JP2010130666A - Predistorter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a predistorter capable of increasing the tracking speed and convergence speed and also capable of obtaining sufficient distortion compensation accuracy. <P>SOLUTION: This predistorter has a distortion compensation circuit 11 and a control unit 13. The distortion compensation circuit 11 outputs a predistortion compensation signal generated by substituting an input signal into a distortion compensation polynominal equation to a compensated circuit 401. The control unit 13 receives an input signal X and an output signal Y of the compensated circuit 401 as input and updates the coefficient value of the distortion compensation polynominal equation based on a differential between the signal generated by substituting the input signal A into the distortion compensation polynominal equation and the signal generated by substituting the output signal Y into the distortion compensation polynominal equation and a variable update coefficient. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a predistorter that compensates for distortion due to a memory effect of a compensated circuit such as a signal amplifier.

  A conventional predistorter includes a lookup table for generating a distortion predistortion signal, and updates a distortion compensation value in the lookup table for each address (see, for example, Patent Document 1). .) Since the predistorter of Patent Document 1 uses adaptive signal processing to update the distortion compensation value of the lookup table for each address, it is proportional to the number of addresses (the number of values obtained by quantizing the amplitude or power of the input signal). As a result, the amount of memory and the amount of calculation are greatly increased.

For this reason, in order to reduce the amount of calculation of the distortion compensation value by adaptive signal processing and the amount of memory, a pre-displacement that calculates the distortion compensation value by reducing the number of addresses when updating and then interpolates the distortion compensation value between addresses. Tota is known (see, for example, Patent Document 2). Also, the distortion compensation value of the lookup table calculated from a set of a plurality of input signals and output signals is averaged for each address corresponding to the intensity (power or amplitude) of the input signal, and the averaged lookup table Estimate the distortion compensation polynomial from the relationship between the address and distortion compensation value, estimate the distortion compensation value again from the distortion compensation polynomial, create a lookup table that interpolates the distortion compensation value between addresses with high accuracy, and A predistorter that quotes the distortion compensation value from the intensity is also known (see, for example, Patent Document 3).
Japanese Patent No. 3560398 JP 2002-223171 A JP 2006-093947 A

  In the conventional predistorter, the update coefficient μ used when updating the coefficient value of the distortion compensation polynomial is constant (fixed value). Therefore, if the update coefficient μ is increased, the follow-up speed and convergence speed are fast, but the effect of noise is directly reflected in the error, so the accuracy of distortion compensation cannot be increased. Conversely, if the update coefficient μ is decreased, distortion compensation There was a problem that convergence could be slow although accuracy could be increased.

  Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a predistorter that can increase the follow-up speed and the convergence speed, and can obtain sufficient distortion compensation accuracy. And

  In order to achieve the above object, in the predistorter according to the present invention, the update coefficient μ used when updating the coefficient value of the distortion compensation polynomial is not a fixed value but a variable value.

  Specifically, the predistorter according to the present invention includes a distortion compensation circuit that outputs a predistortion compensation signal generated by substituting an input signal into a distortion compensation polynomial to the compensation circuit, and the input signal and the compensation circuit. The distortion signal is input based on a difference between a signal generated by substituting the input signal into a distortion compensation polynomial and a signal generated by substituting the output signal into the distortion compensation polynomial and a variable update coefficient. A control unit that updates the coefficient value of the compensation polynomial.

  Another predistorter according to the present invention includes a distortion compensation circuit that outputs a predistortion compensation signal generated by substituting an input signal into a distortion compensation polynomial to the compensated circuit, the predistortion compensation signal, and the compensated compensation. An output signal of the circuit is input, and a coefficient value of the distortion compensation polynomial is updated based on a difference between the predistortion compensation signal and a signal generated by substituting the output signal into the distortion compensation polynomial and a variable update coefficient. A control unit.

  The predistorter according to the present invention can increase the follow-up speed and the convergence speed by increasing the update coefficient μ, and can obtain sufficient distortion compensation accuracy by decreasing the update coefficient μ.

