Signal processing device, wireless communication device, signal processing method and program

Abstract

A signal processing device (10) according to the present disclosure comprises an adjustment unit (11) that adjusts one or both of an input signal and a calibration signal, which is for performing calibration between transmission systems, so that a difference between the signal power of the input signal and the signal power of the calibration signal is reduced. The signal processing device (10) also comprises a compensation unit (12) that performs distortion compensation between the input signal and the calibration signal. The signal processing device (10) further comprises an amplifier (13) that amplifies the input signal and the calibration signal, and an output unit (14) that outputs, to the amplifier (13), the input signal and the calibration signal that have been adjusted by the adjustment unit (11). Thus, provided are a signal processing device, a wireless communication device, a signal processing method, and a program that suppress a nonlinear distortion due to an amplifier and a distortion due to the memory effect of an amplifier in a calibration signal.

Description

[Technical field]

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

[0002] Mobile phone base station equipment uses a technology called digital beamforming to adjust the phase and amplitude of signals in the transmission system for each antenna using digital circuits. In order to form a beam that is output from the antenna in the desired direction, the phase and amplitude at each antenna end are adjusted to a predetermined value. Therefore, calibration is required for the transmission system corresponding to each antenna.

[0003] When the DL signal level transmitted between the antennas is different, the DL calibration signal exhibits nonlinear distortion and distortion due to memory effect depending on the DL signal level, and the calibration accuracy differs between the antennas. For this reason, an increasing number of base station devices perform digital pre-distortion (DPD). DPD is a process in which a distortion component having an inverse characteristic to the distortion characteristic caused by the power amplifier is superimposed on a transmission signal before being input to the power amplifier in order to improve the distortion characteristic caused by the power amplifier. By superimposing the distortion component having an inverse characteristic on this transmission signal, the distortion of the transmission signal that has passed through the power amplifier is suppressed, and the distortion characteristic caused by the power amplifier is corrected. However, whether DPD is enabled or disabled, the calibration accuracy differs, and it is necessary to clarify the influence of the nonlinear distortion of the amplifier and the DPD compensation process that affect the DL calibration signal.

[0004] Patent Document 1 discloses a technique for suppressing nonlinear distortion caused by an amplifier in a wireless communication system by providing a DPD in a stage preceding the amplifier. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-111958 A Summary of the Invention

[0006] Some amplifiers have a memory effect in their input / output characteristics, which occurs when the output signal of the amplifier depends on the history of past input signals. Due to the memory effect, the output signal for an input signal may not be fixed and may depend on the past input signal. Due to this memory effect, when a DL calibration signal is input to the amplifier during calibration operation of wireless communication settings, the DL calibration signal that is amplified and output by the amplifier reflects the memory effect.

[0007] In the technique disclosed in Patent Document 1, suppression of the memory effect by DPD is performed on the DL signal. Therefore, the memory effect and nonlinear distortion of the transmission amplifier remain in the DL calibration signal, and there is a possibility that accurate calibration cannot be performed.

[0008] The present disclosure has been made to solve such problems, and aims to provide a signal processing device, a wireless communication device, a signal processing method, and a program that suppress nonlinear distortion caused by an amplifier and distortion caused by the memory effect of the amplifier in a calibration signal.

[0009] The signal processing device according to the present disclosure includes an adjustment unit that adjusts one or both of the input signal and the calibration signal so as to reduce a difference between the signal power of the input signal and the signal power of a calibration signal that performs calibration between transmission systems, a compensation unit that performs distortion compensation for the input signal and the calibration signal, an amplifier that amplifies the input signal and the calibration signal, and an output unit that outputs the input signal and the calibration signal adjusted by the adjustment unit to the amplifier.

[0010] The wireless communication device according to the present disclosure includes an adjustment means for adjusting one or both of an input signal and a calibration signal so as to reduce a difference between the signal power of the input signal and the signal power of a calibration signal for performing calibration between transmission systems, a compensation means for performing distortion compensation for the input signal and the calibration signal, an amplifier for amplifying the input signal and the calibration signal, and an output means for outputting the input signal and the calibration signal adjusted by the adjustment means to the amplifier.

[0011] The signal processing method according to the present disclosure includes an adjustment step of adjusting one or both of the input signal and the calibration signal so that a difference between the signal power of the input signal and the signal power of a calibration signal that performs calibration between transmission systems is reduced, a compensation step of performing distortion compensation for the input signal and the calibration signal, an amplification step of amplifying the input signal and the calibration signal, and an output step of outputting the input signal and the calibration signal adjusted by the adjustment unit to the amplifier.

[0012] The program according to the present disclosure causes a signal processing device to perform an adjustment process for adjusting either or both of an input signal and a calibration signal so as to reduce a difference between the signal power of the input signal and the signal power of a calibration signal that performs calibration between transmission systems, and an output process for outputting the input signal and the calibration signal adjusted by the adjustment unit to an amplifier.

[0013] According to the present disclosure, it is possible to provide a signal processing device, a wireless communication device, a signal processing method, and a program that suppress nonlinear distortion caused by an amplifier and distortion caused by the memory effect of the amplifier in a calibration signal. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a configuration diagram of a signal processing device according to a first embodiment of the present disclosure. [Diagram 2] FIG. 11 is a conceptual configuration diagram of a signal processing device according to a second embodiment of the present disclosure. [Diagram 3] FIG. 11 is a block diagram showing a configuration of a wireless communication device according to a second embodiment of the present disclosure. [Figure 4] FIG. 11 is a block diagram showing a configuration of a BB unit according to a second embodiment of the present disclosure. [Diagram 5] FIG. 11 is a block diagram showing a configuration of an FE unit according to a second embodiment of the present disclosure. [Figure 6] 11A to 11C are diagrams illustrating power levels of a wireless communication device at each timing of DL and UL according to the second embodiment of the present disclosure. [Figure 7] FIG. 11 is a diagram illustrating an example of a frequency allocation of DL-CAL signals according to the second embodiment of the present disclosure. [Figure 8] FIG. 2 shows an example of a related antenna arrangement. [Figure 9] FIG. 2 is a diagram showing an example of the AM-AM characteristics of a related transmission amplifier. [Figure 10] FIG. 2 is a diagram showing an example of a phase difference between associated antennas; [Figure 11] FIG. 13 is a diagram showing the angular spectrum of the horizontal radiation pattern when a radio signal is output in accordance with related data beamforming. [Figure 12] FIG. 2 illustrates an example of the AM-AM characteristics that an associated amplifier imparts to a signal. [Figure 13] FIG. 2 illustrates an example of the AM-PM characteristics that an associated amplifier imparts to a signal. [Figure 14] FIG. 11 is a diagram illustrating an example of an AM-AM characteristic after a DPD compensation process according to the second embodiment of the present disclosure. [Figure 15] FIG. 11 is a diagram illustrating an example of AM-PM characteristics after DPD compensation processing according to the second embodiment of the present disclosure. [Figure 16] FIG. 11 is a diagram illustrating an example of a frequency bandwidth of a DL signal according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments will be described with reference to the drawings. Note that the drawings are simplified, and the technical scope of the embodiments should not be interpreted narrowly based on the description in the drawings. Also, the same elements are given the same reference numerals, and duplicated explanations will be omitted.

[0016] <Embodiment 1> This embodiment will be described with reference to Fig. 1. Fig. 1 is a configuration diagram of a signal processing device 10 according to this embodiment.

[0017] The signal processing device 10 in this embodiment includes an adjustment section 11, a compensation section 12, an amplifier 13, and an output section 14.

[0018] The adjustment unit 11 adjusts either or both of the input signal and the calibration signal so as to reduce the difference between the signal power of the input signal and the signal power of the calibration signal that performs calibration between the transmission systems. The compensation unit 12 performs distortion compensation for the input signal and the calibration signal. The amplifier 13 amplifies the input signal and the calibration signal. The output unit 14 outputs the input signal and the calibration signal adjusted by the adjustment unit 11 to the amplifier 13.

[0019] According to the signal processing device 10 of this embodiment, it is possible to suppress nonlinear distortion caused by the amplifier and distortion caused by the memory effect of the amplifier in the calibration signal.

[0020] <Embodiment 2> The signal processing device 100 of this embodiment will be described with reference to Fig. 2. Fig. 2 is a conceptual configuration diagram of the signal processing device 100 according to this embodiment.

