The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 29, 1997
Filed:
Aug. 19, 1993
Takashi Kaku, Kawasaki, JP;
Noboru Kawada, Kawasaki, JP;
Fujitsu Limited, Kawasaki, JP;
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.