  The control unit of the predistorter according to the present invention preferably determines the update coefficient to be used when updating the coefficient of the distortion compensation polynomial based on the number of times the distortion compensation circuit has updated the distortion compensation value. . If the value of the update coefficient is increased at the start of the update, and the value of the update coefficient is decreased as the update proceeds, it is possible to perform control that increases the convergence speed and increases the accuracy of distortion compensation after convergence.

  The control unit of the predistorter according to the present invention determines the update coefficient to be used when updating the coefficient of the distortion compensation polynomial based on a difference between the input signal and the output signal of the compensated circuit. Also good. When the error between the input signal and the output signal is large, the update coefficient is increased to increase the tracking speed and the convergence speed. When the error is small, the update coefficient is decreased to increase the accuracy of distortion compensation. Is possible.

  The present invention can provide a predistorter that can increase the follow-up speed and the convergence speed and can obtain sufficient distortion compensation accuracy.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment. In the present specification and drawings, the same reference numerals denote the same components. In addition, the description with the reference numerals without the branch numbers is the description common to all the components and signals with the reference numerals assigned with the branch numbers.

  FIG. 1 is a block diagram illustrating the configuration of the predistorter 301 of this embodiment. The predistorter 301 outputs a predistortion compensation signal A generated by using a distortion compensation polynomial to the input signal X to the compensated circuit 401, the input signal X, and the output signal of the compensated circuit 401. Y is input, and the relationship between the distortion compensation polynomial based on the difference between the signal generated by substituting the input signal A for the distortion compensation polynomial and the signal generated by substituting the output signal Y for the distortion compensation polynomial and the variable update coefficient. And a control unit 13 for updating the numerical value.

  FIG. 2 is a block diagram illustrating the configuration of the predistorter 302 of this embodiment. The predistorter 302 outputs a predistortion compensation signal A generated from the input signal X using a distortion compensation polynomial to the compensated circuit 401, and the predistortion signal A and the compensated circuit 401. The control unit 13 that receives the output signal Y and updates the coefficient value of the distortion compensation polynomial based on the difference between the predistortion signal A and the signal generated by substituting the output signal Y into the distortion compensation polynomial and the variable update coefficient. And comprising.

  For example, the compensated circuit 401 is an amplifier. In the following description, the compensated circuit 401 is described as an amplifier.

  FIG. 3 is a block diagram for explaining the distortion compensation circuit 11 of the predistorter 301 and the predistorter 302. The distortion compensation circuit 11 calculates a predistortion compensation signal A using the input signal X. Since the predistortion compensation signal A is added with the inverse distortion characteristic (distortion compensation characteristic) of the distortion characteristic of the compensated circuit 401, the distortion of the output signal Y of the compensated circuit 401 can be reduced.

  The control unit 13 has a difference between a signal generated by substituting the input signal X into a distortion compensation polynomial (not shown in FIG. 3) or a signal generated by substituting the output signal Y into the distortion compensation polynomial and the predistortion compensation signal A is 0. The coefficient value of the distortion compensation polynomial is updated so as to approach. Further, the control unit 13 avoids falling into an uncontrollable state by multiplying an update coefficient that is greater than 0 and less than or equal to 1 when the distortion compensation value is updated. For example, the control unit 13 determines an update coefficient used when updating the coefficient value of the distortion compensation polynomial based on the number of times the coefficient value of the distortion compensation polynomial used in the distortion compensation circuit 11 is updated. Further, the control unit 13 may determine an update coefficient used when updating the coefficient value of the distortion compensation polynomial based on the difference between the input signal X and the output signal Y of the compensated circuit 401.

