U.S. Philips Corporation

Otto L Warmuth

Walter H Demmer

Johannes G Raven

Claus Dieter Grzyb

Martin H Johanndeiter

Rolf-Dieter Gutsmann

Wolfgang Schwartz

Rolf D Gutsmann

Peter E Draheim

Ingolf B Heinemann

Detlef Deutschmann

Kurt-Joachim Johannes

Norbert A Bergs

A digital circuit which receives a serial input signal and which suppresses fast signal variations. The digital circuit includes an integrator circuit (1) which generates a multi-bit signal by integration of the serial input signal. The output signal of the integrator circuit is applied to an evaluation circuit (2) which generates a serial output signal which assumes a first state when the multi-bit signal exceeds a first threshold value and a second state when the multi-bit signal is below a second threshold value.

Digital circuit for suppressing fast signal variations

The invention relates to a digital low-pass filter which effects a frequency reduction by a factor which is equal to the ratio w/2 between the frequency of the input signal and the frequency of the output signal, wherein w is an odd integer. The input signal is applied to m series-arranged registers. The input signal of the first and the output signals of all the registers are multiplied by coefficients. A change-over switch precedes an input of each multiplier, the change-over switch switching the coefficients symmetrically. The switching instants are always symmetrical relative to a reference sampling instant. The filter is particularly suitable for use in video signal processing, to reduce negative influences of an analog-to-digital converter.

Digital low-pass filter with improved frequency reduction characteristics

In a circuit arrangement for converting an analog picture signal, which corresponds to consecutive fields, into an amplitude-discrete output signal, which, in a comparison stage, compares the picture signal to a plurality of reference values and produces an amplitude-discrete intermediate signal at an output, a significant simplification of the circuit cost and design effort is accomplished with, at the same time, an improvement in the error cancellation by the fact that the change in the positions of the values of the picture signal and the reference values relative to each other corresponds to the sum of a fraction and a first integral number of value intervals.

Method for converting an analog picture signal into an

A color television signal receiver includes a circuit arrangement for demodulating an NTSC-encoded chrominance signal available as a sequence of digital values. An oscillator circuit (33), which has an accumulator (16) and a waveform converter (31) produces two sine-shaped reference signals which are applied to a demodulator circuit (2). The accumulator (16) includes a register (18) and a (first) modulo-adder (17). A phase comparator circuit (12) controlling the phase of the reference signal receives at least one demodulated signal during the occurrence of the color synchronizing signal. The sawtooth-shaped accumulator output signal is added in a second adder (26, 38) during a first switching position of a change-over switch (23, 34) to an adjustable value and is thereafter applied to the waveform converter (31). In the second switching position of the change-over switch (23, 34), which only occurs during the occurrence of the color synchronizing signal, the accumulator output signal is applied unchanged to the waveform converter (31).

Television receiver including a circuit arrangement for demodulating an

For determining the half-cycle durations of the input signal which is presented as a sequence of sampled values, its zero crossings are approximated by lines which interconnect the two sampled values of different signs on both sides of the zero crossing. The half-cycle duration is derived from the number of sampled values within a period, i.e. between two consecutive zero crossings, and from the time intervals at the beginning and end of each half-cycle determined by the intersection of the approximation line with the axis. The time intervals at the beginning and end of each period are corrected for a more accurate determination of the duration and the time intervals during which the values of the individual half-cycle durations are stored, are made to approximate to these half-cycle durations. The instantaneous frequency of the input signal is determined from the values of the half-cycle durations which have thus been shifted in time by forming the reciprocal.

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Hamburg, Germany

Otto L Warmuth