System, specific device, program, and member

Abstract

SOLUTION: There is provided an identification device comprising: a storage unit for storing delay time-incident angle relationship data indicating a relationship between a delay time till a radio wave transmitted from a transmission antenna located in a housing reaches a reception antenna located inside the housing, in a state where a reflector is located in an open section of the housing which is at least partly open and has an inner surface at least a part of which reflects the radio wave, and an incident angle of when the radio wave enters the reflector; an analysis result acquisition unit for acquiring an analysis result in which the radio wave transmitted from the transmission antenna and received by the reception antenna in a state where a measurement object is located in the open part of the housing; and a reflection characteristic identification unit for identifying reflection characteristic of the radio wave of measurement object on the basis of the analysis result and the delay time-incident angle relationship data.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a system, a specific device, a program, and a member.

Background Art

[0002] Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3 describe a method for measuring the reflection characteristics of materials. [Prior Art Documents] [Non-Patent Documents] [Non-Patent Document 1] Takayuki Sasamori, Basics and Applications of Antenna Measurements Using a Network Analyzer, Workshop on Design and Analysis Methods in Antennas and Propagation (54th), Antenna and Propagation Research Special Committee, 2016.6 [Non-Patent Document 2] Yuto Kato, "Investigation and Research on Measurement Techniques and Standard Supply of Material Constants such as Dielectric Constant," NMIJ Report, vol.9, no.4, pp.99-116, 2014. [Non-Patent Document 3] Keysight Technologies, "Basics of Agilent Dielectric Measurements," Application note, 5989-2589JA, 2014.

Summary of the Invention

Means for Solving the Problems

[0003] According to an embodiment of the present invention, a system is provided. The system may include a housing having an inner surface at least partially open and at least partially reflecting radio waves. The system may include a transmitting antenna disposed within the housing. The system may include a receiving antenna disposed within the housing. The system may include a reflection characteristic specifying unit that specifies the radio wave reflection characteristics of the measurement target based on radio waves transmitted from the transmitting antenna and received by the receiving antenna in a state where the measurement target is disposed at the open portion of the housing.

[0004] In the above system, the housing may be a polyhedron having a plurality of faces with at least one side open, and the inner surfaces of two or more of the plurality of faces may be radio wave reflecting surfaces. The housing may be a rectangular parallelepiped having one side open, a first face, a second face facing the first face, a third face, a fourth face facing the third face, and a fifth face facing the open side, and the inner surfaces of the first face and the second face may be radio wave reflecting surfaces, and the inner surfaces of the third face and the fourth face may be radio wave absorbing surfaces. The inner surface of the fifth face may be a radio wave absorbing surface.

[0005] In any of the above systems, the distance between the first face and the second face may be configured to be changeable.

[0006] In any of the above systems, the housing may be a rectangular parallelepiped having one side open, a first face, a second face, a third face facing the first face, a fourth face facing the second face, and a fifth face facing the open side, and the first face, the second face, the third face, and the fourth face may be configured to be switchable between a state in which the first face and the second face are radio wave reflecting surfaces and the third face and the fourth face are radio wave absorbing surfaces, and a state in which the first face and the second face are radio wave absorbing surfaces and the third face and the fourth face are radio wave reflecting surfaces.

[0007] In any of the above systems, the reflection characteristic specifying unit may specify the reflection characteristics of the measurement target by using delay time-incidence angle relationship data indicating the relationship between the delay time from when the radio wave transmitted from the transmission antenna is reflected by a reflector disposed in the open portion of the housing until it reaches the reception antenna and the incidence angle when the radio wave is incident on the reflector. The reflection characteristic specifying unit may specify the reflection characteristics of the measurement target by using the reception level for each time of the radio wave transmitted from the transmission antenna and received by the reception antenna in a state where a reflector having a known reflection coefficient is disposed in the open portion of the housing, the reception level for each time of the radio wave transmitted from the transmission antenna and received by the reception antenna in a state where the measurement target is disposed in the open portion of the housing, and the delay time-incidence angle relationship data.

[0008] In any of the above systems, the transmission antenna and the reception antenna may be arranged in the housing without being aligned.

[0009] According to an embodiment of the present invention, a specifying device is provided. The specifying device may include a storage unit that stores delay time-incidence angle relationship data indicating the relationship between the delay time from when the radio wave transmitted from a transmission antenna disposed in the housing is reflected by a reflector disposed in the open portion of the housing having an inner surface that is at least partially open and at least partially reflects radio waves until it reaches a reception antenna disposed in the housing and the incidence angle when the radio wave is incident on the reflector. The specifying device may include an analysis result acquisition unit that acquires an analysis result obtained by analyzing the radio wave transmitted from the transmission antenna and received by the reception antenna in a state where the measurement target is disposed in the open portion of the housing. The specifying device may include a reflection characteristic specifying unit that specifies the reflection characteristics of the radio wave of the measurement target based on the analysis result and the delay time-incidence angle relationship data.

[0010] According to an embodiment of the present invention, a program for causing a computer to function as the above specifying device is provided.

[0011] According to an embodiment of the present invention, a member is provided. The member may include a housing having an inner surface that is at least partially open and at least partially reflects radio waves. The member may include a transmission antenna disposed within the housing. The member may include a reception antenna disposed within the housing.

[0012] Note that the above summary of the invention does not list all the necessary features of the present invention. Also, sub-combinations of these feature groups can also be inventions.

Brief Description of the Drawings

[0013]

Figure 1

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Best Mode for Carrying Out the Invention

[0014] Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential for the solution means of the invention.