とおく。ここで、ｊは要素増幅器５１３の番号であり、Ｊは要素増幅器５１３の個数である。また、dは入力信号の正規化先行時間、または正規化遅延時間を表し、Ｄ１_ｊはｊ番目の要素増幅器の最大正規化先行時間、Ｄ２_ｊはｊ番目の要素増幅器の最大正規化遅延時間、ｋは次数であり、Ｋ_ｊはｊ番目の要素増幅器の歪成分の最大次数を表す。 (Description of calculation of update amount)
An amplifier composed of a plurality of amplifiers can be modeled as shown in FIG. A discrete time signal obtained by sampling the input signal X with a period T _s is represented by x (nT _s ), and a discrete time signal obtained by sampling the output signal Y with a period T _s is represented by y (nT _s ). X (n), y (n). Also, x (n) and y (n) are complex signals having a real component and an imaginary component, and multiplication and addition for x (n) and y (n) indicate complex multiplication and complex addition, respectively. . That is, in FIG. 1 and FIG. 2 described above, there are a quadrature modulator, a D / A converter, and an upconverter (not shown) between the distortion compensation circuit 11 and the compensated circuit 401. There are a down converter, an A / D converter, and a quadrature demodulator (not shown) between the control units. At this time, each of the distortion characteristic polynomials representing the distortion characteristics of the element amplifier 513 constituting the amplifier is

far. Here, j is the number of the element amplifier 513, and J is the number of the element amplifiers 513. Also, d represents the normalization lead time of the input signal, or the normalization delay time, D1 _j is the maximum normalization lead time of the _jth element amplifier, D2 _j is the maximum normalization delay time of the jth element amplifier, k is the order, and K _j represents the maximum order of the distortion component of the j-th element amplifier.

とおく。ここで、ｒは入力信号の正規化先行時間、または正規化遅延時間を表し、Ｒ１_ｊはｊ番目の要素増幅器に対する合成する比率において関係する入力信号の最大正規化先行時間、Ｒ２_ｊはｊ番目の要素増幅器に対する合成する比率において関係する入力信号の最大正規化遅延時間、ｌは次数であり、Ｌ_ｊはｊ番目の要素増幅器に対する合成する比率において関係する入力信号の最大次数から１次高い次数を表す。このとき、増幅器の出力は

Further, the ratio of combining the element amplifiers 513 is a function of the amplitude value of the input signal X (combining polynomial).

far. Here, r represents the normalization leading time of the input signal, or the normalization delay time, R1 _j is the maximum normalization leading time of the input signal related in the combining ratio with respect to the jth element amplifier, and R2 _j is the jth The maximum normalized delay time of the input signal related in the combining ratio with respect to the element amplifier of L, l is the order, and L _j is the first order higher than the maximum order of the input signal related in the ratio of combining with the j-th element amplifier. Represents. At this time, the output of the amplifier is

である。ここで、ｍａｘ（ｃ_１，ｃ_２，…，ｃ_Ｊ）はｃ_１，ｃ_２，…，ｃ_Ｊの最大値を表す。 Here, Formula 3 is arranged. First, the same terms for different amplifiers (different j)

It is. _{Here, max (c 1, c 2} , ..., c J) are _{c 1, c 2, ...,} representing the maximum value of _{c J.}

である。 Next, if the term of r = d of Formula 4 is put together,

It is.

Equation 5 is

Furthermore,

That is, in order to estimate the distortion characteristics of an amplifier that can be modeled as shown in FIG. 4, complex coefficients h ′ _{d, k} , coefficients h ′ _{r, d, l} , and coefficients h ′ _{r, d, l, k} are calculated. Just do it. In order to calculate the coefficient h ′ _{d, k} , the coefficient h ′ _{r, d, l} , and the coefficient h ′ _{r, d, l, k} , the input signal X and the output signal Y are applied to the model of Equation 7 and the minimum two Multiplication may be used.

となり、線形であるのが理想的である。但し、Ｇは増幅装置の利得を表す実数定数である。ここでは、以降の議論を簡単にする目的で、Ｇ＝１とおくこととする。 (Distortion compensation method)
Next, a distortion compensation method for the amplification device based on the model of FIG. 4 will be described. The relationship between the input and output signals of the entire amplifier is

Ideally, it should be linear. Here, G is a real constant representing the gain of the amplifier. Here, G = 1 is set for the purpose of simplifying the following discussion.

である。 However, in an actual amplifying apparatus, when the amplitude (or power) of the input signal increases, the relationship between the input and output signals is not linear but nonlinear as expressed by Equation 3 or Equation 7. On the other hand, when the relationship between the input signal and the output signal is ideal in Equation 3 or Equation 7, the relationship y (n) = x (n) is established. Therefore, in order to compensate the distortion of the amplifier circuit based on the model of FIG. 4, the distortion compensation is performed by exchanging the input signal X and the output signal Y in Equation 3 or Equation 7, which is a distortion characteristic polynomial expressing the model of FIG. Polynomial

It is.

