WO2009093396A1

WO2009093396A1 - Non-linear distortion compensation circuit, transmission circuit, and non-linear distortion compensation method

Info

Publication number: WO2009093396A1
Application number: PCT/JP2008/072714
Authority: WO
Inventors: Masaki Ichikawa
Original assignee: Nec Corporation
Priority date: 2008-01-25
Filing date: 2008-12-14
Publication date: 2009-07-30

Abstract

Provided is a non-linear distortion compensation circuit that compensates the non-linearity of a power amplifier and also the nonlinear phase characteristics of an analog filter and can perform a highly accurate non-linear distortion compensation as a transmission system without significantly increasing a circuit scale. The non-linear distortion compensation circuit comprises: a compensation coefficient calculation unit for calculating a compensation coefficient from a reverse component of the non-linear distortion produced in the power amplifier and a reverse component of the nonlinear phase characteristics of the analog filter; and a complex multiplication unit for performing a complex calculation between the compensation coefficient calculated by the compensation coefficient calculation unit and a baseband digital signal to be inputted and performing a non-linear distortion compensation on the baseband digital signal.

Description

Nonlinear distortion compensation circuit, transmission circuit, and nonlinear distortion compensation method

The present invention relates to a non-linear distortion compensation circuit, a transmission circuit, and a non-linear distortion compensation method, and particularly to a technique preferably applied in non-linear distortion compensation in a transmission system of a digital microwave radio communication system.

In the digital microwave radio communication system, a quadrature amplitude modulation method such as multi-level QAM is used as a modulation method from the viewpoint of frequency utilization efficiency. In this method, the power amplifier that amplifies the transmission signal uses only a linear region in its input / output characteristics, and therefore it is desirable to take sufficient backoff. The back-off represents an operating point, and is generally given by the difference between the maximum output amplitude level and the output saturation power level.

However, since a sufficiently large transmission power cannot be obtained if the back-off is large, it is actually necessary to reduce the back-off and use it in the non-linear region. At this time, there arises a problem that non-linear distortion generated by using the power amplifier up to the non-linear region is superimposed on the transmission signal and causes characteristic deterioration. For this reason, using a circuit called a predistorter, the nonlinear distortion generated when the signal is amplified is compensated by superimposing the inverse component of the nonlinear distortion corresponding to the power input to the power amplifier on the transmission signal. The way is done.

Fig. 1 shows a configuration example of an open loop transmission circuit using a predistorter. The circuit configuration example of FIG. 1 is also employed in the embodiments of the present invention described later, and each configuration (device) is common to the present embodiment (however, the internal configuration and functions of the predistorter are different). Since these are separate circuits, different numbers are used here for explanation. The transmission circuit includes an FIR (Finite Impulse Response) filter 11, a predistorter 12, a modulator 13, a BPF (Band Pass Filter) 14, and a power amplifier 15. In the digital microwave radio communication system, since it is necessary to transmit using only a predetermined frequency band, an out-of-band signal generated in a modulator or the like is removed using an analog filter. For this reason, the transmission circuit includes a BPF 14.

The input baseband digital signal 8 is supplied to the modulator 13 through the FIR filter 11 and the predistorter 12, is subjected to quadrature amplitude modulation there, passes through the BPF 14, and is amplified by the power amplifier 15. In this transmission circuit, the inverse characteristic of the nonlinear distortion characteristic of the power amplifier 15 is obtained in advance, and this is held in the predistorter 12 so that a compensation value for the input level of the power amplifier 15 is obtained. Yes. That is, distortion generated from the power amplifier is caused by nonlinearity of the amplitude and phase characteristics generated in the saturation region of the amplifier, and the predistorter 12 performs nonlinear compensation of the amplitude and phase characteristics of the power amplifier.

This circuit configuration has the advantage of being simple and inexpensive. However, the characteristic held in the predistorter 12 is the reverse characteristic of the power amplifier 15. For this reason, when the power is input to the power amplifier 15 due to the non-linear phase characteristic of the BPF 14 generated in the frequency band where the non-linear distortion is compensated, there is a deviation from the inverse characteristic of the non-linear phase characteristic of the power amplifier 15. In this way, due to the non-linear phase characteristics of the analog filter used in the transmission circuit, it is difficult to sufficiently compensate the distortion even if the predistorter superimposes the inverse component of the non-linear distortion of the power amplifier. There was a problem that the nonlinear distortion compensation effect could not be obtained.

