Parameter changing device, transmitter, parameter changing method, and program

Abstract

To change a parameter of a distortion compensation section without providing a feedback circuit.SOLUTION: A parameter change device (11) comprises: a multiplier (111) which multiplies a test signal by a back-off rate; a first distortion compensation simulation section (113) which performs distortion compensation processing on a signal obtained by the multiplication using a stored parameter; a scaling section (114) which scales an output signal of the first distortion compensation simulation section (113); a second distortion compensation simulation section (115) which performs distortion compensation processing on the test signal using a parameter different from that of the first distortion compensation simulation section (113); a differentiator (116) which calculates an error between a value of a signal obtained by the scaling and a value of an output signal of the second distortion compensation simulation section (115); an approximate error minimization section (117) for calculating a parameter of the second distortion compensation simulation section (115) which minimizes the error; and an output section (118) which outputs the parameter of the second distortion compensation simulation section (115) to a distortion compensation unit (12).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a parameter changing device, a transmitter, a parameter changing method, and a program. [Background technology]

[0002] In wireless communication systems such as mobile communication systems, the transmitter amplifies the wireless signal using a power amplifier (hereinafter referred to as "PA" as appropriate) and transmits the amplified wireless signal to the receiver.

[0003] Furthermore, in transmitters of wireless communication systems, it is essential to provide a distortion compensation unit that performs distortion compensation processing to compensate for the nonlinear distortion of the PA using parameters in order to achieve high-capacity and highly efficient communication. Examples of distortion compensation units include DPD (Digital Predistortion) type distortion compensation units (for example, Patent Document 1). On the other hand, calculating the optimal parameters for the distortion compensation section requires a feedback circuit that feeds back the output signal of the PA (for example, Patent Document 2).

[0004] Now, referring to Figure 12, an example of a transmitter configuration with a feedback circuit will be described as a transmitter related to the relevant technology. The transmitter 90 shown in Figure 12 comprises a signal processing unit 91, a distortion compensation unit 92, a DA converter (Digital to Analog Converter; hereinafter referred to as "DAC" as appropriate) 93, a mixer 94, an oscillator 95, a PA 96, a transmitting antenna 97, and a feedback circuit 98. The feedback circuit 98 also comprises a mixer 981, an AD converter (Analog to Digital Converter; hereinafter referred to as "ADC" as appropriate) 982, and a parameter update unit 983.

[0005] The distortion compensation unit 92 performs distortion compensation processing on the output signal of the signal processing unit 91 using parameters updated by the parameter update unit 983 to compensate for the nonlinear distortion of PA 96. DAC93 performs a DA conversion on the output signal of the distortion compensation unit 92, converting it from a digital signal to an analog signal.

[0006] The mixer 94 upconverts the output signal from the DAC 93 to the radio frequency by mixing it with the local frequency oscillation signal generated by the oscillator 95. PA96 amplifies the output signal of mixer 94. The transmitting antenna 97 transmits the output signal of PA96 to the receiver (not shown).

[0007] The output signal from PA96 is fed back to mixer 981. Mixer 981 downconverts the output signal from PA96 to an intermediate frequency by mixing it with the local frequency oscillation signal generated by oscillator 95.

[0008] The ADC982 performs A / D conversion of the output signal from the mixer 981, converting it from an analog signal to a digital signal. The parameter update unit 983 updates the parameters of the distortion compensation unit 92 using the output signals of the signal processing unit 91 and the output signals of the ADC 982. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] International Publication No. 2021 / 054118 [Patent Document 2] Japanese Patent Publication No. 2015-005965 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, when a feedback circuit is provided in the transmitter as in the technology described in Patent Document 2, there is a problem that an additional cost of the feedback circuit is incurred, and particularly since the ADC is expensive, the cost of the transmitter increases.

[0011] Therefore, an object of the present disclosure is to provide a parameter changing device, a transmitter, a parameter changing method, and a program capable of changing parameters of a distortion compensation unit without providing a feedback circuit in view of the above-described problems.

Means for Solving the Problems

[0012] A parameter changing device according to one aspect is a parameter changing device that changes parameters of a distortion compensation unit that performs distortion compensation processing for compensating non-linear distortion of an amplifier, a multiplier that multiplies an input test signal by an input back-off rate, a first distortion compensation simulation unit that performs distortion compensation processing on the output signal of the multiplier using parameters stored in a parameter storage unit, a scaling unit that scales the output signal of the first distortion compensation simulation unit, a second distortion compensation simulation unit that performs distortion compensation processing on the input test signal using parameters different from those of the first distortion compensation simulation unit, a differentiator that calculates an error between the value of the output signal of the scaling unit and the value of the output signal of the second distortion compensation simulation unit, an approximate error minimization unit that calculates parameters of the second distortion compensation simulation unit that minimize the error calculated by the differentiator, an output unit that outputs, as parameters of the distortion compensation unit, the parameters of the second distortion compensation simulation unit calculated by the approximate error minimization unit to the distortion compensation unit, and includes.

[0013] A transmitter according to one aspect is the amplifier, the distortion compensation unit that performs distortion compensation processing for compensating non-linear distortion of the amplifier, A parameter changing device for changing the parameters of the strain compensation unit, It is equipped with.

