JP5387445B2 - Predistortion compensation circuit and memory effect distortion compensation method for power amplifier - Google Patents

Description

  The present invention relates to a predistortion compensation circuit for reducing memory effect distortion in a power amplifier and a memory effect distortion compensation method for a power amplifier.

  In a high power transmission apparatus such as a television transmitter or mobile communication, a low level transmission signal is generated and amplified to a required power by a power amplifier (PA). This power amplifier not only linearly amplifies and outputs an input transmission signal, but also outputs a signal having non-linear characteristics because the amplification degree (Gain) varies depending on the level of the input signal.

  By the way, in the above-mentioned power amplifier, since the signal quality is deteriorated by the output of the signal having the nonlinear characteristic, there is a wide range of techniques for improving the signal quality by adding a signal having a characteristic opposite to the nonlinear characteristic to the transmission signal in advance. It is used. Furthermore, in recent years, not only compensation for non-linear characteristics of power amplifiers, but also pre-distortion compensation (PD: Pre-Distortion) for memory effect distortions of power amplifiers, improvement of output characteristics of power amplifiers and necessary backoff A technique for reducing the above has been studied (see, for example, Patent Document 1).

  The memory effect distortion is defined as a distortion component caused by an instantaneous change amount of the level of the modulated wave signal (amplitude component of the modulated wave signal), and many occurrence mechanisms have been studied (for example, see Non-Patent Document 1).

  Further, it has been clarified that the fluctuation factor of the power supply voltage is caused by the temporal change of the amplitude component of the modulated wave signal input to the power amplifier (for example, see Non-Patent Document 2 and Non-Patent Document 3). That is, it can be said that the memory effect distortion is correlated with the temporal change of the amplitude component of the modulated wave signal input to the power amplifier. Therefore, it is possible to cancel the distortion by adding in advance to the modulated wave signal a distortion having characteristics opposite to the distortion corresponding to this change. The temporal change in the signal level of the modulated wave signal can be represented by the gradient of the amplitude component of the modulated wave signal. The gradient of the amplitude component of the modulated wave signal can be easily calculated by taking the difference from the signal obtained by delaying the amplitude component of the modulated wave signal by a minute time.

  In addition, the predistortion compensation circuit corresponding to the memory effect distortion in the power amplifier is configured by using many multipliers in addition to the adder / subtractor and the look-up table (LUT) (for example, patents). Reference 2).

JP 2007-243549 A International Publication No. 2007/004252 Pamphlet

Adaptive predistorter type distortion compensation for amplifiers affected by even-order distortion IEICE Transactions C Vol.J87-C No.1 pp49-53 Digital predistorter for power amplifier with memory effect. IEICE Transactions B Vol.J88-B No.10 pp2062-2071 Broadband nonlinear modeling of power amplifier for communication and its application C Transactions of IEICE C Vol.J90-C No.12 pp882-893

  However, since the distortion compensation circuit of the power amplifier disclosed in Patent Document 2 described above is configured using a large number of multipliers in addition to the adder / subtractor and the lookup table, the hardware cost is high, Furthermore, there is a problem that the circuit scale increases. That is, since the distortion compensation circuit of the power amplifier directly handles the modulated wave signal, it is necessary to operate in real time, and a device that operates at high speed is required. However, a device that operates at high speed is generally expensive. Multipliers are usually expensive, but those that operate at high speed are even more expensive. The use of many such expensive multipliers inevitably increases the hardware cost.

  The present invention has been made in view of such circumstances, and provides a predistortion compensation circuit and a memory effect distortion compensation method for a power amplifier that can reliably reduce memory effect distortion in a power amplifier with a smaller hardware configuration. Objective.

  In order to achieve the above object, the present invention adds a nonlinear distortion compensation coefficient to an input modulated wave signal to compensate for the nonlinear characteristic of the power amplifier, which is a change in gain with respect to the input signal level of the power amplifier. And a memory effect distortion compensation coefficient having a characteristic opposite to the memory effect distortion of the power amplifier according to the gradient of the modulation wave amplitude component in advance, and the modulation wave signal subjected to nonlinear distortion compensation by the nonlinear distortion compensation unit Along with calculating the amplitude component, a delay component obtained by delaying the calculated amplitude component by a predetermined time is obtained, and further, a difference between the amplitude component and the delay component is calculated to obtain a gradient of the amplitude component, and according to the obtained gradient A memory effect distortion compensator for adding the memory effect distortion compensation coefficient to the modulated signal subjected to nonlinear distortion compensation; an input modulated wave signal; and an output of the power amplifier A nonlinear distortion compensation coefficient calculation unit for calculating the nonlinear distortion compensation coefficient based on the item, a distortion compensation circuit before having a.

