Rca Inc.

Walter G Gibson

Thomas Y Chen

Frank C Liu

Max Ward Muterspaugh

Michael Allen Plotnick

Theodor M Wagner

James H Doty, Ii

Roy M Christensen

Roger D Thompson

James M Ferguson

An amplifier having a resonator coupled between input and output terminals thereof supplies a dot clock signal to a character generator in a television receiver. A feedback control circuit supplies DC bias to the resonator during blanking intervals that preceed lines of characters to be displayed to ensure a consistent starting phase for oscillations, removes the DC bias and supplies operating power to the amplifier during a portion of the active video period of each displayed line for sustaining the oscillations and automatically inhibits the supply of amplifier power at the end of each active line of characters to thereby provide three oscillator operating modes of PRIMED, RUNNING and OFF so as to minimize overall power consumption for the oscillator for each field of displayed characters.

Start-stop oscillator having fixed starting phase and minimized

Video disc track numbers are conveyed during each video line by means of a quadrature phase shift keyed data carrier recorded along with the picture and sound carriers on a video disc. Upon playback, the data sequence is processed to identify tracking errors occurring within each video field to thereby enable immediate correction of disc tracking errors on a line-by-line basis thus minimizing picture and sound interruption caused by intra-field tracking errors.

Video disc encoding and decoding system providing intra-field track

A filter limits the bandwidth of a caption video signal in a video disc player to minimize color beats when the caption signal is displayed along with a picture video signal on a television receiver. The filter delay, which would otherwise cause offset between the caption and an associated background signal used to enhance visibility of the caption, is compensated for by extending the time duration of each occurrence of the background signal by a multiple of the filter delay.

Video player with caption generator having character background

A signal source continuously produces a horizontal timing signal proportional to the line rate of a recovered composite video signal. A vertical timing unit coupled to the source continuously produces a vertical timing signal proportional to the field rate of the video signal. An error detector processes data words present in the vertical interval of the composite video signal to provide a data status signal indicative of the validity of each processed data word. The data status signal is applied to the vertical timing unit for synchronizing the vertical timing signal with the vertical synchronizing component of the composite video signal and rendering the vertical timing signal substantially immune to noise which might accompany the composite video signal.

Video disc player having vertical timing signal generator

A video signal is separated into a broad area luminance signal having attenuated vertical and horizontal detail components and a composite detail signal having horizontal and vertical detail components in a predetermined ratio. The broad area luminance signal is combined with the composite detail signal in desired proportions to provide continuous control of the picture detail from soft to sharp in all directions of reproduced images.

Vertical and horizontal detail signal processor

An automatic fine tuning (AFT) circuit is provided which generates an AFT control signal in response to a video intermedate frequency (I.F.) signal. The I.F. signal is supplied to the input of a current source amplifier, which provides current signals of like phase relationship to a discriminator network. The discriminator network is comprised of two tuned circuits, one of which is resonant at a frequency below the desired frequency of the I.F. picture carrier, and the other resonant at a frequency above the desired frequency. The tuned circuits develop voltage variations which vary differentially in magnitude in response to the frequency deviation of the I.F. picture carrier from its desired frequency. The differentially related voltages are detected by two peak detector networks for use as AFT control signals. The current source amplifier and peak detector networks may be conveniently fabricated on a single I.C. chip. The tuned circuits are coupled to the current source amplifier and peak detector networks through two external I.C. terminals.

AFT Circuit

In a video disc playback system non-linear intermodulation distortions are effected during playback by the pick-up stylus. These distortions cause disturbing visual beats in the reproduced images. A first signal path at the output of the pick-up circuitry transfers the main video signal with negligible phase shift over a given band of frequencies. A second signal path which parallels the first path effects a modulation of the video signals by the interferring signals (i.e., sound signals). The signals from the first and second paths are combined to effect a substantial removal of the interfering intermodulation products.

