Modulator and demodulator apparatus

Details Modulator and demodulator apparatus Modulator and demodulator apparatus

1993-08-19

1997-04-29

Tse, Young T.

Pulse or digital communications

Transceivers

Modems

375224, H04B 138

Patent

active

056256434

ABSTRACT:
The invention provides a modulator and demodulator apparatus (modem) which modulates and demodulates a signal in a main channel, for main data, and a secondary channel, for secondary data obtained by frequency division, and which includes a carrier detection unit for detecting a carrier from a demodulation signal and executes a data processing sequence for the demodulation signal in accordance with a result of detection of the carrier detection unit. This apparatus improved in that it can detect a carrier of a low roll-off ratio accurately and stably without a dispersion in detection time and, consequently, data of a demodulation signal can be processed with certainty. The modulator and demodulator apparatus comprises a filter having a characteristic wherein the time axis response is slow and it is provided at a stage preceding the carrier detection unit so that a demodulation signal which has passed through the filter is input to the carrier detection unit.

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