Axis deviation correction method, control device, and program

Abstract

This axial misalignment correction method is for correcting an axial misalignment between a transmission antenna and a reception antenna in a communication system that performs orbital angular momentum (OAM) transmission using one or more OAM modes. In the axial misalignment correction method, while sequentially rotating the transmission antenna and the reception antenna in a given rotation plane, a search is performed for the angle of the transmission antenna and the angle of the reception antenna, so as to maximize an index value calculated on the basis of the reception power of the signal for each OAM mode received by the reception antenna.

Description

[Technical Field]

[0001] The present invention relates to a technique for spatially multiplexing and transmitting wireless signals using the orbital angular momentum (OAM) of electromagnetic waves. [Background technology]

[0002] In recent years, spatial multiplexing transmission technology for wireless signals using OAM has been studied to improve transmission capacity (for example, Non-Patent Document 1). Electromagnetic waves with OAM have equiphase planes distributed in a spiral pattern along the propagation direction, centered on the propagation axis. Electromagnetic waves with different OAM modes propagating in the same direction have orthogonal spatial phase distributions in the direction of the rotation axis. Therefore, signals can be multiplexed and transmitted by separating the signals of each OAM mode modulated with different signal sequences at the receiving device.

[0003] In a wireless communication system using this OAM multiplexing technology, a uniform circular array antenna (hereinafter referred to as a UCA (Uniform Circular Array)) in which multiple antenna elements are arranged at equal intervals in a circle is used to generate, combine, and transmit multiple OAM modes, thereby achieving spatially multiplexed transmission of different signal sequences (see, for example, Non-Patent Document 2). A Butler circuit (Butler matrix circuit), for example, is used to generate and separate signals for multiple OAM modes. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] J.Wang et al., "Terabit free-space data transmission employing orbital angular momentum multiplexing," Nature Photonics, Vol.6, pp.488-496, July 2012. [Non-patent document 2] Y.Yan et al., "High-capacity millimeter-wave communications with orbital angular momentum multiplexing," Nature Commun., vol.5, p.4876, Sep. 2014. [Non-patent document 3] X. Gao, X. Song, Z. Zheng, M. Xie and S. Huang, "Misalignment Measurement of Orbital Angular Momentum Signal Based on Spectrum Analysis and Image Processing," in IEEE Transactions on Antennas and Propagation, vol. 68, no. 1, pp. 521-526, Jan. 2020, doi: 10.1109 / TAP.2019.2938850. Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, OAM multiplexing transmission using UCA enables large-capacity communications, but inter-mode interference occurs if there is an axial misalignment between the transmitting antenna and the receiving antenna.

[0006] A common method for correcting axis misalignment in conventional OAM multiplex transmission is to transmit a reference signal (plane wave), as is done in satellite communications, and then adjust the axis so that the received power is maximized on the receiving side.

[0007] However, the above method is insufficient to suppress inter-mode interference in OAM multiplexed transmission, and more precise axial alignment is required.

[0008] Another conventional technique is a method of estimating the slope by measuring a planar received complex amplitude distribution (Non-Patent Document 3), but performing a planar full search in wireless communications requires a separate planar measuring device or multiple repeated measurements. Therefore, when the method in Non-Patent Document 3 is used as a means for correcting axis misalignment in OAM multiplex transmission, the mechanism becomes complex and the processing becomes slow.

[0009] The present invention has been made in view of the above points, and has an object to provide a technique for easily and quickly correcting axis misalignment in OAM transmission. [Means for solving the problem]

[0010] According to the disclosed technology, there is provided an axis misalignment correction method for correcting an axis misalignment between a transmitting antenna and a receiving antenna in a communication system that performs OAM transmission using one or more OAM modes, the method comprising: While rotating each of the transmitting antenna and the receiving antenna in a certain rotation plane, the angles of the transmitting antenna and the receiving antenna are searched for so that an index value calculated based on the received power of the signal of each OAM mode received by the receiving antenna is maximized. An axis misalignment correction method, When the transmitting antenna and the receiving antenna are rotated sequentially on the rotation plane, the rotation direction of the transmitting antenna and the rotation direction of the receiving antenna are the same or opposite, and the absolute value of the rotation angle of the transmitting antenna and the absolute value of the rotation angle of the receiving antenna are equal. A method for correcting axis misalignment is provided. [Effects of the Invention]

