JP2009177551A - Distortion compensator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine a direction in which a distortion compensation amount of power or phase is varied, in order that an output signal becomes closer to an input signal formed from an input I signal and an input Q signal. <P>SOLUTION: A distortion compensator is characterized in that signal amplitudes of the input I signal and the input Q signal to the distortion compensation apparatus are regarded as values of I coordinates Ia and Q coordinates Qa of an input signal point 101, signal amplitudes of a demodulation I signal and a demodulation Q signal, obtained by demodulating an output signal from the distortion compensation apparatus are regarded as values of I coordinates Ib and Q coordinates Qb of a demodulation signal point 102, and a power increasing/decreasing direction or a phase rotating direction to change a distortion compensation amount is determined in such a direction that the demodulation signal point 102 gets closer to the input signal point 101. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a distortion compensation apparatus and method used in a radio transmission apparatus, and more particularly to an ADPD (Adaptive Digital Predistortion) for compensating distortion generated in an amplifier.

  One method of compensating for distortion generated in an amplifier is predistortion distortion compensation (see, for example, Patent Document 1). In predistortion distortion compensation, an LUT (Look Up Table) in which a distortion compensation amount is determined for each signal power of an input signal is prepared, and the input signal is multiplied by the distortion compensation amount determined by the LUT. In this way, distortion that is opposite to that generated in the amplifier is generated in the input signal in advance, so that distortion of the output signal in the entire distortion compensator is compensated.

  In the conventional predistortion distortion compensation, once an LUT is created, the LUT is used. For this reason, it is difficult to perform adaptive distortion compensation of the amplifier, and when the distortion characteristics fluctuate due to temperature and aging, it is impossible to compensate for distortion of the output signal from the distortion compensator.

Even when the LUT is corrected, it is difficult to determine whether distortion has occurred in either the power or phase of the output signal. Therefore, a distortion compensation device for only one of the power or phase of the output signal is performed. I stayed. For this reason, in the conventional predistortion distortion compensation, it is difficult to bring the power and phase of the output signal closer to the input signal.
JP 2006-10645 A

  Therefore, an object of the present invention is to determine the direction in which the power or phase distortion compensation amount is changed so that the output signal approaches the input signal.

  In order to achieve the above object, the distortion compensator according to the present invention has a demodulated signal point on the IQ coordinate plane specified by the signal amplitude of the demodulated I signal and demodulated Q signal demodulated from the output signal from the distortion compensator. The power or phase of the input signal formed by the input I signal and the input Q signal so as to approach the input signal point on the IQ coordinate plane specified by the signal amplitude of the input I signal and the input Q signal to the distortion compensator. It is characterized in that the direction in which the distortion compensation amount is changed is determined.

  A distortion compensation apparatus according to the present invention is a distortion compensation apparatus that determines an increase / decrease direction of power of an orthogonally modulated output signal, and an input terminal to which an input I signal and an input Q signal are input. A demodulation circuit that demodulates an output signal from the distortion compensation device and outputs a demodulated I signal and a demodulated Q signal; a square sum of signal amplitudes of the input I signal and the input Q signal; the demodulated I signal; And a first power distortion compensation direction determining circuit that calculates a difference from the square sum of the signal amplitude of the demodulated Q signal and determines the increase / decrease direction of the power according to the sign of the difference.

  The first power distortion compensation direction determining circuit calculates a difference between a square sum of signal amplitudes of the input I signal and the input Q signal and a square sum of signal amplitudes of the demodulated I signal and the demodulated Q signal from the demodulation circuit. Therefore, the difference between the power of the input signal formed by the input I signal and the input Q signal in the orthogonal coordinate system and the power of the output signal formed by the demodulated I signal and the demodulated Q signal can be calculated. Since the first power distortion compensation direction determination circuit determines based on the sign of the difference, the power of the output signal can be brought close to the power of the input signal.

  A distortion compensation apparatus according to the present invention is a distortion compensation apparatus that determines an increase / decrease direction of power of an orthogonally modulated output signal, and an input terminal to which an input I signal and an input Q signal are input. A demodulating circuit that demodulates the output signal from the distortion compensation device and outputs a demodulated I signal and a demodulated Q signal, and slightly changes the increase / decrease direction of the power to change the signal amplitude of the input I signal and the input Q signal. A second power distortion compensation direction determining circuit that determines an increase / decrease direction of the power so that a difference between a square sum and a square sum of signal amplitudes of the demodulated I signal and the demodulated Q signal is reduced. Features.

  The second power distortion compensation direction determining circuit calculates a difference between a square sum of signal amplitudes of the input I signal and the input Q signal and a square sum of signal amplitudes of the demodulated I signal and the demodulated Q signal from the demodulation circuit. Therefore, the difference between the power of the input signal formed by the input I signal and the input Q signal in the orthogonal coordinate system and the power of the output signal formed by the demodulated I signal and the demodulated Q signal can be calculated. Since the second power distortion compensation direction determination circuit determines the increase / decrease direction of the power so that the difference becomes small, the power of the output signal can be brought close to the power of the input signal.