  The present invention also includes a first nonlinear distortion compensation step of adding a nonlinear distortion compensation coefficient to the input modulated wave signal to compensate for the nonlinear characteristic of the power amplifier, which is a change in gain with respect to the input signal level of the power amplifier, The amplitude of the modulated wave signal having a memory effect distortion compensation coefficient having a characteristic opposite to the memory effect distortion of the power amplifier in accordance with the gradient of the modulated wave amplitude component and subjected to nonlinear distortion compensation in the first nonlinear distortion compensation step A component is calculated, a delay component obtained by delaying the calculated amplitude component by a predetermined time is obtained, a difference between the amplitude component and the delay component is calculated to obtain a gradient of the amplitude component, and a response according to the obtained gradient A memory effect distortion compensation step of adding the memory effect distortion compensation coefficient to the modulated signal subjected to nonlinear distortion compensation; an input modulated wave signal; and an output signal of the power amplifier A nonlinear distortion compensation coefficient calculation step of calculating the nonlinear distortion compensation coefficient based a memory effect distortion compensation method of a power amplifier having a.

  According to the present invention, distortion due to instantaneous change components of input power of the power amplifier is compensated, so that memory effect distortion of the power amplifier can be reduced. In addition, since the circuit can be configured without using a multiplier, the circuit scale can be reduced as compared with a distortion compensation circuit that uses many multipliers, and the hardware cost can be reduced.

1 is a block diagram showing a schematic configuration of a predistortion circuit according to an embodiment of the present invention. The block diagram which shows schematic structure of the memory effect distortion compensation part of FIG. The block diagram which shows schematic structure of the memory effect distortion compensation coefficient calculating part of FIG.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments for carrying out the invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a predistortion compensation circuit according to an embodiment of the present invention. In the figure, the predistortion circuit 1 of the present embodiment mainly uses a look-up table and an adder / subtracter to reduce memory effect distortion in the power amplifier 50. The non-linear distortion compensator 10; The memory effect distortion compensation unit 20, the nonlinear distortion compensation coefficient calculation unit 30, and the memory effect distortion compensation coefficient compensation unit 40 are configured.

The non-linear distortion compensation unit 10 compensates for the non-linear characteristic of the power amplifier 50. The non-linear distortion compensation coefficient C ₁ calculated by the non-linear distortion compensation coefficient calculation unit 30 is input to the modulated wave signal X ₁ (t). Is added, nonlinear distortion compensation coefficient C ₁ is added to modulated wave signal X ₁ (t) to perform nonlinear compensation, and nonlinearly compensated modulated wave signal X ₂ (t) is output. Here, the non-linear characteristic of the power amplifier 50 is a change in gain with respect to the input signal level of the power amplifier 50.

The memory effect distortion compensator 20 compensates for the memory effect of the power amplifier 50 (distortion with respect to temporal change of the input signal of the power amplifier 50), and the modulated wave signal X ₂ ( t), a memory effect distortion compensation coefficient (amount of distortion compensation) C ₂ calculated by the memory effect distortion compensation coefficient calculation unit 40 is input, and the memory effect distortion compensation coefficient C ₂ is converted into the modulated wave signal X ₂ ( In addition to t), memory effect distortion compensation is performed, and a modulated wave signal X ₃ (t) compensated for memory effect distortion is output.

FIG. 2 is a block diagram showing a schematic configuration of the memory effect distortion compensator 20. In the figure, a memory effect distortion compensation unit 20 includes a first amplitude component detection circuit 21, a first delay device 22, a first subtracter 23, a look-up table (LT) 24, and an adder 25. And is configured. The first amplitude component detection circuit 21 calculates the amplitude component of the modulated wave signal X ₂ (t) compensated for nonlinear distortion, and outputs a signal of the calculated amplitude component. The first delay device 22 delays the signal output from the first amplitude component detection circuit 21 by time τ. First subtractor 23, and the amplitude component of the modulated wave signal X _{2 (t)} output from the first amplitude component detector 21, the modulated wave which is delayed by the first delay unit 22 the signal X _{2 (t} The difference between the amplitude component of) and the delay component is calculated and output. By calculating the difference between the amplitude component of X ₂ (t) of the modulated wave signal and its delay component, the gradient of the amplitude component of the modulated wave signal X ₂ (t) can be calculated.

