发明名称 |
Demodulator comprising an indicator circuit for use in common to cancellation of a pilot signal and an indication of a reception state |
摘要 |
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.
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申请公布号 |
US4680792(A) |
申请公布日期 |
1987.07.14 |
申请号 |
US19850708454 |
申请日期 |
1985.03.05 |
申请人 |
NEC CORPORATION;CLARION CO., LTD. |
发明人 |
TANAKA, KOUICHI;KUWAJIMA, TAKESHI;AMAZAWA, KIYOSHI |
分类号 |
H03D1/22;H04B1/16;H04H40/45;H04H40/81;(IPC1-7):H04H5/00 |
主分类号 |
H03D1/22 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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