Abstract: A trace switch, operated at a line rate, is coupled to a line deflection winding and a trace capacitance for applying a trace voltage to the deflection winding to generate line scanning current in the deflection winding. A deflection retrace capacitance is coupled to the deflection winding for forming a deflection retrace resonant circuit during the line retrace interval to generate a deflection retrace pulse voltage. A modulator inductance is coupled to the trace switch and to the line deflection winding. A modulator switch applies a line rate, switched mode, modulation voltage directly to the modulator inductance to control the amplitude of the current in the modulator inductance at the end of the line trace interval. A modulator retrace capacitance is coupled by the modulator switch to the modulator inductance during the line retrace interval for forming a modulator retrace resonant circuit.

Abstract: A digital video signal processing circuit generates interlaced luminance and chrominance signals from interlaced composite color video signals. The interlaced luminance signal contains vertical detail information without peaking. Each of two progressive scan speed-up processors, controlled to operate in parallel, receives the interlaced luminance and chrominance signals. In each of the speed-up processors, the chrominance signals are time compressed and repeated to generate two lines of time compressed chrominance video for each line of interlaced chrominance video. Furthermore, in each of the speed-up processors, a vertical detail signal is regenerated that contains vertical detail information derived from the interlaced luminance signal. The vertical detail signal is nonlinearly processed to generate a vertical peaking signal that is combined with the vertical detail signal. A time compression stage speeds up the peaked vertical detail signal to a double line rate.

Abstract: A signal overload circuit for use in e.g. a digital TV receiver includes a piecewise linear weighting circuit which weights samples of greater magnitude proportionately more heavily than samples of lesser magnitude. The weighted samples are applied to an accumulator, and the accumulated value over a field interval is compared to an overload reference value to generate an overload output signal which is combined with other gain factors for application as the common gain control signal to a common amplifier. The overload detector is coupled in a feedback loop around the common amplifier. In order not to defeat the function of the other gain factors, the overload detector is programmable and its sensitivity is made responsive to the other gain factors.

Abstract: A color television receiver with luminance and chrominance signal channels includes an automatic kinescope beam current limiter, an automatic white level drive control network, and an automatic black level bias control network. A switching network is timed to operate such that a control signal developed by the beam current limiter is coupled to the luminance channel during normal picture intervals, but is decoupled from the luminance channel during both white level drive control intervals and black level bias control intervals. The beam limiter control signal is continuously coupled to the chrominance channel, independent of the operation of the switching network, to permit chrominance output bias offset errors produced by beam limiter action to be sensed and compensated for by the automatic bias control network.

Abstract: A television receiver includes a character generator for producing alphanumeric data or graphic symbols to be displayed along with a received video signal. An oscillator, locked to a multiple of the color subcarrier frequency of the video signal, supplies a clock signal to the character generator for controlling the timing of displayed character elements. A delay circuit coupled to the character generator and controlled by a measuring circuit imparts an effective delay to the character elements in proportion to the time difference between a transition of the clock signal and the horizontal synchronizing component of the video signal. The delay compensates for temporal and spacial distortions of displayed characters which otherwise would tend to occur when the ratio of the color subcarrier frequency with respect to the horizontal line rate of the video signal is "non-standard" (e.g., other than 910:1 for NTSC or 1135:1 for PAL).

Abstract: A 7 bit digital signal is dithered by adding a low-level digital dithering signal comprised of alternating 1's and 0's, and by truncating the product to 6 bits. To dedither, an EXCLUSIVE-OR gate compares the previous and the current values of the least significant bit of the 6 bit dithered signal. If they are dissimilar, it outputs a "1". Otherwise, it outputs a "0". The output of the EXCLUSIVE-OR gate is ANDed with the dithering signal. If the dithering signal and the output of the EXCLUSIVE-OR gate are both one, then the 6 bit dithered signal is decremented. Otherwise, the 6 bit dithered signal is passed unchanged. The decremented-or-not 6 bit dithered signal is combined with the bit generated by the EXCLUSIVE-OR gate to produce the final 7 bit reconstituted signal.

Abstract: Plural phase detectors in a progressively scanned television receiver measure the phase of the receiver video speed-up memory read and write clocks with respect to the double line-rate horizontal sweep signal of the display. Delay means are provided for delaying the video signal recovered from the memory as a function of the difference between the read and write clock phase measurements each time the memory is read. The delay is effective for minimizing visible artifacts which otherwise may tend to occur when displaying "non-standard" video signals wherein the ratio of the color-subcarrier frequency to the line-frequency of the incoming video signal differs from a given broadcasting standard.

Abstract: A digital-to-analog converter system includes two DAC's operated in ping pong fashion with their analog output signals linearly summed. To preclude bandwidth limiting inherent in the summing operation the applied digital input signal is preconditioned in accordance with the transfer function 1/(1+Z.sup.-1).

Abstract: A digital hue correction circuit for correcting the color of digital TV chrominance signals includes a pipelined divider arranged to divide the smaller of the magnitudes of I and Q color mixture signals by the larger of the magnitudes of the I and Q signals to produce quotients representing tangents over the range of zero to 45 degrees for chrominance angles occurring over the range of zero to 360 degrees. The polarity bits of the I and Q signals and the polarity bit of the difference of the magnitudes of I-Q are encoded to transpose the zero to 45 degree angle tangent values over the range of zero to 360 degree angles. The transposed tangent values address a memory programmed with all negative hue correction coefficients representing the sines and cosines of angles by which the chrominance vector is to be rotated to effect hue correction.

