JP4697778B2 - Distortion compensation apparatus and distortion compensation method - Google Patents

Description

  The present invention relates to a distortion compensation device and a distortion compensation method used for a power amplifier. In particular, the present invention relates to a distortion compensation apparatus and a distortion compensation method for performing linear amplification by performing predistortion (predistortion compensation) processing.

  In recent years, transmission systems such as CDMA (Code Division Multiple Access) have been put into practical use in the mobile communication field. A CDMA transmission amplifier is required to have high linearity for amplifying a broadband / high dynamic range signal with low distortion and high efficiency by suppressing unnecessary radio wave emission (radio wave emission outside the transmission band).

  Conventionally, as a method for compensating for nonlinear distortion of an amplifier, a negative feedback method, a feedforward method, a predistortion method, and the like are known.

  The negative feedback system is rarely used in a radio device of a base station because an oscillation phenomenon or the like is likely to occur when a signal becomes a wide band and operation instability increases.

  The feedforward method is used in many base station radios at present because it does not cause unstable operation in principle. However, the feed-forward method requires a configuration in which an error component is extracted and amplified separately by a sub-amplifier and then subtracted from the output signal of the main amplifier. There is a problem that decreases.

  On the other hand, the predistortion method is attracting attention as an alternative to the feedforward method because a sub-amplifier is not required, and research and development are underway. The principle of the distortion compensation predistortion method will be described below.

  FIG. 8 shows the amplification result when there is no distortion compensation. The amplifier has nonlinear characteristics such as AM / AM characteristics (amplitude distortion characteristics) and AM / PM characteristics (phase distortion characteristics) depending on the input amplitude. Because of this non-linear characteristic, the output waveform of the amplifier becomes non-linear.

  The AM / AM characteristic of the amplifier is non-linear in which the output signal level is saturated when the amplitude level of the input signal exceeds a certain value. When a linear input signal is amplified by this amplifier, the antenna output signal becomes nonlinear.

  The AM / PM characteristics of the amplifier are such that when the amplitude level of the input signal exceeds a certain value, the phase of the output signal rotates. When an input signal with no phase rotation is amplified by this amplifier, the antenna output signal is rotated in phase (see FIG. 10).

  FIG. 9 shows an amplification result when a predistortion compensation unit is provided to compensate for distortion. The distortion characteristic opposite to the distortion characteristic in the amplifier is applied in advance by the predistortion unit. When this signal is input to an amplifier, distortion characteristics are canceled and linear amplification is performed.

  FIG. 11 shows the frequency spectrum with and without distortion compensation. If distortion compensation is not performed, a large amount of power leaks out of the transmission band due to distortion characteristics, but power leaking out of the band can be suppressed by performing distortion compensation.

JP 2003-78360 A

  In the conventional predistortion method, a distortion compensation table is created in consideration of the nonlinear characteristics of the amplifier. In addition, the distortion compensation coefficient is adaptively calculated and the table is updated to cope with a change in the nonlinear characteristic of the amplifier due to a time change, a temperature change or the like. In the conventional system, analog signal processing parts such as an up-converter part and a quadrature modulation part are also included in this adaptive loop. For this reason, even the conventional method can follow the time change and temperature change of the up-converter unit and the quadrature modulation unit, but these changes fluctuate in a very short time compared to the fluctuation of the amplifier. It is necessary to follow in. In order to follow the time change and temperature change as accurately as possible, it is necessary to consider changes in the feedback side down converter, quadrature demodulation unit, and the like.

  The present invention provides a distortion compensation apparatus and a distortion compensation method capable of reducing the processing amount and power consumption by improving the distortion by adjusting the gain in the predistortion distortion compensation apparatus.

  The distortion compensation apparatus of the present invention is a distortion compensation apparatus that compensates for distortion that may occur in a transmission signal in accordance with the distortion characteristic of an amplifier in a wireless communication apparatus, and that has a distortion characteristic opposite to that of the amplifier in the transmission signal. A pre-multiplying distortion compensation unit, a distortion power calculation unit that calculates distortion power from a feedback signal of a transmission signal, a process determination unit that determines whether the calculated distortion power is greater than a predetermined threshold, and the process determination A gain setting unit that sets a gain to be applied to a transmission signal multiplied by a reverse distortion characteristic by the predistortion unit when the distortion power is determined by the unit to be greater than the predetermined threshold; and the gain setting unit A gain adjusting unit that multiplies the transmission signal by the gain set in step (b).