[0011] According to the disclosed technology, axis misalignment correction in OAM transmission can be performed easily and quickly. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 10 is a diagram illustrating an example of phase setting of a UCA for generating an OAM mode signal. [Figure 2] 1A and 1B are diagrams illustrating examples of phase distribution and signal intensity distribution of an OAM multiplexed signal. [Figure 3] 1 is a configuration diagram of a communication system according to an embodiment of the present invention; [Figure 4]FIG. 10 is a diagram showing an image of reverse rotation and same direction rotation. [Figure 5] FIG. 10 is a diagram showing an image of an angle. [Figure 6] FIG. 1 is a diagram illustrating an example of the configuration of an array antenna. [Figure 7] FIG. 10 is a diagram showing the relationship between the angle of the transmitting antenna / receiving antenna and the transmission capacity. [Figure 8] FIG. 2 is a sequence diagram showing an example of a processing flow according to an embodiment of the present invention. [Figure 9] FIG. 2 is a configuration diagram of a control unit 230 (control device). [Figure 10] FIG. 1 is a diagram illustrating the configuration of a computer. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention (the present embodiment) will be described with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0014] (About UCA) First, an example of basic settings and operations related to UCA used in the transmitting device and receiving device of this embodiment will be described.

[0015] Fig. 1 is a diagram showing an example of phase settings of a UCA for generating an OAM mode signal. The UCA shown in Fig. 1 is a UCA consisting of eight antenna elements.

[0016] In Figure 1, signals for OAM modes 0, 1, 2, 3, ... on the transmitting side are generated by the phase difference of the signals supplied to each antenna element (indicated by ●) of the UCA. That is, signals for OAM mode n are generated by setting the phase of the signal supplied to each antenna element so that the phase rotates n times (n x 360 degrees). For example, when the UCA is configured with m = 8 antenna elements as shown in Figure 1 and a signal for OAM mode n = 2 is generated, a phase difference of 360n / m = 90 degrees counterclockwise is set for each antenna element (0 degrees, 90 degrees, 180 degrees, 270 degrees, 0 degrees, 90 degrees, 180 degrees, 270 degrees) so that the phase rotates twice, as shown in Figure 1 (3).

[0017] Note that a signal with the phase rotation direction reversed to that of an OAM mode n signal is called OAM mode -n. For example, the phase rotation direction of a positive OAM mode signal is counterclockwise, and the phase rotation direction of a negative OAM mode signal is clockwise.

[0018] Spatial multiplexing wireless communication can be performed by generating different signal sequences as signals in different OAM modes and transmitting the generated signals simultaneously. On the transmitting side, signals to be transmitted in each OAM mode can be generated and combined in advance and the combined signal for each OAM mode can be transmitted using a single UCA, or multiple UCAs can be used to transmit signals for each OAM mode using different UCAs for each OAM mode.

[0019] To separate the OAM multiplexed signal on the receiving side, the phase of each antenna element of the UCA on the receiving side can be set to be opposite to the phase of the antenna element on the transmitting side.

[0020] However, if interference occurs between OAM modes due to factors such as misalignment between the transmitting and receiving antennas, it becomes necessary to separate the mixed OAM mode signals through digital signal processing such as channel equalization and successive interference cancellation. Interference between OAM modes means, for example, that a signal transmitted from a transmitting device in OAM mode 1 is output as an OAM mode 2 signal on the receiving side.

[0021] Figure 2 shows examples of the phase distribution and signal intensity distribution of an OAM multiplexed signal. In Figures 2(1) and (2), the arrows represent the phase distribution of OAM mode 1 and OAM mode 2 signals as seen from the transmitter at an end face perpendicular to the propagation direction (orthogonal propagation plane). The arrows start at 0 degrees, and the phase changes linearly until they end at 360 degrees. In other words, an OAM mode n signal propagates with its phase rotating n times (n x 360 degrees) on the orthogonal propagation plane. Note that the arrows for the phase distribution of OAM mode -1 and -2 signals point in opposite directions.

[0022] The signal intensity distribution and the position where the signal intensity is maximized differ for each OAM mode. However, the intensity distribution is the same for the same OAM mode but with a different sign. Specifically, the higher the order of the OAM mode, the farther the position where the signal intensity is maximized is from the propagation axis (Non-Patent Document 2). Here, an OAM mode with a larger value is referred to as a higher-order mode. For example, an OAM mode 3 signal is a higher-order mode than OAM mode 0, OAM mode 1, and OAM mode 2 signals.