Abstract: A signal processing apparatus includes a scaling device for increasing the magnitude of a signal from a source to better use the dynamic range of processing apparatus, and to reduce the effects of noise and error sources. This is particularly useful in a television receiver where the maximum magnitude of the (B-Y) chrominance signal component of a composite video signal is smaller than that of the (R-Y) chrominance signal component. To provide improved resolution of the (B-Y) signal components, a gain scaling arrangement increases the magnitude of the (B-Y) signal component to more closely approximate that of the (R-Y) signal component. In a TV receiver having digital signal processing apparatus, a digital multiplier scales the digitized (B-Y) signal component thereby to reduce the errors inherent in processing digital data having a limited number of bits, especially where such processing includes rounding or truncating operations which can introduce additional errors or decrease resolution.

Abstract: A color television receiver with luminance and chrominance signal channels includes an automatic kinescope beam current limiter, an automatic white level drive control network, and an automatic black level bias control network. A switching network is timed to operate such that a control signal developed by the beam current limiter is coupled to the luminance and chrominance channels during normal picture intervals, decoupled from at least the luminance channel during white level drive control intervals, and coupled to at least the chrominance channel during black level bias control intervals.

Abstract: Digital representations of analog signals are limited in resolution accuracy by the number of bits in the digital output signal of an analog-to-digital converter which limits the number of analog output levels produceable by a digital-to-analog converter. The apparent resolution accuracy can be improved, however, by the addition of two "dithering" signals, one at a lower frequency and one at a higher frequency, to increase the number of transitions of the least significant bit (LSB) of the digital signals. In a television receiver employing digital signal processing apparatus, dither signals having magnitudes equivalent to 1/2 and 1/4 LSB and at frequencies related to the TV line frequency and the color subcarrier frequency are preferred.

Abstract: An S-correction circuit for a video display apparatus provides switchable amounts of correction in a given line deflection interval in order to satisfy the requirements of cathode ray tubes having large deflection angles or complex curvature faceplates. A second S-shaping capacitor is coupled in parallel with the main S-shaping capacitor by action of a switching transistor. The time at which the transistor is switched may be controlled, for example, by modulating the switching point at a vertical rate, in order to increase the flexibility of the correction circuit.

Abstract: A regulated switched-mode power supply for a television receiver utilizes a high voltage power transformer. A transformer primary winding, energized in response to a pulse width modulated signal, energizes electrically isolated load circuit windings via transformer action to transfer energy from an unregulated voltage source. A supplemental transformer winding, magnetically coupled to the primary winding, transfers additional energy to the load circuits to maintain accurate load circuit voltage regulation under all receiver operating conditions.

Abstract: The present invention provides for the generation of digitally dithered digital signals which can have an apparent quantizing resolution unaffected by truncation of the least significant bit. The truncated digital signal is dithered in an ordered fashion by adding thereto a bit developed in response to one condition of the truncated bit and is not dithered in response to another condition thereof. The original digital signal can be reconstructed by combining successive samples of the truncated digital signals. One feature of the present invention provides a truncation of digital signals.

Abstract: A beam current limiting (BCL) control apparatus for a digital television system includes a control unit for controlling the reference voltage for the analog-to-digital converter (ADC), which converts the analog composite video signal, including both luminance and chrominance components, to corresponding digital samples, so as to reduce excessive beam currents. A switching circuit prevents the reference voltage from being changed in response to the beam current during horizontal blanking intervals so as to inhibit interference with digital synchronization component detection and automatic chrominance control. A clamping circuit is coupled to the ADC to inhibit the conversion of portions of the composite video signal extending from the black level (0 IRE units) to the sync tips from being affected by the BCL operation. This inhibits the BCL operation from adversely affecting the reproduction of details in dark portions of an image.

Abstract: A color television receiver includes a network for automatically limiting excessive kinescope beam currents developed in response to video signal image information, and a white balance control network for automatically controlling the white level drive (gain) characteristics of the kinescope in response to a white drive reference signal applied to the video signal path during given measuring intervals. A control signal developed by the beam current limiter network, otherwise applied to the video signal path, is decoupled from the video signal path during the white level measuring intervals to prevent distortion of the white level control function.

Abstract: A scan synchronized push-pull power supply for a television receiver has a source of direct voltage coupled to the primary winding of a power transformer. A first controllable switch of the power supply includes a main current path and a control terminal for controlling conduction in the main path. A second switch of the power supply includes a main current path with first and second terminals thereof. The main paths of the two switches are coupled to the primary winding in a push-pull arrangement. A deflection rate signal that is synchronized with scanning current generation is applied to the control terminal of the first switch to alternately switch conduction of its main current path between conductive and nonconductive states during each deflection cycle in synchronism with the scanning current generation.

Abstract: To regulate a supply voltage for a television receiver load circuit, such as the ultor voltage for a high voltage circuit, the primary winding of a transformer is coupled to a source of alternating input voltage for developing an alternating polarity voltage across a secondary winding of the transformer. A saturable reactor includes a magnetizable core with a reactor winding wound around the core. The reactor winding and the transformer secondary winding are conductively coupled to develop an alternating polarity voltage across the reactor winding. The transformer secondary winding is magnetically isolated from the saturable reactor such that the magnetic flux flowing in the reactor core does not link the transformer secondary winding. A capacitor is coupled to the saturable reactor winding for developing a circulating current that aids in magnetically saturating a portion of the reactor core associated with the reactor winding.

Abstract: A switched mode power supply for a remote controlled television receiver incorporates a degaussing circuit having a relay that is required to be energized in order to permit operation of the degaussing circuit. Power to energize the relay is derived from a power supply switch transistor protection circuit which removes residual stored energy from the power transformer primary winding. This stored energy is used to charge a capacitor during the time the switch transistor is nonconductive. The capacitor is discharged to provide current to energize the deguassing circuit relay in order to permit ac mains current to flow through the degaussing coil.