JP5238461B2 - Predistorter - Google Patents

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.

In the conventional predistorter, as a conventional technique of the distortion compensation amplifying apparatus, a method using a single look-up table (LUT) (see, for example, Patent Document 1), or a distortion compensation polynomial is obtained after obtaining the LUT. There is known a method using a single LUT generated again using the same (for example, see Patent Document 2). In addition, conventional predistorters with memory effect countermeasures include a method based on a memory polynomial (for example, see Patent Document 3) and a method based on a Volterra series (for example, Patent Document 4). 5) is known.
Japanese Patent No. 3560398 JP 2006-093947 A JP 2004-320329 A JP 2004-320598 A JP 2007-282066 A

  In particular, in the prior art of the distortion compensation amplifying apparatus with a memory effect countermeasure, the distortion compensation polynomial term (or LUT) is used in order to improve accuracy in either the method based on the memory polynomial or the method based on the Volterra series. If the number of () is increased, the amount of calculation for obtaining the coefficient of the distortion compensation polynomial increases, and it takes a long time to calculate. As a result, the update time becomes long and the convergence speed becomes slow.

  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, the predistorter according to the present invention reduces the amount of calculation once by updating only the coefficients of some terms of the distortion compensation polynomial at the initial stage of updating. The time required for the update is reduced, the coefficient of the term to be calculated in stages is increased, and both the reduction of the time for the distortion compensation value to converge to the specified value and the distortion compensation accuracy are made compatible.

  Specifically, a predistorter according to the present invention has a distortion compensation polynomial that generates a predistortion compensation signal from an input signal, and outputs the predistortion compensation signal generated by the distortion compensation polynomial to a compensated circuit. The distortion compensation unit, the input signal and the output signal of the compensated circuit are input, and the signal generated by substituting the input signal into the distortion compensation polynomial and the output signal into the distortion compensation polynomial A control unit that calculates a coefficient of the distortion compensation polynomial so that a difference from the signal becomes small, and causes the distortion compensation unit to update the coefficient of the distortion compensation polynomial. The distortion compensation polynomial included in the distortion compensation unit calculates a plurality of distortion compensation values from each of a plurality of sampling signals that have captured the input signal at different times, and each of the distortion compensation values is calculated as any one of the sampling signals. The distortion signal is calculated by multiplying, all the distortion signals are combined to generate the predistortion compensation signal, and the control unit updates the distortion compensation polynomial coefficient number to be updated by the distortion compensation unit It is characterized by increasing step by step.

  Another predistorter according to the present invention includes a distortion compensation polynomial that generates a predistortion compensation signal from an input signal, and outputs the predistortion compensation signal generated by the distortion compensation polynomial to a compensated circuit. The difference between the compensation unit, the predistortion compensation signal, and the output signal of the compensated circuit is input, and the difference between the predistortion compensation signal and the signal generated by substituting the output signal into the distortion compensation polynomial is reduced. A control unit that calculates the coefficient of the distortion compensation polynomial and causes the distortion compensation unit to update the coefficient of the distortion compensation polynomial. The distortion compensation polynomial included in the distortion compensation unit calculates a plurality of distortion compensation values from each of a plurality of sampling signals that have captured the input signal at different times, and each of the distortion compensation values is calculated as any one of the sampling signals. The distortion signal is calculated by multiplying, all the distortion signals are combined to generate the predistortion compensation signal, and the control unit updates the distortion compensation polynomial coefficient number to be updated by the distortion compensation unit It is characterized by increasing step by step.

  At the start of distortion compensation, only the coefficients of some terms of the distortion compensation polynomial are updated, and the number of terms for updating the coefficients is increased as the update proceeds. In updating the distortion compensation polynomial, if the number of terms for updating the coefficient is reduced, the amount of calculation is reduced, so the update time is shortened and the convergence speed is increased. However, if the number of coefficient terms to be updated is reduced, the distortion compensation accuracy deteriorates. Therefore, the number of coefficient terms to be updated is increased stepwise to ensure distortion compensation accuracy. When the coefficients of the distortion compensation polynomial are updated in this way, the time taken from the start of operation to the first update is reduced, so the convergence speed is faster than the conventional technology, and the final distortion compensation accuracy is also the same as the conventional technology. Be the same.

  Therefore, the predistorter according to the present invention can increase the follow-up speed and the convergence speed at the initial stage when the update is started, and finally can obtain sufficient distortion compensation accuracy.

  The control unit of the predistorter according to the present invention can determine the number of coefficients of the distortion compensation polynomial to be updated by the distortion compensation unit based on the number of times of updating the coefficient of the distortion compensation polynomial.