The look-up table 24 stores in advance a memory effect distortion compensation coefficient C ₂ having characteristics opposite to the memory effect distortion of the power amplifier 50 corresponding to the gradient of the modulated wave amplitude component, and the amplitude of the modulated wave signal X ₂ (t). and it outputs the memory effect distortion compensation coefficients C ₂ corresponding to the gradient of the component. As the memory effect distortion compensation coefficient C _2, a value calculated by the memory effect distortion compensation coefficient calculation unit 40 is used. The adder 25 adds the memory effect distortion compensation coefficient C ₂ read from the lookup table 24 to the modulated wave signal X ₂ (t).

Returning to FIG. 1, the nonlinear distortion compensation coefficient calculation unit 30 calculates a nonlinear distortion compensation coefficient C ₁ used in each of the nonlinear distortion compensation unit 10 and the memory effect distortion compensation coefficient calculation unit 40. That is, the nonlinear distortion compensation coefficient calculation unit 30 receives the modulated wave signal X ₁ (t) and also receives the output signal Y ₁ (t) of the power amplifier 50, and the nonlinear distortion compensation unit 10 and the memory effect distortion compensation coefficient. A nonlinear distortion compensation coefficient C ₁ used in each of the calculation units 40 is calculated.

The memory effect distortion compensation coefficient calculation unit 40 calculates a memory effect distortion compensation coefficient C ₂ used in the memory effect distortion compensation unit 20. In other words, the memory effect distortion compensation coefficient calculation unit 40 receives the modulated wave signal X ₂ (t) output from the nonlinear distortion compensation unit 10 and the nonlinear distortion compensation coefficient C calculated by the nonlinear distortion compensation coefficient calculation unit 30. ₁ and the output signal Y ₁ (t) of the power amplifier 50 is input, and the memory effect distortion is based on the modulated wave signal X ₂ (t), the nonlinear compensation coefficient C ₁ and the output signal Y ₁ (t) calculating a compensation factor _{C 2.}

FIG. 3 is a block diagram illustrating a schematic configuration of the memory effect distortion compensation coefficient calculation unit 40. In the figure, a memory effect distortion compensation coefficient calculation unit 40 includes a non-linear distortion compensation circuit 41, a second amplitude component detection circuit 42, a second delay unit 43, a second subtractor 44, and a third subtractor 44. A subtractor 45 and a statistical processing unit 46 are provided. The nonlinear distortion compensation circuit 41 has the same circuit configuration as that of the nonlinear distortion compensation unit 10 shown in FIG. Nonlinear distortion compensating circuit 41 to compensate nonlinear distortion of the output signal Y ₁ in addition to _(t) output signal Y ₁ of the power amplifier 50 the non-linear distortion compensation coefficients C _{1 (t).} The second amplitude component detection circuit 42, the second delay unit 43, and the second subtractor 44 are the first amplitude component detection circuit 21, the first delay unit 22, and the first subtracter 23 shown in FIG. Thus, the gradient of the amplitude component of the modulated wave signal X ₂ (t) is output from the second subtractor 44.

The third subtractor 45 calculates the difference between the modulated wave signal X ₂ (t) and the output signal Y ₁ (t) of the power amplifier 50 subjected to nonlinear distortion compensation processing by the nonlinear distortion compensation circuit 41. That is, the input / output error component of the power amplifier 50 is calculated. The difference does not include a non-linear component, and only the difference due to memory effect distortion is extracted. The statistical processing circuit 46 holds a large amount of error signal data with respect to the gradient of the amplitude component of the modulated wave signal, and the gradient of the amplitude component of the modulated wave signal X ₂ (t) output from the second subtractor 44. The relationship with the difference signal output from the third subtracter 45 is approximated as an N (N: integer) order function. This approximation is a transfer function of the memory effect distortion of the power amplifier 50. A compensation coefficient that is the inverse characteristic of this transfer function is obtained and output. The statistical processing circuit 46 can also obtain the compensation coefficient using another method such as an LMS (Least Mean Square) algorithm.

  Although the memory effect distortion compensation unit 20 and the memory effect distortion compensation coefficient calculation unit 40 have been described in detail, the nonlinear distortion compensation unit 10, the nonlinear distortion distortion compensation coefficient calculation unit 30, and the power amplifier 50 are well known to those skilled in the art. Further, since they are not directly related to the present invention, their detailed configuration is omitted.

