JP2007208684A - Transmitter having distortion compensating function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter having a distortion compensating function applying a distortion compensation to a specific signal-amplitude region largely having an effect on distortion characteristics. <P>SOLUTION: The transmitter having the distortion compensating function has an amplitude-value arithmetic section 25 for arithmetically operating an amplitude value from an input modulation signal, and a comparison arithmetic section 26 for comparing an output from the amplitude-value arithmetic section 25 and a threshold-value signal S10. The transmitter further has an address calculation section 15 for calculating an address only when the amplitude value of the input modulation signal is kept within a specified range determined by the threshold-value signal S10 in the comparison arithmetic section 26. Since a distortion is compensated only when the amplitude value of the input modulation signal is kept within the specified range determined by the threshold-value signal S10, a distortion-compensating range can be allocated only to the specified range largely having the effect on distortion characteristics. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmission apparatus with a distortion compensation function that compensates for nonlinear distortion of a power amplifier or the like in a transmission apparatus such as a wireless communication system, and more particularly, transmission with a distortion compensation function that performs distortion compensation only for a region with high nonlinear distortion. It relates to the device.

  Currently, various efforts are being made to achieve low distortion of power amplifiers. As a distortion compensation method, two methods, mainly a method using an analog circuit and a digital method using baseband signal processing, have been studied so far. In recent mobile communications, a high-speed and large-capacity data transmission rate has been demanded, and the signal band to be compensated tends to widen. Due to the widening of the signal band, it is difficult to secure a sufficient compensation frequency band with the analog distortion compensation system used so far. For this reason, a digital distortion compensation method has been actively studied.

  The digital distortion compensation system includes a system (polynomial system) in which the inverse characteristic of the nonlinear characteristic of the power amplifier is approximated by a polynomial and multiplied by the input modulation signal, and a power amplifier corresponding to the input modulation signal level in the LUT (Look Up Table). There are widely known two methods of storing the inverse characteristics of and calling this LUT as necessary. Each method has advantages and disadvantages, but it is considered that the LUT method is suitable for a power amplifier having a large nonlinearity. This is because it is difficult to represent the inverse characteristics of the power amplifier with a limited memory (approximate degree of polynomial) in the polynomial method. For this reason, it is desirable to use the LUT method for a power amplifier with high nonlinearity.

  The following methods are known as distortion compensation methods using a conventional LUT. The input signal input to the power amplifier is divided equally between the minimum value and the maximum value of the signal level. A value that is an inverse characteristic of the power amplifier for each of the divided input modulation signal levels is stored in the LUT as a distortion compensation coefficient. A signal level input to the power amplifier is detected, an LUT address corresponding to the signal level is calculated, and an inverse characteristic corresponding to the input modulation signal level is output. This is a method of obtaining a linear characteristic by canceling the non-linear characteristic by inputting the output inverse characteristic to the power amplifier. In the conventional distortion compensation method using the LUT, in order to shorten the convergence time of the distortion compensation coefficient and improve the compensation accuracy, the address generation frequency of the distortion compensation coefficient table which is an LUT storing the distortion compensation coefficient is made uniform. (For example, refer to Patent Document 1).

  FIG. 7 is a block diagram showing an overall configuration of a transmission apparatus using the conventional distortion compensation method described in Patent Document 1. In FIG. FIG. 7 shows a method for improving compensation characteristics in a transmission apparatus using a conventional distortion compensation method. The input modulation signal S1 is input to the power amplifier 2 via the multiplier 1, and the output modulation signal S2 is output from the power amplifier 2. The subtraction unit 3 subtracts a part of the output modulation signal S2 from the input modulation signal S1, calculates the distortion compensation coefficient S3 by the distortion compensation coefficient calculation unit 4 based on the difference value, and stores it in the distortion compensation coefficient table 5. To do. The address for storing the distortion compensation coefficient S3 in the distortion compensation coefficient table 5 is determined as follows. The amplitude calculation unit 6 calculates the amplitude value of the input modulation signal S1, and the amplitude appearance frequency calculation unit 7 calculates the amplitude appearance frequency of the input modulation signal S1 from the calculated amplitude value. The address calculation unit 8 determines the address of the distortion compensation coefficient table 5 according to the amplitude appearance frequency. According to the determined address, the distortion compensation coefficient S3 is stored in the distortion compensation coefficient table 5, and the data of the distortion compensation coefficient table is updated. The distortion compensation coefficient S3 updated in the multiplier 1 is multiplied by the input modulation signal S1 and input to the power amplifier 2 as a distortion compensation signal.

