JP2016015612A - Receiver and distortion compensation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a suppression effect on deterioration of communication characteristics.SOLUTION: A receiver comprises: a distortion compensation unit 11 which subjects a signal to distortion compensation and outputs the signal which has been subjected to distortion compensation when receiving the signal from a transmitter 20; a hard determination unit 12 which subjects an output signal of the distortion compensation unit 11 to hard determination and outputs a signal corresponding to the results of the hard determination; an error detection unit 13 which detects an error between the output signal of the distortion compensation unit 11 and an output signal 12 of the hard determination unit; a compensation coefficient recording unit 15 which records the compensation coefficient used by the distortion compensation unit 11 for distortion compensation; and a compensation coefficient calculation unit 14 which calculates a compensation coefficient on the basis of the error detected by the error detection unit 13, and updates the compensation coefficient recorded in the compensation coefficient recording unit 15 to the calculated compensation coefficient. The distortion compensation unit 11 performs distortion compensation using a received signal, the received signals received past the received signal, and the compensation coefficients recorded in the compensation coefficient recording unit 15.

Description

  The present invention relates to a receiver and a distortion compensation method.

A transmitter used for wireless communication generally includes a nonlinear device such as an amplifier. Non-linear devices have a characteristic that the input / output relationship is non-linear, and the output signal of the non-linear device may include non-linear distortion due to this characteristic. When a signal including such distortion is transmitted, it causes deterioration of communication characteristics of wireless communication.
Patent Document 1 (Japanese Patent No. 4019912) discloses a technique for estimating and compensating for nonlinear distortion included in a received signal in a receiver that receives a signal transmitted from a transmitter. According to this technique, it is possible to suppress deterioration of communication characteristics by compensating in a receiver for nonlinear distortion generated in a nonlinear device of a transmitter.

Japanese Patent No. 4019912

In addition to non-linear distortion, distortion caused by the memory device includes distortion due to the memory effect. The memory effect is a phenomenon in which an output signal of a nonlinear device with respect to an input signal at a certain time is affected by past input signals. In the technique disclosed in Patent Document 1, compensation for distortion due to the memory effect is not taken into consideration, and deterioration of communication characteristics may not be suppressed.
An object of the present invention is to provide a receiver and a distortion compensation method that can enhance the effect of suppressing deterioration of communication characteristics.

In order to achieve the above object, the receiver of the present invention provides:
When a signal is received from the transmitter, distortion compensation is performed on the received signal, and a distortion compensation unit that outputs the signal after the distortion compensation;
A hard decision unit that performs a hard decision on the output signal of the distortion compensation unit and outputs a signal according to the result of the hard decision;
An error detection unit for detecting an error between the output signal of the distortion compensation unit and the output signal of the hard decision unit;
A compensation coefficient recording section for recording a compensation coefficient for the distortion compensation section to perform distortion compensation;
A compensation coefficient calculation unit that calculates the compensation coefficient based on the error detected by the error detection unit and updates the compensation coefficient recorded in the compensation coefficient recording unit to the calculated compensation coefficient;
The distortion compensator performs distortion compensation using the received signal, a past received signal received in the past from the received signal, and a compensation coefficient recorded in the compensation coefficient recording unit.

In order to achieve the above object, the distortion compensation method of the present invention provides:
A distortion compensation method in a receiver for receiving a signal transmitted from a transmitter,
When receiving a signal from the transmitter, perform distortion compensation for the received signal,
Make a hard decision on the signal after distortion compensation,
Detecting an error between the signal after the distortion compensation and the signal according to the result of the hard decision;
Record a compensation coefficient for performing the distortion compensation,
Based on the detected error, calculate a compensation coefficient for performing the distortion compensation, update the recorded compensation coefficient to the calculated compensation coefficient,
The distortion compensation is performed based on the received signal, a past received signal received earlier than the received signal, and a recorded compensation coefficient.

  ADVANTAGE OF THE INVENTION According to this invention, the suppression effect of deterioration of a communication characteristic can be improved.