[0014] One method for changing parameters is: A parameter changing method using a parameter changing device for changing the parameters of a distortion compensation unit that performs distortion compensation processing to compensate for the nonlinear distortion of an amplifier, Inputting the backoff rate and test signal, Multiplying the test signal by the backoff rate, In the first distortion compensation simulation unit, distortion compensation processing is performed on the signal obtained by the multiplication using the parameters stored in the parameter storage unit. The output signal of the first distortion compensation simulation unit is scaled, In the second distortion compensation simulation unit, distortion compensation processing is performed on the test signal using parameters different from those used in the first distortion compensation simulation unit. The error between the value of the signal obtained by the scaling and the value of the output signal of the second distortion compensation simulation unit is calculated. To calculate the parameters of the second strain compensation simulation unit that minimize the calculated error, The parameters of the second strain compensation simulation unit calculated above are output to the strain compensation unit as parameters of the strain compensation unit. Includes.

[0015] A program according to one aspect is: A program to be executed by a computer to change the parameters of a distortion compensation section that performs distortion compensation processing to compensate for the nonlinear distortion of an amplifier, Inputting the backoff rate and test signal, Multiplying the test signal by the backoff rate, In the first distortion compensation simulation unit, distortion compensation processing is performed on the signal obtained by the multiplication using the parameters stored in the parameter storage unit. The output signal of the first distortion compensation simulation unit is scaled, In the second distortion compensation simulation unit, distortion compensation processing is performed on the test signal using parameters different from those used in the first distortion compensation simulation unit. The error between the value of the signal obtained by the scaling and the value of the output signal of the second distortion compensation simulation unit is calculated. To calculate the parameters of the second strain compensation simulation unit that minimize the calculated error, The parameters of the second strain compensation simulation unit calculated above are output to the strain compensation unit as parameters of the strain compensation unit. Includes. [Effects of the Invention]

[0016] According to the above-described embodiment, the effect is obtained that a parameter changing device, transmitter, parameter changing method, and program can be provided that can change the parameters of the distortion compensation section without providing a feedback circuit. [Brief explanation of the drawing]

[0017] [Figure 1] This figure shows an example of the configuration of the transmitter according to Embodiment 1. [Figure 2] This figure shows an example of a method for determining the backoff rate according to Embodiment 1. [Figure 3] This figure shows an example of a modified configuration of the transmitter according to Embodiment 1. [Figure 4] This figure shows an example of the configuration of a circuit for determining the parameters of the first distortion compensation simulation unit according to Embodiment 1, and an example of the calculations performed by each component of the circuit. [Figure 5] This figure shows an example of the calculation contents of each component in the parameter changing device according to Embodiment 1. [Figure 6] This is a flowchart showing an example of the general operation flow of the parameter changing device according to Embodiment 1. [Figure 7] This is an enlarged diagram showing the periphery of the first distortion compensation simulation unit according to Embodiment 1. [Figure 8] This figure shows an example of the configuration of a transmitter according to Embodiment 2. [Figure 9] This figure shows an example of the configuration of a transmitter according to Embodiment 3. [Figure 10] This figure shows an example of the configuration of a transmitter according to Embodiment 4. [Figure 11] This figure shows an example configuration of a parameter changing device according to Embodiment 5. [Figure 12] This diagram shows an example of the configuration of a transmitter related to the relevant technology. [Modes for carrying out the invention]

[0018] Embodiments of this disclosure will be described below with reference to the drawings. Note that the following description and drawings have been omitted and simplified as appropriate for clarity of explanation. Furthermore, in the following drawings, the same elements are denoted by the same reference numerals, and redundant explanations have been omitted where necessary.

[0019] <Embodiment 1> First, with reference to Figure 1, an example of the configuration of the transmitter 10 according to this embodiment 1 will be described. As shown in Figure 1, the transmitter 10 according to this embodiment 1 includes a parameter changing device 11, a strain compensation unit 12, and a PA 13.

[0020] In addition to the components shown in Figure 1, the transmitter 10 also includes components corresponding to the signal processing unit 91, DAC 93, mixer 94, oscillator 95, and transmitting antenna 97 shown in Figure 12. However, these components are not essential components of this disclosure and are therefore omitted from Figure 1.

[0021] The strain compensation units 12 and PA13 correspond to the strain compensation units 92 and PA96 shown in Figure 12, respectively. Therefore, the input signal to the distortion compensation unit 12 corresponds to the output signal of the signal processing unit 91 shown in Figure 12. The distortion compensation unit 12 performs distortion compensation processing on the input signal using parameters to compensate for the nonlinear distortion of PA 13. The distortion compensation unit 12 is, for example, a DPD-type distortion compensation unit. The signal input to PA 13 corresponds to the output signal of the mixer 94 shown in Figure 12. PA 13 amplifies this signal.

[0022] The parameter changing device 11 is a device that changes the parameters of the distortion compensation unit 12 using the input PA 13 backoff rate and test signal, and outputs the changed parameters to the distortion compensation unit 12.

[0023] The parameter changing device 11 includes a multiplier 111, a parameter storage unit 112, a first distortion compensation simulation unit 113, a scaling unit 114, a second distortion compensation simulation unit 115, a differencer 116, an approximation error minimization unit 117, and an output unit 118.

[0024] The multiplier 111 multiplies the input test signal by the backoff rate of the input PA13. The parameter storage unit 112 stores the parameters of the first distortion compensation simulation unit 113.