By the way, for example, Patent Document 1 discloses a distortion compensator that can simultaneously guarantee linear distortion and nonlinear distortion. In the distortion compensator, outputs of a PA (Power Amplifier) that generates nonlinear distortion and a BPF that generates linear distortion are selectively input to a switching circuit. Then, with the selection input and the timing and frequency of the transmission signal matched, the linear distortion is detected by the linear distortion detection circuit and output to the linear distortion compensation circuit, and the linear distortion is compensated by the linear distortion compensation circuit. In the same state, the nonlinear distortion is detected by the nonlinear distortion detection circuit and output to the nonlinear distortion compensation circuit, and the nonlinear distortion is compensated by the nonlinear distortion compensation circuit.
Japanese Patent Laid-Open No. 2007-82015

The distortion compensator disclosed in Patent Document 1 has three compensation circuits, and is configured to perform compensation operation with three compensation circuits each time the main signal changes. For this reason, the circuit scale which operates every time the main signal changes increases, leading to an increase in power consumption. Further, Patent Document 1 compensates for linear distortion generated by a filter, and does not eliminate a shift in nonlinear compensation (with respect to the phase characteristic of the power amplifier) caused by the nonlinear phase characteristic of the filter.

Therefore, in view of the above-described circumstances, the present invention compensates for nonlinear phase characteristics of an analog filter in addition to compensation for nonlinearity of a power amplifier, and achieves highly accurate nonlinearity as a transmission system without significantly increasing the circuit scale. An object of the present invention is to provide a nonlinear distortion compensation circuit, a transmission circuit, and the like that can perform distortion compensation.

In order to achieve this object, a nonlinear distortion compensation circuit according to the present invention includes a compensation coefficient calculation unit that calculates a compensation coefficient from an inverse component of nonlinear distortion generated in a power amplifier and an inverse component of nonlinear phase characteristics of an analog filter; A complex multiplier that performs a complex operation of the compensation coefficient calculated by the compensation coefficient calculator and the input baseband digital signal to compensate for nonlinear distortion of the baseband digital signal.

The transmission circuit of the present invention includes the above-described nonlinear distortion compensation circuit, a power amplifier, and an analog filter.

The nonlinear distortion compensation method of the present invention includes a compensation coefficient calculation step for calculating a compensation coefficient from an inverse component of nonlinear distortion generated in a power amplifier and an inverse component of nonlinear phase characteristics of an analog filter, and a compensation coefficient calculation step. A complex multiplication step of performing a complex operation between the calculated compensation coefficient and the input baseband digital signal to compensate for nonlinear distortion of the baseband digital signal.

According to the present invention, it is possible to compensate for nonlinear phase characteristics of an analog filter in addition to compensation for nonlinearity of a power amplifier, and to perform highly accurate nonlinear distortion compensation as a transmission system without significantly increasing the circuit scale. It becomes.

The nonlinear distortion compensation circuit 1 to which the present invention is applied includes a compensation coefficient calculation unit 2 and a complex multiplication unit 3 as shown in FIG. The compensation coefficient calculation unit 2 calculates a compensation coefficient from the inverse characteristic of the nonlinear distortion (amplitude characteristic and phase characteristic) generated in the power amplifier 5 and the inverse characteristic of the nonlinear phase characteristic of the analog filter 4. The complex multiplier 3 performs a complex operation of the baseband digital signal 6 input to the nonlinear distortion compensation circuit 1 and the compensation coefficient calculated by the compensation coefficient calculator 2 to compensate for nonlinear distortion of the baseband digital signal. . The baseband signal 6 subjected to nonlinear distortion compensation is amplified by the power amplifier 5 after the signal outside the band is removed by the analog filter 4.

The compensation coefficient calculation unit 2 includes an amplitude compensation coefficient calculation unit that calculates an inverse characteristic of the amplitude characteristic of the nonlinear distortion generated in the power amplifier 5 as an amplitude compensation coefficient, an inverse characteristic related to the phase characteristic of the nonlinear distortion generated in the power amplifier 5, and You may comprise so that it may have a phase compensation coefficient calculation part which calculates a phase compensation coefficient from the inverse characteristic of the nonlinear phase characteristic of the analog filter 4. FIG. Further, the compensation coefficient calculation unit 2 may be configured to calculate the compensation coefficient by performing a complex operation of the amplitude compensation coefficient and the phase compensation coefficient.