  A distortion compensation apparatus according to the present invention is a distortion compensation apparatus that determines a rotation direction of a phase of an orthogonally modulated output signal, and an input terminal to which an input I signal and an input Q signal are input. A demodulation circuit that demodulates an output signal from the distortion compensation device and outputs a demodulated I signal and a demodulated Q signal; and a phase distortion compensation amount is minutely changed to change a signal amplitude of the input I signal and the demodulated I signal. A first phase distortion compensation direction determining circuit that determines the rotational direction of the phase so that the sum of the square of the difference and the square of the difference between the signal amplitudes of the input Q signal and the demodulated Q signal is small. It is characterized by that.

  Since the first phase distortion compensation direction determining circuit calculates the sum of the square of the difference between the signal amplitudes of the input I signal and the demodulated I signal and the square of the difference between the signal amplitudes of the input Q signal and the demodulated Q signal, The distance between the input signal point of the input signal formed by the input I signal and the input Q signal in the coordinate system and the output signal point of the output signal formed by the demodulated I signal and the demodulated Q signal can be calculated. Since the first phase distortion compensation direction determination circuit determines the phase rotation direction so that the sum is small, the output signal point can be brought close to the input signal point. As a result, the phase of the output signal can be brought close to the phase of the input signal.

  A distortion compensation apparatus according to the present invention is a distortion compensation apparatus that determines a rotation direction of a phase of an orthogonally modulated output signal, and an input terminal to which an input I signal and an input Q signal are input. A demodulation circuit that demodulates an output signal from the distortion compensation device and outputs a demodulated I signal and a demodulated Q signal, and absolute coordinates having a point where the signal amplitude of the input I signal and the input Q signal becomes zero as an origin A demodulated signal point specified by the signal amplitude of the demodulated I signal and the demodulated Q signal is provided with relative coordinates with the input signal point specified by the signal amplitude of the input I signal and the input Q signal as the origin. Is selected from the four phase limits of the relative coordinates, and it is determined whether the selected phase limit is positioned in the right or left rotation direction in the absolute coordinates with respect to the input signal point. Rotation direction and anti A second phase distortion compensation direction determination circuit for determining the direction of rotation of the phase such that the direction of, characterized in that it comprises a.

  The second phase distortion compensation direction determining circuit determines the phase distortion direction of the demodulated signal point by determining the phase target limit to which the demodulated signal point belongs and the absolute target phase and phase target limit to which the input signal point and the demodulated signal point belong. Can do. Since the second phase distortion compensation direction determining circuit determines the phase rotation direction in the direction in which the demodulated signal point approaches the input signal point, the phase of the output signal can be brought close to the phase of the input signal.

  In the distortion compensator according to the present invention, the second phase distortion compensation direction determining circuit determines whether the demodulation target point to which the demodulated signal point belongs when the phase target limit to which the demodulated signal point belongs includes the origin of the absolute coordinate. It is preferable to determine whether the input signal point belongs to the right or left rotation direction in the absolute coordinates rather than the absolute limit of the input signal point, and to determine the rotation direction of the phase so as to be opposite to the determined rotation direction. .

  Even if the phase target limit to which the demodulated signal point belongs does not belong to the rotation direction to the right or left of the input signal point, if the demodulated signal point includes the absolute coordinate origin, the demodulated signal has phase distortion. There is also. Even in this case, the second phase distortion compensation direction determination circuit can bring the phase of the output signal closer to the phase of the input signal.

  According to the present invention, the direction in which the power or phase distortion compensation amount is changed can be determined so that the output signal approaches the input signal.

  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.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram illustrating an example of a distortion compensation apparatus according to the present embodiment. The distortion compensation apparatus 91 includes an input terminal 11, an input power measurement circuit 12, a power distortion compensation amount instruction circuit 13, a power distortion compensation circuit 14, a phase distortion compensation amount instruction circuit 20, a phase distortion compensation circuit 21, Orthogonal modulation circuit 15, transmission power amplification circuit 16, demodulation circuit 17, distortion compensation direction determination circuit 41, distortion compensation amount correction circuit 19, delay adjustment circuit 31, D / A circuit 32, A / D The circuit 33 and the orthogonal coordinate conversion circuit 34 are provided. The distortion compensation direction determination circuit 41 functions as a first power distortion compensation direction determination circuit, a second power distortion compensation direction determination circuit, a first phase distortion compensation direction determination circuit, or a second phase distortion compensation direction determination circuit.

  The input terminal 11 receives an input I signal and an input Q signal to the distortion compensation device 91. The input power measurement circuit 12 measures the input power of the input signal formed by the input I signal and the input Q signal. The input power is the sum of the square of the signal amplitude of the input I signal and the square of the signal amplitude of the input Q signal when the input I signal and the input Q signal are arranged in an orthogonal coordinate system.

