JP2010004362A - Amplifying apparatus equipped with distortion compensation function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To input an accurate level baseband signal to an amplifier circuit by reducing the influence of the input / output characteristics of the distortion compensator itself.
An input signal power measurement unit detects a power level of a transmission baseband signal before being input to a distortion compensation unit, and a distortion compensation unit uses a distortion compensation unit to compensate for distortion. After that, the power level of the transmission baseband signal 103 is detected. Then, the LUT gain adjustment unit 111 generates an adjustment value based on the detected power ratio or difference value of each power level, and the generated adjustment value is output from the LUT control unit 110. The compensation data corresponding to the control value to which the adjustment value is added is read from the LUT 112 and provided to the distortion compensation unit 102.
[Selection] Figure 1

Description

  The present invention relates to a transmission amplifying apparatus used in, for example, a base station apparatus for mobile communication, and more particularly to an amplifying apparatus having a function of compensating for nonlinear distortion generated in an amplifying circuit.

  For example, in a base station device provided in a mobile communication system that employs a wideband code division multiple access (W-CDMA) method as a radio access method, a mobile station device that is physically far away is used. Since it is necessary to make the radio signal reach, it is necessary to amplify the transmission signal by a power amplifying circuit. However, since the power amplifier circuit is an analog device, its input / output characteristics are nonlinear functions. In particular, in a region exceeding the amplification limit called a saturation point, the output power becomes substantially constant even when the input signal level increases, and nonlinear distortion occurs in the amplified transmission signal due to the influence of this nonlinear characteristic.

  For the transmission signal before amplification, a signal component outside the desired signal band can be suppressed to a low level by arranging a band limiting filter in the previous stage of the amplification circuit. However, when the nonlinear distortion described above occurs in the transmission signal output from the amplifier circuit, the signal power leaks out of the desired signal band, that is, to the adjacent channel, causing interference between adjacent channels. In particular, since the base station apparatus has high transmission power as described above, leakage of signal power to the adjacent channel is strictly regulated. For this reason, it is a big problem whether to limit the leakage power to the adjacent channel.

  Therefore, a transmission amplifying apparatus for a base station is generally provided with a distortion compensation circuit, and recently, a distortion compensation circuit adopting a feed-forward type predistortion system is becoming mainstream with an emphasis on amplification efficiency. The predistortion method compensates for non-linear distortion of the output signal of the amplifier circuit by giving the inverse characteristics of AM-AM conversion and AM-PM conversion, which are nonlinear characteristics of the amplifier circuit, to the transmission signal input to the amplifier circuit in advance. It is a method. There is a method using a distortion compensation table (Look Up Table; LUT) as one of the methods for giving the reverse characteristics (see, for example, Patent Document 1).

FIG. 6 shows an example of the configuration of a distortion compensator that employs a digital predistortion (DPD) method using an LUT. The distortion compensator (DPD processing circuit) 10 first feeds back a part of the output signal 15 of the amplifier circuit 14, and the distortion detector 17 detects the amount of distortion included in the output signal 15. Then, the LUT control unit 21 updates the distortion compensation characteristics of the LUT 22 based on the detected value of the distortion amount and the amplitude of the input baseband signal 11, and the distortion compensation unit 12 is updated based on the updated distortion compensation characteristics. Is used to control the amplitude and phase of the input baseband signal 11. The distortion-compensated baseband signal 13 whose amplitude and phase are controlled by the distortion compensator 12 is up-converted to a radio frequency by a frequency converter (not shown) and then input to the amplifier circuit 14.
Japanese Patent Laying-Open No. 2006-165856, FIG.

  However, the level of the baseband signal 11 input to the distortion compensation unit 12 may vary after the output of the distortion compensation unit 12 due to the influence of the input / output characteristics of the distortion compensation unit 12 itself. Therefore, the level of the baseband signal 11 before being input to the distortion compensator 12 is not accurately input to the amplifier circuit 14, and as a result, the level of the output signal 15 after being amplified by the amplifier circuit 14 is expected. There was a problem that the level would be different from the value of.

  The present invention has been made paying attention to the above circumstances, and its purpose is to reduce the influence of the input / output characteristics of the distortion compensator itself, and to input an accurate level baseband signal to the amplifier circuit. An object of the present invention is to provide an amplifying apparatus having a function of compensating for non-linear distortion which can be performed.