[0023] Figure 2(3) shows the position where the signal strength is maximum for each OAM mode as a circle. The higher the OAM mode, the farther the position where the signal strength is maximum is from the central axis. Also, the beam diameter of the OAM mode multiplexed signal expands depending on the propagation distance, and the circle showing the position where the signal strength is maximum for each OAM mode becomes larger.

[0024] The system configuration and operation example of this embodiment will be described in detail below.

[0025] (Example of communication system configuration and operation overview) 3 is a diagram showing an example of the configuration of a communication system according to an embodiment of the present invention. This communication system includes a transmitting device 100 and a receiving device 00.

[0026] 3, the transmitting device 100 includes a waveform generation processing unit 110, an OAM generation processing unit 120, an antenna unit 130, a communication signal processing unit 140, and an axis misalignment correction unit 150. The receiving device 200 includes an antenna unit 210, an OAM demultiplexing processing unit 220, a control unit 230, a signal processing unit 240, a communication signal processing unit 250, and an axis misalignment correction unit 260.

[0027] Both antenna units 130 and 210 have a UCA. In this embodiment, both OAM generation processing unit 120 and OAM demultiplexing processing unit 220 are analog circuits such as Butler matrices. However, using analog circuits for OAM generation processing unit 120 and OAM demultiplexing processing unit 220 is just one example, and OAM generation / demultiplexing may also be performed by digital processing. An overview of the operation of transmitting device 100 and receiving device 00 is as follows.

[0028] The waveform generation processing unit 110 generates carrier waves of one or more frequencies. The communication signal processing unit 140 generates analog signals from transmission signal sequences (digital signals). The OAM generation processing unit 120 generates signals of multiple OAM modes from the analog signals carried on carrier waves. As an example, signals of eight OAM modes are generated.

[0029] It should be noted that OAM generation processing unit 120 may generate a signal in one OAM mode. Antenna unit 130 transmits an OAM multiplexed signal in which signals in one or more OAM modes are multiplexed.

[0030] Antenna unit 210 of receiving device 200 receives the OAM multiplexed signal. OAM demultiplexing processor 220 demultiplexes the signals of each OAM mode from the OAM multiplexed signal. Communication signal processor 250 generates and outputs a received signal sequence from the signals of each OAM mode obtained by OAM demultiplexing processor 220.

[0031] The control unit 230 estimates the SIR or transmission capacity for each OAM mode from the received signal power and inter-mode interference power, and searches for the optimal state quickly and accurately by controlling the relative angles of the transmitting and receiving antennas within a plurality of predetermined planes so that the SIR or transmission capacity tends to converge to a local maximum (maximum). Note that either the SIR or transmission capacity may be used in the calculation for the search. Also, the SIR and transmission capacity are examples of index values, and the search may be performed using an index value other than the SIR or transmission capacity. In the following explanation, transmission capacity will be used as an example.

[0032] Specifically, as will be described later, the search utilizes the characteristic that the transmission capacity during axis misalignment is convex when the absolute values ​​of the axis misalignments of the transmitter and receiver are equal, and convergence is facilitated by taking a search path that moves simultaneously in the same or opposite directions.

[0033] In the above-described search process, the signal processing unit 240 receives an angle control amount from the control unit 230, generates a control signal instructing control of the angle control amount, and notifies the axis shift correction unit 260 of the control signal. The axis shift correction unit 260 notifies the axis shift correction unit 150 of the transmitting device 100 of the control signal.

[0034] The axis shift correction unit 150 in the transmitting device 100 adjusts (changes) the angle of the transmitting antenna. The transmitting antenna is the UCA in the antenna unit 130. The axis shift correction unit 260 in the receiving device 200 adjusts (changes) the angle of the receiving antenna. The receiving antenna is the UCA in the antenna unit 210.

[0035] Any method may be used to adjust the angle of the transmitting antenna. For example, the angle of the antenna unit 130 (including the member supporting the UCA) to which the transmitting antenna is fixed may be adjusted, or the angle of the transmitting device 100 to which the antenna unit 130 is fixed may be adjusted.

