Abstract: A wireless transmission system includes a base station device connected to a wireless device by an optical transmission member. The base station device includes an acquiring unit that acquires a distortion component that corresponds to a level of a transmission signal, an amplifying unit that amplifies the distortion component at a predetermined gain, and a transmitting unit that transmits the transmission signal and the amplified distortion component in a separable manner. The wireless device includes a receiving unit that receives the transmission signal and the distortion component, a filtering unit that filters the transmission signal, an attenuating unit that attenuates the distortion component at a gain inverse of the predetermined gain, a combining unit that combines the filtered transmission signal with the attenuated distortion component to obtain a combined signal, and an amplifier that amplifies the combined signal.

Abstract: A power amplifier apparatus includes an amplifier configured to amplify an input signal converted into an analog signal, a distortion compensator circuitry configured to perform a pre-distortion process to an input signal at a second sampling rate higher than a first sampling rate at which the input signal is converted into an analog signal, a remover configured to remove a frequency component exceeding a frequency band corresponding to the first sampling rate from the input signal subjected to the pre-distortion process, a first rate converter configured to convert a sampling rate of the input signal from which the frequency component is removed from the second sampling rate to the first sampling rate, and a first signal converter configured to convert the input signal the sampling rate of which is converted into an analog signal at the first sampling rate to supply the input signal converted into the analog signal to the amplifier.

Abstract: A distortion compensation apparatus compensates for non-linear distortion of a power amplifier. The distortion compensation apparatus includes a pre-distorter, a learning unit, and a gain control unit. During training of the pre-distorter, the learning unit repeatedly updates a compensation coefficient on the basis of signals output from the power amplifier. While the training continues after update of the compensation coefficient, the gain control unit performs gain control on a signal before input to the power amplifier.

Abstract: A LINC power amplifier selects, based on an amplitude of an input signal, partial signals used for combination, and determines, based on the amplitude and a phase of the input signal, an amplitude and a phase of the selected partial signals so that a range of output power that the LINC power amplifier operates a given efficiency is expanded, inputs the selected partial signals to corresponding power amplifiers, and combines signals obtained by amplification of the selected partial signals by the corresponding power amplifiers.

Abstract: A transmitter includes: first and second IFFT units that respectively generate first and second time domain signals from first and second modulated signals generated in first and second modulation schemes; a clipping noise signal generator that generates a clipping noise signal representing a difference between a combined signal of the first and second time domain signals and a specified threshold in a time period in which the power of the combined signal is higher than the threshold; first and second calculators that respectively subtract the clipping noise signals to which first and second coefficients are multiplied from the first and second time domain signals; first and second frequency filters that respectively filter output signals of the first and second calculators; and a combiner that generates a transmission signal including an output signal of the first frequency filter and an output signal of the second frequency filter.

Abstract: A transmission signal power control device includes: at least one low-power attenuator configured to attenuate amplitude of a transmission signal when an absolute value of the amplitude of the transmission signal is smaller than or equal to a clipping threshold; a power amplifier configured to amplify the transmission signal output from the at least one low-power attenuator; and a control unit configured to stop operation of the power amplifier when the absolute value of the amplitude of the transmission signal is smaller than or equal to a value and operate the power amplifier when the absolute value of the amplitude of the transmission signal is larger than the value.

Abstract: A distortion compensation apparatus includes a calculation unit that acquires, from calculation performed by using a factor and an output signal from the amplifier, a distortion component that is associated with the distortion generated in the amplifier, and a comparing unit that compares a signal that is obtained by giving the distortion component acquired by the calculation unit to an output signal output from the amplifier, with an input signal input to the amplifier, to which a distortion component is previously given. The calculation unit adjusts, on the basis of a comparison result obtained by the comparing unit, the factor that is used for the calculation.

Abstract: A distortion compensation device includes: a distortion compensator configured to output, to a power amplifier, a predistortion signal obtained by performing distortion compensation processing on a transmission signal by using a distortion compensation coefficient, wherein the distortion compensator limits bands of a reference signal and a feedback signal so that the bands fall in a pass band and updates the distortion compensation coefficient based on an error between the reference signal and the feedback signal, the reference signal corresponding to the predistortion signal, the feedback signal corresponding to an output feedback of the power amplifier.

Abstract: A predistorter gives an input signal inputted to a power amplifier distortion corresponding to a compensation coefficient. A band limiter limits components in a second frequency band other than a first frequency band of a feedback signal fed back from the power amplifier, and distorts components in the first frequency band according to the limited components in the second frequency band. A learner updates the compensation coefficient on the basis of the distorted feedback signal.

Abstract: A signal processing system is provided. The signal processing system includes: a peak-to-average ratio (PAPR) reducer that reduces a peak-to-average ratio (PAPR) of an input signal x(n), a clipping noise processing system that generates an equivalent clipping noise signal ?*CL(n) that is defined as a weighted sum of a weighted in-band clipping signal WIN*?CL,IN(n) and a weighted out-of-band clipping signal WOUT*?CL,OUT(n) to be used for determining functions of a predistorter that suppresses out-of-band spectrum caused during peak-to-average power reduction process and for generating an input signal of an amplifier which input signal has reduced clipping noise and be distorted so as to compensate nonlinearity of the amplifier.

