KR101683457B1 - Apparatus for digital predistortion in power amplifier considering saturation region and method thereof - Google Patents

Abstract

The present invention relates to a digital predistortion power amplifying apparatus and method, and more particularly, to a digital predistortion power amplifying apparatus and method for calculating a parameter for digital predistortion using input and output signals of a power amplifier, And an output signal of the digital predistortion power calculating unit. The present invention relates to a digital predistortion power amplifying apparatus and method.
The present invention relates to a digital predistortion power amplifier for inputting a predistorted signal to a power amplifier so as to compensate for a nonlinear characteristic of the power amplifier, comprising: a power amplifier for amplifying and outputting an input signal; A predistortion calculator for calculating a predistortion parameter for the power amplifier using an input signal and an output signal measurement value of the power amplifier; And a predistortion applying unit for predistorting an input signal to the power amplifier using the predistortion parameter, wherein the predistortion calculating unit calculates a predistortion of the input signal and the output signal of the power amplifier, The predistortion parameter calculating unit calculates the predistortion parameter in consideration of whether or not the digital predistortion power corresponds to the digital predistortion power.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital predistortion power amplifying apparatus and a digital predistortion power amplifying apparatus,

The present invention relates to a digital predistortion power amplifying apparatus and method, and more particularly, to a digital predistortion power amplifying apparatus and method for calculating a parameter for digital predistortion using input and output signals of a power amplifier, And an output signal of the digital predistortion power calculating unit. The present invention relates to a digital predistortion power amplifying apparatus and method.

Recently, various communication systems have been utilized due to the development of communication technology and popularization of communication service. In a communication system, a power amplifier is an essential component to amplify a signal into a high-power signal for transmission. In general, a power amplifier operates in a low power non-saturation region that exhibits a linear characteristic without being driven in a saturation region that can produce high output due to non-linear characteristics. If non-linear distortion is severe, not only the signal quality may be degraded, but also harmonic interference may be increased due to an increase in harmonic signals. When the power amplifier is driven in a non-saturation region of low power rather than in a saturation region, the linear characteristic can be secured, but the power efficiency of the power amplifier is lowered to about 10 to 20%.

On the other hand, various linearization techniques have been proposed to improve the linear characteristics of the power amplifier and improve the power efficiency. The digital pre-distortion (DPD) method has a simple structure, few components, It is known as an effective technique for linearizing power amplifiers and improving power efficiency. Digital predistortion (DPD) is a technique for linearizing a nonlinear power amplifier by finding the digital predistortion characteristic corresponding to the inverse function of a nonlinear power amplifier and using it to distort the digital signal in advance. On the other hand, Korean Patent Laid-Open Publication No. 10-2013-0039886 (March 23, 2013) detects and distorts components distorted by the nonlinear characteristics of the power amplifier, and furthermore, demodulates the feedback loop And a predistortion device which performs a function of the predistorter.

In order to calculate the inverse function of the power amplifier characteristic function, that is, the predistortion characteristic according to the related art, information about the output signal together with the input signal of the power amplifier is required, so that a feedback signal of the output signal is used. Then, a processor for performing a complex calculation on the input signal and the feedback signal of the power amplifier is used to perform a calculation for finding the predistortion characteristic from the input signal and the feedback signal. More specifically, an adaptive algorithm is used for an input signal and a feedback signal of a power amplifier to calculate a predistortion coefficient value that can constitute an inverse function of a power amplifier characteristic function.

Accordingly, in the adaptive algorithm, the predistortion coefficient is calculated in such a manner that the inverse function of the power amplifier characteristic function to be gradually calculated while gradually updating the predistortion coefficient with respect to a plurality of pieces of data. When an adaptive algorithm is performed on a sufficient number of sample data, the distortion is converged to an appropriate predistortion coefficient. Therefore, the predistortion is performed on the power amplifier by applying the calculated predistortion coefficient value.

