JP5509455B2 - Distortion compensation device - Google Patents

Description

  The present invention relates to a distortion compensation apparatus, and more particularly to a distortion compensation apparatus that effectively performs distortion compensation.

  For example, power amplifiers are required to have high power efficiency and low nonlinear distortion, which are contradictory characteristics. In general, the input / output characteristics of a power amplifier are linear in a region where the input level is low, but become nonlinear when a certain input level is exceeded, and the output power eventually saturates. Usually, in order to improve the power efficiency of the power amplifier, since it is used at an operating point close to the saturation point, nonlinear distortion occurs due to the nonlinearity of the amplifier.

  In the W-CDMA (Wideband-Code Division Multiple Access) method and the OFDMA (Orthogonal Frequency Division Multiple Access) method, the ratio between the average power and the maximum power is large, and therefore it is necessary to be linear in a wide input power range. As one technique for compensating for non-linear distortion, a pre-distortion (PD) system is used. The PD system is a system that compensates for nonlinear characteristics by giving an inverse characteristic of the nonlinear characteristics to an input signal of an amplifier in advance. In particular, a digital pre-distortion (DPD) method that realizes a PD method by digital signal processing is currently the mainstream because it consumes little power.

As amplifier nonlinear characteristics, there are generally AM / AM characteristics (amplitude) and AM / PM characteristics (phase) using the amplitude of the input signal as an index, and distortion due to the memory effect occurs in the amplifier.
As an example, each distortion or a combination of two or more distortions uses the amplitude value of the input signal as a reference argument (address) and a value corresponding to the amplitude value and the inverse characteristic of the nonlinear characteristic of the amplifier that is the distortion compensation target. Compensation is performed using a distortion compensation table that stores (stores) (for example, control values) in association with each other.

FIG. 7 shows a configuration example of a distortion compensator to which the perturbation method is applied.
The distortion compensation apparatus of this example is provided in, for example, a wireless transmitter, and inputs and processes a signal to be transmitted.
The distortion compensation apparatus of this example includes a distortion compensation unit (for example, a digital predistorter) 101, a power amplification unit 102, an FFT (Fast Fourier Transform) calculation unit 111, a distortion power detection unit 112, a coefficient perturbation unit 113, distortion compensation. A table calculation unit 114 is provided.
Information on the distortion compensation table is stored in the memory of the distortion compensation unit 101 (or the distortion compensation table calculation unit 114).

  In the distortion compensation apparatus of this example, the distortion compensation unit 101 generates distortion (predistortion distortion) for the input signal (transmission signal) based on the content of the distortion compensation table, and the power amplification unit 102 amplifies the signal. Output. Also, a part of the output signal from the power amplification unit 102 is input as a feedback signal to the FFT calculation unit 111, the FFT calculation unit 111 performs FFT processing on the input signal, and the distortion power detection unit converts power of a predetermined distortion from the signal. 112, the coefficient perturbation unit 113 performs coefficient perturbation processing based on the detection result, and the distortion compensation table calculation unit 114 calculates and updates the content of the distortion compensation table based on the processing.

As an example, a memory distortion compensation process for compensating for distortion power due to the memory effect will be described.
In this case, the distortion power detection unit 112 detects the distortion power due to the memory effect as the predetermined distortion power, and as a specific example, detects distortion power outside a preset signal band so that it can be monitored. .
Here, it is assumed that the content of the distortion compensation table is expressed using (Equation 1). In (Expression 1), for example, y represents a control value (or the amount of distortion itself) for generating distortion, x represents an input signal level (for example, amplitude level), and a, b, c Are coefficients.

  The coefficient perturbation unit 113 is configured to reduce the distortion power detected by the distortion power detection unit 112 so that the x-square coefficient a, the x-fourth coefficient b, and the x-sixth coefficient in (Expression 1). c is varied. Thus, in the perturbation method, the distortion power is converged to the minimum by trial and error while controlling the contents of the distortion compensation table.

JP 2009-111958 A International Publication No. 2006/087864 Pamphlet

However, the distortion compensator as shown in FIG. 7 has the following problems (Problem 1) to (Problem 4).
(Problem 1) In the perturbation method, since the previous distortion power and the current distortion power are compared and the coefficients a, b, and c in (Equation 1) are varied, it takes time to converge the distortion power. .
(Problem 2) Since distortion power is compared by varying the coefficients a, b, and c in (Equation 1) each time, some fluctuations occur in the spectrum of the input signal (transmission signal).