[0015] In next-generation mobile communications, it is being considered to use the high-frequency band (30 to 300 GHz) of the millimeter-wave band. However, in this band, since the medium characteristics of the material are not clear, in simulations, it is necessary to substitute with medium constants of 100 GHz or less. Alternatively, the user has no choice but to use an estimated value calculated from his or her own experimental values. On the other hand, even if the medium constant can be specified for the reflection characteristics in the millimeter-wave band, the reflection itself has strong elements of diffuse scattering and is not necessarily applicable as it is. In such a situation, the inventor considered an approach that emphasizes experimental values, but it is difficult to efficiently measure the reflection and scattering characteristics of materials. There is also a method using an angle setting arm for measuring the angular characteristics of specular reflection, but mechanical setting and scanning are required, and it takes a huge amount of measurement time. Therefore, in view of the above problems, a simultaneous measurement method of angular characteristics using a plurality of mirror image wave sources was considered as a method that does not require angular scanning in principle. As a specific example, in the system 10 according to the present embodiment, a delay profile is obtained from the transmission characteristics of a transmit-receive omnidirectional antenna installed in an anechoic chamber, and the incident angle is calculated from the delay time to simultaneously measure the incident angle dependence of the reflection characteristics. As a result, mechanical scanning and setting for setting the incident angle are not required in principle, and there is a possibility that high-speed measurement can be realized.

[0016] FIG. 1, FIG. 2, and FIG. 3 are explanatory diagrams for explaining the system 10. The system 10 includes a member 100 and a specific device 300. The system 10 may include an analyzer 200.

[0017] The member 100 includes a housing 110, a transmission antenna 150 disposed within the housing 110, and a reception antenna 160 disposed within the housing 110. At least a part of the housing 110 is open, and it has an inner surface that reflects radio waves at least in part.

[0018] In this embodiment, the case where the housing 110 is a rectangular parallelepiped will be mainly taken as an example for explanation, but the housing 110 is not limited to a rectangular parallelepiped. As shown in FIG. 2, in this embodiment, for the sake of explanation, each surface of the housing 110 is described as the east, west, south, north (E, W, S, N), ceiling (C), and floor (F), namely, the E surface 111, the W surface 112, the C surface 113, the F surface 114, the S surface 115, and the N surface 116. In this example, the N surface 116 is the open surface. That is, the side of the N surface 116 is open. Also, the transmission antenna 150 and the reception antenna 160 are connected to the analyzer 200 by wiring that penetrates the F surface 114. The transmission antenna 150 and the reception antenna 160 may be connected to the analyzer 200 by wiring that penetrates other surfaces.

[0019] As shown in FIG. 3, a measurement target 20, which is an object to be measured for the radio wave reflection characteristics, is disposed at the open portion of the housing 110. The measurement target 20 may be any object. The measurement target 20 has a planar portion disposed at the open portion of the housing 110. The entire measurement target 20 may be planar in shape.

[0020] The inner surfaces of the surfaces of the housing 110 other than the open portion may be selected from a total reflection surface, a radio wave absorption surface, and an open surface as appropriate. In the examples shown in FIGS. 1 to 3, the inner surfaces of the E surface 111, the W surface 112, and the S surface 115 are total reflection surfaces, and the inner surfaces of the C surface 113 and the F surface 114 are radio wave absorption surfaces. In this example, the housing 110 forms a closed system when the measurement target 20 is disposed on the N surface 116. Note that the housing 110 may have other surfaces than the N surface 116 open. For example, in addition to the N surface 116, the S surface 115 may be open. Also, for example, in addition to the N surface 116, the C surface 113 and the F surface 114 may be open. Also, for example, in addition to the N surface 116, the E surface 111 and the W surface 112 may be open.

[0021] The transmission antenna 150 and the reception antenna 160 disposed within the housing 110 are connected to the analyzer 200. The antenna directivity of the transmission antenna 150 and the reception antenna 160 may be omnidirectional.

[0022] The analyzer 200 has a function of measuring the reception level of the radio wave received by the reception antenna 160 for each time. The analyzer 200 may be a VNA (Vector Network Analyzer). The analyzer 200 may have a so-called time domain function.

[0023] The analyzer 200 analyzes the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160 in a state where the measurement object 20 is disposed on the N surface 116 of the housing 110, and provides the analysis result to the specifying device 300. The analyzer 200 may analyze the radio wave in the millimeter wave band transmitted from the transmission antenna 150 and received by the reception antenna 160, and provide the analysis result to the specifying device 300.

[0024] The specifying device 300 specifies the reflection characteristics of the measurement object 20 based on the analysis result acquired from the analyzer 200. Here, the case where the analyzer 200 and the specifying device 300 are separate bodies is illustrated, but the present invention is not limited thereto, and the analyzer 200 and the specifying device 300 may be integrated. That is, the specifying device 300 may have the function of the analyzer 200.

[0025] A method for specifying the reflection characteristics of the measurement object 20 by the specifying device 300 will be described by taking as an example the case where the member 100 illustrated in FIGS. 1 to 3 is used.

[0026] FIG. 4 schematically shows an example of the mirror image space 302 realized by the housing 110. Since the housing 110 is a rectangular parallelepiped, the two-dimensional mirror image space viewed from the +z-axis direction is like the mirror image space 302 shown in FIG. 4. (0, 0), etc. in the figure are the IDs of the mirror image space and represent the mirror image order on the x-plane and y-plane. The mirror image order corresponds to the number of reflections. For example, in the case of two reflections, it is 2. The origin o in the figure is set to the real space (0, 0), and the negative direction of each axis coordinate is represented by a minus sign. In the example shown in FIG. 4, the x-axis is ±2nd order and the y-axis is ±3rd order, representing a total of 35 mirror image spaces. The solid white circles indicating the transmission sources are arranged one by one in each mirror image space. As a function of the dashed white circles indicating the receiving antennas, they exist only in the real space (0, 0), but obstacles that block the paths from each mirror image source exist in each mirror image space. In principle, since there are an infinite number of mirror image sources, it is desirable to limit the target range to a finite distance. In this example, it is limited up to the distance of the long delay cut 304. The system 10 may perform such a limitation by using the time gate function of the analyzer 200.