Then, the compensation coefficient calculation unit 2 relates to the amplitude characteristic and phase characteristic of the nonlinear distortion generated in the power amplifier 5, based on the inverse characteristic data held in advance and the input level of the power amplifier 5, with the inverse characteristic of the amplitude characteristic. A certain amplitude compensation coefficient or a first phase compensation coefficient that is the inverse characteristic of the phase characteristic may be calculated. Further, the compensation coefficient calculation unit 2 is configured to calculate a second phase compensation coefficient that is an inverse characteristic of the phase characteristic based on the inverse characteristic data held in advance with respect to the nonlinear phase characteristic of the analog filter 4. Also good. The compensation coefficient calculation unit 2 may be configured to calculate the phase compensation coefficient by adding the second phase compensation coefficient as an offset to the first phase compensation coefficient.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1, 3, and 4. FIG. 1 is a diagram illustrating a configuration of a transmission circuit in which a predistorter that is a nonlinear distortion compensation circuit of the present embodiment is mounted. In the present embodiment, the transmission circuit 100 employs an open loop configuration using the predistorter 20. The transmission circuit 100 is a circuit used in a microwave digital radio communication system, and includes an FIR filter 10, a modulator 30, a BPF 40, and a power amplifier 50 in addition to the predistorter 20. Here, the input signal format is assumed to be a quadrature amplitude modulation scheme such as multi-level QAM (Quadrature Amplitude Modulation).

The FIR filter 10 is supplied with a baseband digital signal (Ich DATA) at one input and a baseband digital signal (Qch DATA) at the other input, and the bandwidth of these input baseband digital signals 8 Limit. The output of the FIR filter 10 is supplied to the predistorter 20, respectively. Here, the baseband digital signal (Ich DATA) is a numerical sequence of the real part (corresponding to the I axis), and the baseband digital signal (Qch DATA) is a numerical sequence of the imaginary part (corresponding to the Q axis). . The predistorter 20 superimposes the inverse component of the nonlinear distortion (amplitude characteristic and phase characteristic) generated in the power amplifier 50 and the inverse component of the nonlinear phase characteristic of the BPF 40 on the output baseband digital signal from the FIR filter 10. Compensates for nonlinear distortion.

The modulator 30 receives the baseband digital signal compensated for the nonlinearity output from the predistorter 20 and outputs the input signal as a modulated wave (transmission signal) obtained by quadrature amplitude modulation. The output of the modulator 30 passes through the BPF 40. The BPF 40 removes unnecessary wave components generated by the modulator 30 and the like. The signal that has passed through the BPF 40 is supplied to the power amplifier 50. The power amplifier 50 amplifies the modulated wave input from the modulator 30, and the level is automatically controlled so that the average output level becomes a desired output level.

FIG. 3 is a diagram showing an internal configuration of a predistorter which is a nonlinear distortion compensation circuit of the present embodiment. A specific configuration of the predistorter 20 will be described with reference to FIG. In the present embodiment, compensation for nonlinear distortion of both the power amplifier 50 and the BPF 40 is performed. The amount of nonlinear distortion generated in the power amplifier 50 varies depending on the input / output level. Since the amount of compensation needs to be increased as the input / output level increases, the amount of nonlinear compensation is changed for each input level of the power amplifier 50. On the other hand, the nonlinear distortion generated by an analog filter such as the BPF 40 is constant regardless of the input / output level, and the compensation of the phase characteristics of the filter is performed as nonlinear distortion compensation.

In the frequency band necessary to perform nonlinear distortion compensation, the analog filter amplitude characteristics are almost linear. To make the phase characteristics almost linear, however, the filter band is a band where the amplitude characteristics are almost linear. Need to be wider. On the other hand, if the band of the filter is widened, unnecessary wave components cannot be removed. Therefore, it is assumed that the filter has a substantially linear amplitude characteristic and a non-linear phase characteristic. Here, only the phase characteristic is compensated. Thus, the compensation method for the non-linear distortion generated in the power amplifier 50 and the BPF 40 is different.