However, when digital predistortion is performed on the power amplifier according to the above-described conventional technique, the adaptive algorithm fails to converge to an appropriate coefficient value due to the data in the saturation region where the nonlinear characteristic is strong, and an incorrect coefficient value is calculated There arises a problem that the linearization of the power amplifier can not be performed properly. Particularly, when the weight of data in the saturation region is large, the effect on the calculated predistortion coefficient becomes large, and the linear characteristic of the power amplifier may be deteriorated to a great extent.

In addition, when digital predistortion is performed according to the related art, a predistortion coefficient value is calculated using an adaptive algorithm or the like for a plurality of data. Therefore, An apparatus is required, which may increase the cost of the product and increase the size of the power amplifier.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art, and it is an object of the present invention to provide a power amplifier, And to provide a predistortion power amplifying apparatus and method capable of preventing a distortion of a power amplifier.

Another object of the present invention is to provide a predistortion power amplifying apparatus and method capable of improving the calculation complexity by calculating predistortion parameters from a plurality of data when predistorting a power amplifier according to the prior art.

According to one aspect of the present invention, there is provided a digital predistortion power amplifier for inputting a predistorted signal to a power amplifier so as to compensate for a nonlinear characteristic of the power amplifier, A power amplifier for amplifying and outputting an input signal; A predistortion calculator for calculating a predistortion parameter for the power amplifier using an input signal and an output signal measurement value of the power amplifier; And a predistortion applying unit for predistorting an input signal to the power amplifier using the predistortion parameter, wherein the predistortion calculating unit calculates a predistortion of the input signal and the output signal of the power amplifier, And the predistortion parameter calculating unit calculates the predistortion parameter by considering whether or not the predistortion parameter satisfies a predetermined condition.

Here, in calculating the predistortion parameter for the power amplifier, the predistortion calculation unit may exclude an input signal and an output signal measurement value when the power amplifier corresponds to a saturation region.

In addition, the predistortion parameter may be a coefficient capable of forming an inverse function with respect to a characteristic function of the power amplifier.

In calculating the predistortion parameter for the power amplifier, the predistortion calculator may assign a weight less than 1 to the input signal and the output signal measurement value when the power amplifier corresponds to a saturation region can do.

In determining whether the input signal and the output signal measurement value of the power amplifier correspond to a saturation region, the predistortion calculation unit may determine whether the input signal and the output signal measurement value correspond to a region where the output signal does not increase by more than a predetermined reference value Can be determined as a saturated region.

In the predistortion calculation unit, it is determined whether the input signal and the output signal measurement value of the power amplifier correspond to a saturation region. When the input signal is greater than the input power corresponding to P1dB, It can be judged to be applicable.

According to another aspect of the present invention, there is provided a digital predistortion method in a power amplifying apparatus for inputting a predistorted signal to a power amplifier so as to compensate for a nonlinear characteristic of the power amplifier, A predistortion calculating step of calculating a predistortion parameter for the power amplifier using an input signal and an output signal measurement value of the power amplifier; And a predistortion applying step of predistorting an input signal to the power amplifier using the predistortion parameter. In the predistortion calculation step, an input signal and an output signal measurement value of the power amplifier are saturated, And the predistortion parameter calculating unit calculates the predistortion parameter by taking into account whether or not it corresponds to the region.

Here, in calculating the predistortion parameter for the power amplifier, the predistortion calculating step may exclude an input signal and an output signal measurement value when the power amplifier corresponds to a saturation region.

According to the present invention, in calculating parameters for digital predistortion using input and output signals of a power amplifier, parameters for digital predistortion are calculated in consideration of input and output signals when the power amplifier operates in a saturation region The linearity and the power efficiency of the power amplifier can be improved.

According to the present invention, in calculating the parameters for digital predistortion using the input and output signals of the power amplifier, the power amplifier input and output signals in the case where the power amplifier operates in the saturation region are excluded, The calculation complexity for calculating the predistortion parameter can be reduced by calculating the parameter.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 is a block diagram of a digital predistortion power amplifier according to an embodiment of the present invention.
2 is a view for explaining a saturation region in a digital predistortion power amplifier according to an embodiment of the present invention.
3 is a view for explaining a saturation region in a digital predistortion power amplifier according to another embodiment of the present invention.
4 is a flowchart of a digital predistortion method in a power amplifying apparatus according to an embodiment of the present invention.
5 is a flowchart of an algorithm of a digital predistortion method in a power amplifying apparatus according to an embodiment of the present invention.
6 is a graph of a power frequency density measurement for an output signal in a digital predistortion power amplifier according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments will be described in detail below with reference to the accompanying drawings.

