Wireless transmission system, wireless transmission method, and transmission device

Abstract

One aspect of the present invention is a wireless transmission system comprising a transmitter that emits an electromagnetic wave, the electromagnetic wave being an airy beam that propagates so that sidelobes spread out in a direction parallel to the ground.

Description

Wireless transmission system, wireless transmission method, and transmitting device

[0001] The present invention relates to a wireless transmission system, a wireless transmission method, and a transmitting device.

[0002] In recent years, there has been increasing interest in wireless transmission technology.

[0003] Doohwan Lee, Yasunori Yagi, and Hiroyuki Shiba. “Multishape radio: new approach to utilizing the physical properties of electromagnetic waves.” IEICE Communications Express 11.9 (2022): 571-576.

[0004] When forming a wireless transmission area, electromagnetic waves have the property of spreading evenly in all directions, so the electromagnetic waves may spread to areas where area formation is not required, such as the sky, resulting in a loss of power. The electromagnetic waves may be, for example, radio waves, light, or terahertz waves.

[0005] However, when area formation is performed using beamforming, which is a method of forming an area toward a desired terminal, the above problems are solved, but because the wireless space is formed by giving directivity to the desired direction each time, it is difficult to form an area flexibly, and communication with terminals over a wide range may be difficult. As such, it has been difficult to balance reducing energy loss with expanding the areas where communication is possible.

[0006] In view of the above circumstances, an object of the present invention is to provide a technology that achieves both a reduction in energy loss in wireless transmission and an expansion of areas where communication is possible.

[0007] One aspect of the present invention is a wireless transmission system comprising a transmitter that emits electromagnetic waves, the electromagnetic waves being Airy beams that propagate in a direction parallel to the ground with side lobes spreading.

[0008] One aspect of the present invention is a wireless transmission method implemented by a wireless transmission system comprising a transmitter that radiates electromagnetic waves, the electromagnetic waves being Airy beams that propagate in a direction parallel to the ground with side lobes spreading, the wireless transmission method including an emission step in which the transmitter emits the Airy beam.

[0009] One aspect of the present invention is a transmitting device that includes an optical system that converts electromagnetic waves into an Airy beam, and the Airy beam propagates so that side lobes spread in a direction parallel to the ground.

[0010] The present invention makes it possible to reduce energy loss in wireless transmission while expanding the areas where communication is possible.

[0011] 1 is an explanatory diagram illustrating a wireless transmission system according to an embodiment; a diagram illustrating an example of the configuration of a transmitter according to an embodiment; a diagram illustrating an example of the hardware configuration of a control system according to an embodiment; a flowchart illustrating an example of the flow of processing executed in the wireless transmission system according to an embodiment; an explanatory diagram illustrating a wireless transmission system according to a modified example; a diagram illustrating an example of the configuration of a transmitter according to a modified example.

[0012] 1 is an explanatory diagram illustrating a wireless transmission system 100 according to an embodiment. The wireless transmission system 100 includes a transmitter 1 that performs wireless transmission, which is transmission of data or power, to a receiver such as a receiver 9-1 by radiating electromagnetic waves. The electromagnetic waves radiated by the transmitter 1 are Airy beams that propagate in a direction parallel to the ground (hereinafter referred to as the "ground direction") with side lobes spreading.

[0013] The Airy beam transmitted by the transmitter 1 may be, for example, a radio wave, light, or a terahertz wave. For simplicity of explanation, the following description will be given taking the case where the Airy beam is a radio wave as an example.

[0014] FIG. 1 shows a PQ coordinate system, which is a coordinate system defined by a P axis and a Q axis. The P axis and the Q axis are perpendicular to each other. In FIG. 1, the origin O is the origin of the PQ coordinate system. In FIG. 1, the area where the coordinate Q of the Q axis is 0 or less is land, and the area where the coordinate Q of the Q axis is 0 (i.e., Q = 0) is the surface of the land. Therefore, the area where Q = 0 is an example of the ground surface. Therefore, in the example of FIG. 1, the direction parallel to the P axis is an example of the ground direction.

[0015] The following equation (1) shown in Fig. 1 shows the characteristics of an Airy beam. The characteristics of an Airy beam are expressed by the following equation (1) using a coordinate system (hereinafter referred to as the "XZ coordinate system") defined by a Z axis parallel to the direction in which the Airy beam is emitted by transmitter 1 and an X axis perpendicular to the Z axis, with the origin being the position at which transmitter 1 emits the Airy beam. The origin V in Fig. 1 is the origin of the XZ coordinate system.

