Wireless communication device, method, and program

Abstract

To appropriately compensate for nonlinear characteristics of a power amplifier.SOLUTION: A wireless communication device (20) includes: a power amplifier (12) that amplifies and outputs the power of a signal; and a distortion compensation unit (1) that compensates for distortion due to nonlinear characteristics of the power amplifier based on an immediately preceding signal off time length.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a wireless communication device, method, and program.

Background Art

[0002] In mobile communications, a frequency division duplex (FDD) method for simultaneous transmission and reception and a time division duplex (TDD) method for performing transmission and reception in a time division manner to improve frequency utilization efficiency are adopted. In the case of the TDD method, the transmission time and the reception time are switched and operated at high speed. Generally, during the reception time, the power amplifier is stopped to suppress power consumption, and at the same time, unnecessary leakage power is not generated from the device during the reception time (to achieve the standard of the OFF-time leakage power attenuation ratio). Therefore, depending on the time responsiveness of the power amplifier, the non-linear characteristics (AM (Amplitude Modulation)-AM characteristics, AM-PM (Phase Modulation) characteristics) of the power amplifier may differ at the timing immediately after the start of transmission and other timings.

[0003] On the other hand, as a distortion compensation technique widely adopted in wireless base station devices for mobile communications, there is a digital predistortion (DPD) method. Distortion compensation by the digital predistortion method compensates for non-linear distortion generated in a power amplifier. Regarding this technology, Patent Document 1 discloses a technique for detecting multi-valued phase modulation information and switching a look-up table (LUT) between the front stage and the rear stage of a frame based on the detected information.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] However, in related technologies, such as power amplifiers using gallium nitride (GaN) transistors, the nonlinear characteristics immediately after the signal is turned ON (immediately after the signal is switched from OFF to ON) differ significantly from the average nonlinear characteristics that the DPD is trying to compensate for. When the timing of the ON and OFF states of the signal changes dynamically, the nonlinear characteristics immediately after the signal is turned ON (immediately after wireless transmission begins) cannot be adequately compensated. As a result, wireless characteristics such as ACLR (Adjacent Channel Leakage Ratio) and EVM (Error Vector Magnitude) deteriorate immediately after the start of transmission.

[0006] The purpose of this disclosure is to provide a technology that can appropriately compensate for the nonlinear characteristics of a power amplifier, in view of the above-mentioned problems. [Means for solving the problem]

[0007] A first aspect of the present disclosure provides a wireless communication device having a power amplifier that amplifies and outputs the power of a signal, and a distortion compensation unit that compensates for distortion due to the nonlinear characteristics of the power amplifier based on the length of the preceding signal OFF time.

[0008] Furthermore, a second aspect of the present disclosure provides a method for a wireless communication device to compensate for distortion due to the nonlinear characteristics of a power amplifier that amplifies and outputs the power of a signal based on the previous signal OFF time length.

[0009] Furthermore, in a third aspect relating to this disclosure, a program is provided that causes a computer to perform a process to compensate for distortion due to the nonlinear characteristics of a power amplifier that amplifies and outputs the power of a signal, based on the previous signal OFF time length. [Effects of the Invention]

[0010] From one perspective, this allows for appropriate compensation of the nonlinear characteristics of the power amplifier. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows an example of the configuration of a wireless communication device according to the embodiment. [Figure 2] This figure shows an example of the nonlinear characteristics of a power amplifier immediately after the signal is turned ON due to the current collapse phenomenon, and while the ON state continues. [Figure 3] This figure shows an example of the nonlinear characteristics of a power amplifier immediately after the signal is turned ON due to the current collapse phenomenon, and while the ON state continues. [Figure 4] This figure shows an example of the ON / OFF timing of the TDD method, immediately after the signal is turned ON, and when it is stable. [Figure 5] This flowchart shows an example of distortion compensation processing for a wireless communication device according to the embodiment. [Figure 6] This figure shows an example of the configuration of the strain compensation unit according to the embodiment. [Figure 7] This figure shows an example of a method for determining the distortion compensation coefficient and correction coefficient according to the signal OFF time length immediately preceding the embodiment. [Figure 8] This figure shows an example of the time change of the correction coefficient α according to the embodiment. [Figure 9] This figure shows an example of selecting a distortion compensation coefficient and a correction coefficient according to the signal OFF time length immediately preceding the embodiment. [Figure 10] This figure shows an example of selecting a distortion compensation coefficient and a correction coefficient according to the signal OFF time length immediately preceding the embodiment. [Figure 11] This figure shows an example of a computer configuration when at least a part of the wireless communication device according to the embodiment is implemented using a computer and a program. [Modes for carrying out the invention]