FIG. 8A is a diagram showing the appearance frequency of the amplitude value of the input modulation signal in the transmission apparatus using the conventional distortion compensation method described in Patent Document 1, and FIG. 6 is a diagram illustrating the frequency of appearance of addresses in a distortion compensation coefficient table in a transmission apparatus using the conventional distortion compensation scheme described in FIG. As shown in FIG. 8A, the input modulation signal S1 has a certain distribution with respect to the amplitude value. For this reason, the number of updates of the distortion compensation coefficient table in the amplitude region having a high appearance frequency is increased as it is. On the other hand, a sufficient number of updates cannot be obtained in an amplitude region with a low appearance frequency. In particular, a sufficient compensation effect cannot be obtained in the vicinity of the maximum amplitude value that greatly affects the distortion characteristics. Therefore, the amplitude appearance frequency calculation unit 7 recalculates the amplitude value of the input modulation signal S1. As shown in FIG. 8B, each step width of the amplitude value of the modulation signal is adjusted so that the frequency of appearance of addresses in the distortion compensation coefficient table corresponding to each step of the amplitude value has a uniform distribution. As shown in FIG. 8A, when the step width is adjusted to equalize the number of appearances of each step of the amplitude value, the amplitude value width increases as the amplitude appearance decreases. Thereby, the appearance frequency of each address in the distortion compensation coefficient table 5 becomes equal. As described above, the number of times the table is updated for each step of the amplitude value becomes uniform, the convergence time of the distortion compensation coefficient can be shortened, and highly accurate distortion compensation can be performed.
JP 2003-347944 A (FIGS. 1 and 2)

  However, in the conventional technique, each step width of the amplitude value is adjusted in order to make the address appearance frequency uniform. Therefore, in the modulation method in which the difference between the average value of the input modulation signal and the peak signal (hereinafter referred to as the peak factor) is large. The step width of the amplitude value in the vicinity of the maximum amplitude value that has a large influence on the distortion characteristics becomes wider. For this reason, the accuracy of the compensation coefficient is lower and the compensation amount of the distortion characteristic is smaller than in a region where the amplitude appearance frequency is high (that is, a region where the step width of the amplitude value is narrow). In addition, in order to increase the compensation amount, it is necessary to increase the storage capacity of the table, which causes a problem that the cost increases.

  Further, in the conventional technique, in the method of switching the power supply voltage of the power amplifier according to the amplitude value of the input modulation signal such as the envelope tracking method, the characteristics of two different power amplifiers are close to the amplitude value for switching the power supply voltage. On the other hand, when the amplitude region for calculating the distortion compensation coefficient is the same, the operation for compensating the two gain characteristics with one compensation coefficient is not possible, and a sufficient distortion compensation effect cannot be obtained. These are the same in systems other than the envelope tracking system in which the characteristics of the power amplifier are changed by switching control signals, power supplies, and the like.

  The present invention solves such a conventional problem, and an object of the present invention is to provide a transmission device with a distortion compensation function in which distortion compensation is applied to a specific signal amplitude region that greatly affects distortion characteristics. .

  In order to solve the above-described conventional problems, a transmission device with a distortion compensation function according to the present invention includes an amplitude value calculation unit that calculates an amplitude value from an input modulation signal, and a comparison calculation unit that compares an output of the amplitude value calculation unit with a threshold value An input modulation signal determination unit comprising: an address calculation unit that calculates an address only when an amplitude value of the input modulation signal is within a predetermined range determined by the threshold in the input modulation signal determination unit; Distortion compensation is performed only when the amplitude value of the input modulation signal is within a predetermined range determined by the threshold value.

  With this configuration, it is possible to assign the distortion compensation range only to a predetermined range that greatly affects the distortion characteristics.