[0036] Similarly, any method may be used to adjust the angle of the receiving antenna. For example, the angle of antenna unit 210 (including the member supporting UCA) to which the receiving antenna is fixed may be adjusted, or the angle of receiving device 200 to which antenna unit 210 is fixed may be adjusted.

[0037] Alternatively, the angle of the transmitting antenna itself may be adjusted, or the angle of the receiving antenna itself may be adjusted.

[0038] (About angle adjustment) Here, the transmitting antenna and the receiving antenna are collectively referred to as the "transmitting / receiving antenna." In this embodiment, in the angle adjustment, the transmitting / receiving antenna is rotated so as to change the angle of the propagation axis of the transmitting / receiving antenna (an axis extending from the center of the circular UCA perpendicular to the surface of the UCA, which may be simply referred to as the "axis") from a reference axis as seen from the transmitting / receiving antenna. The reference axis is, for example, the propagation axis of the transmitting antenna when it coincides with the propagation axis of the receiving antenna (i.e., the axes are aligned).

[0039] The rotation may be performed in any manner, but in this embodiment, a horizontal or vertical plane is used as the rotation plane, and rotation is performed on the horizontal or vertical plane.

[0040] For convenience, we will assume that the transmitting / receiving antennas are circular disks. The disk is also placed vertically on a horizontal plane (ground) (i.e., the propagation axis is parallel to the horizontal plane). Rotation on the horizontal plane means rotating the disk around an axis that is the diameter of the disk and perpendicular to the horizontal plane. Rotation on the vertical plane means rotating the disk around an axis that is the diameter of the disk and parallel to the horizontal plane.

[0041] In this embodiment, the rotation directions of the transmitting and receiving antennas are also determined. For example, when the transmitting antenna is rotated clockwise on the horizontal plane and the receiving antenna is rotated clockwise on the horizontal plane, this is referred to as rotating the transmitting antenna and the receiving antenna in the "same rotation direction." The same applies to the vertical plane.

[0042] For example, if the transmitting antenna is rotated clockwise in the horizontal plane and the receiving antenna is rotated counterclockwise in the horizontal plane, this is called rotating the transmitting antenna and the receiving antenna in "counter-rotating directions." The same applies to the vertical plane.

[0043] In this embodiment, when the transmitting / receiving antenna is rotated clockwise, the angle of deviation of the propagation axis from the reference axis as seen from the transmitting / receiving antenna is defined as a positive angle, and the opposite angle is defined as a negative angle. Note that the definitions of positive and negative may be reversed.

[0044] Figure 4 shows an image of reverse and same direction rotation. Figure 5 shows an image of the angle. θ in Figure 5 is positive.

[0045] (Antenna configuration example) 6(a), (b), and (c) show configuration examples of the array antenna in the antenna units 130 and 210. As shown in the figures, the array antenna in the antenna units 130 and 210 may be a UCA, a multi-UCA, or a UCA having a central antenna (which may also be a multi-UCA).

[0046] Furthermore, the antenna units 130 and 210 may be Cassegrain antennas, as shown in FIG. 6(d).

[0047] If the transmitting antenna and the receiving antenna each have a central antenna (antenna element), they can be used for coarse angle adjustment. In this case, for example, the axis misalignment correction unit 150 / 260 pre-adjusts the axes of the transmitting / receiving antennas coarsely so that the received power between the central antennas is maximized. "Coarse adjustment" means, for example, adjusting the angular misalignment between the transmitting antenna and the receiving antenna to about 1°.

[0048] Furthermore, the transmitting device 100 / receiving device 200 may be provided with a "scope and target" or a "laser and light receiving target", and the axis deviation correcting unit 150 / 260 may use these to roughly adjust the axis in advance.

[0049] (Transmission capacity characteristics when the axis is misaligned) As mentioned above, in OAM multiplex transmission using an array antenna, the transmission capacity in the event of an axis shift (the transmission capacity calculated by the control unit 230) is characterized by being convex when the absolute values ​​of the axis shift amounts of the transmitting antenna and the receiving antenna are equal.

[0050] These features will be explained with reference to Fig. 7, which is a diagram based on the results of a simulation. The vertical axis of Fig. 7 represents the amount of axial misalignment (+1° to -1°) of the transmitting antenna on a certain plane of rotation, and the horizontal axis represents the amount of axial misalignment (+1° to -1°) of the receiving antenna. The shading / diagonal lines in each square in Fig. 7 give an idea of ​​the magnitude of the transmission capacity when there is an axial misalignment corresponding to that square.