[0012] The principles of the present disclosure will be described with reference to some exemplary embodiments. These embodiments are described for illustrative purposes only, and it should be understood that they are intended to assist those skilled in the art in understanding and implementing the present disclosure without suggesting any limitations on the scope of the present disclosure. The disclosure described herein may be implemented in various ways other than those described below. In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Embodiments of the present disclosure will be described below with reference to the drawings.

[0013] <Configuration> FIG. 1 is a diagram showing an example of the configuration of a wireless communication device 20 according to an embodiment. In the example of FIG. 1, the wireless communication device 20 according to the embodiment includes a distortion compensation unit 1, an orthogonal modulation unit 9, a DAC (Digital-to-Analog Converter) 10, a frequency converter 11, a power amplifier 12, a directional coupler 13, a frequency converter 14, an ADC (Analog-to-Digital Converter) 15, an orthogonal demodulation unit 16, a control unit 17, and a delay circuit 18.

[0014] The distortion compensation unit 1 compensates for distortion due to the non-linear characteristics of the power amplifier 12 when starting wireless transmission (when the signal becomes ON), etc., based on the immediately preceding signal OFF time length (the length of the section that was the signal OFF when the signal changed from OFF to ON). The distortion compensation unit 1 may compensate for the distortion due to the non-linear characteristics of the power amplifier 12 when the immediately preceding signal OFF time length is the first time length, based on a distortion compensation coefficient representing the inverse characteristics of the non-linear characteristics of the power amplifier 12, which is calculated based on the transmission signal input to the power amplifier 12 and the feedback signal obtained by feeding back the signal output from the power amplifier 12 when the signal OFF time length was previously the first time length.

[0015] The distortion compensation unit 1 may perform compensation based on a continuously changing distortion compensation coefficient. In this case, the distortion compensation unit 1 may perform compensation based on the first distortion compensation coefficient during a first period from the time when the signal becomes ON. Then, the distortion compensation unit 1 may perform compensation based on a distortion compensation coefficient that changes from the first distortion compensation coefficient to the second distortion compensation coefficient according to the passage of time during a period from the first period to the second period. Then, the distortion compensation unit 1 may perform compensation based on the second distortion compensation coefficient during a second period in which the non-linear characteristics of the power amplifier 12 are different from those in the first period.

[0016] In the example of FIG. 1, the distortion compensation unit 1 is implemented by a circuit such as an FPGA (Field Programmable Gate Array) and an ASIC (Application Specific Integrated Circuit). In the example of FIG. 1, the distortion compensation unit 1 includes a power calculation unit 2, a power threshold determination unit 3, a correction coefficient data memory 4, a distortion compensation coefficient data memory 5, distortion compensation coefficient LUTs (reference tables) 6a, 6b, 6c,... (hereinafter, simply referred to as "distortion compensation coefficient LUT 6" when there is no need to distinguish).), a correction coefficient calculation unit 7, and a distortion compensation calculation unit 8.

[0017] The power calculation unit 2 calculates the average power and the power per sample of the digital quadrature baseband signals I and Q. The power threshold determination unit 3 counts the duration of time during which the power per sample continuously falls below the threshold and the duration of time during which the power per sample continuously exceeds the threshold.

[0018] The correction coefficient data memory 4 stores the correction coefficient calculated by the control unit 17 and the time change of the correction coefficient. Further, the correction coefficient data memory 4 selects a correction coefficient according to the duration of time during which the power continuously falls below the threshold counted by the power threshold determination unit 3, changes the correction coefficient according to the duration of time during which the power continuously exceeds the threshold, and outputs the result.

[0019] The distortion compensation coefficient data memory 5 stores distortion compensation coefficient LUT 6 corresponding to the power of the digital quadrature baseband signals I and Q, and switches the connection between the distortion compensation coefficient LUT 6 and the correction coefficient calculation unit 7 according to the time length below the threshold determined by the power threshold determination unit 3.