[0021] The configuration of the signal processing device 100 in this embodiment will be described with reference to Fig. 2. Fig. 2 is a configuration diagram of the signal processing device 100 in this embodiment. The signal processing device 100 includes a DL signal monitor unit 101, a CAL-TRX 102, a distortion compensation unit 103, and an amplifier 104. Although Fig. 2 shows only one system of the signal processing device 100, it may include two or more systems.

[0022] The DL signal monitor unit 101 receives a DL signal as an input signal and performs a calculation on the DL signal to generate a DL calibration signal. The result of the calculation performed by the DL signal monitor unit 101 is input to the CAL-TRX 102 and the distortion compensation unit 103. As a specific example of the calculation performed in the DL signal monitor unit 101, the average power value of the DL signal is calculated. The average power value can be calculated by performing the calculation of the following equation 1 on I and Q at any time of the DL signal. I and Q respectively indicate the signal power on the sine axis and cosine axis of the DL signal.

number

[0023] The calculation of the average power value is executed at least during a calibration operation of the signal processing device 100. The calibration operation will be described later.

[0024] The CAL-TRX 102 generates a DL calibration signal based on the result of the calculation performed by the DL signal monitor unit 101. The CAL-TRX 102 inputs the DL calibration signal to the distortion compensation unit 103 during the calibration operation.

[0025] The distortion compensation unit 103 receives the received DL signal and DL calibration signal, and performs distortion compensation processing to compensate for nonlinear distortion and memory effect generated by the amplifier 104 for each signal. The distortion compensation processing is performed using DPD (Digital Pre-Distortion). The DL calibration signal is subjected to DPD compensation processing in the distortion compensation unit 103 using a stored LUT (Look Up Table). The DL calibration signal output from the distortion compensation unit 103 is input to the amplifier 104.

[0026] More specifically, the distortion compensation unit 103 performs a process of making a signal output from the amplifier 104 equal to a signal input to a DPD (Digital Pre Distortion) in order to suppress the influence of nonlinear distortion and memory effect that the amplifier 104 gives to the input signal. DPD compensation coefficients for distortion compensation related to amplitude and phase are stored inside the DPD. The distortion compensation unit 103 performs DPD compensation processing on the input signal using the selected DPD compensation coefficient. For example, the distortion compensation unit 103 stores an LUT in which the IQ (In-Phase / Quadrature-Phase) value of the input signal and the DPD compensation coefficient corresponding to the value are associated. The distortion compensation unit 103 determines the value of the input signal and performs DPD compensation processing. This DPD compensation processing updates the DPD compensation coefficient as appropriate. The DPD compensation coefficient is a coefficient for compensating for nonlinear AM-AM / AM-PM (Amplitude Modulation-Phase Modeling), which causes nonlinear distortion of the amplifier 104. The distortion compensation unit 103 selects appropriate DPD compensation coefficients for amplitude and phase based on the characteristics of the input signal.

[0027] Amplifier 104 amplifies and outputs the DL signal and DL calibration signal input from distortion compensation unit 103. The DL calibration signal output from amplifier 104 is input to CAL-TRX 102, which calculates DL-CAL by comparing the DL calibration signal input to distortion compensation unit 103 with the DL calibration signal output from amplifier 104. Here, the average power value of the DL calibration signal input to distortion compensation unit 103 is a signal calculated based on the average power value received from DL signal monitor unit 101 so as to be the same value as the average power value of the DL signal.

[0028] By the above-mentioned processing, the DL signal and the DL calibration signal are subjected to the same influence of nonlinear distortion and memory effect from amplifier 104, and the influence of nonlinear distortion and memory effect can be suppressed using the same DPD compensation coefficient.

[0029] Here, the wireless communication device 200 in this embodiment will be described with reference to Fig. 3. Fig. 3 is a block diagram showing the configuration of the wireless communication device 200 in this embodiment. The wireless communication device 200 is an example in which the signal processing device 100 shown in Fig. 2 is used as the wireless communication device 200.

[0030] The wireless communication device 200 is equipped with a massive element AAS (Active Antenna System) for 5G, and is a device provided in, for example, a base station device. As shown in FIG. 3, the wireless communication device 200 includes a BF-BB unit 220 and an AAS unit 210.

[0031] Here, the AAS unit 210 includes an optical transceiver 201, a TRX-BB unit 202, a FRONT-END unit 203, 32 antennas 204 including transceivers, a distributor / synthesizer 205, a SW (Switch) 206, and a CAL-TRX (calibration transceiver) 207. In this embodiment, the antenna 204 includes 32 antennas and transceivers, but the antennas 204 and transceivers may have an arrangement and number other than the number. In addition, a control unit (not shown) that controls each of these units may be included. In the following, an uplink (UL) refers to a communication path from a UE (User Equipment: terminal) (not shown) to the wireless communication device 200, and a downlink (DL) refers to a communication path from the wireless communication device 200 to the UE.

[0032] The BF-BB unit 220 is a baseband unit having a function of generating a beamforming signal. The BF-BB unit 220 stores a preset receiving system characteristic [CAL-RX (fixed)] inside. The BF-BB unit 220 also stores the characteristic TX#n*[CAL-RX] of each signal channel acquired by the operation of the TRX-BB unit 202 when the wireless communication device 200 is started and periodically, and updates it every time a new value is acquired. The BF-BB unit 220 uses these values ​​to perform communication in the DL direction by outputting a communication signal for communication to the AAS 210.

[0033] Next, a description will be given of each unit included in the AAS unit 210. The optical transceiver 201 performs photoelectric conversion and the inverse conversion of signals (e.g., multi-layer signals) transmitted and received between the BF-BB unit 220 and the TRX-BB unit 202. Between the optical transceiver 201 and the FRONT-END unit 203, the TRX-BB unit 202 mediates communication signals transmitted and received.

[0034] During DL calibration operation, the TRX-BB unit 202 generates a DL calibration signal, which is an IQ signal, and outputs it to the CAL-TRX 207 via the FRONT-END unit 203, the distributor / synthesizer 205, and the SW 206. Furthermore, during UL calibration operation, the TRX-BB unit 202 generates a UL calibration signal, which is an IQ signal, and outputs it directly to the CAL-TRX 207. In this way, the TRX-BB unit 202 functions as a transceiver baseband unit.

[0035] The TRX-BB unit 202 is a unit that mediates communication signals transmitted and received between the optical transceiver 201 and the FRONT-END unit 203, and includes 32 BB units 300#0-#31. Hereinafter, when there is no need to distinguish between the BB units 300#0-#31, they will simply be referred to as BB units 300.

[0036] The TRX-BB unit 202 executes a DL or UL calibration operation when the wireless communication device 200 is started and periodically to determine and store a calibration weight (hereinafter, referred to as a CAL weight) for the DL signal or UL signal, which is an input signal. This DL / UL-CAL weight is a value for correcting the variation in amplitude and phase of each TX or RX, which will be described later, and is determined by the DL / UL calibration operation based on the DL / UL-CAL signal.

[0037] When wireless communication device 200 transmits a spatially multiplexed signal consisting of multiple layers by data beamforming, the radio wave beam output to a UE with which wireless communication device 200 communicates may cause interference to UEs (other UEs) with which wireless communication device 200 does not communicate, and therefore it is preferable to reduce such interference. Therefore, when wireless communication device 200 forms a beam pattern for transmitting data in the direction of a certain UE and radiates the beam, a null is formed in the direction of the other UE as the pattern of the radiated beam. DL calibration is performed to ensure the desired angle and depth of the null.

[0038] When performing DL calibration, the TRX-BB unit 202 generates a DL calibration signal and transmits it to the CAL-TRX 207 via the FRONT-END unit 203, the distributor / synthesizer 205, and the SW 206. The CAL-TRX 207 outputs the DL calibration signal that has passed through its interior to the TRX-BB unit 202. The TRX-BB unit 202 measures the differences in amplitude and phase between the original DL calibration signal and the DL calibration signal received by the CAL-TRX 207, and determines the DL-CAL weights to be applied to each signal channel in order to inversely correct the differences.