[0051] Basically, the transmission capacity is maximum when the amount of axis misalignment between the transmitting antenna and the receiving antenna is zero, and the transmission capacity decreases as the amount of axis misalignment increases.

[0052] This section explains the change in transmission capacity when the absolute values ​​of the axis misalignment changes between the transmitting antenna and the receiving antenna are equal when the antennas are rotated sequentially. Here, (axis misalignment value X of the transmitting antenna, axis misalignment value Y of the receiving antenna) is written as (Tx=X, Rx=Y).

[0053] Line A in Figure 7 shows the change in transmission capacity when the axis misalignment is changed as follows: (Tx=0.2, Rx=-0.6), (Tx=0.1, Rx=-0.5), ..., (Tx=-0.1, Rx=-0.3), (Tx=-0.2, Rx=-0.2). In other words, the axis misalignment (the angle by which the antenna is rotated) is changed by rotating the transmit and receive antennas in opposite directions with the absolute value of the axis misalignment change being equal: (Tx=0, Rx=0), (Tx=-0.1, Rx=0.1), ..., (Tx=-0.3, Rx=0.3), (Tx=-0.4, Rx=0.4). Line A, which shows this change, is parallel to the diagonal line (reverse rotation axis) shown in Figure 7D.

[0054] When the angle is changed as shown by line A, the transmission capacity increases in accordance with the change in angle, and is maximum at a point (mass) on the axis in the same direction of rotation. If the angle is then changed so that line A extends beyond the point on the axis in the same direction of rotation, the transmission capacity decreases in accordance with the change in angle. This is what is meant by the "convex" mentioned above.

[0055] Similarly, line B in Figure 7 shows the change in transmission capacity when the amount of axis misalignment is changed as follows: (Tx=0, Rx=0.4), (Tx=-0.1, Rx=0.3), and (Tx=-0.2, Rx=0.2). In other words, the amount of change in axis misalignment (the angle by which the antenna is rotated) is changed as follows: (Tx=0, Rx=0), (Tx=-0.1, Rx=-0.1), and (Tx=-0.2, Rx=-0.2), where the transmit antenna and receive antenna are rotated in the same direction with the same absolute value of the change in axis misalignment. Line B of this change is parallel to the diagonal line (axis of the same rotation direction) shown in Figure 7C.

[0056] When the angle is changed as shown by line B, the transmission capacity increases with the change in angle, and is maximum at the point (mass) on the counter-rotation axis. If the angle is then changed so that line B extends beyond the point on the counter-rotation axis, the transmission capacity decreases with the change in angle.

[0057] In other words, when starting a search from a certain point, such as the start point of line A or the start point of line B, an efficient search can be performed by finding the point at which the maximum value is obtained by rotating in the opposite direction (or the same direction), and then finding the point at which the maximum value is obtained by rotating in the same direction (or the opposite direction), as shown by line E or line F.

[0058] In other words, the results tend to converge more easily when searching for the route between lines A and E in Figure 7, or the route between lines B and F. The above example was explained in terms of transmission capacity, but similar characteristics apply when using SIR.

[0059] (Processing flow) Next, an example of the operation of the communication system will be described with reference to the flowchart of Fig. 8. Here, an example of searching for an optimum value at equal intervals (for example, in increments of 0.01°) will be described.

[0060] In S101, the transmitting device 100 constantly transmits one CW (continuous wave) or multiple CWs within the transmission band from each of different modes. The CW may also be called a CW signal. Here, if the number of frequencies is X and the number of modes is M+1, the following frequencies are used to transmit the CW signal: X is an integer equal to or greater than 1, and M is an integer equal to or greater than 0. In other words, the number of frequencies may be 1, and the number of modes may also be 1.

[0061] OAM mode 0 transmit frequency: f 01 , f 02 f 0x OAM mode 1 transmit frequency: f 11 , f 12 f 1x OAM mode 2 transmit frequency: f 21 , f 22 f 2x ... OAM mode M transmit frequency: f M1 , f M2 f Mx The above-described OAM multiplexed signal (OAM multiplexed and frequency multiplexed CW signal) is transmitted from the transmitting device 100 and received by the receiving device 200. In the receiving device 200, the CW signal for each OAM mode is sent to the control unit 230.