[0027] In the mirror image space 302, the thick black line indicates the reflection surface of the measurement target 20. As shown in FIG. 4, in the x-axis direction, the reflection surface appears every two spaces. In the mirror image space 302, there are two layers of the non-measured surface 0-reflection layer ((-1, y), (0, y)) and three layers of the non-measured surface 1-reflection layer ((-2, y), (1, y), and (2, y)) with respect to the reflection surface of the measurement target 20. In FIG. 4, the mirror image space corresponding to the 2-reflection of the non-measured surface is not shown. In this example, there are 14 wave sources for the 0-reflection of the non-measured surface and 21 wave sources for the 1-reflection of the non-measured surface. In the mirror image space 302, if there is one reflection surface of the measurement target 20 in the path between the mirror image source and the receiving antenna (shown by a dashed line in FIG. 4), there is a loss corresponding to one reflection, if there are two, there is a loss corresponding to two reflections, and if there are n, there is a loss corresponding to n reflections. On the other hand, for the other surfaces, since they are total reflection surfaces, the reflection coefficient is 1 and there is no loss due to reflection. Therefore, in the 0-reflection layer, the received level (S 21 ) is equivalent to the free space radio wave loss, and in the n-reflection layer, it is received with a loss corresponding to the reflection coefficient according to the number of times.

[0028] FIG. 5 shows an example of the delay profile 400. In FIG. 5, the vertical axis represents the reception level, and the horizontal axis represents time. The delay profile 400 shows the reception level of the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160 in a state where a perfect reflector with a reflection coefficient of 1 is arranged on the N plane 116. That is, the delay profile 400 shows the reception level for each delay time from when the transmission antenna 150 transmits the radio wave until the reception antenna 160 receives it. The delay time reception level characteristic 401 shows the relationship between the delay time and the reception level.

[0029] The longer the path from when the transmission antenna 150 transmits the radio wave until the reception antenna 160 receives it, the greater the delay time. That is, there is a dependency relationship between the path and the delay time. Therefore, the path can be specified by the delay time. If the path is specified, the incident angle when the radio wave is incident on the measurement target 20 can be specified. That is, the incident angle can be specified by the delay time. The specifying device 300 may store in advance the delay time incident angle relationship data showing the relationship between the delay time and the incident angle, and the delay profile 400.

[0030] FIG. 6 shows the reflection coefficient incident angle characteristic 410. In FIG. 6, the vertical axis represents the reflection coefficient, and the horizontal axis represents the incident angle. The reflection coefficient incident angle characteristic 410 is specified with total reflection (reflection coefficient 1) as the reference value. The specifying device 300 may store in advance the reflection coefficient incident angle characteristic 410.

[0031] FIGS. 7 and 8 show an example of the delay profile 500. The delay profile 500 illustrated in FIG. 7 shows the delay time reception level characteristic 401, and the profiles of two layers (solid line) of the 0 - reflection layer ((-1, y), (0, y)) of the surface to be measured, the 1 - reflection layer ((1, y)) (dashed line) of the surface to be measured, and the 2 - reflection layer (3, y) (dash - dotted line) of the surface to be measured. When the long - delay cut 304 is applied, the long - delay cut 502 shown in FIGS. 7 and 8 will be applied.

[0032] As shown in FIG. 8, the specific device 300 calculates the reflection coefficient for each delay time based on the level difference with respect to the delay time reception level characteristic 401. The specific device 300 specifies the characteristic between the reflection coefficient and the incident angle from the calculation result and the delay time incident angle relationship data.

[0033] FIG. 9 schematically shows an example of the reflection coefficient incident angle characteristic 600. In the system 10 according to the present embodiment, by changing the position of at least one of the transmission antenna 150 and the reception antenna 160, or by changing the position of the reflecting surface without changing the positions of the transmission antenna 150 and the reception antenna 160, the path of the radio wave from the transmission antenna 150 to the reception antenna 160 can be changed, and the reflection coefficients for different incident angles can be specified. FIG. 9 shows the case where the position of the reception antenna 160 is changed to generate the delay profile three times (#1, #2, #3). Further, in the system 10 according to the present embodiment, by changing the orientation of at least one of the transmission antenna 150 and the reception antenna 160 to change the polarization, the characteristics of both TE incidence and TM incidence can be specified.

[0034] The measurement of the reflection characteristics of materials is classified into direct and indirect methods. In the direct method, the reflection characteristics for each incident angle are directly measured using a device that varies the angles of two antennas for transmission and reception. A method of generating a plane wave using a lens or the like is used so that radio waves are appropriately incident on the reflecting surface. Since mechanical angle scanning is required, the measurement time is long and the work is complicated. Therefore, it is difficult to say that it is a method that can be easily measured. On the other hand, in the indirect method, the reflection characteristics are obtained indirectly by measuring the electrical constants such as the dielectric constant of the material sample and substituting it into the Fresnel reflection coefficient. This includes methods of transmitting a plane wave to determine the material constants, methods of filling materials in coaxial lines and waveguides, etc. In the millimeter wave band, since it is known that the roughness of the reflecting surface greatly affects the reflection characteristics, it is desirable to measure the actual materials such as walls and ground objects by the direct method. In the system 10 according to the present embodiment, as described above, an omnidirectional antenna is used to generate reflected waves in multiple directions, and the reflection coefficient incident angle characteristics are specified from the delay time, and the reflection characteristics of the measurement target 20 can be specified very efficiently. Further, in the system 10 according to the present embodiment, by bringing the member 100 into contact with the actual material such as a wall or a ground object for which the reflection characteristics are to be measured, the measurement environment is improved. Therefore, it is possible to eliminate the need to cut out materials for measurement or prepare materials with adjusted sizes for measurement, and the measurement can be made more efficient.

[0035] FIG. 10 schematically shows an example of the functional configuration of the specifying device 300. The specifying device 300 shown in FIG. 10 includes a registration unit 312, a storage unit 314, an analysis unit 316, an analysis result acquisition unit 318, and a reflection characteristic specifying unit 320. Here, the case where the specifying device 300 has the functions of the analysis device 200 is shown, but when the specifying device 300 does not have the functions of the analysis device 200, the specifying device 300 does not have the analysis unit 316, and the analysis device 200 may have the analysis unit 316.

[0036] The member 100 has a housing 110 that is at least partially open and has an inner surface that reflects radio waves at least partially, a transmission antenna 150 disposed in the housing 110, and a reception antenna 160 disposed in the housing 110.

[0037] The housing 110 may be a polyhedron having a plurality of faces with at least one side open. Among the plurality of faces excluding the open face, the inner surface of one or more faces may be a radio wave reflecting surface. Among the plurality of faces excluding the open face, the inner surfaces of two or more faces may be radio wave reflecting surfaces. Among the plurality of faces excluding the open face, the inner surface of the face other than the face whose inner surface is a radio wave reflecting surface may be a radio wave absorbing surface. The inner surfaces of all of the plurality of faces excluding the open face may be radio wave reflecting surfaces.

