A communication system includes a transmission unit configured to output a signal, an attenuation unit configured to attenuate the signal output from the transmission unit, a first coupler having one end portion being connected to the transmission unit via the attenuation unit, a termination unit that is connected to the other end portion of the first coupler, and a second coupler configured to input a signal to the first coupler using at least one of electric field coupling and magnetic field coupling, wherein the first coupler or the second coupler is configured to be movable so that a relative position between the first coupler and the second coupler changes.

A communications device and a method for compensating frequency response distortion of the communication device are provided. The communications device includes a transmitting path circuitry, a receiving path circuitry, a memory pre-distortion circuit, a pre-equalizer circuit and a pre-equalization calculation circuit. The transmitting path circuitry and the receiving path circuitry are configured to generate a feedback signal according to a pre-distortion test signal, where a set of pre-distortion coefficients of the memory pre-distortion circuit are calibrated according to the feedback signal. After calibration of the set of pre-distortion coefficients is finished, the pre-equalization calculating circuit performs calculation on the set of pre-distortion coefficients to generate a calculation result for calibrating the pre-equalizer circuit. After calibration of the pre-equalizer circuit is finished, a transmission signal is processed by the pre-equalizer circuit and the memory pre-distortion circuit first, and then output to outside of the communications device via the transmitting path circuitry.

A power supply circuit in a wireless communications system includes an envelope tracking modulator coupled to a first power amplifier circuit and a second power amplifier circuit, so that the power supply circuit supplies power to the first power amplifier circuit and the second power amplifier circuit. When a transmit signal output by a processor is within a first bandwidth range, the power supply circuit supplies power to the first power amplifier circuit, and the first power amplifier circuit amplifies power of the transmit signal. When the transmit signal output by the processor meets a second bandwidth range, the power supply circuit supplies power to the second power amplifier circuit, and the second power amplifier circuit amplifies the transmit signal.

A transceiver is configured for a calibration mode of operation in which an impedance of a transmit chain is tuned responsive to a power measurement of a mixed RF calibration signal to form a tuned transmit chain. A direct conversion mixes an RF calibration signal with a DC offset signal to form the mixed calibration signal. During a normal mode of operation, a heterodyne mixer mixes an LO signal with an IF signal to produce an RF signal that is amplified through the tuned transmit chain.

A method for reducing distortions of a radio frequency (RF) system includes configuring a plurality of mixers to convert between a plurality of phase signals and a plurality of RF signals, configuring a first mixer of the plurality of mixers to operate in a six-phase operating mode to reduce the distortions of the RF system, and configuring a second mixer of the plurality of mixers to operate in a three-phase operating mode to reduce power consumption of the RF system.

A filter circuit comprises in a signal line a band filter (BF) allowing to let pass a useful frequency band and a notch filter (NF) circuited in series to the band filter for filtering out a stop band frequency. The notch filter comprises a series circuit of a number of parallel shunt elements (SE1 . . . SE6) wherein each shunt element is shifted infrequency against the other shunt elements that the frequencies thereof are distributed (f1 . . . F6) over a notch band. All shunt elements may be realized as a SAW one-port resonator (TR.sub.NF) including regions with different pitches.

A radio frequency transmitter includes a digital-to-analog converter, an analog baseband processor, and a modulator. The digital-to-analog converter is configured to convert a digital frequency-converted signal into a first analog signal, where the digital frequency-converted signal is obtained by performing digital frequency conversion on a digital baseband signal based on a first frequency signal; the analog baseband processor is configured to perform filtering and gain adjustment on the first analog signal to obtain a second analog signal; and the modulator is configured to perform up conversion based on a second frequency signal and the second analog signal, to obtain a radio frequency signal, where the second frequency signal is determined based on a local frequency signal and the first frequency signal.

The present disclosure provides a mixing circuit with high harmonic suppression ratio, including: a multi-phase generation module, which receives a first input signal and generates eight first square wave signals with a phase difference of 45°; a quadrature phase generation module, which receives a second input signal and generates four second square wave signals with a phase difference of 90°; a harmonic suppression module, connected with an output end of the quadrature phase generation module to filter out higher order harmonic components in the second square wave signals; and a mixing module, connected with output ends of the multi-phase generation module and the harmonic suppression module to mix output signals of the multi-phase generation module and the harmonic suppression module. The mixing circuit with high harmonic suppression ratio adds a harmonic suppression module on the basis of multi-phase mixing, thereby improving the harmonic suppression ratio of the output signal.

A high-speed signaling system with adaptive transmit pre-emphasis. A transmit circuit has a plurality of output drivers to output a first signal onto a signal path. A receive circuit is coupled to receive the first signal via the signal path and configured to generate an indication of whether the first signal exceeds a threshold level. A first threshold control circuit is coupled to receive the indication from the receive circuit and configured to adjust the threshold level according to whether the first signal exceeds the threshold level. A drive strength control circuit is coupled to receive the indication from the receive circuit and configured to adjust a drive strength of at least one output driver of the plurality of output drivers according to whether the first signal exceeds the threshold level.

A transmitter for a communication system comprises a digital pre-distortion (DPD) circuit and adaptation circuitry. The DPD circuit is configured to generate a digital intermediate signal by compensating an input signal for distortions resulting from an amplifier. The amplifier is configured to output an output signal based on the digital intermediate signal. The DPD circuit includes one or more an infinite impulse response (IIR) filters configured to implement a first transfer function based on a first parameter, and a second transfer function based on the first parameter and a time constant. The DPD circuit is configured to generate an adjustment signal based on the first transfer function and the second transfer function. The adaptation circuitry is configured to update the first parameter based on the adjustment signal, the input signal, and the output signal.