  Further, the transmission device with a distortion compensation function of the present invention, the address calculation unit, the amplitude value for switching the power supply voltage of the power amplifier in conjunction with the power supply voltage switching signal controlled according to the amplitude value of the input modulation signal, By calculating the address so as to substantially match the amplitude value for switching the address of the distortion compensation coefficient table, two different gain characteristics do not substantially exist in the same address area.

  The transmission device with a distortion compensation function according to the present invention compares an error amplitude value calculation unit that calculates an error amplitude value from an output of the error signal calculation unit, an output of the error amplitude value calculation unit, and a second threshold value. In the error signal determination unit composed of a second comparison calculation unit and the second comparison calculation unit, when the output of the error signal calculation unit is larger than the second threshold, the value of the parameter signal is increased, When the error amplitude value is larger than the second threshold value by providing a parameter signal calculation unit that operates to reduce the value of the parameter signal when the output of the error signal calculation unit is smaller than the second threshold value. The compensation amount is increased, and when the error amplitude value is smaller than the second threshold value, the compensation amount is decreased.

  According to the transmission device with a distortion compensation function of the present invention, it is possible to increase the distortion compensation accuracy without increasing the storage capacity of the table for storing the distortion compensation coefficient.

  Further, according to the transmission device with a distortion compensation function of the present invention, it is possible to improve the degradation of distortion compensation accuracy when the power supply voltage of the power amplifier is switched.

  Moreover, according to the transmission apparatus with a distortion compensation function of the present invention, it is possible to improve the convergence speed and accuracy of distortion compensation.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
1 and 2 are diagrams for explaining a transmission device with a distortion compensation function according to Embodiment 1 of the present invention. FIG. 1 is a block diagram showing an overall configuration of a transmission apparatus with a distortion compensation function in the first embodiment. In FIG. 1, the transmission device with a distortion compensation function includes a power amplifier 10, a distortion compensation unit 11, and a power source 19. The distortion compensation unit 11 includes an error signal calculation unit 12, a distortion compensation coefficient calculation unit 13, an input modulation signal determination unit 14, an address calculation unit 15, a distortion compensation coefficient table 16, a second complex conjugate calculation unit 17, and a third multiplication. Part 18. The error signal calculation unit 12 includes a gain circuit 20 and a subtraction unit 21. The distortion compensation coefficient calculation unit 13 includes a first complex conjugate calculation unit 22, a first multiplier 23, and a second multiplier 24. The input modulation signal determination unit 14 includes an amplitude value calculation unit 25 and a comparison calculation unit 26.

  In Embodiment 1 of the present invention, the input modulation signal X is input to the power amplifier 10 via the third multiplier 18. Further, the input modulation signal X is input to the amplitude value calculation unit 14 to calculate the amplitude value, and the comparison calculation unit 26 compares it with the threshold signal S10. At this time, if the amplitude value of the input modulation signal X is larger than the predetermined range determined by the threshold signal S10, the address calculation unit 15 calculates an address value for updating the value of the distortion compensation coefficient table 16. Further, when the amplitude value of the input modulation signal X is smaller than a predetermined range determined by the threshold signal S10, a series of calculations for calculating an address value and a distortion compensation coefficient are not performed.

  As a method for calculating a distortion compensation coefficient, a method using a general RMS (Root Mean Square) method or the like can be used, and a distortion compensation method using the RMS method will be described below. A part Y1 of the output modulation signal Y of the power amplifier 10 is taken out and divided by the gain G of the power amplifier 10 by the gain circuit 20 to obtain an output signal S11 (= Y1 / G). The subtractor 20 subtracts the output signal S11 of the gain circuit 20 from the input modulation signal X to obtain an error signal e (= X−Y1 / G). The first complex conjugate calculation unit 22 sets the error signal e to the complex conjugate value conj (e). Further, the first multiplier 23 multiplies the parameter signal u that determines the compensation amount of the power amplifier 10 by the complex conjugate value conj (e) of the error signal e to obtain u × conj (e). Further, the second multiplier 24 multiplies the output of the first multiplier 23 and the input modulation signal X. Then, the multiplication output pd_lut (= X × u × conj (e)) of the second multiplication unit 24 is stored in the distortion compensation coefficient table 16. The distortion compensation coefficient table 16 sequentially updates the table value based on the address value calculated by the address calculation unit 15 based on the amplitude value of the input modulation signal X. At this time, the comparison calculation unit 26 compares the amplitude value calculated by the amplitude value calculation unit 25 with the threshold signal S10. The address calculation unit 15 calculates an address value for updating the value of the distortion compensation coefficient table 16 when the amplitude value of the input modulation signal X is larger than a predetermined range determined by the threshold signal S10. When the amplitude value of the input modulation signal X is smaller than the predetermined range determined by the threshold signal S10, the address value is not calculated and the table value is not updated. In the second complex conjugate calculation unit 17, the distortion compensation coefficient pd_lut, which is the output of the distortion compensation coefficient table 16, is set as a complex conjugate value conj (pd_lut). The third multiplication unit 18 multiplies the complex conjugate value conj (pd_lut) and the input modulation signal X and inputs them to the power amplifier 10 to perform distortion compensation.