[0039] Furthermore, when the TRX-BB unit 202 executes UL calibration, it generates a UL-CAL signal and inputs it to the CAL-TRX 207. The CAL-TRX 207 inputs the UL-CAL signal that has passed through the inside of the CAL network to the FE unit 400 via the SW 206 and the distributor / synthesizer 205. The receiver RX inputs the UL-CAL signal to the TRX-BB unit 202. The TRX-BB unit 202 measures the difference in amplitude and phase between the original UL-CAL signal and the UL-CAL signal transmitted by the CAL-TRX 207. The TRX-BB unit 202 determines the UL-CAL weight to be applied to the receiver RX of the TRX 401 of each FE unit 400 for inverse correction using the difference in amplitude and phase. In this way, the TRX-BB unit 202 functions as a transceiver baseband unit.

[0040] The FRONT-END section 203 includes 32 FE units 400#0 to #31. In the following, the FE units 400#0 to #31 will be simply referred to as FE units 400 unless there is a need to particularly distinguish between them.

[0041] The antennas 204 are provided corresponding to each TRX 401, each transmitting amplifier 402, and each receiving amplifier 406. The antennas 204 are polarized wave shared antennas having mutually orthogonal polarized waves of +45 degrees and -45 degrees, and for example, four antennas each having eight sets are provided, that is, a total of 32 antennas are provided. In this case, since one antenna element is used for two polarized waves, the number of antennas is equivalent to 64. Each antenna 204 transmits the RF signal received from each FE unit 400 to one or more UEs by a radio signal. At least one of a filter and a duplexer may be provided in front of each antenna 204.

[0042] When wireless communication device 200 performs DL calibration, distributor / synthesizer 205 combines the DL-CAL signals output from each SW 404, and outputs the combined DL-CAL signal to SW 206. When wireless communication device 200 performs UL calibration, distributor / synthesizer 205 distributes the UL-CAL signal output from SW 206, and outputs the distributed UL-CAL signal to each SW 404.

[0043] SW206 is a switch for switching the signal direction. When wireless communication device 200 executes DL calibration, SW206 outputs the DL-CAL signal output from distributor / synthesizer 205 to SW206. When wireless communication device 200 executes UL calibration, SW206 outputs the UL-CAL signal output from SW206 to distributor / synthesizer 205.

[0044] When the wireless communication device 200 executes DL calibration, the CAL-TRX 207 converts the DL-CAL signal (RF signal) output from the SW 206 into a DL-CAL signal (IQ signal). Then, the CAL-TRX 207 outputs the converted DL-CAL signal to the TRX-BB unit 202.

[0045] Furthermore, when wireless communication device 200 executes UL calibration, CAL-TRX 207 converts a UL-CAL signal (IQ signal) output from TRX-BB unit 202 into a UL-CAL signal (RF signal), and outputs the converted UL-CAL signal to SW 206. Note that, like TRX 401, CAL-TRX 207 may include a transmitter and a receiver (not shown).

[0046] Here, the configuration of the BB unit 300 will be described with reference to Fig. 4. Fig. 4 is a block diagram showing the configuration of the BB unit 300 in this embodiment.

[0047] The BB unit 300 includes a DL signal monitor unit 301, a CFR processing unit 302, and a DPD processing unit 303. Each of the BB units 300#0 to #31 has the same configuration as the BB unit 300 shown in FIG.

[0048] The CFR processing unit 302 limits the IQ signal (multi-layer signal) output from the BF-BB unit 220 and input via the optical transceiver 201 using a CFR threshold, which is a threshold for suppressing the maximum power component. Specifically, the CFR processing unit 302 suppresses the maximum power component that is equal to or less than the CFR threshold, among the amplitude components in the input multi-layer signal, and outputs the signal amplitude components that exceed the peak power level set by the CFR threshold to the DPD processing unit 303.

[0049] The reason why the peak level is suppressed in CFR processing unit 302 is as follows. If the peak level is not suppressed, a transmission signal having a high peak level may be output to transmission amplifier 402 downstream of CFR processing unit 302. In that case, hard clipping occurs at the saturation output level of transmission amplifier 402, causing nonlinear distortion components of high-order intermodulation, and DPD processing unit 303 may not be able to sufficiently compensate for this nonlinear distortion component. To avoid this state, CFR processing unit 302 limits the peak level of the transmission signal input to transmission amplifier 402, and adjusts the transmission signal so that the output level of transmission amplifier 402 does not exceed the saturation level.

[0050] The DPD processing unit 303 is provided between each CFR processing unit 302 and each TRX 401. The DPD processing unit 303 compares the IQ signal (multiple layer signal) output from the CFR processing unit 302 with the IR signal (multiple layer signal) returned via the FB (Feedback) path and to which nonlinear distortion based on the nonlinearity of the transmission amplifier 402 has been added. The DPD processing unit 303 performs compensation by applying weighting that inversely corrects the nonlinearity to the input signal, in order to compensate for nonlinear distortion in the input / output characteristics of AM-AM / AM-PM generated in the transmission amplifier 402, based on this comparison.

[0051] The DPD processing unit 303 performs DPD compensation processing to compensate the amplitude and phase of the IQ signal for wireless communication output from the CFR processing unit 302 based on a DPD compensation coefficient that indicates the inverse characteristic of the input / output characteristic of the downstream amplifier 302, and outputs the signal that has been subjected to the DPD compensation processing as a TR signal to the FRONT-END unit 203. By providing the DPD processing unit 303 for each TRX 401, it is possible to execute DPD compensation processing based on the characteristics of each TRX 401. This DPD compensation processing is performed to suppress nonlinear distortion radiation and improve the SINR (Signal to Interference and Noise Ratio) performance of the DL signal. The EVM (Error Vector Magnitude) and ACLR (Adjacent Channel Leakage Ratio) of the transmission amplifier 402 can also be improved by the DPD compensation processing.

[0052] The configuration of the FE unit 400 will be described below with reference to Fig. 5. Fig. 5 is a block diagram showing the configuration of the FE unit 400 in this embodiment.

[0053] FE unit 400 includes a TRX 401, a transmission amplifier 402, a directional coupler 403, a SW 404, an ORX (Observation Receiver) 405, and a receiving amplifier 406. Each of FE units 400#0 to #31 has the same configuration as FE unit 400 shown in FIG.

[0054] The TRX 401 is a transceiver, and includes a transmitter TX and a receiver RX, not shown. The transmitter TX converts an IQ signal received from the TRX-BB unit 202 into an RF signal, and outputs the RF signal to the antenna 204 or the CAL-TRX 207. When the wireless communication device 200 transmits a wireless signal, the transmitter TX outputs the RF signal to the antenna 204, and when performing DL calibration, the transmitter TX outputs a DL-CAL signal (RF signal) to the CAL-TRX 207 via the distributor / synthesizer 205.

[0055] The receiver TX converts an RF signal received from the antenna 204 or the CAL-TRX 207 into an IQ signal and outputs it to the TRX-BB unit 202. When the wireless communication device 200 receives a radio signal from the UE, the TRX 401 receives the RF signal from the antenna 204. When UL calibration is performed, the TRX 401 receives a UL-CAL signal (RF signal) from the CAL-TRX 207 via the distributor / synthesizer 205. Then, the TRX 401 converts the received UL-CAL signal into a UL-CAL signal (IQ signal) and outputs the converted UL-CAL signal to the BF-BB unit 220 via the TRX-BB unit 202.

[0056] Each transmission amplifier 402 is disposed between each antenna 204 and a TRX 401 provided corresponding to each antenna 204. The transmission amplifier 402 amplifies an RF signal (a signal for wireless communication or a DL-CAL signal) output from the TRX 401, and outputs the amplified signal to the directional coupler 403.

[0057] Each directional coupler 403 is a coupler provided between each transmission amplifier 402 and each antenna 204. The directional coupler 403 outputs the RF signal output from each transmission amplifier 402 to the antenna 204, and also outputs the RF signal to the corresponding ORX 405. The ORX 405 outputs the output RF signal to the DPD processing unit 303 via the FB path, and the DPD processing unit 303 receives the output RF signal and performs the above-mentioned processing.

[0058] The SW404 is a switch that switches the signal input or output to the TRX401 based on a control signal from the control unit of the AAS unit 210. That is, the connection destination of the FRONT-END unit 203 is switched by the control of the AAS unit 210. Specifically, when the wireless communication device 200 is in wireless communication, the SW404 is controlled so that the FRONT-END unit 203 and the antenna 204 are connected and the FRONT-END unit 203 and the CAL-TRX 207 are not connected in each of the signal channels 0 to #31. As a result, during data transmission, the RF signal from the TRX401 is output to the antenna 204, while during data reception, the SW404 causes the RF signal from the antenna 204 to be output to the TRX401.