  The power distortion compensation amount instruction circuit 13 stores a power distortion compensation table, and instructs a power distortion compensation amount corresponding to the input power measured by the input power measurement circuit 12 based on the power distortion compensation table. The instruction is output to the power distortion compensation circuit 14. The power distortion compensation circuit 14 corrects the power formed by the input I signal and the input Q signal input to the input terminal 11 based on the distortion compensation amount indicated by the power distortion compensation amount instruction circuit 13 and outputs a compensation signal. To do. The correction is performed, for example, by multiplying the input I signal and the input Q signal by the power distortion compensation amount indicated by the power distortion compensation amount instruction circuit 13.

  The phase distortion compensation amount instruction circuit 20 stores a phase distortion compensation table and instructs the distortion compensation amount of the phase corresponding to the input power measured by the input power measurement circuit 12 based on the phase distortion compensation table. The instruction is output to the phase distortion compensation circuit 21. When the orthogonal coordinate conversion circuit 34 is provided, the phase distortion compensation amount instruction circuit 20 outputs the phase distortion compensation amount to the orthogonal coordinate conversion circuit 34. Then, the orthogonal coordinate conversion circuit 34 converts the phase distortion compensation amount output from the phase distortion compensation amount instruction circuit 20 into orthogonal coordinates and outputs it to the phase distortion compensation circuit 21. The phase distortion compensation circuit 21 corrects the phase formed by the input I signal and the input Q signal input to the input terminal 11 based on the distortion compensation amount indicated by the phase distortion compensation amount instruction circuit 20 and outputs a compensation signal. To do.

  The quadrature modulation circuit 15 performs quadrature modulation on the compensation signals output from the power distortion compensation circuit 14 or the phase distortion compensation circuit 21 and the power distortion compensation circuit 14 and the phase distortion compensation circuit 21 and outputs an output signal. After the D / A circuit 32 D / A converts the output signal output from the quadrature modulation circuit 15, the transmission power amplifier circuit 16 amplifies the output signal output from the quadrature modulation circuit 15. Thereby, the distortion compensation apparatus 91 can output the output signal by correcting the power and phase formed by the input I signal and the input Q signal.

  The demodulation circuit 17 demodulates the output signal amplified by the transmission power amplification circuit 16 and outputs a demodulated I signal and a demodulated Q signal. In the present embodiment, the output signal demodulated by the demodulation circuit 17 is a signal converted into a digital signal by the A / D circuit 33 after detecting the output signal output from the compensation device 91.

  The distortion compensation direction determination circuit 41 determines the power increase / decrease direction or phase rotation direction of the orthogonally modulated output signal. Since the distortion compensation direction determination circuit 41 determines the power increase / decrease direction and phase rotation direction of the orthogonally modulated output signal, the power and phase of the output signal can be brought close to the power and phase of the input I signal and input Q signal. it can. Here, the power increase / decrease direction or phase rotation direction of the output signal is determined by the demodulation I signal and the demodulation Q signal input from the demodulation circuit 17 and the input I signal and the input Q signal input from the delay adjustment circuit 31. The signal amplitude is used. Details will be described later.

  Here, it is preferable that the distortion compensation direction determination circuit 41 determines both the increase / decrease direction of the output signal power and the phase rotation direction. Furthermore, it is preferable that the relative pull-in speed for determining the increase / decrease direction of the power of the output signal and the pull-in speed for determining the phase rotation direction are variable. As a result, the power and phase of the output signal can be efficiently brought close to the power and phase formed by the input I signal and the input Q signal.

  In addition, when the power distortion compensation amount is a distortion compensation amount obtained by connecting the power distortion compensation amount at each operation point with the signal power at the end point in the section in which the power distortion compensation table divides the signal power as the operation point, the power of the output signal The increase / decrease direction is preferably determined for each detection section composed of one or more sections obtained by dividing the signal power. In this case, the distortion compensation amount correction circuit 19 increases or decreases the power distortion compensation amount at one specific point among the operation points, and determines the power distortion compensation amount at the specific point at which the power distortion in the detection section is minimized. The determination is performed for each predetermined specific point, and the power distortion compensation table stored in the power distortion compensation amount instruction circuit 13 is updated. Similarly, when the phase distortion compensation amount is a distortion compensation amount obtained by connecting the phase distortion compensation amount at each operation point with the signal power at the end point in the section in which the phase distortion compensation table divides the signal power as the operation point, the output signal The phase rotation direction is preferably determined for each detection section composed of one or more sections obtained by dividing the signal power. In this case, the distortion compensation amount correction circuit 19 increases or decreases the phase distortion compensation amount at one specific point among the operation points, and determines the phase distortion compensation amount at the specific point at which the phase distortion in the detection section is minimized. The determination is performed for each predetermined specific point, and the phase distortion compensation table stored in the phase distortion compensation amount instruction circuit 20 is updated. Here, the signal power corresponds to the power of the input signal formed by the input I signal and the input Q signal. In this case, the signal amplitudes of the input I signal, the input Q signal, the demodulated I signal, and the demodulated Q signal are predetermined values in the detection interval. The predetermined value for the signal amplitude of the input I signal and the input Q signal is, for example, an average value in the detection section. The predetermined value for the signal amplitude of the demodulated I signal and the demodulated Q signal is, for example, one specific point among the operation points in the section.