(Problem 3) In order to measure distortion power in the frequency domain for the carrier signal included in the input signal (transmission signal), accurate frequency information of the carrier signal is required from a higher-level device (which may be any device) Further, it is necessary to change the position for monitoring the distortion power depending on the setting state of the carrier signal.
(Problem 4) In order to compare the previous distortion power with the current distortion power, it is necessary to make the output power (transmission power) of the section to be compared (for example, the section of the distortion compensation table address) constant, Special measures are required for burst waves.

The present invention has been made in view of such a conventional situation, and an object thereof is to provide a distortion compensation apparatus capable of effectively performing distortion compensation.
As a specific example, in the distortion compensation apparatus according to an embodiment of the present invention, the distortion compensation table is corrected from errors related to the amplitude information and phase information of the input signal (transmission signal) and the feedback signal. ) To (Problem 4), that is, the time until the distortion power is converged is reduced, the fluctuation of the spectrum of the input signal (transmission signal) is eliminated, and the frequency information of the carrier signal and special measures against the burst wave Is unnecessary.

In order to achieve the above object, in the present invention, a distortion compensator that compensates for distortion generated by an amplifier that amplifies an input signal by a predistortion system is configured as follows.
That is, the coefficient storage means stores a distortion compensation coefficient for predistorting the input signal corresponding to each address at each address. Error detection means detects information relating to an error between the input signal and the signal output from the amplifier. The representative acquisition unit acquires a distortion compensation coefficient at a predetermined plurality of representative addresses based on the information about the error detected by the error detection unit. In this case, the representative acquisition unit relates to an error for acquiring the distortion compensation coefficient. For representative addresses whose information is insufficient based on a predetermined condition, zero-order extrapolation is performed using distortion compensation coefficients acquired for other representative addresses. The updating unit updates the storage contents of the coefficient storage unit based on the distortion compensation coefficient at the representative address acquired by the representative acquisition unit.
Therefore, distortion compensation can be performed effectively. In particular, an appropriate distortion compensation coefficient can be set by obtaining a distortion compensation coefficient using 0th-order extrapolation for a portion where information regarding an error for obtaining the distortion compensation coefficient is insufficient.

Here, in the coefficient storage means (for example, memory), as the correspondence between the address and the signal, for example, the correspondence between the signal level (for example, amplitude or power value) and the address can be used.
Further, as the distortion compensation coefficient, various values may be used depending on, for example, a configuration method for executing distortion compensation.

As the error, for example, an amplitude error or a phase error can be used.
Also, various predetermined representative addresses may be used. For example, the addresses are preset in the apparatus, and as an example, the address range of the coefficient storage means is divided into a predetermined plurality. One representative address can be set for each section.

  Various methods may be used as a technique for obtaining a distortion compensation coefficient at a representative address. As an example, information relating to an error is averaged (may be cumulative addition) for each address of coefficient storage means. And averaging (may be cumulative addition, etc.) the averaging (may be cumulative addition) included in each of the plurality of sections provided in the address range of the coefficient storage means, It is possible to use a technique in which a distortion compensation coefficient is obtained by using and a distortion compensation coefficient is associated with a representative address (here, one address for each section) provided in each of the plurality of sections. it can.

  Various methods may be used as a method for determining a representative address for which information regarding an error for obtaining a distortion compensation coefficient is insufficient based on a predetermined condition. For example, a distortion compensation coefficient may be used. Using a condition that is determined to be insufficient when there is no information about an error for acquiring the address, or one or a plurality of predetermined representative addresses from the lower level such as the amplitude of the input signal For example, a condition that is determined to be insufficient (for example, due to a large variation in error) can be used, and two or more conditions can also be used in combination.

In addition, various representative addresses used when performing zero-order extrapolation to obtain a distortion compensation coefficient for a certain representative address may be used. For example, a distortion compensation coefficient is effective. And the closest one (for example, the one having the closest level such as the amplitude of the input signal) can be used.
Various modes may be used for updating the storage contents of the coefficient storage unit based on the distortion compensation coefficient at the representative address. For example, the distortion compensation coefficient at the representative address is used. It is possible to use a mode in which distortion compensation coefficients at other addresses are obtained and updated by performing interpolation (for example, interpolation only, or interpolation and extrapolation).

  As described above, the distortion compensation apparatus according to the present invention can effectively perform distortion compensation.

It is a figure which shows the structural example of the distortion compensation apparatus which concerns on one Example of this invention. It is a figure which shows the flowchart of the process which calculates the content of the distortion compensation table by calculating the error of an input signal (transmission signal) and a feedback signal. It is a figure which shows notionally an example of the calculation method of an accumulation error. It is a figure which shows an example of the relationship between an area and the address of a distortion compensation table. (A), (b) is a figure which shows an example of the mode of the 0th-order extrapolation in the area where the sample number (data number) of an error is zero. (A), (b) is a figure which shows an example of the mode of the 0th-order extrapolation of the value of the distortion compensation coefficient of the 1st representative point in the area 1. FIG. It is a figure which shows the structural example of the distortion compensation apparatus using the perturbation method.