[0059] On the other hand, when the wireless communication device 200 performs DL / UL calibration, the SW404 is controlled so that in each of the signal channels #0 to #31, the FRONT-END unit 203 and the CAL-TRX 207 are connected and the FRONT-END unit 203 and the antenna 204 are not connected. In other words, the TRX 401 and the distributor / synthesizer 205 are connected, while the connection between the antenna 204 and the TRX 401 is released. When the wireless communication device 200 performs DL calibration, the DL-CAL signal output from the transmission amplifier 402 is input to the distributor / synthesizer 205. When the wireless communication device 200 performs UL calibration, the UL-CAL signal output from the distributor / synthesizer 205 is input to the receiving amplifier 406.

[0060] The wireless communication device 200 prevents the DL / UL-CAL signal processed in each TRX 401 from being affected by interference from other systems by controlling each SW 404. That is, since the DL / UL-CAL signal processed in each TRX 401 does not include an interference component, the AAS unit 210 can accurately determine the CAL weight to be applied to each TRX 401. Furthermore, when the DL / UL calibration is completed, the control unit of the AAS unit 210 controls each SW 404 so that each TRX 401 and each antenna 204 are connected.

[0061] Each receiving amplifier 406 amplifies the input RF signal (a signal for wireless communication or a UL-CAL signal) and outputs it to the corresponding TRX401.

[0062] <Regarding the DL calibration operation> Here, the DL calibration operation of the wireless communication device 200 will be described.

[0063] First, the DL calibration operation will be described. First, the TRX-BB unit 202 outputs a preset DL-CAL signal (IQ signal) to the FRONT-END unit 203. Each TRX401 (transmitter TX) in the FRONT-END unit 203 converts the DL-CAL signal (IQ signal) into a DL-CAL signal (RF signal). The DL-CAL signal (RF signal) converted in each TRX401 is output to the distribution combiner 205 via the transmission amplifier 402 and the SW404 and is combined in the distribution combiner 205. The DL-CAL signal combined in the distribution combiner 205 is input to the CAL-TRX207 via the SW206. Note that the AAS unit 210 may output the DL-CAL signal with timing separated for each signal channel.

[0064] The CAL-TRX207 converts the received DL-CAL signal (RF signal) into a DL-CAL signal (IQ signal) and outputs it to the TRX-BB unit 202. The DL-CAL signal sent from the CAL-TRX207 is in a state where the DL-CAL signals sent from each TRX401#n are synthesized by frequency multiplexing. Therefore, the TRX-BB unit 202 frequency-separates the DL-CAL signal sent from the CAL-TRX207 by FFT (Fast Fourier Transform). Then, the TRX-BB unit 202 extracts the DL-CAL signal and calculates the DL-CAL weight for each of the signal channels #0 to #31.

[0065] Specifically, the TRX-BB unit 202 learns the amplitude and phase variations of the DL-CAL signal for each signal channel by measuring the differences in amplitude and phase between the DL-CAL signal transmitted for each signal channel and the original (i.e., before transmission) DL-CAL signal. Based on the learning results, the TRX-BB unit 202 calculates the DL-CAL weights for each TRX401#n.

[0066] Here, the DL-CAL weight for each TRX401#n is the product of the transmission system characteristics (amplitude and phase characteristics) [TX#n] of TRX401#n and the reception system characteristics (amplitude and phase characteristics) [CAL-RX] of CAL-TRX207, as represented by Equation 2 below.

Equation

[0067] In the above process, the DL calibration learning is completed. The BF-BB unit 220 stores this DL-CAL weight internally. Thereafter, during normal DL-related wireless communication, the BF-BB unit 220 outputs a weighted DL signal for each TRX401 using the above-described DL-CAL weight for that TRX401.

[0068] <Regarding the operation example of the DL operation> Subsequently, an operation example of the DL operation of the AAS unit 210 will be described. The BF-BB unit 220 generates a BF signal (IQ signal) in an internal circuit. Then, the generated BF signal is corrected for each of signal channels #0 to #31 using the above-described DL-CAL weight and output to the TRX-BB unit 202 via the optical transceiver 201. Note that the optical transceiver 201 may not be provided between the BF-BB unit 220 and the TRX-BB unit 202, and the BF-BB unit 220 and the TRX-BB unit 202 may be directly connected. In this case, the BF-BB unit 220 is configured to be connected to an external DU (Distribution Unit) via the optical transceiver 201.

[0069] Specifically, the BF-BB unit 220 multiplies the BF signal by a fraction whose denominator is the DL-CAL weight and whose numerator is the fixed receiving system characteristic [CAL-RX (fixed)] of the CAL-TRX 207. The corrected BF signal is expressed by the following formula 3. Note that [CAL-RX (fixed)] is stored in advance in a storage unit (not shown) of the BF-BB unit 220.

number

[0070] The corrected BF signal is converted from an IQ signal to an RF signal in each TRX 401#n of the TRX-BB unit 202 and transmitted, amplified in each transmission amplifier 402#n, and output from the FRONT-END unit 203. The BF signal output from the FRONT-END unit 203 passes through each TRX 401#n and is expressed by the following equation 4.

number

[0071] If equation 4 is simplified by eliminating [TX#n], it can be expressed as equation 5 below.

number

[0072] In formula 5, if [CAL-RX(fixed)]=[CAL-RX], the BF signal is in an ideal state, and the BF signal in the ideal state is transmitted from each antenna 204#n. Note that in order for [CAL-RX(fixed)]=[CAL-RX], the stability of CAL-RX is important.

[0073] By performing the above operations, it becomes possible to compensate for variations in the amplitude and phase identification of each transmitter TX#n. Through this DL calibration operation, when transmitting spatial multiplexed radio signals of multiple layers by data beamforming, it is possible to accurately set the angle and depth of the nulls formed in the directions of other UEs. Also, it is possible to suppress the occurrence of non-linear distortion radiation caused by third-order intermodulation distortion in each direction of space.

[0074] Note that the update of the DL-CAL weights shown above may be performed between the transmission of radio signals by fan beamforming (beam pattern shape equivalent to omni-directional broad beamforming) and the transmission of radio signals by data beamforming, as will be described later. Also, the update of the DL-CAL weights may be performed periodically. Furthermore, the wireless communication device 200 may update the DL-CAL weights triggered by the sensor of the wireless communication device 200 detecting an environmental change (e.g., temperature change) or a change in the signal over time. The update period in this case may be, for example, a period of 1 minute or more, but is not limited to this.

[0075] <Regarding the UL calibration operation> Next, the UL calibration operation when the UL signal is used as the input signal will be described. The TRX-BB unit 202 directly outputs a preset UL-CAL signal (IQ signal) to the CAL-TRX 207. The CAL-TRX 207 converts the UL-CAL signal (IQ signal) into a UL-CAL signal (RF signal). The UL-CAL signal (RF signal) converted in the CAL-TRX 207 is output to the distribution combiner 205 via the SW 206 and is distributed in the distribution combiner 205. The UL-CAL signal distributed in the distribution combiner 205 is output to each TRX 401 via each SW 404 and the reception amplifier 406. Each TRX 401 converts the UL-CAL signal (RF signal) into a UL-CAL signal (IQ signal) and outputs it to the TRX-BB unit 202.

[0076] The TRX-BB unit 202 measures the difference in amplitude and phase between the UL-CAL signal of the UL-CAL signal received by each TRX 401 and the original UL-CAL signal, and learns the variation in amplitude and phase of the UL-CAL signal. The TRX-BB unit 202 calculates the UL-CAL weight of each TRX 401 based on the learning result.

[0077] The above process ends the UL calibration operation. The BF-BB unit 220 stores the UL-CAL weights internally. Thereafter, during normal UL wireless communication, the BF-BB unit 220 outputs, to each TRX 401, a UL signal weighted by the above-mentioned UL-CAL weight.

