Id tag, measurement system, and arrangement method

Abstract

To present different IDs in a plurality of directions, respectively.SOLUTION: An ID tag 1 includes a plurality of scatterers 11 arranged in a two dimensional manner. Each of the scatterers 11 has different azimuth characteristics with which the scatterer reradiates with predetermined reflection intensity with respect to radio waves emitted from a predetermined azimuth. The scatterers 11 form combinations of scatterers located at equal distance from a first position, and combinations of scatterers located at equal distance from a second position which is different in at least azimuth with respect to the scatterers 11 from the first position.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to ID tags, measurement systems and placement methods. [Background technology]

[0002] RFID (Radio Frequency Identification) is well known. RFID is capable of presenting an ID (identifier) ​​by connecting an IC (integrated circuit) to the antenna inside the tag and re-emitting the radio waves emitted from the reader after modulating them.

[0003] The IC operates using the energy of the incident radio waves. RFID tags are battery-less. They can store a large amount of information. However, the maximum readable distance of an RFID tag is limited by the antenna gain, so it is about 5m.

[0004] Chipless RFID embeds ID information into the design pattern of the antenna, waveguide, or scatterer inside the tag. Chipless RFID is a technology that embeds desired information into reflected waves without an IC, and presents an ID (see Non-Patent Document 1). Since it offers greater design freedom than conventional RFID, chipless RFID can reduce the environmental impact and expand the reading range. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] H, Cristian, et al., "Chipless-RFID: a review and recent developments." Sensors, 2019, 19, 3385 Summary of the Invention [Problem to be solved by the invention]

[0006] However, a conventional chipless RFID cannot present different IDs in multiple directions with a single chipless RFID.

[0007] The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide a technology capable of presenting a different ID in each of a plurality of directions. [Means for solving the problem]

[0008] An ID tag of one embodiment of the present disclosure comprises a plurality of scatterers arranged two-dimensionally, each of the plurality of scatterers having a different azimuth angle characteristic for re-radiating radio waves irradiated from a predetermined azimuth angle with a predetermined reflection intensity, and the plurality of scatterers form a combination of a plurality of scatterers located equidistant from a first position and a combination of a plurality of scatterers located equidistant from a second position that has an azimuth angle different from the first position with respect to the plurality of scatterers.

[0009] A measurement system of one embodiment of the present disclosure includes an ID tag and a radar that irradiates radio waves to the ID tag and acquires values ​​from the distance intensity distribution of the radio waves re-radiated from the ID tag, wherein the ID tag includes a plurality of scatterers arranged two-dimensionally, each of the plurality of scatterers having a different azimuth angle characteristic for re-radiating the radio waves irradiated from a predetermined azimuth angle with a predetermined reflection intensity, and the plurality of scatterers form a combination of a plurality of scatterers located equidistant from a first position and a combination of a plurality of scatterers located equidistant from a second position having an azimuth angle different from the first position with respect to the plurality of scatterers.