  With the above configuration, when the distortion power obtained from the feedback signal is larger than a predetermined threshold, the gain for the transmission signal is adaptively set. When the distortion power is improved by the gain setting, it is not necessary to calculate the distortion compensation coefficient in the compensation coefficient calculation unit, so that the processing amount and power consumption can be reduced.

  When the processing determination unit determines that distortion power is greater than the predetermined threshold, the gain setting unit sets a plurality of gains, and the gain adjustment unit multiplies each of the plurality of gains by a transmission signal, The distortion power calculation unit calculates a plurality of distortion powers from a feedback signal of a transmission signal corresponding to each of the plurality of gains, and the gain setting unit calculates a gain corresponding to the minimum distortion power among the calculated distortion powers. The distortion compensator can be configured to adjust the gain of the gain adjusting unit so that

  With the above configuration, it is possible to set a gain that minimizes distortion power.

  The above distortion compensation device includes an output calculation unit that calculates power of a transmission signal, and a compensation that calculates a compensation coefficient that represents a distortion characteristic opposite to the distortion characteristic of the amplifier in the predistortion unit based on the feedback signal. A coefficient calculation unit; and a distortion compensation table obtained by associating the power calculated by the output calculation unit with the compensation coefficient obtained from the feedback signal of the transmission signal corresponding to the power. it can. In this case, the processing determination unit determines whether the distortion power is greater than a predetermined threshold even after the gain is adjusted in the gain adjustment unit, and after the gain is adjusted in the gain adjustment unit, When the distortion power is larger than a predetermined threshold, the compensation coefficient calculation unit calculates a new compensation coefficient and updates the distortion compensation table with the new compensation coefficient.

  With the above configuration, even when the gain is not improved sufficiently only by the gain adjustment, the distortion can be further suppressed by updating the compensation coefficient.

  The distortion compensation apparatus described above can be used for a wireless communication apparatus. When the gain adjustment unit performs digital amplification, a D / A converter, a quadrature modulation unit, an up converter, and an amplifier may be connected to the subsequent stage of the gain adjustment unit to configure a wireless communication device. it can. In addition, the gain adjustment unit can be configured by a variable attenuator, and an amplifier can be connected to the subsequent stage of the variable attenuator to configure a radio communication apparatus.

  The wireless communication device can be used as a wireless communication base station device or a wireless mobile communication device.

  The distortion compensation method of the present invention is a distortion compensation method for compensating for distortion that may occur in a transmission signal in accordance with the distortion characteristics of an amplifier in a wireless communication apparatus, and transmits distortion characteristics opposite to the distortion characteristics of the amplifier. A step of multiplying the signal, a step of calculating distortion power from a feedback signal of the transmission signal, a step of determining whether the calculated distortion power is greater than a predetermined threshold, and the distortion power is greater than the predetermined threshold When it is determined that the transmission signal is large, the method includes a step of setting a gain to be applied to the transmission signal multiplied by the reverse distortion characteristic, and a step of multiplying the transmission signal by the set gain. An application example of this method can be considered as in the above-described apparatus. A program for causing an arithmetic unit to execute each step of the distortion compensation method is also included in the present invention.

  According to the distortion compensation apparatus and the distortion compensation method of the present invention, it is possible to improve distortion by adjusting the gain of a transmission signal and reduce the number of times of calculating a distortion compensation coefficient, thereby reducing processing amount and power consumption. be able to.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a power amplification device (wireless communication device) 100 according to a first embodiment of the present invention. The power amplifying apparatus 100 includes delay devices 11a, 11b, 11c, and 11d, a predistortion compensation unit 13, a gain adjustment unit 47, D / A converters 21a and 21b, an orthogonal modulation unit 23, and an upconverter 25. , Amplifier 27, directional coupler 29, antenna 31, oscillator 39, down converter 33, A / D converters 37a and 37b, gain setting unit 45, distortion power calculation unit 41, and processing determination A unit 43, a compensation coefficient calculation unit 19, a power calculation unit 15, and a distortion compensation table 17 are configured.

