Abstract: A down-converter for processing frequency signals, preferably received, particularly digital, television signals, comprising two, preferably identical mixer stages (10a, 10b) for down-converting the signal, a local oscillator (12) controlling the mixer stages by a 90° phase shift, a complex filter (14) which couples the output signals of the mixer stages (10a, 10b) by means of a complex filtering method in such a way that the signal components outside a predetermined useful band are substantially suppressed, an adjusting device (13) for adjusting the frequency of the local oscillator (12) and a subsequent low-pass filter.

Abstract: A down-converter for processing frequency signals, preferably received, particularly digital, television signals, comprising two, preferably identical mixer stages (10a, 10b) for down-converting the signal, a local oscillator (12) controlling the mixer stages by a 90° phase shift, a complex filter (14) which couples the output signals of the mixer stages (10a, 10b) by means of a complex filtering method in such a way that the signal components outside a predetermined useful band are substantially suppressed, an adjusting device (13) for adjusting the frequency of the local oscillator (12) and a subsequent low-pass filter.

Abstract: Circuit arrangement for demodulating a video signal (IF signal) which is frequency-modulated on an intermediate-frequency carrier oscillation, including a first demodulation stage (a frequency or phase demodulator) for multiplicatively combining the IF signal with a carrier oscillation of a controllable oscillator and for supplying a first output signal, a second demodulation stage (a frequency or phase demodulator) for multiplicatively combining the IF signal with the carrier oscillation phase-shifted by a quarter period of the intermediate-frequency carrier oscillation, and for supplying a second output signal, a first filter stage for low-pass filtering the first output signal and for supplying a third output signal, a multiplier stage for multiplicatively combining the second output signal and the third output signal to form a fourth output signal, a superposition stage for forming a seventh output signal by additively combining a fifth output signal and a sixth output signal derived from the second outpu

Abstract: A circuit arrangement for demodulating the sound signals in a television signal is described, which circuit arrangement ensures a simple and low-cost structure, also for operation at different transmission standards.To this end, the circuit arrangement according to the invention includes an oscillation-generating stage which derives a (first) oscillation from a television signal (IF television signal) modulated on a first intermediate-frequency carrier oscillation, whose frequency corresponds to the frequency of an intermediate-frequency picture carrier oscillation in the IF television signal and encloses a phase angle of at least substantially 90.degree. with the picture carrier oscillation, a (first) mixer stage, a first input of which can receive the (first) oscillation, and a switching device for optionally applying the IF television signal or a sound signal (IF sound signal) modulated on a second intermediate-frequency carrier oscillation to a second input of the (first) mixer stage.

Abstract: Oscillator having first frequency-determining elements provided for a first oscillation frequency. In order to provide an oscillator, particularly for use in video signal processing, which can be switched and tuned to at least two oscillation frequencies, at least a second frequency-determining element is provided which can be connected to the first frequency-determining element for adjusting the oscillator to a second oscillation frequency.

Abstract: In a synchronous demodulator for demodulating a carrier signal modulated with a useful signal, the demodulator including a filter circuit (2) for selecting the carrier signal, a limiter (3) for generating an amplitude-limited reference signal from the carrier signal, a phase shifter (4) for shifting the phase of the reference signal through a phase angle of essentially 90.degree. with respect to the carrier signal, and a multiplier (5) for multiplicatively combining the modulated carrier signal with the phase shifted reference signal, a simple arrangement effectively suppresses interference phase modulations, in that a dc mixing product is supplied (via 8) by the multiplier (5) as a measure of the frequency deviation of the carrier signal from the pass frequency of the filter circuit (2) as a control signal to this filter circuit for the purpose of controlling the pass frequency.

Abstract: In a circuit arrangement for optionally connecting the outputs of a plurality of signal sources which produce signals consisting of d.c. and a.c. components to an input of a signal sink, an interference-free switching is accomplished by providing that all the signals supplied by the signal sources from their outputs.

Abstract: By means of a digital filter, the chrominance signal is separated from the digitized picture signal and is applied to a variable-gain amplifier which is formed by the series arrangement of a shift stage and a multiplier. The two stages are controlled by a control circuit which receives the maximum amplitude value of the color synchronizing signal, obtained in a digital manner. Depending on this amplitude value the position of the chrominance signal is shifted and thereafter multiplied in the multiplier by a factor of, for example, between 0.5 and 1. Acting thus, the gain factor is split into two sub-factors, one of which is an integral power of 2 and in this way the multiplier is utilized in a much more advantageous manner. The amplitude value of the color synchronizing signal is measured before the amplifier, so that the control is a forward control, none of the problems occurring with closed control loops now being present.

Abstract: A filter circuit for separating video and audio signals has an extra resistive element added. This forms a bridge circuit that greatly increases the attenuation of the audio signal in the video channel.