[0016]

[0017] Here, λ represents the wavelength of the Airy beam, and f represents the focal length of a Fourier transform lens (FTL) used to convert the electromagnetic wave into an Airy beam. b is a parameter according to the optical system that converts the electromagnetic wave into an Airy beam (hereinafter referred to as the "Airy beam generating system"). More specifically, b is a value that determines the phase distribution of a phase modulating lens (PML) used to convert the electromagnetic wave into an Airy beam. A specific example of the phase distribution of a phase modulating lens is Equation (2), which will be described later.

[0018] Both the Fourier transform lens and the phase modulation lens are included in the Airy beam generating system, that is, the Fourier transform lens and the phase modulation lens are optical elements that constitute the Airy beam generating system.

[0019] Using the above formula (1), the result showing the locus of the main lobe of the Airy beam obtained for wavelength λ1 is curve C-1. Using the above formula (1), the result showing the locus of the main lobe of the Airy beam obtained for wavelength λ2, which is different from wavelength λ1, is curve C-2.

[0020] Area A-1 in Figure 1 shows the side lobes of an Airy beam of wavelength λ1. Area A-1 is an area where a receiver present there, such as receiver 9-1, can receive electromagnetic waves of wavelength λ1 transmitted by transmitter 1. Therefore, area A-1 is an example of a so-called reception area for transmitter 1 (i.e., an area where data or power can be received). Position P1 is an example of the edge of the reception area.

[0021] 1, the area A-1 has a spread parallel to the ground surface. This is because the Airy beam transmitted from the transmitter 1 propagates in such a way that the side lobes spread in a direction parallel to the ground surface.

[0022] 1 shows that the Airy beam does not reach the region above the transmitter 1. Therefore, in FIG. 1, electromagnetic waves do not diffuse in the region above the transmitter 1.

[0023] 1, the area where the receiver 9-2 is located is an area where the main lobe or side lobe of wavelength λ1 and wavelength λ2 do not reach, so the receiver 9-2 does not receive the electromagnetic waves of wavelength λ1 and wavelength λ2 transmitted by the transmitter 1.

[0024] In this way, the Airy beam has the property that the side lobes exist only in a specific region and have no intensity in other regions.Furthermore, the trajectory of the beam curves as it propagates.

[0025] The wireless transmission system 100 is a system that performs wireless transmission by utilizing the properties of such Airy beams. In the wireless transmission system 100, as shown in the example of Figure 1, electromagnetic waves are emitted from a transmitter 1 that is elevated relative to the ground so that side lobes spread toward the ground. This forms an area in which power is concentrated near the ground where receivers such as receiver 9-1 are located.

[0026] The transmitter 1 may be any transmitter that emits an Airy beam as an electromagnetic wave that carries data or power, but here, an example of its configuration will be shown using the example of data transmission (i.e., data transmission).

[0027] 2 is a diagram showing an example of the configuration of a transmitter 1 according to an embodiment. The transmitter 1 includes a baseband signal processing unit 11, an RF unit 12, an antenna 13, a control system 14, and an Airy beam generating unit 15. Fig. 2 also shows an example of the relationship between the X-axis, the Z-axis, the origin V of the XZ coordinate system, and the transmitter 1.

[0028] The baseband signal processing unit 11 modulates a carrier wave for data transmission. As a result of the modulation, a baseband signal is obtained. The RF unit 12 converts the baseband signal to a high frequency band. The antenna 13 converts the baseband signal, which has been converted to a high frequency band signal by the RF unit 12, into an electromagnetic wave and radiates it.

[0029] Therefore, when the transmitter 1 transmits data, the antenna 13 radiates electromagnetic waves carrying the data to be transmitted. The antenna 13 may be, for example, a general horn antenna, as long as it radiates electromagnetic waves that are plane waves having a Gaussian distribution. The control system 14 is communicatively connected to the baseband signal processing unit 11 and the RF unit 12, and controls the operations of the baseband signal processing unit 11 and the RF unit 12.

[0030] The Airy beam generator 15 converts the electromagnetic waves radiated by the antenna 13 into an Airy beam. The Airy beam generator 15 may use any known technique to convert the electromagnetic waves into an Airy beam as long as it is capable of converting the electromagnetic waves into an Airy beam using a phase modulation lens and a Fourier transform lens, but the example shown in FIG. 2 will be described as an example. The Airy beam generator 15 is an example of an Airy beam generation system. The Airy beam generator 15 includes a phase modulation lens 151 and a Fourier transform lens 152.

