Audio demodulating circuit and television broadcast receiver
AssigneeSharp Kabushiki Kaisha
InventorKoji Oiwa
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Abstract
An audio demodulating circuit in accordance with the present invention for demodulating audio signals in a plurality of broadcast systems of mutually different frequency deviations such as the NTSC and the PAL, is arranged such that a connection between a trap circuit for suppressing adjacent interference and an intermediate frequency signal line can be controlled without using an externally applied special signal, based on a control voltage applied from a phase comparator with respect to a voltage control oscillator which generates a local oscillation signal for extracting an audio signal from the intermediate frequency signal.
Claims9
An audio demodulating circuit for demodulating audio signals in a plurality of broadcast systems of mutually different frequency deviations, comprising:
- a trap circuit;
- connection means for connecting said trap circuit to an intermediate frequency signal line;
- and
- connection control means for controlling a connection state of said connection means based on a control voltage, said control voltage being applied from a phase comparator to a voltage control oscillator which generates a local oscillating signal for extracting an audio signal from said intermediate frequency signal.
A television broadcast receiver provided with an audio demodulating circuit for demodulating audio signals in a plurality of broadcast systems of mutually different frequency deviations, wherein:
- said audio demodulating circuit comprises:
- at least one trap circuit;
- connection means for connecting said trap circuit or in the case where said trap circuit is provided in plural number, selectively connecting at least one of said plurality of trap circuits to an intermediate frequency signal line;
- and
- connection control means for controlling a connection state of said connection means based on a control voltage, the control voltage being applied from a phase comparator to a voltage control oscillator which generates a local oscillating signal for extracting an audio signal from said intermediate frequency signal.
Dependencies are inferred from the claim text.