Signal processing device, signal processing method and program

Abstract

A signal processing device (100) according to an embodiment of the present invention is provided with: a distortion compensating means (101) for subjecting an input signal to distortion compensation processing to compensate for non-linear distortion, and outputting the signal that has been subjected to the distortion compensation processing; an amplifier (102) for amplifying the signal output by the distortion compensating means (101) and outputting the same as a communication signal; and a signal output means (103) for outputting an adjustment signal for adjusting the distortion compensation processing as an input signal to the distortion compensating means (101), at a timing when the communication signal is not being output, where the adjustment signal has a frequency range covering the frequency range of the communication signal. This makes it possible to provide a signal processing device for suppressing a deterioration in an output signal.

Description

[Technical field]

[0001] The present invention relates to a signal processing apparatus, a signal processing method and a non-transitory computer readable medium. [Background technology]

[0002] Wireless communication technologies such as 5G (5th Generation) are evolving. In this technology field, compensating for distortions present in signals is important to ensure accurate transmission of signal content.

[0003] For example, Patent Document 1 discloses an antenna device equipped with a distortion compensation unit that compensates for distortion caused by multiple amplifiers. A detection unit of the antenna device detects, for example, AM (Amplitude Modulation)-AM distortion or AM-PM (Phase Modulation) distortion as the distortion characteristics of the power amplifier. The distortion compensation unit performs distortion compensation for the multiple amplifiers based on the detection result. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-136772 A Summary of the Invention [Problem to be solved by the invention]

[0005] In wireless communication systems, a DPD (Digital Pre-Distortion) compensator is provided in front of an amplifier to suppress distortion generated by the amplifier and expand the linear range of the amplifier's output signal. However, when a sudden change occurs in the signal input to the amplifier (for example, a change from a narrowband signal to a wideband signal), the DPD compensation may not be able to handle the change. In this case, the output signal from the amplifier deteriorates, and there is a possibility that desired communication characteristics cannot be obtained.

[0006] An object of the present disclosure is to provide a signal processing device, a signal processing method, and a non-transitory computer-readable medium for suppressing degradation of an output signal. [Means for solving the problem]

[0007] A signal processing device according to one aspect of the present embodiment includes a distortion compensation means that performs distortion compensation processing to compensate for nonlinear distortion on an input signal and outputs the signal that has been subjected to the distortion compensation processing, an amplifier that amplifies the signal output by the distortion compensation means and outputs it as a communication signal, and a signal output means that has a frequency band that covers the frequency band of the communication signal at a time when the communication signal is not output, and outputs an adjustment signal for adjusting the distortion compensation processing to the distortion compensation means as the input signal.

[0008] In one aspect of the signal processing method according to the present embodiment, a distortion compensation means performs distortion compensation processing to compensate for nonlinear distortion on an input signal, outputs a signal that has been subjected to the distortion compensation processing, amplifies the signal output by the distortion compensation means and outputs it as a communication signal for communication, and at a timing when the communication signal is not output, an adjustment signal that has a frequency band that covers the frequency band of the communication signal and is used to adjust the distortion compensation processing is output as the input signal to the distortion compensation means.

[0009] A non-transitory computer-readable medium according to one aspect of the present embodiment has stored thereon a program that causes a computer to execute the following steps: a distortion compensation means performs distortion compensation processing to compensate for nonlinear distortion on an input signal, outputs a signal that has been subjected to the distortion compensation processing, amplifies the signal output by the distortion compensation means and outputs it as a communication signal for communication, and at a timing when the communication signal is not output, outputs an adjustment signal that has a frequency band that covers the frequency band of the communication signal and that adjusts the distortion compensation processing to the distortion compensation means as the input signal. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide a signal processing device, a signal processing method, and a non-transitory computer-readable medium for suppressing degradation of an output signal. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram showing an example of a signal processing device according to a first embodiment; [Figure 2A] 5 is a flowchart showing an example of processing by the signal processing device according to the first embodiment. [Figure 2B] 5 is a flowchart showing an example of processing by the signal processing device according to the first embodiment. [Diagram 3] FIG. 11 is a schematic diagram illustrating an example of a wireless communication device according to a second embodiment. [Figure 4] FIG. 11 is a block diagram showing an example of a BB unit according to a second embodiment. [Diagram 5] FIG. 11 is a block diagram showing an example of an FE unit according to a second embodiment. [Figure 6] 11 is a graph showing an example of a power level of a transmitter in a wireless communication device according to a second embodiment. [Figure 7] FIG. 11 is a diagram illustrating an example of a frequency arrangement of DL calibration signals for each transmitter according to the second embodiment. [Figure 8A] 11 is a graph showing an example of each signal according to the second embodiment. [Figure 8B] 13 is a three-dimensional graph showing a detailed example of a CAL signal and an SSB according to the second embodiment. [Figure 8C] 13 is a graph showing a detailed example of a CAL signal and an SSB according to the second embodiment; [Figure 9A] 11 is a graph showing an example of gain in a predetermined frequency band when DPD is off in the second embodiment. [Figure 9B] 13 is a graph showing an example of a DL-CAL signal when DL calibration is performed in a state where DPD is off in the second embodiment. [Figure 9C]11 is a graph showing an example of gain in a predetermined frequency band when DPD is on in the second embodiment. [Figure 9D] 13 is a graph showing an example of a DL-CAL signal when DL calibration is performed with DPD turned on in the second embodiment. [Figure 10A] 13 is a three-dimensional graph showing a detailed example of a DPD training signal and an SSB according to the second embodiment. [Figure 10B] 11 is a graph showing a detailed example of a DPD training signal and an SSB according to the second embodiment; [Figure 11] 11 is a graph showing an example of timing at which a DPD training signal according to the second embodiment is output; [Figure 12] 11 is a flowchart illustrating an example of a process performed by the wireless communication device according to the second embodiment. [Figure 13] 13 is a graph showing an example of a transmission power pattern according to the third embodiment; [Figure 14] FIG. 2 is a block diagram showing an example of a hardware configuration of an apparatus according to each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] First embodiment Hereinafter, a first embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a block diagram showing a signal processing device according to the first embodiment. The signal processing device 100 is a device for processing an electric signal, and can be applied to, for example, a wireless communication device in a communication system, but is not limited thereto.

[0013] The signal processing device 100 includes a distortion compensating unit 101, an amplifier 102, and a signal output unit 103. Each of the components will be described below.

[0014] The distortion compensation unit 101 measures nonlinear distortion of the input signal IN, performs distortion compensation processing to compensate for the measured nonlinear distortion, and outputs the signal that has been subjected to the distortion compensation processing to the corresponding amplifier 102. By this distortion compensation processing, the nonlinear distortion of the signal output by the amplifier 102 is suppressed.

[0015] The distortion compensation unit 101 performs, for example, DPD compensation processing as the distortion compensation processing. When the DPD compensation processing is performed, DPD compensation coefficients related to amplitude and phase are stored inside the distortion compensation unit 101. The DPD compensation coefficients are weights for compensating for nonlinear AM / PM components of the amplifier 102, and the distortion compensation unit 101 selects appropriate DPD compensation coefficients related to amplitude and phase based on the characteristics of the input signal IN. The distortion compensation unit 101 performs DPD compensation processing on the input signal IN using the selected DPD compensation coefficient. For example, the distortion compensation unit 101 stores an LUT (lookup table) in which the amplitude or (I, Q) value of the input signal IN is associated with the DPD compensation coefficient corresponding to the value. The distortion compensation unit 101 determines the value of the input signal IN, and selects an appropriate DPD compensation coefficient by referring to the LUT based on the value, and performs DPD compensation processing. The distortion compensation unit 101 appropriately updates the DPD compensation coefficients related to amplitude and phase using feedback FB of the output of the amplifier 102.