Similar to the arrangement from Equation 3 to Equation 7,

The complex coefficients w ′ _{d, k} , w ′ _{r, d, l} , and w ′ _{r, d, l, k} of Equation 10 are estimated using the least square method, and the input signal X is compensated according to the distortion compensation polynomial. That's fine. In calculating the complex coefficients w ′ _{d, k} , w ′ _{r, d, l} and w ′ _{r, d, l, k} by the least square method, the complex coefficients w ′ _{d, k} , w ′ _{r, d, l,} and w _{'r, d, l,} than the total number of _k by sampling the many input signals X and output signal Y x (n) and using a set of y (n).

That is, for the purpose of linearizing the input / output relationship of the amplifying apparatus using the coefficient of Equation 10 obtained using the least square method, the nonlinear distortion characteristic (distortion value) of the amplifying apparatus provided in the preceding stage of the amplifying apparatus. In a predistorter 301 or 302 that generates a reverse distortion characteristic (distortion compensation value) for the input signal X, a predistortion compensation signal A in which a distortion compensation value is given in advance to the input signal X is generated and input to the amplifying apparatus. At this time, in order to obtain the predistortion compensation signal A in which the output signal Y of the amplifier is y (n) = x (n), the predistorter 301 or 302 is a distortion compensation polynomial expressed by Equation 11. A distortion compensation value is given in advance to the input signal X to generate a predistortion compensation signal A and input it to the amplifying apparatus.

A predistortion compensation signal A that gives an inverse distortion characteristic (distortion compensation characteristic) that compensates for the non-linear distortion given by the mathematical expression 3 or 7, which is a distortion characteristic polynomial expressing the model of FIG. In order to obtain n), a coefficient w ′ _{j, r, d, l, k} that satisfies the relationship of Expression 9 or Expression 10 in which x (n) and y (n) are replaced in Expression 3 or 7 or coefficient What is necessary is to obtain w ′ _{d, k} , w ′ _{r, d, l} , and w ′ _{r, d, l, k} .

とおく。ここで、Ｔは行列の転置を表す。 (Calculation method of distortion compensation polynomial coefficients)
Here, a method for obtaining the coefficient of the distortion compensation polynomial using Expression 10 will be described. However, here, for simplicity of expression, Da = 0, R1 = 0, and D1 = 0. A vector of coefficients in which complex coefficients w ′ _{d, k} , w ′ _{r, d, l} , and w ′ _{r, d, l, k} are all arranged

far. Here, T represents transposition of the matrix.

但し、

歪補償多項式の係数を推定する際に使用する異なるｎに対する数式１０の個数はＮ（Ｎ≧Ｑ＋１）であり、数式１０をＮ個まとめると数式１３は数式１５の連立方程式となる。

Next, a method for obtaining w ₀ , w ₁ ,..., W _Q will be described. In order to obtain the coefficients w ₀ , w ₁ ,..., W _Q of the distortion compensation polynomial in Expression 12, Q + 1 or more Expressions 10 in different n are required. Here, when Expression 10 is expressed as a matrix, Expression 13 is obtained.

However,

The number of Equations 10 for different n used to estimate the coefficient of the distortion compensation polynomial is N (N ≧ Q + 1). When N of Equations 10 are combined, Equation 13 becomes the simultaneous equations of Equation 15.

但し、Ｈは行列の複素共役転置を表す。このようにして得られた係数ｗ_０，ｗ_１，・・・，ｗ_Ｑをａ（ｎ）に適用し、ｘ（ｎ）に応じた歪補償値を算出すれば歪補償ができる。 The coefficients w ₀ , w ₁ ,..., W _Q are obtained by solving the simultaneous equations of Expression 15 or Expression 17. In order to solve the simultaneous equations of Formula 15 or Formula 17, the sweep-out method may be used, or Formula 18 may be used by using the least square method.

