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US 4,232,393 AGranted
Muting arrangement of a radio receiver with a phase-locked loop frequency synthesizer
AssigneeNippon Gakki Seizo Kabushiki Kaisha
InventorsMichiaki Kumaoka, Sinzi Aosima
Life of this patent
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Abstract
In a muting arrangement of a radio receiver using a phase-locked loop frequency synthesizer as a local osicillator, a detector detects an in-lock or out-of-lock state of the phase-locked loop through an output state of a phase comparator included in a feedback loop of the phase-locked loop frequency synthesizer, and a mute gate provided in a signal transmission path of the receiver is operated to mute an audio output when the phase-locked loop is out of lock. An indicator may be provided for visually indicating that the phase-locked loop is in lock.
Claims5
A radio receiver comprising:
- a signal transmission path including a mixer circuit for converting a radio-frequency signal into an intermediate frequency signal, an intermediate frequency amplifier for amplifying said intermediate frequency signal, and a detection circuit for demodulating said intermediate frequency signal;
- a local oscillator circuit means having a phase-locked loop comprised of a voltage-controlled oscillator for providing a local-frequency signal to said mixer circuit, a frequency divider for dividing the output frequency of said voltage-controlled oscillator, a reference signal generator to produce a reference frequency signal, a phase comparator for comparing in phase said reference frequency signal with the output signal of said frequency divider, and a loop filter connected between said phase comparator and said voltage-controlled oscillator for supplying said voltage-controlled oscillator with a control voltage signal having a magnitude which is a function of the phase difference between the input signals of said phase comparator;
- a non-lock detection circuit means connected to the output of said phase comparator for detecting a non-lock state of said phase-locked loop in which the output signals of said frequency divider and said reference signal generator are not coincident in phase;
- and
- mute gate circuit means provided at the output side of said detection circuit of said signal transmission path of the receiver and responsive to said non-lock detection circuit means to mute the demodulated output signal at said signal transmission path, thereby interrupting production of an audio signal from the output of the receiver when the output signals of said frequency divider and signal reference signal generator are not coincident in phase.
2 more elements
An FM radio receiver comprising:
- a local oscillator circuit means having a phase-locked loop comprised of a voltage-controlled oscillator, a frequency divider for dividing the output frequency of said voltage-controlled oscillator, a reference signal generator to produce a reference frequency signal, a phase comparator for comparing in phase said reference frequency signal with the output signal of said frequency divider, and a loop filter connected between said phase comparator and said voltage-controlled oscillator for supplying said voltage-controlled oscillator with a voltage signal having a magnitude which is a function of the phase difference between the input signals of said phase comparator;
- a mixer circuit for mixing an incoming broadcast FM signal with the output signal of said voltage-controlled oscillator to produce an intermediate frequency FM signal;
- a frequency discriminator connected to receive the intermediate frequency FM signal from said mixer circuit;
- a non-lock detection circuit means connected to the output side of said phase comparator for detecting a non-lock state of said phase locked loop in which the output signals of said frequency divider and said reference signal generator are not coincident in phase;
- and
- mute gate circuit means provided at the output side of said frequency discriminator of a signal transmission path of the receiver and responsive to said non-lock detection circuit means to mute the output signal of said frequency discriminator, thereby interrupting production of an audio signal from the output of the receiver when the output signals of said frequency divider and said reference signal generator are not coincident in phase.
3 more elements
Dependencies are inferred from the claim text.