[0038] The housing 110 may be, for example, a hexahedron, and one or more of the six faces may be open. For example, the housing 110 is a rectangular parallelepiped.

[0039] As a specific example, the housing 110 has one side open and is a rectangular parallelepiped having a first face, a second face facing the first face, a third face, a fourth face facing the third face, and a fifth face facing the open side. In the example shown in FIG. 2, the E-plane 111 may be the first face, the W-plane 112 may be the second face, the C-plane 113 may be the third face, the F-plane 114 may be the fourth face, and the S-plane 115 may be the fifth face.

[0040] Among the first face, the second face, the third face, the fourth face, and the fifth face, the inner surfaces of two faces may be radio wave reflecting surfaces and the inner surfaces of three faces may be radio wave absorbing surfaces. For example, the inner surfaces of the first face and the second face may be radio wave reflecting surfaces, and the inner surfaces of the third face, the fourth face, and the fifth face may be radio wave absorbing surfaces. For example, the inner surfaces of the third face and the fourth face may be radio wave reflecting surfaces, and the inner surfaces of the first face, the second face, and the fifth face may be radio wave absorbing surfaces.

[0041] Among the first face, the second face, the third face, the fourth face, and the fifth face, the inner surfaces of three faces may be radio wave reflecting surfaces and the inner surfaces of two faces may be radio wave absorbing surfaces. For example, the inner surfaces of the first face, the second face, and the fifth face may be radio wave reflecting surfaces, and the inner surfaces of the third face and the fourth face may be radio wave absorbing surfaces. For example, the inner surfaces of the third face, the fourth face, and the fifth face may be radio wave reflecting surfaces, and the inner surfaces of the first face and the second face may be radio wave absorbing surfaces.

[0042] Of the first surface, the second surface, the third surface, the fourth surface, and the fifth surface, the inner surfaces of four surfaces may be radio wave reflecting surfaces and the inner surface of one surface may be a radio wave absorbing surface. The inner surfaces of all of the first surface, the second surface, the third surface, the fourth surface, and the fifth surface may be radio wave reflecting surfaces.

[0043] In the example shown in FIG. 2, the C surface 113 may be the first surface, the F surface 114 may be the second surface, the E surface 111 may be the third surface, the W surface 112 may be the fourth surface, and the S surface 115 may be the fifth surface.

[0044] As another example, the housing 110 has two open sides and is a rectangular parallelepiped having a first surface, a second surface facing the first surface, a third surface, and a fourth surface facing the third surface. In the example shown in FIG. 2, in addition to the N surface 116, the S surface 115 may be an open surface, the E surface 111 may be the first surface, the W surface 112 may be the second surface, the C surface 113 may be the third surface, and the F surface 114 may be the fourth surface.

[0045] Of the first surface, the second surface, the third surface, and the fourth surface, two surfaces may be radio wave reflecting surfaces and two surfaces may be radio wave absorbing surfaces. For example, the first surface and the second surface may be radio wave reflecting surfaces and the third surface and the fourth surface may be radio wave absorbing surfaces. For example, the third surface and the fourth surface may be radio wave reflecting surfaces and the first surface and the second surface may be radio wave absorbing surfaces.

[0046] Of the first surface, the second surface, the third surface, and the fourth surface, three surfaces may be radio wave reflecting surfaces and one surface may be a radio wave absorbing surface. The inner surfaces of all of the first surface, the second surface, the third surface, and the fourth surface may be radio wave reflecting surfaces.

[0047] The housing 110 is, for example, a heptahedron and one or more of the seven surfaces may be open. The housing 110 may be a polyhedron having eight or more surfaces and one or more of the eight surfaces being open.

[0048] The housing 110 may be configured such that the distance between the surfaces can be changed. In particular, the housing 110 may be configured such that the distance between the surface whose inner surface is a reflective surface and another surface can be changed. As a specific example, when the inner surfaces of the first surface and the second surface are radio wave reflective surfaces and the inner surfaces of the third surface, the fourth surface, and the fifth surface are radio wave absorbing surfaces, the distance between the first surface and the second surface is configured to be changeable. The housing 110 may be configured such that the distance between the surfaces can be changed, for example, by having a slide structure. Note that the housing 110 is not limited to a slide structure and may have other structures as long as the distance between the surfaces can be changed. By configuring the housing 110 such that the distance between the surfaces can be changed, the variations in the reflection environment can be easily increased, and the measurement efficiency can be improved.

[0049] For each of the inner surfaces of a plurality of surfaces of the housing 110 excluding the open surface, it may be configured to be switchable between a state where it is a radio wave reflective surface and a state where it is a radio wave absorbing surface. As a specific example, the first surface, the second surface, the third surface, and the fourth surface are configured to be switchable between a state where the first surface and the second surface are radio wave reflective surfaces and the third surface and the fourth surface are radio wave absorbing surfaces, and a state where the first surface and the second surface are radio wave absorbing surfaces and the third surface and the fourth surface are radio wave reflective surfaces. For example, the housing 110 has a structure that allows the inner surfaces of a plurality of surfaces excluding the open surface to be radio wave absorbing surfaces and allows a radio wave reflective surface to be attached to and detached from the inner surfaces. The attachment and detachment of the radio wave reflective surface may be realized by magnetic force or may be realized by an adhesive or the like. Also, for example, the housing 110 has a structure that allows the inner surfaces of a plurality of surfaces excluding the open surface to be radio wave reflective surfaces and allows a radio wave absorbing surface to be attached to and detached from the inner surfaces. The attachment and detachment of the radio wave absorbing surface may be realized by magnetic force or may be realized by an adhesive or the like. By configuring the housing 110 in this way, the number of reflection paths can be increased, the polarization can be changed, and thereby the variations in the reflection environment can be increased, and the measurement efficiency can be improved.

[0050] The housing 110 may be a sphere or an ellipsoid with at least a part thereof being open and having an inner surface that reflects radio waves at least in part. The housing 110 may have, for example, the shape of a spherical segment formed by cutting a hollow sphere with a plane. Part or a plurality of parts of the inner surface of the housing 110 may be a radio wave reflecting surface, and other parts may be a radio wave absorbing surface.