[0062] The control unit 230 of the receiving device 200 sets the number of trials N to N=1 and the initial value of the transmission capacity C to C0=0.

[0063] In S102, the control unit 230 determines the rotation plane (horizontal plane / vertical plane) and the rotation direction (same rotation direction / reverse rotation direction). Initially, any one of these may be determined.

[0064] In S103, control unit 230 measures the received power of all the above frequencies for each reception OAM mode by performing an FFT on the received waveform, for example.

[0065] In S104, the control unit 230 calculates the total received power in the own mode (for example, in the case of OAM mode 0, the frequency f 01 , f 02 f 0x The total received power of other modes (for example, in the case of OAM mode 0, the frequency f 01 , f 02 f 0N The SIR (S / I) is calculated for each receive OAM mode, where I is the sum of the signal powers other than the SIR (S / I).

[0066] In S105, the control unit 230 calculates the transmission capacity C of the Nth trial using the following formula: N Σ is the sum of the modes C N =Σ{log2(1+SIR)} When the SIR is used as the index value, for example, the sum of the SIRs for the modes is used.

[0067] In S106, the control unit 230 N and N-1th transmission capacity C N-1 Compared with C N <CN-1 If so, proceed to S107, C N <C N-1 If not, proceed to S109.

[0068] In S107, the control unit 230 instructs the axis shift correction unit 260 / 150 via the signal processing unit 240 to rotate the receiving / transmitting antenna to the angle set at the (N-1)th angle as the optimal value. The axis shift correction unit 260 / 150 rotates the receiving / transmitting antenna to the target angle.

[0069] In S108, if all faces and rotation directions have been searched, the process ends, and if other faces or rotation directions are to be searched, the process returns to S102. Note that each face / each rotation direction may be searched multiple times.

[0070] In S109, the control unit 230 determines the next angle (i.e., an increase or decrease of 0.01°) and instructs the axis shift correction unit 260 / 150 to rotate by that angle via the signal processing unit 240. The axis shift correction unit 260 / 150 rotates the receiving / transmitting antennas by an angle of the same absolute value.

[0071] The above search algorithm is merely an example. The optimum angle may be calculated using a convex optimization algorithm such as the bisection method or Newton's method.

[0072] Furthermore, in the calculation of the SIR / transmission capacity described above, it is also possible to use only OAM modes whose received power exceeds a predetermined threshold from among all OAM modes in use. This allows axis misalignment to be corrected using a number of OAM modes that is fewer than the number of available OAM modes. The process of excluding OAM modes whose received power is equal to or less than the predetermined threshold is performed, for example, at the beginning of loop processing. By using only OAM modes whose received power exceeds the predetermined threshold, it is possible to reduce the signal processing load without affecting accuracy.

[0073] (Regarding the control unit 230) An example of the functional configuration of the control unit 230 is shown in Fig. 9. The control unit 230 may include a functional unit that transmits control signals to the axis deviation correction unit 260 and the like, and Fig. 9 shows an example in which the control unit 230 includes such a functional unit.

[0074] Furthermore, the control unit 230 may be provided outside the receiving device 200. The control unit 230 provided outside the receiving device 200 may be called a control device. Furthermore, all devices including the control unit 230 may be called a control device. In other words, the receiving device 200 may be called a control device. When the control device is provided outside the receiving device 200, the control device and the receiving device 200 are connected via a network.

[0075] 9, the control unit 230 (control device) has an estimation unit 231, a search unit 232, and a control signal transmission unit 233. Note that the control signal transmission unit 233 may be included in the search unit 232.

[0076] The estimation unit 231 receives the signal output from the OAM separation processing unit 220 and calculates the received power, SIR, and transmission capacity. The received power may be measured by the OAM separation processing unit 220, and the value of the received power may be transmitted from the OAM separation processing unit 220 to the estimation unit 231. The search unit 232 searches for an optimal angle, for example, using the logic of the flow in FIG. 8. The control signal transmission unit 233 transmits a control signal to the axis misalignment correction unit 260, instructing it to rotate by the angle calculated by the search unit 232. The control signal transmission unit 233 may transmit the control signal to both the axis misalignment correction unit 260 and the axis misalignment correction unit 150.

[0077] The control device or control unit 230 (hereinafter referred to as control device / control unit 230) may be realized using a dedicated circuit, or may be realized by a computer and software.

