Wireless communication device and wireless communication method

Abstract

To provide a wireless communication device and wireless communication method that can suppress the deterioration of communication quality during operation. [Solution] The wireless communication device according to the present disclosure comprises: an amplifier for amplifying a transmission signal; a bias voltage application unit for applying a bias voltage; a calibration signal output unit for outputting a calibration signal; a storage unit for storing static characteristics showing the relationship between the gate voltage and the steady-state value of the drain current when an arbitrary bias voltage is applied, and correction information for correcting the transient value determined by the transient response of the drain current when one or more calibration signals are input and a set voltage is applied to an expected value; an envelope detection unit for detecting the amplitude of a transmission signal; a correction amount calculation unit for calculating a correction amount of the gate voltage to correct the transient value of the drain current when a transmission signal is input and a set voltage is applied, based on the static characteristics, the correction information, and the amplitude; and a correction amount setting unit for setting the correction amount in the bias voltage application unit.

Description

[Technical Field]

[0001] This disclosure relates to wireless communication devices and wireless communication methods. [Background technology]

[0002] Transmitting devices used in wireless communication such as mobile phones utilize amplifiers that employ amplification elements such as FETs (Field Effect Transistors) to amplify signals. In recent years, there has been a demand for amplifiers capable of higher output and more efficient operation, and amplifiers using nitride semiconductors such as gallium nitride (GaN) as amplification elements have been adopted.

[0003] Current collapse is known to occur in nitride semiconductor devices. Current collapse is as follows: When a high voltage is applied to a semiconductor device while it is in the off state, voltage stress is generated. As a result, charges are trapped in trap levels in the semiconductor layer, and the depletion layer expands. Subsequently, when the semiconductor device is turned on, an increase in on-resistance and a decrease in drain current occur immediately afterward. Due to the rapid change in drain current caused by current collapse, the gain fluctuates rapidly in the interval in which the change occurs. As a result, a degradation of signal quality, such as EVM (Error Vector Magnitude), becomes a problem.

[0004] To address the current collapse phenomenon, Patent Document 1 discloses a technique for adjusting the gate voltage. The power amplifier according to Patent Document 1 first sets the drain current to a predetermined design value by initializing the bias voltage. Next, the power amplifier detects the drain current a short time after it has reached the predetermined value and calculates the change from the predetermined value. Here, the power amplifier has prepared in advance the gate-source voltage necessary to maintain the drain current at the predetermined value based on the calculated change. As a result, by capturing the change in drain current and referring to the required change in gate-source voltage from the prepared data, the drain current in a steady state can be stabilized at the predetermined value. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2012-227795 [Overview of the project] [Problems that the invention aims to solve]

[0006] The power amplifier described in Patent Document 1 detects the drain current at two points in time and adjusts the gate voltage based on the difference between them. However, when a transmission signal is input to the amplifier during operation, the transmission signal fluctuates due to its high frequency, and therefore the gate voltage and drain current also fluctuate due to its high frequency. In this case, even if the drain current is measured at multiple points in time and the difference between them is calculated, it is not possible to grasp the transient change in the drain current based on the above phenomenon from this difference and adjust the gate voltage appropriately. Therefore, the power amplifier described in Patent Document 1 cannot suppress the deterioration of communication quality during operation.

[0007] This disclosure is made to solve these problems and aims to provide a wireless communication device and wireless communication method that can suppress the deterioration of communication quality during operation. [Means for solving the problem]

[0008] The wireless communication device according to this disclosure includes an amplifier that amplifies a transmission signal and has a gate terminal, a drain terminal, and a source terminal; a bias voltage application unit that applies a bias voltage to the gate terminal; a calibration signal output unit that outputs a calibration signal input to the gate terminal; a storage unit that stores static characteristics showing the relationship between the gate voltage of the gate terminal and the steady-state value of the drain current flowing to the drain terminal when an arbitrary bias voltage is applied, and correction information for correcting the transient value determined by the transient response of the drain current when one or more calibration signals are input to the gate terminal and a set voltage is applied to an expected value; an envelope detection unit that detects the amplitude of the transmission signal; a correction amount calculation unit that calculates a correction amount for the gate voltage to correct the transient value of the drain current when the transmission signal is input to the gate terminal and the set voltage is applied, based on the static characteristics, the correction information, and the amplitude; and a correction amount setting unit that sets the correction amount to the bias voltage application unit.

[0009] The wireless communication method according to this disclosure includes the steps of: a wireless communication device applying a bias voltage to the gate terminal of an amplifier that amplifies a transmission signal; inputting a calibration signal to the gate terminal; storing static characteristics showing the relationship between the gate voltage of the gate terminal and the steady-state value of the drain current flowing to the drain terminal when an arbitrary bias voltage is applied; and correction information for correcting the transient value determined by the transient response of the drain current when one or more calibration signals are input to the gate terminal and a set voltage is applied to an expected value; detecting the amplitude of the transmission signal; calculating a correction amount for the gate voltage to correct the transient value of the drain current when the transmission signal is input to the gate terminal and the set voltage is applied, based on the static characteristics, the correction information, and the amplitude; and setting the correction amount. [Effects of the Invention]

[0010] According to the present disclosure, a wireless communication device and a wireless communication method capable of suppressing deterioration of communication quality during operation can be provided.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 is a functional block diagram showing the configuration of the wireless communication device 1 according to the present disclosure. [Figure 2] FIG. 2 is a diagram showing an example of the time dependence of the drain current. [Figure 3] FIG. 3 is a diagram showing an example of the time change of the gate voltage when a set voltage is applied to the gate terminal and a calibration signal is input. [Figure 4] FIG. 4 is a diagram showing an example of the time change of the drain current when a set voltage is applied to the gate terminal and a calibration signal is input. [Figure 5] FIG. 5 is a diagram showing an example of the time change of the gate voltage when a set voltage is applied to the gate terminal and a transmission signal is input. [Figure 6] FIG. 6 is a diagram showing an example of the time change of the drain current when a set voltage is applied to the gate voltage and a transmission signal is input. [Figure 7] FIG. 7 is a flowchart showing an example of the flow of the processing operation of the wireless communication device 1 in the initial calibration stage. [Figure 8] FIG. 8 is a flowchart showing an example of the flow when the storage unit 14 stores the static characteristics. [Figure 9] FIG. 9 is a flowchart showing an example of the flow when the storage unit 14 stores the correction information. [Figure 10] FIG. 10 is a flowchart showing an example of the flow until the correction amount of the gate voltage is set in the operation stage. [Figure 11] FIG. 11 is a functional block diagram showing the configuration of the wireless communication device 100 according to the present disclosure. [Figure 12] FIG. 12 is a circuit diagram showing an example of the envelope detector 103 constituted by a digital circuit. [Figure 13]Figure 13 is a circuit diagram showing an example of an envelope detection unit 103 composed of analog circuits. [Figure 14] Figure 14 is a schematic diagram illustrating an example of a method for calculating the correction amount of the gate voltage used to correct current errors. [Figure 15] Figure 15 is a flowchart showing an example of the flow in the first initial calibration. [Figure 16] Figure 16 is a flowchart showing an example of the flow in the second initial calibration. [Figure 17] Figure 17 is a flowchart showing an example of the flow in the third initial calibration. [Figure 18] Figure 18 is a flowchart showing an example of the flow during the operational phase. [Figure 19] Figure 19 shows a comparison of the time variation of the gate bias voltage (bias voltage) with and without gate voltage correction when using a GaNFET. [Figure 20] Figure 20 shows a comparison of the time variation of the drain current with and without gate voltage correction when using a GaNFET. [Figure 21] Figure 21 shows a comparison of the time variation of the output voltage with and without gate voltage correction when using a GaNFET. [Figure 22] Figure 22 compares the change in output power with and without gate voltage correction when using a GaNFET, with respect to symbol length. [Figure 23] Figure 23 compares the change in EVM with and without gate voltage correction when using a GaNFET. [Figure 24] Figure 24 is a functional block diagram showing the configuration of the wireless communication device 200 according to this disclosure. [Figure 25] Figure 25 is a functional block diagram showing the configuration of the wireless communication device 300 according to this disclosure. [Figure 26] Figure 26 is a diagram showing an example of the hardware configuration of the wireless communication device 400 according to this disclosure. [Modes for carrying out the invention]

[0012] First, I will explain in detail the problems that the technology disclosed aims to solve. The wireless communication device disclosed includes an amplifier for amplifying transmitted signals in wireless communication such as mobile phones. Specifically, the wireless communication device disclosed includes wide-area base stations, macro base stations, active antenna systems, etc. When nitride semiconductor elements are used in the amplifier of a wireless communication device, a transient phenomenon called the current collapse phenomenon occurs, as described above.

[0013] On the other hand, when a wireless communication device operates using a time-division duplex (TDD) system, that is, when switching between UL (Up Link) and DL (Down Link) on the same frequency, transient phenomena called gate lag and drain lag occur. Gate lag is a phenomenon that occurs when switching between the on and off states of an amplifier by preparing a voltage that is the gate voltage (gate-source voltage in the case of a common-source configuration) to achieve the desired performance when the gate voltage is in the ON state, and a pinch-off voltage that is in the OFF state, and switching between these. In other words, gate lag is a phenomenon in which the drain current decreases due to a rapid change in gate voltage and changes transiently until it reaches a steady state. Drain lag is a phenomenon in which the drain current decreases due to a rapid change in drain voltage, such as when switching between the off and ON states of an amplifier, and changes transiently until it reaches a steady state.

[0014] In other words, when employing the TDD method, wireless communication equipment operates by rapidly switching between transmission and reception times. During reception, the power amplifier is shut down to reduce power consumption, while simultaneously preventing unnecessary power leakage from the equipment. When switching between the on and off states of the amplifier at high speed in this way, current collapse, gate lag, and drain lag (hereinafter referred to as transient phenomena) cause transient fluctuations in the amplifier's gain, output, and nonlinear characteristics (AM (Amplitude Modulation) characteristics, AM-PM (Phase Modulation) characteristics) immediately after the start of transmission and at other timings until they reach a steady state. As a result, the distortion compensation cannot keep up with the fluctuation in gain, and the signal quality, such as EVM at the beginning of the transmitted signal, deteriorates.

[0015] In response to transient response delays in drain current due to transient phenomena, the gate voltage adjustment technique described in Patent Document 1 determines the amount of gate voltage change required to maintain the drain current at a specified value in a steady state from the difference in drain current measured at two points in time.