  In the power amplifying apparatus 100, data is exchanged by analog signals on the sending side of the D / A converters 21a, 21b and A / D converters 37a, 37b, while data is exchanged by digital signals on the input side. Has been made.

  In the power amplifying apparatus 100, the distortion power calculation unit 41, the process determination unit 43, the gain setting unit 45, the gain adjustment unit 47, and the predistortion compensation unit 13 constitute the distortion compensation device of the present invention. . Of course, the power calculator 15, the distortion compensation table 17, and the compensation coefficient calculator 19, which are other members, can be grasped as a part of the distortion compensation apparatus. The distortion compensation device is a device that compensates for distortion that may occur in the transmission signal in accordance with the distortion characteristics of the amplifier 27 in the power amplification device 100.

  The delay units 11a, 11b, 11c, and 11d respectively delay the in-phase component I and the quadrature component Q of a transmission baseband signal (information signal such as audio, video, and other digital data) sent from the transmission source by a predetermined time. Is. The delay unit calculates the power from the transmission baseband signal, and delays the transmission signal by the amount of the delay time when the table of the distortion compensation coefficient is drawn to adjust the timing.

  The power calculator 15 calculates the power of the transmission signal based on the in-phase component I and the quadrature component Q of the transmission baseband signal. The transmission power is obtained by the following formula.

  The transmission power of the transmission baseband signal calculated by the power calculation unit 15 is input to the distortion compensation table 17. The distortion compensation table 17 draws a table of distortion compensation coefficients corresponding to the input transmission power. This table lookup can be performed in the same manner even when a transmission amplitude obtained by taking √ of transmission power is used. This transmission amplitude is obtained by the following equation.

  In the distortion compensation table 17, distortion compensation coefficients are stored in the predistortion compensation unit 13 so as to be opposite to the distortion characteristics of the amplifier 27 described later. The distortion compensation coefficient is calculated in advance by the compensation coefficient calculation unit 19. The distortion compensation table 17 is obtained by associating the power calculated by the power calculator 15 with the compensation coefficient obtained from the feedback signal of the transmission signal corresponding to this power.

  The predistortion compensation unit 13 multiplies the input digital signals I and Q from the delay units 11a and 11b by the compensation coefficient stored in the above-described distortion compensation table 17 (multiplies predistortion). This distortion compensation coefficient has a characteristic opposite to the distortion characteristic of the rear amplifier 27 and is calculated in advance by a compensation coefficient calculation unit 19 described later. The gain calculated in the gain setting unit 45 described later is set in the gain adjustment unit 47, and the gain of the transmission signal is adjusted with the set gain. The predistortion unit 13 and the gain adjustment unit 47 will be described later.

  The D / A converters 21 a and 21 b convert the input digital signals I and Q subjected to the predistortion by the predistortion compensation unit 13 into analog signals I and Q. The analog signals I and Q are input to the quadrature modulation unit 23. The quadrature modulation unit 23 multiplies the input analog signals I and Q by a reference carrier wave and a signal obtained by shifting this by 90 °, and adds the multiplication results to perform orthogonal transform.

  The up-converter 25 mixes a quadrature modulation signal generated by the quadrature modulation of the quadrature modulation unit 23 and a local oscillation signal made up of a carrier wave having a frequency as a transmission wave generated by the oscillator 39 to obtain a frequency to a radio frequency. Perform conversion.

  The amplifier 27 amplifies the power of the frequency conversion signal output from the up converter 25. The amplified signal is distributed into two signals by a directional coupler (or distributor) 29, and one signal (forward side) is emitted as a radio wave by an antenna 31.

  A signal distributed without being emitted from the antenna 31 by the directional coupler 29 is used as a feedback signal. The feedback signal is used when measuring distortion power and updating distortion compensation coefficients.

  The down converter 33 down-converts a radio frequency feedback signal to an intermediate frequency band or a base band. The quadrature demodulation unit 35 extracts the in-phase component signal I_F and the quadrature component signal Q_F by performing quadrature detection. The A / D converters 37a and 37b return analog signals to digital signals.