  In order to achieve the above object, one aspect of the present invention provides an amplifier circuit that amplifies and outputs a transmission signal, and a distortion that stores compensation data representing distortion compensation characteristics that are inverse to the nonlinear characteristics of the amplifier circuit. A compensation table; a distortion compensation unit that compensates the signal characteristics of the transmission signal according to compensation data read from the distortion compensation table; and inputs the transmission signal compensated for the signal characteristics to the amplifier circuit; and the amplifier circuit A first detection means for receiving a part of the transmission signal output from the feedback signal and detecting the distortion amount of the amplifier circuit from the feedback signal; the transmission signal before being input to the distortion compensator; and the distortion A second detection unit configured to detect information indicating a difference in signal level from the transmission signal after the signal characteristic is compensated by the compensation unit; and a control unit for the compensation table. Then, the control means calculates the distortion amount based on the information representing the difference between the distortion amount of the amplifier circuit detected by the first detection means and the transmission signal level detected by the second detection means. The compensation data read from the distortion compensation table is controlled so as to reduce the difference in the transmission signal level.

  Therefore, according to one aspect of the present invention, the compensation data read from the distortion compensation table includes the distortion compensation unit detected by the second detection unit in addition to the distortion amount of the amplifier circuit detected by the first detection unit. Control is performed in consideration of information representing the difference in the transmission signal level between the input and output of the. For this reason, even when the level of the transmission signal input to the distortion compensator fluctuates after distortion compensation due to the influence of the input / output characteristics of the distortion compensator itself, this fluctuation component is compensated by the compensation data. Therefore, a transmission signal after distortion compensation having the same level as that of the transmission signal before being input to the distortion compensation unit is always input to the amplification circuit, and thus the transmission signal level output from the amplification circuit is always set. It becomes possible to maintain the expected level.

  That is, according to one aspect of the present invention, the function of compensating for nonlinear distortion by reducing the influence of the input / output characteristics of the distortion compensator itself so that an accurate level baseband signal can be input to the amplifier circuit. Can be provided.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
The amplifying apparatus according to the first embodiment of the present invention is provided, for example, in a transmission system of a base station apparatus for WiMAX (Worldwide Interoperability for Microwave Access) or LTE (Long Term Evolution).

  The base station device includes a base station body, an amplification device, and a plurality of antennas. The base station main body controls communication with each mobile station existing in the communication area covered by the base station. The amplification device includes a communication unit, an amplification circuit, and a distortion compensation unit provided between the communication unit and the amplification circuit. The communication unit performs encoding processing and modulation processing on the baseband transmission data output from the base station main body, and outputs I-phase and Q-phase baseband signals. The amplifier circuit is configured by, for example, a Doherty Amplifier that combines outputs of a plurality of amplifier elements.

The distortion compensation unit has a function of compensating for non-linear distortion generated in the amplifier circuit, and is configured as follows, for example. FIG. 1 is a functional block diagram showing configurations of the distortion compensation unit and the amplifier circuit.
That is, the distortion compensation unit includes a digital predistortion (DPD) processing unit 100 using a distortion compensation table, and includes a distortion compensation unit 102, a distortion compensation table (Look up Table; LUT) 112, and a distortion detection unit 107. A distortion compensation table control unit (LUT control unit) 110, and further includes an input signal power measurement unit 108, a post-distortion signal power measurement unit 109, and an LUT gain adjustment unit 111.

  The distortion compensator 102 includes an attenuator and a phase shifter. With the attenuator and phase shifter, the amplitude of the I-phase and Q-phase transmission baseband signals (input signals) 101 output from a communication unit (not shown) and Change the phase. Then, a transmission baseband signal (distortion compensated signal) 103 with the amplitude and phase varied is output. The signal 103 after distortion compensation is up-converted to a radio frequency by a frequency converter (not shown) and then input to the amplifier circuit 104. The amplifier circuit 104 power-amplifies the input distortion-compensated signal and outputs an amplified wireless transmission signal 105.

  The LUT 112 is configured by a memory having, for example, a 10-bit address space as hardware, and this memory represents distortion compensation characteristics for compensating for AM-AM conversion and AM-PM conversion which are nonlinear characteristics of the amplifier circuit 104. Compensation data is stored in association with each of various input levels of the transmission baseband signal (input signal) 101. The distortion compensation characteristic is set to be the inverse characteristic of the nonlinear characteristic generated in the amplifier circuit 104, and the compensation data is composed of amplitude compensation data and phase compensation data.