[0020] The strain compensation coefficient LUT6 is a LUT that stores the strain compensation coefficient calculated by the control unit 17. The strain compensation coefficient LUT6 outputs the strain compensation coefficient according to the power calculated by the power calculation unit 2.

[0021] The correction coefficient calculation unit 7 performs a correction calculation based on the distortion compensation coefficient read from the distortion compensation coefficient LUT 6 selected by the distortion compensation coefficient data memory 5 and the correction coefficient selected by the correction coefficient data memory 4, and outputs it to the distortion compensation calculation unit 8.

[0022] The distortion compensation calculation unit 8 performs distortion compensation calculations on the digital quadrature baseband signals I and Q based on the distortion compensation coefficients CI and CQ from the correction coefficient calculation unit 7. The quadrature modulation unit 9 quadrature modulates the digital quadrature baseband signals I' and Q', which have undergone distortion compensation calculations in the distortion compensation calculation unit 8, and converts them into digital IF signals.

[0023] The DAC10 converts the digital IF signal converted by the quadrature modulation unit 9 from a digital signal to an analog signal, generating an analog IF (Intermediate Frequency) signal. The frequency converter 11 upconverts the analog IF signal converted by the DAC10 to an RF (Radio Frequency) signal. (Regarding power amplifier 12)

[0024] The power amplifier 12 amplifies and outputs the power of the RF signal. The RF signal is input to the power amplifier 12 when data is transmitted wirelessly from the wireless communication device 20. Therefore, the RF signal input to the power amplifier 12 is turned ON only during the period in which data is actually transmitted within the TDD transmission period. The wireless communication device 20 may control the ON / OFF state of the RF signal to the power amplifier 12 according to the amount of data to be transmitted within the TDD transmission period. This technology is also called, for example, microsleep, and can reduce power consumption. The power amplifier 12 may have a transistor made of gallium nitride (GaN).

[0025] In recent years, power amplifiers 12 for mobile communication base stations and the like have frequently employed gallium nitride (GaN) transistors for high output and high efficiency. However, GaN transistors have the characteristic of exhibiting a current collapse phenomenon. The current collapse phenomenon occurs when electrons are trapped at points where a strong electric field is applied, such as between the source and drain, between the source and gate, and between the drain and the substrate, while the device is in the off state. As the amount of trapped electrons changes depending on the signal OFF time length, the on resistance of the device and the time it takes for the trapped electrons to be released change.

[0026] Figures 2 and 3 illustrate examples of the nonlinear characteristics of a power amplifier immediately after signal ON (start of wireless transmission) due to the current collapse phenomenon and during a sustained ON state (hereinafter referred to as "stable state" as appropriate). Figure 1 shows examples of values ​​201 during the stable state, 202 immediately after ON when the preceding OFF time was relatively short, and 203 immediately after ON when the preceding OFF time was relatively long, with the horizontal axis representing the input level and the vertical axis representing the gain. Figure 2 shows examples of values ​​211 during the stable state, 212 immediately after ON when the preceding OFF time was relatively short, and 213 immediately after ON when the preceding OFF time was relatively long, with the horizontal axis representing the input level and the vertical axis representing the phase. As shown in Figures 2 and 3, the nonlinear characteristics of the power amplifier differ significantly between the state immediately after signal ON and the stable state, depending on the presence or absence of the current collapse phenomenon.

[0027] Figure 4 shows an example of the ON / OFF timing of a TDD (Tunnel Deposition) system, immediately after signal ON, and during stabilization. In the example in Figure 4, t0 is the point at which the signal turns ON, t1 is the point immediately after signal ON, t2 is the point during stabilization, and t3 is the point at which the signal changes from ON to OFF. For example, in the OFDM (Orthogonal Frequency Division Multiplex) modulation signal used in 4G and 5G downlink connections, the change in the nonlinear characteristics of a certain power amplifier is approximately 4 Symbols (≒256us) from t0 to t1, 5 Symbols (≒327us) from t0 to t2, and 1 Symbol (≒71us) from t1 to t2. Note that t1 and t2 will differ depending on the type of power amplifier 12 and the length of the signal OFF time immediately before signal ON.