The following examples are provided to aid in a comprehensive understanding of the methods, apparatus, and / or systems described herein. However, this is merely an example and the present invention is not limited thereto.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intention or custom of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification. The terms used in the detailed description are intended only to describe embodiments of the invention and should in no way be limiting. Unless specifically stated otherwise, the singular form of a term includes plural forms of meaning. In this description, the expressions "comprising" or "comprising" are intended to indicate certain features, numbers, steps, operations, elements, parts or combinations thereof, Should not be construed to preclude the presence or possibility of other features, numbers, steps, operations, elements, portions or combinations thereof.

It is also to be understood that the terms first, second, etc. may be used to describe various components, but the components are not limited by the terms, and the terms may be used to distinguish one component from another .

First, a digital predistortion power amplifying apparatus and method according to an embodiment of the present invention will be outlined. The digital predistortion power amplifier according to an embodiment of the present invention is a digital predistortion power amplifier for inputting a predistorted signal to a power amplifier so as to compensate for a nonlinear characteristic of the power amplifier, A predistortion calculator for calculating a predistortion parameter for the power amplifier using an input signal and an output signal measurement value of the power amplifier, and a predistorter for predicting an input signal to the power amplifier using the predistortion parameter, Distorted predistortion applying section.

At this time, the predistortion calculation unit can calculate the predistortion parameter by considering whether the input signal and the output signal measurement value of the power amplifier correspond to a saturation region. Since the nonlinear characteristic of the power amplifier greatly increases when the power amplifier operates in the saturation region, the predistortion parameter for the power amplifier is calculated in consideration of whether the power amplifier input signal and the output signal correspond to the saturation region So that the power amplifier can be more effectively linearized by the calculated predistortion parameter.

Hereinafter, exemplary embodiments of a digital predistortion power amplifier and method considering a saturation region according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 1 illustrates a configuration diagram of a digital predistortion power amplifier 100 according to an embodiment of the present invention. 1, the digital predistortion power amplifier 100 according to an embodiment of the present invention includes a baseband circuit unit 110 for predistorting a baseband digital signal and converting the digital signal into an analog signal and outputting the analog signal, A predistorter 120 for calculating a predistortion parameter for the amplifier, a frequency converter 130 for frequency-converting a baseband signal into an RF frequency band, a high-power signal And a feedback signal branching unit 150 for branching a part of output signals of the power amplifier 140 to generate a feedback signal.

Referring to FIG. 1, the digital predistortion power amplifier 100 according to an embodiment of the present invention will be described in more detail as follows.

Predistortion may be performed by predistorting (i.e., compensating) the input signal of the power amplifier 140 using an inverse of the characteristic function of the power amplifier 140 to compensate for the non-linearity of the characteristic function of the power amplifier 140 Give something. Since the power amplifier 140 used in the communication system typically amplifies and outputs a signal of an RF frequency band for wireless transmission, the input signal and the output signal of the power amplifier 140 are usually converted into a high frequency signal .

However, in digital predistortion, the input signal of the power amplifier 140 is predistorted at the digital signal level, and therefore the predistortion parameter for the power amplifier 140 is also generated at the digital signal level.

1, the digital signal generated by the base signal generator 112 is passed through the predistorter 114 and converted into a predistortion using the predistorter parameter for the power amplifier 140. [ And then converted into an analog signal by a digital-analog converter 116 such as a digital to analog converter (DAC). Then, the signal is converted into an RF frequency signal through a frequency up-converter 132 such as an up-converter, and then amplified through a power amplifier 140 and output.