Embodiments according to the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration example of a distortion compensation apparatus (a distortion compensation apparatus to which a waveform comparison method is applied) according to an embodiment of the present invention.
The distortion compensation apparatus of this example is provided in, for example, a wireless transmitter, and inputs and processes a signal to be transmitted.
Further, the distortion compensation apparatus of this example compensates for distortion due to the memory effect of the power amplifier (in this example, the power amplification unit 2) as a distortion compensation target. However, as another configuration example, AM / AM characteristics (amplitude) It is also possible to compensate for distortion caused by, distortion caused by AM / PM characteristics (phase), and combinations of two or more distortions.

The distortion compensation apparatus of this example includes a distortion compensation unit (for example, a digital predistorter) 1, a power amplification unit 2 including a power amplifier, a delay unit 11, a transmission signal / feedback signal error calculation unit 12, and a distortion compensation coefficient. A calculation unit 13 and a distortion compensation table calculation unit 14 are provided.
Information on the distortion compensation table is stored in the memory of the distortion compensation unit 1 (or the distortion compensation table calculation unit 14 or the like).

An example of the operation performed in the distortion compensation apparatus of this example will be shown.
An input signal (transmission signal) is input to the distortion compensation unit 1 and the delay unit 11.
The distortion compensation unit 1 generates distortion (predistortion distortion) with respect to the input signal (transmission signal) based on the content of the distortion compensation table, and outputs the signal to the power amplification unit 2. In this example, a distortion compensation coefficient (control value) is stored in the distortion compensation table in association with a signal amplitude value as an address, and the distortion compensation unit 1 determines the amplitude value of the input signal (transmission signal). Then, a distortion compensation coefficient corresponding to the detected value is read out from the distortion compensation table, and distortion (predistortion distortion) is generated using the distortion compensation coefficient.
The power amplifier 2 amplifies the signal input from the distortion compensator 1 and outputs the amplified signal. At this time, the distortion generated in the power amplifying unit 2 and the distortion generated in the distortion compensating unit 1 (predistortion distortion) are canceled out. In an ideal state, the distortion subject to distortion compensation (in this example, the memory effect) (Distortion due to) becomes zero.

The delay unit 11 delays the input signal (transmission signal) by a predetermined time and outputs it to the transmission signal / feedback signal error calculation unit 12.
A part of the output signal from the power amplifier 2 is input to the transmission signal / feedback signal error calculator 12 as a feedback signal.
The transmission signal / feedback signal error calculation unit 12 calculates error information between the signal (transmission signal) input from the delay unit 11 and the feedback signal (output signal from the power amplification unit 2) input from the feedback system. The error information is output to the distortion compensation coefficient calculation unit 13.

The distortion compensation coefficient calculation unit 13 calculates a distortion compensation coefficient (for example, a control value for generating distortion) based on the error information input from the transmission signal / feedback signal error calculation unit 12, and the result The information is output to the distortion compensation table calculation unit 14.
Based on the information input from the distortion compensation coefficient calculation unit 13, the distortion compensation table calculation unit 14 includes the contents of the distortion compensation table (in this example, the distortion compensation coefficient (control value associated with the amplitude value of the signal as an address). )) Is calculated and updated.
By such feedback control, for example, it is possible to adaptively control the predistortion process so that good distortion compensation is always performed following a temperature change or an aging change.

This will be described in more detail with reference to FIGS.
FIG. 2 shows an example of a processing procedure for calculating the content of the distortion compensation table by calculating the error between the input signal (transmission signal) and the feedback signal.
When this processing is started (step S1), the feedback signal passes through the power amplification unit 2 and thus is delayed from the input signal (transmission signal), so that the distortion compensation unit 1 and the power amplification are performed on the input signal (transmission signal). A delay amount corresponding to the delay amount of the unit 2 is set in the delay unit 11 (step S2), and the timings of the input signal (transmission signal) and the feedback signal are matched.
Here, the delay amount set in the delay unit 11 may be set in advance, for example, or a configuration that can be changed by an operation by a user (person) or automatically by a device may be used.