  The LUT 112 receives the power detection value of the input signal 101 obtained by the input signal power measuring unit 108, which will be described later, and the control value output from the LUT gain adjusting unit 111, which will be described later, as addresses. The compensation data corresponding to the detected value and the amplitude compensation data and the phase compensation data corresponding to the control value are read out and given to the attenuator and phase shifter of the distortion compensator 102, whereby the attenuation amount and phase amount are obtained. Control.

  The distortion detection unit 107 detects, for example, the power value by taking out the out-of-band distortion power of the wireless transmission signal 105 output from the amplifier circuit 104 as a feedback signal, and is configured as follows, for example. That is, first, a part of the wireless transmission signal 105 output from the amplifier circuit 104 is mixed with a carrier wave signal by a mixer, the frequency is down-converted, and then passed through a band-pass filter. The output signal is further down-converted to a frequency suitable for A / D conversion by a frequency converter and converted to a digital signal by an A / D converter, and the digital signal is subjected to nonlinear distortion generated by the amplifier circuit 104. The value to be expressed (distortion amount) is input to the LUT control unit 24.

  The LUT control unit 110 is realized, for example, by causing a CPU (Central Processing Unit) to execute software. When the LUT control unit 110 receives a detection value of a distortion amount generated in the amplifier circuit 104 from the distortion detection unit 107, the LUT control unit 110 receives the received value. A control value for causing the detected value of the distortion amount to approach zero is generated, and the generated control value is output to the LUT gain adjustment unit 111 described later.

The input signal power measurement unit 108 detects the power level of the transmission baseband signal (input signal) 101 output from a communication unit (not shown), and provides the detected power value to the LUT 112 and the LUT gain adjustment unit 111.
The distortion-compensated signal power measurement unit 109 detects the power level of the distortion-compensated transmission baseband signal 103 output from the distortion compensation unit 102, and provides the detected power value to the LUT gain adjustment unit 111. .
The input signal power measurement unit 108 and the distortion-compensated signal power measurement unit 109 may be configured to detect the amplitude level or its logarithmic value instead of detecting the power level.

  The LUT gain adjustment unit 111 is realized by causing the CPU to execute software in the same manner as the LUT control unit 110, and a transmission baseband signal (input signal) 101 given from the input signal power measurement unit 108. And information representing the difference between the detected power value of the post-distortion-compensated signal power measurement unit 109 and the detected power value of the post-distortion-compensated signal 103 is calculated. As information indicating the difference, for example, a power ratio or a difference value is used. Then, the ratio or difference value between the calculated power detection values is compared with a preset threshold value, and it is determined whether or not the threshold value is exceeded. As a result of this determination, when it is determined that the ratio or difference value between the power detection values exceeds the threshold value, the adjustment value set based on the ratio or difference value between the power detection values is the LUT control. The control value output from the unit 110 is added, and the control value after the adjustment value is added is given to the LUT 112 as part of the address.

Next, a distortion compensation operation in the amplifying apparatus configured as described above will be described. FIG. 2 is a flowchart showing processing procedures and processing contents of the LUT control unit 110 and the LUT gain adjustment unit 111.
When the amplifying apparatus is activated when the base station starts or restarts, the I-phase and Q-phase baseband signals (input signals) 101 output from the communication unit are subjected to distortion compensation by the distortion compensator 102, and further illustrated in FIG. After being up-converted to a radio frequency by a frequency converter that does not, it is amplified by an amplifier circuit 104 and transmitted from an antenna (not shown).

  When the transmission operation is started, the distortion detection unit 107 captures a part of the wireless transmission signal (output signal) 105 output from the amplifier circuit 104, and the distortion power value outside the band becomes the amplifier circuit 104. It is detected as the amount of distortion generated in. The LUT control unit 110 takes in the detection value of the distortion amount obtained in the distortion detection unit 107 in step S21, and sets a control value for reducing the distortion amount based on the acquired detection value of the distortion amount in step S22. Generate by. The generated control value is output to the LUT gain control unit 111 in step S23.