[0051] The transmitting antenna 150 and the receiving antenna 160 may be arranged in the housing 110 without being aligned. The transmitting antenna 150 and the receiving antenna 160 may be arranged, for example, such that they do not have a positional relationship that is symmetric with respect to the center of gravity of the housing 110. When the transmitting antenna 150 and the receiving antenna 160 are arranged in alignment within the housing 110, the incident angle on the measurement target 20 in the radio wave path including the reflection from the transmitting antenna to the receiving antenna at the measurement target 20 will increase the pattern in which the delay time remains the same despite being different, resulting in a reduction in effective data. On the other hand, by arranging the transmitting antenna 150 and the receiving antenna 160 without alignment within the housing 110, such a pattern can be reduced and the effective data can be increased.

[0052] At least one of the transmitting antenna 150 and the receiving antenna 160 may be arranged such that its position can be changed within the housing 110. Both the transmitting antenna 150 and the receiving antenna 160 may be arranged such that their positions can be changed within the housing 110, or only one of the transmitting antenna 150 and the receiving antenna 160 may be arranged such that its position can be changed within the housing 110.

[0053] The registration unit 312 registers delay time incident angle relationship data indicating the relationship between the delay time from when the radio wave transmitted from the transmitting antenna 150 arranged within the housing 110 of the member 100 is reflected by a reflector arranged at the open part of the housing 110 until it reaches the receiving antenna 160 and the incident angle when the radio wave is incident on the reflector. The delay time incident angle relationship data registered by the registration unit 312 is stored in the storage unit 314.

[0054] When there are a plurality of members 100, the registration unit 312 may register delay time incident angle relationship data for each of the plurality of members 100.

[0055] When the distance between the surfaces of the housing 110 of the member 100 is configured to be changeable, the relationship between the delay time and the incident angle will change depending on the distance between the surfaces. When the distance between the surfaces of the housing 110 of the member 100 is configured to be changeable, the registration unit 312 may register delay time incident angle relationship data for each distance between the surfaces.

[0056] For each of the inner surfaces of the plurality of surfaces of the housing 110 of the member 100 excluding the open surfaces, when the state of being a radio wave reflecting surface and the state of being a radio wave absorbing surface are configured to be switchable, the relationship between the delay time and the incident angle will change for each combination of the radio wave reflecting surface and the radio wave absorbing surface of the inner surfaces of the plurality of surfaces. When, for each of the inner surfaces of the plurality of surfaces of the housing 110 of the member 100 excluding the open surfaces, the state of being a radio wave reflecting surface and the state of being a radio wave absorbing surface are configured to be switchable, the registration unit 312 may register delay time incident angle relationship data for each combination of the radio wave reflecting surface and the radio wave absorbing surface of the inner surfaces of the plurality of surfaces.

[0057] When at least one of the transmission antenna 150 and the reception antenna 160 can be repositioned within the housing 110, the relationship between the delay time and the incident angle will change depending on the position. When at least one of the transmission antenna 150 and the reception antenna 160 can be repositioned within the housing 110, the registration unit 312 may register delay time incident angle relationship data for each position.

[0058] The analysis unit 316 analyzes the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160. The analysis unit 316 may have a so-called time domain function. The analysis unit 316 may specify the reception level of the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160 at each time. The analysis unit 316 may have a so-called time gate function. The analysis unit 316 may target only a time range shorter than a predetermined time.

[0059] The analysis unit 316 may specify the reception level for each time of the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160 in a state where a reflector with a known reflection coefficient is arranged at the open portion of the housing 110 of the member 100. When there are a plurality of open portions of the housing 110, the reflector is arranged for only any one of the plurality of open portions. The analysis unit 316 specifies, for example, the reception level for each time of the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160 in a state where a total reflector with a reflection coefficient of 1 is arranged at the open portion of the housing 110 of the member 100.

[0060] The analysis unit 316 may specify the reception level for each time of the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160 in a state where the measurement target 20 is arranged at the open portion of the housing 110 of the member 100. When there are a plurality of open portions of the housing 110, the measurement target 20 is arranged for only any one of the plurality of open portions.

[0061] The analysis result acquisition unit 318 acquires the analysis result by the analysis unit 316 from the analysis unit 316. The analysis result acquisition unit 318 acquires, for example, the reception level for each time of the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160 in a state where a reflector with a known reflection coefficient is arranged at the open portion of the housing 110 of the member 100. The analysis result acquisition unit 318 acquires, for example, the reception level for each time of the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160 in a state where the measurement target 20 is arranged at the open portion of the housing 110 of the member 100.

[0062] The reflection characteristic specifying unit 320 specifies the radio wave reflection characteristics of the measurement target 20 based on the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160 in a state where the measurement target 20 is arranged in the open portion of the housing 110 of the member 100. The reflection characteristic specifying unit 320 specifies the reflection characteristics of the measurement target 20 using the delay time incident angle relationship data corresponding to the used member 100.

[0063] The reflection characteristic specifying unit 320 may specify the reflection characteristics of the measurement target 20 using the reception level for each time of the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160 in a state where a total reflector is arranged in the open portion of the housing 110, the reception level for each time of the radio wave transmitted from the transmission antenna 150 and received by the reception antenna 160 in a state where the measurement target 20 is arranged in the open portion of the housing 110, and the delay time incident angle data. Specifically, the reflection characteristic specifying unit 320 calculates the reflection coefficient of the measurement target 20 from the level difference of the reception levels for each delay time. Then, the reflection characteristic specifying unit 320 specifies the reflection coefficient for each incident angle using the delay time incident angle data.

[0064] Thereby, for the measurement target 20, the reflection coefficients for each of a plurality of incident angles can be specified without changing the positions of the transmission antenna 150 and the reception antenna 160, and the reflection characteristics of the measurement target 20 can be efficiently specified. In particular, when targeting the millimeter wave band, the positions of the transmission antenna 150 and the reception antenna 160 require very high accuracy, and the specific method of moving the transmission antenna 150 and the reception antenna 160 becomes highly difficult. Therefore, the specific method of this system that can specify the reflection coefficients for each of a plurality of incident angles of the measurement target 20 without moving the transmission antenna 150 and the reception antenna 160 can be said to be more effective.