Next, the processing of step S4 to step S9 is repeatedly executed for a predetermined averaging number (for example, 256 times) (step S3, step S10).
First, the transmission signal / feedback signal error calculation unit 12 acquires an input signal (transmission signal) and a feedback signal (step S4). In this example, the amplitude and phase information of the input signal (transmission signal) and the amplitude and phase information of the feedback signal are acquired by a certain number of samples (smp: 1024 samples, for example).

And the process of step S6-step S8 is performed about the predetermined sample number (for example, 1024 samples) (step S5, step S9). Here, in this example, in order to calculate the correction value of the distortion compensation table, error information between the input signal (transmission signal) and the feedback signal is calculated.
Specifically, the transmission signal / feedback signal error calculation unit 12 adjusts the average amplitude level of the feedback signal to match the average amplitude level of the input signal (transmission signal) by (Equation 2) (step S6).

In (Equation 2), FB_R _i 'represents the amplitude information of the feedback signal after the level correction, FB_R _i and FB_R _j represents the amplitude information of the feedback signal, Tx_R _j is the input signal (transmission signal) It represents amplitude information. Moreover, smp represents the number of samples.

Subsequently, the transmission signal / feedback signal error calculation unit 12 calculates an error between the input signal (transmission signal) and the feedback signal using (Equation 3) (step S7).
Here, in this example, a complex signal composed of an I-phase component and a Q-phase component is used as an input signal (transmission signal) or a feedback signal, and an I-phase result and a Q-phase result are obtained as error calculation results. .

In (Expression 3), Ierr represents the I-phase error, Qerr represents the Q-phase error, FB_R _i represents the amplitude information of the feedback signal, and Tx_R _i represents the amplitude information of the transmission signal. cage, FB_P _i represents the phase information of the feedback signal, Tx_P _i represents the phase information of the transmission signal, the fixed phase amount Fix_P from the power amplifier 2 to the transmission signal / feedback signal error calculating section 12 Represents.

Subsequently, the transmission signal / feedback signal error calculation unit 12 accumulates the I-phase error and the Q-phase error for each address of the distortion compensation table corresponding to the amplitude of the input signal (transmission signal) (step S8). In this example, in order to effectively compensate the distortion due to the memory effect, the I-phase error and the Q-phase error are cumulatively added to the address of the distortion compensation table corresponding to the amplitude (transmission amplitude) of the current sample, and one sample is obtained. For the address of the distortion compensation table corresponding to the previous amplitude (transmission amplitude), a value obtained by inverting the signs (positive and negative signs) of the I-phase error and Q-phase error is cumulatively added.
Further, the transmission signal / feedback signal error calculation unit 12 adds 1 to the number of data with respect to the address of the distortion compensation table to which the error has been cumulatively added in order to average the error (step S8).

Subsequently, the transmission signal / feedback signal error calculation unit 12 determines whether or not the processing in steps S6 to S8 has been executed for a predetermined number of samples (step S9).
If it is determined that the processing in steps S6 to S8 has been performed for a predetermined number of samples, the transmission signal / feedback signal error calculation unit 12 adds 1 to the number of executions of the processing in steps S4 to S9, for example. Then, it is determined whether or not the processing of step S4 to step S9 has been repeatedly executed for a predetermined averaging number (for example, whether or not the next execution number has exceeded a predetermined averaging number) (step S10).
If it is determined that the processes in steps S4 to S9 have been repeated a predetermined number of times of averaging, the processes after step S11 are executed.

FIG. 3 conceptually shows an example of a cumulative error calculation method.
In FIG. 3, the upper horizontal axis represents amplitude (transmission amplitude), the upper vertical axis represents time, the lower horizontal axis represents the address of the distortion compensation table, and the lower vertical axis The axis represents the number of errors and the error.
In this example, in order to effectively compensate for distortion due to the memory effect, the address of the distortion compensation table corresponding to the amplitude (transmission amplitude) one sample before (new accumulated error = previous accumulated error−current error) ) And (new accumulated error = previous accumulated error + current error) for the address of the distortion compensation table corresponding to the amplitude (transmission amplitude) of the current sample (current sample). .

Next, the transmission signal / feedback signal error calculation unit 12 uses a certain interval (in this example, for calculating the distortion compensation table later) for the I-phase error and the Q-phase error accumulated for each address of the distortion compensation table. As an example, after dividing into 9 sections) and accumulating in each section, the average (average I-phase error, average Q-phase error) is taken with the number of samples (number of data) in each section (step S11).
Here, as a method of dividing the section, for example, when the number of addresses in the distortion compensation table is 1024, the first section and the ninth section are calculated with 64 addresses, and the second section to the eighth section are 128 addresses. calculate.
FIG. 4 shows an example of the relationship between the section and the address of the distortion compensation table.

