Gain control in a communication channel

• US 7,653,158 B2
• Filed: 02/17/2006
• Issued: 01/26/2010
• Est. Priority Date: 11/09/2001
• Status: Active Grant

• Current Assignee: ParkerVision, Inc.
• Original Assignee: ParkerVision, Inc.
• Inventors: Brown, Kevin, Rawlins, Gregory S., Sorrells, David F., Rawlins, Michael W.
• Primary Examiner(s): VO, DON NGUYEN
• Application Number:
  US11/356,419
• Publication Number:
  US 20070086548A1
• Time in Patent Office: 1,439 Days
• Field of Search: 375/316, 375/345, 455/234.1
• US Class Current: 375/345
• CPC Class Codes: H03G 3/20 Automatic control H03G3/005 takes precedence; combined with volume compression or expansion H03G7/00
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

Methods and apparatuses for reducing DC offsets in a communication system are described. In a first aspect, a feedback loop circuit reduces DC offset in a wireless local area network (WLAN) receiver channel. The frequency response of the feedback loop circuit can be variable. In a second aspect, a circuit provides gain control in a WLAN receiver channel. The stored DC offset is subtracted from the receiver channel. First and second automatic gain control (AGC) amplifiers are coupled in respective portions of the receiver channel. In a third aspect, a feedback loop circuit reduces DC offset in a WLAN receiver channel. The feedback loop circuit includes a storage element that samples and stores receiver channel DC offset. The loop is opened, and the DC offset stored in the storage element is subtracted from the receiver channel. Circuits for monitoring DC offset, and for providing control signals for controlling the frequency response of the DC offset reducing circuits are also provided.

Claims

1. An apparatus for gain control in a communication channel, comprising:

a multiplier that receives a first automatic gain control (AGC) signal and outputs a second AGC signal, wherein said multiplier includes an operational amplifier, a first resistor and a second resistor arranged in a non-inverting amplifier configuration;

a first AGC amplifier that receives said first AGC signal, wherein said first AGC signal is directly coupled to said first AGC amplifier; and

a second AGC amplifier that receives said second AGC signal.

2. The apparatus of claim 1, wherein the communication channel is a wireless local area network (WLAN) receiver channel.

3. The apparatus of claim 1, wherein said second AGC amplifier is located upstream in a receiver channel from the first AGC amplifier.

4. The apparatus of claim 1, wherein said second AGC amplifier receives a radio frequency signal and said first AGC amplifier receives a baseband signal.

5. The apparatus of claim 1, wherein said second AGC amplifier receives a radio frequency signal and said first AGC amplifier receives an intermediate frequency signal.

6. The apparatus of claim 1, wherein said multiplier multiplies said first AGC signal by an integer amount to generate said second AGC signal.

7. The apparatus of claim 1, wherein said multiplier multiplies said first AGC signal by an integer amount, and said integer amount is equal to 2.

8. A method for gain control in a communication channel, comprising the steps of:

(1) multiplying a first automatic gain control (AGC) signal by an amount to generate a second AGC signal, wherein said multiplying step is performed using an operational amplifier, a first resistor and a second resistor arranged in a non-inverting amplifier configuration;

(2) providing the first AGC signal to a first AGC amplifier, wherein the first AGC signal is directly coupled to the first AGC amplifier; and

(3) providing the second AGC signal to a second AGC amplifier.

9. The method of claim 8, wherein the communication channel is a wireless local area network (WLAN) receiver channel.

10. The method of claim 8, further comprising the step of:

positioning the second AGC amplifier upstream in a receiver channel from the first AGC amplifier.

11. The method of claim 8, further comprising the steps of:

receiving a radio frequency receiver channel signal with the second AGC amplifier; and

receiving a baseband receiver channel signal with the first AGC amplifier.

12. The method of claim 8, further comprising the steps of:

receiving a radio frequency receiver channel signal with the second AGC amplifier; and

receiving an intermediate frequency receiver channel signal with the first AGC amplifier.

13. The method of claim 8, wherein step (1) comprises the step of:

multiplying the first AGC signal by an integer amount to generate the second AGC signal.

14. The method of claim 8, wherein step (1) comprises the step of:

multiplying the first AGC signal by 2 to generate the second AGC signal.

15. The method of claim 8, wherein step (1) comprises the step of:

amplifying the first AGC signal to generate the second AGC signal.