It is a block diagram which shows the principal part structure of the receiver which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the distortion which arises in a nonlinear device. It is a figure for demonstrating a receiving linearizer technique. It is a block diagram which shows the principal part structure of a related receiver. It is a figure which shows the structure of the distortion compensation part shown in FIG. It is a figure which shows the structure of the distortion compensation part shown in FIG. It is a block diagram which shows the principal part structure of the receiver which concerns on the 2nd Embodiment of this invention.

EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated with reference to drawings.
The present invention is mainly mounted on a communication device such as a wireless base station or a fixed wireless transmission device that connects a plurality of wireless base stations via wireless, and receives and receives a signal from a transmitter. The present invention relates to a distortion compensation method in a machine.

(First embodiment)
FIG. 1 is a diagram illustrating a main configuration of a receiver 10 according to the first embodiment of the present invention. In FIG. 1, the configuration of the main part of the transmitter 20 is also shown. First, the configuration of the transmitter 20 will be described.
The transmitter 20 illustrated in FIG. 1 includes a modulation unit 21 and a nonlinear device 22.
The modulation unit 21 performs modulation such as QPSK (Quadrature Phase Shift Keying) and QAM (Quadrature Amplitude Modulation) on the input signal, and outputs the modulated signal to the nonlinear device 22.
The nonlinear device 22 is an amplifier, for example, and performs a predetermined process (for example, amplification) on the output signal of the modulation unit 21 and outputs the result. The output signal of the nonlinear device 22 is transmitted via the antenna of the transmitter 20.

Next, the configuration of the receiver 10 will be described.
The receiver 10 shown in FIG. 1 includes a distortion compensation unit 11, a hard decision unit 12, an error detection unit 13, a compensation coefficient calculation unit 14, and a compensation coefficient recording unit 15.
When a signal wirelessly transmitted from the transmitter 20 is received via the antenna of the receiver 10, the distortion compensation unit 11 performs distortion compensation for compensating for distortion generated in the transmitter 20 included in the received signal. I do. Then, the distortion compensation unit 11 outputs the signal after distortion compensation to the hard decision unit 12 and the error detection unit 13. In the receiver 10, a technique for compensating for distortion generated in the nonlinear device 22 included in the received signal is referred to as a reception linearizer technique.
The hard decision unit 12 performs a hard decision on the output signal of the distortion compensation unit 11 and outputs a signal corresponding to the result of the hard decision to the outside of the receiver 10 (for example, a signal of a communication device in which the receiver 10 is mounted). Output to the processing unit) and the error detection unit 13.
The error detection unit 13 detects an error between the output signal of the distortion compensation unit 11 and the output signal of the hard decision unit 12 and outputs the detection result to the compensation coefficient calculation unit 14.
The compensation coefficient calculation unit 14 calculates a compensation coefficient for the distortion compensation unit 11 to perform distortion compensation based on the detection result of the error detection unit 13, and outputs the calculated distortion compensation coefficient to the compensation coefficient recording unit 15.
The compensation coefficient recording unit 15 records a compensation coefficient for the distortion compensation unit 11 to perform distortion compensation. When the compensation coefficient is output from the compensation coefficient calculation unit 14, the compensation coefficient recorded in the compensation coefficient recording unit 15 is updated to the compensation coefficient output from the compensation coefficient calculation unit 14. The compensation coefficient recorded in the compensation coefficient recording unit 15 is referred to when the distortion compensation unit 11 performs distortion compensation.

Next, distortion generated in the nonlinear device 22 and reception linearizer technology will be described. In the following, as shown in FIG. 2, the input signal of the nonlinear device 22 is x (t) and the output signal is y (t). In this case, when the input signal is represented by a matrix, X = {x (0), x (1),... X (t)}, and when the output signal is represented by a matrix, Y = {y (0), y (1),... y (t)}. When the distortion characteristic of the nonlinear device 22 is A, the output signal Y = A · X.
As described above, the reception linearizer technique is a technique for compensating for distortion occurring in the nonlinear device 22 included in the received signal in the receiver 10. Specifically, as shown in FIG. 3, the reception linearizer (distortion compensation unit) provided in the receiver gives a characteristic B to the received signal, which is caused by the distortion characteristic A of the nonlinear device 22. This technique compensates for distortion and obtains the original signal.
When FIG. 3 is expressed by an equation, Y = B · A · X. From this equation, it can be seen that the distortion generated in the nonlinear device 22 can be compensated by giving the reception signal the inverse characteristic of the distortion characteristic A.