[0016] However, the power amplifier described in Patent Document 1 cannot take into account the transmitted signal input to the amplifier during operation. That is, since the transmitted signal fluctuates at high frequencies, the gate voltage and drain current of the amplifier also fluctuate at high frequencies when the transmitted signal is input to the amplifier. In this case, even if multiple drain currents are measured and the difference between them is calculated, it is not possible to grasp the transient change in the drain current due to transient phenomena from this difference and adjust the gate voltage appropriately. For this reason, the power amplifier described in Patent Document 1 has a limited effect in suppressing the deterioration of communication quality during operation.

[0017] Each embodiment of the present disclosure described below contributes to solving the above-mentioned problems.

[0018] (Embodiment 1) The embodiments of this disclosure will be described below with reference to the drawings. Figure 1 is a functional block diagram showing the configuration of the wireless communication device 1 according to this disclosure. The wireless communication device 1 includes an amplifier 11, a bias voltage application unit 12, a calibration signal output unit 13, a storage unit 14, an envelope detection unit 15, a correction amount calculation unit 16, and a correction amount setting unit 17. Note that the unidirectional arrows shown in Figure 1 simply indicate the direction of the flow of a certain signal (data) and do not exclude bidirectionality.

[0019] The transmission signal targeted by the wireless communication device 1 is, for example, a signal modulated by the OFDM (Orthogonal Frequency Division Multiplexing) method. That is, the transmission signal targeted by the wireless communication device 1 may include the I signal (InPhase signal) and Q signal (Quadrature signal) of the baseband signal.

[0020] Amplifier 11 is a device for amplifying the transmission signal to a transmission output level that can be radiated from the antenna. Amplifier 11 uses a FET with a gate terminal, drain terminal, and source terminal as the amplifying element. Amplifier 11 uses nitride semiconductors as the amplifying element. Specifically, the amplifying elements of amplifier 11 are gallium nitride (GaN) FETs or aluminum gallium nitride (AlGaN) / GaN heterojunction FETs (HFETs).

[0021] The input / output characteristics of amplifier 11 have a nonlinear region. In other words, even if the input signal level of amplifier 11 increases, the output signal of amplifier 11 does not increase proportionally, and there is a nonlinear region in which the output signal of amplifier 11 becomes distorted. This nonlinear region is also called the saturation region. Amplifier 11 typically has an operating point where its efficiency is maximum near this saturation region.

[0022] The FET in amplifier 11 may be a normally-on type or a normally-off type. In the following explanation, we will describe the case where a normally-on type FET is used for amplifier 11.

[0023] The bias voltage application unit 12 is a device for applying a bias voltage to the gate terminal of the amplifier 11. In other words, the bias voltage application unit 12 is a constant voltage power supply for operating the amplifier 11 and applying a reference voltage to amplify the input signal to the amplifier 11. The bias voltage application unit 12 applies the bias voltage to the gate terminal via a bias circuit. The bias circuit includes one or more load resistors. Here, the voltage applied to the gate terminal is called the gate voltage. When only the bias voltage is applied to the gate terminal, the bias voltage and the gate voltage are equal in value.

[0024] The bias voltage application unit 12 can apply a gate voltage equivalent to the PAPR (Peak-to-Average Power Ratio) during operation to the gate terminal, via a pinch-off voltage that turns the FET off and a set voltage that turns the FET on. The gate voltage equivalent to the PAPR during operation refers to the gate voltage when the transmitted signal is at its maximum rating. In other words, the gate voltage equivalent to the PAPR refers to the maximum value of the gate voltage when the input of the transmitted signal is considered during operation. That is, the gate voltage equivalent to the PAPR refers to the value of the gate voltage when the peak signal of the transmitted signal is input to the amplifier 11.

[0025] The calibration signal output unit 13 is a device for outputting a calibration signal to be input to the gate terminal. The calibration signal output unit 13 can output a calibration signal having any signal level. The calibration signal input to the gate terminal may be, for example, a continuous wave (CW) or a pulse wave. In other words, the calibration signal may have a value that changes over time. In this case, the amplitude or frequency of the calibration signal may change over time. The calibration signal may be a sine wave, a square wave, a triangular wave, a sawtooth wave, or have any other waveform. Also, if the transmission signal is known, the calibration signal may have the same signal level as the transmission signal. The calibration signal output unit 13 is typically a signal generator.

[0026] The storage unit 14 is an example of a non-volatile storage device such as a hard disk or flash memory. The storage unit 14 stores static characteristics showing the relationship between the gate voltage and the steady-state value of the drain current when an arbitrary bias voltage is applied. That is, the storage unit 14 stores the relationship between the gate voltage and the drain current in a steady state after the gate voltage is applied. Here, the steady-state value of the drain current refers to the value of the drain current when the gate voltage is input and the drain current reaches a steady state. The storage unit 14 may store the relationship between the gate voltage and the steady-state value of the drain current as a table, as a function, or as a graph.

[0027] The static characteristics stored in the memory unit 14 may be, for example, the relationship between the steady-state values ​​of the gate voltage and drain current at predetermined stages when the gate voltage is changed from the pinch-off voltage to a voltage equivalent to PAPR. Alternatively, the static characteristics stored in the memory unit 14 may be the relationship when the gate voltage is changed from the pinch-off voltage to the set voltage. Furthermore, the static characteristics stored in the memory unit 14 may be the relationship between the average value of the gate voltage when the set voltage is applied to the gate terminal and a predetermined calibration signal is input, and the steady-state value of the drain current relative to that average value. In this case, the memory unit 14 also stores the relationship between the gate voltage from the pinch-off voltage to that average value.

[0028] Furthermore, the memory unit 14 stores correction information for correcting transient values ​​determined by the transient response of the drain current when a calibration signal is input to the gate terminal and a set voltage is applied. Here, transient response refers to the response delay of the drain current associated with transient phenomena. That is, when a calibration signal is input to the gate terminal and the gate voltage is switched, for example, from a pinch-off voltage to a set voltage, a predetermined time is required for the drain current to reach a steady state. Transient response is the dynamic characteristic of the drain current until it reaches a steady state.

[0029] In the above, the transient value is the value of the drain current at any point in time during the transient response. Here, any point in time may be any point in time or any time interval. That is, the transient value may be the value of the drain current at any point in time during the transient response, the value of the drain current determined by any time interval, or the range of the drain current over any time interval. Specifically, the transient value may be the RMS (Root Mean Square) value of the drain current over any time interval, the average value, or the peak value. When a single transient value is determined by any time interval, that transient value may be the average value of the RMS of the drain current over any time interval, or the peak value of the RMS. Also, the transient value may be the RMS value of the drain current at any point in time, or the instantaneous value. In the following explanation, the transient value will be described as being determined to a single value.

[0030] The correction information stored in the memory unit 14 is correction information for correcting transient values ​​to any value in the steady state. In other words, the correction information stored in the memory unit 14 is information for correcting the value of the drain current, which decreases due to transient phenomena, in a direction that increases it. Here, when a calibration signal is input to the gate terminal, unlike when only a bias voltage is applied, the steady-state value of the drain current is not necessarily uniquely determined. For example, if the calibration signal is a continuous wave, the drain current will not converge to a single value even when the steady state is reached, but will oscillate. The arbitrary steady-state value that the transient value targets may be, for example, the average value of the drain current in the steady state, the RMS value, or the peak value. If the drain current is fixed to a single value, that value may be used as the target. Hereafter, the arbitrary steady-state value that the transient value targets will be referred to as the expected value.

[0031] The expected value may be calculated based on the static characteristics stored in the memory unit 14. Specifically, it is as follows: First, the value of the gate voltage at the corresponding time of the transient is determined. Here, if the time is a single point in time, the gate voltage is uniquely determined. If the time is a time interval, the gate voltage may be the average value, the RMS value, or the peak value of the gate voltage during that time interval. Next, the steady-state value of the drain current corresponding to the value of the gate voltage is determined from the static characteristics stored in the memory unit 14. The expected value may be this steady-state value.

[0032] The memory unit 14 may store, as part of the correction information, the current error which is the difference between the transient value and the expected value, the value of the gate voltage that needs to be applied to correct the transient value to the expected value, or the correction amount which is the difference between the value of the gate voltage and the value of the set voltage. Hereafter, this information will be referred to as information regarding the gate voltage difference.

[0033] Furthermore, the memory unit 14 may store information regarding the amplitude of the calibration signal as part of the correction information for correcting transient values ​​to expected values.

[0034] The memory unit 14 may store information regarding the amplitude of the calibration signal and information regarding the gate voltage difference in association. In particular, if multiple calibration signals with different amplitudes are input to the gate terminal and the memory unit 14 stores information regarding the gate voltage difference when each calibration signal is input, the memory unit 14 may store information regarding the amplitude of each calibration signal and information regarding the gate voltage difference in association.

[0035] For example, consider a case where the memory unit 14 stores the current error between the transient value and the expected value as information regarding the gate voltage difference. In this case, the memory unit 14 may store the amplitude of the calibration signal and the current error in association. In particular, if multiple calibration signals with multiple different amplitudes are input to the gate terminal and the memory unit 14 stores the current error when each calibration signal is input, the memory unit 14 may store the signal level of each calibration signal and the current error in association.

[0036] Here, the memory unit 14 may store the association between information regarding the amplitude of the calibration signal and information regarding the gate voltage difference, that is, the correspondence between the two, as a table, as a function, or as a graph. In the above example, the memory unit 14 may store the current errors corresponding to each of the signal levels of multiple calibration signals as a table. For example, if a calibration signal with n different signal levels is input and one current error is stored for each, the memory unit 14 may store an n × 1 table.

[0037] The memory unit 14 may store information regarding multiple gate voltage differences obtained from multiple transient values ​​for the transient response of the drain current observed in response to a single calibration signal input. Multiple transient values ​​for the transient response are, for example, transient values ​​at multiple time points. That is, the memory unit 14 may store the value of the drain current determined by multiple time widths during the transient response, or it may store the range of the drain current at multiple time widths, or it may store the value of the drain current at multiple points in time. Specifically, the memory unit 14 may store the RMS value, average value, or peak value of the drain current at each of the multiple time widths. If one transient value is defined for each of the multiple time widths, the memory unit 14 may store the average value of the RMS value of the drain current at each time width, or it may store the peak value of the RMS value.

[0038] For example, consider a case where the memory unit 14 stores information about the gate voltage difference for each of the m time widths created by dividing a portion of the transient response by a time width α. If the transient value is the average value of the RMS value of the drain current in each time width, the memory unit 14 may also store the current error between the transient value and the expected value as information about the gate voltage difference for each time width. In this case, the memory unit 14 stores m current errors.

