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Integrable quadrature FM demodulator using fewer signal pins
| Details |
Inventors: Goto, Kuniaki;
Assignee: Tokyo Shibaura Denki Kabushiki Kaisha (JP)
Primary Examiner: Grimm; Siegfried H.
Assistant Examiner: Mis; David C.
Attorney, Agent or Firm: Finnegan, Henderson, Farabow, Garrett & Dunner
A quadrature type FM demodulator device used, for example, in a television receiver, includes a band pass filter for filtering a sound intermediate frequency (SIF) signal input to the device. The output of the band pass filter is coupled through a filter circuit to an integrated circuit having a limiter amplifier and an FM detector to output a sound signal from the SIF signal. |
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DETAILED DESCRIPTION Accordingly, an object of the present invention is to provide a quadrature type FM demodulator device for detecting sound signals which requires a small number of signal pins for the sound intermediate frequency integrated circuit.
It is another object of the present invention to provide a quadrature type FM demodulator device which can be easily fabricated.
It is yet another object of this invention to provide a quadrature type FM demodulator which can be manufactured at a lower cost than the prior art devices.
According to the present invention, there is provided a quadrature type FM demodulator device for outputting a sound signal comprising a 4.
5 MHz band-pass filter means to which a sound intermediate frequency signal is inputted, a series R-C circuit including bias resistor means and bypass capacitor means, which is connected in parallel to the output of the filter means, a sound intermediate frequency signal integrated circuit, and a resonance circuit for tuning to a sound carrier signal.
The sound intermediate frequency signal integrated circuit includes a first power source pin impressed with a first potential, a second power source pin impressed with a second potential, and first, second, third and fourth signal pins.
The first signal pin is connected to an output terminal of the filter means and the second signal pin is connected to a junction of the resistor means and the capacitor means.
The integrated circuit further includes a sound intermediate frequency limiter amplifier means of the phase discriminating type of which the input terminals are respectively connected to the first and second signal pins, a frequency modulation detector of which a first input terminal is directly connected to an output terminal of the limiter amplifier means for receiving an output signal of the amplifier means, of which a second input terminal is connected to the fourth signal pin and receives a signal phase-shifted by 90.
degree.
from the output signal of the amplifier means, and of which an output terminal is connected to the third signal pin where an output sound signal is provided, and the phase shifting capacitor means of which one end is connected to the output terminal of the limiter amplifier so as to receive its output signal and the other end is connected to the fourth signal pin
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