  Next, the calculated amplitude region of the distortion compensation coefficient in the gain vs. input modulation signal characteristic of the power amplifier 10 will be described with reference to FIGS. 2 (a) and 2 (b). 2A is a gain characteristic diagram of the power amplifier 10 showing the calculation range of the conventional distortion compensation coefficient, and FIG. 2B is a power amplifier showing the calculation range of the distortion compensation coefficient in the first embodiment of the present invention. FIG. FIG. 2A shows a case where the compensation coefficient is calculated over the entire amplitude region of the input modulation signal of the power amplifier 10. The power amplifier 10 has a substantially linear gain characteristic in a region where the amplitude value of the input modulation signal is small, and distortion of the output modulation signal is small. On the other hand, it is the region where the gain characteristic is nonlinear that has a great influence on the distortion characteristic of the power amplifier 10. For this reason, in the distortion compensation of the power amplifier 10, it is not necessary to calculate a compensation coefficient over the entire amplitude region of the input modulation signal, and the distortion compensation coefficient is calculated for the region where the input amplitude of the power amplifier 10 is small. By making it correspond to the vicinity of a region with high nonlinearity, a more accurate compensation coefficient can be obtained. FIG. 2B shows a case where the calculation range of the distortion compensation coefficient is made to correspond to a region with high nonlinearity in the gain characteristic. Here, the amplitude value at which the calculation of the distortion compensation coefficient is started is a value determined by the threshold signal S10 described above. It is shown that by calculating the compensation coefficient only in the region with high nonlinearity, a more accurate compensation coefficient can be obtained even with the same table resolution.

According to the first embodiment of the present invention, there is provided determination means for determining that the amplitude value of the input modulation signal is within a predetermined range determined by the threshold value, and the distortion compensation operation is performed on the input modulation signal within the predetermined range By implementing the above, it becomes possible to assign the compensation range of the distortion compensation coefficient table only to the region that greatly affects the distortion characteristics, and the distortion compensation accuracy can be improved even with a table having a small storage capacity.
In the first embodiment of the present invention, the amplitude value calculation unit 25 calculates the amplitude value of the input modulation signal and compares it with the threshold signal S10. However, a configuration using a power value instead of the amplitude value is also possible. good.

In the first embodiment of the present invention, the distortion compensation method using the RMS method has been described. However, a configuration using another method may be used.
(Embodiment 2)
3 to 5 are diagrams for explaining a transmission device with a distortion compensation function according to Embodiment 2 of the present invention. FIG. 3 is a block diagram showing an overall configuration of a transmission apparatus with a distortion compensation function according to Embodiment 2 of the present invention. In FIG. 3, the transmitter with distortion compensation function according to the second embodiment of the present invention is configured to switch the power supply voltage of the power amplifier 10 using the power supply voltage switching signal S30, and according to the magnitude of the amplitude value of the input modulation signal. Thus, the power supply voltage is controlled by the power supply voltage switching signal S30 so as to correspond to a system such as an envelope tracking system.

