal exceed a second threshold value during the predetermined time interval to indicate a fast interferer condition.

7. The AGC of claim 5, wherein the gain mapper is configured such that when the fast interferer detector provides the fast interferer signal, the gain mapper determines the gain signal based on the fast interferer signal instead of the error signal.

8. The AGC of claim 1, wherein the default reference is a constant value.

9. The AGC of claim 1, wherein the default reference is a function of at least one variable.

10. The AGC of claim 9, wherein the default reference is a function of at least one variable of the broadband signal.

11. The AGC of claim 10, wherein the default reference is a function of at least broadband signal strength.

12. The AGC of claim 1, in combination with a television tuner, wherein the amplified broadband signal is provided to front-end components of the television tuner to select a desired channel from the amplified broadband signal.

6. The AGC of 5, wherein the second number is greater than the first number.