[0016] The amplifier 102 is an amplifier that amplifies the signal output from the distortion compensation unit 101 and outputs it as an output signal OUT. The amplifier 102 can output a communication signal used for wireless or wired communication as the output signal OUT. The communication signal may be, for example, a transmission signal transmitted from the signal processing device 100 to another device, or a reception signal received by the signal processing device 100 from another device. Note that any type of amplifier can be used as the amplifier 102.

[0017] The signal output unit 103 has a frequency band that covers the frequency band of the communication signal, and outputs an adjustment signal for adjusting the distortion compensation process to the distortion compensation unit 101 as an input signal IN at a timing when the communication signal is not output from the amplifier 102. The "frequency band that covers the frequency band of the communication signal" means that, when the frequency band of the communication signal is from frequency F1 to F2 (F1>F2) and the frequency band of the adjustment signal is from frequency F3 to F4 (F3>F4), F3 is equal to or greater than F1 and F4 is equal to or less than F2. The adjustment signal is, for example, a dense signal in which there is no blank frequency band such as a guard band in the frequency band of the signal. Specifically, the adjustment signal may be a signal in which a large number of narrowband subcarriers are multiplexed and transmitted on the frequency axis by modulation using OFDM (Orthogonal Frequency Division Multiplexing). Specifically, a desired adjustment signal can be generated by allocating transmission data to all subcarriers within the band of the signal and executing IFFT (Inverse Fast Fourier Transform) processing. The adjustment signal may be a signal that is spread over the entire frequency band by modulation using spread spectrum. The spread spectrum method is a method used in CDMA (Code Division Multiple Access) systems, such as direct sequence spread spectrum. In the spread spectrum method, a scramble code is applied to the transmission data to increase the data rate, thereby obtaining a wideband signal. However, the adjustment signal is not limited to the above method and can be generated by any method.

[0018] In addition, when the communication signal is a transmission signal transmitted from the signal processing device 100 to another device, the signal output unit 103 may generate the communication signal at a timing different from that for generating the adjustment signal, and output the communication signal to the distortion compensation unit 101.

[0019] FIG. 2A is a flowchart showing a process executed by the signal processing device 100 when a communication signal is input to the amplifier 102. As shown in FIG.

[0020] First, the distortion compensation unit 101 performs distortion compensation processing on the input communication signal, and outputs the signal that has been subjected to distortion compensation processing (step S11). The amplifier 102 amplifies and outputs the communication signal output by the distortion compensation unit 101 (step S12). The distortion compensation unit 101 adjusts the distortion compensation processing using feedback FB of the output signal (step S13). Here, the distortion compensation unit 101 updates the DPD compensation coefficient. By performing distortion compensation processing in this manner, the SINR of the communication signal can be improved.

[0021] 2B is a flowchart showing a process executed by the signal processing device 100 when an adjustment signal is input to the amplifier 102 as an input signal at a timing when a communication signal is not output. First, the signal output unit 103 outputs the adjustment signal to the amplifier 102 as an input signal IN (step S14). The distortion compensation unit 101 performs distortion compensation processing on the adjustment signal and outputs the adjustment signal that has been subjected to distortion compensation processing (step S15). The amplifier 102 amplifies and outputs the adjustment signal output by the distortion compensation unit 101 (step S16). The distortion compensation unit 101 adjusts the distortion compensation processing using feedback of the output signal (step S17).

[0022] As described above, the signal output unit 103 of the signal processing device 100 outputs an adjustment signal, the frequency band of which includes the frequency band of the communication signal, as the input signal IN to the distortion compensation unit 101 at a timing when the communication signal is not output from the amplifier 102. In order to adjust the distortion compensation process using the adjustment signal output by the amplifier 102, the distortion compensation unit 101 sets the distortion compensation so that the gain does not drop in the frequency band of the adjustment signal. For example, when the distortion compensation unit 101 executes the DPD compensation process, the distortion compensation unit 101 updates the DPD compensation coefficient to one suitable for the adjustment signal by using feedback of the output signal of the amplifier 102. With this update, even when the signal processing device 100 outputs the communication signal after outputting the adjustment signal, it is possible to suppress the deterioration of the gain of the communication signal by the distortion compensation unit 101.

[0023] As an example, the adjustment signal may be a signal modulated by OFDM or spectrum spread. This allows the signal processing device 100 to relatively easily generate an adjustment signal that can suppress deterioration of the gain of the communication signal regardless of where the frequency component of the communication signal is located on the frequency band of the adjustment signal by using a known technique.

[0024] Note that the signal processing device 100 may be provided with a plurality of amplifiers 102. That is, the signal processing device 100 may have a plurality of signal channels. In this case, the distortion compensation unit 101 may be provided for each signal channel. Alternatively, there may be a signal channel that is provided with an amplifier 102 but not provided with a distortion compensation unit 101. Furthermore, one unit of the distortion compensation unit 101 may perform distortion compensation processing on a plurality of signal channels and output the signals that have been subjected to the distortion compensation processing to a plurality of amplifiers 102.

[0025] Embodiment 2 Hereinafter, a second embodiment of the present disclosure will be described with reference to the drawings. In the second embodiment, the signal processing shown in the first embodiment will be described with a detailed concrete example.

[0026] Hereinafter, an embodiment of a wireless communication device will be described in which TDD (Time Division Duplex) is used as a communication method and MIMO (Multi User-Multi Input Multi Output) is used for wireless transmission and reception. In addition, in order to achieve high frequency utilization efficiency, this wireless communication device uses digital beamforming technology.

[0027] FIG. 3 is a block diagram showing an example of a wireless communication device 10 according to the second embodiment. The wireless communication device 10 is a specific application example of the signal processing device 100, and is equipped with a massive element AAS (Active Antenna System) for 5G, and is a device provided in, for example, a base station. As shown in FIG. 3, the wireless communication device 10 includes a BF-BB (Beamforming-Baseband) unit 20 and an AAS unit 30. Here, the AAS unit 30 includes an optical transceiver 31, a TRX-BB unit 32, a front-end unit 33, 32 antennas 34 (wireless transmission units), a distributor / synthesizer 35, a SW (Switch) 36, and a CAL-TRX (calibration transceiver) 37, and a control unit (not shown) that controls each of these units. Note that, in the following, an uplink (UL) refers to a communication path from a UE (User Equipment) (not shown) to the wireless communication device 10, and a downlink (DL) refers to a communication path from the wireless communication device 10 to the UE.

[0028] The BF-BB unit 20 is a baseband unit having a function of generating a beamforming signal. The BF-BB unit 20 stores a preset receiving system characteristic [CAL-RX (fixed)] inside. The BF-BB unit 20 also stores the characteristic TX#n*[CAL-RX] of each signal channel acquired by the operation of the TRX-BB unit 32 when the wireless communication device 10 is started and periodically, and updates it every time a new value is acquired. The BF-BB unit 20 uses these values ​​to output a communication signal for communication to the AAS unit 30, thereby performing communication in the DL direction. Details of this process will be described later.

[0029] Furthermore, the BF-BB unit 20 executes a DL or UL calibration operation when the wireless communication device 10 is started and periodically to determine and store a calibration weight (hereinafter, referred to as a CAL weight) for DL ​​or UL. 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. For example, DL calibration is performed to accurately generate the angle and depth of a null point formed in wireless signal radiation before the wireless communication device 10 transmits a wireless signal by data beamforming.