[0028] In 4G (fourth-generation mobile communication system), the DL (downlink) / UL (uplink) switching pattern has a fixed repeating period of 10 msec. Therefore, the TDD timing is a known value, and the signal OFF time is the same in every cycle, so the degree of the current collapse phenomenon is the same in every cycle, and the nonlinearity immediately after the signal ON is also the same in every cycle.

[0029] On the other hand, it has been indicated that Semi-static TDD and Dynamic TDD will be realized in the future for 5G (5th generation mobile communication system) NR (New Radio). With Semi-static TDD, the TDD timing can be set for each frame in units of 0.5, 0.625, 1, 1.25, 2, 2.5, 5, and 10 msec. With Dynamic TDD, DL / UL can be flexibly switched on a symbol-by-symbol basis as needed, without setting the repetition period of the DL / UL switching pattern. As a result, when the TDD timing changes dynamically, the length of the preceding signal OFF time changes each time, and the degree of the current collapse phenomenon also changes each time, so the change in the nonlinearity of the power amplifier 12 immediately after the signal ON is also different each time.

[0030] The directional coupler 13 feeds back a portion of the output of the power amplifier 12 to the frequency converter 14. The frequency converter 14 down-converts the RF signal fed back by the directional coupler 13 into an analog IF signal. The ADC 15 converts the analog IF signal down-converted by the frequency converter 14 from an analog signal to a digital signal and generates a digital IF signal.

[0031] The quadrature demodulation unit 16 quadrature demodulates the digital IF signal converted by the ADC 15 and converts it into digital quadrature baseband feedback signals Ib and Qb. The delay circuit 18 delays the digital quadrature baseband signals I and Q for a set time and outputs them to the control unit 17.

[0032] The control unit 17 calculates the delay time between the transmission signal and feedback signal input to the control unit 17, that is, the digital quadrature baseband signals Ia and Qa and the digital quadrature baseband feedback signals Ib and Qb, and sets this delay time in the delay circuit 18. The control unit 17 also calculates a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier 12 tailored to the sample, and updates the distortion compensation coefficient stored in the distortion compensation coefficient LUT6 that matches each condition with the calculated distortion compensation coefficient.

[0033] Here, the control unit 17 may, for example, compare the amplitude and phase of the transmission signal input to the power amplifier 12 and the feedback signal obtained by feeding back the signal output from the power amplifier 12 as digital signals, and calculate a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier 12 based on the comparison result. The method for calculating the distortion compensation coefficient in this disclosure is not limited to this, and other methods may be used. The control unit 17 also updates the correction coefficient and the change time of the correction coefficient according to each condition.

[0034] <Processing (Action)> Next, an example of distortion compensation processing of the wireless communication device 20 according to the embodiment will be described with reference to Figures 5 to 10. Figure 5 is a flowchart showing an example of distortion compensation processing of the wireless communication device 20 according to the embodiment. Figure 6 is a diagram showing an example of the configuration of the distortion compensation unit 1 according to the embodiment. Figure 7 is a diagram showing an example of a method for determining the distortion compensation coefficient and correction coefficient according to the immediately preceding signal OFF time length according to the embodiment. Figure 8 is a diagram showing an example of the time change of the correction coefficient α according to the embodiment. Figure 9 is a diagram showing an example of selecting the distortion compensation coefficient and correction coefficient according to the immediately preceding signal OFF time length according to the embodiment. Figure 10 is a diagram showing an example of selecting the distortion compensation coefficient and correction coefficient according to the immediately preceding signal OFF time length according to the embodiment. Note that the wireless communication device 20 may perform the following processing at each point in time while communicating (transmitting or receiving) using the TDD method, for example.

[0035] In step S1, the power calculation unit 2 calculates the power of the digital quadrature baseband signals I and Q. Subsequently, the power threshold determination unit 3 determines the previous signal OFF time length, the signal ON time, and the time when the signal stabilized, based on the measurement results of the power calculation unit 2 (step S2). Here, the power threshold determination unit 3 may, for example, calculate the signal OFF time length as the length of time during which the power of each measured sample has continuously been below a threshold (a power value considered to be signal OFF; for example, 0W). The power threshold determination unit 3 may, for example, determine the time when the length of time during which the signal has continuously exceeded the threshold exceeds a specific length of time as the time when the signal stabilized.