The predistorter 20 includes an operating point setting circuit 21, an AMP amplitude compensation coefficient calculation unit 22, an AMP phase compensation coefficient calculation unit 23, a BPF phase compensation coefficient offset unit 24, a compensation coefficient calculation unit 25, and a complex multiplier 26. The operating point setting circuit 21 calculates the input level of the power amplifier 50 from the desired output level information 9 of the power amplifier 50 and outputs it to the AMP amplitude compensation coefficient calculator 22 and the AMP phase compensation coefficient calculator 23. The AMP amplitude compensation coefficient calculation unit 22 holds in advance the inverse characteristic data of the nonlinear distortion of the power amplifier 50, and the nonlinear distortion is obtained from the inverse characteristic data and the input level of the power amplifier 50 input from the operating point setting circuit 21. The amplitude correction value is obtained by calculating the amplitude characteristic corresponding to the inverse component of the signal, and the correction value is input to the compensation coefficient calculation unit 5.

Similar to the AMP amplitude compensation coefficient calculation unit 22, the AMP phase compensation coefficient calculation unit 23 holds the inverse characteristic data of the nonlinear distortion of the power amplifier 50 in advance, and the inverse characteristic data and the operating point setting circuit 21 are input. The phase correction value (1) is obtained by calculating the phase characteristic corresponding to the inverse characteristic of the nonlinear distortion from the input level of the power amplifier 50, and the correction value is input to the BPF phase compensation coefficient offset unit 24. The BPF phase compensation coefficient offset unit 24 holds in advance inverse characteristic data of the phase characteristics of the analog filter, sets a phase correction value (2) corresponding to the BPF 40, and is input from the AMP phase compensation coefficient calculation unit 23 Add to the phase correction value (1) as an offset. The phase correction value (2) is a value that does not change during operation once set.

The value obtained by adding the phase correction value (2) as an offset to the phase correction value (1) is set as the phase correction value (3), and the correction value is input to the compensation coefficient calculation unit 25. Using the amplitude correction value and the phase correction value (3) obtained above, the compensation coefficient calculation unit 25 performs a complex product to obtain a transmission system compensation coefficient. The complex multiplier 26 performs a complex operation on the baseband digital signal and the compensation coefficient input from the compensation coefficient calculator 5. As a result, the signal output from the predistorter 20 becomes data having the inverse characteristic of the nonlinear distortion of the power amplifier 50 and the BPF 40.

This signal is subjected to quadrature amplitude modulation by the modulator 30 and then supplied to the BPF 40. In the BPF 40, the nonlinear phase characteristic of the filter is added to the modulated wave, but it is canceled by the nonlinear distortion component added based on the phase correction value (2). The signal that has passed through the BPF 14 is supplied to the power amplifier 50 where it is amplified and output. Since the modulated wave passing through the power amplifier 50 is superimposed with a nonlinear distortion component added based on the amplitude correction value and the phase correction value (1), the output signal is subjected to nonlinear distortion compensation with high accuracy. Signal can be obtained.

FIG. 4 is a flowchart showing the flow of nonlinear distortion compensation processing in the predistorter in this embodiment. First, the operating point setting circuit 21 calculates the input level from the output level information of the power amplifier 50 and outputs it to the AMP amplitude compensation coefficient calculator 22 and the AMP phase compensation coefficient calculator 23 (step S1).

In the AMP amplitude compensation coefficient calculation unit 22, the inverse characteristic data relating to the amplitude characteristic of the nonlinear distortion of the power amplifier 50 that is held in advance is read (step S2). Then, the amplitude characteristic corresponding to the inverse component of the nonlinear distortion is calculated from the input level input from the operating point setting circuit 21 and the read inverse characteristic data (step S3). Then, the calculated amplitude characteristic is output to the compensation coefficient calculator 25 as an amplitude correction value (step S4).

On the other hand, the AMP phase compensation coefficient calculation unit 23 reads the inverse characteristic data relating to the phase characteristic of the nonlinear distortion of the power amplifier 50 that is held in advance (step S5). Then, a phase characteristic corresponding to the inverse component of the nonlinear distortion is calculated from the input level input from the operating point setting circuit 21 and the read reverse characteristic data, and is output to the BPF phase compensation coefficient offset unit 24 as a phase correction value (1). (Step S6).