[0039] Consider the above case, where the memory unit 14 stores the correspondence between information regarding the amplitude of the calibration signal and information regarding the gate voltage difference as a table, and where the input of calibration signals has n different signal levels. If m current errors are stored for each input of the calibration signal, the memory unit 14 stores an n × m table.

[0040] Here, an example of correction information stored in the memory unit 14 will be explained with reference to the drawings. First, the transient response of the drain current due to transient phenomena is shown in the drawings. Figure 2 is a diagram showing an example of the time dependence of the drain current. In Figure 2, it is assumed that the bias voltage application unit 12 applies a set voltage from t1 to t2. Also, in Figure 2, the calibration signal and the transmission signal are not input to the gate terminal. In this case, the drain current I DS At t1, immediately after the set voltage is applied, the steady-state value is I DS_Q It does not change permanently, but changes transiently. In this case, for example, the current error, which is the difference between the transient value and the steady-state value at any point in time tx between t1 and t2, can be expressed as ΔIds(tx).

[0041] Next, we will explain the case when a calibration signal is input. Figure 3 shows an example of the time change of the gate voltage when a set voltage is applied to the gate terminal and a calibration signal is input. Figure 4 shows an example of the time change of the drain current when a set voltage is applied to the gate terminal and a calibration signal is input. In Figure 3, the set voltage is V GS_Q Therefore, a continuous wave (CW) with constant amplitude and frequency is input as the calibration signal. Furthermore, the set voltage and calibration signal are assumed to be applied and input between t1 and t2. As shown in Figure 3, by inputting a continuous wave calibration signal, the gate voltage oscillates with constant amplitude and frequency.

[0042] In Figure 4, I DS_QThis is the steady-state value of the drain current when the set voltage is applied, in the absence of transient phenomena. Also, in Figure 4, the upper waveform is the ideal drain current waveform when a continuous wave calibration signal is input, in the absence of transient phenomena. As shown in Figure 4, in the absence of transient phenomena, the drain current waveform from t1 to t2 is I DS_Q It oscillates with a constant amplitude and frequency around the point. In contrast, the waveform below is the drain current waveform when a continuous wave calibration signal is input, taking transient phenomena into consideration. As shown in Figure 4, when transient phenomena occur, the drain current waveform from t1 to t2 changes transiently while oscillating around the transient response of the drain current when only the set voltage is applied to the gate terminal (drain current waveform in Figure 2).

[0043] In Figure 4, the RMS value of the ideal drain current is taken as the expected value, and the RMS value of the drain current considering transient phenomena is taken as the actual response value. In this case, the memory unit 14 can store the current error, which is the difference ΔIds(tx) between the average value of the expected value and the average value of the actual response value during the time interval from tx-1 to tx, which is the time interval from t1 to t2, as part of the correction information.

[0044] Next, we will describe other specific examples of correction information stored in the memory unit 14. First, consider the case where the memory unit 14 stores the value of the gate voltage that needs to be applied to correct the transient value to the expected value as information about the gate voltage difference. In this case, the memory unit 14 stores the gate voltage value obtained, for example, as follows: First, the memory unit 14 finds the value of the gate voltage at which the expected value is the steady-state value from the static characteristics it stores. Next, the memory unit 14 finds the value of the gate voltage at which the transient value is the steady-state value from the static characteristics it stores. Then, it calculates the difference between these values. The value of the gate voltage that needs to be applied to correct the transient value to the expected value may be this difference.

[0045] Next, let's consider the case where the transmission signal is known. Specifically, let's consider the case where one of several transmission signals with different amplitudes predetermined during the operational phase is input to the gate terminal. In this case, the memory unit 14 may store correction information for when the same calibration signal as the multiple transmission signals is input to the gate terminal. In other words, the memory unit 14 may store as correction information the amount of gate voltage correction required to correct transient values ​​to expected values ​​when an expected transmission signal is input during the operational phase.

[0046] The envelope detection unit 15 detects the amplitude of the transmitted signal during the operational phase. Specifically, the envelope detection unit 15 detects the amplitude of the transmitted signal by detecting the envelope of the transmitted signal.

[0047] The correction amount calculation unit 16 calculates a correction amount for the gate voltage that corrects the transient value of the drain current when a transmission signal is input to the gate terminal and a set voltage is applied, based on the static characteristics stored in the memory unit 14, the correction information, and the amplitude detected by the envelope detection unit 15. In other words, the correction amount calculation unit 16 calculates a gate voltage in the operation phase that makes the transient value of the drain current, which fluctuates due to transient phenomena, equal to or close to the value in the steady state.

[0048] The correction amount calculation unit 16 may, for example, calculate the correction amount by associating the amplitude of the transmitted signal detected by the envelope detection unit 15 with the amplitude of the calibration signal stored by the storage unit 14 as part of the correction information. In this case, the correction amount calculation unit 16 may calculate the correction amount as the difference between the gate voltage when a calibration signal with the given amplitude is input and the gate voltage at which the transient value of the drain current when the calibration signal is input is the steady-state value.

[0049] For example, suppose the memory unit 14 stores transient values, expected values, and current errors when a calibration signal with an amplitude corresponding to the amplitude of the transmitted signal is input. The amplitude corresponding to the amplitude of the transmitted signal may be the same amplitude, an approximate amplitude, or the amplitude of the transmitted signal and the amplitude of the calibration signal may be integer multiples. If the memory unit 14 stores the amplitude of the calibration signal in association with the transient values, expected values, and current errors, the memory unit 14 can output transient values, expected values, and current errors corresponding to the amplitude of the calibration signal. The correction amount calculation unit 16 may calculate the correction amount of the gate voltage from the transient values, expected values, and current errors as follows.

[0050] First, the correction amount calculation unit 16 calculates the gate voltage based on the static characteristics when a calibration signal having the amplitude is input and a set voltage is applied. This can be determined by referring to the gate voltage at which the expected value of the drain current is a steady-state value from the static characteristics stored in the storage unit 14. Next, the correction amount calculation unit 16 derives the gate voltage at which the transient value of the drain current is a steady-state value. This can also be determined by referring to the static characteristics stored in the storage unit 14. The correction amount calculation unit 16 may calculate the difference between these values ​​as the correction amount for the gate voltage.

[0051] If the storage unit 14 stores the value of the gate voltage that needs to be applied to correct the transient value to the expected value as information regarding the gate voltage difference, the correction amount calculation unit 16 may determine the correction amount by outputting the correction amount of the gate voltage value corresponding to the amplitude from the storage unit 14.

[0052] The correction amount calculation unit 16 may calculate the correction amount based on the time from when the bias voltage application unit 12 applies the set voltage until the envelope detector 15 detects the amplitude, or may calculate the correction amount based on the time from when the transmission signal is input until the envelope detector 15 detects the amplitude. For example, consider the case where the storage unit 14 stores information regarding a plurality of gate voltage differences at a plurality of times. When the envelope detector 15 detects the amplitude Δt after the bias voltage application unit 12 applies the set voltage, the correction amount calculation unit 16 may calculate the correction amount using the data at time Δt stored by the storage unit 14.

[0053] On the other hand, the correction amount calculation unit 16 may calculate the correction amount of the gate voltage by a method other than the above. For example, consider the case where, during the operation stage, one of a plurality of signals having different amplitudes determined in advance is input to the gate terminal as the transmission signal. In this case, the correction amount calculation unit 16 may use, as the correction amount, the correction amount of the gate voltage stored by the storage unit 14 as it is when a calibration signal having the same amplitude as the amplitude of the transmission signal detected by the envelope detector 15 is input.

[0054] Here, the waveforms of the gate voltage and drain current when a transmission signal is input during the operation stage will be described using the drawings. FIG. 5 is a diagram showing an example of the time change of the gate voltage when a set voltage is applied to the gate terminal and a transmission signal is input. FIG. 6 is a diagram showing an example of the time change of the drain current when a set voltage is applied to the gate voltage and a transmission signal is input.

[0055] In FIG. 5, assume that the set voltage V GS_Q is applied from t1 to t2, and the pinch-off voltage V GS_OFF is applied at other times. As shown in FIG. 5, when a transmission signal is input from t1 to t2, the gate voltage fluctuates around V GS_Q . In FIG. 6, when the set voltage is applied from t1 to t2, the drain current also fluctuates. Here, the ideal drain current (expected value) without transient phenomena is the steady-state value I DS_Q when only the set voltage is applied.It fluctuates around this point. However, when considering transient phenomena, the drain current (actual response) fluctuates around a transient response waveform that is slower than the fluctuation of the transmitted signal. The correction amount calculation unit 16 calculates a correction value for the gate voltage that corrects the difference between the expected value and the actual response in Figure 6.

[0056] Finally, the correction amount setting unit 17 will be described. The correction amount setting unit 17 sets the gate voltage correction amount calculated by the correction amount calculation unit 16 to the bias voltage application unit 12. In other words, by setting the correction amount in the bias voltage application unit 12, the transient value of the drain current can be set to the value in the steady state or a value close to it. Here, the correction amount setting unit 17 may set the gate voltage value itself in the bias voltage application unit 12, or it may set the bias voltage application unit 12 to a correction amount to be added to the current bias voltage.

[0057] Next, the processing operation of the wireless communication device 1 will be described. First, the processing operation of the wireless communication device 1 in the stage until the memory unit 14 stores the static characteristics and correction information (initial calibration stage) will be described. Figure 7 is a flowchart showing an example of the flow of processing operation of the wireless communication device 1 in the initial calibration stage. First, the bias voltage application unit 12 applies a gate voltage to the gate terminal (S11). Next, the calibration signal output unit 13 outputs a calibration signal (S12). Here, steps S11 and S12 may be performed simultaneously, or step S12 may be performed before step S11. Also, if the memory unit 14 stores the static characteristics, step S12 may not be performed. After that, the memory unit 14 stores the static characteristics and correction information (S13).

[0058] Next, the flow of how the storage unit 14 stores static characteristics and correction information will be explained in detail. Figure 8 is a flowchart showing an example of the flow when the storage unit 14 stores static characteristics. First, the bias voltage application unit 12 applies a predetermined gate voltage to the gate terminal (S101). Next, the storage unit 14 stores the steady-state value of the drain current (S102). After that, the wireless communication device 1 determines whether the storage of all steady-state values ​​of the drain current for the target gate voltage range has been completed (S103). If the storage unit 14 has completed the storage, the procedure ends. If the storage of all steady-state values ​​of the drain current has not been completed, the bias voltage application unit 12 applies the gate voltage for the next step (S104). As a result, the storage unit 14 stores the static characteristics.