  The digital signals I_F and Q_F described above are input to the distortion power calculation unit 41, and distortion power that is leakage power outside the transmission band is calculated. The distortion power calculation unit 41 calculates distortion power based on the input in-phase component signal I_F and quadrature component signal Q_F as feedback signals.

  FIG. 2 is a graph showing the relationship between the transmission band and the distortion power measurement band (distortion power calculation section). 2A shows a case where the transmission carrier is one carrier, and FIG. 2B shows a case where the transmission carrier is two carriers. As shown in FIG. 2A, when there is one transmission carrier, the distortion power for the adjacent band 2 · y [Hz] band is calculated except the transmission band x [Hz]. As shown in FIG. 2B, when there are two transmission carriers, the distortion power for the adjacent band 2 · y [Hz] band is calculated except the transmission band 2 · x [Hz]. Therefore, for n carriers, the distortion power for the 2 · y [Hz] band is calculated excluding the transmission band n · x [Hz] (x and y can be set arbitrarily).

  Two examples are given as methods of calculating the distortion power. FIG. 3A conceptually shows a method of calculating power by extracting only a distortion power measurement band by BPF (Band Pass Filter), and FIG. 3B shows spectrum using FFT (Fast Fourier Transform). A method of calculating the power of the corresponding band after calculating the above is conceptually shown. In FIG. 3A, BEF (Band Elimination Filter) can also be used. Details of the method are introduced in JP-A Nos. 2001-203539 and 2004-64733.

  The processing determination unit 43 looks at the level of the distortion level calculated by the distortion power calculation unit 41. If the threshold is exceeded, that is, if the distortion power is large, the gain determination unit 47 of the gain setting unit 45 Activate the gain adjustment mode for gain adjustment. Under this mode, if the distortion level does not improve even if the gain is adjusted, the compensation coefficient calculation unit 19 calculates the update coefficient. When the distortion level is improved, the compensation coefficient calculation unit 19 does not calculate the update coefficient.

  The gain setting unit 45 calculates a gain and sets the calculated gain in the gain adjustment unit 47. The gain adjusting unit 47 multiplies the set gain by the transmission signal. In other words, the gain adjusting unit 47 adjusts the gain of the transmission signal.

  It is considered that there are various causes for the distortion power. However, the transmission signal accompanying a physical change such as a time change or a temperature change of the quadrature modulation unit 23, the up-converter 25, etc., which are analog signal processing parts. It is thought that the part which bears to the change of gain is large. Therefore, in the present invention, the gain setting unit 45 and the gain adjustment unit 47 that can adjust the gain are provided, and the distortion power is measured by changing the gain for the transmission signal by these portions, and the compensation is terminated when the characteristics are improved. I am going to do that.

  The compensation coefficient calculation unit 19 determines the amplitude distortion compensation coefficient so that the error between the transmission signal and the feedback signal is minimized. As a method of calculating the distortion compensation coefficient, there are a least square method, an exponentially weighted sequential least square method, and the like (see Japanese Patent Laid-Open No. 9-69733). The delay units 11c and 11d are used to adjust the delay between the transmission signal and the feedback signal.

  FIG. 4 shows a sequence chart including steps of signal transmission, feedback control, distortion compensation, and gain adjustment in the power amplifying apparatus 100 of the present embodiment. First, after the power calculator 15 calculates the power of the transmission baseband signal, the distortion compensation table 17 subtracts the distortion compensation coefficient from the calculated power (step S101). Then, the predistortion compensation unit 13 multiplies the transmission signal by the inverse distortion characteristic based on the distortion compensation coefficient (step S102). Further, the transmission signal is D / A converted and orthogonally modulated by each of the D / A converters 21a and 21b and the orthogonal modulation unit 23, and is amplified by the amplifier 27 (step S103).

  The directional coupler 29 feeds back the signal amplified by the amplifier 25, and via the down converter 33, the orthogonal demodulator 35, and the A / D converters 37a and 37b, the distortion power calculator 41 and the compensation coefficient calculator 19 (Step S104). This feedback signal is used to calculate the compensation factor when measuring distortion power and updating the compensation factor. Then, the distortion power calculation unit 41 measures the distortion power of the feedback signal (step S105). On the other hand, the signal not fed back by the directional coupler 29 is emitted as a transmission signal from the antenna 31 (step S106). This completes the transmission sequence.

