Method and apparatus for automatic gain control of a multi-carrier signal in a communication receiver

• US 20040151264A1
• Filed: 05/12/2003
• Published: 08/05/2004
• Est. Priority Date: 02/01/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Montojo, Juan, Salvi, Rohan Sudhakar, Black, Peter
• Granted Patent: US 7,995,684 B2
• Time in Patent Office: Days
• US Class Current: 375/345
• 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 3/3078 Circuits generating control signals for digitally modulated signals
• CPC Class Codes: H03M 1/185 the determination of the range being based on more than one digital output value, e.g. on a running average, a power estimation or the rate of change
• CPC Class Codes: H04L 27/0002 analog front ends; means for connecting modulators, demodulators or transceivers to a transmission line duplex arrangements H04L5/143
• CPC Class Codes: H04L 27/28 with simultaneous transmission of different frequencies each representing one code element
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26

Abstract

A receiver operates to AGC a multi-carrier signal through a corresponding number of inner loops and an outer loop AGC processes. A first number of bits for representing the multi-carrier signal with a limited amount of interference is determined through a calibration mode process. The first number of bits provides for quantization of the multi-carrier signal at an outer loop AGC to a maximum quantization level. After the received signal power estimate is reached a predetermined “ON” threshold, the outer loop AGC is operated at a second number of bits higher than the first number of bits to allow a quantization of possible interference in accordance with a difference of the first and second number of bits. The outer loop AGC switches back to use the first number of bits when the received signal power estimate falls below a predetermined “OFF” threshold.

Claims

1. A method for a communication system receiver for processing a multi-carrier signal, comprising:

determining a first number of bits for quantization of said multi-carrier signal at an outer loop automatic gain control for said processing;

operating said outer loop automatic gain control at said first number of bits in an inactive mode by fixing an attenuation level of said outer loop to a fixed value, and at a second number of bits in an active state when a power estimate of said multi-carrier signal reaches an ON threshold;

operating said outer loop automatic gain control to switch from said second number of bits in said active state to said first number of bits in said inactive state when said power estimate of said received signal reaches an OFF threshold.

2. The method as recited in claim 1 further comprising:

an inner loop digital signal processing for rejecting undesired signal passed through an outer loop signal processing including said outer loop automatic gain control.

3. An apparatus for a communication system receiver for processing a multi-carrier signal, comprising:

an outer loop automatic gain control configured for operating at a first number of bits in an inactive mode by fixing an attenuation level of said outer loop to a fixed value, at a second number of bits in an active state when a power estimate of said multi-carrier signal reaches an ON threshold, and to switch from said second number of bits in said active state to said first number of bits in said inactive state when said power estimate of said received signal reaches an OFF threshold.

4. The apparatus as recited in claim 3 further comprising:

an inner loop digital signal processor for rejecting undesired signal passed through an outer loop signal processing including said outer gain automatic control.

5. A method for a communication system, comprising:

controlling gain of a multi carrier signal in accordance with operation of an outer loop automatic gain control quantizing said multi carrier signal at a first number of bits in an inactive mode by fixing an attenuation level of said outer loop to a fixed value and at a second number of bits in an active state when a power estimate of said multi-carrier signal reaches an ON threshold.

6. The method as recited in claim 5 wherein said controlling gain of a multi carrier signal further comprising switching from said second number of bits in said active state to said first number of bits in said inactive state when said power estimate of said received signal reaches an OFF threshold.

7. The method as recited in claim 5 further comprising:

rejecting, via an inner loop digital signal processing, undesired signal passed through an outer loop signal processing including said outer loop automatic gain control.

8. An apparatus for processing a multi carrier signal, comprising:

an outer loop automatic gain control for controlling gain of said multi carrier signal, including means for quantizing said multi carrier signal at a first number of bits in an inactive mode by fixing an attenuation level of said outer loop to a fixed value and at a second number of bits in an active state when a power estimate of said multi-carrier signal reaches an ON threshold and means for switching from said second number of bits in said active state to said first number of bits in said inactive state when said power estimate of said received signal reaches an OFF threshold.

9. The apparatus as recited in claim 8 further comprising:

an inner loop digital signal processor for rejecting undesired signal passed through an outer loop signal processing including said outer loop automatic gain control of each carrier of said multi carrier signal.