Next, distortion generated in the nonlinear device 22 will be described in more detail.
When only the non-linear distortion caused by the characteristic that the input / output relationship of the non-linear device 22 is non-linear without considering the distortion caused by the memory effect, the distortion characteristic of the non-linear device 22 at time t ₀ is expressed by the following equation: It is represented by (1).

式（１），（２）において、ｋは非線形デバイス２２の非線形歪みを近似（モデル化）する多項式の次数である。式（１），（２）では、非線形デバイス２２の非線形歪みを近似する多項式として、メモリ多項式モデルを採用している。また、式（２）において、ｍは時間的なパラメータである。 On the other hand, when the memory effect is also taken into consideration, the distortion characteristics of the nonlinear device 22 are expressed by the following formula (2).

In equations (1) and (2), k is the degree of a polynomial that approximates (models) the nonlinear distortion of the nonlinear device 22. In equations (1) and (2), a memory polynomial model is adopted as a polynomial that approximates the nonlinear distortion of the nonlinear device 22. In Expression (2), m is a temporal parameter.

式（３）から、ある時刻（例えば、時刻ｔ₀）における非線形デバイス２２の出力信号（ｙ（ｔ₀））は、その時刻よりも過去（時刻ｔ_-1〜時刻ｔ_-M+1）の非線形デバイス２２の入力信号の影響を受けることが分かる。したがって、ある時刻における受信機１０の受信信号は、その時刻よりも過去に受信された受信信号の影響を受けることになる。 Expression (2) is expanded with respect to time (expanded to times t _{0 to} t _N ), and expressed as a matrix, the following expression (3) is obtained.

From the equation (3), the output signal (y (t ₀ )) of the nonlinear device 22 at a certain time (for example, time t ₀ ) is past (time t ₋₁ to time t _{−M + 1} ) than that time. It can be seen that the input signal of the nonlinear device 22 is affected. Therefore, the reception signal of the receiver 10 at a certain time is affected by the reception signal received in the past from that time.

Next, the operation of the receiver 10 will be described.
First, for comparison, an operation of a receiver (related receiver) that does not consider the memory effect will be described. FIG. 4 is a block diagram illustrating a main configuration of the related receiver 30.
The main configuration of the receiver 30 is the same as the main configuration of the receiver 10. Therefore, in FIG. 4, each constituent element of the receiver 30 is given a reference number with “A” after the reference number of the corresponding constituent element of the receiver 10, and redundant description is omitted. .
In the following, as shown in FIG. 4, the input signal of the nonlinear device 22 is x (t) and the output signal is y (t). Further, an input signal to the distortion compensator 11A is y ′ (t), and an output signal of the hard decision unit 12A is x ′ (t). It is also assumed that y ′ (t) = y (t−d) and x ′ (t) = x (t−d) hold. d is the signal delay from the transmitter to the receiver. Further, the distortion characteristic of the nonlinear device 22 (distortion characteristic of the nonlinear distortion) is a _k, and the compensation coefficient for the distortion compensation unit 11A to perform distortion compensation is c _k .

誤差検出部１３Ａは、硬判定部１２Ａの出力信号（ｘ’（ｔ））と歪み補償部１１Ａの出力信号（Ｃ_k＊ｙ’（ｔ））との誤差を検出する。
補償係数算出部１４Ａは、誤差検出部１３Ａの検出結果に基づき、以下の式（５）を満たす補償係数ｃ_kを、例えば、ＬＭＳ（Ｌｅａｓｔ Ｓｑｕａｒｅｓ Ｍｅｔｈｏｄ）を用いて算出する。

補償係数算出部１４Ａが算出した補償係数ｃ_kを用いて歪み補償を行なうことで、非線形デバイス２２の歪み特性の逆特性を受信信号ｙ’（ｔ）に与えることができる。その結果、受信信号ｙ’（ｔ）に含まれる非線形歪みを補償することができる。 When only the nonlinear distortion of the nonlinear device 22 is considered, the output signal y (t) of the nonlinear device 22 is expressed by the following equation (4).