[0010] A placement method of one embodiment of the present disclosure includes an ID tag and a radar that irradiates radio waves to the ID tag and acquires values ​​from the distance intensity distribution of the radio waves re-radiated from the ID tag, wherein the ID tag includes a plurality of scatterers arranged two-dimensionally, each of the plurality of scatterers having a different azimuth angle characteristic for re-radiating the radio waves irradiated from a predetermined azimuth angle with a predetermined reflection intensity, and the plurality of scatterers form a combination of a plurality of scatterers located equidistant from a first position and a combination of a plurality of scatterers located equidistant from a second position having an azimuth angle different from the first position with respect to the plurality of scatterers. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide a technique capable of presenting a different ID in each of a plurality of directions. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating the system configuration of a measurement system according to the present disclosure. [Diagram 2] FIG. 2 is a diagram illustrating an example in which the measurement system is applied to an automobile. [Diagram 3] FIG. 3 is a diagram illustrating an example in which the measurement system is applied to a UAV. [Figure 4] FIG. 4 is a diagram showing an example of a distance intensity distribution read by a radar from an ID tag in a measurement system. [Diagram 5] FIG. 5 is a diagram for explaining an example of values ​​presented in two directions by an ID tag in a measurement system. [Figure 6] FIG. 6 is a diagram illustrating an example of a top view of an ID tag. [Figure 7] FIG. 7 is a diagram for explaining an example of the positions of a combination of scatterers that constitute a value presented by an ID tag relative to the radar position. [Figure 8] FIG. 8 is a diagram showing an example of the shape and azimuth angle characteristics of a scatterer. [Figure 9]FIG. 9 is a diagram defining the positions of scatterers arranged on an ID tag. [Figure 10] FIG. 10 shows an example in which a scatterer pattern is arranged on an ID tag that presents a predetermined bit string. [Figure 11] FIG. 11 shows an example of a measurement system including the ID tag and radar of FIG. [Figure 12] FIG. 12 shows an example of a bit string read from the ID tag in FIG. 10 by the measurement system in FIG. [Figure 13] FIG. 13 is a diagram for explaining an example of the effective area of ​​a scatterer (part 1). [Figure 14] FIG. 14 is a diagram for explaining an example of the effective area of ​​a scatterer (part 2). [Figure 15] FIG. 15 is a diagram for explaining an example of the effective area when a part of the opening of the scatterer is cut away (part 1). [Figure 16] FIG. 16 is a diagram for explaining an example of the effective area when a part of the opening of the scatterer is cut away (part 2). [Figure 17] FIG. 17 is a diagram comparing the angular characteristics of the RCS in a scatterer using an electromagnetic field simulation with the approximate value of the RCS calculated from the effective area. [Figure 18] FIG. 18 is a diagram illustrating an example of an arrangement method in the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same parts are given the same reference numerals and the description will be omitted.

[0014] (Measurement System) A measurement system 5 according to the present disclosure will be described with reference to Fig. 1. The measurement system 5 includes an ID tag and a radar 2.

[0015] The ID tag 1 uses chipless RFID technology to present different values ​​in multiple directions. The value presented by the ID tag 1 is expressed as a binary number of 1 or more bits. It may be an identifier. Here, the multiple directions differ in at least the azimuth angle φ with respect to the ID tag 1. The multiple directions may also differ in the depression angle θ (elevation angle).

[0016] The radar 2 irradiates the ID tag 1 with radio waves and obtains a value from the distance intensity distribution of the radio waves re-emitted from the ID tag 1. The radar 2 is sometimes called a distance measuring radar.

[0017] The radar 2 may read a plurality of columns of the ID tag 1 that are separated by at least the resolution in the ground range direction. This allows the radar 2 to obtain a multi-bit binary number from one direction and one ID tag 1. In the present disclosure, the ID tag 1 presents different values ​​in a plurality of directions, so that the radar 2 can obtain a multi-bit binary number from each direction. For example, the radar 2 obtains a first value at a first position and obtains a second value at a second position. The radar 2 may move between the first position and the second position. Alternatively, two radars 2 having the same function may be disposed at each of the first position and the second position.

[0018] In the example shown in FIG. 1, radar 2a is located in a first direction (θ1, φ1). The ID tag 1 can present a value "1001" to radar 2a located in the first direction. Radar 2b is located in a second direction (θ2, φ2). The ID tag 1 can present a value "1101" to radar 2b located in the second direction. Radar 2c is located in a third direction (θ3, φ3). The ID tag 1 can present a value "1100" to radar 2c located in the third direction.

[0019] The radar 2 is, for example, a millimeter wave (FMCW: Frequency Modulated Continuous Wave) radar (S. Lee, S. Kang, S.-C. Kim, and J.-E. Lee, “Radar cross section measurement with 77 ghz automotive fmcw radar,” in 2016 IEEE 27 th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC). IEEE, 2016, pp. 1-6.) Using a 79 GHz millimeter wave FMCW radar and using the 77 to 81 GHz band, a distance resolution of 37.5 mm is achieved. The distance resolution is calculated as the speed of light / (2 x available bandwidth).

[0020] Such a measurement system 5 may be applied to a moving vehicle such as an automobile or an Unmanned Aerial Vehicle (UAV), as shown in FIGS.