[0031] The phase modulation lens 151 is a phase modulation lens that performs phase modulation on the electromagnetic wave radiated from the antenna 13. The phase modulation lens 151 performs phase modulation on the incident electromagnetic wave according to the position for each position in a plane perpendicular to the Z axis. Note that performing phase modulation means changing the phase. With the plane perpendicular to the Z axis defined as the XY plane and the Y axis defined as the axis perpendicular to the X and Z axes, the amount of phase change at each position in the XY plane caused by the phase modulation lens 151 (i.e., the phase distribution of the phase modulation lens 151) is expressed, for example, by the following equation (2):

[0032]

[0033] The Fourier transform lens 152 is a Fourier transform lens that performs a Fourier transform on the electromagnetic wave that has been phase-modulated by the phase modulation lens 151. The Fourier transform performed by the Fourier transform lens 152 is a process that changes the phase at each position in the XY plane by an amount expressed by, for example, the following equation (3).

[0034]

[0035] k ０ represents the wave number of the carrier wave. The distance between the Fourier transform lens 152 and the phase modulation lens 151 is the focal length f of the Fourier transform lens 152.

[0036] As a result of passing through the phase modulation lens 151 and the Fourier transform lens 152 in this order, the electromagnetic wave incident on the phase modulation lens 151 is emitted from the Fourier transform lens 152 as an Airy beam.

[0037] 3 is a diagram showing an example of the hardware configuration of the control system 14 in the embodiment. The control system 14 includes a control unit 141 including a processor 91 such as a CPU (Central Processing Unit) and a memory 92 connected by a bus, and executes a program. By executing the program, the control system 14 functions as a device or system including the control unit 141, an interface unit 142, and a storage unit 143.

[0038] More specifically, the processor 91 reads out a program stored in the storage unit 143 and stores the read program in the memory 92. The processor 91 executes the program stored in the memory 92, causing the control system 14 to function as a device or system including the control unit 141, the interface unit 142, and the storage unit 143.

[0039] The control unit 141 controls the operation of each functional unit of the transmitter 1, including, for example, the control system 14. The control unit 141 controls the operation of the baseband signal processing unit 11 and the RF unit 12 to generate an Airy beam. The control unit 141 acquires data to be transmitted from an external device, for example, via the interface unit 142. The control unit 141 controls the operation of the baseband signal processing unit 11 and the RF unit 12 so as to transmit the acquired data by an Airy beam, for example. The control unit 141 acquires information stored in, for example, the memory unit 143. The process of acquiring information stored in the memory unit 143 is specifically reading.

[0040] The interface unit 142 includes a communication interface for connecting the control system 14 to an external device. The interface unit 142 communicates with the external device via wired or wireless communication. The external device is, for example, a device that is the source of data to be transmitted. In such a case, the interface unit 142 acquires the data to be transmitted by communicating with the device that is the source of the data to be transmitted.

[0041] The interface unit 142 includes input devices such as a mouse, keyboard, and touch panel. The interface unit 142 may be configured as an interface that connects these input devices to the control system 14. In this way, the interface unit 142 accepts input of various information to the control system 14 via the input device, either wired or wireless. Note that data to be transmitted does not necessarily have to be input to a communication interface, but may also be input to an input device.

[0042] The interface unit 142 outputs various types of information. The interface unit 142 includes a display device such as a CRT (Cathode Ray Tube) display, a liquid crystal display, or an organic EL (Electro-Luminescence) display. The interface unit 142 may be configured as an interface that connects these display devices to the control system 14. The interface unit 142 outputs, for example, information input to the interface unit 142.

[0043] The storage unit 143 is configured using a computer-readable storage medium device (non-transitory computer-readable recording medium) such as a magnetic hard disk device or a semiconductor storage device. The storage unit 143 stores various information related to the transmitter 1. The storage unit 143 stores, for example, a computer program for generating an Airy beam for data transmission, which computer program controls the baseband signal processing unit 11 and the RF unit 12. The storage unit 143 stores, for example, various information generated by the operation of the control unit 141. The storage unit 143 stores, for example, information acquired by the interface unit 142.

[0044] 4 is a flowchart showing an example of a process flow executed by the wireless transmission system 100 according to the embodiment. More specifically, FIG. 4 is a flowchart showing an example of a process flow when the transmitter 1 transmits data. The transmitter 1 acquires data to be transmitted (step S101). More specifically, the control unit 141 acquires the data to be transmitted via the interface unit 142.

[0045] After step S101, the transmitter 1 emits an Airy beam for transmitting the acquired data (step S102). More specifically, the control unit 141 generates electromagnetic waves for transmitting the acquired data by controlling the operations of the baseband signal processing unit 11 and the RF unit 12, and the generated electromagnetic waves are converted into an Airy beam by the Airy beam generating unit 15 and emitted. Note that in the case of transmitting power, the processing of step S101 does not need to be executed.

