A communication system includes a demodulator configured to demodulate a modulated signal responsive to a first carrier signal. The demodulator includes a filter and a gain adjusting circuit. The filter is configured to generate a filtered first signal based on a first signal. The first signal is a product of the first carrier signal and the modulated signal. The filter has a gain adjusted based on a set of control signals. The gain adjusting circuit is coupled to the filter, and is configured to generate the set of control signals based on at least a voltage of the filtered first signal. The gain adjusting circuit includes a first peak detector coupled to the filter. The first peak detector is configured to output a peak value of the voltage of the filtered first signal.

A communication system includes a transmitter configured to transmit a modulated signal, a transmission line configured to carry the modulated signal, and a receiver coupled to the transmitter by the transmission line, and configured to receive the modulated signal. The transmitter includes a modulator configured to generate the modulated signal responsive to a data signal and a carrier signal. The receiver includes a demodulator configured to demodulate the modulated signal responsive to a first carrier signal. The demodulator includes a filter and a gain adjusting circuit configured to adjust a gain of the filter, and to generate the set of control signals based on a voltage of the filtered first signal and a voltage of the first signal. The gain adjusting circuit includes a first peak detector coupled to the filter, and configured to detect a peak value of the voltage of the filtered first signal.

A low pass filter is disclosed. In an embodiment a low-pass filter includes a current-compensated choke, a reference potential and a capacitor connected in parallel with the current-compensated choke and to the reference potential, wherein a core of the current-compensated choke is configured to have a magnetic circuit, and wherein the core has an air gap.

Analog interference filter devices and methods for isolation of desirable portions of a radio frequency signal. Signal compensation is used to provide desirable center frequency, passband width, ripple, rolloff, stopband and distortion performance. The filter is implemented with passive and/or active components.

The present disclosure relates to a concept of nonlinear signal processing which may be used for predistortion for RF power amplifiers. The concept includes generating time variant filter coefficients for a linear filter circuit based on a nonlinear mapping of an input signal, and filtering the input signal with the linear filter circuit using the time variant filter coefficients in order to generate a filtered output signal. Thus, it is proposed to implement a non-linear filter by a time-varying linear filter where the time-varying coefficients are derived from the input signal.

In an embodiment a low-pass filter arrangement has an input terminal for receiving an input voltage, a first voltage source coupled to the input terminal, a serial connection comprising a first and a second filter diode, the serial connection being coupled to the first voltage source, wherein a connection point between the first and the second filter diode is coupled to an output terminal of the filter arrangement, and a first filter capacitor coupled between the output terminal and a filter reference potential terminal. Therein the first voltage source is adapted to provide a first adjustable forward voltage whereby the first and the second filter diodes are both biased in a forward direction.

This nonlinear microwave filter is provided with quantum bits that are formed on a circuit board in which target quantum bits are formed which are quantum bits controlled in a superconducting quantum circuit, and that are coupled to a control waveguide to which the target quantum bits are coupled, wherein the distance to a waveguide end in the control waveguide is within a predetermined range from semi integer times the resonant wavelength, the quantum bits have a resonant frequency in which the difference from the resonant frequency of the target quantum bits is within a predetermined range, and the coupling to the control waveguide is stronger by a predetermined value than the coupling between the target quantum bits and the control waveguide.

Frequency multipliers (300) for generating a differential output signal from a single-ended input signal are disclosed. The frequency multiplier comprises a single-ended input (P.sub.in(f.sub.0)) to receive the input signal with a frequency of f.sub.0 and differential outputs (+/−P.sub.out(2nf.sub.0)) to provide the differential output signals. The frequency multiplier further comprises a first signal branch (301) connected to the single-ended input and one of the differential outputs (+P.sub.out(2nf.sub.0)). The first signal branch comprises a first low pass or bandpass filter with a center frequency of f.sub.0 (L/BPF1), a first nonlinear component (NC1) and a first high pass or bandpass filter with a center frequency of 2nf.sub.0 (H/BPF1). The frequency multiplier further comprises a second signal branch connected to the single-end input and another one of the differential outputs (−P.sub.out(2nf.sub.0)). The second signal branch comprises a second low pass or bandpass filter with a center frequency of f.sub.0 (L/BPF1), a second nonlinear component (NC2) and a second high pass or bandpass filter with a center frequency of 2nf.sub.0 (H/BPF2). The first and second nonlinear components are configured such that even-order harmonics generated in the first and second nonlinear components are in anti-phase, thereby the differential output signals with a frequency of 2n times the frequency of the input signal are generated at the differential output, where n is an integer number.

A communication system includes a transmitter configured to transmit a modulated signal, a transmission line configured to carry the modulated signal, and a receiver coupled to the transmitter by the transmission line, and configured to receive the modulated signal. The transmitter includes a modulator configured to generate the modulated signal responsive to a data signal and a carrier signal. The receiver includes a demodulator configured to demodulate the modulated signal responsive to a first carrier signal. The demodulator includes a filter and a gain adjusting circuit configured to adjust a gain of the filter, and to generate the set of control signals based on a voltage of the filtered first signal and a voltage of the first signal. The gain adjusting circuit includes a first peak detector coupled to the filter, and configured to detect a peak value of the voltage of the filtered first signal.

A communication system includes a modulator configured to generate a modulated signal responsive to at least a data signal, and a demodulator configured to demodulate the modulated signal responsive to a first carrier signal. The demodulator includes a filter configured to generate a filtered first signal based on a first signal, and a gain adjusting circuit coupled to the filter. The first signal is based on the first carrier signal and modulated signal. The filter has a gain controlled by a set of control signals. The gain adjusting circuit is configured to adjust the gain of the filter, and to generate the set of control signals based on a voltage of the filtered first signal and a voltage of the first signal. The gain adjusting circuit includes a first peak detector coupled to the filter, and configured to detect a peak value of the voltage of the filtered first signal.