[0065] When the distance between the surfaces of the housing 110 of the member 100 is configured to be changeable, the reflection characteristic specifying unit 320 specifies the reflection coefficient for each of a plurality of incident angles for each distance between the surfaces, using the delay time - incident angle relationship data registered for each distance between the surfaces. As a result, it is possible to specify the reflection coefficients for a large number of incident angles, and it is possible to more efficiently specify the reflection characteristics of the measurement object 20.

[0066] When, for each of the inner surfaces of a plurality of surfaces of the housing 110 of the member 100, excluding the open surfaces, the state of being a radio wave reflecting surface and the state of being a radio wave absorbing surface are configured to be switchable, the reflection characteristic specifying unit 320 specifies the reflection coefficient for each of a plurality of incident angles for each combination of the radio wave reflecting surface and the radio wave absorbing surface of the inner surfaces of the plurality of surfaces, using the delay time - incident angle relationship data registered for each combination of the radio wave reflecting surface and the radio wave absorbing surface of the inner surfaces of the plurality of surfaces. Also by this, it is possible to specify the reflection coefficients for a large number of incident angles, and it is possible to more efficiently specify the reflection characteristics of the measurement object 20.

[0067] In the measurement in the system 10, radio waves of different frequencies may be transmitted from the transmission antenna 150, and the reflection characteristics of the measurement object 20 may be specified for each different frequency. The analysis unit 316 causes, for example, the transmission antenna 150 to transmit radio waves while performing frequency sweeping. The analysis unit 316 may also cause the transmission antenna 150 to sequentially transmit pulse waves of different frequencies. The reflection characteristic specifying unit 320 may specify the reflection characteristics, that is, the reflection coefficient - incident angle characteristics, for each different frequency from the analysis result by the analysis unit 316. As a result, it is possible to efficiently specify the reflection characteristics of the measurement object 20 for each frequency. According to the experiment conducted by the inventor, in the 30 GHz to 100 GHz band, no difference was observed in the reflection characteristics, but a frequency dependency peculiar to the 300 GHz band was observed, in which the reflection coefficient becomes low when it reaches the 300 GHz band. According to the system 10 according to the present embodiment, such a frequency dependency can be efficiently measured, and it can contribute to the research in this field.

[0068] When at least one of the transmission antenna 150 and the reception antenna 160 can be repositioned within the housing 110, the reflection characteristic specifying unit 320 specifies the reflection coefficient for each of a plurality of incident angles for each arrangement using the delay time - incident angle relationship data registered for each arrangement. As illustrated in FIG. 11, by changing the arrangement of the reception antenna 160, the polarization can be changed. As a result, although there is a load in accurately positioning the transmission antenna 150 and the reception antenna 160, it becomes possible to specify the reflection coefficients for more incident angles or to specify the reflection characteristics for different polarizations, enabling more efficient specification of the reflection characteristics of the measurement target 20.

[0069] FIG. 12 schematically shows an example of the flow of the measurement process in the system 10. Here, the distance between the surfaces of the housing 110 of the member 100 is configured to be changeable, and the flow of the process when measurements are appropriately performed while changing the distance between the surfaces will be described. Note that the state where the measurement target 20 is in contact with the open portion of the housing 110 is defined as the start state.

[0070] In step 102 (steps may be abbreviated as S), the system 10 performs a measurement. Specifically, first, the analysis unit 316 causes the transmission antenna 150 to transmit radio waves, and the reception antenna 160 analyzes the received radio waves to specify the reception level for each delay time. Then, the reflection characteristic specifying unit 320 uses the reception level for each delay time, the reception level for each time of the radio waves transmitted from the transmission antenna 150 and received by the reception antenna 160 in a state where a total reflector is arranged at the open portion of the housing 110 of the member 100, and the delay time - incident angle relationship data corresponding to the state of the member 100 to calculate the reflection coefficient for each incident angle.

[0071] If the measurement of all the relationships of the distances between the surfaces has not been completed, the process proceeds to S106. If it has been completed, the process proceeds to S108. In S106, the positional relationship of the reflecting surface in the housing 110 of the member 100 is changed. Then, the process returns to S102 to execute the measurement. Such a change may be made by the experimenter conducting the experiment. In addition, when the member 100 is configured to be able to automatically change the positional relationship of the reflecting surface by electric drive or the like, such a change may be made automatically.

[0072] In S108, the reflection characteristic specifying unit 320 specifies the reflection characteristics of the measurement target 20 using the reflection coefficients for each incident angle calculated in S102. Then, the process ends.

[0073] In this way, by performing the measurement while appropriately changing the positional relationship between the surfaces, it is possible to efficiently increase the data of the reflection coefficients corresponding to the incident angles and improve the characteristic accuracy of the reflection characteristics. Note that in FIG. 12, the case of changing the positional relationship between the surfaces is illustrated, but the present invention is not limited thereto, and at least one of the positions of the transmission antenna 150 and the reception antenna 160 may be changed.

[0074] FIG. 13 schematically shows an example of the hardware configuration of a computer 1200 that functions as the specifying device 300. The program installed in the computer 1200 causes the computer 1200 to function as one or more "parts" of the device according to the present embodiment, or causes the computer 1200 to execute an operation associated with the device according to the present embodiment or the one or more "parts", and / or causes the computer 1200 to execute the process according to the present embodiment or a stage of the process. Such a program may be executed by the CPU 1212 to cause the computer 1200 to execute specific operations associated with some or all of the blocks of the flowcharts and block diagrams described herein.

[0075] The computer 1200 according to this embodiment includes a CPU 1212, a RAM 1214, and a graphic controller 1216, which are interconnected by a host controller 1210. The computer 1200 also includes input / output units such as a communication interface 1222, a storage device 1224, a DVD drive, and an IC card drive, which are connected to the host controller 1210 via an input / output controller 1220. The DVD drive may be a DVD-ROM drive, a DVD-RAM drive, or the like. The storage device 1224 may be a hard disk drive, a solid state drive, or the like. The computer 1200 also includes legacy input / output units such as a ROM 1230 and a keyboard, which are connected to the input / output controller 1220 via an input / output chip 1240.