[0036] Next, the correction coefficient data memory 4 changes (determines) the correction coefficient α at a pre-stored timing according to the time length determined by the power threshold determination unit 3, and the distortion compensation coefficient data memory 5 selects the distortion compensation coefficient LUT 6 according to the time length determined by the power threshold determination unit 3 (step S3). Next, the distortion compensation coefficient associated with the power value calculated by the power calculation unit 2 is read from the distortion compensation coefficient LUT 6 (step S4). Next, the correction coefficient calculation unit 7 determines the distortion compensation coefficients CI and CQ (step S5).

[0037] The correction coefficient data memory 4, the distortion compensation coefficient data memory 5, and the correction coefficient calculation unit 7 may compensate based on the first distortion compensation coefficient during the first period from the moment the signal is turned ON. Then, during the period from the first period to the second period, compensation may be based on a distortion compensation coefficient that changes from the first distortion compensation coefficient to the second distortion compensation coefficient according to the passage of time. Furthermore, during the second period, when the nonlinear characteristics of the power amplifier 12 differ from those of the first period, compensation may be based on the second distortion compensation coefficient.

[0038] In the example shown in Figure 6, the distortion compensation coefficient LUT6a stores a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier 12 immediately after the signal is turned on, when the preceding signal OFF time length is a specific length. The distortion compensation coefficient LUT6b stores a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier 12 when it is stable. Note that the initial value of the distortion compensation coefficient recorded in the distortion compensation coefficient LUT6 may be set in advance.

[0039] Figure 7 shows an example of how to select the distortion compensation coefficient LUT6 and the correction coefficient according to the previous signal OFF time length, in the case of the circuit configuration of the distortion compensation unit 1 in Figure 6. In the interval (period) 721 after the power 701 becomes less than or equal to the threshold 711, the distortion compensation coefficient LUT6a, the distortion compensation coefficient LUT6b, and the correction coefficient α0 are selected.

[0040] In section 722, following section 721, distortion compensation coefficients LUT6c, LUT6b, and correction coefficient α1 are selected. In section 723, following section 722, distortion compensation coefficients LUT6d, LUT6b, and correction coefficient α2 are selected. If the power exceeds the threshold during this process, the selected distortion compensation LUT and correction coefficient will remain in place until the power falls below the threshold of 711. By selecting the distortion compensation coefficient and correction coefficient when the signal is OFF in this way, the distortion compensation coefficient LUT6 can be switched continuously (smoothly) without any discontinuities.

[0041] The correction coefficient calculation unit 7 uses the following formulas to determine the distortion compensation coefficients: CIa and CQa are read from the distortion compensation coefficient LUT 6a; CIb and CQb are read from the distortion compensation coefficient LUT 6b; CI and CQ are the distortion compensation coefficients after the correction calculation; and α is the correction coefficient read from the correction coefficient data memory 4. In this case, the correction coefficient calculation unit 7 may perform the correction calculation using the following formulas (1) and (2). CI = α×CIa+(1-α)×CIb (1) CQ = α×CQa+(1-α)×CQb (2)

[0042] Here, the correction coefficient α is a coefficient that changes with time, and may change as shown in Figure 8, for example. In the example in Figure 8, in the interval from t0 to t1 in Figure 4, α = 1.0, in the interval from t1 to t2, α changes stepwise (continuously, over time) from 1.0 to 0.0, and in the interval from t2 to t3, α = 0.0.

[0043] As a result, the distortion compensation coefficients CI and CQ after the correction calculation are given by equation (3) below for the interval from t0 to t1, by equation (4) below for the interval from t1 to t2, and by equation (5) below for the interval from t2 to t3. CI = CIa, CQ = CQa ···(3) CI = α×CIa+(1-α)×CIb, CQ = α×CQa+(1-α)×CQb (4) CI = CIb, CQ = CQb ···(5)

[0044] This makes it possible to apply distortion compensation coefficients that correspond to the nonlinear characteristics of each time period. Furthermore, even if the distortion compensation coefficient LUT6a and distortion compensation coefficient LUT6b are completely different LUTs, the LUT switching is weighted by an averaging process using a correction coefficient, so there is no abrupt change in the compensation coefficient associated with LUT switching. This reduces signal discontinuity and suppresses spectrum degradation and unwanted spurious signals.