[0030] When performing DL calibration, the BF-BB unit 20 generates a DL calibration signal (hereinafter referred to as DL-CAL signal), which is an IQ signal, and outputs it to the CAL-TRX 37 via the optical transceiver 31, the TRX-BB unit 32, the front-end unit 33, the distributor / synthesizer 35, and the SW 36. The CAL-TRX 37 converts the input RF signal into an IQ signal, and outputs the DL-CAL signal to the BF-BB unit 20. The BF-BB unit 20 determines the DL-CAL weight to be applied to each signal channel by measuring the difference in amplitude and phase between the original DL-CAL signal and the DL-CAL signal output by the CAL-TRX 37.

[0031] When the BF-BB unit 20 executes UL calibration, it generates an IQ signal, which is a UL calibration signal (hereinafter, referred to as a UL-CAL signal), and transmits it directly to the CAL-TRX 37. The CAL-TRX 37 converts the IQ signal into an RF signal, and outputs the UL-CAL signal to the BF-BB unit 20 via the SW 36, the distributor / synthesizer 35, the front-end unit 33, the TRX-BB unit 32, and the optical transceiver 31. The BF-BB unit 20 determines the UL-CAL weight to be applied to each signal channel by measuring the difference in amplitude and phase between the original UL-CAL signal and the UL-CAL signal transmitted by the CAL-TRX 37. In this way, the BF-BB unit 20 functions as a baseband having a function of generating a beamforming signal. In addition, in Figs. 3 and 4, the DL / UL-CAL signal, which is an IQ signal transmitted and received between the BF-BB unit 20 and the CAL-TRX 37, is indicated as DL / UL-CAL IQ.

[0032] Next, a description will be given of each component of the AAS unit 30. The optical transceiver 31 performs photoelectric conversion of signals (eg, multi-layer signals) transmitted and received between the BF-BB unit 20 and the TRX-BB unit 32, and the reverse conversion.

[0033] The TRX-BB unit 32 is a transceiver baseband unit that mediates communication signals transmitted and received between the optical transceiver 31 and the front-end unit 33, and includes 32 BB units 40#0-#31. Hereinafter, the BB units 40#0-#31 will be collectively referred to as BB unit 40.

[0034] 4 is a block diagram of the BB unit 40. The BB unit 40 includes a CFR processing unit 41 and a DPD processing unit 42. Each of the BB units 40#0 to #31 has the same configuration as that shown in FIG.

[0035] The CFR processing unit 41 suppresses the peak level of the IQ signal (multi-layer signal) output from the BF-BB unit 20 and input via the optical transceiver 31 to a CFR threshold, and outputs the signal to the DPD processing unit 42. The CFR threshold is a threshold for suppressing the maximum peak component. Specifically, when the amplitude of the input multi-layer signal exceeds the CFR threshold, the CFR processing unit 41 suppresses the amplitude of the multi-layer signal to the CFR threshold, and outputs the signal to the DPD processing unit 42.

[0036] The DPD processing unit 42 corresponds to the distortion compensation unit 101 according to the first embodiment, and is provided between each CFR processing unit 41 and each TRX 51. The DPD processing unit 42 compensates for nonlinear distortion in the input / output characteristics of AM-AM and AM-PM generated in the transmitting amplifier 52, using the IQ signal (multi-layer signal) output from the CFR processing unit 41 and the IR signal (multi-layer signal) output from the transmitting amplifier 52 (transmitting power amplifier) ​​via the directional coupler 53 and the FB path. The IR signal is represented as a signal FB in Figs. 4 and 5.

[0037] The DPD processor 42 performs DPD compensation processing to compensate the amplitude and phase of the IQ signal for wireless communication output from the CFR processor 41 based on a DPD compensation coefficient that represents the inverse characteristics of the input / output characteristics of the downstream transmitting amplifier 52, and outputs the signal that has been subjected to the DPD compensation processing as a signal TR to the FE unit 50. By providing a DPD processor 42 for each TRX 51, it is possible to execute DPD compensation processing based on the characteristics of each TRX 51. This DPD compensation processing is performed to improve the DL SINR (Signal to Interference plus Noise Ratio) performance. Furthermore, the DPD compensation processing can also improve the EVM (Error Vector Magnitude) and ACLR (Adjacent Channel Leakage Ratio) of the transmitting amplifier 52.

[0038] The received signal RE output from the antenna 34 is output to the optical transceiver 31 via the FE unit 50.

[0039] Furthermore, the TRX-BB unit 32 outputs a DPD training signal via each DPD processing unit 42 at a timing other than the DL / UL calibration operation, thereby causing each DPD processing unit 42 to adjust the DPD compensation setting. Therefore, the TRX-BB unit 32 corresponds to the signal output unit 103 according to the first embodiment. Details of this processing will be described later.

[0040] Returning to Fig. 3, the description of the AAS section 30 will continue. The front-end section 33 includes 32 FE units 50#0-#31. The FE units 50#0-#31 will be collectively referred to as FE unit 50 below.

[0041] Fig. 5 is a block diagram of the FE unit 50. The FE unit 50 includes a TRX 51, a transmission amplifier (transmission power amplifier) ​​52, a directional coupler (COUPLER) 53, a SW 54, and a reception amplifier (reception power amplifier) ​​55. Each of the FE units 50#0 to #31 has the same configuration as that shown in Fig. 5.

[0042] The TRX 51 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 32 into an RF signal, and outputs the RF signal to the antenna 34 or the CAL-TRX 37. When the wireless communication device 10 transmits a wireless signal, the transmitter TX outputs the RF signal to the antenna 34, and when performing DL calibration, the transmitter TX outputs the RF signal to the CAL-TRX 37 via the distributor / synthesizer 35.

[0043] Furthermore, the receiver RX converts an RF signal received from the antenna 34 or the CAL-TRX 37 into an IQ signal and outputs it to the TRX-BB unit 32. When the wireless communication device 10 receives a wireless signal from the UE, the TRX 51 receives the RF signal from the antenna 34. When UL calibration is performed, the TRX 51 receives a UL-CAL signal (RF signal) from the CAL-TRX 37 via the distributor / synthesizer 35. Then, the TRX 51 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 20 via the TRX-BB unit 32.

[0044] Furthermore, the TRX 51 has an FB path that converts the RF signal FB output from the directional coupler 53 into an IQ signal and outputs the IQ signal to the DPD processing unit 42 described above.

[0045] Each transmitting amplifier 52 corresponds to the amplifier 102 according to the first embodiment, and is disposed between each antenna 34 and a TRX 51 provided corresponding to each antenna 34. The transmitting amplifier 52 amplifies an RF signal (a signal for wireless communication or a DL-CAL signal) output from the TRX 51, and outputs the amplified signal to the directional coupler 53.

[0046] Each directional coupler 53 is a coupler provided between each transmitting amplifier 52 and each antenna 34. The directional coupler 53 outputs the RF signal output from each transmitting amplifier 52 to the antenna 34 and also to the corresponding TRX 51. The TRX 51 outputs the output RF signal to the DPD processing unit 42 via the FB path. The DPD processing unit 42 receives the IQ signal output from the FB path and compensates for nonlinear distortion in the input / output characteristics of AM-AM and AM-PM generated in the transmitting amplifier 52 as described above.

[0047] The SW54 is a switch that switches a signal to be input or output to the TRX51 based on a control signal from the control unit of the AAS unit 30. That is, under the control of the AAS unit 30, the connection destination of the front-end unit 33 is switched.

[0048] Specifically, when the wireless communication device 10 is performing wireless communication, in each of the signal channels #0 to #31, the front-end unit 33 is connected to the antenna 34, and the SW54 is controlled so as not to connect the front-end unit 33 to the CAL-TRX 37. As a result, during data transmission, an RF signal is output from the TRX51 to the antenna 34, while during data reception, the SW54 causes the TRX51 to output an RF signal from the antenna 34.