[0078] <Calibration execution timing> Next, the timing of DL and UL calibration execution will be described. As described above, the wireless communication device 200 may be a wireless communication device that performs wireless communication in TDD (Time Division Duplex: TDD communication method) mode. The TDD mode is a communication method in which the same frequency is used in uplink and downlink (UL / DL) to perform transmission and reception by switching DL communication and UL communication over time. A DL subframe is transmitted in DL communication, and a UL subframe is transmitted in UL communication. In addition, at the timing of switching from DL communication to UL communication, a special subframe is transmitted. The special subframe is a subframe that is configured with a DwPTS (Downlink Pilot Time Slot), an UpPTS (Uplink Pilot Time Slot), and a GP (Guard Period). The DwPTS is a field reserved for DL ​​communication, the UpPTS is a field reserved for UL communication, and the GP is a field in which neither DL communication nor UL communication is performed.

[0079] In the wireless communication device 200, during a time period of a GP (Guard Period) in which neither DL communication nor UL communication is performed, the transmitter TX and the receiver RX in the TRX 401 are exclusively in an OFF / ON state. The wireless communication device 200 performs at least one of DL calibration and UL calibration, for example, during the time period of the GP of a special subframe.

[0080] Here, the transmitter power level during calibration will be described with reference to Fig. 6. Fig. 6 is a diagram showing the power level of wireless communication device 200 at each timing of DL and UL. The horizontal axis of Fig. 6 indicates time, and the vertical axis indicates power level. A solid line L1 in Fig. 6 indicates the transition of the transmission power level of transmitter TX of wireless communication device 200.

[0081] According to FIG. 6, it can be seen that the transmission power level, which is the off power level in the initial transmitter off section, passes through a transmitter transition section, becomes the on power level in the transmitter on section, and then passes through another transmitter transition section, and becomes the off power level in the transmitter off section.

[0082] In Fig. 6, the time period marked "UL transmission" indicates the time period for UL communication. The time period marked "DL transmission" indicates the time period for DL ​​communication. The time period marked "GP or UL transmission" indicates the time period for GP or UL communication.

[0083] The wireless communication device 200 performs DL calibration or UL calibration during the time interval (transmitter transition interval) of the GP in the special subframe. This time interval is included within the uplink-downlink frame timing interval. As shown in FIG. 6, within the GP, the time interval during which the transmitter TX in FIG. 6(a) transitions from OFF to ON and the time interval during which it transitions from ON to OFF in FIG. 6(b) are, for example, 10 μs. The wireless communication device 200 can perform the above-described DL calibration or UL calibration in at least one of the intervals in FIG. 6(a) or (b). That is, in this example, the output time of the DL / UL-CAL signal may be within 10 μs. Also, the main purpose of the calibration is to unify the frequency characteristics of the amplitude and phase in the linear region among the 32 TRX401s. Therefore, it is important to lower the power of the DL / UL-CAL signal to a level that does not undergo non-linear degradation and can ensure the required SNR (Signal-to-Noise Ratio) while being below the maximum rating. In this way, the DL-CAL weight, which is a value for correcting the variations in the amplitude and phase of each TX or RX, is periodically calculated during the time interval of the GP and stored inside the BF-BB unit 220.

[0084] <Regarding the frequency arrangement of the DL-CAL signal> Here, the frequency arrangement of the DL-CAL signal will be described. Here, an example of the frequency arrangement of the DL-CAL signal with frequency orthogonality for each TRX#n will be used for the description. As shown in FIG. 3, an example of the frequency arrangement of the DL-CAL signal for each transmitter TX#n in the case where 32 TRX#n are provided will be described.

[0085] Referring to FIG. 7, an example of the frequency arrangement of the DL-CAL signal for each transmitter TX#n will be described. FIG. 7 is a diagram showing an example of the frequency arrangement of the DL-CAL signal.

[0086] In Fig. 7, in the frequency arrangement of the DL-CAL signal of one transmitter TX#n, the subcarriers used to transmit the DL-CAL signal are arranged at intervals of X [MHz]. In addition, between adjacent transmitters TX#n, the frequency arrangement of the DL-CAL signal is shifted in the frequency direction by Y [MHz]. fsc0 [MHz] is the reference frequency.

[0087] In the example shown in FIG. 7, the following two frequency allocation conditions A1 and A2 need to be satisfied. Frequency allocation condition A1: X [MHz]>Y [MHz] × (number of transmitters TX#n-1) is satisfied. Frequency allocation condition A2: Within the signal bandwidth, the frequency “sc0= fsc0 The frequency "sck=fsc0+31Y+kX[MHz]" of the uppermost subcarrier sck of the DL-CAL signal for transmitter TX#31 is entered from the frequency "sck=fsc0+31Y+kX[MHz]".

[0088] <Issues related to related technologies> Next, problems associated with the related technology will be described. FIG. 8 shows an example of the arrangement of antennas 204#0 to #31 in the related technology. The numbers shown in FIG. 8 indicate the numbers of the antennas 204, and for example, "1" indicates that antenna "#1" is arranged. In the example of FIG. 8, eight antennas are arranged in four rows, and antennas 204 in the same row output the same wireless signal. For example, four antennas belonging to each of (a1), (a2), (b1), (b2), (c1), (c2), (d1), and (d2) in FIG. 8 output the same wireless signal. Therefore, the radio wave strength of the four antennas in these rows is approximately the same.

[0089] The antennas 204#0-#31 can transmit radio signals by, for example, fan beamforming and data beamforming. Here, the transmission of radio signals by fan beamforming means transmitting radio signals of approximately constant intensity in a range in front of the radio communication device 200 and in a horizontal direction from the front of the radio communication device 200, covering a predetermined angle, and is used for broadcast data transmission, for example. In contrast, the transmission of radio signals by data beamforming means transmitting radio signals of high intensity in front of the radio communication device 200 and in a certain angle direction in the horizontal direction, while forming a null in the direction of another UE and transmitting a radio signal of low intensity. This method of transmitting radio signals is used for data communication with a specific UE.

[0090] When the antennas 204#0 to #31 transmit radio signals by fan beam forming, for example, (a1) and (a2) output radio signals of the maximum rating, and (b1) and (b2), (c1) and (c2), and (d1) and (d2) output radio signals of increasing radio field strength in this order. That is, the strength of the output radio signals decreases from the center of the antenna shown in FIG. 8 to the outside. As an example, the BF-BB unit 220 outputs input signals of up to -14 dBFS (average) to the transmission amplifiers 402 corresponding to (a1) and (a2), and outputs input signals of up to -24 dBFS (average) to the transmission amplifiers 402 corresponding to (b1) and (b2).

[0091] The phases of the input signals to the transmission amplifier 402 corresponding to (a1), (a2), (c1), and (c2) are the same, and the phases of the input signals to the transmission amplifier 402 corresponding to (b1), (b2), (d1), and (d2) are inverted from the phases of the input signals to the transmission amplifier 402 corresponding to (a1), (a2), (c1), and (c2).

[0092] 9 is a graph showing an example of the AM-AM input / output characteristics of the transmission amplifier 402 corresponding to the antennas 204 of (a1), (a2), (b1), and (b2) in FIG. 8. The horizontal axis of FIG. 9 is the amplitude of the input signal, and the vertical axis of FIG. 9 is the amplitude of the output signal. The input / output characteristics of the transmission amplifier 402 corresponding to (a1) and (a2) are shown as in FIG. 9(a), and the input / output characteristics of the transmission amplifier 402 corresponding to (b1) and (b2) are shown as in FIG. 9(b). The ideal input / output characteristics of the transmission amplifier 402 are linear, and are shown as in FIG. 9(e). Note that the input / output characteristics (a) and (b) of the transmission amplifier 402 are not compensated for by the DPD processors 303.

[0093] Also, consider the case where a memory effect occurs in the AM-AM characteristics and AM-PM characteristics of transmitting amplifier 402, that is, a phenomenon in which the AM-AM characteristics and AM-PM characteristics change depending on the input / output levels that passed through transmitting amplifier 402 in the past time period and are maintained for a certain period of time. In this case, if a signal of -37 dBFS (average) is input as a DL-CAL signal to transmitting amplifier 402 as an input signal, the points indicating the corresponding output signal in the input / output characteristics (a) and (b) are (c) and (d).

[0094] 9, the input / output characteristics (a) and (b) have nonlinearity that deviates from the ideal input / output characteristics. In particular, the input / output characteristic (a) has a larger nonlinearity than the input / output characteristic (b). A DL-CAL signal having a small amplitude (intensity) is input to each transmission amplifier 402.