[0078] That is, the control device / control unit 230 can be realized by using hardware resources such as a CPU and memory built into a computer to execute a program corresponding to the processing performed by the control device / control unit 230. The program can be recorded on a computer-readable recording medium (such as a portable memory) and can be saved or distributed. The program can also be provided via a network such as the Internet or email. The computer may also be a virtual machine on a cloud.

[0079] Fig. 10 is a diagram showing an example of the hardware configuration of the computer. The computer in Fig. 10 includes a drive device 1000, an auxiliary storage device 1002, a memory device 1003, a CPU 1004, an interface device 1005, a display device 1006, an input device 1007, an output device 1008, and the like, all of which are interconnected by a bus BS. The computer may further include a GPU.

[0080] A program for realizing processing on the computer is provided by a recording medium 1001 such as a CD-ROM or a memory card. When the recording medium 1001 storing the program is set in the drive device 1000, the program is installed from the recording medium 1001 to the auxiliary storage device 1002 via the drive device 1000. However, the program does not necessarily have to be installed from the recording medium 1001, but may be downloaded from another computer via a network. The auxiliary storage device 1002 stores the installed program as well as necessary files, data, etc.

[0081] The memory device 1003 reads and stores the program from the auxiliary storage device 1002 when an instruction to start the program is received. The CPU 1004 realizes functions related to the control device / control unit 230 in accordance with the program stored in the memory device 1003. The interface device 1005 is used as an interface for connecting to a network, etc. The display device 1006 displays a GUI (Graphical User Interface) or the like according to the program. The input device 1007 is composed of a keyboard, mouse, buttons, a touch panel, etc., and is used to input various operation instructions. The output device 1008 outputs the results of calculations.

[0082] (Effects of the embodiment) The technology according to this embodiment does not require a full search using planar distribution measurements as in conventional technology, and enables simple and fast axial alignment between the transmitting antenna and receiving antenna that perform OAM transmission.

[0083] More specifically, by adjusting the initial state of the transmitting / receiving antennas within a predetermined range (axis misalignment of about 1°), the results converge without diverging.

[0084] Furthermore, although the received power of each OAM mode varies greatly depending on distance, etc., by using SIR or the transmission capacity based on it as an index, thresholds for determining convergence are not required. Another feature is that there are no restrictions on installation (distance, etc.), since the initial conditions for convergence (initial angle deviation range) are uniquely determined in advance by the array antenna configuration, regardless of the antenna installation situation (distance, etc.).

[0085] (Addendum) This specification describes at least the axis deviation correction method, control device, and program described in the following sections. (Additional note 1) An axis misalignment correction method for correcting an axis misalignment between a transmitting antenna and a receiving antenna in a communication system that performs OAM transmission using one or more OAM modes, comprising: While rotating each of the transmitting antenna and the receiving antenna in a certain rotation plane, the angles of the transmitting antenna and the receiving antenna are searched for so that an index value calculated based on the received power of the signal of each OAM mode received by the receiving antenna is maximized. Axis misalignment correction method. (Additional note 2) When the transmitting antenna and the receiving antenna are rotated sequentially on the rotation plane, the rotation direction of the transmitting antenna and the rotation direction of the receiving antenna are the same or opposite, and the absolute value of the rotation angle of the transmitting antenna and the absolute value of the rotation angle of the receiving antenna are equal. The axis deviation correction method described in appended item 1. (Additional note 3) The index value is the sum of SIRs or the sum of transmission capacities for the one or more OAM modes. 3. The axis deviation correction method according to claim 1 or 2. (Additional note 4) Calculating the index value using only the OAM modes in which the received power exceeds a predetermined threshold, among the one or more OAM modes. 4. The axis deviation correction method according to any one of claims 1 to 3. (Additional note 5) A control device that corrects an axis misalignment between a transmitting antenna and a receiving antenna in a communication system that performs OAM transmission using one or more OAM modes, an estimation unit that calculates an index value based on the received power of the signal in each OAM mode received by the receiving antenna; a search unit that searches for angles of the transmitting antenna and the receiving antenna such that the index value is maximized while sequentially rotating the transmitting antenna and the receiving antenna on a certain rotation plane; A control device comprising: (Additional note 6) A program for causing a computer to function as each part of the control device described in appended paragraph 5.