  The control unit of the predistorter according to the present invention determines the number of coefficients of the distortion compensation polynomial to be updated by the distortion compensation unit based on a difference between the input signal and the output signal of the compensated circuit. May be.

  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 has a distortion compensation polynomial that generates the predistortion compensation signal A from the input signal X, and outputs the predistortion compensation signal A generated by the distortion compensation polynomial to the compensated circuit 401. Input signal X and output signal Y of compensated circuit 401 are input, and the difference between the signal generated by substituting input signal X into the distortion compensation polynomial and the signal generated by substituting output signal Y into the distortion compensation polynomial is small. And a control unit 13 that calculates the coefficient of the distortion compensation polynomial so that the distortion compensation unit 11 updates the coefficient of the distortion compensation polynomial.

  FIG. 2 is a block diagram illustrating the configuration of the predistorter 302 of this embodiment. The predistorter 302 has a distortion compensation polynomial that generates the predistortion compensation signal A from the input signal X, and outputs the predistortion compensation signal A generated by the distortion compensation polynomial to the compensated circuit 401; The predistortion signal A and the output signal Y of the compensated circuit 401 are input, and the distortion compensation polynomial A and the signal generated by substituting the output signal Y into the distortion compensation polynomial are reduced. And a control unit 13 that calculates the coefficient and causes the distortion compensation unit 11 to update the coefficient of the distortion compensation polynomial.

  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 illustrating the distortion compensator 11 of the predistorter 301 and the predistorter 302. The distortion compensation unit 11 has a distortion compensation polynomial expressed by Equation 11 or Equation 21 described later, and generates a predistortion compensation signal from the input signal X and outputs it to the compensated circuit 401. A distortion compensation polynomial calculates a distortion signal by calculating a plurality of distortion compensation values from each of a plurality of sampling signals that have captured the input signal X at different times, and multiplying each of the distortion compensation values by one of the sampling signals. The predistortion compensation signal A is generated by synthesizing all the distortion signals. 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 performs distortion so that the difference between the signal generated by substituting the input signal X for the distortion compensation polynomial or the signal generated by substituting the output signal Y for the distortion compensation polynomial and the predistortion compensation signal A approaches zero. Calculate the coefficient of the compensation polynomial. Further, the control unit 13 applies the calculated coefficient to the distortion compensation polynomial of the distortion compensation unit 11. The predistorter 301 and the predistorter 302 can follow the distortion variation generated in the compensated circuit 401 by the operation of the control unit 13. Further, in the initial stage of the update, the control unit 13 calculates only some of the distortion compensation polynomial terms and applies them to the distortion compensation polynomial, and calculates as the update progresses. The number of coefficients of the distortion compensation polynomial to be applied is increased stepwise and applied to the distortion compensation polynomial. Since the control unit 13 calculates the coefficient of the distortion compensation polynomial and applies it to the distortion compensation polynomial in this way, the time required from the start of operation to the first update is reduced, so that the convergence speed is faster than the conventional technique. And the final distortion compensation accuracy is the same as that of the prior art.

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 compensator 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 expressed as a function (combining polynomial) of the amplitude value of the input signal X

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.

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 perform distortion compensation for the amplifier circuit based on the model of FIG. 4, distortion compensation is performed by replacing 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

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, which is input to the amplifier.

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 unit 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 unit 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 amplification device, the input signal to the amplification device is not x (n), but y (n), which is the output signal Y of the amplification 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。 Also,

Then, simultaneous equations

The w (i) may be updated by However, μ satisfies 0 <μ ≦ 1.0.

と分割する。図５のように、更新を開始した初期の時点では歪補償多項式ａ’（ｎ）の一部ｂ_０（ｎ）の係数のみを計算して更新し、歪補償値に反映させる。更新が進むにつれてｂ_１（ｎ）、ｂ_２（ｎ）の順（もしくはｂ_２（ｎ）、ｂ_１（ｎ）の順）に追加して求める係数の個数を増やしていく。 In the present invention, the distortion compensation polynomial is divided into a plurality of groups, and only a part of the coefficient of the distortion compensation polynomial is calculated and applied at the initial time when the update is started, and the distortion compensation polynomial is calculated and applied as the update proceeds. Increase the number of coefficients in steps. For example, the distortion compensation polynomial a ′ (n) of Equation 21 is

And split. As shown in FIG. 5, at the initial time when updating is started, only the coefficients of part b ₀ (n) of the distortion compensation polynomial a ′ (n) are calculated and updated and reflected in the distortion compensation value. As the update progresses, the number of coefficients to be obtained is increased in the order of b ₁ (n) and b ₂ (n) (or in the order of b ₂ (n) and b ₁ (n)).