Next, the operation of the predistortion circuit 1 of this embodiment will be described.
When the modulated wave signal X ₁ (t), which is a target signal for power amplification, is given to the nonlinear distortion compensator 10, the nonlinear distortion compensator 10 performs nonlinear characteristics of the power amplifier 50 (with respect to the input power of the power amplifier 50. The inverse characteristic of the component due to the gain characteristic) is added to the modulated wave signal X ₁ (t). The nonlinear distortion compensation coefficient C ₁ added to the modulated wave signal X ₁ (t) is given by the nonlinear distortion compensation coefficient calculation unit 30.

The modulated wave signal X ₂ (t) after nonlinear distortion compensation by the nonlinear distortion compensation unit 10 is given to the memory effect distortion compensation unit 20, and the memory effect distortion compensation unit 20 has a memory effect distortion characteristic (power) of the power amplifier 50. A distortion characteristic with respect to an instantaneous change amount of input power of the amplifier 50) and an inverse characteristic are added to the modulated wave signal X ₂ (t). The memory effect distortion compensation coefficient C ₂ added to the modulated wave signal X ₂ (t) is given from the memory effect distortion compensation coefficient calculation unit 40.

In the memory effect distortion compensator 20, the first amplitude component detector 21 detects the amplitude component of the modulated wave signal X ₂ (t), and the first delay unit 22 delays the signal by time τ, ₂ calculates the difference between the amplitude component of the modulated wave signal X ₂ (t) and its delay component. By calculating the difference between the amplitude component of modulated wave signal X ₂ (t) and its delay component, the gradient of the amplitude component of modulated wave signal X ₂ (t) is obtained. A memory effect distortion compensation coefficient corresponding to the obtained gradient of the amplitude component is read from the lockup table 24, and the first adder 25 adds it to the modulated wave signal X ₂ (t). Through these series of operations, memory effect distortion compensation is performed on the modulated wave signal X ₁ (t).

As described above, according to the predistortion circuit 1 of the present embodiment, the memory effect distortion compensation unit 20 for compensating for the memory effect distortion is provided in the front stage of the power amplifier 50, and the memory effect given to the memory effect distortion compensation unit 20 is also provided. the memory effect distortion compensation coefficient calculation unit 40 that calculates the distortion compensation coefficients C ₂ is provided, the memory effect distortion compensation unit 20 has a memory effect distortion opposite characteristics of the power amplifier 50 in accordance with the gradient of the pre-modulation wave amplitude component A lookup table 24 that stores memory effect distortion compensation coefficients, a first amplitude component detection circuit 21 that calculates an amplitude component of the modulated wave signal X ₂ (t) that has undergone nonlinear distortion compensation by the nonlinear distortion compensation unit 10, and a first delay unit 22 to the amplitude component of the first amplitude component detector 21 modulated wave signal X ₂ calculated in _(t) is delayed by a predetermined time, calculated by the first amplitude component detector 21 First subtraction to obtain the slope of the amplitude component of the modulated wave signal X _{2 (t)} of the amplitude component and by calculating the difference between the obtained delay element in the first delay unit 22 modulated wave signal X _{2 (t)} The memory effect distortion compensation coefficient C ₂ corresponding to the gradient of the amplitude component of the modulated wave signal X ₂ (t) obtained by the comparator 23 and the first subtracter 23 is read out from the lookup table 24 and nonlinear distortion compensation is performed. And an adder 25 for adding to the modulated wave signal X ₂ (t). Therefore, the memory effect distortion of the power amplifier 50 can be reduced by compensating the distortion with respect to the instantaneous change component of the input power of the power amplifier 50. In addition, since the circuit can be configured without using a multiplier, the circuit scale can be reduced as compared with a distortion compensation circuit that uses many multipliers, and the hardware cost can be reduced.

  In addition, since the memory effect distortion compensation coefficient calculation unit 40 can be configured without using a multiplier, the circuit scale can be reduced and the hardware cost can be reduced as compared with a distortion compensation circuit using many multipliers. .

  The present invention can be applied to a power amplifier or the like of a transmitter for television broadcasting or a base station of a mobile phone.