Where H represents the complex conjugate transpose of the matrix. Distortion compensation can be performed by applying the coefficients w ₀ , w ₁ ,..., W _Q thus obtained to a (n) and calculating a distortion compensation value corresponding to x (n).

である。 The distortion compensation circuit 11 receives the coefficient calculated by the control unit 13 and applies it to the distortion compensation polynomial. The predistorter 301 generates a predistortion compensation signal A from the input signal X using a distortion compensation polynomial to which this coefficient is applied. Since the distortion compensation polynomial stored in the distortion compensation circuit 11 is obtained by appropriately modeling the compensated circuit 401 and obtained from the distortion characteristics of the model, the predistorter 301 can calculate the distortion compensation value with a small amount of calculation. The accuracy of distortion compensation can be increased. However, the initial value of Equation 12, which is the coefficient of the predistorter 301, is

It is.

(Update algorithm)
In order to accurately obtain the coefficient of the distortion compensation polynomial at one time, the input signal when the signal that covers all the amplitude (or power) of the assumed input signal is actually input to the amplifying device, and the input It is necessary to calculate the coefficient of the distortion compensation polynomial using the least square method using a set of output signals corresponding to the signal, and there is a problem that the amount of calculation becomes enormous. That is, in order to accurately calculate the coefficient of the distortion compensation polynomial, it is necessary to use a very large number of sampled input signals and output signals.

  Further, there is a problem that the coefficient of the distortion compensation polynomial of the amplifying device also changes due to temperature, humidity, and aging. Furthermore, it is necessary to update the coefficient of the distortion compensation polynomial with the passage of time while performing distortion compensation of the amplifier. An update algorithm for updating the coefficient of the distortion compensation polynomial with the passage of time is shown here.

  When updating the coefficient of the distortion compensation polynomial while compensating for distortion of the amplifying device, the input signal to the amplifying device is not x (n), but y (n) which is the output signal Y of the amplifying device is changed to x (n). The predistortion compensation signal A of Formula 11 that has been subjected to distortion compensation so as to be close to each other is an input signal.

も成立する。ここで、

とおく。但し、ｗ’_ｄ，ｋ（ｉ）、ｗ’_{ｒ，ｄ，ｌ}（ｉ）、およびｗ’_{ｒ，ｄ，ｌ，ｋ}（ｉ）はｉ回目の更新で得られた係数ｗ’_ｄ，ｋ、ｗ’_{ｒ，ｄ，ｌ}、およびｗ’_{ｒ，ｄ，ｌ，ｋ}をそれぞれ表す。 At this time, if distortion compensation of the amplifying apparatus is accurately performed, y (n) = x (n) is established.

Also holds. here,

far. However, w ′ _{d, k} (i), w ′ _{r, d, l} (i) and w ′ _{r, d, l, k} (i) are the coefficients w ′ _{d, k} obtained in the i-th update. , W ′ _{r, d, l} and w ′ _{r, d, l, k} respectively.

とおくと、誤差

が得られる。この誤差ｅ（ｎ）が零になるように歪補償多項式の係数を更新する。 If the distortion compensation of the amplifying device is not sufficient, y (n) = x (n) does not hold,

Error

Is obtained. The coefficient of the distortion compensation polynomial is updated so that this error e (n) becomes zero.

That is, the coefficients w ′ _{d, k} (i), w ′ _{r, d, l} (i), and w ′ _r satisfying the condition y (n) = x (n) that makes the input / output relationship of the entire amplification device linear. _{, D, l, k} (i) satisfies Equation (10). Here, the coefficients w ′ _{d, k} , w ′ _{r, d, l} , and w ′ _{r, d, l, k} are all arranged as w ₀ , w _{1 ,.} because represented, i-th coefficient _w 0 obtained _{updates, w 1, ···,} w _Q each _{w 0 (i), w 1} (i), ···, w Q (i) and In other words, the coefficients w ₀ (i), w ₁ (i),..., W _Q (i) satisfying the condition y (n) = x (n) that makes the input / output relationship of the entire amplifier circuit linear are mathematical expressions. 10 is satisfied. Accordingly, w ₀ (i), w ₁ (i),..., W _Q (i) may be obtained so that a ′ (n) and a ″ (n) match.