If the predistortion parameter applied in the predistortion applying unit 114 appropriately models the inverse of the characteristic function of the power amplifier 140, the signal output from the power amplifier 140 may be an output signal having a good linearity . The output signal of the power amplifier 140 is branched by a feedback signal branching unit 150 such as a directional coupler so that a frequency down-converting unit 134 such as a down- To the baseband frequency. The signal may be converted into a digital signal through an analog-to-digital converter 118 such as an analog-to-digital converter (ADC) and transferred to the storage device 124 of the predistortion calculator 120 and stored.

Also, a signal used as an input signal of the power amplifier 140, which is output from the predistorter 114, is also stored in the storage device 124 of the predistorter 120, Lt; / RTI > can be used to calculate the predistortion parameter. The predistortion data processor 122 of the predistortion calculator 120 uses the input signal and the output signal of the power amplifier 140 stored in the storage device 124 to construct an inverse function of the characteristic function of the power amplifier The predistortion parameter that can be obtained is calculated. For example, when the inverse function is represented by a predetermined polynomial or the like, an inverse function for the power amplifier 140 is constructed by calculating a coefficient for the polynomial equation or the like as the predistortion parameter, It becomes possible to distort the pre-distortion.

In addition, since the characteristics of the power amplifier 140 vary with time, power, and temperature, it is necessary to continuously find the inverse function while tracking the nonlinear characteristic. To this end, a circuit for feedbacking the power amplifier output as shown in FIG. 1 is required .

In addition, the digital predistortion power amplifier 100 according to an embodiment of the present invention may be configured such that the input signal and the output signal measurement values stored in the storage device 124 such as the memory of the predistorter 120 correspond to a saturation region The inverse of the calculated predistortion parameter and the characteristic function of the power amplifier 140 that can be formed from the calculated predistortion parameter can effectively compensate the linear characteristic of the power amplifier 140 do.

For example, as can be seen from FIG. 2, even if the power measurement value of the input signal increases by a certain amount, a region where the power measurement value of the output signal does not increase beyond a predetermined reference value can be determined as a saturation region.

In this case, even when the power measurement value of the input signal increases to more than Max_W in FIG. 2, the power measurement value of the output signal does not increase and becomes saturated, so that the nonlinear characteristic of the output signal may be very large in the saturation state Even if only a small number of the input signal and the output signal measurement value in the saturated state are present, the influence on the predistortion parameter calculated accordingly can be very large.

Accordingly, in calculating the predistortion parameter for the power amplifier 140 as an embodiment of the present invention, the input signal and the output signal measurement value in the case where the power amplifier 140 is in the saturation region, It is possible to block the influence of the predistortion parameter and further improve the linearity in the power amplifier 140. [

Alternatively, in calculating the predistortion parameter for the power amplifier 140, a weight value smaller than 1 may be assigned to the input signal and the output signal measurement value when the power amplifier 140 is in the saturation region, The measured value of the signal and the measured value of the output signal may be taken into account so that the nonlinear characteristic of the power amplifier 140 can be prevented from greatly increasing.

In an embodiment of the present invention, a region having a P1dB (1 dB compression point) or more of the power amplifier 140 as shown in FIG. 3 may be defined as a saturation region. In this case, by setting the saturation region to be wider as compared with the case of FIG. 2, the linearity in the non-power amplifier 140 in the predistortion parameter can be further improved.

On the other hand, in this case, since the input signal and the output signal measurement value data in the saturation region are relatively reduced, it may be difficult to improve the linear characteristic in the saturation region. Therefore, It is preferable to set an appropriate region as a saturation region.

FIG. 4 illustrates a flowchart of a digital predistortion method in a power amplifier according to an embodiment of the present invention. As shown in FIG. 4, the digital predistortion method in the power amplifying apparatus according to an embodiment of the present invention includes a step S410 of obtaining a measured value of an input signal of the power amplifier 140 and an output signal thereto, Calculating (S420) predistortion parameters for the power amplifier (140) from measurements of the input signal and the output signal, taking into account whether the input signal and output signal measurements correspond to a saturation region And predistorting the input signal to the power amplifier 140 using a parameter (S430).

In calculating the predistortion parameter for the power amplifier 140, the power amplifier 140 may be set to a saturation (for example, the power amplifier 140) in the same manner as in the predistortion power amplifier according to the embodiment of the present invention the linear characteristics of the power amplifier 140 can be further improved by excluding the input signal and the output signal measurement values corresponding to the saturation region.