[0025] The first distortion compensation simulation unit 113 performs distortion compensation processing on the output signal of the multiplier 111 using the parameters stored in the parameter storage unit 112. The second distortion compensation simulation unit 115 performs distortion compensation processing on the input test signal using different parameters than those used by the first distortion compensation simulation unit 113.

[0026] The first distortion compensation simulation unit 113 and the second distortion compensation simulation unit 115 perform the same distortion compensation processing as the distortion compensation unit 12, except that they use different parameters. Therefore, the first distortion compensation simulation unit 113 and the second distortion compensation simulation unit 115 are, for example, DPD-type distortion compensation units.

[0027] Furthermore, the distortion compensation unit 12, the first distortion compensation simulation unit 113, and the second distortion compensation simulation unit 115 may be composed of memory polynomials. A DPD-type distortion compensation unit composed of memory polynomials is described, for example, in Non-Patent Document 1. Non-patent document 1: J. Kim, K. Konstantinou, “Digital Predistortion of wide band signals based on power amplifier with memory”, IET Electron Ketter, Vol.37 No.23, pp.1417-1418, November 2001

[0028] The scaling unit 114 scales the output signal of the first distortion compensation simulation unit 113. The differencer 116 calculates the error between the output signal value of the scaling unit 114 and the output signal value of the second distortion compensation simulation unit 115.

[0029] The approximation error minimization unit 117 calculates the parameters of the second distortion compensation simulation unit 115, which minimizes the error calculated by the differencer 116. The output unit 118 outputs the parameters of the second strain compensation simulation unit 115, calculated by the approximation error minimization unit 117, to the strain compensation unit 12 as parameters for the strain compensation unit 12.

[0030] Note that in Figure 1, the unidirectional arrow simply indicates the direction of a signal (data) flow and does not exclude bidirectionality (the same applies to Figures 3, 4, 5, 7, 8, 9, and 10, which will be discussed later).

[0031] Furthermore, the parameter storage unit 112 is not an essential component of the parameter changing device 11 and may be provided outside of the parameter changing device 11. In other words, the parameter changing device 11 may be realized with a minimum configuration consisting of a multiplier 111, a first distortion compensation simulation unit 113, a scaling unit 114, a second distortion compensation simulation unit 115, a differencer 116, an approximation error minimization unit 117, and an output unit 118.

[0032] The configuration of the parameter changing device 11 will be described in more detail below. First, let's explain the backoff rate and test signal of PA13 that are input to the multiplier 111.

[0033] The test signal is a signal with the same properties as the input signal of the distortion compensation unit 12 (for example, a signal modulated with the same modulation scheme as the input signal of the distortion compensation unit 12). Alternatively, the test signal may be the same signal as the input signal of the distortion compensation unit 12.

[0034] The backoff rate of PA13 is determined according to the communication distance between the transmitter 10 and the receiver (not shown) and the communication quality of the receiver. An example of how to determine the backoff rate is described below.

[0035] Step S101: The spatial attenuation rate is calculated based on the communication distance between the transmitter 10 and the receiver. Based on the calculated spatial attenuation rate, the appropriate output power (=operating point) for the transmitter 10 is determined, and the backoff rate that results in the determined output power is set as the initial value of the backoff rate. Thereafter, steps S102 and S103 are repeated, starting from the initial value of the backoff rate.

[0036] Step S102: The backoff rate is updated by adding +Δγ, and it is determined whether the receiver's communication quality improves. If the communication quality improves, the update of the backoff rate is reflected, and the process returns to step S102. On the other hand, if the communication quality does not improve, the backoff rate is reset to its original value (backoff rate is reduced by -Δγ), and the process proceeds to step S103. Figure 2 shows how the receiver's communication quality improves when the backoff rate is increased by +Δγ from its initial value. Note that in Figure 2, a lower communication quality value indicates better communication quality.

[0037] Step S103: The backoff rate is updated by -Δγ, and it is determined whether the receiver's communication quality improves. If the communication quality improves, the update of the backoff rate is reflected, and the process returns to step S102. On the other hand, if the communication quality does not improve, the backoff rate is restored to its original value (backoff rate is increased by +Δγ), and the process returns to step S102.

[0038] As described above, in steps S101 to S103, the so-called descent method is used to find the backoff rate that minimizes the receiver's communication quality value. Then, the backoff rate that minimizes the communication quality value is input to the multiplier 111.

[0039] The user may determine the backoff rate. In this case, the user may determine the backoff rate as described above, input the determined backoff rate along with the test signal to the multiplier 111, and also input the test signal to the second distortion compensation simulation unit 115.

[0040] Alternatively, as shown in Figure 3, the backoff rate may be determined by an input unit 110 located before the multiplier 111. In this case, the input unit 110 may determine the backoff rate as described above, input the determined backoff rate along with the test signal to the multiplier 111, and also input the test signal to the second distortion compensation simulation unit 115.

[0041] Next, referring to Figure 4, the parameters of the first distortion compensation simulation unit 113 stored in the parameter storage unit 112 will be described. Figure 4 shows an example of the configuration of a circuit for determining the parameters of the first distortion compensation simulation unit 113 and an example of the calculations performed by each component of that circuit.

[0042] The circuit shown in Figure 4 comprises a strain compensation unit 21, a PA 22, and a parameter optimization unit 23. In Figure 4, the strain compensation unit 21 is assumed to be composed of a memory polynomial.