[0021] In the example shown in Fig. 2, the ID tag 1 is installed on the side of a two-way road. A millimeter wave radar mounted on each vehicle is used to read the ID tag 1. A scatterer that allows each vehicle to read the ID tag 1 is placed in the azimuth direction that makes it easy for each vehicle to read the ID tag 1. The ID tag 1 can present a different ID to each vehicle traveling in a different direction.

[0022] In the example shown in Fig. 3, the ID tag 1 is grounded at a position where UAVs flying from different directions meet. The UAVs read the ID tag 1 using a millimeter wave radar, similar to the example in Fig. 2. In the ID tag 1, scatterers that are read by each UAV are placed in the azimuth direction that makes it easy for each UAV to read. The ID tag 1 can present different IDs to UAVs flying from different directions.

[0023] As shown in Figures 2 and 3, the measurement system 5 can extend the outdoor autonomous control capability of a mobile object such as a car or a UAV. The signal-to-noise (SN) ratio determines the bit error rate (BER) of a bit string. The measurement system 5 uses chipless RFID tags, so the high SNR can ensure the safety of the guidance.

[0024] The measurement system 5 is equipped with an ID tag 1 and a radar 2 using chipless RFID technology, and therefore is compatible with all day and all weather conditions. With conventional camera recognition technology, the mechanisms for grasping the surrounding situation and controlling the aircraft may not function properly in poor visibility conditions. In contrast, the measurement system 5 according to the present disclosure can support advanced control of a moving object even in poor visibility conditions.

[0025] (ID tag) The ID tag 1 according to the present disclosure will be described with reference to Fig. 4 etc. The ID tag 1 employs a spatial modulation method for encoding chipless RFID, and expresses a bit string by the arrangement pattern of the scatterers 11.

[0026] The ID tag 1 is provided on an XY plane. A plurality of scatterers 11 are arranged two-dimensionally on the XY plane. The scatterers 11 are, for example, corner reflectors or triangular pyramid-shaped metal bodies formed by processing the hollow portion of a corner reflector. A typical corner reflector has a retroreflective function and therefore has a high radar cross section (RCS). The RCS is an index that indicates the ability to re-radiate irradiated radio waves in the direction of a receiving antenna.

[0027] In the present disclosure, each of the multiple scatterers 11 has a different azimuth angle characteristic. The azimuth angle characteristic is a characteristic of re-radiating radio waves irradiated from a predetermined azimuth angle with a predetermined reflection intensity. Specifically, in the present disclosure, the scatterer 11 re-radiates radio waves from a predetermined azimuth angle with high reflection intensity, and re-radiates radio waves from a predetermined azimuth angle with low reflection intensity. Note that it is not necessary for all the scatterers 11 arranged in the ID tag 1 to have different azimuth angle characteristics. As will be described with reference to FIG. 8 etc., the azimuth angle characteristic of each scatterer 11 may be divided into a plurality of patterns.

[0028] The radar 2 measures the sum of reflection intensities from the scatterers 11 at the same distance from the radar 2 among the multiple scatterers 11 on the ID tag 1 as the reception intensity, and measures the distance intensity distribution. The distance intensity distribution shown in the upper right diagram of FIG. 4 is a distribution in which the sum of reflection intensities for each distance is associated. The radar 2 determines the bit string "1101" from the distance intensity distribution of FIG. 4. In this disclosure, a case will be described in which power equal to or greater than a predetermined value is converted to "1", and power less than the predetermined value is converted to "0". In other embodiments, the conversion may be performed using other functions. It is sufficient that the conversion formula is shared between the ID tag 1 and the radar 2.

[0029] In the measurement system 5, the radar 2 is assumed to be located sufficiently far away from the ID tag 1. The dashed line on the ID tag 1 indicates the straight line where the plane of the ID tag 1 intersects with a plane perpendicular to the vector of the incident wave emitted by the radar 2. In other words, the positions of the scatterers 11 on the ID tag that are equidistant from the radar 2 are indicated by the dashed line.

[0030] 5, a combination of multiple scatterers positioned equidistant from a first position and a combination of multiple scatterers positioned equidistant from a second position are formed on the ID tag 1. The first position and the second position differ at least in azimuth angle with respect to the scatterer 11 on the ID tag 1. The first position and the second position may differ in depression angle as well as azimuth angle.