  Next, the process determination unit 43 determines whether or not the distortion power measured by the distortion power calculation unit 41 is greater than a predetermined threshold (step S107). If the distortion power is smaller than the threshold value, distortion compensation is continued using the conventional distortion compensation table (step S107; NO). On the other hand, when the distortion power is larger than the threshold, the process determination unit 43 first determines that the gains of the quadrature modulation unit 23 and the up-converter 25 have changed due to aging and temperature change, and enters the gain adjustment mode (step S107; YES).

  Under the gain adjustment mode, the gain setting unit 45 sets a value obtained by changing the original gain g in the range from the lower limit value X [dB] to the upper limit value Y [dB] (step S108 to step S110). This setting is performed, for example, in a range of (original gain−x [dB] = X [dB]) to (original gain + y [dB] = Y [dB]) at a predetermined i [dB] interval (for example, 1 dB). This is performed by a loop process in which a plurality of gains are sequentially set at intervals.

  First, the gain setting unit 45 sets the lower limit value X [dB] as the gain g in the gain adjustment unit 47 (step S108). Then, the distortion power corresponding to the gain X is calculated by the distortion power calculation unit 41 by a normal method, and the distortion power is stored in the gain setting unit 45 (step S109). Thereafter, a gain (X + i) [dB] obtained by increasing X by a predetermined interval i [dB] is set in the gain adjusting unit 47 (step S110). Then, the distortion power corresponding to the set gain is measured again (step S111). Next, the gain setting unit 45 determines whether or not the gain (X + i) [dB] has reached the upper limit value Y [dB] (step S112). If the gain (X + i) [dB] has not yet reached Y [dB], A value obtained by increasing the value of i [dB] minutes ago is created (step S112; NO), and measurement and storage of distortion power are continued in the same manner.

  When the set gain reaches the upper limit value Y [dB] (step S112; YES), the gain setting unit 45 determines the minimum distortion power among the distortion power of the feedback signal measured and stored corresponding to each gain. Is set in the gain adjustment unit 47 (step S113). This completes the gain adjustment mode.

  Next, the process determination unit 43 determines whether or not the distortion power measured after gain adjustment is greater than a predetermined threshold (step S114). When it is smaller than the threshold value (step S114; NO), distortion compensation by normal table lookup is continued (however, the gain is after gain adjustment). When the distortion power after gain adjustment is larger than the threshold value, the table update mode is entered (step S114; YES). The compensation coefficient calculation unit 19 newly calculates a distortion compensation coefficient (step S115), and the compensation coefficient calculation unit 19 uses the newly calculated distortion compensation coefficient (updated distortion compensation coefficient) to obtain a distortion compensation table 17. Is updated (step S116). Thereafter, distortion compensation is performed based on the updated table (return to step S101).

  In the present embodiment, the necessity of gain adjustment is determined (gain adjustment mode) in preference to the compensation coefficient update (table update mode) by the compensation coefficient calculation unit. It is considered that the increase in distortion power is largely due to a change in the gain of the transmission signal caused by a physical change such as a time change and a temperature change of the quadrature modulation unit 23 and the up-converter 25 that are analog signal processing parts. Therefore, if the distortion power can be improved by activating the gain adjustment mode, the distortion compensation table 17 need not be updated (table update mode) as a result, and the processing amount and power consumption can be reduced. .

  The distortion compensation control in the present invention can be regarded as compensation control only for gain adjustment, excluding the update of the distortion compensation coefficient in the compensation coefficient calculation unit 19 and the distortion compensation table 17. In the case of only gain adjustment, the compensation coefficient calculation unit 19 and the distortion compensation table 17 are not essential requirements for the distortion compensation apparatus.

(Second Embodiment)
FIG. 5 shows a power amplifying apparatus 101 according to the second embodiment of the present invention. In this embodiment, unlike the power amplifying apparatus 100 of FIG. 1, instead of the quadrature modulation unit 23 and the quadrature demodulation unit 35, a digital quadrature modulation unit 51 and a digital quadrature demodulation unit 53 are respectively connected to the preceding stage of the D / A converter 21. The A / D converter 37 is provided at a subsequent stage.

