Abstract: The circuit for the digital filtering of IF intermediate frequency video signals comprises an A/D (analog/digital) converter and a Nyquist filter (N); an analog prefilter, suitable for selecting the desired channel, is placed upstream of the A/D converter. The Nyquist filter (N) is a digital filter placed downstream of the A/D converter, composed of two IIR filters (15, 16) placed in cascade, one (16) of these IIR filters being produced in non-causal form with spectrum conjugate to the other IIR filter (15) produced in causal form, and of an FIR filter (17) in series, for correcting the IIR filters.

Abstract: A digital receiver includes a mixer stage receiving a carrier signal S(t) and delivering an intermediate frequency signal S.sub.FI (t) to a demodulation stage. The mixer stage is furnished with a PLL circuit for generating a signal at a given frequency. The digital receiver further includes a phase noise digital correction stage for tapping off a noise signal .phi..sub.n (t) generated by the PLL circuit in the mixer stage and for compensating the noise signal .phi..sub.n (t) in the demodulation stage.

Abstract: A method for digitizing intermediate frequency (IF) video signals, of acceptable cost, in which the signal from a tuning device is pre-filtered and amplified. This pre-processed signal is fed to a sample and hold circuit whose bandwidth covers the range up to at least the maximum intermediate frequency, and the sampled signals output from the sample and hold circuit are fed to an analog-to-digital converter whose dynamic resolution is sufficient only up to about half of the sampling frequency. The invention is applicable to the processing of digital IF video signals.

Abstract: The disclosure relates to a A digital filtering system of a signal, including a calculation circuit that calculates the average increase in amplitude .DELTA.X.sub.av (n) between two samples X(n), and an "output signal (Y(n)) circuit" that calculates a mean, weighted by a coefficient a, of the sample to be filtered X(n) and the previous sample Y(n-1) algebraically increased by said average increase in amplitude .DELTA.X.sub.av (n). The invention is applicable to digital signal processing.

Abstract: There is disclosed an A/D conversion circuit comprising a first A/D converter for receiving an input signal of the A/D conversion circuit and providing a digital output signal, the first A/D converter having a restricted resolution, wherein the input signal passes through delay means to a first input of a subtraction stage. A first D/A converter operating on the output signal of the first A/D converter generates an analog output signal and feeds the analog output signal via an adding stage to a second and subtracting input of the subtraction stage, wherein the input signal of the first D/A converter passes through a correction algorithm unit to a second D/A converter. The output signal of the second D/A converter is fed to a second input of the adding stage, wherein the correction algorithm unit provides empirically determined data for D/A conversion correction. A low pass filter coupled to the output of the subtraction stage provides a low pass filtered and amplified output signal.

Abstract: A method of digitization of an intermediate frequency signal having a bandwidth that can change from one standard to another and of which one of the frequency limits of this band is substantially constant, wherein before converting the analog signal into a digital signal, the signals of the channels (S.sub.if.sup.N+1, S.sub.if.sup.N-1) adjacent to the frequency band of the signal to be digitized are eliminated in three stages: in a first stage, the signals (S.sub.if.sup.N+1) of channels adjacent to said substantially constant frequency limit are eliminated by filtering; in a second stage, the signal to be processed is transposed in frequency so that in the transposed signal the variable frequency limit of said band of the signal to be digitized has a substantially constant value; in a third stage, the signals of channels adjacent to the transposed signal are eliminated by filtering. The invention is applicable to the processing of digital IF video signals.

Abstract: A video signal is applied to a kinescope having scan velocity modulation for improving picture sharpness in the vertical direction. Pictures from video signals of a type having non-interpolated and vertically interpolated lines (e.g., interlace-progressive up-converted) will tend to exhibit a significant reduction of sharpness in vertical direction. This problem is corrected by applying scan velocity modulation only to the interpolated lines of the video signal. Furthermore, the vertical deflection is restricted to horizontal structures or real vertical transitions, respectively. In order to have a high noise immunity of this sensitive processing, the resulting luminance amplitude of the shifted line as well as the vertical deflection is controlled to be strongly dependent on the current video signal (soft decision).

Abstract: For progressive scan conversion adjacent fields cannot be used to interpolate moving objects because motion blur will be introduced then. The most simple solution is to insert the average of the two adjacent lines for each missing line. A technique superior to vertical averaging represents the DIAG3 algorithm, where according to the found minimum gradient the orientation of the interpolation filter is chosen. But in case of high diagonal frequencies interpolation errors will occur. Therefore it is tested if the reconstructed pixel value exceeds or falls below the pixel values in the two adjacent lines of the input signal. If this happens, instead of one of the detected diagonal directions the vertical direction is taken, it.e. a vertical averaging is carried out.

Abstract: Visual artifacts, normally characteristic of interpolated images, are minimized by a method of adaptive interpolation in which pixel values of a current line to be interpolated are determined from respective values of vertically adjacent pixels of adjacent lines in a current field. The values are adaplively weighted according to one or more gradients of respectively located pixel values of one or more temporally adjacent fields thereby providing an interpolated image having improved sharpness, no temporal lag, and no switching artifacts.

Abstract: Large format TV tubes must produce a high peak brightness in order to be acceptable to the user. This results in a large beam current in bright areas of the picture and in a subsequent defocusing of the resulting spot on the display and in a loss of the sharpness of vertical and horizontal transitions. The apparent sharpness of a vertical transition is gained by modifying the deflection of the TV receiver such that, at vertical transitions, the line on the bright side of the transition is deflected away from the transition region. Advantageously, the amount of vertical scan modulation corresponds to a multi-level control signal and depends on the grey levels of the transition.