Carrier recovery circuit for offset qpsk demodulators
CA 1279906 C · Owner: Nec Corporation · Inventors: Otani, Susumu; Nawata, Hizuru
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
CARRIER RECOVERY CIRCUIT FOR OFFSET QPSK DEMODULATORS", ABSTRACT OF DISCLOSURE, A carrier recovery circuit comprises a voltage-controlled oscillator with a .pi./2 phase shifter coupled to it for generating carriers of quadrature phase relationship. First and second phase comparators respectively detect phase differences between an offset QPSK modulated signal and the carriers of the quadrature phase relationship. Signal from the first phase comparator is delayed by a 1/2 symbol duration and applied to one input of a quadri-phase detector having stable phase angles at .pi./4 (3/4).pi. (5/4).pi. and (7/4).pi. radian and signal from the second phase comparator is applied to the other input of …
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Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.
Why it's free to use
- Granted February 5, 1991. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended February 5, 2008.
- We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
Timeline
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Sources & verification
Official CIPO records
Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.