[0031] In the upper left diagram of FIG. 5, the dashed lines on the ID tag 1 indicate positions equidistant from the first position. A plurality of scatterers 11 are arranged in each of the first column b1, the second column b2, the third column b3, and the fourth column. Similarly, in the upper right diagram of FIG. 5, the dashed lines on the ID tag 1 indicate positions equidistant from the second position. A plurality of scatterers 11 are arranged in each of the first column b1, the second column b2, the third column b3, and the fourth column.

[0032] The ID tag 1 presents a one-bit binary value at a first position, which is the sum of the reflection intensities of a plurality of scatterers located at an equal distance from the first position to the first position. The ID tag 1 presents a one-bit binary value, specifically, "1" or "0", at the sum of the reflection intensities of a plurality of scatterers 11 located on the first row b1 to the first position. Similarly, the ID tag 1 presents a one-bit binary value at a second position, which is the sum of the reflection intensities of a plurality of scatterers located at an equal distance from the second position to the second position.

[0033] Also, a first combination of a plurality of scatterers located at a first distance from the first position and a second combination of a plurality of scatterers located at a second distance from the first position present two-bit binary values ​​at the first position. For example, the first combination is a first column b1, and the second combination is a second column b2. Each column presents one bit of binary value. In the example shown in FIG. 5, the ID tag 1 can present four columns of binary values ​​for each position.

[0034] In the upper left of Fig. 5, the radar 2a is at a first position (r1, θ1, φ1). Here, r1 is the distance from the center of the ID tag 1. θ1 and φ1 are the azimuth angle and depression angle of the radar 2a with respect to the center of the ID tag 1. Starting from the position closest to the radar 2a at the first position, each scatterer 11 for reading the first column b1, the second column b2, the third column b3, and the fourth column b4 are placed on each dashed line.

[0035] 5, the radar 2b is at a second position (r2, θ2, φ2). Starting from the position closest to the radar 2b at the second position, the scatterers 11 are placed on each broken line in order to read the first bit b1, the second bit b2, the third bit b3, and the fourth bit b4.

[0036] At the first position, the radar 2 obtains the sum of the reflection intensities of the scatterers 11 located on the first row b1 as the reflection intensity of the distance to the dashed line of the first row b1. Similarly, the radar 2 obtains the sum of the reflection intensities of the scatterers located on the second row b2, the third row b3, and the fourth row b4 as the reflection intensity of the distance to each dashed line. If the reflection intensity is equal to or greater than a predetermined value, the radar 2 determines that the bit is "1", and if it is less than the predetermined value, it is "0". At the first position, the radar 2 reads a value in which the values ​​"1" or "0" of each row are arranged as a first value from the ID tag 1. Similarly, the radar 2 reads a second value from the ID tag 1 at the second position.

[0037] In this disclosure, in FIG. 5, bi=(0,1) indicates that the i-th bit of the value presented by ID tag 1 for the first position is 0 or 1. bj=(0,1) indicates that the j-th bit when viewed from the second position is 0 or 1. bij=(00,01,10,11) indicates that the combination of the i-th bit when viewed from the first position and the j-th bit when viewed from the second position is 00, 01, 10, or 11.

[0038] 6 and 7, the relationship between the position of the scatterer 11 on the ID tag 1 and the direction in which the ID is presented is shown. The ID tag 1 shown in Fig. 6 presents values ​​in three directions, Da, Db, and Dc. The three directions, Da, Db, and Dc, have azimuth angles of 0°, 120°, and 240°, respectively. The ID tag 1 presents a 4-bit bit string for each direction.

[0039] The scatterers 11 installed in the ID tag 1 each have a triangular pyramid shape with an equilateral triangular base. In Fig. 6, the scatterers 11 are arranged with their bottoms facing up and with the sides of their bottoms in contact with each other.

[0040] 7(a)-(c) show the positions of the scatterers 11 that derive the value presented by the ID tag 1 when the ID tag 1 shown in FIG. 6 is viewed from each of the directions Da, Db, and Dc. In FIG. 7(a), when the ID tag 1 is viewed from the direction Da, the four bits of the value presented by the ID tag 1 are derived by the scatterers 11 arranged in a direction perpendicular to the direction Da on the ID tag 1. In order from the closest to the direction Da, an arrangement of the scatterers 11 that derive the first bit b1, an arrangement of the scatterers 11 that derive the second bit b2, an arrangement of the scatterers 11 that derive the third bit b3, and an arrangement of the scatterers 11 that derive the fourth bit b1 are formed. As shown in FIG. 7(b) and (c), an arrangement of the scatterers 11 is formed similarly when viewed from each of the directions Db and Dc.

