Abstract: A harmonic rejection mixer for carrying out a frequency translation of a mixer input signal having a mixer input frequency, the mixer including an up-conversion mixer for generating an intermediate signal by multiplying the mixer input signal with a first local oscillation signal having a first local oscillation frequency, and a down-conversion mixer for generating a mixer output signal by multiplying the intermediate signal with a second local oscillation signal having a second local oscillation frequency. The first local oscillation frequency and the second local oscillation frequency are greater than the mixer input frequency. The first local oscillation signal is an l-time oversampled sine wave and the second local oscillation signal is an m-time oversampled sine wave.

Abstract: A harmonic rejection mixer for carrying out a frequency translation of a mixer input signal having a mixer input frequency, the mixer including an up-conversion mixer for generating an intermediate signal by multiplying the mixer input signal with a first local oscillation signal having a first local oscillation frequency, and a down-conversion mixer for generating a mixer output signal by multiplying the intermediate signal with a second local oscillation signal having a second local oscillation frequency. The first local oscillation frequency and the second local oscillation frequency are greater than the mixer input frequency. The first local oscillation signal is an l-time oversampled sine wave and the second local oscillation signal is an m-time oversampled sine wave.

Abstract: A first switching circuit has an input for receiving a first input signal, and a second switching circuit has an input for receiving a second input signal. A node is connected to receive outputs from both the first and second switching circuits. A filter receives an unfiltered signal from the node to generate an output signal. A circuit is provided to alternately actuate the first and second switching circuits during a transition time period so as to smoothly transition the output of the filter between the first and second input signals. At least one of the first and second input signals is a time-varying analog signal. The smooth transition between the first and second input signals has a shape determined by pulse width and frequency characteristics of pulses output by the circuit to alternately actuate the first and second switching circuits. The shape may include a linear ramp, an S-shaped curve, a parabolic curve and a hyperbolic curve.

Abstract: A method of signal compression of a signal to reduce the large dynamic range, for example, of the output signal of a CD player in such a way that soft passages of a piece of music are reproduced in somewhat louder manner and very loud passages of a piece of music some are reproduced in somewhat less loud manner. The signal compression circuit used therefor can be integrated completely. The audio signal is fed over a volume control, which can be adjusted by the user, and to this end, a digital setting signal in accordance with the adjustment made on the user side, is supplied via a bus line. When the audio signal is strongly increasing, a tracking signal is formed of said signal, with the amplitude thereof being dependent on the medium amplitude of the audio signal. A window comparator compares the tracking signal with a reference value, as a consequence of which the contents of the up/down counter are reduced. This reduced value is added via an adder to the digital setting signal for the volume control.

Abstract: An SC filter with intrinsic anti-alias function for adjustably decreasing or increasing the amplitude of audio signals in a predetermined frequency range. The SC filter includes a filter module having an RC network with at least one frequency-response-determining RC member whose resistor component R is realized in SC technology. The SC filter also includes a setting means connected to the filter module such that its setting determines the frequency response of the SC filter. The setting means also renders possible a neutral setting in which the effective audio signal path of the SC filter circumvents the filter module so that no decrease or increase of the amplitude of individual frequency portions takes place. An anti-alias low pass filter unit is connected into the audio signal path when the setting means is not set to the neutral setting and the anti-alias low pass filter unit is not located in the audio signal path when the setting means is set to the neutral setting.

Abstract: A method of signal compression of a signal to reduce the large dynamic range, for example, of the output signal of a CD player in such a way that soft passages of a piece of music are reproduced in somewhat louder manner and very loud passages of a piece of music some are reproduced in somewhat less loud manner. The signal compression circuit used therefor can be integrated completely. The audio signal is fed over a volume control, which can be adjusted by the user, and to this end, a digital setting signal in accordance with the adjustment made on the user side, is supplied via a bus line . When the audio signal is strongly increasing, a tracking signal is formed of said signal, with the amplitude thereof being dependent on the medium amplitude of the audio signal. A window comparator compares the tracking signal with a reference value, as a consequence of which the contents of the up/down counter are reduced. This reduced value is added via an adder to the digital setting signal for the volume control.

Abstract: In an integrated circuit comprising a so-called “switched” capacitor, the latter is switched by a parallel circuit of two complementary switching transistors having mutually complementary switching pulse trains. Due to parasitic effects during this switching operation, disturbing offset voltages arise at the switched capacitor. In order to avoid such offset voltages, the edges of the one switching pulse train are shifted in time with respect to the corresponding edges of the complementary switching pulse train. To this end, a switching pulse generator contains a delay member fed with a control signal which is formed by means of a constant reference voltage using a dummy or simulation of that circuit that contains the switched capacitor.

Abstract: A switched capacitor wherein one of the plates of the capacitor to be switched is fed with the input signal via a transistor switch receiving as control signal at the gate thereof a pulse train with predetermined frequency. For compensating the parasitic capacitance of the transistor switch, a compensation component is located between the transistor switch and the capacitor to be switched. This compensation component is formed as an incomplete transistor structure, such as only 1/2 of a transistor, has a drain region in common with transistor switch and has an insulated gate. The parasitic capacitance of the compensation component thus is established mainly by the capacitance between the insulated gate and the drain region and thus corresponds to the parasitic capacitance of the transistor switch, whereby complete compensation with optimized charge transfer is achieved.