Then, in the BPF phase compensation coefficient offset unit 24, the inverse characteristic data of the phase characteristic of the analog filter is read and set as the phase correction value (2) (step S7). Then, the phase correction value (3) is calculated by adding the set phase correction value (2) as an offset to the phase correction value (1) input from the AMP phase compensation coefficient calculation unit 23 (step S8). Then, the phase correction value (3) is output to the compensation coefficient calculation unit 25 as a phase correction value in which the nonlinear phase characteristic of the BPF 40 is offset from the inverse characteristic of the nonlinear distortion of the power amplifier 50 (step S9).

The compensation coefficient calculation unit 25 performs complex product using the amplitude correction value input from the AMP amplitude compensation coefficient calculation unit 22 and the phase correction value input from the BPF phase compensation coefficient offset unit 24 to compensate for the transmission system. A coefficient is calculated (step S10). Then, the complex multiplier 26 performs complex operation on the baseband digital signal 8 from the FIR 10 and the compensation coefficient from the compensation coefficient calculator 25 to compensate for nonlinear distortion (step S11).

As described above, according to the present embodiment, in addition to the nonlinear distortion compensation of the power amplifier, since the nonlinear phase characteristic of the BPF is compensated, more accurate nonlinear distortion compensation can be performed as a transmission system. Become.

In addition, according to the present embodiment, as an analog filter, in the frequency band necessary for performing nonlinear distortion compensation, the amplitude characteristics are almost linear and the number of circuits inside the predistorter is increased to compensate for the nonlinear phase characteristics. It is possible to perform nonlinear distortion compensation with higher accuracy while suppressing the above.

In addition, according to the present embodiment, the circuit configuration other than the circuit configuration inside the predistorter can adopt the same configuration as that used so far, so that the merit that the manufacturing cost is low can be maintained.

As mentioned above, although this invention was demonstrated with reference to embodiment, this invention is not limited to the said embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

That is, from the viewpoint of suppressing an increase in circuit scale, the present invention considers a filter having a substantially linear amplitude characteristic in the frequency band where nonlinear compensation is performed, and compensates only for the nonlinear phase characteristic. It is also possible to compensate for a significant amplitude characteristic.

In addition, a quadrature modulator such as multi-level QAM is assumed as an input signal format, but the present invention is not limited to this modulation method, and any circuit in which a modulator and a power amplifier are superimposed on a transmission signal may be used. It can be applied to anything.

This application claims priority based on Japanese Patent Application No. 2008-015055 filed on January 25, 2008, the entire disclosure of which is incorporated herein.

It is the figure which showed the structure of the transmission circuit provided with the nonlinear distortion compensation circuit which concerns on embodiment of this invention. It is the figure which showed the structure of the nonlinear distortion compensation circuit to which this invention is applied. It is the figure which showed the internal structure of the nonlinear distortion compensation circuit which concerns on embodiment of this invention. It is the flowchart which showed the flow of the nonlinear distortion compensation process in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nonlinear

distortion compensation circuit

2,25 Compensation

coefficient calculation part

3,26 Complex multiplication part 4

Analog filter

5,50

Power amplifier

6,8 Baseband digital signal 9 Output level information 10 FIR filter 20 Predistorter 21 Operating point setting circuit 22 AMP amplitude compensation coefficient calculation unit 23 AMP phase compensation coefficient calculation unit 24 BPF phase compensation coefficient offset unit 30 Modulator 40 BPF
100 Transmitter circuit