[0045] Figure 9 shows an example of selecting a distortion compensation coefficient and a correction coefficient according to the duration of the preceding signal OFF time. In the example in Figure 9, in section 912 immediately after the signal ON, the distortion compensation coefficient is the value recorded in the distortion compensation coefficient LUT6a, which corresponds to the duration of section 911 where the power is below the threshold. Furthermore, in section 913 from section 912 to the stable section 914, the distortion compensation coefficient is continuously switched from the value of the distortion compensation coefficient LUT6a to the value of the distortion compensation coefficient LUT6b. In section 914, the stable section, the distortion compensation coefficient is the value recorded in the distortion compensation coefficient LUT6b.

[0046] Furthermore, in section 922 immediately after the signal is turned ON, the distortion compensation coefficient is the value recorded in the distortion compensation coefficient LUT6c, which corresponds to the duration of section 921 where the power is below the threshold. Also, in section 923 from section 922 to the stable section 924, the distortion compensation coefficient is continuously switched from the value of the distortion compensation coefficient LUT6c to the value of the distortion compensation coefficient LUT6b. In section 924 during the stable period, similar to section 914, the distortion compensation coefficient is the value recorded in the distortion compensation coefficient LUT6b.

[0047] Furthermore, if the nonlinearity of the power amplifier 12 differs in each stable section, a distortion compensation coefficient LUT6 may be used for each section as shown in Figure 10. In the example in Figure 10, in section 922 immediately after the signal is turned ON, the distortion compensation coefficient is the value recorded in the distortion compensation coefficient LUT6c corresponding to the time length of section 921 where the power is below the threshold. Also, in section 1023 from section 922 to the first stable section 1024, the distortion compensation coefficient is continuously switched from the value of the distortion compensation coefficient LUT6c to the value of the distortion compensation coefficient LUT6d. In addition, in the first stable section 1024, the distortion compensation coefficient is the value recorded in the distortion compensation coefficient LUT6d.

[0048] Furthermore, in section 1025, from section 1024 to the stable second section 1026, the strain compensation coefficient is continuously switched from the value of the strain compensation coefficient LUT6d to the value of the strain compensation coefficient LUT6e. Also, in the stable second section 1026, the value recorded in the strain compensation coefficient LUT6e is used as the strain compensation coefficient. Furthermore, in section 1027, from section 1026 to the stable third section 1028, the strain compensation coefficient is continuously switched from the value of the strain compensation coefficient LUT6e to the value of the strain compensation coefficient LUT6f. Also, in the stable third section 1028, the value recorded in the strain compensation coefficient LUT6f is used as the strain compensation coefficient.

[0049] Furthermore, the correction coefficient calculation unit 7 is not limited to the above equations (1) and (2), but may continuously change CI and CQ using, for example, the mean square method.

[0050] Next, the distortion compensation calculation unit 8 performs distortion compensation calculations on the digital quadrature baseband signals I and Q based on the distortion compensation coefficients CI and CQ (step S6). This compensates for distortion due to the nonlinear characteristics of the power amplifier 12 based on the previous signal OFF time length. Furthermore, even if, for example, the nonlinear characteristics of the power amplifier 12 differ significantly only immediately after the TDD signal is ON, it is possible to suppress spectrum degradation and unwanted spurious signals, enabling accurate distortion compensation throughout the entire transmission section. In addition, in Semi-static TDD and Dynamic TDD, where the TDD pattern changes dynamically, accurate distortion compensation is possible even if the nonlinear characteristics of the power amplifier immediately after the TDD signal is ON differ significantly each time the signal is ON.

[0051] (Regarding the update of the data for the distortion compensation coefficient LUT6) The control unit 17 may calculate a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier 12 for a specific signal OFF time length, based on the transmission signal input to the power amplifier 12 at a specific signal OFF time length and the feedback signal obtained by feeding back the signal output from the power amplifier 12. The control unit 17 may then record the calculated distortion compensation coefficient in the distortion compensation coefficient LUT 6 for that specific signal OFF time length. This allows, for example, the distortion compensation coefficient LUT 6 corresponding to each signal OFF time length to be updated based on actual measured values, thereby achieving more accurate distortion compensation.