[0049] On the other hand, when the wireless communication device 10 performs DL / UL calibration, the SW54 is controlled so that, in each of the signal channels #0 to #31, the front-end unit 33 and the CAL-TRX37 are connected and the front-end unit 33 and the antenna 34 are not connected. In other words, the TRX51 and the distributor / synthesizer 35 are connected, while the connection between the antenna 34 and the TRX51 is released. When the wireless communication device 10 performs DL calibration, the DL-CAL signal output from the transmitting amplifier 52 is output to the distributor / synthesizer 35. When the wireless communication device 10 performs UL calibration, the UL-CAL signal output from the distributor / synthesizer 35 is output to the receiving amplifier 55.

[0050] The wireless communication device 10 prevents the DL / UL-CAL signal processed by each TRX 51 from being affected by interference from other systems by controlling each SW 54. That is, since the DL / UL-CAL signal processed by each TRX 51 does not contain an interference component, the AAS unit 30 can accurately determine the CAL weight to be applied to each TRX 51. Furthermore, when the DL / UL calibration is completed, the control unit of the AAS unit 30 controls each SW 54 so that each TRX 51 and each antenna 34 are connected.

[0051] Each receiving amplifier 55 is disposed between each antenna 34 and a TRX 51 provided corresponding to each antenna 34. The transmitting amplifier 52 amplifies a received RF signal (a signal for wireless communication or a UL-CAL signal) and outputs the amplified signal to the corresponding TRX 51.

[0052] Returning to Fig. 3, the description of the AAS unit 30 will be continued. The antennas 34 are provided corresponding to each TRX 51, each transmitting amplifier 52, and each receiving amplifier 55. The antennas 34 are polarization diversity antennas having mutually orthogonal polarizations of +45 degrees and -45 degrees, and four antennas each having eight sets are provided, that is, a total of 32 antennas are provided. Each antenna 34 transmits the RF signal received from each FE unit 50 to one or more UEs by wireless. At least one of a filter and a duplexer may be provided in front of each antenna 34 as appropriate.

[0053] When wireless communication device 10 performs DL calibration, distributor / synthesizer 35 combines the DL-CAL signals output from each SW 54, and outputs the combined DL-CAL signal to SW 36. When wireless communication device 10 performs UL calibration, distributor / synthesizer 35 distributes the UL-CAL signal output from SW 36, and outputs the distributed UL-CAL signal to each SW 54.

[0054] SW36 is a switch for switching the signal direction. When wireless communication device 10 executes DL calibration, SW36 outputs the DL-CAL signal output from distributor / synthesizer 35 to SW36. When wireless communication device 10 executes UL calibration, SW36 outputs the UL-CAL signal output from SW36 to distributor / synthesizer 35.

[0055] When the wireless communication device 10 executes DL calibration, the CAL-TRX 37 converts the DL-CAL signal (RF signal) output from the SW 36 into a DL-CAL signal (IQ signal). Then, the CAL-TRX 37 outputs the converted DL-CAL signal to the BF-BB unit 20.

[0056] Also, when the wireless communication device 10 performs UL calibration, CAL-TRX37 converts the UL-CAL signal (IQ signal) output from the BF-BB unit 20 into a UL-CAL signal (RF signal), and outputs the converted UL-CAL signal to SW36. Note that CAL-TRX37 may be equipped with a transmitter and a receiver, similar to TRX51.

[0057] Hereinafter, the DL calibration operation and UL calibration operation of the wireless communication device 10 will be described.

[0058] First, the DL calibration operation will be described. First, the BF-BB unit 20 outputs a preset DL-CAL signal (IQ signal) to the front-end unit 33 via the optical transceiver 31 and the TRX-BB unit 32. Each TRX51 (transmitter TX) in the front-end unit 33 converts the DL-CAL signal (IQ signal) into a DL-CAL signal (RF signal). The DL-CAL signals (RF signals) converted by each TRX51 are output to the distribution combiner 35 via the transmission amplifier 52 and SW54, and are combined by the distribution combiner 35. The DL-CAL signal combined by the distribution combiner 35 is output to CAL-TRX37 via SW36. Note that the AAS unit 30 may output the DL-CAL signal with timing separated for each signal channel.

[0059] CAL-TRX37 converts the received DL-CAL signal (RF signal) into a DL-CAL signal (IQ signal) and outputs it to the BF-BB unit 20. The DL-CAL signal sent from CAL-TRX37 is in a state where the DL-CAL signals sent from each TRX51#n are combined by frequency multiplexing. Therefore, the BF-BB unit 20 frequency-separates the DL-CAL signal sent from CAL-TRX37 by FFT (Fast Fourier Transform), extracts the DL-CAL signal for each of the signal channels #0 to #31, and calculates the DL-CAL weight.

[0060] Specifically, the BF-BB unit 20 learns the variations in the amplitude and phase of the DL-CAL signal for each signal channel by measuring the difference in amplitude and phase between the DL-CAL signal transmitted for each signal channel and the original (i.e., before transmission) DL-CAL signal. The BF-BB unit 20 calculates the DL-CAL weight of each TRX 51#n based on the learning result.

[0061] Here, the DL-CAL weight of each TRX51#n is the product of the transmission system characteristics (amplitude and phase characteristics) [TX#n] of TRX51#n and the reception system characteristics (amplitude and phase characteristics) [CAL-RX] of CAL-TRX37, as expressed in the following equation 1.

number

[0062] This completes the DL calibration operation. The BF-BB unit 20 stores this DL-CAL weight internally. Thereafter, during normal DL wireless communication, the BF-BB unit 20 outputs to each TRX 51 a DL signal weighted by the above-mentioned DL-CAL weight for that TRX 51.

[0063] Next, a description will be given of an example of DL operation of the BF-BB unit 20. The BF-BB unit 20 generates a BF signal (IQ signal) in an internal circuit. Then, the generated BF signal is corrected with the above-mentioned DL-CAL weight for each of the signal channels #0 to #31, and then output to the TRX-BB unit 32 via the optical transceiver 31.

[0064] Specifically, the BF-BB unit 20 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 37. The corrected BF signal is expressed by the following formula 2. Note that [CAL-RX (fixed)] is stored in advance in a storage unit (not shown) of the BF-BB unit 20.

number

[0065] The corrected BF signal is converted from an IQ signal to an RF signal by each TRX 51#n of the TRX-BB unit 32 and sent out, amplified by each transmission amplifier 52#n, and output from the front-end unit 33. The BF signal output from the front-end unit 33 passes through each TRX 51#n, and is therefore expressed by the following Equation 3.

number

[0066] Furthermore, when Equation 3 is simplified by deleting [TX#n], it can be expressed as Equation 4 below.

number

[0067] In formula 4, 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 34#n. Note that, in order for [CAL-RX(fixed)]=[CAL-RX], the stability of CAL-RX is important.

[0068] By performing the above operations, it is possible to compensate for the variations in amplitude and phase characteristics of each transmitter TX#n. This DL calibration operation makes it possible to accurately determine the angle and depth of the null point formed in the radio signal radiation before transmitting the radio signal by data beamforming. In addition, it is possible to suppress the occurrence of nonlinear distortion radiation caused by third-order intermodulation distortion in each spatial direction.

[0069] Note that, as described below, the update of the DL-CAL weight may be performed between the transmission of the wireless signal by fan beamforming and the transmission of the wireless signal by data beamforming. Alternatively, the update of the DL-CAL weight may be performed periodically. As yet another example, the wireless communication device 10 may update the DL-CAL weight triggered by the sensor of the wireless communication device 10 detecting an environmental change (e.g., temperature change) or a change in the signal over time. The update period in this case is, for example, a period of 1 minute or more.