[0086] Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0087] 100 Transmitting device 110 Waveform generation processing section 120 OAM generation processing unit 130 Antenna section 140 Communication signal processing section 150 Axis deviation correction unit 200 receiving device 210 Antenna section 220 OAM separation processing unit 230 Control Unit 231 Estimation Department 232 Search Department 233 Control signal transmitter 240 Signal Processing Unit 250 Communication signal processing section 260 Axis offset correction unit 1000 Drive Device 1001 Recording media 1002 Auxiliary storage device 1003 Memory device 1004 CPU 1005 Interface device 1006 Display device 1007 Input Device 1008 Output Device

Claims

1. 1. An axis misalignment correction method for correcting an axis misalignment between a transmitting antenna and a receiving antenna in a communication system that performs OAM transmission using one or more OAM modes, comprising: an axis misalignment correction method for searching for angles of the transmitting antenna and the receiving antenna such that an index value calculated based on the received power of signals in each OAM mode received by the receiving antenna is maximized while rotating the transmitting antenna and the receiving antenna sequentially on a certain rotation plane, When the transmitting antenna and the receiving antenna are rotated sequentially on the rotation plane, the rotation direction of the transmitting antenna and the rotation direction of the receiving antenna are the same or opposite, and the absolute value of the rotation angle of the transmitting antenna and the absolute value of the rotation angle of the receiving antenna are equal. Axis misalignment correction method.

2. 1. An axis misalignment correction method for correcting an axis misalignment between a transmitting antenna and a receiving antenna in a communication system that performs OAM transmission using one or more OAM modes, comprising: an axis misalignment correction method for searching for angles of the transmitting antenna and the receiving antenna such that an index value calculated based on the received power of signals in each OAM mode received by the receiving antenna is maximized while rotating the transmitting antenna and the receiving antenna sequentially on a certain rotation plane, The index value is the sum of SIRs or the sum of transmission capacities for the one or more OAM modes. Axis misalignment correction method.

3. 1. An axis misalignment correction method for correcting an axis misalignment between a transmitting antenna and a receiving antenna in a communication system that performs OAM transmission using one or more OAM modes, comprising: an axis misalignment correction method for searching for angles of the transmitting antenna and the receiving antenna such that an index value calculated based on the received power of signals in each OAM mode received by the receiving antenna is maximized while rotating the transmitting antenna and the receiving antenna sequentially on a certain rotation plane, Among the one or more OAM modes, only an OAM mode in which the received power exceeds a predetermined threshold is used to calculate the index value. Axis misalignment correction method.

4. A control device for correcting an axis misalignment between a transmitting antenna and a receiving antenna in a communication system that performs OAM transmission using one or more OAM modes, comprising: an estimation unit that calculates an index value based on the received power of the signal in each OAM mode received by the receiving antenna; a search unit that searches for angles of the transmitting antenna and the receiving antenna such that the index value is maximized while sequentially rotating the transmitting antenna and the receiving antenna on a certain rotation plane, When the transmitting antenna and the receiving antenna are rotated sequentially on the rotation plane, the rotation direction of the transmitting antenna and the rotation direction of the receiving antenna are the same or opposite, and the absolute value of the rotation angle of the transmitting antenna and the absolute value of the rotation angle of the receiving antenna are equal. Control device.

5. A control device for correcting an axis misalignment between a transmitting antenna and a receiving antenna in a communication system that performs OAM transmission using one or more OAM modes, comprising: an estimation unit that calculates an index value based on the received power of the signal in each OAM mode received by the receiving antenna; a search unit that searches for angles of the transmitting antenna and the receiving antenna such that the index value is maximized while sequentially rotating the transmitting antenna and the receiving antenna on a certain rotation plane, The index value is the sum of SIRs or the sum of transmission capacities for the one or more OAM modes. Control device.

6. A control device for correcting an axis misalignment between a transmitting antenna and a receiving antenna in a communication system that performs OAM transmission using one or more OAM modes, comprising: an estimation unit that calculates an index value based on the received power of the signal in each OAM mode received by the receiving antenna; a search unit that searches for angles of the transmitting antenna and the receiving antenna such that the index value is maximized while sequentially rotating the transmitting antenna and the receiving antenna on a certain rotation plane, The estimation unit calculates the index value using only an OAM mode in which the received power exceeds a predetermined threshold, among the one or more OAM modes. Control device.

7. A program for causing a computer to function as each unit in the control device according to any one of claims 4 to 6.

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