[0059] Next, the flow of the memory unit 14 storing correction information will be explained. Figure 9 is a flowchart showing an example of the flow of the memory unit 14 storing correction information. First, the bias voltage application unit 12 applies a set voltage to the gate terminal (S105). Next, the calibration signal output unit 13 outputs a predetermined calibration signal (S106). Here, the application of the set voltage by the bias voltage application unit 12 and the output of the calibration signal by the calibration signal output unit 13 may occur simultaneously, or the output of the calibration signal by the calibration signal output unit 13 may occur first. After that, the memory unit 14 stores the correction information (S107). After that, the bias voltage application unit 12 stops applying the set voltage, and the calibration signal output unit 13 stops outputting the calibration signal (S108). Here, the stopping of output by the bias voltage application unit 12 and the calibration signal output unit 13 may occur simultaneously with the storage of correction information by the memory unit 14, or the stopping of output by the bias voltage application unit 12 and the calibration signal output unit 13 may occur first. Subsequently, the wireless communication device 1 determines whether the storage unit 14 has finished storing the correction information for all target calibration signal inputs (S109). If the storage unit 14 has finished storing the information, the procedure ends. If the storage of correction information for all calibration signals has not been completed, the calibration signal output unit 13 sets the calibration signal for the next step (S110). As a result, the storage unit 14 stores the correction information.

[0060] Next, the processing operation of the wireless communication device 1 during the operational phase will be described. Figure 10 is a flowchart showing an example of the flow up to setting the gate voltage correction amount during the operational phase. First, the envelope detection unit 15 detects the amplitude of the transmitted signal (S14). Next, the correction amount calculation unit 16 calculates the gate voltage correction amount to correct the transient value of the drain current (S15). After that, the correction amount setting unit 17 sets the correction amount calculated by the correction amount calculation unit 16 to the bias voltage application unit 12 (S16).

[0061] Thus, the wireless communication device 1 according to this disclosure can suppress the deterioration of communication quality during operation. That is, because the transmission signal input to the amplifier 11 fluctuates due to its high frequency, the gate voltage and drain current of the amplifier 11 also fluctuate accordingly. In this case, even if multiple drain currents are measured and the difference between them is calculated, it is not possible to grasp the transient change in the drain current due to transient phenomena from this difference and adjust the gate voltage appropriately.

[0062] In the wireless communication device 1 according to this disclosure, a storage unit 14 stores static characteristics and correction information during the initial calibration stage, an envelope detection unit 15 detects the amplitude of the transmitted signal, a correction amount calculation unit 16 calculates the gate voltage correction amount based on the static characteristics, correction information, and amplitude, and a correction amount setting unit 17 sets the correction amount. In the operation stage, the wireless communication device 1 can calculate a gate voltage correction amount based on the transmitted signal by using the amplitude of the transmitted signal instead of using the difference in drain current. As a result, the wireless communication device 1 can compensate for the gate voltage and directly compensate for the drain current, thereby reducing gain fluctuations due to transient changes in drain current. This makes it possible to suppress the deterioration of signal quality such as EVM at the beginning of the transmitted signal.

[0063] (Embodiment 2) Next, the wireless communication device 100 according to this embodiment will be described. Figure 11 is a functional block diagram showing the configuration of the wireless communication device 100 according to this disclosure. The wireless communication device 100 is a system that specifically realizes the wireless communication device 1 according to Embodiment 1. The wireless communication device 100 includes a transmit signal output unit 101, a calibration signal / voltage output unit 102, an envelope detection unit 103, a time management unit 104, a transient phenomenon estimation unit 105, a memory unit 106, a correction amount setting unit 107, an amplifier 108, a DPD (Digital Pre-Distortion) signal processing unit 109, a DPD calculation unit 110, a CFR (Crest Factor Reduction) 111, a switch 112, a switch 113, a DAC (Digital-to-Analog Converter) 114, a DAC 115, a combining unit 116, a buffer 117, a driver 118, a differential amplifier 119, a coupler 120, an attenuator 121, an ADC (Analog-to-Digital Converter) 122, an ADC 123, and an output load 124. Note that the unidirectional arrow shown in Figure 11 simply indicates the direction of a signal (data) flow and does not exclude bidirectionality. Descriptions that overlap with those of the wireless communication device 1 according to Embodiment 1 will be omitted as appropriate.

[0064] The transmit signal output unit 101 is a device that outputs the transmit signal to be amplified by the wireless communication device 100 during the operational phase. The transmit signal output by the transmit signal output unit 101 is a digital signal modulated by the OFDM method. That is, the transmit signal includes the I signal and Q signal of a digitally modulated baseband signal. The transmit signal output unit 101 is connected to the switch 112.

[0065] The calibration signal / voltage output unit 102 is a device that outputs a calibration signal to be input to the gate terminal during the initial calibration stage, and also applies a bias voltage to the gate terminal during the initial calibration stage. The calibration signal / voltage output unit 102 comprises an output unit that outputs a calibration signal and an output unit that outputs a bias voltage. During the operation stage, the calibration signal / voltage output unit 102 inputs the calibration signal to the gate terminal via the same circuit as the circuit that the transmission signal output unit 101 uses to output the transmission signal. That is, the calibration signal output by the calibration signal / voltage output unit 102 is a digital signal. The calibration signal output by the calibration signal / voltage output unit 102 does not necessarily have to include both the I signal and the Q signal. The calibration signal output by the calibration signal / voltage output unit 102 may contain only the I signal.

[0066] The calibration signal / voltage output unit 102 is a device that performs the functions of the bias voltage application unit 12 and the calibration signal output unit 13 related to the wireless communication device 1 during the initial calibration stage. The calibration signal / voltage output unit 102 may be composed of multiple independent devices. For example, the calibration signal / voltage output unit 102 may be composed of a power supply unit and a signal generator. In Figure 11, the calibration signal / voltage output unit 102 is shown to output a calibration signal and a bias voltage. That is, in Figure 11, of the two lines extending from the calibration signal / voltage output unit 102, the upper line represents the circuit through which the calibration signal flows, and the lower line represents the circuit to which the bias voltage is applied. The calibration signal output from the calibration signal / voltage output unit 102 is input to the same switch 112 as the transmission signal output unit 101. The bias voltage output from the calibration signal / voltage output unit 102 is input to the same switch 113 as the correction amount setting unit 107 that outputs the bias voltage during the operation stage. Further explanation of the calibration signal / voltage output unit 102 is the same as that of the bias voltage application unit 12 and calibration signal output unit 13 related to the wireless communication device 1, and therefore the explanation is omitted.

[0067] The envelope detection unit 103 detects the envelope of the transmitted signal during the operational phase. The envelope detection unit 103 may also detect the envelope of the calibration signal during the initial calibration phase. In other words, the envelope detection unit 103 has the same function as the envelope detection unit 15 related to the wireless communication device 1. The envelope detection unit 103 detects the transmitted signal between the CFR 111 and the DPD signal processing unit 109 and the DPD calculation unit 110. The envelope detection unit 103 outputs the amplitude of the detected signal to the time management unit 104 and the transient phenomenon estimation unit 105.

[0068] The envelope detection unit 103 may be composed of digital circuits or analog circuits. Examples of the configuration of the envelope detection unit 103 are shown in Figures 12 and 13. Figure 12 is a circuit diagram showing an example of an envelope detection unit 103 composed of digital circuits. Figure 13 is a circuit diagram showing an example of an envelope detection unit 103 composed of analog circuits.

[0069] As shown in Figure 12, the envelope detection unit 103, which is composed of digital circuits, includes a multiplier unit 103a, an LPF (Low Pass Filter) 103b, and a square root calculation unit 103c. The multiplier unit 103a calculates the squares of the I signal and the Q signal. The LPF 103b removes high-frequency components of the signal and applies bandwidth limiting. The square root calculation unit 103c calculates the square roots of the I signal and the Q signal. Also, as shown in Figure 13, the envelope detection unit 103, which is composed of analog circuits, includes a diode 103d and a capacitor 103e. The diode 103d rectifies the I signal and the Q signal. The capacitor 103e smooths the high-frequency components of the signal. The other functions of the envelope detection unit 103 are the same as those of the envelope detection unit 15, so their explanation is omitted.

[0070] The time management unit 104 measures the elapsed time since the transmission signal output unit 101 detected during operation. The time management unit 104 may also measure the elapsed time since the calibration signal output unit 102 detected during the initial calibration stage. Alternatively, the time management unit 104 may measure the time since the calibration signal output unit 102 applied the bias voltage during operation. The time management unit 104 is typically a timer. The time management unit 104 receives the amplitude of the signal detected by the envelope detection unit 103 and outputs it to the transient phenomenon estimation unit 105 along with the time measured by the time management unit 104.

[0071] The transient phenomenon estimation unit 105 acquires the digital value of the drain current during the initial calibration stage and obtains the static and dynamic characteristics between the gate voltage and the drain current. The transient phenomenon estimation unit 105 then outputs the acquired characteristics of the amplifier 108 to the storage unit 106. Specifically, the transient phenomenon estimation unit 105 acquires the drain current value and obtains the relationship between the gate voltage and the drain current during the first, second, and third initial calibrations. The first, second, and third initial calibrations are measurement tests performed by the wireless communication device 100 during the initial calibration stage. Through the first, second, and third initial calibrations, the transient phenomenon estimation unit 105 acquires information such as the characteristics of the amplifier 108.

[0072] In the first initial calibration, the transient phenomenon estimation unit 105 acquires the static characteristics between the gate voltage and drain current when the calibration signal / voltage output unit 102 applies an arbitrary bias voltage to the gate terminal. The static characteristics refer to the relationship between the gate voltage and the drain current in a steady state, i.e., the steady-state value. The bias voltage applied to the gate terminal is, for example, a voltage from the pinch-off voltage to a voltage equivalent to PAPR. For example, the calibration signal / voltage output unit 102 applies the bias voltage in multiple stages from the set voltage to a voltage equivalent to PAPR, and the transient phenomenon estimation unit 105 measures the static characteristics by acquiring the drain current value at each stage. That is, in the first initial calibration, the transient phenomenon estimation unit 105 measures the static characteristics stored in the storage unit 14 according to Embodiment 1. The transient phenomenon estimation unit 105 outputs the static characteristics acquired in the first initial calibration to the storage unit 106.