  The configuration of the second embodiment of the present invention is different from the first embodiment of the present invention shown in FIG. 1 in that the address calculation unit 15 is the second address calculation unit 30 and the power source 19 is the second power source 31. The configuration is replaced with. The second address calculation unit 30 is coupled with the power supply voltage switching signal S30 controlled according to the amplitude value of the input modulation signal, and the amplitude value for switching the power supply voltage and the amplitude value for switching the address of the distortion compensation coefficient table. The addresses are calculated so as to substantially match. The second power supply 31 is characterized in that the power supply voltage of the power amplifier 10 is switched by a power supply voltage switching signal S30 controlled according to the amplitude value of the input modulation signal. In the present invention, the number of power supply voltages to be switched is two, but it is also possible to switch to more voltages.

  Next, the operating characteristics of the transmission apparatus with a distortion compensation function according to Embodiment 2 of the present invention will be described with reference to FIG. 4A is a gain characteristic diagram of the power amplifier showing the step width of the distortion compensation coefficient table by the conventional address calculation process, and FIG. 4B is the distortion in the address calculation process according to the second embodiment of the present invention. It is a gain characteristic figure of a power amplifier which showed the step width of the compensation coefficient table. FIG. 4A shows gain characteristics when the power supply voltage of the power amplifier 10 is switched by the power supply voltage switching signal S30 in accordance with the amplitude value of the input modulation signal. The characteristics are low when the power supply voltage is low (power supply voltage 1 in the figure) and high when the power supply voltage is high (power supply voltage 2 in the figure). In the method of switching the power supply voltage of the power amplifier according to the amplitude value of the input modulation signal, such as the envelope tracking method, near the amplitude value of the input modulation signal where the characteristics of the power amplifier 10 such as power efficiency and distortion characteristics are the best. Switch the power supply voltage. Assuming that the switching point Q is the amplitude value at which the characteristic of the power amplifier 10 is best, the gain characteristic changes discontinuously by switching the power supply voltage of the power amplifier 10 from the power supply voltage 1 to the power supply voltage 2 at the switching point Q. As shown in FIG. 4A, at the switching point Q, when two different gain characteristics exist in the same address region for the power supply voltage 1 and the power supply voltage 2, two gains are obtained with one compensation coefficient. Since the operation compensates for the characteristics, a sufficient distortion compensation effect cannot be obtained. Although not shown, a sufficient distortion compensation effect cannot be obtained for the phase characteristics as well.

  On the other hand, FIG. 4B shows the amplitude value of the input modulation signal that is substantially the same as the switching of the power supply voltage of the power amplifier 10 and the switching of the address of the distortion compensation coefficient table by the address calculation process of the second embodiment of the present invention. This is performed at (switching point Q) so that two different gain characteristics do not substantially exist in the same address area.

Here, regarding the address calculation processing according to the second embodiment of the present invention shown in FIG. 4B, the operation of calculating the address area with reference to the switching point Q will be described with reference to FIGS. FIG. 5A is a process flow diagram illustrating the address calculation process in the second address calculation unit 30 according to the second embodiment of the present invention. The maximum value of the amplitude that can be input to the power amplifier 10 is the maximum input amplitude Vmax, the amplitude value that switches the power supply voltage by the power supply voltage switching signal S30 is the power supply voltage switching amplitude Vq, the minimum address value of the distortion compensation coefficient table 16 is 1, and the maximum address When the value is the maximum address value Nmax and the power supply voltage switching signal S30 is the power supply voltage switching address value Q, the switching amplitude value Vp of each address in the distortion compensation coefficient table 16 is determined as follows. Is done.
First, an amplitude value difference B (= Vmax−Vq) is calculated from the input maximum amplitude Vmax and the power supply voltage switching amplitude Vq (processing 1). Next, the number of addresses C (= Nmax−Q) existing in the interval of the amplitude difference B is calculated from the maximum address value Nmax and the power supply voltage switching address value Q in the distortion compensation coefficient table 16 (processing 2). Further, a step width R per address is calculated by performing an operation of dividing the amplitude value difference B by the number of addresses C (processing 3). Then, an amplitude range (= R × Nmax) for performing distortion compensation is obtained from the step width R and the maximum address value Nmax, and an amplitude lower limit value Vmin (= Vmax−R × Nmax) for distortion compensation is obtained by subtracting from the input maximum amplitude Vmax. calculate. Next, the switching amplitude value Vp at the address value N is calculated. From the address value N and the step width R, an amplitude range Vn (= N × R) from the address value 1 to N is obtained. Then, the switching amplitude value Vp at the address value N is determined by adding the distortion compensation amplitude lower limit value Vmin and the address value 1 to N amplitude range Vn (process 4).