The error detector 13A detects an error between the output signal (x ′ (t)) of the hard decision unit 12A and the output signal (C _k * y ′ (t)) of the distortion compensator 11A.
The compensation coefficient calculation unit 14A calculates a compensation coefficient _ck satisfying the following equation (5) based on the detection result of the error detection unit 13A using, for example, LMS (Least Squares Method).

By performing distortion compensation using the compensation coefficient _ck calculated by the compensation coefficient calculation unit 14A, the inverse characteristic of the distortion characteristic of the nonlinear device 22 can be given to the received signal y ′ (t). As a result, nonlinear distortion included in the received signal y ′ (t) can be compensated.

FIG. 5 is a diagram illustrating a configuration of the distortion compensator 11A. In FIG. 5, it is assumed that K = 4. In this case, the compensation coefficient calculation unit 14A calculates four compensation coefficients c ₀ , c ₁ , c ₂ , and c ₃ . FIG. 5 shows a state at time t ₀ .
The distortion compensation unit 11A illustrated in FIG. 5 includes an absolute value circuit (ABS) 201, multipliers 202 to 208, and an adder 209.
Received signal y ′ (t) is input to ABS 201 and multipliers 202 and 203. Further, compensation coefficients C ₀ , C ₁ , C ₂ , and C ₃ are input to the multipliers 202, 204, 206, and 208, respectively.
The ABS 201 obtains the absolute value of the received signal y ′ (t ₀ ) and outputs the obtained absolute value to the multipliers 203, 205, and 207.
Multiplier 202 multiplies reception signal y ′ (t ₀ ) by compensation coefficient C ₀ and outputs the multiplication result (C ₀ y ′ (t ₀ )) to adder 209.
The multiplier 203 multiplies the received signal y ′ (t ₀ ) by the output (| y ′ (t ₀ ) |) of the ABS 201 and multiplies the result (y ′ (t ₀ ) | y ′ (t ₀ ) |). Is output to the multipliers 204 and 205.
The multiplier 204 multiplies the output (y ′ (t ₀ ) | y ′ (t ₀ ) |) of the multiplier 203 by the compensation coefficient C _1, and the multiplication result (C ₁ y ′ (t ₀ ) | y ′). (T ₀ ) |) is output to the adder 209.
The multiplier 205 multiplies the output of the ABS 201 (| y ′ (t ₀ ) |) and the output of the multiplier 203 (y ′ (t ₀ ) | y ′ (t ₀ ) |), and the multiplication result (y ′ (T ₀ ) | y ′ (t ₀ ) | ² ) is output to the multipliers 206 and 207.
The multiplier 206 multiplies the output (y ′ (t ₀ ) | y ′ (t ₀ ) | ² ) of the multiplier 205 by the compensation coefficient C _2, and the multiplication result (C ₂ y ′ (t ₀ ) | y '(T ₀ ) | ² ) is output to the adder 209.
The multiplier 207 multiplies the output of the ABS 201 (| y ′ (t ₀ ) |) and the output of the multiplier 205 (y ′ (t ₀ ) | y ′ (t ₀ ) | ² ), and the multiplication result (y '(T ₀ ) | y' (t ₀ ) | ³ ) is output to the multiplier 208.
The multiplier 208 multiplies the output (y ′ (t ₀ ) | y ′ (t ₀ ) | ³ ) of the multiplier 207 by the compensation coefficient C _3, and the multiplication result (C ₃ y ′ (t ₀ ) | y '(T ₀ ) | ³ ) is output to the adder 209.
The adder 209 includes an output from the multiplier 202 (c ₀ y ′ (t ₀ )), an output from the multiplier 204 (c ₁ y (t ₀ ) ′ | y ′ (t ₀ ) |), and a multiplier 206. Output (c ₂ y ′ (t ₀ ) | y ′ (t ₀ ) | ² ) and the output of multiplier 208 (c ₃ y ′ (t ₀ ) | y ′ (t ₀ ) | ³ ) (Σc _k * y ′ (t ₀ )). Then, the adder 209 outputs the addition result to the hard decision unit 12A.