とおく。但し、ｉ≧０である。なお、数式２４の係数ｗ（ｉ）の初期値としては、ｗ（０）＝（１，０，・・・，０）^Ｔを用いるか、同じ被補償部に対して十分な取り込み点数Ｎのときに数式１５、数式１７または数式１８を用いて予め求めておいた係数ｗをｗ（０）＝ｗとして用いるか、同じ被補償部に対して十分に更新回数を確保して予め求めておいた係数の行列ｗ（∞）をｗ（０）＝ｗ（∞）として用いればよい。 Here, the update of w ₀ , w ₁ ,... W _Q will be described.

far. However, i ≧ 0. As an initial value of the coefficient w (i) in Expression 24, w (0) = (1, 0,..., 0) ^T is used, or a sufficient number N of acquisition points for the same compensated portion is used. Sometimes the coefficient w obtained in advance using Expression 15, Expression 17 or Expression 18 is used as w (0) = w, or it is obtained in advance by ensuring a sufficient number of updates for the same compensated portion. The matrix w (∞) of the coefficients may be used as w (0) = w (∞).

である。
また、行ｘ_ｎ（ｉ）を構成するベクトルｘ１_ｎ（ｉ）、ｘ２_ｎ（ｉ）およびｘ３_ｎ（ｉ）はそれぞれ数式２６、数式２７及び数式２８で表せる。

である。
また、行ｙ_ｎ（ｉ）を構成するベクトルｙ１_ｎ（ｉ）、ｙ２_ｎ（ｉ）およびｙ３_ｎ（ｉ）はそれぞれ数式３０、数式３１及び数式３２で表せる。

但し、Ｎは歪補償値を推定する際に使用する入出力信号の取り込み点数、Ｍは次の多項式係数の更新時に用いる入出力信号の取り込み開始までのサンプリング間隔数である。 Here, in order to simplify the expression, when Da = 0, R1 = 0, and D1 = 0, input signals corresponding to w ₀ (i), w ₁ (i),..., W _Q (i) The matrixes of X and output signal Y can be expressed as Equation 25 and Equation 29, respectively.

It is.
Further, the vectors x1 _n (i), x2 _n (i), and x3 _n (i) constituting the row x _n (i) can be expressed by Expression 26, Expression 27, and Expression 28, respectively.

It is.
Further, the vectors y1 _n (i), y2 _n (i), and y3 _n (i) constituting the row y _n (i) can be expressed by Expression 30, Expression 31, and Expression 32, respectively.

Here, N is the number of input / output signal capture points used when estimating the distortion compensation value, and M is the number of sampling intervals until the start of input / output signal capture used when updating the next polynomial coefficient.

とおくと、連立方程式

によりｗ（ｉ）を更新すればよい。但し、μは０＜μ≦１．０を満たす更新係数である。 Also,

Then, simultaneous equations

The w (i) may be updated by However, μ is an update coefficient that satisfies 0 <μ ≦ 1.0.

とする（図５）。但し、０＜μ_ＭＩＮ＜μ_ＭＡＸ≦１．０であり、０≦I_ＭＩＮ＜I_ＭＡＸである。このように、更新開始時には更新係数の値を大きくしておき、更新が進むにつれて更新係数の値を小さくすると、収束速度が速く、かつ収束後の歪補償の精度を高める制御が可能となる。尚、数式３７は更新係数μを適応的に変える関数の一例であり、更新係数μを適応的に変える関数としては更新の回数ｉを変数とした関数であれば他の形でもよい。 In the present invention, the update coefficient μ is adaptively changed according to the number of updates or the power of the error signal e (i). For example, when the update coefficient μ is changed according to the number of updates as an example of the present invention, the update coefficient is

(FIG. 5). However, 0 <μ _MIN <μ _MAX ≦ 1.0 and 0 ≦ I _MIN <I _MAX . As described above, if the value of the update coefficient is increased at the start of the update and the value of the update coefficient is decreased as the update progresses, it is possible to perform control that increases the convergence speed and increases the accuracy of distortion compensation after convergence. Note that Formula 37 is an example of a function that adaptively changes the update coefficient μ, and the function that adaptively changes the update coefficient μ may be any other form as long as the function uses the number of updates i as a variable.