[0043] As shown in Figure 4, the distortion compensation unit 21 processes the signal x at time n. n And the following signal sequence, including past signal sequences. TIFF0007838396000001.tif55 is inputted. TIFF0007838396000002.tif552 The distortion compensation unit 21 performs distortion compensation processing on the signal x n using the parameter α k Thereby, the distortion compensation unit 21 obtains the following u n TIFF0007838396000003.tif1657 Here, the operation matrix X is expressed as follows. TIFF0007838396000004.tif577 However, TIFF0007838396000005.tif564 where the symbol * means the product of the components of the vector (the same applies in the following disclosure of the present application) and returns the result of the following vector operation. TIFF0007838396000006.tif5121

[0044] The parameter optimization unit 23 performs delay adjustment so that the signal x n and the signal output from PA22 are synchronized with the signal x n and then scales the value v n so that it matches the power level with the signal x n to calculate the error between them. Thereby, the parameter optimization unit 23 obtains the following error e n TIFF0007838396000007.tif427TIFF0007838396000008.tif551

[0045] Furthermore, the parameter optimization unit 23 updates the parameter α n using the error e k Thereby, the parameter optimization unit 23 obtains the following parameter α k+1 TIFF0007838396000009.tif760 However, TIFF0007838396000010.tif32 is an operator that performs conjugate transpose of the matrix.

[0046] ​​​ The calculation shown in Figure 4 is described, for example, in Non-Patent Document 2. Non-patent document 2: RN Braithwaite, “Closed-loop digital predistortion (DPD) using an observation path with limited bandwidth”, IEEE Trans. Microw. Theory Techn., vol. 63, no. 2, pp. 726-736, Feb. 2015.

[0047] In the circuit shown in Figure 4, the calculation shown in Figure 4 is repeated until the parameter α converges. Once the parameter α converges, the converged parameter α is stored in the parameter storage unit 112.

[0048] Next, with reference to Figure 5, an example of the calculations performed by each component in the parameter changing device 11 will be explained. In Figure 5, the backoff rate of PA13 is γ, and the test signal is y. n Let it be so.

[0049] The multiplier 111 receives the test signal y n The backoff rate γ is multiplied to this. As a result, the multiplier 111 calculates the following signal p n To obtain. TIFF0007838396000011.tif425

[0050] The first distortion compensation simulation unit 113 processes the signal p output from the multiplier 111. n For this, distortion compensation processing is performed using the parameter α stored in the parameter storage unit 112. As a result, the first distortion compensation simulation unit 113 processes the following signal q n To obtain. TIFF0007838396000012.tif518 Here, the operation matrix P is expressed as follows: TIFF0007838396000013.tif576 However, TIFF0007838396000014.tif564

[0051] The scaling unit 114 receives the signal q output from the first distortion compensation simulation unit 113. n The following signals s are scaled. As a result, the scaling unit 114 scales the following signals s n To obtain. TIFF0007838396000015.tif525

[0052] The second distortion compensation simulation unit 115 receives the test signal y n For this, strain compensation processing is performed using the parameter θ calculated by the approximation error minimization unit 117. As a result, the second strain compensation simulation unit 115 processes the following signal z n To obtain. TIFF0007838396000016.tif618 Here, the operation matrix Y is expressed as follows: TIFF0007838396000017.tif575 However, TIFF0007838396000018.tif563

[0053] The differencer 116 receives the signal s output from the scaling unit 114. n The value of and the signal z output from the second distortion compensation simulation unit 115 n The difference between the value of and is calculated. Thus, the differencer 116 calculates the following error e n To obtain. TIFF0007838396000019.tif426

[0054] The approximation error minimization unit 117 performs the following calculation and outputs the error e from the differencer 116. n The parameter θ of the second distortion compensation simulation unit 115 that minimizes the distortion is calculated. The above calculation performed in the approximation error minimization unit 117 of TIFF0007838396000020.tif637 is: This is the operation to minimize TIFF0007838396000021.tif55. The output unit 118 outputs the parameter θ of the second strain compensation simulation unit 115, calculated by the approximation error minimization unit 117, to the strain compensation unit 12 as a parameter for the strain compensation unit 12.

[0055] In this embodiment 1, an example was described in which the distortion compensation unit 12, the first distortion compensation simulation unit 113, and the second distortion compensation simulation unit 115 are configured using memory polynomials, but the embodiment is not limited to this.

[0056] For example, the operation matrix of the memory polynomial (e.g., the operation matrix X, Y, P mentioned above) can be replaced with the operations of a neural network, and the least squares method used in this embodiment 1 can be replaced with the learning (backpropagation) used in neural networks.

[0057] Therefore, the distortion compensation unit 12, the first distortion compensation simulation unit 113, and the second distortion compensation simulation unit 115 may be configured by a neural network. A DPD-type distortion compensation unit configured by a neural network is described, for example, in Non-Patent Documents 3 and 4. Non-patent document 3: Meenakshi Rawat, Fadhel M.Ghannouchi, “A Mutual Distortion and Impairment Compensator for Wideband Direct-Conversion Transmitters Using Neural Networks”, IEEE Transaction on Broadcast, Vol.58 No.2, pp.168-177, June 2012 Non-patent document 4: M. Tanio, N. Ishii and N. Kamiya, "Efficient Digital Predistortion Using Sparse Neural Network", in IEEE Access, vol. 8, pp. 117841-117852, 2020, doi: 10.1109 / ACCESS.2020.3005146.