  As described above, due to the memory effect, the output signal of the non-linear device 22 at a certain time is affected by the input signal of the non-linear device 22 past that time. In the receiver 30, distortion due to the memory effect cannot be compensated because distortion compensation considering the past input to the nonlinear device 22 is not performed.

誤差検出部１３は、硬判定部１２の出力信号（ｘ’（ｔ））と歪み補償部１１の出力信号（Ｃ_mk＊ｙ’（ｔ））との誤差を検出する。 Next, the operation of the receiver 10 will be described. In the following, as shown in FIG. 1, it is assumed that the distortion characteristic of the nonlinear device 22 is a _mk including distortion caused by the memory effect. Further, a compensation coefficient for the distortion compensation unit 11 to perform distortion compensation is assumed to be _cmk .
In consideration of distortion caused by the memory effect, the output signal y ′ (t) of the nonlinear device 22 is expressed by the following equation (6).

The error detector 13 detects an error between the output signal (x ′ (t)) of the hard decision unit 12 and the output signal (C _mk * y ′ (t)) of the distortion compensator 11.

Based on the detection result of the error detection unit 13, the compensation coefficient calculation unit 14 makes the compensation coefficient so that the inverse characteristic of the distortion characteristic a _mk of the nonlinear device 22 is given to the received signal y ′ (t) by the distortion compensation unit 11. c _mk is calculated, and the calculated compensation coefficient c _mk is recorded in the compensation coefficient recording unit 15. The compensation coefficient calculation unit 14 calculates the compensation coefficient C _mk using, for example, LMS. The distortion compensation unit 11 performs distortion compensation using the compensation coefficient C _mk recorded in the compensation coefficient recording unit 15.

FIG. 6 is a diagram illustrating a configuration of the distortion compensation unit 11. In FIG. 6, it is assumed that M = K = 4. In this case, the compensation coefficient calculation unit 14 calculates compensation coefficients C _{00 to} C ₀₃ , C _{10 to} C ₁₃ , C _{20 to} C ₂₃ , and C _{30 to} C ₃₃ . FIG. 6 shows a state at time t ₀ .
The distortion compensation unit 11 illustrated in FIG. 6 includes a plurality of unit distortion compensation circuits 110 (110-0 to 110-3), a plurality of delay devices 120 (120-1 to 120-3), and an adder 130. .
The unit distortion compensation circuit 110-0 and the unit distortion compensation circuit 110-1 are connected via a delay device 120-1. The unit distortion compensation circuit 110-1 and the unit distortion compensation circuit 110-2 are connected via a delay device 120-2. The unit distortion compensation circuit 110-2 and the unit distortion compensation circuit 110-3 are connected via a delay device 120-3.

The unit distortion compensation circuit 110-0 includes an ABS 111, multipliers 112 to 118, and an adder 119. The received signal y ′ (t ₀ ) is input to the ABS 111, the multiplier 112, and the delay unit 120-1 of the unit distortion compensation circuit 110-0.
The ABS 111, the multipliers 112 to 118, and the adder 119 correspond to the ABS 201, the multipliers 202 to 208, and the adder 209 of the distortion compensation unit 11A shown in FIG. Therefore, in FIG. 6, the description of the connection relationship (input / output relationship) of the ABS 111, the multipliers 112 to 118, and the adder 119 is omitted.
However, in the unit distortion compensation circuit 110-0, the compensation coefficients C ₀₀ , C ₀₁ , C ₀₂ , and C ₀₃ are input to the multipliers 112, 114, 116, and 118, respectively. The compensation coefficients C ₀₀ , C ₀₁ , C ₀₂ and C ₀₃ are compensation coefficients calculated by the compensation coefficient calculation unit 14 corresponding to the received signal y ′ (t ₀ ).
The output of the adder 119 of the unit distortion compensation circuit 110-0 is as follows.