(Third embodiment)
FIG. 6 shows a power amplifying apparatus 102 according to the third embodiment of the present invention. In this embodiment, the input transmission signal is an analog signal. Unlike the power amplifying apparatus 100 of FIG. 1, an attenuator setting unit 57, a D / A converter 21 d, and a variable attenuator 55 are provided instead of the gain setting unit 45 and the gain adjustment unit 47. Further, an A / D converter 37 c is provided at the front stage of the power calculation unit 15, and a D / A converter 21 c is provided at the rear stage of the distortion compensation table 17.

  In the present embodiment, an appropriate attenuation amount is calculated by the attenuator setting unit 57, and the calculated attenuation amount is set in the variable attenuator 55. The variable attenuator 55 adjusts the gain of the transmission signal with the set attenuation amount. However, since the adjustment of the attenuation amount is considered to be included in the gain adjustment, the attenuator setting unit 57 and the variable attenuator 55 are special forms (for analog use) of the gain setting unit 45 and the gain adjustment unit 47. In other words, it can be considered to be included in the gain setting unit 45 and the gain adjustment unit 47.

(Fourth embodiment)
FIG. 7 shows a power amplifying apparatus 103 according to the fourth embodiment of the present invention. In the power amplifying apparatus 103, unlike the power amplifying apparatus 100 of FIG. That is, the compensation coefficient calculation unit 19 calculates the compensation coefficient based on the feedback signal regardless of the magnitude of the distortion power. In the present embodiment, gain adjustment by the gain setting unit 45 and the gain adjustment unit 47 is performed from the obtained distortion power, but the update determination of the compensation coefficient by the processing determination unit 43 is not performed. In this case, the determination in step S114 in FIG. 4 is not performed, and the processes in steps S115 and S116 are performed directly after step S113.

  In the present invention, in the predistortion type distortion compensation device, the signal amplified by the amplifier 27 is detected as a feedback signal, the distortion power calculation unit 41 calculates the magnitude of the distortion level, and the condition determination unit 43 determines the distortion level. A condition determination is made as to whether or not the threshold value is greater. When the distortion level is high, the transmission gain is adjusted. If the distortion level does not improve even if the gain is adjusted, the compensation coefficient calculation unit 19 updates the compensation coefficient.

  That is, the distortion is improved by performing the distortion compensation by the predistortion method, but if the adaptive operation is performed unconditionally, the processing amount and the power consumption increase. Therefore, a gain adjustment unit 47 that performs gain correction corresponding to time change, temperature change, etc. of the up converter 25, the quadrature modulation unit 23, etc. is provided, and the number of times of coefficient calculation is reduced by performing processing according to the detected distortion level. It is possible to reduce the processing amount and power consumption.

  The power amplifying device of the above-described embodiment can be used as a wireless communication device, particularly as a wireless communication base station device. The radio communication base station apparatus is installed in, for example, a mobile phone base station. The wireless communication device can also be used as a wireless mobile communication device. An example of the wireless mobile communication device is a portable wireless device represented by a mobile phone.

  The distortion compensation method of the present invention can be executed by a program that causes an arithmetic processing unit such as a CPU or DSP incorporated in a processing determination unit to execute a predetermined procedure. This program is stored in the form of a memory or other recording medium provided inside or outside the distortion compensation apparatus.

  Although various embodiments of the present invention have been described above, the present invention is not limited to the matters shown in the above-described embodiments, and those skilled in the art can make modifications and applications based on the description and well-known techniques. This is also the scope of the present invention, and is included in the scope for which protection is sought.

  According to the present invention, it is possible to provide a distortion compensation apparatus and a distortion compensation method that can improve distortion basically by adjusting the gain of a transmission signal and reduce the number of coefficient calculations.

