Automatic VSB/QAM modulation recognition method and apparatus

Details Automatic VSB/QAM modulation recognition method and apparatus Automatic VSB/QAM modulation recognition method and apparatus

1994-12-13

1997-06-03

Tse, Young T.

Pulse or digital communications

Receivers

Amplitude modulation

375344, 375350, 348725, H04L 2706, H04N 544

Patent

active

056362501

ABSTRACT:
Methods and apparatus for automaticly distinguishing between QAM and VSB modulated signals and, for implementing an automatic VSB/QAM modulation recognition circuit are described. In accordance with various described embodiments, a narrow digital passband filter is used to sweep across the frequency region of a received HDTV signal where a VSB pilot tone would be located if the received signal is a VSB signal. The power of the filtered HDTV signal is estimated and compared to various preselected thresholds. If a power threshold value indicative of the presence of a VSB pilot tone is exceeded VSB is declared present. If no VSB pilot tone is detected, as indicated by the measured signal power levels, receipt of a QAM signal is declared. Various methods of insuring that transient changes in a received signal do not result in an erroneous decision with regard to the type of demodulation to perform are also described.

REFERENCES:
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patent: 5264937 (1993-11-01), Christopher
patent: 5452015 (1995-09-01), Hulyalkar
patent: 5487186 (1996-01-01), Scarpa
patent: 5506636 (1996-04-01), Patel
patent: 5548617 (1996-08-01), Patel et al.
patent: 5557337 (1996-09-01), Scarpa
patent: 5565932 (1996-10-01), Citta et al.

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