The delay device 120-1 delays the received signal y ′ (t ₀ ) by a time d corresponding to the signal delay from the transmitter to the receiver, and outputs the delayed signal to the unit distortion compensation circuit 110-1 and the delay device 120-2. To do. As described above, since the state at time t ₀ is shown in FIG. 6, the unit distortion compensation circuit 110-1 and the delay unit 120-2 have a time t ₋ past the time t ₀ by the time d than time t _0. received signal y in ₁ '(t _-1) is input.
The configuration of the unit distortion compensation circuit 110-1 is the same as the configuration of the unit distortion compensation circuit 110-0. However, in the unit distortion compensation circuit 110-1, each of the multipliers 112, 114, 116, and 118 has a compensation coefficient C ₁₀ corresponding to the received signal y ′ (t ₋₁ ) calculated by the compensation coefficient calculation unit 14. , C ₁₁ , C ₁₂ , C ₁₃ are input. Therefore, the output of the adder 119 of the unit distortion compensation circuit 110-1 is as follows.

Delay device 120-2 delays the output signal of delay device 120-1 by time d and outputs the delayed signal to unit distortion compensation circuit 110-2 and delay device 120-3. As described above, since the state at time t ₀ is shown in FIG. 6, the unit distortion compensation circuit 110-2 and the delay device 120-3 have the time t past the time t ₋₁ than the time t _−1. the received signal y in _-2 '(t _-2) is input.
The configuration of the unit distortion compensation circuit 110-2 is the same as the configuration of the unit distortion compensation circuit 110-0. However, in the unit distortion compensation circuit 110-2, each of the multipliers 112, 114, 116, and 118 has a compensation coefficient C ₂₀ corresponding to the received signal y ′ (t ₋₂ ) calculated by the compensation coefficient calculation unit 14. , C ₂₁ , C ₂₂ , C ₂₃ are input. Therefore, the output of the adder 119 of the unit distortion compensation circuit 110-2 is as follows.

The delay device 120-3 delays the output signal of the delay device 120-2 by time d and outputs the delayed signal to the unit distortion compensation circuit 110-3. As described above, since the state at time t ₀ is shown in FIG. 6, the unit distortion compensation circuit 110-3 receives the received signal y at time t _{−3 that} is past time t ₋₃ from time t _−2. '(T _-3 ) is input.
Unit distortion compensation circuit 110-3, the output signal (reception signal y delayer 120-2 '(t _-3)) and the compensation coefficient calculation unit 14 has calculated, the received signal y' corresponding to (t _-3) Compensation coefficient The compensation coefficients c _{30 to} C ₃₃ are multiplied, and the multiplication result is output to the adder 130.
The configuration of the unit distortion compensation circuit 110-3 is the same as that of the unit distortion compensation circuit 110-0. However, in the unit distortion compensation circuit 110-3, each of the multipliers 112, 114, 116, and 118 has a compensation coefficient C ₃₀ corresponding to the received signal y ′ (t ₋₃ ) calculated by the compensation coefficient calculation unit 14. , C ₃₁ , C ₃₂ , C ₃₃ are input. Therefore, the output of the adder 119 of the unit distortion compensation circuit 110-3 is as follows.

The adder 130 adds the outputs of the unit distortion compensation circuits 110-0 to 110-3 and outputs the addition result to the hard decision unit 12. The output of the adder 130 is expressed by the following equation (7).

  As can be seen from equation (7), the receiver 10 performs distortion compensation using not only a received signal at a certain time but also a received signal received in the past from the received signal. For this reason, distortion caused by the memory effect can also be compensated.

The compensation coefficient calculation unit 14 may change the values of M and K in accordance with communication characteristics required for communication between the transmitter 20 and the receiver 10 and the state of the communication path. For example, the compensation coefficient calculation unit 14 sets M and K to large values when high communication characteristics are required for communication between the transmitter 20 and the receiver 10 or when the communication path is in a poor state. Also good. In addition, the compensation coefficient calculation unit 14 may set M and K to small values when a modulation method that is not easily affected by the state deterioration of the communication channel such as QPSK is selected. Further, the compensation coefficient calculation unit 14 may set M and K to small values when the signal deterioration due to nonlinear distortion is small and the compensation coefficient value is small.
By changing the value of M, the reception period of the past received signal used for distortion compensation changes. Therefore, if the value of M is reduced, the number of unit distortion compensation circuits 110 to be operated is reduced, so that the power consumption of the receiver 10 can be reduced. Also, by reducing the values of M and K, the number of compensation coefficients calculated by the compensation coefficient calculation unit 14 is reduced, so that the processing load is reduced and the power consumption can be reduced. Therefore, adaptively changing the values of M and K can reduce the power consumption of the receiver 10 while preventing the deterioration of the communication characteristics.