[0073] In the second initial calibration, the transient phenomenon estimation unit 105 acquires the dynamic characteristics between the gate voltage and the drain current when the gate voltage is switched from the pinch-off voltage to the set voltage. In other words, the dynamic characteristics are the transient response of the drain current due to transient phenomena. That is, in the second initial calibration, the transient phenomenon estimation unit 105 acquires the relationship between the transient values ​​of the gate voltage and the drain current.

[0074] After the calibration signal / voltage output unit 102 switches the gate voltage from the pinch-off voltage to the set voltage, the calibration signal / voltage output unit 102 may switch back to the pinch-off voltage or leave it at the set voltage. Also, when switching the gate voltage back from the set voltage to the pinch-off voltage, the time it takes to switch from the pinch-off voltage to the set voltage and then back to the pinch-off voltage may be the same length as the time it takes to turn on the amplifier 108 when the wireless communication device 100 employs the TDD method. Specifically, this time may be the length of 1 symbol, 5 symbols, or 10 symbols. This time may also be the time it takes for the drain current to reach a steady state or the time it takes for it to not reach a steady state. The transient phenomenon estimation unit 105 outputs the dynamic characteristics of the gate voltage and drain current acquired in the second initial calibration to the storage unit 106.

[0075] In the second initial calibration, the transient phenomenon estimation unit 105 calculates the current error, which is the difference between the transient value of the drain current and the steady-state value of the drain current. The transient phenomenon estimation unit 105 may also obtain transient values ​​of the drain current at multiple time points after switching to the set voltage and calculate the current error. In this case, the transient phenomenon estimation unit 105 obtains the steady-state value of the drain current when the set voltage is applied from the storage unit 106. The transient phenomenon estimation unit 105 may also output the calculated current error to the storage unit 106.

[0076] Furthermore, in the second initial calibration, the transient phenomenon estimation unit 105 may calculate a correction amount for the gate voltage to correct the acquired current error. Here, an example of a method for calculating the correction amount for the gate voltage to correct the current error will be explained with reference to the drawings.

[0077] Figure 14 is a schematic diagram of an example of a method for calculating the correction amount of the gate voltage used to correct current errors. Figure 14 shows the gate voltage V GS x-axis, drain current I DS This graph shows the relationship between the two when V is used as the y-axis. GS_OFF V is the pinch-off voltage. GS_Qis the set voltage, I DS_Q The set voltage V GS_Q This is the steady-state value of the drain current when the pinch-off voltage V is applied. GS_OFF For example, the set voltage is -5V, and the set voltage is V GS_Q For example, is -2V, and also, I DS_C (tx) is the value of the drain current at time tx. Here, tx is any time in the transient response of the drain current when the gate voltage is switched from the pinch-off voltage to the set voltage. That is, I DS_C This is one of the transient values ​​of the drain current.

[0078] The curve shown in Figure 14 represents the static characteristics between the gate voltage and drain current acquired by the transient phenomenon estimation unit 105 in the first initial calibration. That is, the current error of the drain current at tx is I DS_Q and I DS_C ΔI is the difference from (tx). DS (tx). The transient phenomenon estimation unit 105 calculates the current error ΔI at tx. DS Gate voltage correction amount ΔV to correct (tx) GS (tx) can be calculated, for example, as follows:

[0079] First, the transient phenomenon estimation unit 105 calculates the transient value I of the drain current at time tx from the static characteristics of the gate voltage and drain current. DS_C The gate voltage V at which (tx) is a steady-state value. GS_C Calculate (tx). In other words, V GS_C The steady-state value of the drain current when (tx) is applied to the gate voltage is I DS_C (tx) is obtained. Next, the transient phenomenon estimation unit 105 sets the set voltage V GS_Q and V GS_C ΔV is the difference from (tx). GS The transient phenomenon estimation unit 105 calculates (tx). GS (tx) is the current error ΔI of the drain current at time tx. DS (tx) can be used as the gate voltage correction amount to correct. That is, the calibration signal / voltage output unit 102 is the gate voltage correction amount ΔV GSBy applying (tx) to the set voltage, the current error ΔI DS (tx) can be corrected. The transient phenomenon estimation unit 105 may output the calculated gate voltage correction amount of 1 or more to the storage unit 106.

[0080] Next, the third initial calibration will be described. In the third initial calibration, the transient phenomenon estimation unit 105 switches the bias voltage from the pinch-off voltage to the set voltage and acquires the dynamic characteristics of the gate voltage and drain current when the calibration signal is input to the gate terminal. That is, the third initial calibration acquires the transient response of the drain current when the calibration signal is input, compared to the second initial calibration. The calibration signal output by the calibration signal / voltage output unit 102 is the same as the calibration signal input to the gate terminal by the storage unit 14 in Embodiment 1 to store the correction information. That is, the third initial calibration is a measurement test performed to acquire the correction information stored by the storage unit 14 in Embodiment 1. Here, the transient phenomenon estimation unit 105 may acquire correction information for one calibration signal, or it may acquire correction information for multiple calibration signals having different amplitudes.

[0081] An example of the correction information acquired by the transient phenomenon estimation unit 105 will be explained again using Figures 3 and 4. In Figure 3, the calibration signal / voltage output unit 102 outputs a set voltage V from t1 to t2. GS_Q The voltage is applied. During this time, the calibration signal / voltage output unit 102 outputs a continuous wave (CW) of constant amplitude and constant frequency as a calibration signal. In Figure 3, we consider dividing the time from t1 to t2 into time widths α and acquiring correction information for m time widths. Of these, we consider acquiring correction information at time tx, for example.

[0082] In Figure 4, the correction information at time tx is, for example, the correction information for the time range from tx-1 to tx. First, the transient phenomenon estimation unit 105 calculates the average value of the RMS value of the actual response, which is the transient response, as the transient value for the time range from tx-1 to tx. Next, the transient phenomenon estimation unit 105 obtains the steady-state drain current when a set voltage is applied to the gate terminal and a calibration signal is input. This may be obtained by measuring the drain current that goes through the transient response to the steady state, or by obtaining the steady-state value I of the drain current when the set voltage is applied, which was obtained by the first initial calibration. DS_Q It may also be calculated from the waveform of the calibration signal. Subsequently, the transient phenomenon estimation unit 105 calculates the average value of the RMS value as the expected value of the drain current in the steady state. Then, the transient phenomenon estimation unit 105 calculates the difference ΔI between the transient value and the expected value. DS (tx) is calculated as the current error.

[0083] The transient phenomenon estimation unit 105 calculates the current error ΔI at time tx. DS A gate voltage correction amount may be calculated to correct (tx). Here, the method for calculating the gate voltage correction amount is the same as the calculation method in the second initial calibration. Specifically, it is as follows: First, the transient phenomenon estimation unit 105 calculates the gate voltage at which the transient value of the drain current at tx is the same as the steady-state value, based on the static characteristics of the gate voltage and drain current. That is, the transient phenomenon estimation unit 105 calculates the gate voltage at which the transient value of the drain current at tx is equal to the steady-state value, based on the static characteristics of the gate voltage and drain current. In other words, the steady-state value of the drain current when this gate voltage is applied will be the same as the transient value. That is, the steady-state value of the drain current when this gate voltage is applied will be equal to the transient value. Next, the transient phenomenon estimation unit 105 calculates the difference between the set voltage and the gate voltage. The transient phenomenon estimation unit 105 calculates this difference as the current error ΔI of the drain current at tx. DS (tx) can be used as the gate voltage correction amount to correct for this.

[0084] In the third initial calibration, the transient phenomenon estimation unit 105 may output the transient value of the drain current to the storage unit 106, or it may output the expected value, or it may output the current error, or it may output the gate voltage correction amount, or it may output all of these. In other words, the transient phenomenon estimation unit 105 outputs arbitrary correction information for calculating the gate voltage correction amount to the storage unit 106. Here, the transient phenomenon estimation unit 105 outputs to the storage unit 106 the elapsed time since the calibration signal / voltage output unit 102 applied the set voltage or output the calibration signal, and the amplitude of the calibration signal, relating the above correction information.

[0085] During operation, the transient phenomenon estimation unit 105 receives amplitude information of the transmitted signal from the envelope detection unit 103 and elapsed time information from the time management unit 104. The transient phenomenon estimation unit 105 retrieves correction information corresponding to the amplitude and elapsed time from the storage unit 106. Here, the correction information corresponding to the amplitude and elapsed time of the transmitted signal may be correction information for the same elapsed time when a calibration signal with the same amplitude is input, or it may be correction information for an approximate amplitude and an approximate elapsed time. The transient phenomenon estimation unit 105 outputs the correction information retrieved from the storage unit 106 to the correction amount setting unit 107.

[0086] The storage unit 106 is an example of a non-volatile storage device such as a hard disk or flash memory. During the initial calibration stage, the storage unit 106 acquires and stores from the transient phenomenon estimation unit 105 the static characteristics of the drain current based on the first initial calibration, the dynamic characteristics of the drain current based on the second and third initial calibrations, and correction information such as current error and gate voltage correction value. Here, the storage unit 106 stores the correction information acquired by the transient phenomenon estimation unit 105 in the third initial calibration in association with the elapsed time since the calibration signal was output and the amplitude of the calibration signal. Specifically, the storage unit 106 may store these relationships in a table. That is, the storage unit 106 has the same function as the storage unit 14 in Embodiment 1. During the operation stage, the storage unit 106 outputs the correction information to the transient phenomenon estimation unit 105 based on a command from the transient phenomenon estimation unit 105.

[0087] The correction amount setting unit 107 applies a bias voltage to the gate terminal during operation. In particular, when correcting transient values ​​of drain current due to transient phenomena, the correction amount setting unit 107 obtains correction information from the transient phenomenon estimation unit 105 and applies a bias voltage to the gate terminal that takes into account the correction amount of the gate voltage for correcting transient values. In other words, during operation, the correction amount setting unit 107 has the functions of the bias voltage application unit 12, the correction amount calculation unit 16, and the correction amount setting unit 17 according to Embodiment 1.

[0088] If the memory unit 106 stores the gate voltage correction amount as correction information, that is, if the transient phenomenon estimation unit 105 outputs the gate voltage correction amount to the correction amount setting unit 107, the correction amount setting unit 107 applies a bias voltage which is the set voltage plus the gate voltage correction amount. On the other hand, if the memory unit 106 does not store the gate voltage correction amount as correction information, that is, if the transient phenomenon estimation unit 105 does not output the gate voltage correction amount to the correction amount setting unit 107, the correction amount setting unit 107 calculates the gate voltage correction amount. For example, if the transient phenomenon estimation unit 105 outputs the current error to the correction amount setting unit 107, the correction amount setting unit 107 calculates the gate voltage correction amount from the current error. The method for calculating the gate voltage correction amount from the current error is the same as the method used by the transient phenomenon estimation unit 105 to calculate the gate voltage correction amount in the third initial calibration, so a detailed explanation of the method is omitted.

