AGC fine-tuning by the adaptive time domain equalizer

• US 7,660,344 B2
• Filed: 06/28/2002
• Issued: 02/09/2010
• Est. Priority Date: 06/28/2002
• Status: Active Grant

• Current Assignee: BWA Technology Incorporated
• Original Assignee: BWA Technology Incorporated
• Inventors: Haghighat, Afshin
• Primary Examiner(s): Corrielus; Jean B
• Application Number:
  US10/183,161
• Publication Number:
  US 20040001541A1
• Time in Patent Office: 2,783 Days
• Field of Search: 375/219, 375/222, 375/229, 375/232, 375/259, 375/316, 375/345, 375/285, 375/350, 455/284, 455/296, 455/305, 455/234.1, 455/245.1
• US Class Current: 375/222
• CPC Class Codes: H04L 2025/0342 QAM
• CPC Class Codes: H04L 2025/03477 not time-recursive
• CPC Class Codes: H04L 25/03019 adaptive, i.e. capable of adjustment during data reception
• CPC Class Codes: H04L 27/3809 Amplitude regulation arrangements

Abstract

A method of improvement for gain control for a Quadrature Amplitude Modulation (QAM) signal within a communication system with at least one digital modem. The communication system utilizes a non-decision aided AGC at the intermediate frequency level and a modified Adaptive Time Domain Equalizer (ADTE) to fine tune the level of baseband signals, perform phase and amplitude correction, and channel equalization. The center tap coefficients of or dynamically modified by the ADTE. The resynchronization time and phase and amplitude imbalance correction will be reduced as a consequence of the controlling of the signal gain by a non-decision aided automatic gain controller.

Claims

1. In a communication system including at least one digital modem, a method of processing a quadrature amplitude modulation (QAM) signal, the method comprising:

coarse tuning a received QAM signal using a non-decision aided gain controller at an intermediate frequency level, wherein inphase/quadrature baseband signals within the received signal having amplitudes defined by the coarse tuning;

fine tuning, using an adaptive time domain equalizer (ATDE), the inphase/quadrature baseband signals by changing dynamic center tap coefficients relative to at least one side coefficient to perform inphase/quadrature amplitude correction;

wherein the communication system is a point-to-multipoint communication system, wherein the communication system operates in the millimeter wavelength spectrum, wherein the communication system is a time division multiple access system for communicating data in a frame format, wherein the communication system is a time-division duplex system, and wherein fine tuning, using the ATDE, the inphase/quadrature baseband signals by changing dynamic center tap coefficients comprises filtering the dynamic center tap coefficients and limiting the filtered dynamic center tap coefficients.

2. A communication system with at least one digital modem for processing quadrature amplitude modulation (QAM) signals, wherein the at least one digital modem comprises:

an automatic gain controller for coarse tuning a received QAM signal; and

an adaptive time domain equalizer (ATDE) for fine tuning inphase/quadrature baseband signals within the received QAM signal;

wherein the ATDE modifies a dynamic center tap coefficient relative to at least one side coefficient within a predetermined range determined by user and defined by a limiter.

3. The communication system of claim 2, wherein the ATDE includes a lowpass filter/accumulator configured to receive the dynamic center tap coefficient and the limiter is configured to receive the dynamic center tap coefficient from the lowpass filter/accumulator, to limit the dynamic center tap coefficient, and to provide the limited dynamic center tap coefficient to a multiplier.

4. The communication system of claim 2, wherein the automatic gain controller uses peak detection.

5. The communication system of claim 2, wherein the communication system is a cable network system.

6. The communication system of claim 2, wherein the communication system is a point-to-point communication system.

7. The communication system of claim 2 wherein the communication system is a point-to-multipoint communication system.

8. The communication system of claim 7 wherein the communication system operates in the millimeter wavelength spectrum.

9. The communication system of claim 8 wherein the communication system is a time division multiple access system for communicating data in a frame format.

10. The communication system of claim 9 wherein a data density within each frame is dynamically variable.

11. The communication system of claim 9 wherein the communication system is a time-division duplex system.

12. The communication system of claim 11 wherein the communication system is an adaptive time division duplex system.