Vp = (Vmax−R × Nmax) + (N × R) = Vmin + Vn
However, N ≦ Nmax
Here, when the address value N is Q (address value for switching the power supply voltage), the power supply voltage switching amplitude Vq and the amplitude value Vp for switching the address of the distortion compensation coefficient table can be made the same.
FIG. 5B shows the calculation of the switching amplitude Vp at the address rank N when the maximum input amplitude Vmax = 5 V, the power supply voltage switching amplitude Vq = 4 V, the maximum address value Nmax = 100, and the power supply voltage switching address value Q = 60. An example is shown. As shown in FIG. 5B, the step width R corresponding to one address is 0.025V, and the range for calculating the distortion compensation coefficient is 2.5 to 5V. In the power supply voltage switching address value Q (N = 60), the amplitude value Vp at which the address is switched is 4 V, which is the same voltage as the power supply voltage switching amplitude Vq.

  According to the second embodiment of the present invention, the amplitude value for switching the power supply voltage of the power amplifier 10 in conjunction with the power supply voltage switching signal S30 controlled according to the amplitude value of the input modulation signal, and the distortion compensation coefficient table By providing the second address calculation unit 30 for calculating the address so as to substantially match the amplitude value for switching the address, two different gain characteristics do not substantially exist in the same address region, and the power supply of the power amplifier Even when the characteristics of the power amplifier change discontinuously by switching the voltage, the distortion compensation accuracy can be improved.

In addition to the envelope tracking method, the device using a plurality of characteristics of the power amplifier can be implemented in the Doherty method.
(Embodiment 3)
Next, Embodiment 3 of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing a configuration of a transmission apparatus with a distortion compensation function according to Embodiment 3 of the present invention. In the third embodiment, in addition to the configuration of the first embodiment of the present invention, an error signal determination unit 42 and a parameter signal calculation unit 43 having an error amplitude value calculation unit 40 and a second comparison calculation unit 41 are added. Configured. In the first embodiment already described, the parameter signal u for determining the compensation amount is calculated as a fixed value. However, in the third embodiment of the present invention, a part Y1 of the output modulation signal Y of the power amplifier 10 and the input are input. It is characterized in that the variable parameter signal v is changed depending on the magnitude of an error signal e indicating an error from the modulation signal X. The same components as those in the first embodiment of the present invention are denoted by the same reference numerals.
The variable parameter signal v is calculated as follows. An error amplitude value of the error signal e is obtained by inputting the output of the error signal calculation unit 12 to the error amplitude value calculation unit 40. The second comparison calculation unit 41 compares the output of the error amplitude value calculation unit 40 with the second threshold signal S20. The parameter signal calculation unit 43 calculates the value so that the variable parameter signal v is increased when the amplitude value of the error signal e is larger than the second threshold signal S20, and is decreased when it is less than or equal to the threshold. To do.

  That is, according to the third embodiment of the present invention, the error signal determination unit 42 that compares the error signal e and the threshold signal S20, and the variable parameter signal v is increased when the value of the error signal e is larger than the threshold signal S20. When the error signal e is larger than the threshold signal S20, a convergence speed is obtained by providing a parameter signal calculation unit 43 that reduces the variable parameter signal v when the threshold signal S40 is lower than the threshold signal S20. When the error signal e is smaller than the threshold signal S20, the amount of compensation is reduced, so that the linear accuracy can be improved.

  The transmission device with a distortion compensation function according to the present invention can increase the distortion compensation accuracy without increasing the storage capacity of the table for storing the distortion compensation coefficient, so that it is generated with a high-speed, wide-band transmission signal having a large peak factor. It is useful as a transmitter with a distortion compensation function that compensates for distortion.