  The distortion compensation amount correction circuit 19 has a function as a power distortion compensation amount correction circuit and a phase distortion compensation amount correction circuit. The power distortion compensation amount correction circuit corrects the distortion compensation amount of the power distortion compensation circuit 14 so that the power of the output signal increases or decreases in the power increase / decrease direction determined by the distortion compensation direction determination circuit 41. To correct the power distortion compensation amount, for example, the power distortion compensation table stored in the power distortion compensation amount instruction circuit 13 is updated. The phase distortion compensation amount correction circuit corrects the distortion compensation amount of the phase distortion compensation circuit 21 so that the phase of the output signal rotates in the rotation direction of the phase determined by the distortion compensation direction determination circuit 41. To correct the phase distortion compensation amount, for example, the phase distortion compensation table stored in the phase distortion compensation amount instruction circuit 20 is updated. The distortion compensation amount correction circuit 19 has a function as a power distortion compensation amount correction circuit or a phase distortion compensation amount correction circuit, so that the power or phase of the output signal is changed to that of the input signal formed by the input I signal and the input Q signal. It can be close to power or phase.

  Moreover, it is preferable that the distortion compensation amount correction circuit 19 has a function as both a power distortion compensation amount correction circuit and a phase distortion compensation amount correction circuit. In this case, the power and phase of the output signal can be brought close to the power and phase of the input signal formed by the input I signal and the input Q signal. And since the pull-in speed in the increase / decrease direction of the power of the output signal and the rotation direction of the phase are variable, the power and phase of the output signal can be brought close to the power and phase of the input signal efficiently.

(First form of distortion compensation direction determination circuit 41)
A first power distortion compensation direction determination circuit, which is a first form of the distortion compensation direction determination circuit, will be described with reference to FIG. FIG. 2 shows an IQ coordinate plane for explaining an example of the first power distortion compensation direction determining circuit. The input signal point 101 is specified by the signal amplitudes of the input I signal Ia and the input Q signal Qa. The demodulated signal point 102 is specified by the signal amplitudes of the demodulated I signal Ib and demodulated Q signal Qb. At this time, the first power distortion compensation direction determining circuit determines the sum of squares of the signal amplitudes of the input I signal Ia and the input Q signal Qa (Ia ² + Qa ² ) and ² of the signal amplitudes of the demodulated I signal Ib and the demodulated Q signal Qb. sum difference _E a ⁼ a ^{(Ib 2 + Qb 2) {} (Ia 2 + Qa 2) - (Ib 2 + Qb 2)} was calculated to determine the increase or decrease direction of the power according to the sign of the difference _{E a.} By calculating the difference E _A, it can determine whether the smaller or the power of the demodulated signal is larger than the power of the input signal.

As shown in FIG. 2, if the difference E _A is a negative value, the first power distortion compensation direction determination circuit, the increase or decrease direction of the power is determined in a direction to reduce the power. On the other hand, if the difference E _A is a positive value, the first power distortion compensation direction determination circuit, the increase or decrease direction of the power is determined so as to increase the power. Thereby, the first power distortion compensation direction determining circuit can bring the power of the output signal closer to the power of the input signal formed by the input I signal Ia and the input Q signal Qa. Incidentally, the difference _{E A} ^{is -} may be calculated by ^{{(Ib 2 + Qb 2)} (Ia 2 + Qa 2)}. In this case, the determined increase / decrease direction may be reversed.

(Second form of distortion compensation direction determination circuit 41)
The second power distortion compensation direction determining circuit, which is a second form of the distortion compensation direction determining circuit, slightly changes the increase / decrease direction of power, and the sum of squares of the signal amplitudes of the input I signal Ia and the input Q signal Qa (Ia ² + Qa). ² ) and the difference E _A = {(Ia ² + Qa ² ) − (Ib ² + Qb ² )} between the square sums (Ib ² + Qb ² ) of the signal amplitudes of the demodulated I signal Ib and demodulated Q signal Qb. Determine the direction of power increase / decrease. The power that is slightly changed by the second power distortion compensation direction determining circuit is, for example, the distortion compensation amount of the power corrected by the power distortion compensation circuit 14 shown in FIG. 1 or the instruction of the power distortion compensation amount instruction circuit 13 shown in FIG. Is the amount of distortion compensation of the power to be transmitted.

For example, the second power distortion compensation direction determination circuit when the minutely changed distortion compensation amount of power to correct the power distortion compensating circuit, the difference E _A described above is increased or decreased. If the difference E _A when reduced power decreases, increasing or decreasing direction of the power by the second power distortion compensation direction determination circuit determines is a direction of decreasing the power. If the difference E _A when increased power is reduced, increasing or decreasing direction of the power by the second power distortion compensation direction determination circuit determines is a direction of increasing the power. Since the second power distortion compensation direction determination circuit to reduce the difference E _A, it can be approximated to the power of the input signal to form the input I signal and the input Q signal power of the output signal.