である。 B ₀ (n), b ₁ (n) and b ₂ (n) are

It is.

のような順番で、求める歪補償多項式の係数の数を増やしていく。 When the distortion compensation polynomial a ′ (n) is divided in this way, only the coefficient of c _0,0 (n) is calculated and updated at the initial stage where the update of the coefficient of the distortion compensation polynomial is started as shown in FIG. And reflected in distortion compensation, as the update progresses

In this order, the number of distortion compensation polynomial coefficients to be obtained is increased.

である。このとき、

のような順番で、求める歪補償多項式の係数を増やしていく。 Furthermore, c _{0, d} (n), c _{1, d} (n) and c _{2, d} (n) are

It is. At this time,

In this order, the coefficients of the distortion compensation polynomial to be obtained are increased.

  The division of the distortion compensation polynomial as described above can be finally divided into monomials which are the minimum units of the polynomial. The polynomials obtained by the division can be ordered as shown in FIGS. 5 and 6, for example. However, the ordering of FIGS. 5 and 6 is merely an example, and is not limited to this order.

  As shown in FIGS. 5 and 6, by calculating and applying the coefficients of the distortion compensation polynomial terms, the number of polynomial terms to be updated and used for distortion compensation is small at the initial stage of updating. Since the calculation amount to be calculated is reduced and the time required for one update is also reduced, the time until the distortion compensation amount converges to the specified value is reduced. Further, as the update progresses, the number of polynomial terms used for distortion compensation increases stepwise, so that the final distortion compensation accuracy increases. Therefore, it is possible to achieve both a reduction in time for the distortion compensation value to converge to the specified value and distortion compensation accuracy.

  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 the operation | movement at the time of the update of the predistorter which concerns on this invention. It is a figure explaining the operation | movement at the time of the update of the predistorter which concerns on this invention.

Explanation of symbols

301, 302: Predistorter 11: Distortion compensation unit 13: Control unit 22: Intensity calculation unit 23: Look-up table 24: Complex multiplier 401: Compensated circuit 511: Delay element 512-j: Amplitude value function (j is 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 unit that generates a predistortion compensation signal from an input signal, and outputs the predistortion compensation signal generated by the distortion compensation polynomial to a compensated circuit;
The input signal and the output signal of the compensated circuit are input, and a difference between a signal generated by substituting the input signal into the distortion compensation polynomial and a signal generated by substituting the output signal into the distortion compensation polynomial is A controller that calculates the coefficient of the distortion compensation polynomial so as to be reduced, and causes the distortion compensation unit to update the coefficient of the distortion compensation polynomial;
A predistorter comprising:
The distortion compensation unit
Generate a plurality of sampling signals that take in the input signal at different times,
A calculation result obtained by multiplying one sampling signal by at least a value based on the one sampling signal or a value based on another sampling signal is acquired, and the distortion compensation polynomial that adds all the calculation results is used to obtain the calculation result. Generate a predistortion signal,
The predistorter, wherein the control unit gradually increases the number of coefficients of the distortion compensation polynomial to be updated by the distortion compensation unit. A distortion compensation unit that generates a predistortion compensation signal from an input signal, and outputs the predistortion compensation signal generated by the distortion compensation polynomial to a compensated circuit;
The distortion compensation polynomial is inputted so that a difference between the predistortion compensation signal and a signal generated by substituting the output signal into the distortion compensation polynomial is reduced. A control unit that updates the coefficient of the distortion compensation polynomial to the distortion compensation unit;
A predistorter comprising:
The distortion compensation unit
Generate a plurality of sampling signals that take in the input signal at different times,
A calculation result obtained by multiplying one sampling signal by at least a value based on the one sampling signal or a value based on another sampling signal is acquired, and the distortion compensation polynomial that adds all the calculation results is used to obtain the calculation result. Generate a predistortion signal,
The predistorter, wherein the control unit gradually increases the number of coefficients of the distortion compensation polynomial to be updated by the distortion compensation unit.   The said control part determines the number of the coefficient of the said distortion compensation polynomial made to update with respect to the said distortion compensation part based on the frequency | count that the coefficient of the said distortion compensation polynomial was updated. Predistorter.   The control unit determines the number of coefficients of the distortion compensation polynomial to be updated by the distortion compensation unit based on a difference between the input signal and an output signal of the compensated circuit. Or the predistorter of 2.

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