[0041] 7, each scatterer 11 on the ID tag 1 derives a predetermined bit to be presented in a direction Da, a predetermined bit to be presented in a direction Db, and a predetermined bit to be presented in a direction Dc. Therefore, each scatterer 11 has desired reflection characteristics for each direction according to the value of the bit that the scatterer 11 derives for each direction.

[0042] (Scatterer) The azimuth angle characteristic of the scatterer 11 is specified by whether the reflection intensity at a position where the ID tag 1 presents the ID is higher or lower than a predetermined value. For example, when the ID tag 1 presents an ID at two positions, the azimuth angle characteristic of the scatterer 11 is specified by a combination of the reflection intensity at the first position being "higher or lower" than a predetermined value and the reflection intensity at the second position being "higher or lower" than a predetermined value.

[0043] The ID tag 1 that presents its ID at two positions includes a scatterer 11 having azimuth angle characteristics of the following four patterns. As the number of positions at which the ID tag 1 presents its ID increases, the variation of the scatterer 11 also increases. (1) The reflection intensity for the first position is higher than a predetermined value, and the reflection intensity for the second position is higher than a predetermined value; (2) the reflection intensity for the first position is higher than a predetermined value, and the reflection intensity for the second position is lower than a predetermined value; (3) the reflection intensity for the first location is lower than a predetermined value and the reflection intensity for the second location is higher than a predetermined value; and (4) The reflection intensity for the first position is lower than a predetermined value, and the reflection intensity for the second position is lower than a predetermined value.

[0044] The azimuth angle characteristic of the scatterer 11 can also be expressed as follows. The scatterer 11 may belong to both a first combination that presents a value of one bit at a first position and a second combination that presents a value of one bit at a second position. In such a scatterer 11, the reflection intensity to a position, of the first position and the second position, that presents a value whose sum is equal to or greater than a predetermined value, is stronger than the reflection intensity to a position, of the first position and the second position, that presents a value whose sum is less than the predetermined value.

[0045] For example, if the sum of the combination of scatterers is equal to or greater than a predetermined value, the bit value is "1", and if it is less than the predetermined value, the bit value is "0". A scatterer 11 belonging to both a combination that presents "1" at a first position and a combination that presents "0" at a second position has a stronger reflection intensity in the direction of the first position than in the direction of the second position, and has a weaker reflection intensity in the direction of the second position than in the direction of the first position. Moreover, a strong reflection intensity may mean a reflection intensity stronger than a predetermined value. A weak reflection intensity may mean a reflection intensity weaker than a predetermined value.

[0046] The scatterers 11 are arranged in the ID tag 1 according to the azimuth angle characteristics. For example, the azimuth angle characteristics of each of the multiple scatterers included in the first combination and the azimuth angle characteristics of each of the multiple scatterers included in the second combination are specified so that the sum of the reflection intensities at a first position by the multiple scatterers included in the first combination becomes a predetermined value, and the sum of the reflection intensities at a second position by the multiple scatterers included in the second combination becomes a predetermined value. This process may be performed by, for example, optimization processing by a computer.

[0047] Here, the "predetermined value" is determined by the values ​​presented by the first and second combinations, for example, where the bit value is "1" when the sum of the combination of scatterers is equal to or greater than the predetermined value, and the bit value is "0" when the sum is less than the predetermined value. When the first combination presents "1", the sum of the reflection intensities at the first position due to the multiple scatterers included in the first combination is required to be equal to or greater than the predetermined value. On the other hand, when the second combination presents "0", the sum of the reflection intensities at the second position due to the multiple scatterers included in the second combination is required to be less than the predetermined value.

[0048] Once the azimuth angle characteristics of each scatterer 11 belonging to the first combination and the azimuth angle characteristics of each scatterer belonging to the second combination are determined, each scatterer 11 included in the first combination is placed at a position equidistant from the first position on the ID tag 1. Similarly, each scatterer 11 included in the second combination is placed at a position equidistant from the second position on the ID tag 1.