[0089] Amplifier 108 is a device for amplifying the transmission signal to a transmission output level that can be radiated from the antenna. The input / output characteristics of amplifier 108 have a nonlinear region similar to that of amplifier 11 according to Embodiment 1. Amplifier 108 comprises an amplifying element 108a, a drain voltage supply unit 108b, a load 108c, an LPF 108d, a load 108e, a bonding wire 108f, a coupling capacitor 108g, and a coupling capacitor 108h.

[0090] The amplification element 108a is a FET having a gate terminal, a drain terminal, and a source terminal. The amplification element 108a is a nitride semiconductor, similar to the amplification element of the amplifier 11 according to Embodiment 1. The amplification element 108a is, for example, a GaN FET.

[0091] The drain voltage supply unit 108b is a power supply device that supplies drain voltage. The drain voltage supply unit 108b supplies DC voltage. The load 108c is an inductor located between the drain voltage supply unit 108b and the drain terminal of the amplification element 108a. The DC voltage output from the drain voltage supply unit 108b is supplied to the drain terminal of the amplification element 108a via the load 108c.

[0092] The LPF108d limits the high-frequency bandwidth of the bias voltage. The LPF108d receives an analog signal of the bias voltage as input and supplies the bias voltage to the gate terminal of the amplifier element 108a via the load 108e. The load 108e is an inductor located between the LPF108d and the gate terminal of the amplifier element 108a.

[0093] The bonding wire 108f is a wire used to detect the drain current and extract it externally. One end of the bonding wire 108f is connected to the source terminal of the amplification element 108a, and the other end is grounded. The equivalent circuit of the bonding wire 108f is a parallel circuit of inductor 108f1, shunt resistor 108f2, and capacitor 108f3, as shown in Figure 11. One terminal of the bonding wire 108f and the other terminal are branched and input to the differential amplifier 119, which is outside the amplifier 108. As a result, the bonding wire 108f can extract the current flowing through it, i.e., the drain current, externally.

[0094] The coupling capacitor 108g is a capacitor that cuts the DC component of the transmission signal input to the amplifier 108, and stably superimposes the bias voltage and the transmission signal. One end of the coupling capacitor 108g is connected to the driver 118, and the other end is connected to the gate terminal of the load 108e and the amplification element 108a.

[0095] The coupling capacitor 108h is a capacitor that cuts the DC component of the amplified transmission signal, allowing only the AC component of the transmission signal to be output. One end of the coupling capacitor 108h is connected between the load 108c and the drain terminal of the amplification element 108a, and the other end is connected to the coupler 120.

[0096] The DPD signal processing unit 109 receives the transmission signal during the operation phase, multiplies the transmission signal by a distortion compensation coefficient that is the inverse of the characteristics of the amplifier 108, and outputs it to the DAC 115. Specifically, the DPD signal processing unit 109 compensates for the nonlinear characteristics of the amplifier 108 at the high-efficiency point where the amplifier 108 operates, and adds a distortion compensation coefficient to the transmission signal to output a signal with linear characteristics. The DPD signal processing unit 109 receives the distortion compensation coefficient from the DPD calculation unit 110.

[0097] The DPD calculation unit 110 compares the transmission signal input to the gate terminal during operation with the fed-back drain current and calculates a distortion compensation coefficient. The DPD signal processing unit 109 has one end connected to the CFR 111 and the other end connected to the DAC 115. The DPD calculation unit 110 receives the signal input to the DPD signal processing unit 109 and the signal output by the DPD signal processing unit 109. The DPD calculation unit 110 also receives the amplified transmission signal via the coupler 120, attenuator 121, and ADC 122. Based on this information, the DPD calculation unit 110 calculates a distortion compensation coefficient and outputs it to the DPD signal processing unit 109.

[0098] The DPD signal processing unit 109 and the DPD calculation unit 110 may or may not be used in the initial calibration stage.

[0099] CFR111 receives the transmit signal output from switch 112 and clips the transmit signal according to a predetermined threshold value based on the input / output characteristics of amplifier 108. The clipped transmit signal is output to envelope detection unit 103 and DPD signal processing unit 109. CFR111 may be used only during the operational phase. In other words, CFR111 may or may not be used during the initial calibration phase.

[0100] Switches 112 and 113 are devices for switching the circuit between the initial calibration stage and the operation stage. Switch 112 is configured to accept signals from either the calibration signal / voltage output unit 102 or the transmission signal output unit 101, and is switchably connected to either unit. That is, switch 112 is configured to accept the calibration signal during the initial calibration stage and the transmission signal during the operation stage. Switch 112 outputs either of the input signals to the CFR111. In Figure 11, when switch 112 is switched to "1", switch 112 outputs the calibration signal output from the calibration signal / voltage output unit 102 to the CFR111. When switch 112 is switched to "0", switch 112 outputs the transmission signal output from the transmission signal output unit 101 to the CFR111.

[0101] Switch 113 is configured to switchably connect to the calibration signal / voltage output unit 102 and the correction amount setting unit 107, and to apply a bias voltage from either one to the gate terminal. That is, in the initial calibration stage, switch 113 applies the bias voltage supplied from the calibration signal / voltage output unit 102 to the gate terminal, and in the operation stage, it applies the bias voltage supplied from the correction amount setting unit 107 to the gate terminal. In Figure 11, when switch 113 is switched to "1", switch 113 applies the bias voltage supplied from the calibration signal / voltage output unit 102 to the gate terminal. When switch 113 is switched to "0", switch 113 applies the bias voltage supplied from the correction amount setting unit 107 to the gate terminal.

[0102] Switches 112 and 113 may be able to switch circuits in conjunction. For example, by selecting whether it is the initial calibration phase or the operation phase, the control system (not shown) of the wireless communication device 100 may be controlled to switch switches 112 and 113 simultaneously. For example, in Figure 11, when switching from the initial calibration phase to the operation phase, the control system may switch switches 112 and 113 from "1" to "0".

[0103] DAC114 and DAC115 are devices for converting input digital signals into analog signals. DAC114 is placed in a circuit that applies a bias voltage to the gate terminal. Specifically, one terminal of DAC114 is connected to switch 113, and the other terminal is connected to the LPF108d of amplifier 108. That is, DAC114 converts the digital signal of the bias voltage output from calibration signal / voltage output unit 102 or correction amount setting unit 107 into an analog signal and outputs it to amplifier 108.

[0104] The DAC115 is placed in the circuit that inputs the calibration signal or transmission signal to its gate terminal. Specifically, one terminal of the DAC115 is connected to the DPD signal processing unit 109, and the other terminal is connected to the combining unit 116. In other words, the DAC115 converts the digital signal of the transmission signal or calibration signal processed by the DPD signal processing unit 109 into an analog signal and outputs it to the amplifier 108.

[0105] The combining unit 116 combines the I signal and Q signal of the transmission signal or calibration signal. One terminal of the combining unit 116 is connected to the DAC 115, and the other terminal is connected to the buffer 117. The combining unit 116 receives the transmission signal or calibration signal output from the DAC 115 and outputs the combined signal to the buffer 117.

[0106] Buffer 117 and driver 118 are amplifiers positioned before amplifier 108. Buffer 117 and driver 118 amplify the transmit signal or calibration signal to a level that amplifier 108 can amplify. One terminal of buffer 117 is connected to the combining unit 116, and the other terminal is connected to driver 118. Buffer 117 receives the combined signal from the combining unit 116 and outputs the amplified signal to driver 118. One terminal of driver 118 is connected to buffer 117, and the other terminal is connected to the coupling capacitor 108g of amplifier 108. Driver 118 receives the signal amplified by buffer 117, further amplifies the signal, and outputs it to amplifier 108.

[0107] The differential amplifier 119 is a current sense amplifier for detecting the drain current extracted by the bonding wire 108f of the amplifier 108. One end of the differential amplifier 119 is connected to the source terminal and ground terminal of the bonding wire 108f, and the other end of the differential amplifier 119 is connected to the ADC 123. The differential amplifier 119 amplifies the detected drain current and outputs it to the ADC 123.

[0108] Coupler 120 is a distributor for feeding back the transmitted signal output via amplifier 108 to DPD calculation unit 110. One end of coupler 120 is connected to the coupling capacitor 108h of amplifier 108, and the other end is connected to the attenuator 121 and output load 124. In other words, the transmitted signal output from amplifier 108 via coupling capacitor 108h is split by coupler 120 to the attenuator 121 and output load 124.

[0109] The attenuator 121 is a device that attenuates the transmitted signal amplified via the amplifier 108 to its pre-amplified level and inputs it to the DPD calculation unit 110. One end of the attenuator 121 is connected to the coupler 120, and the other end is connected to the ADC 122. The attenuator 121 attenuates the transmitted signal distributed by the coupler 120 and outputs it to the ADC 122.

[0110] ADC122 and ADC123 are devices for converting input analog signals into digital signals. One end of ADC122 is connected to attenuator 121, and the other end of ADC122 is connected to DPD calculation unit 110. ADC122 outputs the transmitted signal attenuated by attenuator 121 to DPD calculation unit 110. One end of ADC123 is connected to differential amplifier 119, and the other end of ADC123 is connected to transient phenomenon estimation unit 105. ADC123 outputs the detected drain current to transient phenomenon estimation unit 105.

[0111] The output load 124 is a load resistor located at the output terminal. The output load 124 is connected to the coupler 120. The output load 124 consumes the power of the transmitted signal distributed from the coupler 120. The output load 124 may be, for example, an antenna.

[0112] Next, the processing operations of the wireless communication device 100 will be described. First, an example of the flow of processing operations of the wireless communication device 100 during the initial calibration stage will be described. Figure 15 is a flowchart showing an example of the flow during the first initial calibration. In Figure 15, the calibration signal / voltage output unit 102 is assumed to apply a bias voltage ranging from the pinch-off voltage to the gate voltage equivalent to the PAPR during operation.