  Next, based on the result obtained by the transmission signal / feedback signal error calculation unit 12, the distortion compensation coefficient calculation unit 13 calculates each distortion compensation coefficient from the I-phase error in each section according to (Equation 4). The same process is performed for the Q phase (step S12). In this example, the value obtained by inverting the sign of the I-phase error is weighted to correct the distortion compensation coefficient, and the same calculation is performed for the Q-phase.

In (Expression 4), Adj_Coef _n represents a distortion compensation coefficient after correction, Coef _n represents a distortion compensation coefficient (before correction), and AveIerr _n represents an average I-phase error.
Note that the initial value of the distortion compensation coefficient may be set arbitrarily.

  Here, when the number of error samples (data number) is 0, the distortion compensation coefficient cannot be corrected. Therefore, the number of error samples (data) in the section after the third section (section 3). If the (number) is 0, the distortion compensation coefficient is estimated by extrapolating from the zero order according to (Equation 5).

FIGS. 5A and 5B show an example of 0th-order extrapolation in a section where the number of error samples (number of data) is zero.
In the graph of FIG. 5A, the horizontal axis represents the distortion compensation table address (distortion compensation coefficient number), and the vertical axis represents the distortion compensation coefficient value.
In the graph of FIG. 5B, the horizontal axis represents the distortion compensation table address (distortion compensation coefficient number), and the vertical axis represents the error sample number (data number).
Here, the address (distortion compensation coefficient number) in the distortion compensation table represents the address of the representative point in each section (for example, the address in the center or the vicinity in each section, or obtained by another method). Assume that the number of error samples (the number of data) and the value of the distortion compensation coefficient correspond to the representative points in each section.

In the example of FIGS. 5A and 5B, the number of error samples (number of data) in each section from the third section (section 3) to the seventh section (section 7) is not zero. Since the number of error samples (number of data) in the eighth section (section 8) is 0, the distortion compensation coefficient value in the immediately preceding section 7 (in this example, for example, the value after correction) is the 0th order. By extrapolation, the distortion compensation coefficient value in section 8 is set to be the same value as the distortion compensation coefficient value in section 7.
In the example of FIGS. 5A and 5B, the number of error samples (number of data) is also zero for the ninth interval (interval 9), so that the 0th order extrapolation in the immediately preceding interval 8 is performed. By extrapolating the value of the subsequent distortion compensation coefficient (or the value of the distortion compensation coefficient in the immediately preceding section 7 while the number of error samples (data number) is not 0 (in this example, for example, correction) It is also possible to consider that the later value) is zero-order extrapolation), and the value of the distortion compensation coefficient after the zero-order extrapolation in section 8 (or the distortion in section 7) It is set to use the same value as the compensation coefficient).

  In addition, the error used for correcting the distortion compensation coefficient of the representative point (first representative point) of the address in the first section (section 1) usually has a large variation in error. About the value of the distortion compensation coefficient of the 1st representative point in the area 1, it carries out 0th-order extrapolation unconditionally by (Formula 6).

FIGS. 6A and 6B show an example of a state of zero-order extrapolation of the value of the distortion compensation coefficient at the first representative point in section 1.
In the graph of FIG. 6A, the horizontal axis represents the distortion compensation table address (distortion compensation coefficient number), and the vertical axis represents the distortion compensation coefficient value.
In the graph of FIG. 6B, the horizontal axis represents the distortion compensation table address (distortion compensation coefficient number), and the vertical axis represents the difference (error) of each sample between the input signal (transmission signal) and the feedback signal. Represents.
Here, the address (distortion compensation coefficient number) in the distortion compensation table represents the address of the representative point in each section (for example, the address in the center or the vicinity in each section, or obtained by another method). Assume that the number of error samples (the number of data) and the value of the distortion compensation coefficient correspond to the representative points in each section.

  In the example of FIGS. 6A and 6B, the value of the distortion compensation coefficient in the immediately following section 2 (in this example, the corrected value, for example) is extrapolated from the first representative point in the section 1 to the zeroth order. Accordingly, the distortion compensation coefficient value in section 1 is set to be the same value as the distortion compensation coefficient value in section 2.

  When the number of error samples (data number) in section 2 is 0, or when the number of error samples (data number) in section 3 (or several subsequent sections) is 0, The distortion compensation coefficient value (for example, the corrected value in this example) in the immediately following section (for example, any section after section 3) while the number of error samples (data number) is not zero. It is also possible to set the value of the distortion compensation coefficient in the section 2 or the like before the zero order extrapolation.

