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:
Jul. 14, 1987
Filed:
Mar. 05, 1985
NEC Corporation, Tokyo, JP;
Clarion Co., Ltd., Tokyo, JP;
Abstract
In a demodulator comprising an indicator (31) for indicating either stereo reception or monaural reception, an indicator circuit (30) is used to cancel a pilot signal included in a stereophonic signal and to produce a drive signal for driving the indicator. The indicator circuit comprises a negative feedback loop formed by an adder circuit (41), a phase detector (43), and a cancellation circuit (45). The cancellation circuit supplies the indicator and the adder circuit with the drive signal and a cancelling signal synchronized with and approximate to the pilot signal, respectively. The adder circuit substracts the cancelling signal from the pilot signal to deliver an intermediate signal to a multiplex decoder and to the cancellation circuit through the phase detector. The cancellation circuit comprises a wave generator for generating a pair of currents proportional to an amplitude of the pilot signal and a level adjusting circuit for converting one of the currents into the cancelling signal. The other current is converted into the drive signal.