As described above, the receiver 10 of the present embodiment performs distortion compensation on the received signal from the transmitter 20 and outputs a distortion-compensated signal, and the output signal of the distortion compensation unit 11. A hard decision unit 12 that performs a hard decision and outputs a signal corresponding to the result of the hard decision. The receiver 10 also includes a compensation coefficient recording unit 15 that records the compensation coefficient, an error detection unit 13 that detects an error between the output signal of the distortion compensation unit 11 and the output signal of the hard decision unit 12, and the error detection unit 13 A compensation coefficient calculation unit 14 that calculates a compensation coefficient based on the detected error and updates the compensation coefficient recorded in the compensation coefficient recording unit 15 to the calculated compensation coefficient.
The distortion compensator 11 performs distortion compensation using the received signal, a past received signal received earlier than the received signal, and the compensation coefficient recorded in the compensation coefficient recording unit 15.

  Distortion compensation that takes into account not only the current received signal but also past received signals can compensate not only for nonlinear distortion but also for distortion caused by the memory effect. Can be increased.

すなわち、ナイキストフィルタ２３は、変調部２１の出力信号ｘ（ｔ）の帯域を制限して、非線形デバイス２２に出力する。
送信機２０がナイキストフィルタ２３を有する場合、ナイキストフィルタ２３と同等の特性を有するナイキストフィルタ１６を設け、硬判定部１２の出力の帯域を制限して誤差検出部１３に入力することで、精度の高い歪み補償が可能となる。 (Second Embodiment)
FIG. 7 is a block diagram showing a configuration of a receiver 10A according to the second embodiment of the present invention.
The receiver 10 </ b> A of the present embodiment is different from the receiver 10 of the first embodiment in that a Nyquist filter 16 is added between the hard decision unit 12 and the error detection unit 13.
The Nyquist filter 16 outputs a signal z ′ (t) obtained by limiting the band of the output signal x ′ (t) of the hard decision unit 12 to the error detection unit 13.
As illustrated in FIG. 7, the transmitter 20 may be provided with a Nyquist filter 23 between the modulation unit 21 and the nonlinear device 22. In this case, if the input signal of the nonlinear device 22 (the output signal of the Nyquist filter 23) is z (t), the output signal y (t) of the nonlinear device 22 is as follows.

That is, the Nyquist filter 23 limits the band of the output signal x (t) of the modulation unit 21 and outputs it to the nonlinear device 22.
When the transmitter 20 includes the Nyquist filter 23, the Nyquist filter 16 having the same characteristics as the Nyquist filter 23 is provided, and the bandwidth of the output of the hard decision unit 12 is limited and input to the error detection unit 13, thereby improving accuracy. High distortion compensation is possible.

As described above, the receiver 10 </ b> A of the present embodiment includes the Nyquist filter 16 between the hard decision unit 12 and the error detection unit 13.
Therefore, the bandwidth of the input to the error detection unit 13 is limited in accordance with the bandwidth limitation of the input signal to the nonlinear device 22 in the transmitter 20, and more accurate compensation is possible.

DESCRIPTION OF SYMBOLS 10,10A Receiver 11 Distortion compensation part 12 Hard decision part 13 Error detection part 14 Compensation coefficient calculation part 15 Compensation coefficient recording part 16,23 Nyquist filter 110 Unit distortion compensation circuit 111 Absolute value circuit 112-118 Multiplier 119,130 Addition Unit 120 delay unit 20 transmitter 21 modulation unit 22 nonlinear device

Claims (10)