[0046] Furthermore, the wireless transmission system 100 configured in this manner transmits data or power by emitting an Airy beam whose side lobes extend toward the ground. Therefore, as shown in FIG. 1, for example, radio waves do not propagate above the transmitter 1. On the other hand, as shown in FIG. 1, for example, the area in which communication with the transmitter 1 is possible extends parallel to the ground. Therefore, the wireless transmission system 100 can simultaneously reduce energy loss in wireless transmission and expand the areas in which communication is possible.

[0047] (Variation) The control unit 141 may also execute an Airy beam adjustment process. The Airy beam adjustment process is a process of executing a frequency determination process and controlling the operation of the RF unit 12 so that the Airy beam is emitted at the frequency determined by the frequency determination process. The frequency determination process is a process of determining the frequency of the Airy beam to a frequency that corresponds to the transmission environment, which is the environment for transmitting electromagnetic waves. Therefore, after executing the frequency determination process, the transmitter 1 emits an Airy beam at the frequency determined by the execution of the frequency determination process.

[0048] <First Example of Frequency Determination Process> The frequency determination process is, for example, a process (hereinafter referred to as "first type determination process") that determines the frequency of the Airy Beam to a frequency according to the position of the transmitter 1 and the position of the edge of the receiving area. The position of the transmitter 1 and the position of the edge of the receiving area are examples of the transmission environment.

[0049] The first type determination process may be any process that can determine a frequency based on the position of the transmitter 1 and the position of the edge of the receiving area. The first type determination process may be, for example, a process that uses equation (1). The first type determination process that determines a frequency using equation (1) will be described as a first example of the first type determination process.

[0050] <<First Example of First Type Determination Process>> The values ​​of the parameters X and Z in equation (1) are determined based on the position of the transmitter 1 and the position of the edge of the receiving area. Therefore, if a predetermined optical characteristic value is also used, the value of the frequency λ can be determined using equation (1).

[0051] Therefore, in the first type determination process, the control unit 141 determines the frequency of the Airy beam using equation (1) based on information indicating the position of the transmitter 1, information indicating the position of the edge of the receiving area, and predetermined optical characteristic values.

[0052] The optical characteristic values ​​are values ​​that indicate the characteristics of the phase modulation lens and the Fourier transform lens used to generate the Airy beam. Specifically, the value that indicates the characteristics of the phase modulation lens used to generate the Airy beam is the value b that determines the phase distribution of the phase modulation lens. Specifically, the value that indicates the characteristics of the Fourier transform lens used to generate the Airy beam is the focal length f of the Fourier transform lens.

[0053] The information indicating the position of the receiving area end may be input by the user via the interface unit 142, or may be input by an external device via the interface unit 142. Alternatively, the information may be information indicating a position that the control unit 141 has acquired as the position of the receiving area end in accordance with a predetermined rule.

[0054] The information indicating the position of the transmitter 1 may be input by the user via the interface unit 142, or may be input by an external device via the interface unit 142. Alternatively, the information may be information indicating a position acquired by the control unit 141 as the position of the edge of the receiving area in accordance with a predetermined rule.

[0055] Either the information indicating the position of the transmitter 1 or the information indicating the position of the edge of the receiving area may be predetermined. The control unit 141 may obtain the information indicating the position of the transmitter 1 and the information indicating the position of the edge of the receiving area by, for example, a global positioning system (GPS).

[0056] The information indicating the position of the transmitter 1 may include, for example, the height of the transmitter 1 from the ground.

[0057] <<Second Example of First Type Determination Process>> The first type determination process may be, for example, a process of determining the frequency of the Airy Beam using tabular data indicating a predetermined correspondence between the relative positional relationship between the transmitter 1 and the edge of the receiving area and the frequency. The correspondence between the relative positional relationship between the transmitter 1 and the edge of the receiving area and the frequency indicated in the tabular data may be obtained in advance using, for example, equation (1), may be based on experience, or may be obtained by simulation.

[0058] <Second Example of Frequency Determination Process> The transmitter 1 may transmit a plurality of known signals with different frequencies at a predetermined timing, and receive information indicating the SNR (Signal-to-Noise Ratio) measured by a receiver that receives the signals (hereinafter referred to as "SNR information"). In this case, the signals in the SNR are known signals. The known signals are also known signals. In other words, when the transmitter 1 transmits a plurality of known signals with different frequencies at a predetermined timing, and the receiver that receives the known signals measures the SNR, which represents the ratio of the known signals to noise, the transmitter 1 may receive SNR information, which is information indicating the result of the measurement.