[0052] For example, suppose that the distortion compensation coefficient LUT6a stores a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier 12 immediately after signal ON, when the signal OFF time length immediately before signal ON in the TDD method is 2ms. Also, suppose that the distortion compensation coefficient LUT6b stores a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier 12 when it is stable.

[0053] In this case, the control unit 17 may calculate a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier 12 in the section immediately after the signal is turned on, based on the transmitted signal and feedback signal in the section immediately after the signal is turned on, assuming that the signal OFF section immediately before the signal is turned on is 2ms. The control unit 17 may then update the distortion compensation coefficient of the distortion compensation coefficient LUT 6a with the calculated value.

[0054] Furthermore, the control unit 17 may calculate a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier 12 during the stable period, based on the transmitted signal and feedback signal during the stable period, when the signal OFF period immediately before the signal ON is 2ms. The control unit 17 may then update the distortion compensation coefficient of the distortion compensation coefficient LUT6b with the calculated value.

[0055] <Variation> Figure 11 shows an example of the configuration of a computer 100 when at least a part of the wireless communication device 20 according to the embodiment (for example, the strain compensation unit 1) is implemented by a computer and a program. In the example of Figure 11, the computer 100 includes a processor 101, memory 102, and a communication interface 103. These parts may be connected by a bus or the like. The memory 102 stores at least a part of the program 104. The communication interface 103 includes an interface necessary for communication with other network elements.

[0056] When program 104 is executed through the cooperation of the processor 101 and memory 102, etc., computer 100 performs at least some of the processing of embodiments of the present disclosure. Memory 102 may be of any type suitable for a local technology network and may be implemented using any suitable data storage technology, such as non-temporary computer-readable storage media, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, etc. Although only one memory 102 is shown for computer 100, computer 100 may have several physically different memory modules. Processor 101 may be of any type suitable for a local technology network and may include one or more general-purpose computers, dedicated computers, microprocessors, digital signal processors (DSPs), and, in non-limited examples, processors based on multicore processor architectures. Computer 100 may have multiple processors, such as application-specific integrated circuit chips that are time-dependent to a clock that synchronizes the main processor.

[0057] Embodiments of the present disclosure may be implemented in hardware or in dedicated circuitry, software, logic, or any combination thereof. Some embodiments may be implemented in hardware, while others may be implemented in firmware or software that can be executed by a controller, microprocessor, or other computing device.

[0058] This disclosure also provides at least one computer program product tangibly stored on a non-temporary computer-readable storage medium. The computer program product includes computer-executable instructions, such as instructions contained in a program module, and is executed on a device on a target real or virtual processor to perform the processes or methods of this disclosure. The program module includes routines, programs, libraries, objects, classes, components, data structures, etc., that perform a specific task or implement a specific abstract data type. The functionality of the program module may be combined or divided among the program module as desired in various embodiments. The machine-executable instructions of the program module can be executed on a local or distributed device. On a distributed device, the program module can reside on both local and remote storage media.

[0059] Program code for performing the methods of this disclosure may be written in any combination of one or more programming languages. These program codes are provided to a processor or controller of a general-purpose computer, a dedicated computer, or other programmable data processing device, and when the program code is executed by the processor or controller, the functions / operations in the flowchart and / or block diagrams to be implemented are performed. The program code runs entirely on the machine, partly on the machine, partly as a standalone software package, partly on the machine, partly on a remote machine, or entirely on a remote machine or server.

[0060] The program code described above may be embodied in a machine-readable medium, which may be any tangible medium that can contain or store programs used by or in connection with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. The machine-readable medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination thereof. More specific examples of machine-readable storage media include one or more wires, portable computer diskettes, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or electrical connections having a suitable combination of the above.

[0061] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention.