  When the transmission operation is started, the power level of the transmission baseband signal (input signal) 101 before being input to the distortion compensation unit 102 is detected by the input signal power measurement unit 108, and the distortion compensation unit 102 The distortion-compensated signal power measurement unit 109 detects the power level of the transmission baseband signal 103 after distortion compensation. First, in steps S31 and S32, the LUT gain adjustment unit 111 receives the power detection value of the transmission baseband signal 101 before distortion compensation from the input signal power measurement unit 108 and the distortion compensation from the signal power measurement unit 109 after distortion compensation, respectively. The power detection value of the later transmission baseband signal 103 is captured. In step S33, the power ratio or difference value between the captured power detection values is calculated.

  Next, the LUT gain adjustment unit 111 takes in the control value output from the LUT control unit 110 in step S34, and then compares the calculated power ratio or difference value with a preset threshold value in step S35. . As a result of this comparison, if the calculated power ratio or difference value is larger than the threshold value, it is determined that the signal attenuation in the distortion compensation unit 102 is large, and the power ratio is calculated based on the power ratio or difference value in step S36. Alternatively, an adjustment value for reducing the difference value below the threshold value is generated. In step S37, the generated adjustment value is added to the control value output from the LUT control unit 110, and the control value added with the adjustment value is given to the LUT 112 as an address in step S38.

  Therefore, the compensation data is read from the area addressed by the control value to which the adjustment value is added from the LUT 112, and this compensation data is given to the distortion compensation unit. As a result, the distortion compensator 102 variably controls the amplitude and phase of the transmission baseband signal 101 based on the compensation data corresponding to the control value to which the adjustment value is added. That is, the distortion compensation unit 102 performs distortion compensation in consideration of signal attenuation by the distortion compensation unit 102 itself.

  In contrast, it is assumed that the power ratio or the difference value calculated in step S33 is equal to or less than the threshold value. In this case, the LUT gain adjustment unit 111 determines that the signal attenuation in the distortion compensation unit 102 is small, proceeds from step S35 to step S38, and directly gives the control value output from the LUT control unit 110 to the LUT 112 as an address. Therefore, in this case, compensation data is read from the area addressed by the control value to which the adjustment value is not added from the LUT 112, and this compensation data is given to the distortion compensation unit 102. Therefore, the fruit distortion compensator 102 variably controls the amplitude and phase of the transmission baseband signal 101 based on the compensation data corresponding to the control value.

  Thereafter, during the transmission operation, the distortion compensation operation is repeatedly performed at regular time intervals. FIG. 3 shows an example of control values output from the LUT gain adjustment unit 111. In the figure, A in the figure shows the control value when the attenuation amount of the transmission baseband signal between the input and output of the distortion compensator 102 is below the threshold value, and B in the figure is between the input and output of the distortion compensator 102 The control value when the amount of attenuation of the transmission baseband signal exceeds the threshold value is shown. As shown in the figure, when the attenuation amount of the transmission baseband signal between the input and output of the distortion compensation unit 102 exceeds the threshold value, the adjustment value W is added to the control value output from the LUT control unit 110. Is done.

  As described above, in the first embodiment, the input signal power measurement unit 108 detects the power level of the transmission baseband signal 101 before being input to the distortion compensation unit 102 and the distortion-compensated signal power measurement unit 109. Thus, the power level of the transmission baseband signal 103 after the distortion compensation by the distortion compensation unit 102 is detected. Then, the LUT gain adjustment unit 111 generates an adjustment value based on the detected power ratio or difference value of each power level, and the generated adjustment value is output from the LUT control unit 110. The compensation data corresponding to the control value to which the adjustment value has been added is read from the LUT 112 and provided to the distortion compensation unit 102.

Therefore, the compensation data read from the LUT 112 is detected by the power level of the transmission baseband signal 101 before being input to the distortion compensation unit 102 detected by the input signal power measurement unit 108 and the signal power measurement unit 109 after distortion compensation. Correction is performed based on the power ratio or difference value of the power level of the transmission baseband signal 103 after distortion compensation. Therefore, even when the level of the transmission signal input to the distortion compensation unit 102 fluctuates after distortion compensation due to the input / output characteristics of the distortion compensation unit 102 itself, this fluctuation component is compensated by the compensation data. The Therefore, the distortion compensation unit 102 outputs a transmission baseband signal 103 that retains the power level of the transmission baseband signal 101 before distortion compensation, whereby the power of the wireless transmission signal output from the amplifier circuit 104 is output. Can always be set to the expected value.
Further, in the first embodiment, since the LUT gain adjustment unit 111 is provided separately from the LUT control unit 110, there is an advantage that the compensation data can be adjusted without changing the existing LUT control unit 110.