Alternatively, in calculating the predistortion parameter for the power amplifier 140 in step S420, the power amplifier 140 may measure the input signal and the output signal when the power amplifier 140 corresponds to a saturation region, And may reduce the influence of the input and output signals and improve the linear characteristics of the power amplifier 140 in a weighted manner

At this time, in determining whether the input signal and the output signal measurement value of the power amplifier 140 correspond to a saturation region, a region where the output signal does not increase by more than a predetermined reference value, Or determine the saturation region based on P1dB of the power amplifier 140. [

FIG. 5 illustrates a flowchart for explaining the algorithm of the digital predistortion method in the power amplifier according to the embodiment of the present invention. 1, the predistortion data processor 122 obtains a predistortion coefficient w using N input signals x (n) and N feedback signals y (n). At this time, first, the saturation power limiting the update of the predistortion coefficient value is set to the max_W value, and the predistortion coefficient value is initialized to w = [0, ..., 0] ^T. The max_W value is preferably set to a magnitude value of the saturation power of the power amplifier 140, wherein the max_W value is set differently according to the characteristics of the power amplifier 140. [ Next, the predistortion coefficient value w is obtained by using an adaptive algorithm using x (n) and y (n) whose measured values are smaller than the max_W value. If the predistortion parameter (coefficient w ) calculated by using the measured value of the input measurement value included in the saturation region of the power amplifier 140 is used for predistortion, the measurement value when the input signal is included in the saturation region It also affects the measurement values not included in the saturation region, and the linearization is not properly performed. However, in the case of applying the w value calculated by a method of updating the w value by using only the samples having a max_W value or less and maintaining the w value without updating in the samples having a value of the max_W value or more to the predistortion, The linearity can be guaranteed. By limiting the updating process of the predistortion coefficient w in this manner, an optimum coefficient value w can be obtained and applied to the input signal x to provide a predistortion signal that can effectively compensate the nonlinearity of the power amplifier 140. [ . ≪ / RTI >

A more specific example is given below. First, when the predistortion applying section 114 is implemented using the (2P + 1) th order polynomial, the input signal s (n) of the predistortion applying section 114 and the output signal x (n) can be expressed by the following equation (1).

[Equation 1]

In this case, in Equation (1), the two vectors may be defined as follows.

The predistortion parameter to be calculated by the predistortion data processing unit 122 becomes a vector w constituted by the coefficients for the polynomial of the above equation (1). Accordingly, the process performed by the predistortion data processor 122 to obtain w as an embodiment of the present invention will be described as follows.

First, perform the following initialization process.

Next, an adaptive algorithm for calculating the predistortion parameter is performed as follows.

The adaptive algorithm described above is a recursive least squares (RLS) algorithm according to the prior art. To obtain w in the algorithm, an initial value of w and an initial value of P are required. Therefore, since there is no information at the initial operation step of the algorithm, that is, when n = 1, w uses a vector whose all elements are '0' as an initial value, and P uses (P + 1) Size initial matrix. Then, w and P are updated by equations (1) and (2) calculated by the adaptive algorithm during n = 1, ..., N, and converge to the optimal value gradually. However, when there is measurement data larger than the saturation power of the measurement values of the input signal and the output signal, the convergence due to the data is not properly performed, so that the accurate w can not be obtained, There may be a problem that the linearization is not performed properly.

Accordingly, in the digital predistortion method in the power amplifier according to the embodiment of the present invention, it is determined whether each value of the input signal is larger or smaller than max_W, and whether w is updated or w is maintained is determined. That is, when the magnitude of the input signal corresponding to the maximum output value of the power amplifier (140) max_W, a w value of the amplitude of the input signal measured by following the formula (1) and equation (2) only for a small data than max_W When the input signal size is larger than max_W, the previous w value is maintained, and the predistortion coefficient w that can compensate the linearity with respect to the measurement data other than the saturation region is obtained.