(Third form of distortion compensation direction determination circuit 41)
A first phase distortion compensation direction determination circuit, which is a third form of the distortion compensation direction determination circuit, will be described with reference to FIG. FIG. 3 shows an IQ coordinate plane for explaining an example of the first phase distortion compensation direction determining circuit. The first phase distortion compensation direction determining circuit slightly changes the phase distortion compensation amount, and squares (Ia−Ib) ² of the difference between the signal amplitudes of the input I signal Ia and the demodulated I signal Ib, the input Q signal Qa, and the demodulated Q the square of the difference between the signal amplitude of the signal Qb is the sum E _P and (Qa-Qb) ² determines the rotational direction of the phase to be smaller. The phase rotation direction that is slightly changed by the first phase distortion compensation direction determination circuit is, for example, the distortion compensation amount of the phase corrected by the phase distortion compensation circuit 21 or the distortion compensation amount of the phase indicated by the phase distortion compensation circuit 21. is there.

For example, the first phase distortion compensation direction determination circuit rotates the phase distortion compensation amount of the phase distortion compensation circuit 21, the difference E _P described above is increased or decreased. When the difference E _P becomes small when the phase distortion compensation amount is rotated to the right, the rotation direction of the phase to be determined is the direction to rotate the phase to the right. If the difference E _P is small when the phase distortion compensation amount is rotated counterclockwise, the phase rotation direction to be determined is the direction of rotating the phase counterclockwise. The first phase distortion compensation direction determination circuit, so to reduce the difference E _P, can be brought close to the input signal of the phase forming the phase of the output signal input I signal and the input Q signal.

(Fourth form of distortion compensation direction determination circuit 41)
A second phase distortion compensation direction determination circuit, which is a fourth form of the distortion compensation direction determination circuit, will be described with reference to FIG. FIG. 4 shows an IQ coordinate plane for explaining a first example of the second phase distortion compensation direction determining circuit. The second phase distortion compensation direction determining circuit uses the signal amplitudes of the input I signal Ia and the input Q signal Qa on the absolute coordinates with the origin O as the point where the signal amplitudes of the input I signal Ia and the input Q signal Qa become zero. Relative coordinates with the specified input signal point 101 as the origin O ′ are provided, and the phase target limit to which the demodulated signal point 102 specified by the signal amplitudes of the demodulated I signal Ib and demodulated Q signal Qb belongs is four phase target limits in relative coordinates. Select from. For example, as shown in FIG. 4, the sign of the signal amplitude difference (Ia-Ib) between the input I signal Ia and the demodulated I signal Ib is positive, and the signal amplitude of the input Q signal Qa and the demodulated Q signal Qb is If the sign of the difference (Qa−Qb) is negative, the second phase distortion compensation direction determination circuit selects the second phase target limit as the phase target limit to which the demodulation signal point 102 belongs. Similarly, if the sign of the difference (Ia−Ib) is positive and the sign of the difference (Qa−Qb) is positive, the second phase distortion compensation direction determining circuit determines the third phase target limit as the difference (Ia− If the sign of Ib) is negative and the sign of the difference (Qa−Qb) is negative, the first phase target limit is set, and the sign of the difference (Ia−Ib) is negative and the sign of the difference (Qa−Qb) is set If it is positive, the fourth phase target limit is selected.

  Thereafter, the second phase distortion compensation direction determination circuit determines whether the selected phase target limit is located in the right or left rotation direction in absolute coordinates with respect to the input signal point, and a direction opposite to the determined rotation direction. The phase rotation direction is determined so that The determination as to whether the position is in the right or left rotation direction can be made by calculating the absolute target limit of the input signal point 101 and the demodulated signal point 102. FIG. 5 shows an example of determination as to whether the position is in the right or left rotation direction. When the absolute target limit of the input signal point 101 and the demodulated signal point 102 is both the first absolute target limit, it is determined that the second phase target limit of the demodulated signal point 102 is located in the left rotation direction in the absolute coordinates from the origin O ′. In this case, the second phase distortion compensation direction determination circuit determines the right rotation direction. On the contrary, if the absolute target limit of the input signal point 101 and the demodulated signal point 102 is both the first absolute target limit and the demodulated signal point 102 is the fourth phase target limit, the second phase distortion compensation direction determining circuit Determine the left direction of rotation. Here, in the present embodiment, the right direction, that is, the clockwise direction is indicated as a negative direction, and the left direction, that is, the counterclockwise direction is indicated as a positive direction.

  As shown in FIG. 4, the second phase distortion compensation direction determination circuit determines the phase target limit to which the demodulated signal point 102 belongs, and the absolute target phase and phase target limit to which the input signal point 101 and demodulated signal point 102 belong. The direction of distortion of the phase of the point 102 can be determined. The second phase distortion compensation direction determination circuit determines the rotation direction of the phase in a direction in which the demodulated signal point 102 approaches the input signal point 101 that is the origin of the relative coordinates, so that the phase of the output signal approaches the phase of the input signal. Can do.