[0059] In such a case, the frequency determination process may be a process of determining a frequency at which the SNR is maximized based on SNR information. The predetermined timing may be any predetermined timing, for example, a predetermined periodic timing. The SNR is an example of a transmission environment.

[0060] FIG. 5 is an explanatory diagram illustrating a wireless transmission system 100a according to a modified example. The wireless transmission system 100a differs from the wireless transmission system 100 in that it includes a transmitter 1a instead of the transmitter 1. The transmitter 1a emits a narrow beam to an area not reached by the Airy beam. Therefore, the transmitter 1 emits a narrow beam in addition to the Airy beam. In FIG. 5, beam B1 is an example of a narrow beam emitted by the transmitter 1. Reference numeral 99 in FIG. 5 is an example of a mobile object moving in the air not reached by the Airy beam, such as a drone.

[0061] FIG. 6 is a diagram showing an example of the configuration of a transmitter 1a in a modified example. For ease of explanation, components similar to those in the transmitter 1 are given the same reference numerals and will not be described again. The transmitter 1a differs from the transmitter 1 in that it further includes a narrow beam antenna 16. The narrow beam antenna 16 is an antenna that generates a narrow beam. The narrow beam antenna 16 is, for example, an array antenna. The beam emitted from the narrow beam antenna 16 is a narrow beam such as beam B1 in FIG. 5. The operation of the narrow beam antenna 16 is controlled by a control unit 141.

[0062] In this way, the wireless transmission system 100a can form a separate receiving area in an area where there is no interference from the Airy beam. If the transmitter 1 were to emit a narrow beam instead of an Airy beam, multiple beams would interfere with the receiving area formed by the narrow beam emitted from the narrow beam antenna 16. On the other hand, if an Airy beam is emitted instead, there is no interference, as shown in Figure 5. Therefore, communication and power transmission can be performed in an environment with less noise.

[0063] The control system 14 may be implemented using a plurality of information processing devices connected to each other via a network so that they can communicate with each other. In this case, the processes executed by the control unit 141 may be distributed among the plurality of information processing devices.

[0064] The transmitter 1 and the transmitter 1a are both examples of a transmitting device.

[0065] Note that all or part of the functions of the baseband signal processing unit 11 and the control system 14 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. The program may be transmitted via a telecommunications line.

[0066] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0067] REFERENCE SIGNS LIST 100, 100a...wireless transmission system, 1, 1a...transmitter, 11...baseband signal processing unit, 12...RF unit, 13...antenna, 14...control system, 15...Airy beam generating unit, 16...narrow beam antenna, 151...phase modulation lens, 152...Fourier transform lens, 141...control unit, 142...interface unit, 143...storage unit, 91...processor, 92...memory

Claims

1. A wireless transmission system comprising: a transmitter that radiates electromagnetic waves, the electromagnetic waves being an Airy beam that propagates in a direction parallel to the ground with side lobes spreading.

2. The wireless transmission system according to claim 1, wherein the transmitter further emits a narrow beam in an area not reached by the Airy beam.

3. A wireless transmission system as described in claim 1 or 2, wherein the transmitter executes a frequency determination process to determine the frequency of the Airy Beam to a frequency according to the transmission environment, and then emits an Airy Beam of the frequency determined by executing the frequency determination process.

4. A wireless transmission system as described in claim 3, wherein the frequency determination process is a process of determining the frequency of the Airy beam to a frequency depending on the position of the transmitter and the position of the edge of the receiving area.

5. A wireless transmission system as described in claim 3, wherein when the transmitter transmits a plurality of known signals of different frequencies at a predetermined timing and the receiver receives the known signals and measures an SNR representing a ratio of the known signals to noise, the frequency determination process is a process of determining a frequency at which the SNR is maximized based on a result of the measurement.

6. A wireless transmission system as described in claim 3, wherein the frequency determination process is a process of determining the frequency of the Airy Beam using tabular data showing a predetermined correspondence between the relative positional relationship between the transmitter 1 and the edge of the receiving area and the frequency.

7. A wireless transmission method implemented by a wireless transmission system comprising a transmitter that radiates electromagnetic waves, the electromagnetic waves being Airy beams that propagate with side lobes spreading in a direction parallel to the ground, the wireless transmission method including an emission step in which the transmitter emits the Airy beam.

8. A transmitting device comprising an optical system for converting an electromagnetic wave into an Airy beam, the Airy beam propagating in such a way that side lobes spread in a direction parallel to the ground.

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