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:
May. 01, 2007
Filed:
Nov. 26, 2002
Tadashi Koga, Tokyo, JP;
Tadashi Koga, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
When a PLL circuit is used to extract and recover clock component from an information data signal, where an optical receive signal has been converted into an electrical signal, and to monitor the frequency of a recovered clock, a low frequency section frequency detection circuit having a BPF (band-pass filter) where transmission center frequency has been shifted to higher frequency relative to center frequency of the electrical signal and a high frequency section frequency detection circuit having a BPF where the transmission center frequency has been shifted to lower frequency are provided in parallel. Utilizing a slope on one side of each transmission characteristic of the BPF makes it possible to set detection frequency freely and accurately. Therefore, a frequency detection circuit without using a special device in an optical transmitter/receiver, capable of easily detecting accurate frequency shift of f±Δf or more, and of low price and high performance, can be obtained.