Sony Corporation

Hiromi Kawakami

Masayuki Hongu

Masaharu Tokuhara

Yoshihiro Yamamoto

Shigeru Ohmuro

Tsutomu Niimura

Masumi Ogawa

Toshiaki Meguro

An intercarrier sound detecting apparatus for a television receiver includes an antenna for receiving a television signal; a tuner for selecting a desired frequency range of the received television signal from the antenna and producing a tuned signal having a video intermediate frequency component in response thereto; a filter for extracting the video intermediate frequency component from the tuned signal; video intermediate frequency amplifiers for producing a video intermediate frequency signal having an amplitude-modulated video carrier component, in response to the extracted video intermediate frequency component; a phase-locked loop which phase-locks the video intermediate frequency signal with respect to the amplitude-modulated video carrier component thereof and produces an output signal having a 4.5 MHz beat signal component in response thereto; a band pass filter for transmitting substantially only the 4.5 MHz beat signal component; and a frequency discriminator for producing a sound signal in response to the 4.5 MHz beat signal component transmitted through the band pass filter.

Intercarrier sound detecting apparatus for a television receiver

A television sound receiver includes an input terminal for selectively receiving a television sound signal from one or more broadcasting stations and a home television apparatus, a tuner, having a local oscillator, connected to the input terminal, an intercarrier sound demodulating circuit connected to the tuner, a split-carrier sound demodulating circuit, including a limiter amplifier, connected to the tuner, a sound signal output terminal, and switching circuitry for selectively and operatively connecting the intercarrier or split-carrier sound demodulating circuit between the tuner and sound signal output terminal. Additionally the receiver includes an error detector connected to the split-carrier sound demodulating circuit for detecting the frequency error of the tuner local oscillator and a first operational circuit responsive to the output signal from the error detector which produces a first operational output signal whereby the output signal therefrom activates the switching circuitry such that the split-carrier sound demodulating circuit is operatively connected between the tuner and the sound signal output terminal when the output signal from the error detector is less than a predetermined level. Control circuitry is provided which supplies a signal to activate the switching circuitry such that the intercarrier sound demodulating circuit is operatively connected between the tuner and sound signal output terminal whenever the home television apparatus is operatively connected to the input terminal. A second operational circuit is also provided which is responsive to output signals from a pair of level detectors which are connected to the limiter amplifier. An output signal supplied from the second operational circuit activates the switching circuitry such that the intercarrier sound demodulating circuit is operatively connected between the tuner and the sound signal output terminal when the output signals from the level detectors are below a predetermined value.

Television sound receiver

A television sound receiver having an input terminal for receiving a television sound signal, a tuner including a local oscillator connected to the input terminal, an intercarrier sound demodulating circuit connected to the tuner, a split-carrier sound demodulating circuit, including a limiter amplifier connected to the tuner, a sound signal output terminal, and a switching device for selectively and operatively connecting either the intercarrier or split-carrier sound demodulating circuits between the tuner and the sound signal output terminal. Additionally, the receiver includes an error detecting device connected to the split-carrier sound demodulating circuit for detecting the frequency error of the local oscillator and a first operational device which is responsive to an output signal from the error detecting device and which produces a first operational device output signal which activates the switching device such that the split-carrier sound demodulating circuit is operatively connected between the tuner and the sound output terminal when the output signal from the error detecting device is less than a predetermined level. Level detectors are connected to the limiter amplifier and detect a level of the split-carrier sound signal. A second operational device, which is responsive to the output signal from the level detectors, produces an output signal which activates the switching device such that the intercarrier sound demodulating circuit is operatively connected between the tuner and the sound output terminal when the output signals from the level detectors are less than a predetermined value.

A muting circuit for a television or AM signal receiver which uses a synchronous detector. The muting circuit includes an input terminal for receiving an amplitude modulated signal, a synchronous detector for detecting such AM signal, a circuit for supplying a reference signal having a predetermined frequency and phase to the synchronous detector, an amplifier, a circuit path for delivering to the amplifier the detected signal produced by the synchronous detector, a level detecting device connected to the output of the synchronous detector for producing an excess signal when the detected signal exceeds a predetermined level, an integrator for producing a muting signal in response to the production over an extended period of time of the excess signal, and a switching device connected to the amplifier for muting the signal produced by the amplifier in response to the production of the muting signal.

Muting circuit

A synchronous detector adapted to detect a modulated information signal, such as a video IF signal. The modulated information signal is provided in the form of a vestigial sideband signal. A band-pass filter including a tuned circuit tuned to the frequency of the carrier on which the information signal is modulated has a pass band which is less than the frequency spectrum of the vestigial sideband signal so as to limit the frequency spectrum of the signal passed by the filter to a double sideband signal. A limiter is coupled to the band-pass filter to receive the double sideband signal and for deriving a switching carrier therefrom, the frequency of the switching carrier being equal to the frequency of the carrier on which the information signal is modulated. An emitter-follower circuit is connected between the band-pass filter and the limiter so as to couple the double sideband signal from the filter to the limiter. A multiplier circuit has first input terminals coupled to the limiter for receiving the derived switching carrier and second input terminals for receiving the modulated information signal, whereby the modulated information signal is multiplied with the switching carrier to obtain the information signal.