  Further, in this example, the value of the distortion compensation coefficient in the section 1 is obtained by extrapolating the value of the distortion compensation coefficient in the section 2 with zero order extrapolation. For example, not only the section 1 (first representative point) but also the section 2 (first representative point) is obtained. (2 representative points) or a predetermined interval thereafter, when there is a large variation in error, a configuration in which the range of the 0th-order extrapolation is widened may be used. As a specific example, an interval m (here In this case, the value of the distortion compensation coefficient in m is an integer value equal to or greater than 1) can be set to the same value as the value of the distortion compensation coefficient in the section m + 1.

  Next, the distortion compensation table calculation unit 14 calculates distortion compensation coefficient values calculated by the distortion compensation coefficient calculation unit 13 (in this example, values of distortion compensation coefficients at nine representative points in nine sections 1 to 9). ) For each point (each address) between the representative points, by interpolating the value of the distortion compensation coefficient (for example, cubic spline interpolation), from the value of the distortion compensation coefficient at the representative point and its interpolation result The content of the configured distortion compensation table is calculated and set in the distortion compensation unit 1 (step S13). Thereby, this process is complete | finished (step S14).

  As described above, in the distortion compensation apparatus of this example, the delay unit 11 that delays the input signal (transmission signal), and the transmission signal / feedback signal error calculation unit 12 that calculates an error between the input signal (transmission signal) and the feedback signal. A distortion compensation coefficient calculation unit 13 that calculates a distortion compensation coefficient (in this example, a distortion compensation coefficient at each representative point of a plurality of sections) from the error calculated by the transmission signal / feedback signal error calculation unit 12, a distortion compensation coefficient A distortion compensation table calculation unit 14 that calculates the content of the distortion compensation table from the distortion compensation coefficient calculated by the calculation unit 13 (by interpolation in this example), a distortion compensation unit 1 that compensates for nonlinear distortion, and an input signal (transmission signal) The power amplifier 2 is provided.

  In the distortion compensation apparatus of this example, for example, the time until convergence of distortion power is reduced by correcting the distortion compensation table from the errors related to the amplitude information and phase information of the input signal (transmission signal) and the feedback signal. Therefore, it is possible to eliminate the fluctuation of the spectrum of the input signal (transmission signal) and eliminate the need for special measures against the frequency information of the carrier signal and the burst wave.

  Therefore, in the distortion compensation device of this example, for example, it is possible to easily cope with a burst wave, and distortion compensation can be performed without frequency information. It can be easily applied to products having different sources, signal bands, transmission frequencies, and the like.

Here, as an example, the function of the distortion compensation apparatus as in this example can be provided in a transmitter (for example, a transmission amplification apparatus) used in a base station apparatus of a mobile communication system. The generated distortion (distortion such as memory effect) can be compensated. Further, the function of the distortion compensation apparatus as in this example can be applied to, for example, a digital predistorter (DPD).
Further, as an apparatus having the function of a distortion compensating apparatus as in this example, an amplifying apparatus that compensates for distortion such as a memory effect can be implemented.

  In the distortion compensation apparatus of the present example, the coefficient storage unit is configured by the function of the distortion compensation unit 1 and the like storing the information of the distortion compensation table, and the amplifier of the power amplifying unit 2 is an amplifier for distortion compensation. An error detection unit is configured by the functions of the delay unit 11 and the transmission signal / feedback signal error calculation unit 12, and a representative acquisition unit configured to acquire a distortion compensation coefficient at a representative address is configured by the function of the distortion compensation coefficient calculation unit 13. Thus, an updating means for updating the information of the distortion compensation table is configured by the function of the distortion compensation table calculation unit 14.

(Hereinafter, other configuration examples A1 to A3)
Other configuration examples A1 to A3 are shown below.
All or part of each of these configuration examples A1 to A3 may be used in the present invention. For example, an address generated by the address generation means in the configuration example A1 can be used as a representative address, and error information (error data) outside the set range in the configuration example A2 In addition, the error data between the input signal and the output signal of the amplifier in the configuration example A3 is mapped to the address acquired for the input signal, and the input signal and the amplifier are used. It is possible to use a configuration in which data obtained by inverting the sign (positive or negative sign) of error data with respect to the output signal is mapped to an address acquired for an input signal that is earlier than the input signal.

