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:
Nov. 16, 1999
Filed:
Jun. 10, 1997
Hiroyuki Kiyanagi, Sendai, JP;
Masayuki Watabe, Sendai, JP;
Fujitsu Limited, Kanagawa, JP;
Abstract
A carrier regenerating circuit used for a demodulator which demodulates many-valued orthogonal amplitude modulation signals. The carrier regenerating circuit consists of a first PLL (phase-locked loop) section, including a detector for detecting an intermediate-frequency signal using a local oscillator, a phase error detecting section and a first loop filter, which feeds back phase error information to the local oscillator via the first loop filter; and a second PLL (phase-locked loop) section, including a frequency control section a second loop filter, which feeds back a frequency control signal to the local oscillator via the second loop filter by performing an updating operation by means of the frequency control section when a mark ratio due to the phase error information deviates from a predetermined range. The carrier regenerating circuit with a simplified circuit configuration can always synchronize an input signal (a many-valued orthogonal amplitude-modulation signal) by quickly adjusting the frequency of a regeneration carrier signal to an optimum value even when the input signal is out of synchronization.