[0062] Some or all of the above embodiments may also be described as follows, but are not limited to the following: (Note 1) A power amplifier that amplifies the power of a signal and outputs it, A distortion compensation unit that compensates for distortion due to the nonlinear characteristics of the power amplifier based on the previous signal OFF time length, A wireless communication device having the following features. (Note 2) The aforementioned distortion compensation unit is Based on a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier, calculated based on the transmitted signal input to the power amplifier and the feedback signal obtained by feeding back the signal output from the power amplifier when the previous signal OFF time length was the first time length, the distortion due to the nonlinear characteristics of the power amplifier when the immediately preceding signal OFF time length was the first time length is compensated. The wireless communication device described in Appendix 1. (Note 3) The aforementioned distortion compensation unit is Based on the previous signal OFF time length, the distortion due to the nonlinear characteristics of the power amplifier when starting wireless transmission is compensated. Wireless communication device as described in Appendix 1 or 2. (Note 4) The power amplifier has a transistor made of gallium nitride (GaN). Wireless communication device as described in Appendix 1 or 2. (Note 5) The aforementioned distortion compensation unit is During the first period from the moment the signal is turned ON, compensation is performed based on the first distortion compensation coefficient. During the period from the first period to the second period, compensation is performed based on a strain compensation coefficient that changes from the first strain compensation coefficient to the second strain compensation coefficient according to the passage of time. The nonlinear characteristics of the power amplifier are compensated based on the second distortion compensation coefficient during the second period, which differs from those of the first period. Wireless communication device as described in Appendix 1 or 2. (Note 6) Wireless communication device, Based on the previous signal OFF time, the power amplifier amplifies the signal power and outputs it, compensating for the distortion caused by the nonlinear characteristics of the power amplifier. method. (Note 7) A program that instructs a computer to perform a process to compensate for distortion caused by the nonlinear characteristics of a power amplifier that amplifies and outputs the signal power, based on the length of the previous signal OFF time. [Explanation of symbols]

[0063] 20 Wireless communication devices 1 Distortion compensation section 2 Power calculation section 3 Power threshold determination unit 4. Correction coefficient data memory 5. Distortion Compensation Coefficient Data Memory 7. Correction coefficient calculation unit 8 Distortion compensation calculation section 9. Orthogonal modulation section 10 DAC 11 Frequency Converter 12 Power Amplifier 13 Directional coupler 14 Frequency Converters 15 ADC 16. Orthogonal demodulation unit 17 Control Unit 18 Delay Circuit

Claims

1. A power amplifier that amplifies the power of a signal and outputs it, It includes a distortion compensation unit that compensates for distortion due to the nonlinear characteristics of the power amplifier based on the previous signal OFF time length, The distortion compensation unit compensates for the distortion due to the nonlinear characteristics of the power amplifier when the most recent signal OFF time was the first time, based on a distortion compensation coefficient that represents the inverse characteristics of the nonlinear characteristics of the power amplifier, calculated based on the transmission signal input to the power amplifier and the feedback signal obtained by feeding back the signal output from the power amplifier when the signal OFF time was previously the first time. Wireless communication device.

2. The aforementioned distortion compensation unit is Based on the previous signal OFF time length, the distortion due to the nonlinear characteristics of the power amplifier when starting wireless transmission is compensated. The wireless communication device according to claim 1.

3. The power amplifier has a transistor made of gallium nitride (GaN), The wireless communication device according to claim 1 or 2.

4. The aforementioned distortion compensation unit is During the first period from the moment the signal is turned ON, compensation is performed based on the first distortion compensation coefficient. During the period from the first period to the second period, compensation is performed based on a strain compensation coefficient that changes from the first strain compensation coefficient to the second strain compensation coefficient according to the passage of time. The nonlinear characteristics of the power amplifier are compensated based on the second distortion compensation coefficient during the second period, which differs from those of the first period. The wireless communication device according to claim 1 or 2.

5. Wireless communication device, Based on the previous signal OFF time, the distortion due to the nonlinear characteristics of the power amplifier, which amplifies and outputs the signal power, is compensated for. Based on a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier, calculated based on the transmission signal input to the power amplifier and the feedback signal obtained by feeding back the signal output from the power amplifier when the signal OFF time length was previously the first time length, the distortion due to the nonlinear characteristics of the power amplifier when the immediately preceding signal OFF time length was the first time length is compensated. method.

6. A process to compensate for distortion due to the nonlinear characteristics of the power amplifier that amplifies and outputs the signal power based on the previous signal OFF time length, The computer is instructed to perform a process to compensate for the distortion due to the nonlinear characteristics of the power amplifier when the most recent signal OFF time was the first time, based on a distortion compensation coefficient that represents the inverse characteristic of the nonlinear characteristics of the power amplifier, calculated based on the transmission signal input to the power amplifier when the signal OFF time was previously the first time, and the feedback signal obtained by feeding back the signal output from the power amplifier. program.

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