[0113] First, the calibration signal / voltage output unit 102 applies a pinch-off voltage to the gate terminal (S21). Next, the transient phenomenon estimation unit 105 acquires the steady-state drain current (S22). Then, the memory unit 106 stores the static characteristics between the gate voltage and the drain current (S23). After that, the wireless communication device 100 determines whether the bias voltage applied by the calibration signal / voltage output unit 102 is equivalent to the gate voltage of the PAPR during operation (S24). If the bias voltage is equivalent to the gate voltage of the PAPR during operation, the first initial calibration is completed. If the bias voltage has not reached the gate voltage equivalent to the PAPR during operation, the calibration signal / voltage output unit 102 applies the next stage bias voltage to the gate terminal (S25). Thus, the wireless communication device 100 performs the first initial calibration.

[0114] Figure 16 is a flowchart illustrating an example of the flow in the second initial calibration. In Figure 16, the transient phenomenon estimation unit 105 acquires the transient response and current error of the drain current, and the storage unit 106 stores the transient response and current error of the drain current. First, the calibration signal / voltage output unit 102 applies a set voltage as the bias voltage (S26). Next, the transient phenomenon estimation unit 105 acquires the transient response of the drain current and the current error between it and the steady-state value (S27). After that, the storage unit 106 stores the transient response and current error of the drain current (S28). As a result, the wireless communication device 100 performs the second initial calibration.

[0115] Figure 17 is a flowchart illustrating an example of the flow in the third initial calibration. In Figure 17, the calibration signal / voltage output unit 102 receives n calibration signals, and the transient phenomenon estimation unit 105 acquires the transient response for each calibration signal. The transient phenomenon estimation unit 105 divides the time during which the set voltage is applied into time widths α and acquires the transient value of the drain current for each time width. Here, the total number of time widths is assumed to be m. The transient phenomenon estimation unit 105 also acquires the current error for each time width. Furthermore, the storage unit 106 stores the relationship between the current error and the amplitude of the calibration signal for each time width in a table.

[0116] First, the calibration signal / voltage output unit 102 applies a set voltage as a bias voltage (S29). Next, the calibration signal / voltage output unit 102 outputs a calibration signal (S30). Here, the calibration signal / voltage output unit 102 may perform the steps of applying the set voltage and outputting the calibration signal simultaneously. After that, the transient phenomenon estimation unit 105 acquires the transient response of the drain current (S31). Then, the transient phenomenon estimation unit 105 acquires a total of m transient values ​​of the drain current for each time width α (S32). After that, the transient phenomenon estimation unit 105 acquires the expected value of the drain current for each time width α (S33). After that, the transient phenomenon estimation unit 105 calculates a total of m current errors for each time width α (S34).

[0117] Subsequently, the memory unit 106 stores the relationship between the current error for each time width α and the amplitude of the calibration signal as a table (S35). Then, the calibration signal / voltage output unit 102 stops applying the set voltage and outputting the calibration signal (S36). Here, the application of the set voltage and stopping the output of the calibration signal by the calibration signal / voltage output unit 102 may occur simultaneously with the storage by the memory unit 106, or it may occur before the storage by the memory unit 106. After that, the wireless communication device 100 determines whether the third initial calibration has been performed for the n calibration signals (S37). If the third initial calibration has been performed for the n calibration signals, the third initial calibration is completed. If the third initial calibration has not been performed for the n calibration signals, the calibration signal / voltage output unit 102 changes the signal level of the calibration signal (S38). As a result, the wireless communication device 100 performs the third initial calibration.

[0118] Next, an example of the processing flow of the wireless communication device 100 during the operational phase will be described. Figure 18 is a flowchart of an example of the flow during the operational phase. In Figure 18, the correction amount setting unit 107 is assumed to calculate the gate voltage correction amount.

[0119] First, the correction amount setting unit 107 applies a set voltage as the bias voltage (S39). Next, the transmission signal output unit 101 outputs the transmission signal to be amplified (S40). Here, the transmission signal output unit 101 may output the transmission signal at the same time as the bias voltage is applied by the correction amount setting unit 107, or it may output the transmission signal before that. After that, the envelope detection unit 103 detects the envelope of the transmission signal (S41). Then, the time management unit 104 measures the elapsed time since the set voltage was applied or since the transmission signal was output (S42). Here, the measurement of the elapsed time by the time management unit 104 may be at the same time as the detection of the envelope by the envelope detection unit 103, or it may be before that. After that, the transient phenomenon estimation unit 105 obtains the current error from the storage unit 106 based on the amplitude of the transmission signal and the elapsed time (S43). Subsequently, the correction amount setting unit 107 calculates the gate voltage correction amount based on the current error calculated by the transient phenomenon estimation unit 105 (S44). Then, the correction amount setting unit 107 applies a bias voltage that takes into account the calculated gate voltage correction amount (S45).

[0120] As described above, the wireless communication device 100 according to this disclosure can suppress the deterioration of communication quality during operation. Compared to the wireless communication device 1 according to Embodiment 1, the wireless communication device 100 focuses on the amplitude of the signal, calculates the gate voltage correction amount by detecting the envelope of the transmitted signal, and corrects the drain current by correcting the gate voltage. As a result, the wireless communication device 100 can reduce fluctuations in gain due to transient changes in the drain current after the set voltage is applied. Consequently, the wireless communication device 100 can suppress the deterioration of communication quality such as EVM.

[0121] The effects of the wireless communication device 100 according to this disclosure will be explained with reference to the drawings. Figure 19 is a diagram comparing the time change of the gate bias voltage (bias voltage) with and without gate voltage correction when using a GaN FET. In Figure 19, the horizontal axis represents time, and the vertical axis represents the amplitude of the voltage. In Figure 19, the gate lag and drain lag are simulated. Furthermore, in the case with correction in Figure 19, the wireless communication device 100 corrects both the current error with respect to the initial value of the applied gate bias voltage, which is -2.1V, and the current error with respect to the amplitude of the transmitted signal.

[0122] Figure 20 compares the time variation of drain current with and without gate voltage correction when using a GaN FET. In Figure 20, the horizontal axis represents time, and the vertical axis represents the current value. As shown in Figure 20, when the gate voltage is not corrected for amplifier 108 with poor gate lag and drain lag, the drain current immediately after amplifier 108 turns on is suppressed and significantly degraded. On the other hand, when the gate voltage is corrected, the degradation of the drain current immediately after amplifier 108 turns on is suppressed.

[0123] Figure 21 compares the time variation of the output voltage with and without gate voltage correction when using a GaN FET. In Figure 21, the horizontal axis represents time, and the vertical axis represents the voltage amplitude. As shown in Figure 21, when the gate voltage is not corrected for amplifier 108 with poor gate lag and drain lag, the output voltage immediately after amplifier 108 turns on drops significantly. On the other hand, when the gate voltage is corrected, the drop in output voltage immediately after amplifier 108 turns on is suppressed.

[0124] Figure 22 compares the change in output power with and without gate voltage correction when using a GaN FET, with respect to symbol length. In Figure 22, the horizontal axis represents symbol length, and the vertical axis represents output power. As shown in Figure 22, when the gate voltage is not corrected for amplifier 108 with poor gate lag, the output power immediately after amplifier 108 turns on drops significantly. In contrast, when the gate voltage is corrected, the drop in output power immediately after amplifier 108 turns on is suppressed.

[0125] Figure 23 compares the change in EVM with and without gate voltage correction when using a GaN FET. In Figure 23, the horizontal axis represents symbol length and the vertical axis represents EVM. As shown in Figure 23, when the gate voltage is not corrected for amplifier 108 with poor gate lag, the output power immediately after amplifier 108 turns on drops significantly, degrading the EVM of the first symbol of the transmitted signal. In contrast, when the gate voltage is corrected, the drop in output power immediately after amplifier 108 turns on is suppressed, thereby suppressing the degradation of the EVM of the first symbol of the transmitted signal.

[0126] (Embodiment 3) Next, the wireless communication device 200 according to this embodiment will be described. Figure 24 is a functional block diagram showing the configuration of the wireless communication device 200 according to this disclosure. The unidirectional arrows shown in Figure 24 simply indicate the direction of the flow of a certain signal (data) and do not exclude bidirectionality. The wireless communication device 200 differs from the wireless communication device 100 according to Embodiment 2 in that the location of drain current acquisition is different. Specifically, the wireless communication device 200 places the shunt resistor 108f2 for detecting the drain current not on the bonding wire 108f, but between the drain voltage supply unit 108b and the amplification element 108a. The drain current flowing through the shunt resistor 108f2 is input to the transient phenomenon estimation unit 105 via the differential amplifier 119 and the ADC 123.

[0127] The specific differences in configuration compared to the wireless communication device 100 are as follows: In the amplifier 108, a load 108c and a shunt resistor 108f2 are placed between the amplifying element 108a and the drain voltage supply unit 108b. One end of the shunt resistor 108f2 is connected to the load 108c, and the other end is connected to the drain terminal. The coupling capacitor 108h is connected between the shunt resistor 108f2 and the drain terminal. In the differential amplifier 119, one set of two terminals is connected between the terminals of the shunt resistor 108f2, and the other terminal is connected to the ADC 123. As a result, the differential amplifier 119 can detect the drain current flowing through the shunt resistor 108f2 located on the drain side. The other configurations are the same as those of the wireless communication device 100, so their explanation is omitted. By using the wireless communication device 200, the deterioration of communication quality during operation can also be suppressed.

[0128] (Embodiment 4) Next, the wireless communication device 300 according to this embodiment will be described. Figure 25 is a functional block diagram showing the configuration of the wireless communication device 300 according to this disclosure. The unidirectional arrows shown in Figure 25 simply indicate the direction of the flow of a certain signal (data) and do not exclude bidirectionality. The wireless communication device 300 performs gate voltage correction on the wireless communication device 100 according to Embodiment 2 using the transmitted signal amplified by the amplifier 108.

[0129] The specific differences in configuration compared to the wireless communication device 100 are as follows: One end of the ADC 122 is connected to the attenuator 121, while the other end is connected not only to the DPD calculation unit 110 but also to the envelope detection unit 103. The envelope detection unit 103 receives the transmission signal via the ADC 122.

[0130] In the wireless communication device 100, the envelope detection unit 103 receives the transmission signal before amplification by the amplifier 108 and detects its envelope. In contrast, in the wireless communication device 300, the envelope detection unit 103 receives the transmission signal that has been amplified by the amplifier 108 and branched from the coupler 120, and detects its envelope. The envelope detection unit 103 outputs the amplitude of the signal detected by detecting the envelope to the time management unit 104 and the transient phenomenon estimation unit 105, similar to the wireless communication device 100. The other configurations of the envelope detection unit 103 are the same as those of the wireless communication device 100. The other configurations of the wireless communication device 300 are also the same as those of the wireless communication device 100, so their explanation is omitted. By using the wireless communication device 300, the deterioration of communication quality during operation can also be suppressed.