[0049] With reference to FIG. 8, an example of the shape and azimuth angle characteristics of the scatterer 11 is shown. In the present disclosure, the scatterer 11 has a triangular pyramid shape with its slopes formed of a metal member. The scatterer 11 may be formed hollow, partially filled with a metal member, or entirely filled with a metal member to form a solid scatterer. In the ID tag 1, the bases of the triangular pyramid shapes are two-dimensionally arranged with the apex of the triangular pyramid shape facing downward and the base facing upward. The scatterer 11 is, for example, a corner reflector, or a triangular pyramid-shaped metal body formed by processing the hollow portion of a corner reflector.

[0050] The bottom surface of the scatterer 11 has an opening shape that corresponds to the azimuth angle characteristic of the scatterer 11. Depending on the directional characteristic to be realized, the scatterer 11 may have a part of the hollow portion covered with a metal member. Also, the scatterer 11 may not be hollow, but may be solid and filled with a metal member.

[0051] In the present disclosure, the bottom surface of the scatterer 11 is formed into a predetermined equilateral triangle regardless of the azimuth angle characteristics realized by the scatterer 11. By forming the bottom surface into an equilateral triangle, each scatterer 11 can be disposed interchangeably in each space shown in FIG.

[0052] In this disclosure, the azimuth angle characteristics of the scatterer 11 will be explained by dividing them into six patterns in FIG. 8. The upper part of FIG. 8 shows the shape of the opening part on the bottom surface of the scatterer 11. The lower part of FIG. 8 shows the opening shape with respect to the bottom surface by hatching. The lower part of FIG. 8 further shows the direction in which the reflection intensity of the scatterer 11 is stronger than a predetermined value. Moreover, the dashed parts in the E1 and E2 patterns in the lower part of FIG. 8 indicate that the opening has been cut away.

[0053] The name of each pattern is determined by the direction of reflection and the number of directions. If the reflection direction is the vertex direction, it is named V, if it is the edge direction, it is named E, followed by the number of directions, 1 or 2. A pattern is a pattern that reflects in each direction, and N is a pattern that does not reflect in each direction.

[0054] (1) A pattern: The slopes are made of a metal material and have a hollow triangular pyramid shape. The A pattern scatterer 11 is formed of three slopes made of metal material with the same thickness, and the bottom is open. The A pattern scatterer 11 achieves strong reflection intensity in each azimuth angle direction of the three vertices and three sides.

[0055] (2) V2 pattern: Compared to the A(V3, E3) pattern, one vertex of the bottom surface is covered with a metal member. The scatterer 11 of the V2 pattern realizes a strong reflection intensity from the center of gravity of the bottom surface to the vertices other than the vertex covered with the metal member, specifically, in the direction of the two open vertices.

[0056] (3) V1 pattern: Compared to the V2 pattern, the two vertices of the bottom surface are covered with a metal member. The scatterer 11 of the V1 pattern realizes a strong reflection intensity from the center of gravity of the bottom surface to the vertices other than the vertices covered with the metal member, specifically, in the direction of one vertex that is open.

[0057] (4) E2 pattern: Compared to the A pattern, one side of the bottom surface is formed thicker than the other two sides and is covered with a metal member. The scatterer 11 of the E2 pattern realizes a strong reflection intensity from the center of gravity of the bottom surface to the two sides other than the side formed thicker, specifically, the two sides formed thinner than the others. Note that in the present disclosure, when the bottom side is placed at the top and viewed from above, the side portion formed thicker is filled with a metal member up to the vertically downward direction of the end of the side formed thicker, and is designed so that the volume of the opening portion is smaller than that of the A pattern.

[0058] (5) E1 pattern: Compared to the A pattern, two sides of the bottom surface are formed thicker than the other sides and are covered with a metal member. The scatterer 11 of the E1 pattern realizes a strong reflection intensity from the center of gravity of the bottom surface to the side other than the side formed thicker, specifically, the side formed thinner than the others. As with the E2 pattern, the side portion formed thicker in this disclosure may be filled with a metal member up to the vertical downward direction of the end of the side formed thicker when viewed from above with the base side positioned upward. The E1 pattern is designed to have a smaller volume of the opening portion than the A pattern and the E2 pattern.