Synchronous detector particularly adapted for a video IF signal

An oscillating circuit provides first and second reference signals having a phase difference of 90.degree. with respect to each other. The oscillating circuit includes an oscillator providing the first reference signal at an output thereof, a voltage-to-current converting circuit, which may incorporate a common-base transistor, and a capacitor connected between the output of the oscillator and an input of the converting circuit. The output of the converting circuit then provides the second reference signal which differs in phase by 90.degree. from the first reference signal. The oscillator may include differentially connected transistors and an LC resonant circuit.

Oscillating circuit

Demodulating apparatus for a modulated signal comprised of a carrier deriving circuit which is supplied with the modulated signal and which derives an unmodulated carrier therefrom, the carrier deriving circuit including a tuned circuit having a center frequency substantially coincident with the carrier frequency of the modulated signal and a limiter circuit in which the limiter circuit imparts a phase shift to the signal supplied thereto in connection with its elimination of the amplitude fluctuations in the signal produced by the tuned circuit. A synchronous detector receives the modulated signal and the derived carrier so as to detect the modulated signal with the derived carrier. A phase shift circuit supplies the synchronous detector with a phase shifted modulated signal, the phase shift substantially compensating for the phase shift imparted by the limited circuit in the carrier deriving circuit, whereby the modulated signal and the carrier which are applied to the synchronous detector are substantially in phase with each other.

Demodulating apparatus with phase shift compensation

A television receiver has an automatic fine tuning circuit with a first phase-locked loop including a first low pass filter and a synchronous video detector with a second phase-locked loop including a second low pass filter. The cut off frequency of the first low pass filter is selected lower than the cut-off frequency of the second low pass filter, thereby enabling a stable operation of two phase-locked loops simultaneously.

Television receiver with synchronous detection and automatic fine tuning

A tuner for receiving signals broadcast on two spaced bands, each divided into several channels, has two fixed bandpass filters, one to pass all of the channels in the lower frequency band and the other to pass all of the channels in the higher frequency band. The tuner includes a mixer to which signals of either band are supplied by selective operation of a double-throw switch. A tunable local oscillator supplies a heterodyning signal to the mixer to convert any selected channel of the received signal to an intermediate frequency (i.f.) band chosen to avoid image interference from undesired channels, whether the local oscillator frequency is above or below the selected channel. To ease the constraints on the choice of the i.f. band, different i.f. filters tuned to first and second i.f. bands may be used for the higher and lower received bands. A second double-throw switch ganged with the first switch can then be used to direct the heterodyned signals to the proper i.f. filter.

Multi-band tuner with fixed broadband input filters

A tuner for receiving signals broadcast on two spaced bands, each divided into several channels, has two fixed bandpass filters, one to pass all of the channels in the lower band between the lowest frequency f.sub.P of the lowest channel and the highest frequency f.sub.S of the highest channel of the lower band, and the other to pass all of the channels in the upper frequency band between the lowest frequency f.sub.T of the lowest channel and the highest frequency f.sub.W in the highest channel of the upper band. The bandwidth of each channel is f.sub.B. The tuner includes an amplifier and a third filter to which signals of either band are supplied by selective operation of a switch. The third filter has a cut-off frequency below the second harmonic of the lowest frequency of the upper band to simplify the avoidance of image interference from second harmonic signals of the band. A tunable local oscillator supplies a heterodyning signal to the mixer to convert any selected channel of the received signal to an intermediate frequency (i.f.) band, and image interference is avoided by setting the local oscillator frequency f.sub.n required to convert channel n to the i.f. at a frequency above that channel such that the lowest frequency f.sub.L of the i.f. band satisfies the following conditions: ##EQU1##

Multi-band tuner

An amplifier provides a complete video and sound I.F. signal to a synchronous detector switching circuit, and the switching signal to be applied to the switching circuit is obtained from the same amplifier by connecting a grounded base stage, with its emitter impedance, in series with the amplifier load. The grounded base stage has a load tuned to the I.F. carrier frequency, and the filtered signal from the grounded base is the signal applied as the switching signal to the synchronous detector switching circuit.

Amplifying circuit

A transistor biasing circuit having a single biasing transistor for biasing first and second operational transistors. The biasing transistor has means connecting its base to its collector and means are provided to connect the base of each of the first and second operational transistors to the collector circuit of the biasing transistor. Each of the three transistors are arranged in a circuit between a pair of voltage terminals which are connected to a power supply. The arrangement of the resistors in the circuit paths of the biasing transistor and the operational transistors are in such a way as to provide circuit means for stabilizing the collector currents of the first and second transistors regardless of variations in the factor of h.sub.FE. This circuit arrangement provides an improved stabilization of the collector currents over prior art devices.

Transistor biasing circuit

A transistor biasing circuit having circuit means for biasing two amplifier transistors so as to stabilize the DC collector currents thereof regardless of variations in the factor h.sub.FE. The biasing circuit includes a biasing transistor having its emitter connected through specified resistances to the base circuits of the two amplifying transistors. In addition, a pair of series diode connected transistors are connected to the base circuit of the biasing transistor. By selecting specified values of the various resistance used in the biasing circuit arrangement, the desired stabilization technique is obtained. This circuit arrangement is particularly useful in the case of integrated circuits.

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Yokohama, Japan

Hiromi Kawakami