[0131] (Hardware configuration) Figure 26 shows an example of the hardware configuration of a wireless communication device 400 according to the present disclosure. In Figure 26, the wireless communication device 400 has a processor 401 and a memory 402. The processor 401 may be, for example, a microprocessor, an MPU (Micro Processing Unit), or a CPU (Central Processing Unit). The processor 401 may include multiple processors. The memory 402 is composed of a combination of volatile memory and non-volatile memory. The memory 402 may include storage located away from the processor 401. In this case, the processor 401 may access the memory 402 via an I / O (Input / Output) interface, which is not shown.

[0132] In the above example, the program can be stored and provided to the computer using various types of non-transitory computer-readable medium. Non-transitory computer-readable medium includes various types of tangible storage medium. Examples of non-transitory computer-readable medium include magnetic storage media (e.g., magneto-optical disks), CD-ROMs, CD-Rs, CD-R / Ws, and semiconductor memory (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, RAMs). Alternatively, the program may be provided to the computer using various types of transient computer-readable medium. Examples of transient computer-readable medium include electrical signals, optical signals, and electromagnetic waves. Transitory computer-readable medium can be supplied to the computer via wired communication channels such as electric wires and optical fibers, or via wireless communication channels. Computers include various information processing devices such as PCs (Personal Computers), servers, CPUs, MPUs, FPGAs (Field Programmable Gate Arrays), and ASICs (Application Specific Integrated Circuits).

[0133] 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 made as can be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0134] Each drawing is merely illustrative to illustrate one or more embodiments. Each drawing may be associated with one or more other embodiments rather than with only one specific embodiment. As those skilled in the art will understand, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings, for example, to create embodiments not explicitly shown or described. Not all features or steps shown in any one drawing to illustrate an exemplary embodiment are necessarily required, and some features or steps may be omitted. The order of steps shown in any of the drawings may be changed as appropriate.

[0135] Some or all of the above embodiments may also be described as follows, but are not limited to the following: (Note 1) An amplifier equipped with a gate terminal, drain terminal, and source terminal, which amplifies the transmitted signal, A bias voltage application unit that applies a bias voltage to the gate terminal, A calibration signal output unit that outputs a calibration signal input to the gate terminal, A storage unit that stores static characteristics showing the relationship between the gate voltage of the gate terminal and the steady-state value of the drain current flowing through the drain terminal when any bias voltage is applied, and correction information for correcting the transient value determined by the transient response of the drain current when one or more calibration signals are input to the gate terminal and a set voltage is applied to the expected value, An envelope detection unit for detecting the amplitude of the transmitted signal, A correction amount calculation unit calculates a correction amount for the gate voltage that corrects the transient value of the drain current when the transmission signal is input to the gate terminal and the set voltage is applied, based on the static characteristics, the correction information, and the amplitude. A correction amount setting unit for setting the correction amount to the bias voltage application unit, A wireless communication device equipped with the following features. (Note 2) The calibration signal output unit outputs a plurality of calibration signals having different amplitudes. The storage unit stores the correction information when the plurality of calibration signals are input. The correction amount calculation unit calculates the difference between the gate voltage calculated based on the static characteristics when the calibration signal having the amplitude corresponding to the amplitude of the transmission signal is input and the set voltage is applied, and the gate voltage at which the transient value of the drain current is the steady-state value, as the correction amount. The wireless communication device described in Appendix 1. (Note 3) The storage unit stores, as correction information, the current error between the steady-state value of the drain current corresponding to the average value of the gate voltage during a predetermined time interval in the transient response, and the average value of the transient value of the drain current during the time interval. Wireless communication device as described in Appendix 1 or Appendix 2. (Note 4) The storage unit stores, as correction information, the correspondence between the amplitudes of the plurality of calibration signals and the current errors in the plurality of time intervals as a table. Wireless communication device as described in Appendix 3. (Note 5) The calibration signal output unit outputs a continuous wave having a constant amplitude and frequency as the calibration signal. A wireless communication device as described in any one of the items from Appendix 1 to Appendix 4. (Note 6) The envelope detection unit detects the amplitude of the transmission signal input to the gate terminal. A wireless communication device as described in any one of the items from Appendix 1 to Appendix 5. (Note 7) The envelope detection unit detects the amplitude of the transmitted signal output from the drain terminal. A wireless communication device as described in any one of the items from Appendix 1 to Appendix 5. (Note 8) The aforementioned amplifier is an amplifier that uses a GaN-FET. A wireless communication device as described in any one of the items from Appendix 1 to Appendix 7. (Note 9) Wireless communication device, The steps include applying a bias voltage to the gate terminal of an amplifier that amplifies the transmitted signal, The steps include inputting a calibration signal to the gate terminal, A step of storing static characteristics showing the relationship between the gate voltage of the gate terminal and the steady-state value of the drain current flowing through the drain terminal when an arbitrary bias voltage is applied, and correction information for correcting the transient value determined by the transient response of the drain current when one or more calibration signals are input to the gate terminal and a set voltage is applied to the expected value, The step of detecting the amplitude of the transmission signal, A step of calculating the correction amount of the gate voltage to correct the transient value of the drain current when the transmission signal is input to the gate terminal and the set voltage is applied, based on the static characteristics, the correction information, and the amplitude. The steps of setting the correction amount and executing Wireless communication method. (Note 10) The steps include applying a bias voltage to the gate terminal of an amplifier that amplifies the transmitted signal, The steps include inputting a calibration signal to the gate terminal, A step of storing static characteristics showing the relationship between the gate voltage of the gate terminal and the steady-state value of the drain current flowing through the drain terminal when an arbitrary bias voltage is applied, and correction information for correcting the transient value determined by the transient response of the drain current when one or more calibration signals are input to the gate terminal and a set voltage is applied to the expected value, The step of detecting the amplitude of the transmission signal, A step of calculating the correction amount of the gate voltage to correct the transient value of the drain current when the transmission signal is input to the gate terminal and the set voltage is applied, based on the static characteristics, the correction information, and the amplitude. The steps include setting the correction amount, A program that causes a computer to execute something.

[0136] Some or all of the elements (e.g., configuration and function) described in Appendices 2 to 8 that are dependent on Appendice 1 may also be dependent on Appendices 9 and 10 in the same way as those described in Appendices 2 to 8. Some or all of the elements described in any appendice may be applicable to various hardware, software, recording means, systems, and methods for recording software. [Explanation of symbols]

[0137] 1. Wireless communication device 11 Amplifier 12 Bias voltage application section 13 Calibration signal output section 14 Storage section 15 Envelope detection section 16 Correction amount calculation section 17 Correction Amount Setting Section 100 Wireless communication devices 101 Transmit signal output section 102 Calibration signal / voltage output section 103 Envelope detection section 104 Time Management Department 105 Transient phenomenon estimation section 106 Storage section 107 Correction amount setting section 108 Amplifier 109 DPD signal processing unit 110 DPD calculation unit 111 CFR 112 switches 113 switches 114 DAC 115 DAC 116 Synthesis section 117 buffers 118 drivers 119 Differential Amplifier 120 couplers 121 Attenuator 122 ADC 123 ADC 124 Output load 200 Wireless communication devices 300 Wireless communication devices 400 Wireless communication devices 401 Processor 402 memory

Claims

1. An amplifier equipped with a gate terminal, drain terminal, and source terminal, which amplifies the transmitted signal, A bias voltage application unit that applies a bias voltage to the gate terminal, A calibration signal output unit that outputs a calibration signal input to the gate terminal, A storage unit that stores static characteristics showing the relationship between the gate voltage of the gate terminal and the steady-state value of the drain current flowing through the drain terminal when any bias voltage is applied, and correction information for correcting the transient value determined by the transient response of the drain current when one or more calibration signals are input to the gate terminal and a set voltage is applied to the expected value, An envelope detection unit for detecting the amplitude of the transmitted signal, A correction amount calculation unit calculates a correction amount for the gate voltage that corrects the transient value of the drain current when the transmission signal is input to the gate terminal and the set voltage is applied, based on the static characteristics, the correction information, and the amplitude. A correction amount setting unit for setting the correction amount to the bias voltage application unit, A wireless communication device equipped with the following features.

2. The calibration signal output unit outputs a plurality of calibration signals having different amplitudes. The storage unit stores the correction information when the plurality of calibration signals are input. The correction amount calculation unit calculates the difference between the gate voltage calculated based on the static characteristics when the calibration signal having the amplitude corresponding to the amplitude of the transmission signal is input and the set voltage is applied, and the gate voltage at which the transient value of the drain current is the steady-state value, as the correction amount. The wireless communication device according to claim 1.

3. The storage unit stores, as correction information, the current error between the steady-state value of the drain current corresponding to the average value of the gate voltage during a predetermined time interval in the transient response, and the average value of the transient value of the drain current during the time interval. A wireless communication device according to claim 1 or claim 2.

4. The storage unit stores, as correction information, the correspondence between the amplitudes of the plurality of calibration signals and the current errors in the plurality of time intervals as a table. The wireless communication device according to claim 3.

5. The calibration signal output unit outputs a continuous wave having a constant amplitude and frequency as the calibration signal. The wireless communication device according to claim 1.

6. The envelope detection unit detects the amplitude of the transmission signal input to the gate terminal. The wireless communication device according to claim 1.

7. The envelope detection unit detects the amplitude of the transmitted signal output from the drain terminal. The wireless communication device according to claim 1.

8. The aforementioned amplifier is an amplifier that uses a GaN-FET. The wireless communication device according to claim 1.

9. Wireless communication device, The steps include applying a bias voltage to the gate terminal of an amplifier that amplifies the transmitted signal, The steps include inputting a calibration signal to the gate terminal, A step of storing static characteristics showing the relationship between the gate voltage of the gate terminal and the steady-state value of the drain current flowing through the drain terminal when an arbitrary bias voltage is applied, and correction information for correcting the transient value determined by the transient response of the drain current when one or more calibration signals are input to the gate terminal and a set voltage is applied to the transient value to an expected value. The step of detecting the amplitude of the transmission signal, A step of calculating the correction amount of the gate voltage to correct the transient value of the drain current when the transmission signal is input to the gate terminal and the set voltage is applied, based on the static characteristics, the correction information, and the amplitude. The steps of setting the correction amount and executing Wireless communication method.

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