DESCRIPTION OF SYMBOLS 1 Predistortion compensation circuit 10 Nonlinear compensation part 20 Memory effect distortion compensation part 21 1st amplitude component detection circuit 22 1st delay device 23 1st subtractor 24 Look-up table 25 Adder 30 Nonlinear compensation coefficient calculating part 40 Memory effect distortion compensation coefficient calculation unit 41 Non-linear distortion compensation circuit 42 Second amplitude component detection circuit 43 Second delay device 44 Second subtractor 45 Third subtractor 46 Statistical processing circuit 50 Power amplifier

Claims (10)

A non-linear distortion compensation unit that adds a non-linear distortion compensation coefficient to the input modulated wave signal to compensate for the non-linear characteristic of the power amplifier, which is a change in gain with respect to the input signal level of the power amplifier;
A memory effect distortion compensation coefficient having a characteristic opposite to the memory effect distortion of the power amplifier according to the gradient of the modulation wave amplitude component in advance, and the amplitude component of the modulation wave signal subjected to nonlinear distortion compensation by the nonlinear distortion compensation unit And calculating a delay component obtained by delaying the calculated amplitude component by a predetermined time, and further calculating a difference between the amplitude component and the delay component to obtain a gradient of the amplitude component, and the memory corresponding to the obtained gradient A memory effect distortion compensation unit for adding an effect distortion compensation coefficient to the modulated wave signal subjected to nonlinear distortion compensation;
A nonlinear distortion compensation coefficient calculator that calculates the nonlinear distortion compensation coefficient based on the input modulated wave signal and the output signal of the power amplifier;
A predistortion circuit comprising: The memory effect distortion compensation unit
A lookup table storing a memory effect distortion compensation coefficient having a characteristic opposite to the memory effect distortion of the power amplifier according to the gradient of the modulation wave amplitude component in advance;
A first amplitude component detection circuit that calculates an amplitude component of the modulated wave signal that has been nonlinear distortion compensated by the nonlinear distortion compensator;
A first delay device for delaying the amplitude component of the modulated wave signal calculated by the first amplitude component detection circuit by a predetermined time;
The difference between the amplitude component of the modulated wave signal calculated by the first amplitude component detection circuit and the delay component obtained by the first delay unit is calculated to obtain the gradient of the amplitude component of the modulated wave signal. A first subtractor to obtain;
The memory effect distortion compensation coefficient corresponding to the gradient of the amplitude component of the modulated wave signal obtained by the first subtracter is read from the lookup table and added to the nonlinear wave compensated modulated wave signal And
The predistortion circuit according to claim 1, comprising: The memory effect distortion compensation coefficient is calculated based on the nonlinear distortion compensated modulated wave signal, the nonlinear distortion compensation coefficient, and the output signal of the power amplifier, and applied to the memory effect distortion compensation unit. The predistortion circuit according to claim 1, further comprising an arithmetic unit. The memory effect distortion compensation coefficient calculator is
A nonlinear distortion compensation circuit that adds a nonlinear distortion compensation coefficient calculated by the nonlinear distortion compensation unit to an output signal of the power amplifier to compensate for a nonlinear characteristic of the power amplifier that is a change in gain with respect to an input signal level of the power amplifier. When,
A second amplitude component detection circuit that calculates an amplitude component of the modulated wave signal that has been nonlinear distortion compensated by the nonlinear distortion compensator;
A second delayer that delays the amplitude component of the modulated wave signal calculated by the second amplitude component detection circuit by a predetermined time;
The difference between the amplitude component of the modulated wave signal calculated by the second amplitude component detection circuit and the delay component obtained by the second delay unit is calculated to obtain the gradient of the amplitude component of the modulated wave signal. A second subtractor to obtain;
A third subtractor for calculating a difference between the modulated wave signal subjected to nonlinear distortion compensation by the nonlinear distortion compensation unit and the output signal of the power amplifier subjected to nonlinear distortion compensation by the nonlinear distortion compensation circuit;
Statistical processing is performed on the gradient of the amplitude component of the modulated wave signal calculated by the second subtractor and the error signal of the input / output signal of the power amplifier calculated by the third subtractor, and the memory effect distortion compensation coefficient A statistical processing circuit to obtain
The predistortion compensation circuit according to claim 1, further comprising: The statistical processing circuit includes:
A large number of error signal data with respect to the gradient of the modulation wave amplitude component are held, and the relationship between the gradient of the modulation wave amplitude component and the error signal is approximated as a function of N (N: integer) order, and the memory effect distortion of the power amplifier 5. A predistortion circuit according to claim 4, wherein a memory effect distortion compensation coefficient having an inverse characteristic of the obtained transfer function is obtained. A first nonlinear distortion compensation step of adding a nonlinear distortion compensation coefficient to the input modulated wave signal to compensate for a nonlinear characteristic of the power amplifier, which is a change in gain with respect to an input signal level of the power amplifier;