(Second Embodiment)
FIG. 4 is a functional block diagram showing a configuration of a transmission amplifying apparatus according to the second embodiment of the present invention. In the figure, the same parts as those in FIG.
The DPD processing unit 200 is provided with an LUT control unit & LUT gain adjustment unit 210. The LUT control unit & LUT gain adjustment unit 210 includes one CPU (Central Processing Unit), and realizes both the LUT control function and the LUT gain adjustment function by causing the CPU to execute software.

Due to such a configuration, the DPD processing unit 200 performs the following distortion compensation control. FIG. 5 is a flowchart showing a control procedure and control contents by the LUT control unit & LUT gain adjustment unit 210.
That is, when the transmission operation is started, a part of the wireless transmission signal (output signal) 105 output from the amplification circuit 104 is captured by the distortion detection unit 107, and the distortion power value outside the band is amplified by the amplification. It is detected as a distortion amount generated in the circuit 104. The LUT control unit & LUT gain adjustment unit 210 takes in the detected value of the distortion amount obtained by the distortion detection unit 107 in step S41. In step S42, a control value for reducing the amount of distortion is generated based on the acquired detected value of the amount of distortion.

  At the same time, the power level of the transmission baseband signal 101 before being input to the distortion compensation unit 102 is detected by the input signal power measurement unit 108, and the transmission base after the distortion compensation is performed by the distortion compensation unit 102. The power level of the band signal 103 is detected by the signal power measurement unit 109 after distortion compensation. In steps S43 and S44, the LUT control unit & LUT gain adjustment unit 210 receives the power detection value of the transmission baseband signal 101 before distortion compensation from the input signal power measurement unit 108 and the signal power measurement unit 109 after distortion compensation, respectively. The power detection value of the transmission baseband signal 103 after distortion compensation is captured. In step S45, a power ratio or difference value between the captured power detection values is calculated.

  Subsequently, in step S46, the LUT control unit & LUT gain adjustment unit 210 compares the calculated power ratio or difference value with a preset threshold value. As a result of this comparison, if the calculated power ratio or difference value is greater than the threshold value, it is determined that the signal attenuation in the distortion compensation unit 102 is large, and the power ratio is determined based on the power ratio or difference value in step S47. Alternatively, an adjustment value for reducing the difference value below the threshold value is generated. In step S48, the generated adjustment value is added to the control value previously generated in step S42, and the control value added with the adjustment value is provided as an address to the LUT 112 in step S48.

  Therefore, the compensation data is read from the area addressed by the control value to which the adjustment value is added from the LUT 112, and this compensation data is given to the distortion compensation unit. For this reason, the distortion compensation unit 102 variably controls the amplitude and phase of the transmission baseband signal 101 based on compensation data corresponding to the control value to which the adjustment value is added. That is, the distortion compensation unit 102 performs distortion compensation in consideration of signal attenuation by the distortion compensation unit 102 itself.

In contrast, it is assumed that the power ratio or the difference value calculated in step S45 is equal to or less than the threshold value. In this case, the LUT control unit & LUT gain adjustment unit 210 determines that the signal attenuation in the distortion compensation unit 102 is small, and proceeds from step S46 to step S49, where the control value previously generated in step S42 is directly transferred to the LUT 112. Give as an address. Therefore, in this case, compensation data is read from the area addressed by the control value to which the adjustment value is not added from the LUT 112, and this compensation data is given to the distortion compensation unit 102. As a result, the distortion compensator 102 variably controls the amplitude and phase of the transmission baseband signal 101 based on the compensation data corresponding to the control value.
Thereafter, during the transmission operation, the distortion compensation operation is repeatedly performed at regular time intervals.

  As described above, in the second embodiment, the control value for reducing the distortion amount based on the distortion amount of the amplifier circuit 104 detected by the distortion detection unit 107 in the LUT control unit & LUT gain adjustment unit 210. Is generated based on the power ratio or difference value between the power level of the transmission baseband signal 101 before being input to the distortion compensation unit 102 and the power level of the transmission baseband signal 103 after distortion compensation. Generate adjustment values. When the power ratio or the difference value is larger than the threshold value, the generated adjustment value is added to the control value and given to the LUT 112.