1 is a block diagram of a power amplification device according to a first embodiment of the present invention. The graph which shows a transmission band and distortion electric power calculation area. The conceptual diagram which shows the method of calculating distortion electric power. The processing sequence diagram in a power amplifier. The block diagram of the power amplification apparatus concerning the 2nd Embodiment of this invention. The block diagram of the power amplification apparatus concerning the 3rd Embodiment of this invention. The block diagram of the power amplification apparatus concerning the 4th Embodiment of this invention. The figure which shows the amplification result when there is no predistortion compensation. The figure which shows the amplification result at the time of providing a front distortion compensation part and carrying out distortion compensation. The figure which shows the concept that the phase of an antenna output signal rotates. The figure which shows the frequency spectrum when not carrying out distortion compensation.

Explanation of symbols

11a delay unit 11b delay unit 11c delay unit 11d delay unit 13 predistortion compensation unit 15 power calculation unit 17 distortion compensation table memory 19 compensation coefficient calculation unit 21a D / A converter 21b D / A converter 23 orthogonal modulation unit 25 upconverter 27 Amplifier 29 Directional coupler 31 Antenna 33 Down converter 35 Orthogonal demodulator 37a A / D converter 37a A / D converter 39 Oscillator 41 Distortion power calculation unit 43 Processing determination unit 45 Gain setting unit 47 Gain adjustment unit 51 Digital quadrature Modulator 53 Digital quadrature demodulator 55 Variable attenuator 57 Attenuator setting unit 100 Power amplifying device 101 Power amplifying device 102 Power amplifying device 103 Power amplifying device

Claims (9)

A distortion compensation device that compensates for distortion that may occur in a transmission signal in accordance with distortion characteristics of an amplifier in a wireless communication device,
An output calculation unit for calculating the power of the transmission signal;
A compensation coefficient calculation unit for calculating a compensation coefficient representing a distortion characteristic opposite to the distortion characteristic of the amplifier based on a feedback signal of the transmission signal amplified by the amplifier;
A distortion compensation table that associates and stores the power calculated in the output calculation unit and the compensation coefficient obtained from the feedback signal of the transmission signal corresponding to the power;
A predistortion unit that multiplies a transmission signal by the compensation coefficient stored in the distortion compensation table ;
A distortion power calculating unit for calculating a distortion power from the feedback signal,
A process determination unit that determines whether or not the calculated distortion power is greater than a predetermined threshold;
A gain setting unit that sets a gain to be applied to a transmission signal multiplied by a reverse distortion characteristic by the pre-distortion compensation unit when the processing determination unit determines that the distortion power is greater than the predetermined threshold;
A gain adjustment unit that multiplies the transmission signal compensated for distortion by the gain set in the gain setting unit ,
The processing determination unit determines whether or not the distortion power is greater than a predetermined threshold even after the gain is adjusted in the gain adjustment unit,
After the gain is adjusted in the gain adjustment unit, when the distortion power is larger than a predetermined threshold, the compensation coefficient calculation unit calculates a new compensation coefficient and updates the distortion compensation table with the new compensation coefficient. Compensation device. The distortion compensation apparatus according to claim 1,
When the processing determination unit determines that the distortion power is greater than the predetermined threshold, the gain setting unit sets a plurality of gains,
The gain adjusting unit multiplies each of the plurality of gains by a transmission signal,
The distortion power calculation unit calculates a plurality of distortion powers from a feedback signal of a transmission signal corresponding to each of the plurality of gains,
The said gain setting part is a distortion compensation apparatus which adjusts the gain of the said gain adjustment part so that it may become a gain corresponding to the minimum distortion power among the calculated said distortion power.   The distortion compensator according to claim 1 or 2,
  The gain adjusting unit is a distortion compensation device that performs digital amplification.   The distortion compensator according to claim 1 or 2,
  A distortion compensation apparatus, wherein the gain adjustment unit is configured by a variable attenuator.   A wireless communication apparatus including the distortion compensation apparatus according to claim 1.   A distortion compensation device according to claim 3;
  A wireless communication apparatus comprising a D / A converter, a quadrature modulation unit, an up-converter, and an amplifier connected to a subsequent stage of the gain adjustment unit.   The distortion compensation apparatus according to claim 4,
  A wireless communication device comprising: an amplifier connected to a subsequent stage of the variable attenuator.   A radio communication base station apparatus comprising the radio communication apparatus according to claim 5.   A wireless mobile communication device comprising the wireless communication device according to claim 5.

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