Non-linear aperture correction circuit having a signal bypass arrangement

A signal separation network is provided which accomplishes the functions of a sound take-off network and intercarrier sound trap in a single network. A common detector produces detected composite video and intercarrier sound signals. Circuitry is provided for processing the composite video signal, and a separate circuit is provided for processing sound information. The signal separation network has an input responsive to the detected composite video and intercarrier sound signals, a first output terminal coupled to the input of the video processing circuitry, and a second output terminal coupled to the input of the sound processing circuitry. The network is characterized by a transfer function which exhibits a dominant zero approximately at the intercarrier sound frequency at the first output terminal, which provides trapping of the intercarrier sound signal in the path to the video processing circuitry. The network is also characterized by a transfer function at the second output terminal which exhibits a dominant pole substantially at the intercarrier sound frequency and a zero at a lower frequency so as to peak the response at the second terminal around the intercarrier sound frequency. The intercarrier sound signal is therefore prefiltered by the bandpass characteristic at this second terminal and is then applied to the sound processing circuitry. The network may be arranged in either a series tuned or a bridged-T configuration, and may also be arranged so as to exhibit a zero in the transfer function at the second output terminal which provides attenuation of mid-band video signals in the sound channel.

Signal separation networks

A comb filter apparatus is provided with means for equalizing the delayed and undelayed signal levels at the inputs to the adding or subtracting matrix, whereby maximum cancellation and reinforcement of the undesired and desired signals is effected. An input signal is coupled to an additive or subtractive matrix by way of an undelayed signal path and a delayed signal path. The delayed and undelayed signals at the inputs to the matrix are each coupled to a detector by way of a bandpass filter, which pass frequencies at which the combing of the signal is most critical. The detectors detect the levels of the input signals and apply the detected levels as two inputs to a difference circuit. The two signal levels are compared in the difference circuit to develop a gain control signal. The gain control signal is utilized to control the gain of a gain controllable stage which is coupled in series with one of the signal paths thereby equalizing the levels of the input signals to the combining matrix.

Comb filter equalization circuit

A selectivity network is provided for a synchronous detector, a reference signal circuit, and an AFT circuit. The selectivity network comprises a first tuned circuit coupled across two terminals of the reference signal circuit and tuned to the desired frequency of the I.F. picture carrier. A second tuned circuit is lightly coupled to the first tuned circuit and is coupled across two inputs of the AFT circuit to provide a frequency dependent phase-sifted reference signal to the AFT circuit. The first tuned circuit includes a trap circuit tuned to provide attenuation about a frequency intermediate the frequency of a sound carrier and that picture signal sideband frequency which, upon detection, results in a video signal corresponding to the intercarrier sound second subharmonic frequency. The trap in the reference signal tuned circuit minimizes quadrature distortion in the reference channel and the resultant harmonic distortion in the video signals, which causes sound buzz. The frequency notched reference signal is applied to the AFT tuned circuit, which causes a balancing of the pull-in range of the AFT circuit about the desired picture carrier frequency, thereby immunizing the AFT circuit against noise-pulling. The frequency notch in the AFT circuit at the indicated frequency also minimizes AFT effects of a frequency offset co-channel sound carrier, allowing the automatic acquisition of signals which are offset in frequency toward the lower adjacent channel.

Television signal processing system

A wideband signal delay line network comprises at least respective end terminals and an intermediate terminal. One of the end terminals and the intermediate terminal are coupled to a source of wide bandwidth composite signal, and are arranged to provide a signal time delay therebetween substantially equal to NT/2, where N is an odd integer and T is the reciprocal of a selected frequency at which it is desired to provide a desired amplitude response (e.g., attenuation or null) of the composite signal. A combined signal appearing at the intermediate terminal is representative of the composite signal coupled to the intermediate terminal and the composite signal coupled to the one end terminal, the latter signal being delayed relative to the composite signal coupled to the intermediate terminal. The combined signal is coupled via the remaining end terminal to utilization means. An illustrative utilization means comprises an amplitude peaking circuit accepting signals from the remaining end terminal and additional intermediate terminals of the delay line network.

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Princeton, NJ, United States of America

Walter G Gibson