Therefore, as in the first embodiment, the compensation data read from the LUT 112 includes the power level of the transmission baseband signal 101 before being input to the distortion compensation unit 102 and the transmission baseband signal 103 after distortion compensation. It is adjusted based on the power ratio or difference value between the power levels. For this reason, even when the power level of the transmission baseband signal 101 input to the distortion compensation unit 102 fluctuates after distortion compensation due to the influence of the input / output characteristics of the distortion compensation unit 102 itself, this fluctuation component is Compensated by data. Therefore, the distortion compensation unit 102 outputs a transmission baseband signal 103 that retains the power level of the transmission baseband signal 101 before distortion compensation, whereby the power of the wireless transmission signal output from the amplifier circuit 104 is output. Can always be set to the expected value.
In the second embodiment, both the LUT control function and the LUT gain adjustment function are realized by the LUT control unit & LUT gain adjustment unit 210. For this reason, it is only necessary to provide one CPU, which has an advantage that the hardware configuration can be easily reduced in size.

(Other embodiments)
In each of the above embodiments, the case where the predistortion processing is performed on the I and Q complex signals having the baseband frequency, that is, the case where the Cartesian negative feedback circuit is used has been described as an example. The present invention can also be applied when performing predistortion processing.

  Further, the LUT control unit and the LUT gain adjustment unit may be configured by hardware. In addition, the configuration of the DPD processing circuit, the distortion detection unit, the LUT control unit, and the LUT gain adjustment unit can be variously modified and implemented without departing from the scope of the present invention.

  In short, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in each embodiment. Furthermore, you may combine suitably the component covering different embodiment.

It is a block diagram which shows the structure of the distortion compensation unit (DPD processing circuit) and the analog processing unit which are the principal parts of the transmission amplifier concerning the 1st Embodiment of this invention. 2 is a flowchart showing a processing procedure and processing contents of an LUT control unit and an LUT gain adjustment unit of the DPD processing circuit shown in FIG. 1. FIG. 6 is a characteristic diagram for explaining processing contents of an LUT control unit and an LUT gain adjustment unit of the DPD processing circuit shown in FIG. 1. It is a block diagram which shows the structure of the distortion compensation unit (DPD processing circuit) and the analog processing unit which are the principal parts of the transmission amplifier concerning the 2nd Embodiment of this invention. 5 is a flowchart showing a processing procedure and processing contents of an LUT control unit & an LUT gain adjustment unit of the DPD processing circuit shown in FIG. 4. It is a block diagram which shows the structure of the transmission amplification apparatus provided with the conventional general distortion compensation function.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100,200 ... Distortion compensation unit (DPD process part), 101 ... Transmission baseband signal (input signal) before being input into a distortion compensation part, 102 ... Distortion compensation part, 103 ... Transmission baseband signal after distortion compensation, DESCRIPTION OF SYMBOLS 104 ... Amplifier circuit, 105 ... Radio transmission signal (output signal) output from amplifier circuit, 106 ... Feedback signal, 107 ... Distortion detection part, 108 ... Input signal power measurement part, 109 ... Signal power measurement part after distortion compensation, DESCRIPTION OF SYMBOLS 110 ... LUT control part, 111 ... LUT gain adjustment part, 112 ... Distortion compensation table (LUT), 210 ... LUT control part & LUT gain adjustment part.

Claims (1)

An amplifier circuit that amplifies and outputs the input transmission signal; and
A distortion compensation table storing compensation data representing distortion compensation characteristics that are inverse to the nonlinear characteristics of the amplifier circuit;
A distortion compensation circuit that compensates the signal characteristics of the transmission signal in accordance with compensation data read from the distortion compensation table, and inputs the transmission signal with the signal characteristics compensated to the amplifier circuit;
First detection means for receiving a part of the transmission signal output from the amplifier circuit as a feedback signal and detecting a distortion amount of the amplifier circuit from the feedback signal;
Second detection means for detecting information representing a signal level difference between a transmission signal before being input to the distortion compensation circuit and a transmission signal after signal characteristics have been compensated by the distortion compensation circuit;
Based on the information indicating the difference between the distortion amount of the amplifier circuit detected by the first detection means and the transmission signal level detected by the second detection means, the distortion amount is reduced and the transmission signal level is reduced. And a control means for controlling compensation data read from the distortion compensation table in order to reduce the difference between the two, an amplifying apparatus having a distortion compensation function.

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