[0076] The CPU 1212 operates according to programs stored in the ROM 1230 and the RAM 1214, thereby controlling each unit. The graphic controller 1216 acquires image data generated by the CPU 1212 in a frame buffer or the like provided in the RAM 1214 or in itself, and causes the image data to be displayed on the display device 1218.

[0077] The communication interface 1222 communicates with other electronic devices via a network. The storage device 1224 stores programs and data used by the CPU 1212 in the computer 1200. The DVD drive reads a program or data from a DVD-ROM or the like and provides it to the storage device 1224. The IC card drive reads programs and data from an IC card and / or writes programs and data to an IC card.

[0078] ROM 1230 stores therein a boot program or the like executed by the computer 1200 at activation, and / or a program dependent on the hardware of the computer 1200. The input / output chip 1240 may also be connected to the input / output controller 1220 via various input / output units such as a USB port, a parallel port, a serial port, a keyboard port, a mouse port, etc.

[0079] The program is provided by a computer-readable storage medium such as a DVD-ROM or an IC card. The program is read from the computer-readable storage medium, installed in the storage device 1224, the RAM 1214, or the ROM 1230 which is also an example of a computer-readable storage medium, and executed by the CPU 1212. The information processing described in these programs is read by the computer 1200, resulting in the cooperation between the programs and the various types of hardware resources described above. The device or method may be configured by realizing the operation or processing of information according to the use of the computer 1200.

[0080] For example, when communication is executed between the computer 1200 and an external device, the CPU 1212 may execute a communication program loaded in the RAM 1214 and instruct the communication interface 1222 to perform communication processing based on the processing described in the communication program. The communication interface 1222 reads the transmission data stored in the transmission buffer area provided in a recording medium such as the RAM 1214, the storage device 1224, the DVD-ROM, or the IC card under the control of the CPU 1212, transmits the read transmission data to the network, or writes the received data received from the network to the reception buffer area provided on the recording medium, etc.

[0081] In addition, the CPU 1212 may cause all or necessary portions of files or databases stored in an external recording medium such as the storage device 1224, a DVD drive (DVD-ROM), an IC card, etc. to be read into the RAM 1214, and may execute various types of processing on the data on the RAM 1214. Next, the CPU 1212 may write back the processed data to the external recording medium.

[0082] Various types of information such as various types of programs, data, tables, and databases may be stored in the recording medium and may undergo information processing. The CPU 1212 may perform various types of processing on the data read from the RAM 1214, including various types of operations, information processing, conditional judgment, conditional branch, unconditional branch, information search / replacement, etc. described throughout this disclosure and specified by the instruction sequence of the program, and write back the results to the RAM 1214. Also, the CPU 1212 may search for information in files, databases, etc. within the recording medium. For example, when a plurality of entries each having an attribute value of a first attribute associated with an attribute value of a second attribute are stored in the recording medium, the CPU 1212 searches for an entry that matches the condition where the attribute value of the first attribute is specified among the plurality of entries, reads the attribute value of the second attribute stored in the entry, and thereby may obtain the attribute value of the second attribute associated with the first attribute that satisfies a predetermined condition.

[0083] The programs or software modules described above may be stored in a computer-readable storage medium on or near the computer 1200. Also, a recording medium such as a hard disk or RAM provided within a server system connected to a dedicated communication network or the Internet can be used as a computer-readable storage medium, thereby providing the program to the computer 1200 via the network.

[0084] In the flowchart and block diagram in this embodiment, a block may represent a stage of a process in which an operation is executed or a "part" of a device having a role of executing an operation. A specific stage and "part" may be implemented by a dedicated circuit, a programmable circuit supplied with computer-readable instructions stored on a computer-readable storage medium, and / or a processor supplied with computer-readable instructions stored on a computer-readable storage medium. The dedicated circuit may include digital and / or analog hardware circuits and may include an integrated circuit (IC) and / or discrete circuits. The programmable circuit may include, for example, a reconfigurable hardware circuit including logical products, logical sums, exclusive logical sums, negative logical products, negative logical sums, and other logical operations, flip-flops, registers, and memory elements, such as a field programmable gate array (FPGA) and a programmable logic array (PLA).

[0085] The computer-readable storage medium may include any tangible device capable of storing instructions executable by an appropriate device. As a result, a computer-readable storage medium having instructions stored therein will comprise a product including instructions executable to create means for performing the operations specified in the flowchart or block diagram. Examples of the computer-readable storage medium may include an electronic storage medium, a magnetic storage medium, an optical storage medium, an electromagnetic storage medium, a semiconductor storage medium, and the like. More specific examples of the computer-readable storage medium may include a floppy (registered trademark) disk, a diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an electrically erasable programmable read-only memory (EEPROM), a static random access memory (SRAM), a compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), a Blu-ray (registered trademark) disc, a memory stick, an integrated circuit card, and the like.

[0086] Computer-readable instructions may include any combination of one or more programming languages, including assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state-setting data, or source code or object code written in an object-oriented programming language such as Smalltalk®, JAVA®, C++, and a conventional procedural programming language such as the "C" programming language or a similar programming language.

[0087] The computer-readable instructions may be provided locally or via a wide area network (WAN) such as a local area network (LAN), the Internet, etc. to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, or a programmable circuit, for the processor of the general-purpose computer, the special-purpose computer, or other programmable data processing device, or the programmable circuit to execute the computer-readable instructions to generate means for performing the operations specified in the flowchart or block diagram. Examples of processors include computer processors, processing units, microprocessors, digital signal processors, controllers, microcontrollers, etc.

[0088] As described above, the present invention has been described using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various changes or improvements can be made to the above embodiments. It is clear from the description of the claims that forms with such changes or improvements may also be included in the technical scope of the present invention.

[0089] In the claims, the specification, and the drawings, the execution order of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown is not explicitly indicated as "earlier" or "preceding" etc. in particular, and it should be noted that it can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the specification, and the drawings, even if it is described using "first," "next," etc. for convenience, it does not mean that it is essential to be implemented in this order.