[0070] Next, the UL calibration operation will be described. The BF-BB unit 20 outputs a preset UL-CAL signal (IQ signal) directly to the CAL-TRX 37. The CAL-TRX 37 converts the UL-CAL signal (IQ signal) into a UL-CAL signal (RF signal). The UL-CAL signal (RF signal) converted by the CAL-TRX 37 is output to the distribution combiner 35 via the SW 36 and is distributed by the distribution combiner 35. The UL-CAL signal distributed by the distribution combiner 35 is output to each TRX 51 via each SW 54 and the receiving amplifier 55. Each TRX 51 converts the UL-CAL signal (RF signal) into a UL-CAL signal (IQ signal) and outputs it to the BF-BB unit 20 via the TRX-BB unit 32 and the optical transceiver 31.

[0071] The BF-BB unit 20 measures the difference in amplitude and phase between the UL-CAL signal of the UL-CAL signal received by each TRX 51 and the original UL-CAL signal, and learns the variation in amplitude and phase of the UL-CAL signal. The BF-BB unit 20 calculates the UL-CAL weight of each TRX 51 based on the learning result.

[0072] The UL calibration operation ends here. The BF-BB unit 20 stores this UL-CAL weight internally. Thereafter, during normal UL-related wireless communication, the BF-BB unit 20 will output a UL signal weighted with the above-described UL-CAL weight for each TRX 51 to each TRX 51.

[0073] <Calibration execution timing> Next, the timing of DL and UL calibration will be described. As described above, the wireless communication device 10 is a wireless communication device compatible with the TDD mode (TDD communication method). The TDD mode is a communication method in which the same frequency is used in uplink and downlink (UL / DL) and DL communication and DL communication and UL communication are switched over time for transmission and reception. DL slots are transmitted for DL ​​communication, and UL slots are transmitted for UL communication. Furthermore, at the timing of switching from DL communication to UL communication, flexible slots are transmitted. A flexible slot is a slot consisting of a DL symbol, a UL symbol, and a flexible symbol. The DL symbol is a field reserved for DL ​​communication, the UL symbol is a field reserved for UL communication, and the flexible symbol is a field in which either DL communication or UL communication may be performed.

[0074] The wireless communication device 10 performs either DL calibration or UL calibration, for example, in a transition period when switching from DL to UL in a Flexible Symbol or in a transition period when switching from a UL slot to a DL slot.

[0075] <Transmitter power level when performing calibration> FIG. 6 shows the power levels of the transmitter TX at each of the DL and UL timings. The horizontal axis of FIG. 6 represents time, and the vertical axis represents the power level. The solid line L1 in FIG. 6 shows the transition of the transmission power level of the transmitter TX of the wireless communication device 10. From FIG. 6, it can be seen that the transmission power level, which was the off-power level in the initial transmitter-off period, becomes the on-power level in the transmitter-on period through the transmitter-transition period, and becomes the off-power level in the transmitter-off period again through the transmitter-transition period. Note that in FIG. 6, the time period described as UL transmission indicates the time period of UL communication. Also, the time period described as DL transmission indicates the time period of DL communication. Also, the time period described as UL transmission indicates the time period of UL communication.

[0076] The wireless communication device 10 executes DL calibration or UL calibration in the DL / UL switching period (transmitter transition period). This time period is included within the period of the uplink-downlink frame timing. The time periods (a) when the transmitter TX transitions from OFF to ON and (b) when it transitions from ON to OFF are, for example, 10 μs. The wireless communication device 10 can execute the above-described DL calibration or UL calibration in at least one of the periods (a) and (b). That is, in this example, the output time of the DL / UL-CAL signal may be within 10 μs. Also, the power of the DL / UL-CAL signal may be below the maximum rating. In this way, the DL-CAL weight is periodically calculated and stored inside the BF-BB unit 20.

[0077] <Regarding the Frequency Arrangement of the DL-CAL Signal> Furthermore, an example of the frequency arrangement of the DL-CAL signal with frequency orthogonality for each TRX#n will be described. Here, 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.

[0078] An example of a frequency arrangement of DL-CAL signals for each transmitter TX#n will be described with reference to Fig. 7. Fig. 5 illustrates an example of a frequency arrangement of DL-CAL signals for each transmitter TX#n.

[0079] 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 by Y [MHz] in the frequency direction. Note that fs0 [MHz] is the reference frequency.

[0080] Here, in the example shown in FIG. 7, the following two frequency allocation conditions A1 and A2 need to be satisfied. Frequency allocation condition A1: The relationship X [MHz]>Y [MHz] × (number of transmitters TX#n-1) is true. Frequency allocation condition A2: The signal bandwidth range includes the frequency of the lowest subcarrier sc0 of the DL-CAL signal for transmitter TX#1, “sc0=fs0 [MHz]”, to the frequency of the highest subcarrier sck of the DL-CAL signal for transmitter TX#31, “sck=fsc0+31Y+kX [MHz]”.

[0081] Next, a specific problem related to the second embodiment will be described. Fig. 8A is a graph showing an example of each signal output in the wireless communication device 10. The horizontal axis (X axis) of Fig. 8A indicates time, and the vertical axis (Y axis) indicates frequency, and the graph in Fig. 8A shows signals output by the front-end unit 33. In Fig. 8A, the wireless communication device 10 does not perform individual data communication with the UE, and the wireless communication device 10 periodically outputs a synchronization signal block (SSB) and a reference signal (RS). In addition, at the initial time when an enable signal that causes the transmitter TX of the TRX51 to transition from off to on is output, the wireless communication device 10 outputs a DL-CAL signal.

[0082] In this example, the frequency band of the DL-CAL signal is 100 MHz, and the output time of the signal is 8 μs. On the other hand, the frequency band of the SSB is 7.2 MHz, the output time is 140 μs, and the frequency band of the RS is 23.04 MHz, and the output time is 35.7 μs. The output time of the DL-CAL signal is much shorter than that of the SSB, but the frequency band of the DL-CAL signal is much larger than that of the SSB. Therefore, it can be said that the DL-CAL signal is a wideband signal, and the SSB is a narrowband signal. Note that the output time of the DL-CAL signal is less than 10 μs, which is the transition time of the transmitter TX, as mentioned above.

[0083] Figure 8B is a three-dimensional graph showing details of the DL-CAL signal and SSB shown in Figure 8A. The XY axes in Figure 8B indicate time and frequency, as in Figure 8A. The Z axis in Figure 8B indicates the power of each signal.

[0084] As shown in Figure 8B, the DL-CAL signal is composed of a total of 10 subcarriers in a frequency band of 100 MHz. The frequency band and power of each subcarrier are almost the same. In addition, the peak level power of the DL-CAL signal is lower than the peak level power of the SSB.

[0085] Figure 8C shows the relationship between frequency and power excerpted from the graph shown in Figure 8B as a two-dimensional graph. The horizontal axis (X axis) of Figure 8C shows frequency, and the vertical axis (Y axis) shows power. As shown in Figure 8C, the frequency band of each subcarrier of the DL-CAL signal is smaller than the frequency band of the SSB.

[0086] When the DL-CAL signal is one of the signals described above, the following problems may occur when the wireless communication device 10 transmits the wireless signal.

[0087] 9A to 9D are graphs showing an example of a DL-CAL signal output from the front-end unit 33 when the wireless communication device 10 executes DL calibration with DPD compensation turned off or on. In this example, how the DL-CAL signal is output after the SSB is output from the front-end unit 33 is shown.