[1] (Configuration Example A1) In this configuration example A1, a distortion compensator that compensates for distortion generated by an amplifier that amplifies an input signal by a predistortion system is configured as follows.
That is, the coefficient storage means stores a distortion compensation coefficient for predistorting the input signal corresponding to each address at each address. Address detecting means detects an address of 0th to (M−1) th M (M is an integer of 2 or more) bits corresponding to the input signal. The address generation means uses the set N (N is an integer smaller than M) and sets the bit values from 0 to (M−N−2) -th for the M-bit address detected by the address detection means. An address is generated by rounding down and rounding down the (M−N−1) -th bit value (0 is rounded down and 1 is rounded up). Error mapping means maps error data between the input signal and the output signal of the amplifier to the address generated by the address generation means for the input signal, averages each address, and error information based on the result Is generated. Update control means updates the stored contents of the coefficient storage means based on the error information generated by the error mapping means.

  Therefore, since error data is mapped and averaged to a representative address generated based on an address corresponding to an input signal, for example, in a power amplifier having a complicated nonlinear characteristic, Compared to the above, it is expected that approximation close to the ideal is performed and sufficient performance of the DPD is obtained, and distortion compensation can be effectively performed.

Here, in the coefficient storage means (for example, memory), as the correspondence between the address and the signal, for example, the correspondence between the signal level (for example, amplitude or power value) and the address can be used.
Further, as the distortion compensation coefficient, various values may be used depending on, for example, a configuration method for executing distortion compensation.

Various values may be used as the bit number M of the M-bit address and the bit number N of the higher N bits.
As the error, for example, an amplitude error or a phase error can be used.
The error data may be averaged in various modes. For example, a mode in which averaging is performed for each update period of the storage contents of the coefficient storage means can be used.

Further, as the error information, various information regarding the error may be used.
In addition, various modes may be used as a mode of updating the storage contents of the coefficient storage unit based on the error information. For example, a mode of updating so as to reduce the error indicated by the error information is used. Can do.

[2] (Configuration Example A2) In this configuration example A2, a distortion compensation apparatus that compensates for distortion generated by an amplifier that amplifies an input signal by a predistortion system is configured as follows.
That is, the coefficient storage means stores a distortion compensation coefficient for predistorting the input signal corresponding to each address at each address. An address acquisition unit acquires an address corresponding to the input signal or an address based thereon. The error data selection means excludes error data out of the set range from the error data between the input signal and the output signal of the amplifier, and outputs other error data (error data within the set range). ) Is selected. The error mapping means maps error data between the input signal selected by the error data selection means and the output signal of the amplifier to the address obtained by the address obtaining means for the input signal, and for each address Averaging is performed, and error information based on the result is generated. Update control means updates the stored contents of the coefficient storage means based on the error information generated by the error mapping means.

  Therefore, with respect to the error data between the input signal and the output signal of the amplifier, the error data out of the set range is excluded and other error data (error data within the set range) is selected. Therefore, for example, it is expected that the initial convergence time of nonlinear inverse characteristics and the time required for tracking will be shortened while ensuring the stability of distortion compensation compared with the conventional case, and distortion compensation is effectively performed. It can be carried out.

Here, in the coefficient storage means (for example, memory), as the correspondence between the address and the signal, for example, the correspondence between the signal level (for example, amplitude or power value) and the address can be used.
Further, as the distortion compensation coefficient, various values may be used depending on, for example, a configuration method for executing distortion compensation.

Further, as the address acquisition means, for example, an address detection means for detecting an address corresponding to the input signal is used, or an address such as a representative is generated from the address detection means and the address detected by the address detection means. Address generation means can be used.
As the error, for example, an amplitude error or a phase error can be used.
Moreover, various ranges may be used as the range regarding the error. For example, both the upper limit and the lower limit may be used, or only one of the upper limit and the lower limit may be used. Moreover, as a range, for example, it may be expressed by “more than” or “less than”, or may be expressed by “greater than” or “less than”.
The error data may be averaged in various modes. For example, a mode in which averaging is performed for each update period of the storage contents of the coefficient storage means can be used.

Further, as the error information, various information regarding the error may be used.
In addition, various modes may be used as a mode of updating the storage contents of the coefficient storage unit based on the error information. For example, a mode of updating so as to reduce the error indicated by the error information is used. Can do.

[3] (Configuration Example A3) In this configuration example A3, a distortion compensation apparatus that compensates for distortion due to the memory effect generated by an amplifier that amplifies an input signal by a predistortion system is configured as follows.
That is, the memory effect coefficient storage means stores, for each address, a memory effect distortion compensation coefficient for applying predistortion to the input signal corresponding to each address. An address acquisition unit acquires an address corresponding to the input signal or an address based thereon. The error mapping means maps error data between the input signal and the output signal of the amplifier to the address acquired by the address acquisition means for the input signal, and the error mapping between the input signal and the output signal of the amplifier. Data obtained by inverting the sign (positive / negative sign) of data is mapped to the address acquired by the address acquisition means for the input signal that is past the input signal, averaged for each address, and error information based on the result Is generated. Update control means updates the stored contents of the coefficient storage means based on the error information generated by the error mapping means.