[0058] The following describes an example of the general operation flow of the parameter changing device 11 with reference to Figure 6. As shown in Figure 6, first, the parameter change device 11 receives the backoff rate of PA13 and a test signal (step S201). Next, the multiplier 111 multiplies the test signal by the backoff rate of PA13 (step S202).

[0059] Next, the first distortion compensation simulation unit 113 performs distortion compensation processing on the output signal of the multiplier 111 using the parameters stored in the parameter storage unit 112 (step S203). Next, the scaling unit 114 scales the output signal of the first distortion compensation simulation unit 113 (step S204).

[0060] Next, the second distortion compensation simulation unit 115 performs distortion compensation on the test signal using different parameters than those used by the first distortion compensation simulation unit 113 (step S205). Steps S203, S204, and step S205 are not limited to being performed in this order; they may be performed in the reverse order, or almost simultaneously and in parallel.

[0061] Next, the differencer 116 calculates the error between the output signal value of the scaling unit 114 and the output signal value of the second distortion compensation simulation unit 115 (step S206). Next, the approximation error minimization unit 117 calculates the parameters of the second distortion compensation simulation unit 115 that minimize the error calculated by the differencer 116 (step S207). Subsequently, the output unit 118 outputs the parameters of the second strain compensation simulation unit 115, calculated by the approximation error minimization unit 117, to the strain compensation unit 12 as parameters for the strain compensation unit 12 (step S208).

[0062] As described above, according to this embodiment 1, the first distortion compensation simulation unit 113 performs distortion compensation processing on the signal obtained by multiplying the test signal by the backoff rate of PA 13, using parameters stored in the parameter storage unit 112. The second distortion compensation simulation unit 115 performs distortion compensation processing on the test signal using different parameters than those of the first distortion compensation simulation unit 113. The differencer 116 calculates the error between the value of the signal obtained by scaling the output signal of the first distortion compensation simulation unit 113 and the value of the output signal of the second distortion compensation simulation unit 115. The approximation error minimization unit 117 calculates the parameters of the second distortion compensation simulation unit 115 that minimize the calculated error. The output unit 118 outputs the calculated parameters of the second distortion compensation simulation unit 115 to the distortion compensation unit 12 as parameters for the distortion compensation unit 12.

[0063] This makes it possible to change the parameters of the distortion compensation unit 12 without providing a feedback circuit as shown in Figure 12. Furthermore, since there is no need to provide a feedback circuit, it is possible to avoid increasing the cost of the transmitter 10.

[0064] <Embodiment 2> Figure 7 is an enlarged view of the periphery of the first distortion compensation simulation unit 113 according to the above-described embodiment 1. As shown in Figure 7, in the embodiment 1 described above, the test signal is multiplied by the backoff rate in the multiplier 111 preceding the first distortion compensation simulation unit 113. Therefore, the operating point of the first distortion compensation simulation unit 113 is changed (=power scaling).

[0065] However, much of the signal processing for wireless communication, such as mobile communications, is performed using fixed-point arithmetic due to the requirements for operating speed and circuit size. Therefore, changing the operating point of the first distortion compensation simulation unit 113 may cause a loss of signal accuracy in the input and output stages of the first distortion compensation simulation unit 113. Specifically, when the backoff ratio γ is γ < 1 (i.e., when the power scaling is less than 1), the bit accuracy of the signal in the input and output stages of the first distortion compensation simulation unit 113 deteriorates by -log2(γ). As a result, the accuracy of the parameters of the strain compensation unit 12 calculated by the approximation error minimization unit 117 deteriorates, which in turn leads to a deterioration in the compensation accuracy of the strain compensation unit 12. This second embodiment is an example of suppressing the degradation of the parameter accuracy of the distortion compensation unit 12 caused by the degradation of the bit accuracy of the signal in the input and output stages of the first distortion compensation simulation unit 113.

[0066] The following describes an example of the configuration of the transmitter 10A according to this second embodiment, with reference to Figure 8. As shown in Figure 8, the transmitter 10A according to this second embodiment differs from the transmitter 10 according to the first embodiment described above in that the parameter changing device 11 is replaced with a parameter changing device 11A.

[0067] Furthermore, the parameter changing device 11A in this second embodiment differs from the parameter changing device 11 in the first embodiment described above in that a fixed-point conversion unit 119 is added before the output unit 118.

[0068] In this second embodiment, the multiplier 111, parameter storage unit 112, first distortion compensation simulation unit 113, scaling unit 114, second distortion compensation simulation unit 115, differencer 116, and approximation error minimization unit 117 perform the above-mentioned calculations using floating-point arithmetic. This makes it possible to suppress the degradation of the bit accuracy of the signals in the input and output stages of the first distortion compensation simulation unit 113.

[0069] Furthermore, since the approximation error minimization unit 117 also performs floating-point calculations, the parameters of the second distortion compensation simulation unit 115 calculated by the approximation error minimization unit 117 are parameters expressed in floating-point format. However, since the distortion compensation unit 12 is a component that processes signals for wireless communication, it performs distortion compensation processing using fixed-point arithmetic.

