AGC fine-tuning be the adaptive time domain equalizer

• US 20040001541A1
• Filed: 06/28/2002
• Published: 01/01/2004
• Est. Priority Date: 06/28/2002
• Status: Active Grant

• Current Assignee: BWA Technology Incorporated (L3Harris Technologies, Inc.)
• Original Assignee: BWA Technology Incorporated (L3Harris Technologies, Inc.)
• Inventors: Haghighat, Afshin
• Granted Patent: US 7,660,344 B2
• Time in Patent Office: Days
• US Class Current: 375/232
• 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 coeficients 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 gain control for a QAM signal, the improvement comprising the steps of using a non-decision aided algorithm at the intermediate frequency level for coarse tuning and using a modified Adaptive Time Domain Equalizer (ATDE) to fine tune the level of the I/Q baseband signals and perform I/Q amplitude and phase imbalance correction along with a channel equalization.

2. The method of claim 1, wherein the fine-tuning uses center tap coefficients.

3. The method of claim 2, wherein the center tap coefficients are dynamic.

4. The method of claim 3, wherein the center tap coefficients are updated at least each symbol period.

5. The method of claim 3, wherein the center tap coefficients are limited to a predetermined range

6. The method of claim 1, wherein the ATDE is internal to the digital modem.

7. The method of claim 1, wherein the coarse AGC can use peak detection.

8. The method of claim 1, wherein the communication system is a cable network system.

9. The method of claim 1, wherein the communication system is a point-to-point communication system.

10. The method of claim 1 wherein said communication system is a point-to-multipoint communication system.

11. The method of claim 10 wherein said communication system operates in the millimeter wave frequency spectrum.

12. The method of claim 11 wherein said communication system is a time division multiple access system for communicating data in a frame format.

13. The method of claim 12 wherein the data density within each frame is dynamically variable.

14. The method of claim 12 wherein said communication system is a time-division duplex system.

15. The method of claim 14 wherein said communication system is an adaptive time division duplex system.

16. The method of claim 15 wherein the forward/reverse ratio is dynamically configurable.

35. The method of claim 2, wherein the center tap coefficients are dynamic.

17. A communication system with at least one digital modem for processing QAM signals, the improvement wherein the at least one digital modem comprises;

an automatic gain controller for coarse tuning of the baseband signal and an ATDE for fine tuning the baseband signal

18. The communication system of claim 17, wherein the ATDE modifies a center tap coefficient within a predetermined range

19. The communication system of claim 18, wherein the ATDE includes a lowpass filter/accumulator and a limiter.

20. The communication system of claim 17, wherein the automatic gain controller uses peak detection.

21. The communication system of claim 17, wherein the communication system is a cable network system.

22. The communication system of claim 17, wherein the communication system is a point-to-point communication system.

23. The computer system of claim 17 wherein said communication system is a point-to-multipoint communication system.

24. The computer system of claim 23 wherein said communication system operates in the millimeter wave frequency spectrum.

25. The computer system of claim 24 wherein said communication system is a time division multiple access system for communicating data in a frame format.

26. The computer system of claim 25 wherein the data density within each frame is dynamically variable.

27. The computer system of claim 25 wherein said communication system is a time-division duplex system.

28. The computer system of claim 27 wherein said communication system is an adaptive time division duplex system.

29. The computer system of claim 28 wherein the forward/reverse ratio is dynamically configurable.

30. A method of reducing re-synch time and I/Q amplitude and phase imbalance correction in a digital modem for a QAM signal comprising the steps of controlling the signal gain with a non-decision aided automatic gain controller to produce a baseband signal, and tuning the baseband signal in an Adaptive time domain equalizer utilizing non-fixed center tap coefficients.

31. The method of claim 30, wherein the center tap coefficients are dynamic.

32. The method of claim 31, wherein the center tap coefficients are limited to a predetermined range.

33. The method of claim 32, wherein the predetermined range is user configurable.

34. In a communication system including at least one digital modem, a method of gain control for a QAM signal, the improvement comprising using a modified Adaptive Time Domain Equalizer (ATDE) to tune the level of the I/Q baseband signals and perform I/Q amplitude and phase imbalance correction along with channel equalization, wherein center tap coefficients are not fixed.