  FIG. 6 shows an IQ coordinate plane for explaining a second example of the second phase distortion compensation direction determining circuit. In the second phase distortion compensation direction determining circuit, when the phase target limit to which the demodulated signal points 102 a and 102 b belong includes the origin O of the absolute coordinate, the absolute target limit to which the demodulated signal points 102 a and 102 b belong is more than the absolute target limit of the input signal point 101. Is also determined to belong to the right or left rotation direction in absolute coordinates. For example, in the case of the demodulated signal point 102a, it is determined that the third phase target limit to which the demodulated signal point 102a belongs includes the origin O and belongs to the rotation direction to the right of the first absolute target limit to which the input signal point 101 belongs. In the case of the demodulated signal point 102b, it is determined that the third phase target limit to which the demodulated signal point 102b belongs includes the origin O and belongs to the rotation direction to the left of the first target limit to which the input signal point 101 belongs.

  Then, the second phase distortion compensation direction determination circuit determines the phase rotation direction so as to be opposite to the determined rotation direction. For example, since it is determined that the demodulated signal point 102a belongs to the right rotation direction, the phase rotation direction is determined to be the left rotation direction. Since it is determined that the demodulated signal point 102b belongs to the left rotation direction, the phase rotation direction is determined so as to be the right rotation direction.

  Even when the phase target limit to which the demodulated signal points 102a and 102b belong, such as the demodulated signal points 102a and 102b, includes the origin O of the absolute coordinates, the distortion of the output signal is corrected if the phase of the output signal is not rotated. You may not be able to. Even in such a case, the second phase distortion compensation direction determining circuit can bring the phase of the output signal closer to the phase of the input signal formed by the input I signal Ia and the input Q signal Qa.

  The second phase distortion compensation direction determination circuit determines whether the selected phase target limit is located in the right or left rotation direction in absolute coordinates with respect to the input signal point by referring to the stored rotation direction determination table. May be. FIG. 7 shows an example of the rotation direction determination table. In this case, the second phase distortion compensation direction determining circuit selects the absolute target limit of the input signal point 101 and the demodulated signal point 102 and the phase target limit of the demodulated signal point 102 shown in FIG. Here, instead of selecting the phase target limit, the difference in signal amplitude between the input I signal Ia and the demodulated I signal Ib (Ia-Ib) and the difference in signal amplitude between the input Q signal Qa and the demodulated Q signal Qb (Qa-Qb). May be directly referred to. When the absolute limit of the input signal point and the demodulated signal point is different, it may be determined whether the demodulated signal point is positioned in the right or left rotation direction in absolute coordinates with respect to the input signal point only by the combination of the absolute limit. Further, depending on the combination of the absolute limit of the input signal point and the demodulated signal point, as described in “+ or −” in the rotation direction column, depending on which of the right direction and the left direction is closer, You may determine whether it is located in the left rotation direction.

(Example of power and phase distortion compensation 1)
FIG. 8 shows an IQ coordinate plane for explaining a first example of power and phase distortion compensation. In the first example of power and phase distortion compensation, the distortion compensation amount is changed in the direction determined by the first power distortion compensation direction determining circuit and the first phase distortion compensation direction determining circuit. The first power distortion compensation direction determination circuit determines the power increase / decrease direction 111, and the distortion compensation amount correction circuit 19 increases / decreases the power distortion compensation amount in the power increase / decrease direction 111. On the other hand, the first phase distortion compensation direction determination circuit determines the phase rotation direction 112, and the distortion compensation amount correction circuit 19 rotates the phase distortion compensation amount in the phase rotation direction 112. As a result, the demodulated signal point 102 moves on the path in the power increasing / decreasing direction 111 and the path in the phase rotating direction 112 so as to approach the input signal point 101.

  As described above, by combining the first power distortion compensation direction determination circuit and the first phase distortion compensation direction determination circuit, even if the power and phase of the demodulation signal point 102 are different from those of the input signal point 101, the demodulation signal The point 102 can be brought close to the input signal point 101. Furthermore, if the pull-in speed of the first power distortion compensation direction determination circuit and the pull-in speed of the first phase distortion compensation direction determination circuit are adjusted, the range surrounded by the path of the power increase / decrease direction 111 and the path of the phase rotation direction 112 An arbitrary route can be selected. Although the first power distortion compensation direction determining circuit is used in the distortion compensation example 1, the same operation and effect can be obtained even when the second power distortion compensation direction determining circuit is used instead of the first power distortion compensation direction determining circuit. can get.

(Example of power and phase distortion compensation 2)
FIG. 9 shows an IQ coordinate plane for explaining a second example of power and phase distortion compensation. In the second example of power and phase distortion compensation, the distortion compensation amount is changed in the direction determined by the first power distortion compensation direction determining circuit and the second phase distortion compensation direction determining circuit. The first power distortion compensation direction determination circuit determines the power increase / decrease direction 111, and the distortion compensation amount correction circuit increases / decreases the power distortion compensation amount in the power increase / decrease direction 111. The second phase distortion compensation direction determination circuit determines the phase rotation direction 113, and the distortion compensation amount correction circuit rotates the phase distortion compensation amount in the increase / decrease direction 113. As a result, the demodulated signal point 102 moves on the path in the power increase / decrease direction 111 and the path in the phase rotation direction 113 so as to approach the input signal point 101.