When a signal is received from the transmitter, distortion compensation is performed on the received signal, and a distortion compensation unit that outputs the signal after the distortion compensation;
A hard decision unit that performs a hard decision on the output signal of the distortion compensation unit and outputs a signal according to the result of the hard decision;
An error detection unit for detecting an error between the output signal of the distortion compensation unit and the output signal of the hard decision unit;
A compensation coefficient recording section for recording a compensation coefficient for the distortion compensation section to perform distortion compensation;
A compensation coefficient calculation unit that calculates the compensation coefficient based on the error detected by the error detection unit and updates the compensation coefficient recorded in the compensation coefficient recording unit to the calculated compensation coefficient;
The distortion compensator performs distortion compensation using the received signal, a past received signal received in the past from the received signal, and a compensation coefficient recorded in the compensation coefficient recording unit. Machine. The receiver of claim 1, wherein
The compensation coefficient calculation unit calculates the compensation coefficient using a polynomial that models distortion generated in a nonlinear device included in the transmitter, and obtains the degree of the polynomial in communication between the transmitter and the receiver. The receiver is set based on a communication characteristic to be set or a state of a communication path between the transmitter and the receiver. The receiver according to claim 1 or 2,
The compensation coefficient calculation unit determines a reception period of the past received signal used for the distortion compensation, a communication characteristic required for communication between the transmitter and the receiver, or communication between the transmitter and the receiver. A receiver set based on a state of a road. The receiver according to any one of claims 1 to 3,
The distortion compensator is
A plurality of unit distortion compensation circuits for multiplying the input signal by the compensation coefficient calculated by the compensation coefficient calculator and outputting a multiplication result;
An adder for adding the outputs of the plurality of unit distortion compensation circuits and outputting the signal after the addition as a signal after the distortion compensation;
Of the plurality of unit distortion compensation circuits, the reception signal is input to one unit distortion compensation circuit, and the reception signal is input to each of the other unit distortion compensation circuits with different delay times.
The receiver, wherein the compensation coefficient calculation unit calculates a compensation coefficient corresponding to a signal input to each of the plurality of unit distortion compensation circuits. The receiver according to any one of claims 1 to 4,
A Nyquist filter is provided between the hard decision unit and the error detection unit,
The receiver, wherein the Nyquist filter limits a band of an output signal of the hard decision unit, and outputs the band-limited signal to the error detection unit. A distortion compensation method in a receiver for receiving a signal transmitted from a transmitter,
When receiving a signal from the transmitter, perform distortion compensation for the received signal,
Make a hard decision on the signal after distortion compensation,
Detecting an error between the signal after the distortion compensation and the signal according to the result of the hard decision;
Record a compensation coefficient for performing the distortion compensation,
Based on the detected error, calculate a compensation coefficient for performing the distortion compensation, update the recorded compensation coefficient to the calculated compensation coefficient,
A distortion compensation method, wherein the distortion compensation is performed based on the received signal, a past received signal received earlier than the received signal, and a recorded compensation coefficient. The distortion compensation method according to claim 6, wherein
The compensation coefficient is calculated using a polynomial that models distortion generated in a nonlinear device included in the transmitter, and the degree of the polynomial is determined as communication characteristics required for communication between the transmitter and the receiver or the transmitter. A distortion compensation method is set based on a state of a communication path between the receiver and the receiver. The distortion compensation method according to claim 6 or 7,
The reception period of the past received signal used for the distortion compensation is set based on communication characteristics required for communication between the transmitter and the receiver or a state of a communication path between the transmitter and the receiver. And a distortion compensation method. The distortion compensation method according to any one of claims 6 to 8,
The receiver includes
A plurality of unit distortion compensation circuits for multiplying the input signal by the compensation coefficient calculated by the compensation coefficient calculator and outputting a multiplication result;
An adder that adds the outputs of the plurality of unit distortion compensation circuits and outputs the signal after the addition as a signal after the distortion compensation;
Of the plurality of unit distortion compensation circuits, the reception signal is input to one unit distortion compensation circuit, and the reception signal is input to each of the other unit distortion compensation circuits with different delay times.
A distortion compensation method for calculating a compensation coefficient corresponding to a signal input to each of the plurality of unit distortion compensation circuits. The distortion compensation method according to any one of claims 6 to 9,
A distortion compensation method, wherein a band of a signal corresponding to the result of the hard decision is limited by a Nyquist filter, and an error between the signal after the band limitation and the signal after the distortion compensation is detected.

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