A modulation effect signal having a memory effect distortion compensation coefficient having a characteristic opposite to that of the memory effect distortion of the power amplifier in accordance with the gradient of the modulation wave amplitude component, and having undergone nonlinear distortion compensation in the first nonlinear distortion compensation step; Along with calculating the amplitude component, a delay component obtained by delaying the calculated amplitude component by a predetermined time is obtained, and further, a difference between the amplitude component and the delay component is calculated to obtain a gradient of the amplitude component, and according to the obtained gradient A memory effect distortion compensation step of adding the memory effect distortion compensation coefficient to the nonlinear distortion compensated modulated wave signal;
A nonlinear distortion compensation coefficient calculation step for calculating the nonlinear distortion compensation coefficient based on the input modulated wave signal and the output signal of the power amplifier;
A memory effect distortion compensation method for a power amplifier comprising: The memory effect distortion compensation step includes:
A memory effect distortion compensation coefficient storage step for storing a memory effect distortion compensation coefficient having a characteristic opposite to the memory effect distortion of the power amplifier according to the gradient of the modulation wave amplitude component in advance;
A first amplitude component detection step of calculating an amplitude component of the modulated wave signal that has been nonlinear distortion compensated in the first nonlinear distortion compensation step;
A first delaying step of delaying the amplitude component of the modulated wave signal calculated in the first amplitude component detecting step by a predetermined time;
The difference between the amplitude component of the modulated wave signal calculated in the first amplitude component detecting step and the delay component obtained in the first delay step is calculated to obtain the gradient of the amplitude component of the modulated wave signal. Obtaining a first subtraction step;
A memory effect distortion compensation coefficient corresponding to the gradient of the amplitude component of the modulated wave signal obtained in the first subtraction process is obtained from the memory effect distortion compensation coefficient storage process, and is obtained as the first nonlinear distortion compensation process. A first addition step of adding to the modulated wave signal subjected to nonlinear distortion compensation at
A memory effect distortion compensation method for a power amplifier according to claim 6, comprising:   A memory effect distortion compensation coefficient that calculates the memory effect distortion compensation coefficient based on the nonlinear distortion compensated modulated wave signal, the nonlinear distortion compensation coefficient, and the output signal of the power amplifier, and gives the memory effect distortion compensation coefficient to the memory effect distortion compensation step The memory effect distortion compensation method for a power amplifier according to claim 6, further comprising a calculation step. The memory effect distortion compensation coefficient calculation step includes:
A nonlinear distortion compensation coefficient calculated in the first nonlinear distortion compensation step is added to the output signal of the power amplifier to compensate for the nonlinear characteristic of the power amplifier, which is a change in gain with respect to the input signal level of the power amplifier. 2 nonlinear distortion compensation steps;
A second amplitude component detection step of calculating an amplitude component of the modulated wave signal that has been nonlinear distortion compensated in the first nonlinear distortion compensation step;
A second delaying step of delaying the amplitude component of the modulated wave signal calculated in the second amplitude component detecting step by a predetermined time;
The difference between the amplitude component of the modulated wave signal calculated in the second amplitude component detection step and the delay component obtained in the second delay step is calculated to obtain the gradient of the amplitude component of the modulated wave signal. A second subtraction step to obtain;
A third subtraction step for calculating a difference between the modulated wave signal subjected to nonlinear distortion compensation in the first nonlinear distortion compensation step and the output signal of the power amplifier subjected to nonlinear distortion compensation in the second nonlinear distortion compensation step; ,
Statistical processing is performed on the gradient of the amplitude component of the modulated wave signal calculated in the second subtraction step and the error signal of the input / output signal of the power amplifier calculated in the third subtraction step, and the memory effect distortion compensation coefficient Statistical processing step to obtain
A memory effect distortion compensation method for a power amplifier according to claim 6, comprising:   The statistical processing step holds a large number of error signal data with respect to the gradient of the modulated wave amplitude component, and approximates the relationship between the gradient of the modulated wave amplitude component and the error signal as a function of N (N: integer) order. The memory effect distortion compensation method for a power amplifier according to claim 9, wherein a memory effect distortion compensation coefficient having an inverse characteristic of the obtained transfer function is obtained by obtaining a memory effect distortion transfer function of the power amplifier.

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