Claims

A compensation coefficient calculation unit that calculates a compensation coefficient from the inverse component of the nonlinear distortion generated in the power amplifier and the inverse component of the nonlinear phase characteristic of the analog filter;
A complex multiplier that performs a complex operation of the compensation coefficient calculated by the compensation coefficient calculator and an input baseband digital signal to compensate for nonlinear distortion of the baseband digital signal;
A nonlinear distortion compensation circuit comprising:
The compensation coefficient calculation unit
An amplitude compensation coefficient calculating unit that calculates an inverse characteristic related to an amplitude characteristic of nonlinear distortion generated in the power amplifier as an amplitude compensation coefficient;
A phase compensation coefficient calculation unit that calculates a phase compensation coefficient from the inverse characteristic related to the phase characteristic of the nonlinear distortion generated in the power amplifier and the inverse characteristic of the nonlinear phase characteristic of the analog filter;
The nonlinear distortion compensation circuit according to claim 1, comprising:
The compensation coefficient calculation unit includes an amplitude compensation coefficient that is an inverse characteristic related to an amplitude characteristic of a nonlinear distortion generated in the power amplifier, an inverse characteristic related to a phase characteristic of the nonlinear distortion generated in the power amplifier, and a nonlinear phase of the analog filter. 3. The nonlinear distortion compensation circuit according to claim 1, wherein the compensation coefficient is calculated by performing a complex operation with a phase compensation coefficient obtained from an inverse characteristic of the characteristic.
The compensation coefficient calculation unit relates to amplitude characteristics and phase characteristics of nonlinear distortion generated in the power amplifier, and based on inverse characteristic data held in advance and an input level of the power amplifier, the inverse characteristics of amplitude characteristics of the nonlinear distortion 4. The nonlinear distortion compensation circuit according to claim 1, wherein a first phase compensation coefficient that is an inverse characteristic of the amplitude compensation coefficient and the phase characteristic of the nonlinear distortion is calculated. 5.
The compensation coefficient calculation unit calculates a second phase compensation coefficient that is an inverse characteristic of the nonlinear phase characteristic based on inverse characteristic data stored in advance with respect to the nonlinear phase characteristic of the analog filter. The nonlinear distortion compensation circuit according to any one of claims 1 to 4.
The compensation coefficient calculation unit calculates a first phase compensation coefficient that is an inverse characteristic of the phase characteristic of the nonlinear distortion generated in the power amplifier, and calculates the second phase compensation coefficient obtained as the nonlinear phase characteristic of the analog filter. 6. The nonlinear distortion compensation circuit according to claim 1, wherein the phase compensation coefficient is calculated by adding the first phase compensation coefficient as an offset.
A transmission circuit comprising the nonlinear distortion compensation circuit according to any one of claims 1 to 6, a power amplifier, and an analog filter.
A compensation coefficient calculation step for calculating as a compensation coefficient from the inverse component of the nonlinear distortion generated in the power amplifier and the inverse component of the nonlinear phase characteristic of the analog filter;
A complex multiplication step for performing a complex operation between the compensation coefficient calculated in the compensation coefficient calculation step and an input baseband digital signal to compensate for nonlinear distortion of the baseband digital signal;
A non-linear distortion compensation method comprising:
The compensation coefficient calculating step includes:
An amplitude compensation coefficient calculating step for calculating an inverse characteristic related to an amplitude characteristic of nonlinear distortion generated in the power amplifier as an amplitude compensation coefficient;
A phase compensation coefficient calculating step for calculating a phase compensation coefficient from an inverse characteristic related to a phase characteristic of nonlinear distortion generated in the power amplifier and an inverse characteristic of a nonlinear phase characteristic of the analog filter;
The nonlinear distortion compensation method according to claim 8, further comprising:
The compensation coefficient calculating step includes an amplitude compensation coefficient that is an inverse characteristic related to an amplitude characteristic of a nonlinear distortion generated in the power amplifier, an inverse characteristic related to a phase characteristic of the nonlinear distortion generated in the power amplifier, and a nonlinear phase of the analog filter. 10. The nonlinear distortion compensation method according to claim 8, wherein the compensation coefficient is calculated by performing a complex operation with a phase compensation coefficient obtained from an inverse characteristic of the characteristic.
The compensation coefficient calculating step relates to amplitude characteristics and phase characteristics of nonlinear distortion generated in the power amplifier, and based on inverse characteristic data held in advance and an input level of the power amplifier, the inverse characteristics of amplitude characteristics of the nonlinear distortion 11. The nonlinear distortion compensation method according to claim 8, wherein the first phase compensation coefficient that is an inverse characteristic of the amplitude compensation coefficient and the phase characteristic of the nonlinear distortion is calculated.
The compensation coefficient calculating step calculates a second phase compensation coefficient that is an inverse characteristic of the nonlinear phase characteristic based on inverse characteristic data held in advance with respect to the nonlinear phase characteristic of the analog filter. The nonlinear distortion compensation method according to any one of claims 8 to 11.
The compensation coefficient calculating step calculates a first phase compensation coefficient that is the inverse characteristic of the phase characteristic of the nonlinear distortion generated in the power amplifier, and calculates the second phase compensation coefficient obtained as the nonlinear phase characteristic of the analog filter. The nonlinear distortion compensation method according to any one of claims 8 to 12, wherein the phase compensation coefficient is calculated by adding the first phase compensation coefficient as an offset.