[0088] Fig. 9A is a graph showing a case where the AAS unit 30 generates and outputs an SSB when the DPD processing unit 42 does not execute DPD compensation processing. Fig. 9A shows a state where the output level of the transmitter gain set by the AAS unit 30 is constant regardless of the frequency when the DPD compensation processing is not executed (when DPD is off).

[0089] FIG. 9B is a graph showing a case where the AAS unit 30 generates and outputs a DL-CAL signal after FIG. 9A (i.e., after the AAS unit 30 generates and outputs an SSB). The DL-CAL signal is output based on the frequency characteristic of the transmitter gain, which is constant regardless of the frequency, shown in FIG. 9A, and the output level of the original DL-CAL signal itself (e.g., OFDM output level). As described above, since the gain and output level are flat (constant) regardless of the frequency band, the power of the 10 subcarriers of the DL-CAL signal output by the DPD processing unit 42 is approximately the same. Then, only the amplitude level error between each transmitter is corrected by learning using the DL-CAL signal. Therefore, the DL calibration in the wireless communication device 10 is performed without any problem, and the above-mentioned DL-CAL weight is accurately calculated.

[0090] FIG. 9C is a graph showing a case where the AAS unit 30 generates and outputs an SSB in a state where the DPD processing unit 42 executes DPD compensation processing. In the situation in FIG. 9C, unlike FIG. 9A, the DPD correction performed by the AAS unit 30 targets a signal region in which the spectrum exists only in a part of the frequency band. In other words, the range of the frequency band in which nonlinear distortion compensation is performed is narrowed. Then, the frequency characteristic of the transmitter gain is temporarily set to a gain frequency characteristic that is band-limited by a BPF (Band Pass Filter) with the SSB frequency as its band. In addition, when a wideband signal, which is a signal different from the SSB, passes through the AAS unit 30 in the next DL slot, the frequency characteristic of the transmitter gain changes in the DPD update processing as if the BPF band had changed. For the above reasons, as shown in FIG. 9C, the frequency characteristic in the 100 MHz band is not constant and may appear filtered. 9C, the transmitter gain has a frequency characteristic in which the gain is unduly weighted so as to drop at a certain frequency Fth in the 100 MHz frequency band in which the DL-CAL signal is output, and as a result, the output level of the DL-CAL signal output by the AAS unit 30 is also unduly weighted.

[0091] FIG. 9D is a graph showing a case where the AAS unit 30 generates and outputs a DL-CAL signal after generating and outputting an SSB in the state shown in FIG. 9C. Normally, the DPD processing unit 42 changes its own compensation coefficient according to the input signal. However, as described above, the output time of the DL-CAL signal is very short at 8 μs. Therefore, the DPD processing unit 42 is unable to change its own compensation coefficient according to the DL-CAL signal in time, and outputs the DL-CAL signal based on the set gain set in FIG. 9C. As a result, the gain of the 10 subcarriers of the DL-CAL signal drops at the frequency Fth as shown in FIG. 9D. Therefore, the DL calibration in the wireless communication device 10 is performed using a signal different from the original DL-CAL signal, and the DL-CAL weight is not calculated accurately.

[0092] The same phenomenon may occur not only in the DL-CAL signal but also in a wideband signal related to data communication. This phenomenon continues until the next time the DPD processor 42 changes its own compensation coefficient. In addition, the EVM and ACLR of the transmission amplifier 52 also deteriorate.

[0093] In the second embodiment, even in the case where DL calibration is expected to be performed after the wireless communication device 10 transmits an SSB as a wireless signal, the DL calibration can be accurately performed by the following process.

[0094] Figure 10A is a three-dimensional graph showing a detailed example of a DPD training signal and an SSB, where the X-axis, Y-axis and Z-axis represent time, frequency and signal power, respectively.

[0095] The DPD training signal is a wideband, high-density signal that is generated by the TRX-BB unit 32 using OFDM modulation, passes through the DPD processing unit 42, and is output to the transmission amplifier 52. The DPD training signal has a frequency band of 100 MHz, and within that frequency band, a large number of subcarriers are orthogonally multiplexed on the frequency axis. Here, the frequency band and power occupied by each subcarrier are approximately the same. As described below, the output time of the DPD training signal may be equal to or less than the time it takes for the transmitter TX to transition from OFF to ON or from ON to OFF. In this example, the output time is 8 μs. The power of the DPD training signal may be equal to or less than the maximum rating.

[0096] Figure 10B is a two-dimensional graph showing the relationship between frequency and power extracted from the graph shown in Figure 10A. The horizontal axis (X axis) of Figure 10B shows frequency, and the vertical axis (Y axis) shows power. As shown in Figure 10B, the peak level power of the DPD training signal is higher than the peak level power of the SSB (communication signal). However, the peak level power of the DPD training signal is lower than the peak level power during maximum rated transmission.

[0097] Fig. 11 is a graph showing an example of the timing at which a DPD training signal is output. The horizontal axis in Fig. 11 represents time. The upper part of Fig. 11 shows the output signal output in the DL direction from the front-end unit 33, the middle part shows the DPD signal capture window in the DPD processing unit 42, and the lower part shows the TX enable signal of the transmitter TX in the TRX 51.

[0098] The DPD signal capture window indicates a section during which the DPD processor 42 captures IQ data used to update the DPD compensation coefficients. The DPD processor 42 updates the DPD compensation coefficients using part of the data in this section in accordance with the DPD processing.

[0099] The DPD processor 42 is set to internally store data used to update the DPD compensation coefficient from the time when the maximum peak is detected within the DPD signal capture window. The TRX-BB unit 32 outputs the DPD training signal so that the DPD training signal has the maximum signal peak at the beginning of the signal section. This allows the DPD processor 42 to store the DPD training signal over the entire signal.

[0100] The following is a chronological explanation of Fig. 11. The control unit of the AAS unit 30 grasps the timing of the DL data slot, and turns on the TX enable signal at timing t1, just before the start of the DL data slot. This activates the transmitter TX in the TRX 51. This period corresponds to the transition period described above.

[0101] During the period from timing t1 to timing t2 when the DL data slot starts, the BF-BB unit 20 generates and outputs a DL-CAL signal. This causes the wireless communication device 10 to perform DL calibration as described above. In this example, the DL calibration is performed periodically, about once every few minutes, during the period from when the TX enable signal is turned on to when the DL data slot starts.

[0102] Note that the DPD signal capture window in the DPD processor 42 is not positioned in this section. The DPD signal capture window is from timing t1 to t sh The DPD processing starts from a time shifted by (=t2-t1). Therefore, in the DPD processing unit 42, the DPD compensation coefficient is not set based on the DL-CAL signal.

[0103] The period from t2 to t3 is the section from the start to the end of the DL data slot. The DPD signal capture window in the DPD processor 42 is set to include this section, and the DPD processor 42 performs DPD compensation processing on the communication signal in the DL data slot.

[0104] After the DL data slot ends at timing t3, the control unit of the AAS unit 30 turns off the TX enable signal at timing t4, which stops the operation of the transmitter TX in the TRX 51.

[0105] In the period from timing t3 to t4, DL calibration is not performed, and therefore no DL-CAL signal is output. However, the TRX-BB unit 32 periodically generates and outputs a DPD training signal. Here, if the transmission signal in the period from t2 to t3 is only SSB, the peak of the DPD training signal is high, and therefore the DPD processing unit 42 sets the DPD compensation coefficient based on the DPD training signal. On the other hand, if a signal of the maximum rated level is transmitted in the period from t2 to t3, the peak of that signal is higher than the DPD training signal, and therefore the DPD compensation coefficient is set based on the maximum rated signal.

[0106] Timings t4 to t5 are a period during which the transmitter TX is not in operation, and during this period, the wireless communication device 10 performs UL communication.