[0095] Similarly to the AM-AM input / output characteristics, the phase difference between the input signal and output signal of transmission amplifier 402 (AM-PM input / output characteristics) also has a significant difference when compared with ideal input / output characteristics (characteristics in which the phase difference is 0). The differences increase in the order of (a1) and (a2), (b1) and (b2), (c1) and (c2), and (d1) and (d2).

[0096] It may seem that the distortion due to the nonlinearity described above can be eliminated by compensating the input signal to the transmission amplifier 402. However, when the transmission amplifier 402 is, for example, a Doherty amplifier, which is a gallium nitride amplifier, a memory effect may occur in the AM-AM input / output characteristics and the AM-PM input / output characteristics. In this case, even if the input signal has changed and been compensated, the transmission amplifier 402 may output an output signal based on the input / output characteristics related to the input signal before compensation for a certain period of time due to the memory effect occurring in the transmission amplifier 402 itself.

[0097] In particular, when wireless communication device 200 transmits a wireless signal by fan beamforming, performs DL calibration, and then transmits a wireless signal by data beamforming, the following problem occurs.

[0098] When transmitting a radio signal by fan beamforming, the output of the transmission amplifier 402 varies in strength from the maximum rated output to low signal strength. At this stage, distortion due to the nonlinearity of each transmission amplifier 402 is compensated for by the corresponding DPD processor 303.

[0099] When performing DL calibration after emitting radio waves by data beamforming, the DL-CAL signal output by the BF-BB unit 220 has approximately the same output level between each transmitter TX, unlike the case of fan beamforming. However, due to the memory effect of the transmission amplifier 402, the AM-AM and AM-PM characteristics determined by the input / output characteristics during fan beamforming affect the DL-CAL signal output from each transmitter when passing through each transmission amplifier 402.

[0100] As an example, a signal with an average level of -37 dBFS is assumed as the DL-CAL signal. 0 dBFS corresponds to the maximum output level of the transmission DAC (Digital Analog Converter). As described above, when the DL-CAL signal is input to the transmission amplifier 402 in a state where the memory effect occurs, the points (c) and (d) showing the output signals corresponding to the input / output characteristics (a) and (b) in FIG. 9 are (c) and (d). Therefore, the DL-CAL signal in a state where the memory effect occurs has a gain difference compared to the ideal input / output characteristics. In addition, during the DL calibration operation using the DL-CAL signal, it is assumed that the wireless communication device 200 learns the frequency characteristics of the amplitude and phase of each transmitter in a linear region without nonlinearity and unifies and corrects the difference between each frequency characteristic. Therefore, since the DPD processing unit 303 is turned off, the distortion due to the nonlinearity of each transmission amplifier 402 is not compensated for by the corresponding DPD processing unit 303. Therefore, during the DL calibration operation, the DL-CAL weight is set so as to compensate for the difference in amplitude and phase between each transmitter TX caused by this memory effect.

[0101] In the next data slot, when the wireless communication device 200 transmits a radio signal by data beamforming, the output of each transmission amplifier 402 is at the maximum rating for transmitting data to the UE. That is, the radio signal output by the BF-BB unit 220 has substantially the same amplitude for each signal channel. Also, when the radio signal by data beamforming is transmitted, each DPD processor 303 is on, so that each DPD processor 303 attempts to compensate for distortion caused by the nonlinearity of the corresponding transmission amplifier 402.

[0102] However, as described above, the DL-CAL weights that were set in the previous DL calibration reflect the history of fan beamforming. Therefore, the output signals of each transmitting amplifier 402 should have had substantially the same amplitude, but due to the unnecessary DL-CAL weights, the amplitudes of the output signals of each transmitting amplifier 402 differ. In addition, a phase difference that should not exist in reality occurs in each transmitting amplifier 402. In this way, over-compensation or under-compensation occurs in the amplitude and phase of the wireless signal by data beamforming. This phenomenon continues until the DL-CAL weights are updated.

[0103] FIG. 10 is a diagram showing an example of the phase difference between the antennas. The horizontal axis of the graph in FIG. 10 indicates the number of the transmission amplifier 402, and the vertical axis of the graph indicates the phase difference amount from the transmission amplifiers 402#3, #4, #11, and #12 (corresponding to (a1) and (a2) in FIG. 8). FIG. 10 shows the phase shift amount between the radio signals of the data beamforming output by the transmission amplifier 402 when transmitting a radio signal in a state in which correction by unnecessary DL-CAL weights is performed by the above-mentioned processing in the configuration of the antenna 204 shown in FIG. 8. Note that while FIG. 10 shows the phase difference amount from the transmission amplifiers 402#0 to #15, the phase difference amount from the transmission amplifiers 402#16 to #31 (phase difference amount from the transmission amplifiers 402#19, #20, #27, and #28) is also shown in the same graph as FIG. 10.

[0104] Fig. 10 shows a case where, statistically, within a range of ±3σ where σ is the standard deviation, when the memory effect exists, the phase difference between each transmitter is a maximum of 11.6 degrees pp (phase-phase) in the case of (1), a maximum of 23.1 degrees pp in the case of (2), and a maximum of 34.6 degrees pp in the case of (3). The effect of this phase difference on data beamforming was verified by the following calculation. As shown in Fig. 9, the phase difference amount of the transmission amplifier 402 corresponding to the antennas 204 of (d1) and (d2) in Fig. 8 is the largest, and the phase difference amount becomes smaller as the transmission amplifiers 402 corresponding to (c1) and (c2), (b1) and (b2) are arranged.

[0105] Fig. 11 is a diagram showing the angular spectrum of a horizontal radiation pattern when a radio signal related to related data beamforming is output. The horizontal axis of the graph in Fig. 11 indicates the horizontal (left-right) angle from the front of wireless communication device 200, and the vertical axis of the graph indicates a normalized radiation power level when the output signal from the front of wireless communication device 200 is used as a reference. (1) to (3) in Fig. 11 are graphs showing angular spectrums when there are phase differences such as (1) to (3) in Fig. 10, and (0) in Fig. 11 shows the original angular spectrum without unnecessary DL-CAL weight.

[0106] As can be understood by referring to FIG. 11, the depth of the null point closest to the front of the wireless communication device 200 (first null depth) is 46 dB in the case of (0), 27 dB in the case of (1), 21 dB in the case of (2), and 17 dB in the case of (3). That is, the larger the phase difference, the shallower the null depth. That is, the DL SINR in the direction of each UE when transmitting a spatial multiplexed signal is deteriorated by this shallow null, that is, interference waves in beamforming to other UEs. The null depth determines the MU-MIMO performance of the wireless communication device 200. Therefore, the throughput of the cell when the wireless communication device 200 functions as a base station does not improve, and the communication quality deteriorates.

[0107] The wireless communication device 200 in this embodiment has a configuration capable of suppressing SINR degradation so that, when there is a memory effect in the nonlinear characteristics of the amplifier, the memory effect degrades the calibration accuracy and thereby prevents the SINR of the signal to each terminal from being degraded when transmitting a spatially multiplexed signal.

[0108] <Description of the Operation of the Signal Processing Device in the Present Embodiment> Here, a description will be given of the operation of the signal processing device 100 in this embodiment. When there is a nonlinear distortion and a memory effect of the amplifier 104, the signal processing device 100 uses DPD to suppress the influence of these on the DL calibration signal.

[0109] The nonlinear distortion and memory effect that amplifier 104 imparts to an input signal will be described with reference to Fig. 12 and Fig. 13. Fig. 12 is a diagram showing an example of the AM-AM characteristics that an associated amplifier imparts to a signal. Fig. 13 is a diagram showing an example of the AM-PM characteristics that an associated amplifier imparts to a signal.

[0110] The horizontal axis of FIG. 12 represents the input level, and the vertical axis represents the value obtained by dividing the output level by the input level. Therefore, the lower the value on the vertical axis, the lower the value amplified by the amplifier 104. The horizontal axis of FIG. 13 represents the input level, and the horizontal axis represents the value obtained by subtracting the phase of the input signal from the phase of the output signal. Therefore, the DPD compensation coefficient varies depending on the average level of the DL signal input to the amplifier 104, and the average level of the DL signal varies from time to time. Therefore, when the DL calibration signal is at a fixed level, the DL calibration signal cannot be compensated by DPD, which deteriorates the accuracy of the calibration. As shown in FIG. 12 and FIG. 13, the AM-AM / AM-PM characteristics are different from each other because the effects of nonlinear distortion and memory effect vary depending on the average power value input.

