Sony Corporation

Masayuki Hongu

Masaharu Tokuhara

Hiromi Kawakami

Shigeru Ohmuro

Tsutomu Niimura

Masahiro Tada

Yoshio Ishigaki

Yoshihiro Yamamoto

Takeshi Hamada

Takao Sumi

Takashi Okada

Kazuo Yamagiwa

Toshio Sarugaku

Takahiko Tamura

Hiroyuki Kita

Hisafumi Motoe

Shigeru Omuro

In a picture-in-picture television receiver, the subpicture signal is A-D converted; the converted digital subpicture signal is latched in response a subpicture clock in synchronism with a subpicture synchronizing signal; the latched signal is latched again and stored in an image memory in response to a main picture synchronizing signal; and the latched signal is read from the image memory in synchronism with the main picture synchronizing signal, in order that the subpicture can stably be inserted in a predetermined area of the main picture by eliminating the unstable data duration during which variation in the subpicture signal is different for each bit signal thereof.

Picture-in-picture television receivers

A dark signal component below a predetermined level of a video signal is varied such that a dark peak level is made to coincide with a pedestal level by feedback control. According to this configuration, a signal component toward a white level side above the predetermined level is not changed by dark restoration, thus obtaining stable color reproduction and stable brightness which are not affected by the dark restoring operation.

Dark level restoring circuit

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.

Television sound receiver

A synchronous detector for detecting an information signal modulated onto a carrier, such as a video IF signal, is disclosed in which there are provided a circuit for supplying the modulated information signal in the form of a vestigial sideband signal, a filter circuit coupled to the supplying circuit which includes a tuning circuit tuned to the frequency of the carrier on which the information signal is modulated, an emitter follower circuit connected to the output of the filter circuit, a limiter circuit connected to the filter circuit, for producing a switching carrier, and a multiplier having first and second input terminals coupled to the output of the limiter circuit and to the supplying circuit, for multiplying the modulated information signal and the switching carrier to obtain said information signal. In one embodiment, the limiter circuit includes a differential amplifier having first and second transistors, base electrodes of which are connected to the emitter follower circuit, and third and fourth common base transistors, emitter electrodes of which are respectively connected to collector electrodes of the first and second transistors and collector electrodes of which provide output terminals for supplying the switching carrier.

Carrier regenerating circuit for a synchronous detector

A synchronous detector suitable for use in a color television receiver detects both a video signal and an audio IF signal, but in a fashion in which these two signals do not interfere with one another. In the detector, a tuner provides an IF signal in which the video signal and audio or sound IF signals are modulated on a carrier; a signal generator, such as a phase-locked loop, provides both a detecting signal synchronized with the carrier of the IF signal, and a comparing signal having the same frequency as the carrier of the IF signal but phase-shifted .pi./2 therefrom; a synchronous detecting circuit for synchronously detecting the IF signal by the detecting signal to produce the video signal; and a phase comparator for phase comparing the IF signal with the comparing signal to provide the sound IF signal. In one arrangement, the phase comparator provides a filtered version of the sound IF signal as an AFT control signal to control the fine tuning of the tuner. In another embodiment, two phase comparators are included so that the sound IF signal and the AFT control signal are provided separately.

Detector circuit for a television receiver

In a system in which an intermediate frequency signal is synchronously detected using an intermediate frequency carrier signal derived from the intermediate frequency signal by means of a tuned circuit and a limiter circuit to remove amplitude variations therefrom, an automatic fine tuning signal is derived in a phase detector to which are fed the intermediate frequency carrier signal after its phase has been shifted 90 degrees in a phase shifter and either the intermediate frequency signal or the intermediate frequency carrier signal. When the intermediate frequency carrier signal is used in the phase detector, a second tuned circuit is used therein and buffering between the two tuned circuits prevents interaction therebetween.

Automatic fine tuning circuit

An automatic fine tuning (AFT) circuit includes a frequency discriminator for discriminating an intermediate frequency signal, a capacitor supplied with the discriminated intermediate frequency signal to produce an AFT voltage thereacross, a comparator circuit for comparing the AFT voltage with a reference voltage, a first switching transistor controlled by the comparator circuit and which supplies and charges the capacitor with the reference voltage during a channel selection operation when the AFT voltage is less than the reference voltage, a second switching transistor controlled by the comparator circuit and which connects the capacitor to ground to discharge the same during a channel selection operation when the AFT voltage is greater than the reference voltage, and a third switching transistor for rendering the comparator circuit operative during a channel selection operation and inoperative during an AFT operation.

AFT circuit

An automatic fine tuning loop in a television receiver is controlled by phase comparison between a video intermediate frequency signal and a reference oscillator signal. The reference oscillator signal is used in synchronous detection of the video intermediate frequency signal. The frequency of the reference oscillator is controlled by a phase locked loop, of which it is a part, and which includes a low-pass filter having selectable high and low cut-off frequencies. A lock-out detector selects the high cut-off frequency for rapid correction when lock-out is detected and selects the low cut-off frequency for frequency stability when lock-in is detected. An AFT disable switch disables the automatic fine tuning loop during manual tuning. In one embodiment, a disable switch ganged with the AFT disable switch selects the high cut-off frequency in the low-pass filter to prevent hunting.

Television receiver

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

A video signal processing circuit includes an amplifier with a circuit connected to it to emphasize the amplification of some frequencies relative to others. A non-linear circuit is also connected to the amplifier and comprises a capacitor connected in series with non-linear elements that change the amplification of positive and negative overshoots of the signal relative to the middle amplitude range. The result is non-linear modification of emphasis and can be used to pre-emphasize video signals before using them to modulate the frequency of a carrier and, in the playback section to de-emphasize the signals to minimize FM noise. Use of the capacitor prevents direct current from flowing and thus affecting the threshold levels of the non-linear elements. Component values can be selected to effect temperature compensation.

Capacitive-type nonlinear emphasis circuit

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

A variable delay device for delaying an electrical signal includes a bar-shaped magnetostrictive member to be a transmitting path of a supersonic wave, an input transducer for converting an electric signal into a supersonic wave and an output transducer for converting a supersonic wave into an electric signal, the input and output transducers being provided at at opposite end portions of the magnetostrictive member, and a magnetic field producing device provided between the input and output transducers for supplying the magnetostrictive member with a magnetic field which varies in intensity along the elongated direction of the magnetostrictive member. The magnetic field supplied to the magnetostrictive member is controlled by a control signal applied to the magnetic field producing device to vary the Young's modulus of the magnetostrictive member. As a result, the velocity of the supersonic wave being transmitted therein is varied, to thereby control the delay time of the electric signal.

Variable delay device

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.

Growing community of inventors

Kawasaki, Japan

Masayuki Hongu