[0107] Next, from timing t5 when the TX enable signal is turned on until timing t6 when the DL data slot starts, the TRX-BB unit 32 generates and outputs a DPD training signal. Here, the DPD signal capture window in the DPD processing unit 42 is located in this section, and the DPD compensation coefficient is set in the DPD processing unit 42 based on the DPD training signal. Note that DL calibration is not performed in the section from timing t4 to t5.

[0108] Timing t6 to t7 is the section from the start to the end of the DL data slot, and during this section, the DPD processor 42 performs DPD compensation processing on the communication signal in the DL data slot.

[0109] Timing t7 to t8 is the interval from the end of the DL data slot until the TX enable signal is turned off. In this interval, the TRX-BB unit 32 generates and outputs a DPD training signal. Here, the DPD signal capture window in the DPD processing unit 42 is located in this interval, and the DPD processing unit 42 sets a DPD compensation coefficient based on the DPD training signal.

[0110] 12 is a flowchart showing signal processing related to output of a DPD training signal and DL communication, focusing on the front and back of one DL data slot. This example shows a case where a DL-CAL signal is not output. The signal processing performed will be described below.

[0111] First, the TRX-BB unit 32 generates and outputs a DPD training signal before the wireless communication device 10 performs DL communication (step S21). After that, the wireless communication device 10 performs DL communication (step S22). After that, the TRX-BB unit 32 generates and outputs a DPD training signal again (step S23). The wireless communication device 10 repeats the above process for each DL data slot to be output. In at least one of steps S11 and S13, the distortion compensation unit 101 updates the DPD compensation coefficient for the DPD training signal. Therefore, in the DPD processing unit 42, the DPD compensation coefficient is set based on the DPD training signal.

[0112] The intervals of timing t1 to t2, t3 to t4, t5 to t6, and t7 to t8 shown above are transition intervals between ON and OFF of the transmitter TX, and are 10 μs as shown in the example of Fig. 4. In this example, the output time of the DPD training signal is set to 8 μs, which is shorter than that, so that the TRX-BB unit 32 can feed back the signal amplified by the transmission amplifier 52 and have it captured by the DPD processing unit 42.

[0113] Moreover, the DPD training signal is a wideband and high-density signal. That is, the DPD compensation coefficient determined by the DPD training signal in the DPD processing unit 42 is set so that compensation is performed in any frequency band of the DPD training signal. That is, the DPD processing unit 42 can set a general-purpose DPD compensation coefficient. Therefore, even if a narrowband signal is output in a DL data slot immediately before the DPD training signal and then a wideband signal is output in the next DL data slot, it is possible to suppress deterioration of the gain of the wideband signal in the next DL data slot. Also, even if a communication signal with few (sparse) frequency components is output in a DL data slot immediately before the DPD training signal and then a communication signal with many (dense) frequency components is output in the next DL data slot, it is possible to suppress deterioration of the gain of the communication signal in the next DL data slot.

[0114] The DPD training signal may be output either before or after each DL data slot, not both before and after each DL data slot. As described above, it is preferable that the DPD training signal is output so as not to overlap with the DL-CAL signal. This can prevent the influence of the DPD training signal on the calibration operation and the DL-CAL weight from being calculated inaccurately. It can also prevent the DPD processing unit 42 from setting a DPD compensation coefficient that is not suitable for a wideband signal due to the influence of the DL-CAL signal. Furthermore, the EVM and ACLR of the transmission amplifier 52 can be improved.

[0115] Furthermore, the frequency band of the DPD training signal covers the frequency band of the DL-CAL signal, and the DPD training signal is output at a timing prior to the DL-CAL signal. Therefore, even when the TRX-BB unit 32 outputs the DL-CAL signal, a general-purpose DPD compensation coefficient is set in advance by the DPD training signal, so that the wireless communication device 10 can accurately calculate the DL-CAL weight. Therefore, the wireless communication device 10 can accurately compensate for variations in amplitude and phase.

[0116] Moreover, the wireless communication device 10 includes a TRX 51 between the DPD processing unit 42 and the transmission amplifier 52, and the TRX-BB unit 32 outputs a DPD training signal at the following timings: That is, at least one of a section before a DL data slot where the transmitter TX of the TRX 51 transitions from off to on, and a section after a DL data slot where the transmitter TX transitions from off to on. As a result, even if the communication signal in the immediately preceding DL data slot is a narrowband signal at a timing when a signal can be output in the DL direction, the wireless communication device 10 can remove the influence of the narrowband signal on the DPD compensation coefficient and set a DPD compensation coefficient compatible with the communication signal in the next DL data slot.

[0117] Furthermore, the DPD training signal has a signal peak at the beginning of the signal section. By detecting this peak, the DPD processing unit 42 can store the DPD training signal throughout the entire signal. This allows the DPD processing unit 42 to reliably set an appropriate DPD compensation coefficient.

[0118] In addition, in the wireless communication device 10 that performs wireless communication, it is possible to perform both the calibration operation that determines the MU-MIMO performance and the DPD compensation processing suitable for wideband signals, thereby further improving the quality of wireless communication.

[0119] Third embodiment Hereinafter, a third embodiment of the present disclosure will be described with reference to the drawings. In the third embodiment, a variation of the signal processing shown in the second embodiment will be described.

[0120] The antennas 34#0 to 34#31 of the wireless communication device 10 described above can transmit wireless signals by, for example, fan beamforming and data beamforming. Here, the transmission of wireless signals by fan beamforming means transmitting wireless signals of approximately constant intensity to the front of the wireless communication device 10 and to a range of a predetermined angle in the horizontal direction from the front, and is used for, for example, broadcast data transmission. In contrast, the transmission of wireless signals by data beamforming means transmitting wireless signals of high intensity to points in front of the wireless communication device 10 and at a certain angle in the horizontal direction, while transmitting wireless signals of low intensity to null points, which are other points in the horizontal direction. This method of transmitting wireless signals is used for data communication with a specific UE. The antennas 34 are arranged in one or more rows (for example, four rows).

[0121] Furthermore, even when the wireless communication device 10 sets the DPD compensation coefficient by the DPD training signal, the wireless communication device 10 transmits wireless signals based on the DPD training signal from the antennas 34#0-#31. However, the wireless signals based on the DPD training signals are not communication signals, and therefore are not signals that are originally transmitted to the UE. Therefore, it is preferable to suppress the power of the wireless signals transmitted based on the DPD training signals as much as possible. In particular, it is preferable to reduce the power of the wireless signals transmitted based on the DPD training signals in the front direction of the wireless communication device 10 (a direction in which data communication with the UE is particularly expected). This makes it possible to suppress the UE in the cell formed by the wireless communication device 10 from receiving unnecessary signals.

[0122] Specifically, the TRX-BB unit 32 generates a DPD training signal for each signal channel so that the phases of the radio signals in each of the adjacent antennas 34 (that is, each of the adjacent signal channels) are different.

[0123] Fig. 13 is a graph showing an example pattern of the gain of the transmission power in the wireless communication device 10. The horizontal axis of the graph in Fig. 13 indicates the horizontal angle from the front of the wireless communication device 10, and the vertical axis of the graph in Fig. 13 indicates the power (dB) of the wireless signal output from the wireless communication device 10 when the reference power is set to 0 dB. Also, (0) in Fig. 13 is a pattern when the antennas 34#0 to #31 all output the DPD training signals as beamforming signals in phase. In contrast, (1) is a pattern when the antenna 34 outputs the DPD training signals as beamforming signals so that the phases of the DPD training signals in adjacent signal channels are inverted (i.e., the phase changes by 180°).