  Therefore, the error data between the input signal and the output signal of the amplifier is mapped to the address obtained for the input signal, and the data obtained by inverting the sign of the error data between the input signal and the output signal of the amplifier is Using a configuration in which the input signal is mapped to an address acquired for a past input signal, a configuration preferable for DPD that compensates for the memory effect (for example, updating of the storage contents of coefficient storage means based on error information) is realized. Distortion compensation can be performed effectively.

Here, in the coefficient storage means (for example, memory), as the correspondence between the address and the signal, for example, the correspondence between the signal level (for example, amplitude or power value) and the address can be used.
Further, as the distortion compensation coefficient, various values may be used depending on, for example, a configuration method for executing distortion compensation.

Further, as the address acquisition means, for example, an address detection means for detecting an address corresponding to the input signal is used, or an address such as a representative is generated from the address detection means and the address detected by the address detection means. Address generation means can be used.
As the error, for example, an amplitude error or a phase error can be used.
The error data may be averaged in various modes. For example, a mode in which averaging is performed for each update period of the storage contents of the coefficient storage means can be used.

Further, as the error information, various information regarding the error may be used.
In addition, various modes may be used as a mode of updating the storage contents of the coefficient storage unit based on the error information. For example, a mode of updating so as to reduce the error indicated by the error information is used. Can do.
(Other configuration examples A1 to A3)

Here, the configuration of the system and apparatus according to the present invention is not necessarily limited to the configuration described above, and various configurations may be used. The present invention can also be provided as, for example, a method or method for executing the processing according to the present invention, a program for realizing such a method or method, or a recording medium for recording the program. It is also possible to provide various systems and devices.
The application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
In addition, as various processes performed in the system and apparatus according to the present invention, for example, the processor executes a control program stored in a ROM (Read Only Memory) in hardware resources including a processor and a memory. A controlled configuration may be used, and for example, each functional unit for executing the processing may be configured as an independent hardware circuit.
The present invention can also be understood as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the control program, and the program (itself). The processing according to the present invention can be performed by inputting the program from the recording medium to the computer and causing the processor to execute the program.

  1, 101... Distortion compensation unit 2, 102.. Power amplification unit 11.. Delay unit 12.. Transmission signal / feedback signal error calculation unit 13.. Distortion compensation coefficient calculation unit 14, 114. Distortion compensation table calculation unit, 111.. FFT operation unit, 112 ... Distortion power detection unit, 113 ... Coefficient perturbation unit,

Claims (1)

In a distortion compensation device that compensates for distortion generated by an amplifier that amplifies an input signal by a predistortion method,
Coefficient storage means for storing a distortion compensation coefficient for giving predistortion to an input signal corresponding to each address at each address;
Error detection means for detecting information relating to an error between the input signal and the signal output from the amplifier;
Based on the information on the error detected by the error detection means, a distortion compensation coefficient at a predetermined plurality of representative addresses is acquired. In this case, the information on the error for acquiring the distortion compensation coefficient is a predetermined condition. A representative acquisition means for acquiring a representative address that is insufficient based on the first-order extrapolation using a distortion compensation coefficient acquired for another representative address;
Updating means for updating the storage contents of the coefficient storage means based on the distortion compensation coefficient at the representative address acquired by the representative acquisition means;
Equipped with a,
The predetermined representative addresses are one representative address for each section obtained by dividing the address range of the coefficient storage unit into a predetermined plurality,
As a technique for obtaining a distortion compensation coefficient at the representative address, information on errors is averaged or cumulatively added for each address of the coefficient storage means, and a plurality of sections provided in the address range of the coefficient storage means are obtained. Averaging or accumulating the results of averaging or accumulating included in each, obtaining a distortion compensation coefficient using the result, and associating the distortion compensation coefficient with one representative address for each section Is,
As a technique for determining a representative address for which information on an error for obtaining the distortion compensation coefficient is insufficient based on a predetermined condition, one or a plurality of predetermined plural ones from the higher amplitude level of the input signal are used. When there is no information about an error for obtaining a distortion compensation coefficient in each representative address, one address or a plurality of predetermined representative addresses from the lower one of the amplitude level of the input signal About the condition to determine that it is insufficient,
As another representative address used when performing the 0th-order extrapolation, the address where the distortion compensation coefficient is effectively acquired and the amplitude level of the input signal is the closest is used.
A distortion compensation apparatus characterized by the above.

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