In the adaptive algorithm, in order to linearize the nonlinearity of the power amplifier 140, the predistortion coefficient w is continuously changed. When the measurement data over the saturation power is used, the w value which is far from the optimum value is found. The w value is updated using only the measurement data of less than the power so that a more accurate w value can be obtained for measurement data other than the saturation region. Finally, the predistortion coefficient w calculated as described above is used to predistort the input signal of the power amplifier 140 in the predistorter 114, thereby improving the linear characteristic of the power amplifier 140.

FIG. 6 illustrates a power frequency density measurement graph according to an embodiment of the present invention using an LTE signal having a bandwidth of 20 MHz. The respective spectra in FIG. 6 will be described as follows. First, the input signal of the power amplifier 140 is amplified using (a) spectrum, the output of the power amplifier 140 without applying any predistortion, (b) spectrum, input signals and output signal measurement data in all regions the output of the power amplifier 140 when the predistorter according to the conventional technique of updating the w value is applied is (c) spectrum, and finally, as an embodiment of the present invention, the power amplifier 140 is placed in the non- The output of the power amplifier 140 when applying the method of updating the w value using only the input signal and the output signal measurement data corresponding to the (d) spectrum corresponds to the spectrum.

As can be seen from FIG. 6, when N data corresponding to the saturation region is included, the spectrum (d) according to an embodiment of the present invention shows better spectral performance than the method according to the prior art It can be clearly seen that the linear characteristics of the power amplifier 140 can be improved by applying the present invention.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments described in the present invention are not intended to limit the technical spirit of the present invention but to illustrate the present invention. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

100: digital predistortion power amplifying device
110: base band circuit section
112: base signal generator
114: Predistortion application part
116: digital-analog conversion section
118: Analog-to-digital conversion section
120: predistortion calculation section
122: Predistortion data processor
124: Storage device
130: Frequency converter
132: frequency up /
134: frequency down-
140: Power amplifier
150: feedback signal divider

Claims (8)

A digital predistortion power amplifier for inputting a predistorted signal to a power amplifier so as to compensate for a nonlinear characteristic of the power amplifier,
A power amplifier for amplifying and outputting an input signal;
A predistorter for calculating a predistortion parameter for the power amplifier by storing a plurality of input signals and a plurality of output signal measurements of the power amplifier, And
And a predistortion applying unit for predistorting an input signal to the power amplifier using the predistortion parameter,
The predistortion calculator compares a plurality of input signals of the power amplifier with a plurality of output signal measurements to determine whether or not the signal corresponds to a saturation region, and outputs an input signal and an output signal measurement value corresponding to the saturation region And the predistortion parameter calculating unit calculates the predistortion parameter. delete The method according to claim 1,
Wherein the predistortion parameter is a coefficient that can form an inverse function to a characteristic function of the power amplifier. The method according to claim 1,
In the predistortion calculator,
In calculating the predistortion parameter for the power amplifier,
Wherein a weight value smaller than 1 is given to an input signal and an output signal measurement value when the power amplifier corresponds to a saturation region. The method according to claim 1,
In the predistortion calculator,
In determining whether an input signal and an output signal measurement value of the power amplifier correspond to a saturation region,
And determines an area where the output signal does not increase by more than a predetermined reference value as a saturated area even if the input signal becomes large. The method according to claim 1,
In the predistortion calculator,
In determining whether an input signal and an output signal measurement value of the power amplifier correspond to a saturation region,
And determines that the input signal corresponds to a saturation region when the input signal is greater than the input power corresponding to P1dB. A digital predistortion method in a power amplifier device for inputting a predistorted signal to a power amplifier so as to compensate for nonlinear characteristics of the power amplifier,
A predistortion calculating step of storing a plurality of input signals and a plurality of output signal measurement values of the power amplifier and using the same to calculate a predistortion parameter for the power amplifier; And
And predistorting the input signal to the power amplifier using the predistortion parameter to predistort the input signal to the power amplifier,
In the predistortion calculation step, a plurality of input signals and a plurality of output signal measurement values of the power amplifier are compared to determine whether they correspond to a saturation region, and an input signal and an output signal measurement value corresponding to a saturation region And calculating the predistortion parameter by excluding the predistortion parameter. delete

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