Telecommunications – Receiver or analog modulated signal frequency converter – Frequency or phase modulation
Patent
1992-09-03
1995-04-25
Eisenzopf, Reinhard J.
Telecommunications
Receiver or analog modulated signal frequency converter
Frequency or phase modulation
455222, 455303, 455307, 455312, 381 13, H04B 110
Patent
active
054107512
ABSTRACT:
An FM noise reduction circuit including a level detection circuit receiving an intermediate frequency signal. The level detection circuit rectifies the intermediate frequency signal, and outputs a rectified intermediate frequency signal. A first frequency filter passes the rectified intermediate frequency signal in a first frequency range, and outputs a first voltage responsive to the portion of the rectified intermediate frequency signal passed in the first frequency range. A first interference signal detection circuit includes a second frequency filter. The second frequency filter passes the rectified intermediate frequency signal in a second frequency range and outputs a second voltage responsive to the portion of the rectified intermediate frequency signal passed in the second frequency range. The second interference signal detection circuit includes a third frequency filter. The third frequency filter passing the rectified intermediate frequency signal in a third frequency range, and outputs a third voltage responsive to the portion of the rectified intermediate frequency signal passed in the third frequency range. The first, second, and third frequency ranges are different. A control circuit controls muting, high frequency components, and blending of a demodulated audio output responsive to the first, second, and third voltages, to reduce FM noise.
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Eisenzopf Reinhard J.
NEC Corporation
Vo Nguyen
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