Siemens Aktiengesellschaft

Siemens Aktiengesellschaft Ag

Richard Stepp

Josef Fenk

Jurgen Wondra

Hans Fiesel

A circuit configuration for intermediate frequency demodulation for a video signal processing device includes an intermediate frequency filter to which an input signal converted to an intermediate frequency is delivered, and a mixer for demodulation with a simulated video carrier. In a further branch, the video carrier is eliminated from the input signal by a bandpass and converted in an oscillator into reference signals being mutually phase offset by 90.degree.. A phase tracker ensures that the phase and frequency of the simulated video carrier are correct relative to the signal to be demodulated. The phase tracker contains in each of two branches a mixer and a low pass, through which a component separation of the video signal to be demodulated is carried out. The reference signals are weighted in further mixers with determined equisignal components and combined into the simulated video carrier.

Circuit configuration for intermediate frequency demodulation and device

A filter with adjustable edge steepness includes input terminals for applying a signal to be filtered. One of the input terminals is connected to a reference potential. A signal-forming device is connected to the input terminals for forming a first signal and a second signal from the signal to be filtered. The signal-forming device adjusts a difference between the first signal and the second signal. A subtraction device is connected to the signal-forming device for forming a differential signal from the first signal and the second signal. A frequency-dependent device has an input terminal connected to the subtraction device, an output terminal for supplying another signal, and a filter transfer characteristic to be delivered to the differential signal. An addition device has an output and is connected to the signal-forming device and to the output terminal of the frequency-dependent device for forming a summation signal at the output from the first signal and the other signal. One output terminal is connected to the output of the addition device and another output terminal is connected to the reference potential.

Filter with adjustable edge steepness

A four-quadrant multiplier based on a Gilbert cell is utilized to multiply several signals by a similar signal. The transistors in two pairs of coupled differential amplifiers of one input terminal of the inner multiplier that is activated like a Gilbert cell by way of a diode-and-transistor section have several emitters. Each pair of emitters in the right and the left branch of the miltiplier can be oppositely activated by way of a source of variable current or by way of a series of a transistor and a source of current. To process square-wave signals, the source of variable current is a source that can be engaged and disengaged by I.sup.2 L gates.

Multiple-input four-quadrant multiplier

A method and circuit arrangement identifies the presence or absence of known frequencies in an input signal composed of a plurality of frequencies, whereby a frequency generator controlled by a reference frequency generates four switch signals having frequencies dependent upon the frequency to be identified and having a phase difference of 90.degree. and respectively one switch signal is mixed with the input signal in a respective mixer. The respective mixer products of two mixers are additively combined and are filtered through a respective filter for filtering AC components out, and the DC voltage component contained in the respective mixer product given the presence of the known frequency is evaluated with respect to the amplitude.

Method and circuit arrangement for identifying the presence or absence

A method and circuit for determining the presence or absence of a frequency of known value in an input signal composed of several frequencies employ a frequency generator, to which a stable reference signal is supplied, for generating two switching signals having a frequency which is the same as the known frequency and a phase difference of 90.degree.. The input signal is supplied to two mixers, to which the out-of-phase signals from the frequency generator are respectively supplied. The products of the two mixers are supplied to respective filters for filtering out ac components, and the respective amplitudes of the remaining dc voltage components of the respective mixed products are evaluated, the result of the evaluation indicating the presence or absence of the known frequency in the input signal.

Method and circuit for determining the presence or absence of at least

An integrable bipolar oscillator circuit, includes four transistors of the same conductivity type, four resistors, three constant current sources having base points and outputs, a reference potential terminal connected to the base points of each of the constant current sources, a supply potential terminal, and a frequency-determining feedback member, the output of the first constant current source being connected to the emitter of the first transistor and to the base of the second transistor, the output of the second constant current source being connected to the emitter of the third transistor and to the base of the fourth transistor, the emitters of the second and fourth transistors being connected to the output of the third constant current source through a given connection, the collectors of the first and third transistors being directly connected to the supply potential terminal, the first and second resistors each being connected between a respective one of the collectors of the second and fourth transistors and the supply potential terminal, the fourth resistor being connected between the base of the first transistor and the collector of the fourth transistor, the third resistor being connected between the base of the third transistor and the collector of the second transistor, the frequency-determining feedback member being connected between the base of the third transmitter and the base of the first transistor, and an oscillator voltage being supplied between the emitters of the first and third transistors.

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Munich, Germany

Richard Stepp