[0070] Therefore, in this second embodiment, the fixed-point conversion unit 119, which is located before the output unit 118, converts the parameters of the second distortion compensation simulation unit 115, which are expressed in floating-point format, into parameters expressed in fixed-point format. Then, the output unit 118 outputs the parameters of the second distortion compensation simulation unit 115, expressed in fixed-point format, to the distortion compensation unit 12 as parameters for the distortion compensation unit 12. As a result, the distortion compensation unit 12, which is performing fixed-point calculations, can use the parameters of the second distortion compensation simulation unit 115, thereby suppressing the deterioration of the compensation accuracy of the distortion compensation unit 12.

[0071] As described above, according to this second embodiment, the multiplier 111, parameter storage unit 112, first distortion compensation simulation unit 113, scaling unit 114, second distortion compensation simulation unit 115, differencer 116, and approximation error minimization unit 117 perform floating-point operations. The fixed-point conversion unit 119 converts the parameters of the second distortion compensation simulation unit 115, which are expressed in floating-point format, into parameters expressed in fixed-point format. The output unit 118 outputs the parameters of the second distortion compensation simulation unit 115, which are expressed in fixed-point format, to the distortion compensation unit 12 as parameters for the distortion compensation unit 12.

[0072] This makes it possible to suppress the degradation of the bit accuracy of the signals in the input and output stages of the first distortion compensation simulation unit 113, and also makes it possible to suppress the degradation of the compensation accuracy of the distortion compensation unit 12, as the distortion compensation unit 12 can use the parameters of the second distortion compensation simulation unit 115 through the conversion by the fixed-point conversion unit 119. Other effects are the same as those of Embodiment 1 described above.

[0073] <Embodiment 3> Although the transmitters 10 and 10A according to the embodiments 1 and 2 described above are provided with only one PA 13, this disclosure is also applicable to transmitters with a multi-stage PA configuration. This third embodiment is an example of applying the present disclosure to a transmitter equipped with a two-stage PA.

[0074] The following describes an example of the configuration of the transmitter 10B according to this third embodiment, with reference to Figure 9. As shown in Figure 9, the transmitter 10B according to this third embodiment includes a parameter changing device 11B, a downstream PA distortion compensation unit 12X, a downstream PA distortion compensation unit 12Y, a downstream PA 13X, and a downstream PA 13Y.

[0075] The subsequent PA distortion compensation unit 12X and the preceding PA distortion compensation unit 12Y correspond to the distortion compensation unit 12 according to Embodiment 1 described above. The subsequent PA 13X and the preceding PA 13Y correspond to the PA 13 according to Embodiment 1 described above.

[0076] The subsequent PA distortion compensation unit 12X performs distortion compensation processing on the input signal using parameters to compensate for the nonlinear distortion of the subsequent PA 13X. The input signal corresponds to the output signal of the signal processing unit 91 shown in Figure 12. The pre-stage PA distortion compensation unit 12Y performs distortion compensation processing on the input signal using parameters to compensate for the nonlinear distortion of the pre-stage PA 13Y.

[0077] The parameter changing device 11B is a device that uses the input back-off rates and test signals of the downstream PA 13X and upstream PA 13Y to change the parameters of the downstream PA distortion compensation unit 12X and the upstream PA distortion compensation unit 12Y, and outputs the changed parameters to the downstream PA distortion compensation unit 12X and the upstream PA distortion compensation unit 12Y.

[0078] The parameter changing device 11B includes a multiplier 111X, a parameter storage unit 112X, a first distortion compensation simulation unit 113X, a scaling unit 114X, a second distortion compensation simulation unit 115X, a differencer 116X, an approximation error minimization unit 117X, an output unit 118X, a parameter storage unit 112Y, a first distortion compensation simulation unit 113Y, a scaling unit 114Y, a second distortion compensation simulation unit 115Y, a differencer 116Y, an approximation error minimization unit 117Y, and an output unit 118Y.

[0079] The multiplier 111X corresponds to the multiplier 111 according to Embodiment 1 described above. The parameter storage units 112X and 112Y correspond to the parameter storage unit 112 according to Embodiment 1 described above. The first distortion compensation simulation units 113X and 113Y correspond to the first distortion compensation simulation unit 113 according to Embodiment 1 described above. The scaling units 114X and 114Y correspond to the scaling unit 114 according to Embodiment 1 described above. The second distortion compensation simulation units 115X and 115Y correspond to the second distortion compensation simulation unit 115 according to Embodiment 1 described above. The differencers 116X and 116Y correspond to the differencer 116 according to Embodiment 1 described above. The approximation error minimization units 117X and 117Y correspond to the approximation error minimization unit 117 according to Embodiment 1 described above. The output units 118X and 118Y correspond to the output unit 118 according to Embodiment 1 described above.

[0080] The multiplier 111X multiplies the input test signal by the backoff ratio of the input downstream PA13X and upstream PA13Y. The parameter storage unit 112X stores the parameters of the first distortion compensation simulation unit 113X.

[0081] The first distortion compensation simulation unit 113X performs distortion compensation processing on the output signal of the multiplier 111X using the parameters stored in the parameter storage unit 112X. The second distortion compensation simulation unit 115X performs distortion compensation processing on the input test signal using different parameters than those of the first distortion compensation simulation unit 113X.

[0082] The scaling unit 114X scales the output signal of the first distortion compensation simulation unit 113X. The differencer 116X calculates the error between the output signal value of the scaling unit 114X and the output signal value of the second distortion compensation simulation unit 115X.