Abstract: An amplifier includes an increase unit, a generator, a decrease unit, an adder, and an amplification unit. The increase unit increases a rate of an input signal and samples the input signal. The generator generates a predistorter signal for compensating for distortion occurring due to amplification of the input signal, from the input signal whose rate is increased by the increase unit. The decrease unit configured to decrease a rate of the predistorter signal generated by the generator to the rate before being increased by the increase unit. The adder adds the predistorter signal whose rate is decreased by the decrease unit to the input signal before the rate is increased. The amplification unit configured to amplify the input signal to which the predistorter signal is added by the adder.

Abstract: A transmission signal power control apparatus includes a power amplifier model unit which generates a learning digital signal by multiplying part of a predistortion signal by model coefficients which tentatively represent the input-output characteristics of a power amplifier, and an adaptive low-pass filter which generates a pseudo feedback signal by attenuating the high frequency components of the learning digital signal by multiplying the learning digital signal by weighting coefficients. Then, the power amplifier model unit updates the model coefficients such that the error between the feedback signal whose the high frequency components are attenuated by the low-pass filter and which is digitized, and the pseudo feedback signal is minimized, and the adaptive low-pass filter updates the weighting coefficients such that the error is minimized.

Abstract: A distortion compensation apparatus includes a pre-distorter, a gain control unit, and a learning unit. The pre-distorter adds distortion according to compensation coefficients to individual input signals prior to the input signals being input to a power amplifier. The gain control unit applies gain control to individual feedback signals fed back from the power amplifier according to a maximum level of the feedback signals within a time frame. The learning unit updates the compensation coefficients used by the pre-distorter, using the feedback signals subjected to the gain control by the gain control unit.

Abstract: A predistortion apparatus, includes a reducer to output a signal that a peak to average power ratio of an input signal is reduced by clipping, a first predistorter to generate and output a first predistortion signal from the output signal of the reducer, based on a signal obtained by removing a clipping noise caused by the clipping from the output signal of the reducer, so as to reduce energy of a residual error component obtained by removing a clipping noise caused by the clipping from an error signal included in an output of the power amplifier, a second predistorter to generate and output, by using the clipping noise, a second predistortion signal to remove a clipping noise component from the first predistortion signal, and a combiner to generate an input signal of the power amplifier obtained by combining the first predistortion signal and the second predistortion signal.

Abstract: A signal processing apparatus includes a corrector that corrects a digital signal in accordance with a correction value, a converter that converts the digital signal corrected by the corrector into an analog signal, a sample-and-hold unit that holds an instantaneous value of the analog signal that has been obtained by the converter and that has been amplified by an amplifier for a certain frequency that is smaller than twice a maximum frequency of the analog signal, a digitizer that converts the instantaneous value held by the sample-and-hold unit into a digital value when the digitizer received an operation clock having the certain frequency, and an updater that updates, on the basis of the digital value obtained by the digitizer, the correction value of the corrector such that the correction value becomes a correction value that reduces nonlinear distortion in the analog signal amplified by the amplifier.

Abstract: A distortion compensation apparatus compensates for non-linear distortion of a power amplifier. The distortion compensation apparatus includes a pre-distorter, a learning unit, and a gain control unit. During training of the pre-distorter, the learning unit repeatedly updates a compensation coefficient on the basis of signals output from the power amplifier. While the training continues after update of the compensation coefficient, the gain control unit performs gain control on a signal before input to the power amplifier.

Abstract: A power amplifier apparatus includes an amplifier configured to amplify an input signal converted into an analog signal, a distortion compensator circuitry configured to perform a pre-distortion process to an input signal at a second sampling rate higher than a first sampling rate at which the input signal is converted into an analog signal, a remover configured to remove a frequency component exceeding a frequency band corresponding to the first sampling rate from the input signal subjected to the pre-distortion process, a first rate converter configured to convert a sampling rate of the input signal from which the frequency component is removed from the second sampling rate to the first sampling rate, and a first signal converter configured to convert the input signal the sampling rate of which is converted into an analog signal at the first sampling rate to supply the input signal converted into the analog signal to the amplifier.

Abstract: An ISI Replica unit is provided, which produces interference components similar to one due to LPF into the output of HPA MODEL unit. An HPA MODEL unit models the characteristic of HPA using the output signal of the predistorter and an error signal obtained by subtracting a feedback signal from the output of the ISI Replica so that the error signal approaches zero. The feedback signal is used after filtration by LPF, thereby including interference components. The error signal obtained by the feedback signal after LPF and the output signal of ISI Replica unit includes few interference components, thereby modeling by the HPA MODEL unit becomes accurate and the linearization performances become better.

Abstract: A transmission signal power control apparatus includes a power amplifier model unit which generates a learning digital signal by multiplying part of a predistortion signal by model coefficients which tentatively represent the input-output characteristics of a power amplifier, and an adaptive low-pass filter which generates a pseudo feedback signal by attenuating the high frequency components of the learning digital signal by multiplying the learning digital signal by weighting coefficients. Then, the power amplifier model unit updates the model coefficients such that the error between the feedback signal whose the high frequency components are attenuated by the low-pass filter and which is digitized, and the pseudo feedback signal is minimized, and the adaptive low-pass filter updates the weighting coefficients such that the error is minimized.

Abstract: A transmission signal power control device includes: at least one low-power attenuator configured to attenuate amplitude of a transmission signal when an absolute value of the amplitude of the transmission signal is smaller than or equal to a clipping threshold; a power amplifier configured to amplify the transmission signal output from the at least one low-power attenuator; and a control unit configured to stop operation of the power amplifier when the absolute value of the amplitude of the transmission signal is smaller than or equal to a value and operate the power amplifier when the absolute value of the amplitude of the transmission signal is larger than the value.