1 is a block diagram showing an overall configuration of a transmission device with a distortion compensation function according to Embodiment 1 of the present invention. (A) Gain characteristic diagram of power amplifier 10 showing a calculation range of a conventional distortion compensation coefficient (b) Gain characteristic diagram of power amplifier 10 showing a calculation range of a distortion compensation coefficient in the first embodiment of the present invention The block diagram which shows the whole structure of the transmitter with a distortion compensation function in Embodiment 2 of this invention. (A) Gain characteristic diagram of power amplifier 10 showing step width of distortion compensation coefficient table by conventional address calculation processing (b) Step width of distortion compensation coefficient table in address calculation processing of embodiment 2 of the present invention Gain characteristics diagram of power amplifier 10 (A) Process flow diagram for explaining the address calculation process in the second address calculation unit 30 according to the second embodiment of the present invention (b) Calculation example of the switching amplitude Vp of the address rank N The block diagram which shows the whole structure of the distortion compensation transmission apparatus in Embodiment 3 of this invention. The block diagram which shows the whole structure of the transmitter which used the conventional distortion compensation system (A) The figure showing the appearance frequency of the amplitude value of the input modulation signal in the transmission device using the conventional distortion compensation method. (B) The appearance frequency of the address of the distortion compensation coefficient table in the transmission device using the conventional distortion compensation method. Figure representing

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Power amplifier 11 Distortion compensation part 12 Error signal calculation part 13 Distortion compensation coefficient calculation part 14 Input modulation signal determination part 15 Address calculation part 16 Distortion compensation coefficient table 17 2nd complex conjugate calculation part 18 3rd multiplication part 19 Power supply 20 Gain circuit 21 Subtraction unit 22 First complex conjugate calculation unit 23 First multiplication unit 24 Second multiplication unit 25 Amplitude value calculation unit 26 Comparison calculation unit 30 Second address calculation unit 31 Second power supply 40 Error amplitude value Calculation unit 41 Second comparison calculation unit 42 Error signal determination unit 43 Parameter signal calculation unit

Claims (3)

A power amplifier for amplifying the input modulation signal;
A transmission device with a distortion compensation function comprising a distortion compensation unit that multiplies the input modulation signal by a distortion compensation coefficient to compensate for nonlinear distortion of the power amplifier,
The distortion compensation unit
An error signal calculation unit that generates an error signal that is an error between the output from the power amplifier and the input modulation signal;
A first complex conjugate computing unit that performs complex conjugate computation on the output of the error signal computing unit; a first that multiplies the output of the first complex conjugate computing unit and a parameter signal that determines the amount of change in the distortion compensation coefficient; A distortion compensation coefficient calculation unit including a multiplication unit, a second multiplication unit that multiplies the output of the first multiplication unit and the input modulation signal;
An amplitude value calculation unit that calculates an amplitude value from the input modulation signal, an input modulation signal determination unit that includes a comparison calculation unit that compares an output of the amplitude value calculation unit and a threshold value;
An address calculation unit that calculates an address only when an amplitude value of the input modulation signal is within a predetermined range determined by the threshold value in the input modulation signal determination unit;
A distortion compensation coefficient table that holds the output of the distortion compensation coefficient calculator at the address calculated by the address calculator;
A second complex conjugate calculation unit for calculating complex conjugate of the output from the distortion compensation coefficient table;
A third multiplier that multiplies the output from the second complex conjugate calculator and the input modulation signal;
The transmission apparatus with a distortion compensation function, wherein the distortion compensation unit performs distortion compensation only when an amplitude value of the input modulation signal is within a predetermined range determined by the threshold value. A power supply for switching the power supply voltage of the power amplifier by a power supply voltage switching signal controlled according to the amplitude value of the input modulation signal;
The address calculating unit calculates an address so that an amplitude value for switching a power supply voltage and an amplitude value for switching an address of the distortion compensation coefficient table are substantially matched with the power supply voltage switching signal. The transmission apparatus with a distortion compensation function according to claim 1. An error amplitude determination unit that calculates an error amplitude value from an output of the error signal calculation unit, an error signal determination unit that includes a second comparison calculation unit that compares the output of the error amplitude value calculation unit and a second threshold value; ,
In the error signal determination unit, when the output of the error signal calculation unit is larger than the second threshold, the value of the parameter signal is increased, and when the output of the error signal calculation unit is smaller than the second threshold The distortion compensation transmission apparatus according to claim 1, further comprising: a parameter signal calculation unit that operates so as to reduce a value of the parameter signal.

Images