[0083] The approximation error minimization unit 117X calculates the parameters of the second distortion compensation simulation unit 115X, which minimizes the error calculated by the differencer 116X. The output unit 118X outputs the parameters of the second distortion compensation simulation unit 115X, calculated by the approximation error minimization unit 117X, to the subsequent PA distortion compensation unit 12X as parameters for the subsequent PA distortion compensation unit 12X.

[0084] The parameter storage unit 112Y stores the parameters of the first distortion compensation simulation unit 113Y. The first distortion compensation simulation unit 113Y performs distortion compensation processing on the output signal of the first distortion compensation simulation unit 113X that is input to it, using the parameters stored in the parameter storage unit 112Y.

[0085] The second distortion compensation simulation unit 115Y performs distortion compensation processing on the output signal of the input scaling unit 114X using different parameters than those of the first distortion compensation simulation unit 113Y.

[0086] The scaling unit 114Y scales the output signal of the first distortion compensation simulation unit 113Y. The differencer 116Y calculates the error between the output signal value of the scaling unit 114Y and the output signal value of the second distortion compensation simulation unit 115Y.

[0087] The approximation error minimization unit 117Y calculates the parameters of the second distortion compensation simulation unit 115Y, which minimizes the error calculated by the differencer 116Y. The output unit 118Y outputs the parameters of the second distortion compensation simulation unit 115Y, calculated by the approximation error minimization unit 117Y, to the pre-stage PA distortion compensation unit 12Y as parameters for the pre-stage PA distortion compensation unit 12Y.

[0088] Since this third embodiment is configured as described above, it can be applied to a transmitter 10B equipped with a two-stage configuration of a downstream PA13X and a upstream PA13Y, and it is possible to change the parameters of the downstream PA distortion compensation unit 12X and the upstream PA distortion compensation unit 12Y. Other effects are the same as those of Embodiment 1 described above.

[0089] <Embodiment 4> The transmitters 10, 10A, and 10B according to embodiments 1, 2, and 3 described above were transmitters for wireless communication, but this disclosure is also applicable to transmitters for optical communication. Embodiment 4 is an example of applying the present disclosure to a transmitter for optical communications.

[0090] The following describes an example of the configuration of the transmitter 10C according to this embodiment 4, with reference to Figure 10. As shown in Figure 10, the transmitter 10C according to this embodiment 4 includes a parameter changing device 11C, a distortion compensation unit 12C, a driver amplifier (hereinafter referred to as "DA" as appropriate) 14, and an E / O (Electronic / Optical) conversion unit 15.

[0091] The parameter changing device 11C corresponds to the parameter changing devices 11 and 11A according to the embodiments 1 and 2 described above. The strain compensation unit 12C corresponds to the strain compensation unit 12 according to the embodiments 1 and 2 described above. The distortion compensation unit 12C performs distortion compensation processing on the input signal using parameters to compensate for the nonlinear distortion of DA14. The parameter change device 11C uses the input backoff rate and test signal of DA14 to change the parameters of the distortion compensation unit 12C, and outputs the changed parameters to the distortion compensation unit 12C.

[0092] DA14 amplifies the output signal of the distortion compensation unit 12C. The E / O conversion unit 15 converts the output signal of DA14 from an electrical signal to an optical signal, and transmits the converted signal to a receiver (not shown) via an optical component such as an optical fiber.

[0093] Since this embodiment 4 is configured as described above, it can be applied to the transmitter 10C for optical communication and the parameters of the distortion compensation unit 12C can be changed. Other effects are the same as those of Embodiment 1 described above.

[0094] <Embodiment 5> Referring to Figure 11, an example of the configuration of the parameter changing device 11D according to this embodiment 5 will be described. As shown in Figure 11, the parameter changing device 11D according to this embodiment 5 comprises a processor 1101 and a memory 1102.

[0095] The processor 1101 may be, for example, a microprocessor, an MPU (Micro Processing Unit), or a CPU (Central Processing Unit). The processor 1101 may include multiple processors.

[0096] Memory 1102 is composed of a combination of volatile and non-volatile memory. Memory 1102 may include storage located away from the processor 1101. In this case, the processor 1101 may access memory 1102 via an I(Input) / O(Output) interface, which is not shown.

[0097] The parameter changing devices 11, 11A, 11B, and 11C according to the embodiments 1, 2, 3, and 4 described above may have the hardware configuration shown in Figure 11. A program is stored in the memory 1102. This program includes a set of instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more of the functions described in the embodiments described above. The components of the parameter changing devices 11, 11A, 11B, and 11C described above may be realized by the processor 1101 reading and executing the program stored in the memory 1102. Furthermore, the storage function of the parameter changing devices 11, 11A, 11B, and 11C described above may be realized by the memory 1102.

[0098] Furthermore, the programs described above may be stored on non-temporary computer-readable media or tangible storage media. Examples, but not limited to, include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drives (SSDs) or other memory technologies, CD-ROMs, digital versatile discs (DVDs), Blu-ray® discs or other optical disc storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices. The programs may also be transmitted over temporary computer-readable media or communication media. Examples, but not limited to, include electrical, optical, acoustic, or other forms of propagating signals.