  Here, when the pull-in speed of the second phase distortion compensation direction determination circuit is sufficiently faster than that of the first power distortion compensation direction determination circuit, the demodulated signal point 102 moves between the fourth phase target limit and the first phase target limit. For example, the second phase distortion compensation direction determination circuit having a high pull-in speed determines the phase rotation direction 113, and the distortion compensation amount correction circuit rotates the phase. Then, the demodulated signal point 102 once belongs to the first phase target limit. At this time, since the demodulated signal point 102 belongs to the first phase target limit, the second phase distortion compensation direction determination circuit does not determine the phase rotation direction. While the demodulated signal point 102 belongs to the first phase target limit, the first power distortion compensation direction determination circuit having a low pull-in speed determines the power increase / decrease direction 111, and the distortion compensation amount correction circuit increases the power distortion compensation amount. Increase or decrease in direction 111. When the distortion compensation amount correcting circuit increases or decreases the power distortion compensation amount in the power increase / decrease direction 111, the demodulated signal point 102 again belongs to the fourth phase target limit. At this time, since the demodulated signal point 102 belongs to the fourth phase target limit, the second phase distortion compensation direction determination circuit having a high pull-in speed determines the phase rotation direction 113, and the distortion compensation amount correction circuit rotates the phase. Then, the demodulated signal point 102 again belongs to the first phase target limit. As a result, when the pull-in speed of the second phase distortion compensation direction determining circuit is sufficiently higher than that of the first power distortion compensation direction determining circuit, the demodulated signal point 102 meanders on the phase target boundary near the phase target boundary. While approaching the input signal point 101.

  FIG. 10 shows a case where the phase target limit to which the demodulated signal point 102 belongs includes the origin O of the absolute coordinate, and the absolute target limit to which the demodulated signal point 102 belongs belongs to the right rotation direction in the absolute coordinate rather than the absolute target limit of the input signal point 101. An example of power and phase distortion compensation will be described. Also in this case, the first power distortion compensation direction determination circuit determines the power increase / decrease direction 111, and the second phase distortion compensation direction determination circuit determines the phase rotation direction 113. As a result, the demodulated signal point 102 moves on the path in the power increase / decrease direction 111 and the path in the phase rotation direction 113 so as to approach the input signal point 101.

  As described above, by combining the first power distortion compensation direction determination circuit and the second phase distortion compensation direction determination circuit, even if the power and phase of the demodulation signal point 102 are different from those of the input signal point 101, the demodulation signal The point 102 can be brought close to the input signal point 101. Further, as in the first distortion compensation example, by adjusting the pull-in speed of the first power distortion compensation direction determining circuit and the pull-in speed of the second phase distortion compensation direction determining circuit, the path and phase rotation in the power increasing / decreasing direction 111 are adjusted. An arbitrary route can be selected within a range surrounded by the route in the direction 113. Similar to the first distortion compensation example 1, the same operation and effect can be obtained by using the second power distortion compensation direction determining circuit instead of the first power distortion compensation direction determining circuit. Also,

(Embodiment 2)
FIG. 11 is a schematic configuration diagram illustrating an example of a distortion compensation apparatus according to the present embodiment. The distortion compensator 92 is different from the distortion compensator 91 described with reference to FIG. 1 in that it corresponds to steady error correction. Specifically, the distortion compensation device 92 includes an input terminal 11, a power distortion compensation circuit 14, a phase distortion compensation circuit 21, a quadrature modulation circuit 15, a demodulation circuit 17, a distortion compensation direction determination circuit 41, The compensation amount correction circuit 19, the delay adjustment circuit 31, the D / A circuit 32, the A / D circuit 33, and the orthogonal coordinate conversion circuit 34 are provided. Both configurations are as described in the first embodiment.

  Similarly to the first embodiment, the distortion compensator 92 includes the distortion compensation direction determination circuit 41 so that the output signal approaches the input signal formed by the input I signal and the input Q signal. It is possible to determine the direction in which the distortion compensation amount is changed.

  Then, the distortion compensation amount correction circuit 19 corrects the power distortion compensation circuit 14 so that the power of the output signal increases or decreases in the power increase / decrease direction determined by the distortion compensation direction determination circuit 41 as a power distortion compensation amount correction circuit. Increase or decrease the power. In addition, the distortion compensation amount correction circuit 19 is a phase distortion compensation amount correction circuit, and adjusts the phase to be corrected by the phase distortion compensation circuit 21 so that the output signal rotates in the rotation direction of the phase determined by the distortion compensation direction determination circuit 41. Rotate. As a result, the power and phase of the output signal can be brought close to the power and phase of the input signal formed by the input I signal and the input Q signal.

  It can be used as a distortion compensation device used for high-efficiency transmission of wireless communication.