[0111] The average power value is calculated by inputting the DL signal to the DL signal monitor unit 301. The calculated average power value is calculated so that the DL calibration signal output from the CAL-TRX 207 is equal to the value received from the DL signal monitor unit 301. As a result, the DL signal and the DL calibration signal have the same average power value.

[0112] CFR processing unit 302 limits the peak levels of the input DL signal and DL calibration signal by a set threshold value, and inputs them to DPD processing unit 303. The DL signal and DL calibration signal input to DPD processing unit 303 undergo distortion compensation processing, and are input to TRX 401, where the IQ signal is converted into an RF (Radio Frequency) signal and input to transmission amplifier 402. The signal amplified by transmission amplifier 402 is input to ORX 405 via directional coupler 403, and fed back to DPD processing unit 303. DPD processing unit 303 calculates a DPD compensation coefficient for suppressing the influence of nonlinear distortion and memory effect of transmission amplifier 402 based on the fed back DL signal and DL calibration signal, and compensates for the DL signal and DL calibration signal.

[0113] By carrying out such processing, the DL signal and the DL calibration signal have the AM-AM / AM-PM characteristics shown in FIG. 14 and FIG. 15, making it possible to suppress the influence of nonlinear distortion and memory effect.

[0114] As described above, wireless communication device 200 can change the level of the DL calibration signal output from CAL-TRX 207 in accordance with the DL signal by adding DL signal monitor section 301 to BB unit 300 and connecting it to CAL-TRX 207. Therefore, wireless communication device 200 in this embodiment, i.e., signal processing device 100, can suppress nonlinear distortion caused by the amplifier and distortion caused by the memory effect of the amplifier in the calibration signal.

[0115] According to the wireless communication device 200 of this embodiment, it is possible to suppress nonlinear distortion caused by the amplifier and distortion due to the memory effect of the amplifier in the calibration signal.

[0116] <Embodiment 3> In the second embodiment, the calculation performed in the DL signal monitor unit 301 is the average level as shown in Equation 1, but in the present embodiment, any power value other than the average level is used.

[0117] The DL signal monitor unit 301 performs calculations for generating a calibration signal based on the input DL signal, and inputs the calculation results to the CAL-TRX 207. As will be described below, the calculations by the DL signal monitor unit 301 can be any power value that can be calculated from the DL signal, in addition to the average power value.

[0118] As a specific example, a method of calculating a bandwidth from a DL signal input to the DL signal monitor unit 301 will be described with reference to Fig. 16. Fig. 16 is a diagram showing an example of the frequency bandwidth of a DL signal according to this embodiment. When the DL signal input to the DL signal monitor unit 301 exists only partially relative to the signal bandwidth of the wireless communication device 200 as shown in Fig. 16, this bandwidth is calculated by FFT (Fast Fourier Transform) from the IQ value of the DL signal. The calculated bandwidth is input to the CAL-TRX 207, which selects a DL CAL signal from Fig. 7 that is common to the bandwidth of the received signal, and inputs it to the TRX-BB unit 202.

[0119] The AM-AM and AM-PM characteristics of the transmission amplifier 402 vary depending on the frequency. That is, the AM-AM and AM-PM characteristics change not only depending on the input level of the transmission amplifier 402 but also on the input frequency bandwidth.

[0120] Therefore, according to the wireless communication device 200 of this embodiment, the accuracy of the calibration can be improved by limiting the bandwidth of the DL-CAL signal to the same bandwidth as that of the DL signal.

[0121] <Other embodiments> The signal processing device 10 of the present disclosure includes, for example, an embodiment as a signal processing method. That is, the signal processing method includes an adjustment step of adjusting one or both of the input signal and the calibration signal so that a difference between the signal power of the input signal and the signal power of a calibration signal for performing calibration between transmission systems becomes small, a compensation step of performing distortion compensation for the input signal and the calibration signal, an amplification step of amplifying the input signal and the calibration signal, and an output step of outputting the input signal and the calibration signal adjusted by the adjustment unit to the amplifier.

[0122] In the above example, the program can be stored and provided to the computer using various types of non-transitory computer readable media. The non-transitory computer readable media includes various types of tangible storage media. The non-transitory computer readable media includes, for example, a magnetic recording medium, a magneto-optical recording medium, a CD-ROM (Read Only Memory), a CD-R, a CD-R / W, and a semiconductor memory. The semiconductor memory is, for example, a mask ROM, a PROM (Programmable ROM), an EPROM (Erasable PROM), a flash ROM, and a RAM (Random Access Memory). The program may also be provided to the computer by various types of transitory computer readable media. Examples of the transitory computer readable medium include an electric signal, an optical signal, and an electromagnetic wave. The transitory computer readable medium can provide the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

[0123] The above program causes the signal processing device 10 to execute an adjustment process for adjusting either or both of the input signal and the calibration signal so as to reduce the difference between the signal power of the input signal and the signal power of a calibration signal that performs calibration between the transmission systems, and an output process for outputting the input signal and the calibration signal adjusted by the adjustment unit to an amplifier.

[0124] The present disclosure is not limited to the above-described embodiment, and can be appropriately modified without departing from the spirit of the present disclosure. For example, some or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited to the following.