[0099] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be understood by those skilled in the art within the scope of the present disclosure. For example, each of the embodiments described above may be applied in combination of any two or more embodiments. [Explanation of symbols]

[0100] 10, 10A, 10B, 10C Transmitter 11, 11A, 11B, 11C, 11D Parameter change device 110 Input Section 111,111X multiplier 112,112X,112Y parameter storage unit 113,113X,113Y First distortion compensation simulation section 114,114X,114Y scaling section 115, 115X, 115Y Second distortion compensation simulation section 116,116X,116Y differentiator 117,117X,117Y Approximation error minimization part 118,118X,118Y output section 119 Fixed-point conversion section 1101 Processor 1102 memory 12,12C Distortion compensation section 12X Post-stage PA distortion compensation section 12Y Front stage PA distortion compensation section 13 PA 13X rear PA 13Y Front stage PA 14 DA 15 E / O conversion section

Claims

1. A parameter changing device for changing the parameters of a distortion compensation unit that performs distortion compensation processing to compensate for the nonlinear distortion of an amplifier, A multiplier that multiplies the input test signal by the input backoff rate, A first distortion compensation simulation unit performs distortion compensation processing on the output signal of the multiplier using parameters stored in a parameter storage unit, A scaling unit that scales the output signal of the first distortion compensation simulation unit, A second distortion compensation simulation unit performs distortion compensation processing on the input test signal using parameters different from those of the first distortion compensation simulation unit, A differencer that calculates the error between the output signal value of the scaling unit and the output signal value of the second distortion compensation simulation unit, An approximation error minimization unit calculates the parameters of the second strain compensation simulation unit that minimize the error calculated by the differencer, An output unit that outputs the parameters of the second strain compensation simulation unit, calculated by the approximation error minimization unit, to the strain compensation unit as parameters of the strain compensation unit, A parameter changing device equipped with the following features.

2. It further includes a fixed-point conversion unit, The multiplier, the first distortion compensation simulation unit, the second distortion compensation simulation unit, the scaling unit, the differencer, and the approximation error minimization unit perform floating-point operations. The fixed-point conversion unit converts the parameters of the second distortion compensation simulation unit, which are expressed in floating-point format, into parameters expressed in fixed-point format. The output unit outputs the parameters of the second distortion compensation simulation unit, which have been converted by the fixed-point conversion unit and expressed in fixed-point format, to the distortion compensation unit as parameters of the distortion compensation unit. The parameter changing device according to claim 1.

3. It further includes an input section, The amplifier, the distortion compensation unit, and the parameter changing device are provided in the transmitter. The input unit determines the backoff rate based on the communication distance between the transmitter and the receiver and the communication quality of the receiver, inputs the determined backoff rate together with the test signal to the multiplier, and inputs the test signal to the second distortion compensation simulation unit. The parameter changing device according to claim 1.

4. The first strain compensation simulation unit and the second strain compensation simulation unit perform the same strain compensation processing as the strain compensation unit, except for the parameters. The parameter changing device according to claim 1.

5. The aforementioned distortion compensation unit, the first distortion compensation simulation unit, and the second distortion compensation simulation unit are composed of memory polynomials. The parameter changing device according to claim 1.

6. The distortion compensation unit, the first distortion compensation simulation unit, and the second distortion compensation simulation unit are configured by a neural network. The parameter changing device according to claim 1.

7. The aforementioned amplifier, The distortion compensation unit performs distortion compensation processing to compensate for the nonlinear distortion of the amplifier, A parameter changing device according to any one of claims 1 to 6, comprising: a parameter changing device for changing the parameters of the strain compensation unit; A transmitter equipped with the following features.

8. A parameter changing method using a parameter changing device for changing the parameters of a distortion compensation unit that performs distortion compensation processing to compensate for the nonlinear distortion of an amplifier, Inputting the backoff rate and test signal, Multiplying the test signal by the backoff rate, In the first distortion compensation simulation unit, distortion compensation processing is performed on the signal obtained by the multiplication using the parameters stored in the parameter storage unit. The output signal of the first distortion compensation simulation unit is scaled, In the second distortion compensation simulation unit, distortion compensation processing is performed on the test signal using parameters different from those used in the first distortion compensation simulation unit. The error between the value of the signal obtained by the scaling and the value of the output signal of the second distortion compensation simulation unit is calculated. To calculate the parameters of the second strain compensation simulation unit that minimize the calculated error, The parameters of the second strain compensation simulation unit calculated above are output to the strain compensation unit as parameters of the strain compensation unit. Methods for changing parameters, including those mentioned above.

9. A program to be executed by a computer to change the parameters of a distortion compensation section that performs distortion compensation processing to compensate for the nonlinear distortion of an amplifier, Inputting the backoff rate and test signal, Multiplying the test signal by the backoff rate, In the first distortion compensation simulation unit, distortion compensation processing is performed on the signal obtained by the multiplication using the parameters stored in the parameter storage unit. The output signal of the first distortion compensation simulation unit is scaled, In the second distortion compensation simulation unit, distortion compensation processing is performed on the test signal using parameters different from those used in the first distortion compensation simulation unit. The error between the value of the signal obtained by the scaling and the value of the output signal of the second distortion compensation simulation unit is calculated. To calculate the parameters of the second strain compensation simulation unit that minimize the calculated error, The parameters of the second strain compensation simulation unit calculated above are output to the strain compensation unit as parameters of the strain compensation unit. A program that includes this.

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