Gte Products Corporation

Gte Sylvania Incorporated

Wilfred L Hand

Craig W Brun

Kenneth J Burdick

Robert C Wheeler

Paul G Wolfe

Arthur H Klein

Charles B Neal

Victor J Jacek

An interface circuit that couples the output of a differential AFC detector to a tuner and in so doing provides a single-ended control signal and a substantially constant reference signal. A bridging circuit combines the differential outputs to effect a substantially constant signal which is appropriately scaled by a referencing circuit so as to develop the reference voltage required. A dividing circuit coupled to one of the differential outputs develops an AFC control voltage having the range required to accommodate the tuner's AFC-responsive circuitry.

AFC Interface circuit

A delay circuit for enhancing acquisition of a synthesizer PLL subsequent to change in the synthesizer's frequency of operation or a change in the source of tuning voltage applied to a voltage-controllable reference oscillator. A control circuit determines whether the reference oscillator operates in a crystal-controlled or in a voltage-controlled mode. The delay circuit includes a monostable having an output coupled to the control circuit and a trigger input coupled to both an ENTER CHANNEL indicator and a pulse generator. The monostable is triggered, thereby assuring temporary crystal-controlled operation of the reference oscillator, in response to an ENTER CHANNEL indicator or to an output from a pulse generator. The pulse generator is responsive to a change in the source of reference oscillator tuning control voltage from, for example, a manually variable fine tuning potentiometer to an AFC control circuit.

Acquisition delay circuit for a PLL reference oscillator

An apparatus for coupling a source of signals to a receiver having a ground return electrically coupled to the AC line and for providing immunity from interfering ambient signals. The apparatus includes a coaxial transmission line surrounded at both ends by feedthrough capacitor coupling the outer conductor of the transmission line to the ground return of the signal source. A toroidal ferrite member also surrounds the transmission line between the feedthrough capacitors thereby reducing the current flowing in the outer conductor and the resulting direct pickup of ambient signals.

TV antenna isolation system

A circuit for applying a fine tuning voltage to an oscillator operating within distinct ranges of frequency. The fine tuning voltage is tailored so that a substantially equal fine tuning range, for example, .+-.1.5 MHz, is achieved with respect to each of the ranges of frequency. The circuit includes a potentiometer that is connected between two voltage sources. The values of the voltage sources are appropriately varied in response bandswitch information. In a television receiver the values are varied in response to a signal indicating operation on a Low Band VHF, a High Band VHF, or a UHF channel.

Fine tuning circuit

In a synthesizer system having a reference oscillator selectively operable in either a voltage-controlled or an injection-locked mode, a circuit for effecting the appropriate mode of operation. The circuit includes an analog gate coupled between the output of a crystal oscillator and the input of the reference oscillator. The analog gate is driven by a logic element responsive to a plurality of signals indicative of specific operating conditions. In particular, the circuit assures that the reference oscillator is coupled to the crystal oscillator, that is, the reference oscillator operates in the injection locked mode, while the synthesizer PLL achieves acquisition.

Control circuit for establishing voltage-controlled or injection-locked

A voltage-controllable reference oscillator for a synthesized receiver. In one mode of operation the reference oscillator is injection locked to a crystal-controlled oscillator so that the receiver's local oscillator frequency is a rational multiple of the crystal oscillator frequency. In another mode of operation the reference oscillator is isolated from the crystal-controlled oscillator and its operating frequency is determined by the voltage applied at its tuning control terminal. The control voltage is selectively provided by a manually variable fine tuning circuit or by an AFC circuit. An acquisition delay circuit develops a pulse when a channel is selected or when the source of tuning voltage is changed, thereby assuring that the reference oscillator is operating in the injection-locked mode until the synthesizer phase-locked loop has achieved acquisition.

AFC System for a synthesizer tuning system

A method and circuit for detecting and removing chrominance signal components from the luminance channel of a television receiver is shown. The luminance channel is separated into distinct subchannels, one of which has a filter providing attenuation at the chrominance subcarrier frequency. A detection circuit operates to select the output of the filtered subchannel whenever a chrominance subcarrier signal appears in the luminance channel. The detection circuit is sensitive to the phase relationship between the chrominance signal and a portion of the luminance signal and is therefore substantially immune to signals other than chrominance subcarriers, including high frequency components of the luminance signal.

Signal-dependent chrominance subcarrier filtering circuit

A high-speed, solid-state, electronic circuit for alternately coupling two separate video signal paths to a third video signal path in response to high frequency square wave excitation, the circuit utilizing two dual-gate metal oxide semiconductor field effect transistors having oppositely phased signals applied to respective switching gates for cancellation of switching transient signals.

Multi-channel video switch using dual-gate MOS-FETS

A video processing system for a television receiver is shown. The video processing system includes a gain controlled stage through which a video signal is coupled. The gain of the stage is controlled to provide contrast control of the video signal. The video signal is also applied to an aperture correction circuit which develops an aperture correction signal including a pre-shoot transient responses. The aperture correction signal is also coupled through the gain controlled stage so that it is amplified or attenuated by the same amount as the video signal. An automatic peaking control circuit receives the pre-shoot and over-shoot signals to generate an automatic control signal to control the gain of the aperture correction circuit. A tracking control circuit causes the automatic peaking control circuit to accurately track the setting of an adjustable control which controls the gain of the aperture correction circuit. The output of the gain controlled stage is coupled to an output stage where the black level of the video signal is controlled by a black level control circuit. The disclosed video processing system is further adapted for fabrication in integrated circuit form.

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Clarence, NY, United States of America

Wilfred L Hand