Rca Inc.

Abraham E Rindal

Max Ward Muterspaugh

William A Lagoni

Gregory George Tamer

Patrick D Griffis

A multiplier for multiplying the modulated sound and picture carriers to produce an intercarrier sound signal in a quasi-parallel sound channel of an IF section has a pair of anti-parallel connected diodes in a limiter for generating an amplitude limited version of the picture carrier. It has been discovered that the varying capacitance of the diodes with picture amplitude can cause phase shifts and hence phase modulation interference in the intercarrier signal. The latter is especially troublesome for stereo sound reproduction. To reduce such interference, a low value resistor is shunt coupled to the diodes to inhibit the capacitance variations of the diodes and resulting undesired phase modulation in the intercarrier sound signal.

Quasi-parallel television if suitable for stereo sound reception

A circuit has two signal paths. The first path provides a signal with a selected magnitude and phase. The second path selectively provides either no signal or a signal with twice the magnitude and opposite phase with respect to that provided by said first path. The signals of the two paths are combined to provide a signal with a selectable phase. The circuit can be used in a stereo decoder in which an L+R stereo sum signal is combined with an expanded R-L stereo difference signal, provided by an expander also used for a SAP signal, to produce left (L) and right (R) stereo signals so that when the SAP signal is being reproduced, it is of the same phase in both left and right channels.

Phase selectable circuit for use in a stereo demodulator

In a television signal processing apparatus, a phase-locked loop (PLL) is provided for detecting the audio information from the television signal and for providing a defect control signal which, when applied to compensation circuitry, reduces impulse noise effects in the video information. The PLL includes a phase detector, a lowpass filter (LPF) and a voltage controlled oscillator (VCO). The phase detector has a first input coupled to be responsive to the frequency modulated sound signal produced by the tuner, a second input coupled to be responsive to the output of the VCO and an output coupled to the LPF. The LPF provides a phase control signal to the VCO and provides the detected audio information. A signal mixer serving as a synchronous detector has first and second inputs coupled to the first and second inputs, respectively, of the phase detector and has an output for providing the defect control signal indicative of the amplitude variations of the frequency modulated sound carrier.

Sound signal and impulse noise detector for television receivers

A frequency translation phase-locked loop (PLL) is provided for detecting the audio information from a received television signal. The PLL includes a switching arrangement which, in a first position causes the loop to process the IF picture and sound carriers for detecting the audio information in an intercarrier type of detection method and, in a second position causes the loop to process the IF sound carrier for detecting the audio information without the use of the received picture carrier, in a 'separate' (split-sound) type of audio detection method.

Frequency translation phase-locked loop for separate or intercarrier

A frequency translation phase-locked loop (PLL) is provided for detecting the audio information from a television signal. A voltage controllable oscillator having a nominal oscillation frequency equal to the frequency difference between the intermediate frequency (IF) picture and sound carriers provides one input to a mixer and a substantially unmodulated picture carrier is supplied as the other input to the mixer. A phase detector has as its first input the output signal from the mixer and as its second input the sound carrier. A lowpass filter coupled between the output of the phase detector and a control input to the VCO completes the PLL. The detected audio information is provided at the output of the lowpass filter.

Growing community of inventors

Indianapolis, IN, United States of America

Abraham E Rindal