1 is a schematic configuration diagram illustrating an example of a distortion compensation apparatus according to a first embodiment. It is an IQ coordinate plane explaining an example of a first power distortion compensation direction determination circuit. It is an IQ coordinate plane for explaining an example of the first phase distortion compensation direction determination circuit. It is an IQ coordinate plane for explaining a first example of the second phase distortion compensation direction determining circuit. It is an example of determination whether it is located in the right or left rotation direction. It is an IQ coordinate plane for explaining a second example of the second phase distortion compensation direction determining circuit. It is an example of a rotation direction determination table. It is an IQ coordinate plane for explaining a first example of power and phase distortion compensation. It is an IQ coordinate plane for explaining a second example of power and phase distortion compensation. Example of power and phase distortion compensation when the phase target limit to which the demodulated signal point belongs includes the origin of the absolute coordinate, and the absolute target limit to which the demodulated signal point belongs belongs to the right rotation direction in the absolute coordinate rather than the absolute target limit of the input signal point Show. FIG. 6 is a schematic configuration diagram illustrating an example of a distortion compensation apparatus according to a second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Input terminal 12 Input power measurement circuit 13 Power distortion compensation amount instruction | indication circuit 14 Power distortion compensation circuit 15 Orthogonal modulation circuit 16 Transmission power amplification circuit 17 Demodulation circuit 19 Distortion compensation amount correction circuit 20 Phase distortion compensation amount instruction circuit 21 Phase distortion compensation circuit 31 Delay adjustment circuit 32 D / A circuit 33 A / D circuit 34 Cartesian coordinate transformation circuit 41 Distortion compensation direction determination circuit 91, 92 Distortion compensation device 101 Input signal point 102, 102a, 102b Demodulation signal point 111 Power increase / decrease direction 112, 113 Phase rotation direction Ia Input I signal Qa Input Q signal Ib Demodulated I signal Qb Demodulated Q signal

Claims (5)

A distortion compensator that determines an increase / decrease direction of power of an orthogonally modulated output signal,
An input terminal to which an input I signal and an input Q signal are input to the distortion compensation device;
A demodulation circuit that demodulates an output signal from the distortion compensation device and outputs a demodulated I signal and a demodulated Q signal;
The difference between the sum of squares of the signal amplitudes of the input I signal and the input Q signal and the sum of the squares of the signal amplitudes of the demodulated I signal and the demodulated Q signal is calculated, and the power is calculated according to the sign of the difference. A first power distortion compensation direction determining circuit for determining an increase / decrease direction;
A distortion compensation apparatus comprising: A distortion compensator that determines an increase / decrease direction of power of an orthogonally modulated output signal,
An input terminal to which an input I signal and an input Q signal are input to the distortion compensation device;
A demodulation circuit that demodulates an output signal from the distortion compensation device and outputs a demodulated I signal and a demodulated Q signal;
The increase / decrease direction of the power is slightly changed so that the difference between the square sum of the signal amplitudes of the input I signal and the input Q signal and the square sum of the signal amplitudes of the demodulated I signal and the demodulated Q signal is reduced. A second power distortion compensation direction determining circuit for determining an increase / decrease direction of the power;
A distortion compensation apparatus comprising: A distortion compensator that determines a rotation direction of a phase of an orthogonally modulated output signal,
An input terminal to which an input I signal and an input Q signal are input to the distortion compensation device;
A demodulation circuit that demodulates an output signal from the distortion compensation device and outputs a demodulated I signal and a demodulated Q signal;
By slightly changing the amount of phase distortion compensation, the sum of the square of the difference between the signal amplitudes of the input I signal and the demodulated I signal and the square of the difference between the signal amplitudes of the input Q signal and the demodulated Q signal is small. A first phase distortion compensation direction determining circuit for determining the rotation direction of the phase so that
A distortion compensation apparatus comprising: A distortion compensator that determines a rotation direction of a phase of an orthogonally modulated output signal,
An input terminal to which an input I signal and an input Q signal are input to the distortion compensation device;
A demodulation circuit that demodulates an output signal from the distortion compensation device and outputs a demodulated I signal and a demodulated Q signal;
Relative with the input signal point specified by the signal amplitude of the input I signal and the input Q signal as the origin, on the absolute coordinates with the origin where the signal amplitude of the input I signal and the input Q signal is zero A coordinate target is provided, and a phase target limit to which the demodulated signal point specified by the signal amplitude of the demodulated I signal and the demodulated Q signal belongs is selected from the four phase target limits of the relative coordinates, and the selected phase target limit is the input signal point A second phase distortion compensation direction determining circuit that determines whether the rotation direction is the right or left rotation direction in the absolute coordinates and determines the rotation direction of the phase so as to be opposite to the determined rotation direction. ,
A distortion compensation apparatus comprising:   When the phase target limit to which the demodulated signal point belongs includes the absolute coordinate origin, the absolute phase limit to which the demodulated signal point belongs is more than the absolute target limit of the input signal point. 5. The distortion according to claim 4, wherein it is determined whether the rotation direction belongs to the right or left rotation direction in the absolute coordinates, and the rotation direction of the phase is determined to be opposite to the determined rotation direction. Compensation device.

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