Explanation of Reference Numerals

[0090] 10 System, 20 Object to be Measured, 100 Member, 110 Housing, 111 E Plane, 112 W Plane, 113 C Plane, 114 F Plane, 115 S Plane, 116 N Plane, 150 Transmitting Antenna, 160 Receiving Antenna, 200 Analyzer, 300 Specifying Device, 302 Mirror Space, 304 Long Delay Cut, 312 Registration Unit, 314 Storage Unit, 316 Analysis Unit, 318 Analysis Result Acquisition Unit, 320 Reflection Characteristic Specifying Unit, 400 Delay Profile, 410 Reflection Coefficient Incidence Angle Characteristic, 500 Delay Profile, 502 Long Delay Cut, 600 Reflection Coefficient Incidence Angle Characteristic, 1200 Computer, 1210 Host Controller, 1212 CPU, 1214 RAM, 1216 Graphics Controller, 1218 Display Device, 1220 Input / Output Controller, 1222 Communication Interface, 1224 Storage Device, 1230 ROM, 1240 Input / Output Chip

Claims

1. A housing having an inner surface at least partially open and at least partially reflecting radio waves, A transmission antenna disposed within the housing, A reception antenna disposed within the housing, A reflection characteristic specifying unit that specifies the incident angle dependence of the radio wave reflection characteristics of the measurement object based on the radio waves transmitted from the transmission antenna and received by the reception antenna in a state where the measurement object is disposed in the open portion of the housing A system comprising.

2. A housing having an inner surface at least partially open and at least partially reflecting radio waves, A transmission antenna disposed within the housing, A reception antenna disposed within the housing, A reflection characteristic specifying unit that specifies the reflection characteristics of the radio waves of the measurement object based on the radio waves transmitted from the transmission antenna and received by the reception antenna in a state where the measurement object is disposed in the open portion of the housing Comprising, The housing is a polyhedron having a plurality of faces with at least one side open, A system in which the inner surfaces of two or more of the plurality of faces are radio wave reflecting surfaces.

3. A housing having an inner surface at least partially open and at least partially reflecting radio waves, A transmission antenna disposed within the housing, A reception antenna disposed within the housing, A reflection characteristic specifying unit that specifies the reflection characteristics of the radio waves of the measurement object based on the radio waves transmitted from the transmission antenna and received by the reception antenna in a state where the measurement object is disposed in the open portion of the housing Comprising, The reflection characteristic specifying unit specifies the reflection characteristics of the measurement object using delay time incident angle relationship data indicating the relationship between the delay time from when the radio wave transmitted from the transmission antenna is reflected by a reflector disposed in the open portion of the housing and reaches the reception antenna and the incident angle when the radio wave is incident on the reflector. A system.

4. A housing having an inner surface at least partially open and at least partially reflecting radio waves, A transmission antenna disposed within the housing, A reception antenna disposed within the housing, A reflection characteristic specifying unit that specifies the reflection characteristics of the radio waves of the measurement object based on the radio waves transmitted from the transmission antenna and received by the reception antenna in a state where the measurement object is disposed in the open portion of the housing Comprising, A system in which the orientation of at least one of the transmission antenna and the reception antenna is configured to be changeable.

5. The housing has one side open and is a rectangular parallelepiped having a first face, a second face facing the first face, a third face, a fourth face facing the third face, and a fifth face facing the open side. Inner surfaces of the first face and the second face are radio wave reflecting surfaces. The system according to any one of claims 1 to 4, wherein inner surfaces of the third face and the fourth face are radio wave absorbing surfaces.

6. The system according to claim 5, wherein an inner surface of the fifth face is a radio wave absorbing surface.

7. The system according to claim 5, wherein the distance between the first face and the second face is configured to be changeable.

8. The housing has one side open and is a rectangular parallelepiped having a first face, a second face, a third face facing the first face, a fourth face facing the second face, and a fifth face facing the open side. The first face, the second face, the third face, and the fourth face are configured to be switchable between a state in which the first face and the second face are radio wave reflecting surfaces and the third face and the fourth face are radio wave absorbing surfaces, and a state in which the first face and the second face are radio wave absorbing surfaces and the third face and the fourth face are radio wave reflecting surfaces. The system according to any one of claims 1 to 4.

9. The system according to any one of claims 1 to 4, wherein the transmission antenna and the reception antenna are arranged so as not to have a positional relationship symmetric with respect to the center of gravity of the housing.

10. The reflection characteristic specifying unit uses the reception level of the radio wave transmitted from the transmission antenna and received by the reception antenna at each time, with a reflector having a known reflection coefficient arranged in the open portion of the housing, the reception level of the radio wave transmitted from the transmission antenna and received by the reception antenna at each time, with the measurement target arranged in the open portion of the housing, and the delay time incident angle relationship data to specify the reflection characteristic of the measurement target. The system according to claim 3.

11. A storage unit that stores delay time incident angle relationship data indicating the relationship between the delay time from when radio waves transmitted from a transmission antenna disposed in the housing are reflected by the reflector and reach a reception antenna disposed in the housing until they reach the reflector and the incident angle when the radio waves are incident on the reflector, in a state where the reflector is disposed at an open portion of a housing having an inner surface that is at least partially open and at least partially reflects radio waves. An analysis result acquisition unit that acquires an analysis result obtained by analyzing radio waves transmitted from the transmission antenna and received by the reception antenna in a state where a measurement target is disposed at an open portion of the housing. A reflection characteristic specifying unit that specifies the radio wave reflection characteristics of the measurement target based on the analysis result and the delay time incident angle relationship data. A specifying device comprising the above.

12. A program for causing a computer to function as the specifying device according to Claim 11.

13. A housing having at least a part that is open and an inner surface that at least partially reflects radio waves. A transmission antenna disposed in the housing. A reception antenna disposed in the housing. Comprising the above. The housing is a polyhedron having a plurality of faces, with at least one side being open. A member in which the inner surfaces of two or more of the plurality of faces are radio wave reflecting surfaces.

14. A housing having at least a part that is open and an inner surface that at least partially reflects radio waves. A transmission antenna disposed in the housing. A reception antenna disposed in the housing. Comprising the above. A member in which the orientation of at least one of the transmission antenna and the reception antenna is configured to be changeable.

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