更新係数を数式３８の関数である

とする（図６）。但し、０＜μ_ＭＩＮ＜μ_ＭＡＸ≦１．０であり、０＜Ｓ_ＴＨ１≦Ｓ_ＴＨ２である。このように、更新係数μを誤差電力の関数として誤差電力に応じて更新係数を変化させると誤差電力が大きいときは更新係数を大きくして追従速度、および収束速度が速くなるように動作し、誤差電力が小さいときは更新係数を小さくして歪補償の精度を高める制御が可能となる。尚、数式３９は更新係数μを適応的に変える関数の一例であり、更新係数μを適応的に変える関数としては誤差信号ｅ（ｉ（Ｎ＋Ｍ）＋ｎ）の電力｜ｅ（ｉ（Ｎ＋Ｍ）＋ｎ）｜^２を変数とした関数であれば他の形でもよい。 As another example of the present invention, when the update coefficient μ is changed according to the power | e (i (N + M) + n) | ² of the error e (i (N + M) + n), the total error power is reduced. With the formula,

The update coefficient is a function of Equation 38.

(FIG. 6). However, a _{0 <μ MIN <μ MAX ≦} 1.0, is _{0 <S TH1} ≦ _{S TH2.} In this way, when the update coefficient μ is changed as a function of the error power and the update coefficient is changed according to the error power, when the error power is large, the update coefficient is increased and the tracking speed and the convergence speed are increased. When the error power is small, it is possible to perform control to increase the accuracy of distortion compensation by reducing the update coefficient. Equation 39 is an example of a function that adaptively changes the update coefficient μ. The function that adaptively changes the update coefficient μ is the power | e (i (N + M) + n of the error signal e (i (N + M) + n). ) | Other forms may be used as long as the function has ² as a variable.

  The predistorter according to the present invention can be applied to a power amplifier of a radio transmitter used in a mobile communication base station or the like.

It is a block diagram explaining the structure of the predistorter which concerns on this invention. It is a block diagram explaining the structure of the predistorter which concerns on this invention. It is a block diagram explaining the distortion compensation circuit of the predistorter concerning the present invention. It is the figure which modeled the amplifier circuit comprised with the some amplifier. It is a figure explaining Numerical formula 37. It is a figure explaining Numerical formula 39.

Explanation of symbols

301, 302: Predistorter 11: Distortion compensation circuit 13: Control unit 401: Compensated circuit 511: Delay element 512-j: Amplitude value function (j is a natural number)
513: Element amplifier 514: Complex multiplier 515: Integrator X: Input signal Y: Output signal A: Predistortion compensation signal

Claims (4)

A distortion compensation circuit for outputting a predistortion compensation signal generated by substituting an input signal into a distortion compensation polynomial to a compensated circuit;
The input signal and the output signal of the compensated circuit are input, and the difference and variable between the signal generated by substituting the input signal into a distortion compensation polynomial and the signal generated by substituting the output signal into the distortion compensation polynomial A control unit for updating a coefficient value of the distortion compensation polynomial based on an update coefficient;
A predistorter comprising: A distortion compensation circuit for outputting a predistortion compensation signal generated by substituting an input signal into a distortion compensation polynomial to a compensated circuit;
The predistortion compensation signal and the output signal of the circuit to be compensated are input, and based on a difference between the predistortion compensation signal and a signal generated by substituting the output signal into the distortion compensation polynomial and a variable update coefficient A control unit for updating the coefficient value of the distortion compensation polynomial;
A predistorter comprising:   The said control part determines the said update coefficient used when updating the coefficient of the said distortion compensation polynomial based on the frequency | count that the said distortion compensation circuit updated the said distortion compensation value, The Claim 1 or 2 characterized by the above-mentioned. The predistorter described.   The control unit determines the update coefficient to be used when updating a coefficient of the distortion compensation polynomial based on a difference between the input signal and an output signal of the compensated circuit. The predistorter described in 1.

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