[0124] 13, in the pattern (1), the transmission power in the front direction (near 0°) is about 30 dB lower than in the pattern (0). Furthermore, the peak power of (1) within a range of 45° to the left and right from the front is 10 dB lower than the peak power in the front direction of (0). Therefore, it is possible to prevent UEs in a cell formed by the wireless communication device 10 from receiving unnecessary signals based on the DPD training signal.

[0125] As a process for achieving this effect, it is also possible for the TRX-BB unit 32 to output uncorrelated DPD training signal data for each signal channel. However, as described above, setting the phases of the DPD training signals to be different for each of the adjacent antennas 34 can reduce the storage capacity of the wireless communication device 10 required for generating the DPD training signals.

[0126] It should be noted that the number of antennas 34 in the wireless communication device 10 is not limited to the illustrated number (32). In the wireless communication device 10, the above-described effects can be achieved as long as the DPD training signals are output such that the phases of the signals are different between adjacent antennas.

[0127] The present disclosure is not limited to the above-mentioned embodiments, and can be modified as appropriate without departing from the spirit of the present disclosure. For example, the number of channel signals in the second and third embodiments does not have to be limited to 32. In the second embodiment, the communication signal is not limited to SSB, and may be another signal.

[0128] Furthermore, if there is a circuit configuration in which a DPD processing unit is provided upstream of the receiving amplifier 55, it is possible to achieve both DPD compensation processing and UL calibration by performing processing similar to that of the second embodiment for UL calibration instead of DL calibration.

[0129] The wireless communication systems to which the technology of the present disclosure can be applied are not limited to those described in the second and third embodiments.

[0130] In the above-mentioned embodiment, this disclosure has been described as a hardware configuration, but this disclosure is not limited to this. This disclosure can also be realized by making a processor in a computer execute a computer program to perform the processes (steps) of the device described in the above-mentioned embodiment.

[0131] 14 is a block diagram showing an example of a hardware configuration of an information processing device (signal processing device) for executing the processes of the above-described embodiments. Referring to FIG. 14, the information processing device 90 includes a signal processing circuit 91, a processor 92, and a memory 93.

[0132] The signal processing circuit 91 is a circuit for processing signals in accordance with the control of the processor 92. The signal processing circuit 91 may include a communication circuit for receiving a signal from a transmitting device.

[0133] The processor 92 performs the processing of the device described in the above embodiment by reading and executing software (computer programs) from the memory 93. As an example of the processor 92, one of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), an FPGA (Field-Programmable Gate Array), a DSP (Demand-Side Platform), and an ASIC (Application Specific Integrated Circuit) may be used, or a plurality of them may be used in parallel.

[0134] The memory 93 is configured by a combination of volatile memory and non-volatile memory. The memory 93 may include storage located away from the processor 92. In this case, the processor 92 may access the memory 93 via an I / O (Input / Output) interface (not shown).

[0135] 14, the memory 93 is used to store software modules. The processor 92 can perform the processes described in the above embodiments by reading and executing the software modules from the memory 93.

[0136] As described above, one or more processors included in each device in the above-mentioned embodiments execute one or more programs including instructions for causing a computer to execute the algorithms described with reference to the drawings. This process realizes the signal processing method described in each embodiment.

[0137] 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. Examples of the non-transitory computer readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROM (Read Only Memory), CD-R, CD-R / W, and semiconductor memory (e.g., mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, 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 media include electric signals, optical signals, and electromagnetic waves. The transitory computer readable media can provide the program to the computer via a wired communication path such as an electric wire and an optical fiber, or via a wireless communication path.

[0138] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above. Various modifications that can be understood by a person skilled in the art can be made to the configuration and details of the present disclosure within the scope of the disclosure.

[0139] This application claims priority based on Japanese Patent Application No. 2020-217508, filed on December 25, 2020, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0140] 10 Wireless communication devices 20 BF-BB section 30 AAS Department 31 Optical Transceiver 32 TRX-BB section 33 Front end 34 Antenna 35 Distribution combiner 36 SW 37 CAL-TRX 40 BB unit 41 CFR Processing Section 42 DPD Processing Unit 50 FE unit 51 TRX 52 Transmitting amplifier 53 Directional coupler 54 SW 55 Receiving amplifier 100 Signal processing device 101 Distortion compensation section 102 Amplifier 103 Signal output section

Claims

1. a distortion compensation unit that performs a distortion compensation process for compensating for nonlinear distortion of an input signal and outputs a signal that has been subjected to the distortion compensation process; an amplifier that amplifies the signal output by the distortion compensation means and outputs the signal as a communication signal for communication; a signal output means for outputting an adjustment signal for adjusting the distortion compensation processing as the input signal to the distortion compensation means at a timing when the communication signal is not output, the adjustment signal having a frequency band that covers the frequency band of the communication signal, The signal output means outputs, as the adjustment signal, a signal modulated by Orthogonal Frequency Division Multiplexing (OFDM) or spectrum spread modulation so as not to overlap with a calibration signal output during a calibration operation of the own device. Signal processing device.

2. As the input signal input to the distortion compensation means, the power of the peak level of the adjustment signal is higher than the power of the peak level of the communication signal, The distortion compensation means sets a DPD (Digital Pre-Distortion) compensation coefficient used in the distortion compensation processing based on the adjustment signal. The signal processing device according to claim 1 .

3. a frequency band of the adjustment signal covers a frequency band of the calibration signal, and the adjustment signal is output at a timing prior to the timing of the calibration signal.

3. A signal processing device according to claim 1 or 2.

4. a transmitter between the distortion compensation means and the amplifier; the signal output means outputs the adjustment signal in at least one of a section before a data slot of the communication signal and in which the transmitter transitions from off to on, and a section after the data slot of the communication signal and in which the transmitter transitions from on to off. A signal processing device according to any one of claims 1 to 3.

5. the signal output means outputs, as the adjustment signal, a signal having a signal peak at the beginning of a signal section. A signal processing device according to any one of claims 1 to 4.

6. The signal processing device is a wireless communication device further comprising a wireless transmission means for wirelessly transmitting an output signal from the amplifier. A signal processing device according to any one of claims 1 to 5.

7. The signal processing device includes a plurality of the amplifiers, the wireless transmission means includes a plurality of antennas corresponding to the plurality of amplifiers; The plurality of antennas wirelessly transmit the adjustment signal such that the adjustment signal has a different phase from each other at adjacent antennas. The signal processing device according to claim 6.

8. The distortion compensation means performs a distortion compensation process for compensating for nonlinear distortion of an input signal, and outputs the signal that has been subjected to the distortion compensation process; amplifying the signal output by the distortion compensation means and outputting it as a communication signal for communication; outputting, as the input signal, an adjustment signal for adjusting the distortion compensation process, the adjustment signal having a frequency band that covers the frequency band of the communication signal, at a timing when the communication signal is not output, to the distortion compensation means; The adjustment signal is a signal modulated by OFDM (Orthogonal Frequency Division Multiplexing) or spectrum spread, and is output so as not to overlap with the timing of the calibration signal output during the calibration operation. Signal processing methods.

9. The distortion compensation means performs a distortion compensation process for compensating for nonlinear distortion of an input signal, and outputs the signal that has been subjected to the distortion compensation process; amplifying the signal output by the distortion compensation means and outputting it as a communication signal for communication; outputting, as the input signal, an adjustment signal for adjusting the distortion compensation process, the adjustment signal having a frequency band that covers the frequency band of the communication signal, at a timing when the communication signal is not output, to the distortion compensation means; The adjustment signal is a signal modulated by OFDM (Orthogonal Frequency Division Multiplexing) or spectrum spread, and is output so as not to overlap with the timing of the calibration signal output during the calibration operation. A program that causes a computer to do something.

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