Supat Wongwirawat

US Patent:

20050157820, Jul 21, 2005

Filed:

Jan 15, 2004

Appl. No.:

10/757536

Inventors:

Supat Wongwirawat - Langhorne PA, US
Azzedine Touzni - Doylestown PA, US
Mark Hryszko - Doylestown PA, US
Raul Casas - Doylestown PA, US
Yiwen Yu - Holland PA, US

International Classification:

H04L027/14
H04L027/16
H04L027/22

US Classification:

375326000, 375324000

Abstract:

A digital receiver, that may be used to receive VSB/QAM digital television signals, includes an adaptive fine carrier recovery circuit that compensates for deviations in the carrier frequency or phase. The carrier recovery circuit de-rotates a signal including phase errors. Estimations of phase errors are filtered using a filter whose gain and bandwidth are adjusted adaptively. This allows the carrier recovery circuit to track phase/frequency offset without introducing significant jitter. In one embodiment, the receiver includes a DFE, and the adaptive carrier recovery circuit mitigates instability that might be associated with the DFE.

US Patent:

20080123786, May 29, 2008

Filed:

Nov 29, 2007

Appl. No.:

11/947105

Inventors:

Supat Wongwirawat - Langhorne PA, US
Mark Hryszko - Doylestown PA, US
Devan Namboodiri - Holland PA, US
Raul A. Casas - Doylestown PA, US

International Classification:

H03D 1/06
H04B 1/10
H04L 1/00
H04L 25/08

US Classification:

375346, 375227

Abstract:

The present invention is directed to a method and system for detecting and compensating for signal impairments in modulated signals. Phase noise and gain noise based signal impairments can be detected as a function of the difference between the optimal position in the constellation grid (the center) and the actual position in the constellation grid of a received symbol. As symbols are received, they are compared to optimal positions and a measure of the phase noise and gain noise can be determined for each symbol. Over a period of time, the detector can compute an average measure of phase noise and gain noise. When the average measure of phase noise and/or gain noise reaches a predefined threshold, the detector can indicate a phase noise based and/or gain noise based signal impairment has been detected to the receiver. The receiver can adjust one or more receive parameters in order to improve reception. Burst noise based signal impairments can be detected as a function of the number of QAM symbols that have an i component or a q component that exceeds the maximum constellation value in a predefined period of time or in the course of a predefined number of symbols received. When the number of number of QAM symbols having burst noise exceeds reaches a predefined threshold, the detector can indicate a burst noise signal impairment to the receiver and the receiver can adjust one or more receive parameters in order to improve reception.

US Patent:

20080123787, May 29, 2008

Filed:

Nov 29, 2007

Appl. No.:

11/947124

Inventors:

Supat Wongwirawat - Langhorne PA, US
Mark Hryszko - Doylestown PA, US
Devan Namboodiri - Holland PA, US
Raul A. Casas - Doylestown PA, US

International Classification:

H03D 1/04

US Classification:

375346

Abstract:

The present invention is directed to a method and system for detecting and compensating for signal impairments in modulated signals. Phase noise and gain noise based signal impairments can be detected as a function of the difference between the optimal position in the constellation grid (the center) and the actual position in the constellation grid of a received symbol. As symbols are received, they are compared to optimal positions and a measure of the phase noise and gain noise can be determined for each symbol. Over a period of time, the detector can compute an average measure of phase noise and gain noise. When the average measure of phase noise and/or gain noise reaches a predefined threshold, the detector can indicate a phase noise based and/or gain noise based signal impairment has been detected to the receiver. The receiver can adjust one or more receive parameters in order to improve reception. Burst noise based signal impairments can be detected as a function of the number of QAM symbols that have an i component or a q component that exceeds the maximum constellation value in a predefined period of time or in the course of a predefined number of symbols received. When the number of number of QAM symbols having burst noise exceeds reaches a predefined threshold, the detector can indicate a burst noise signal impairment to the receiver and the receiver can adjust one or more receive parameters in order to improve reception.

US Patent:

20080123788, May 29, 2008

Filed:

Nov 29, 2007

Appl. No.:

11/947090

Inventors:

Supat Wongwirawat - Langhorne PA, US
Mark Hryszko - Doylestown PA, US
Devan Namboodiri - Holland PA, US
Raul A. Casas - Doylestown PA, US

International Classification:

H03D 1/06

US Classification:

375348

Abstract:

The present invention is directed to a method and system for detecting and compensating for signal impairments in modulated signals. Phase noise and gain noise based signal impairments can be detected as a function of the difference between the optimal position in the constellation grid (the center) and the actual position in the constellation grid of a received symbol. As symbols are received, they are compared to optimal positions and a measure of the phase noise and gain noise can be determined for each symbol. Over a period of time, the detector can compute an average measure of phase noise and gain noise. When the average measure of phase noise and/or gain noise reaches a predefined threshold, the detector can indicate a phase noise based and/or gain noise based signal impairment has been detected to the receiver. The receiver can adjust one or more receive parameters in order to improve reception. Burst noise based signal impairments can be detected as a function of the number of QAM symbols that have an i component or a q component that exceeds the maximum constellation value in a predefined period of time or in the course of a predefined number of symbols received. When the number of number of QAM symbols having burst noise exceeds reaches a predefined threshold, the detector can indicate a burst noise signal impairment to the receiver and the receiver can adjust one or more receive parameters in order to improve reception.