Abstract: A method for offset compensation of a signal processing circuit in whose signal path a circuit configuration with offset is disposed, wherein the circuit configuration with offset is temporarily decoupled from the signal path of the signal processing circuit and meanwhile held strictly in a dc mode; a compensating dc voltage is added to the output dc voltage occurring at the output of the circuit configuration with offset in the dc mode, said compensating dc voltage being varied until the cumulative value of output dc voltage and compensating dc voltage has became zero; the circuit configuration with offset is then coupled into the signal path again; andfrom then on the compensating dc voltage occurring at the cumulative value zero is permanently added to the output signal of the circuit configuration with offset until a new offset compensating process is performed.

Abstract: An audio signal processor is disclosed which has at least one audio signal input and at least one audio signal output as well as at least one control input, and an audio signal processing unit connected between audio signal input and audio signal output, the audio signal processing unit having a programmable indicator tone generator circuit to be driven via the control input and whose indicator tone signal is switched to the audio signal output in accordance with the state of the control input.

Abstract: For eliminating the emphasis given an audio signal in the transmitter, an audio signal processor of an audio device (e.g., a car radio) contains a low-pass filter. In order to attenuate the spurious higher-frequency signal fractions in case of poor reception and accordingly low received field strength, the cutoff frequency of the low-pass filter is shifted in the direction of lower frequencies in accordance with a received field strength signal when the field strength becomes lower. In order to avoid external adjusting components and save pins on the IC chip, the field strength signal is supplied to an analog-to-digital converter and the latter supplies a digital signal to a low-pass filter whose cutoff frequency is variable. For this purpose the low-pass filter contains a number of integrated components one of which is connected or disconnected by a digit place of the digital signal in each case.

Abstract: An electric signal processing circuit with an operational amplifier having a signal input, a feedback input and a signal output, and a nonlinear circuit device having a characteristic with a distortion-producing nonlinearity and located in the input signal circuit or in the feedback circuit of the operational amplifier, wherein a compensating circuit device having a characteristic with generally the same nonlinearity as the characteristic of the nonlinear circuit device is disposed in the feedback circuit or in the input signal circuit of the operational amplifier for compensating the distortion of the nonlinear circuit device.

Abstract: A filter circuit adjustably decreases or increases the amplitude of audio signals in a predetermined frequency range. The filter circuit includes a filter module having an RC network with at least one frequency-response-determining RC member whose resistor component R is realized in SC technology. A setting device is connected to the filter module such that its setting determines the frequency response of the SC filter. The setting device renders possible a neutral setting in which the effective audio signal path of the filter circuit circumvents the filter module so that no decrease or increase of the amplitude of individual frequency portions takes place. Furthermore, an audio signal processor comprises at least one audio signal input, at least one audio signal output, and at least one control input.

Abstract: Driver and overload protection circuit for an electrical switch means. Switching control pulses with a minimum edge duration are fed to a two stage comparator circuit having first, lower and second, higher comparator threshold values. When the lower comparator threshold value is exceeded by a switching control pulse, the electrical switch means is rendered conducting. There is provided an overload detection circuit which, upon detection of overload of the electrical switch means, effects switching off of the same. For avoiding that turning on spikes upon each turning on of the electrical switch means, for example when switching capacitive loads, lead to deactivation of the switch means, any overload signal of the overload detector means is blocked as long as the instantaneous voltage value of the particular switching control pulse is not above the upper comparator threshold.

Abstract: In a stereo decoder, channel separation takes place with the aid of a demodulator to acquire signals for stereo operation. At low received field strength there is a continuous switchover to mono operation for each channel in the demodulator. For this purpose a switch is located in a signal path between input and output of the demodulator and driven by a PWM signal whose pulse-width repetition rate determines whether solely mono operation, solely stereo operation or a mixture of the two takes place. For generating the PWM signal, the field strength signal is compared with a triangular signal. To permit the switchover points between stereo and mono operation to be aligned by the manufacturer in accordance with the amplitude of the field strength signal, the apparatus contains two limit storage registers in which digital limit signals are set from outside.

Abstract: A circuit combining the functions of phase-sensitive rectifier and integrator uses an operational amplifier and capacitors. A control signal switches a capacitor in and out of a feedback loop containing a second feedback capacitor, resulting in a residual charge in the second feedback capacitor if there is a phase-difference between an input signal and the control signal. The invention may also incorporate an automatic offset compensation circuit by using additional switches and a second control signal. The capacitor that is switched in and out of the feedback loop is coupled to a compensation capacitor during periods when the capacitor is not being used for the phase-sensitive rectifier and integrator portions of the circuit. The circuit arrangement allows the use of long time constants in the integrator portion of the circuit.

Abstract: A device for digital aurally compensated loudness control of audio signals, comprising two fine-stepped resistor chains connected in a series connection which on one end is adapted to be acted upon by the audio signal to be attenuated and whose connection point has a correction impedence connected thereto, and comprising one coarse-stepped resistor chain which at one end receives the fine-attenuated audio signal taken off from one fine-stepped resistor chain and which has at least one feed-in terminal at a predetermined location along the coarse-stepped resistor chain into which is fed a fine-attenuated audio signal taken off from the other fine-stepped resistor chain. The output signal of the device is taken off from the coarse-stepped resistor chain.

Abstract: The synchronism or tracking between two analog signals is compared by a cuit arrangement having two inputs to which these analog signals are applied. A comparator circuit compares the two signals and provides a trigger or energizing signal to a switch which in turn produces an error signal when the two compared signals deviate from each other to an extent larger than a predetermined limit. One input is connected to the comparator circuit through a heterodyning circuit wherein the respective analog signal is heterodyned by a heterodyning signal which varies in its polarity. The comparator circuit includes a polarity detector which provides a signal signifying a positive or a negative difference between the amplitudes of the two polarity signals. A discriminator circuit is operatively connected to the comparator to provide a switch energizing signal when the difference signal does not have any zero transitions or passages with the frequency of the heterodyning signal.