[0125] (Appendix 1) an adjustment unit that adjusts one or both of the input signal and the calibration signal so that a difference between a signal power of the input signal and a signal power of a calibration signal that performs calibration between the transmission systems becomes small; a compensation unit that performs distortion compensation between the input signal and the calibration signal; an amplifier for amplifying the input signal and the calibration signal; an output section that outputs the input signal adjusted by the adjustment section and a calibration signal to the amplifier; A signal processing device comprising: (Appendix 2) The adjustment unit adjusts the signal power of the calibration signal. 2. A signal processing device as claimed in claim 1. (Appendix 3) the adjustment unit adjusts the calibration signal based on average power values ​​of the input signal and the calibration signal, 3. A signal processing device as claimed in claim 2. (Appendix 4) the adjustment unit adjusts the signal power of the calibration signal by calculating a frequency bandwidth of the input signal by a Fast Fourier Transform (FFT) based on an In-Phase / Quadrature-Phase (IQ) value of the input signal. 3. A signal processing device as claimed in claim 2. (Appendix 5) The signal processing device includes: a directional coupler that feeds back the signal amplified by the amplifier to the adjustment unit; Further equipped with The adjustment unit adjusts the calibration signal based on the power of the fed-back calibration signal. 5. The signal processing device according to claim 2, wherein the signal processing device is a device for processing a signal. (Appendix 6) The adjustment unit suppresses a maximum power component of the calibration signal to be equal to or less than a threshold. 6. The signal processing device according to claim 1, (Appendix 7) The adjustment unit adjusts the calibration signal for each channel of the input signal. 7. The signal processing device according to claim 2, wherein the signal processing device is a device for processing a signal. (Appendix 8) The compensation unit performs DPD (Digital Pre-Distortion) to compensate for distortion characteristics and memory effects caused by the amplifier. 8. The signal processing device according to claim 1, (Appendix 9) The compensation unit performs a process of compensating the input calibration signal using a stored LUT (Look Up Table). 9. The signal processing device according to any one of claims 2 to 8. (Appendix 10) The LUT associates an IQ (In-Phase / Quadrature-Phase) value of an input signal with a DPD compensation coefficient corresponding to the IQ value. 10. The signal processing device of claim 9. (Appendix 11) The DPD compensation coefficient is a coefficient for compensating for nonlinear AM-AM / AM-PM (Amplitude Modulation-Phase Modeling), which is a cause of nonlinear distortion of an amplifier. 11. The signal processing device of claim 10. (Appendix 12) the compensation unit selects a DPD compensation coefficient based on the amplitude and phase of the input signal and the calibration signal; 12. The signal processing device according to claim 10 or 11. (Appendix 13) an adjustment means for adjusting one or both of the input signal and the calibration signal so that a difference between a signal power of the input signal and a signal power of a calibration signal for performing calibration between the transmission systems becomes small; a compensation means for performing distortion compensation between the input signal and the calibration signal; an amplifier for amplifying the input signal and the calibration signal; an output means for outputting the input signal adjusted by the adjustment means and the calibration signal to the amplifier; A wireless communication device comprising: (Appendix 14) The wireless communication device performs wireless communication in a TDD (Time Division Duplex) mode. 14. The wireless communication device of claim 13. (Appendix 15) The adjustment means adjusts the signal power of the calibration signal. 15. The wireless communication device according to claim 13 or 14. (Appendix 16) the adjustment means adjusts the calibration signal based on average power values ​​of the input signal and the calibration signal, 16. The wireless communication device according to claim 14 or 15. (Appendix 17) the adjustment means adjusts the signal power of the calibration signal by calculating a frequency bandwidth of the input signal by FFT (Fast Fourier Transform) based on an IQ (In-Phase / Quadrature-Phase) value of the input signal. 17. The wireless communication device according to claim 15 or 16. (Appendix 18) The wireless communication device includes: a directional coupler for feeding back the signal amplified by the amplifier to the adjustment means; Further equipped with The adjustment means adjusts the calibration signal based on the power of the fed-back calibration signal. 18. The wireless communication device according to claim 15, (Appendix 19) The adjustment means suppresses a maximum power component of the calibration signal to be equal to or less than a threshold value. 19. The wireless communication device according to any one of appendixes 13 to 18. (Appendix 20) the adjustment means adjusts the calibration signal for each channel of the input signal. 20. The wireless communication device according to claim 15, wherein the first and second communication interfaces are connected to each other. (Appendix 21) The compensation means performs DPD (Digital Pre-Distortion) to compensate for distortion characteristics and memory effects caused by the amplifier. 21. The wireless communication device according to claim 13. (Appendix 22) The compensation means performs a process of compensating the input calibration signal using a stored LUT (Look Up Table). 22. The wireless communication device according to claim 15, (Appendix 23) The LUT associates an IQ (In-Phase / Quadrature-Phase) value of an input signal with a DPD compensation coefficient corresponding to the IQ value. 23. The wireless communication device of claim 22. (Appendix 24) The DPD compensation coefficient is a coefficient for compensating for nonlinear AM-AM / AM-PM (Amplitude Modulation-Phase Modeling), which is a cause of nonlinear distortion of an amplifier. 24. The wireless communication device of claim 23. (Appendix 25) the compensation means selecting a DPD compensation coefficient based on the amplitude and phase of the input signal and the calibration signal; 25. The wireless communication device according to claim 23 or 24. (Appendix 26) an adjustment step of adjusting one or both of the input signal and the calibration signal so that a difference between a signal power of the input signal and a signal power of a calibration signal for performing calibration between the transmission systems becomes small; a compensation step of performing distortion compensation between the input signal and the calibration signal; an amplifying step of amplifying the input signal and the calibration signal; an output step of outputting the input signal and the calibration signal adjusted by the adjustment step to the amplification step; A signal processing method comprising: (Appendix 27) The adjusting step adjusts a signal power of the calibration signal. 27. A signal processing method as recited in claim 26. (Appendix 28) The adjustment step adjusts the calibration signal based on average power values ​​of the input signal and the calibration signal, 28. A signal processing method as recited in claim 27. (Appendix 29) the adjusting step adjusts the signal power of the calibration signal by calculating a frequency bandwidth of the input signal by a Fast Fourier Transform (FFT) based on an In-Phase / Quadrature-Phase (IQ) value of the input signal; 28. A signal processing method as recited in claim 27. (Appendix 30) The adjusting step includes suppressing a maximum power component of the calibration signal to be equal to or less than a threshold. A signal processing method according to any one of appendixes 26 to 29. (Appendix 31) The adjustment step adjusts the calibration signal for each channel of the input signal. A signal processing method according to any one of claims 27 to 30. (Appendix 32) The compensation step performs DPD (Digital Pre-Distortion) to compensate for distortion characteristics and memory effects caused by the amplification step. A signal processing method according to any one of claims 26 to 31. (Appendix 33) The compensation step performs a process of compensating the input calibration signal using a stored LUT (Look Up Table). A signal processing method according to any one of claims 27 to 32. (Appendix 34) The LUT associates an IQ (In-Phase / Quadrature-Phase) value of an input signal with a DPD compensation coefficient corresponding to the IQ value. 34. A signal processing method as recited in claim 33. (Appendix 35) The DPD compensation coefficient is a coefficient for compensating for nonlinear AM-AM / AM-PM (Amplitude Modulation-Phase Modeling), which causes nonlinear distortion in the amplification step. 35. A signal processing method as recited in claim 34. (Appendix 36) the compensating step selecting DPD compensation coefficients based on amplitudes and phases of the input signal and the calibration signal; 36. A signal processing method according to claim 34 or 35. (Appendix 37) an adjustment process for adjusting one or both of the input signal and the calibration signal so that a difference between a signal power of the input signal and a signal power of a calibration signal for performing calibration between transmission systems becomes small; an output process for outputting the input signal and the calibration signal adjusted in the adjustment process to an amplifier; A program for causing a signal processing device to execute the above. (Appendix 38) The adjustment process includes a process of adjusting a signal power of the calibration signal. 38. The program according to claim 37. (Appendix 39) the adjustment process performs a process of adjusting the calibration signal based on average power values ​​of the input signal and the calibration signal, 39. The program according to claim 38. (Appendix 40) the adjustment process includes performing a process of adjusting the signal power of the calibration signal by calculating a frequency bandwidth of the input signal by FFT (Fast Fourier Transform) based on an IQ (In-Phase / Quadrature-Phase) value of the input signal; 39. The program according to claim 38. (Appendix 41) The adjustment process includes performing a process of suppressing a maximum power component of the calibration signal to be equal to or less than a threshold value. The program according to any one of appendices 37 to 40. (Appendix 42) the adjustment process includes a process of adjusting the calibration signal for each channel of the input signal. The program according to any one of appendices 38 to 41.

[0126] Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

[0127] This application claims priority based on Japanese Patent Application No. 2021-046725, filed on March 22, 2021, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0128] 10, 100 Signal processing device 11 Adjustment part 12 Compensation Department 13 Amplifier 14 Output section 101 DL signal monitor unit 102 CAL-TRX 103 Distortion compensation section 104 Amplifier

Claims

1. an adjustment means for adjusting the calibration signal so that a difference between a signal power of an input signal and a signal power of a calibration signal for performing calibration between transmission systems becomes small; a compensation means for performing distortion compensation between the input signal and the calibration signal; an amplifier for amplifying the input signal and the calibration signal; an output means for outputting the calibration signal adjusted by the adjustment means to the amplifier; A signal processing device comprising:

2. The adjustment means adjusts the signal power of the calibration signal. The signal processing device according to claim 1 .

3. the adjustment means adjusts the calibration signal based on average power values ​​of the input signal and the calibration signal, The signal processing device according to claim 2 .

4. the adjustment means adjusts the signal power of the calibration signal by calculating a frequency bandwidth of the input signal by FFT (Fast Fourier Transform) based on an IQ (In-Phase / Quadrature-Phase) value of the input signal; The signal processing device according to claim 2 .

5. The signal processing device includes: a directional coupler for feeding back the signal amplified by the amplifier to the adjustment means; Further equipped with The adjustment means adjusts the calibration signal based on the power of the fed-back calibration signal. The signal processing device according to any one of claims 2 to 4.

6. The adjustment means suppresses a maximum power component of the calibration signal to be equal to or less than a threshold value. The signal processing device according to any one of claims 1 to 5.

7. the adjustment means adjusts the calibration signal for each channel of the input signal. The signal processing device according to any one of claims 2 to 6.

8. an adjustment means for adjusting the calibration signal so that a difference between a signal power of an input signal and a signal power of a calibration signal for performing calibration between transmission systems becomes small; a compensation means for performing distortion compensation between the input signal and the calibration signal; an amplifier for amplifying the input signal and the calibration signal; an output means for outputting the calibration signal adjusted by the adjustment means to the amplifier; A wireless communication device comprising:

9. an adjustment step of adjusting the calibration signal so that a difference between a signal power of an input signal and a signal power of a calibration signal for performing calibration between transmission systems becomes small; a compensation step of performing distortion compensation between the input signal and the calibration signal; an amplifying step of amplifying the input signal and the calibration signal; an output step of outputting the calibration signal adjusted by the adjustment step to the amplification step; A signal processing method comprising:

10. an adjustment process of adjusting the calibration signal so that a difference between a signal power of an input signal and a signal power of a calibration signal for performing calibration between transmission systems becomes small; an output process of outputting the calibration signal adjusted in the adjustment process to an amplifier; A program for causing a signal processing device to execute the above.

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