[0059] (6) N pattern: A solid triangular pyramid shape with its slope and bottom made of metal. The N pattern scatterer 11 nullifies the reflection intensity in each azimuth angle direction of the three vertices and three sides.

[0060] As shown in Fig. 8, when a portion of the opening shape of the bottom surface close to a predetermined direction is open, the reflection intensity in the predetermined direction is stronger than when it is covered. For example, when an opening at a vertex is covered, the RCS from the center of gravity of the bottom surface to the vertex is invalidated, and the reflection intensity is relatively stronger in other vertex directions. When an opening at a side is covered, the RCS from the center of gravity to the side is invalidated, and the reflection intensity is relatively stronger in other side directions.

[0061] (Placement method) As shown in Fig. 9, each scatterer 11 with an equilateral triangular base is arranged on the ID tag 1 with the apex facing downward and the base facing upward. The position of each scatterer 11 arranged in Fig. 8 is uniquely identified by coordinates determined by Da, Db, and Dc. Here, Da, Db, and Dc are coordinate axes corresponding to the direction in which the ID tag 1 presents its ID. For Da, Db, and Dc, the values ​​-1, 0, 1, and 2 are given in the direction of the arrow, respectively.

[0062] Here, Da, Db, and Dc have the relationship shown in equation (1).

[0063]

number

[0064] Define S(Da, Db, Dc) as the pattern (shape) of the scatterer 11 arranged at the coordinates (Da, Db, Dc). The pattern of the scatterer 11 is the six shapes shown in FIG. 8. By determining S(Da, Db, Dc), the arrangement of the scatterer 11 on the ID tag 1 is determined.

[0065]

Number

[0066] Define the azimuthal direction {φd} (0 ≦ d < Nd) in which the ID tag 1 presents the ID.

[0067] When presenting an ID of Nb bits in each of the Nd directions, for the direction d (0 ≦ d < Nd), the nth (0 ≦ n < Nb) bit is set to B d n = {1.0}. The information of the ID presented by the ID tag 1 is expressed as a two-dimensional array of Nd × Nb.

[0068] At this time, the bit string B presented by the ID tag 1 in each direction is defined by Equation (3).

[0069]

Number

[0070] When the bit string B presented by the ID tag 1 is given by Equation (3), S(Da, Db, Dc) is obtained by Equation (4).

[0071]

Number

[0072] As shown in formula (4), when the bit string B of the ID presented by the ID tag 1 in each azimuth direction and the coordinates (Da, Db, Dc) at which the scatterer is placed are given, the pattern S (Da, Db, Dc) of the scatterer 11 placed at that position is determined. In the example shown in Fig. 8, at a certain position, if the values ​​presented in three directions by the scatterer 11 placed at that position are determined, the number of reflections at that position is determined.

[0073] In this disclosure, whether the pattern of the scatterers 11 arranged at positions in the ID tag 1 is V-type or E-type is determined by the relationship between the orientation in which the scatterers 11 are arranged and the azimuth angle direction. As shown in Fig. 9, the azimuth angle direction may be from the center of gravity to the apex direction or from the center of gravity to the side direction depending on the orientation of the scatterers 11. In the ID tag 1 shown in Fig. 9, the azimuth angle direction is known, and the orientation of the scatterers 11 in the ID tag 1 is also determined from the position of the scatterers 11.

[0074] Fig. 10 shows an example of the pattern arrangement of the scatterers 11 when the bit string B shown in formula (3) is presented in the ID tag 1 shown in Fig. 9. The ID tag 1 shown in Fig. 10 has a side of 174 mm and a length in the X direction of 30 mm.

[0075] FIG. 12 shows the results of measuring the ID tag 1 shown in FIG. 10 by the measurement system 5 shown in FIG. 11. The measurement system 5 shown in FIG. 11 includes the ID tag 1 and the radar 2. As shown in FIG. 10, the ID tag 1 has a plurality of scatterers 11 arranged therein, and the opening shape of the bottom surface of each scatterer 11 is controlled to achieve a desired reflection intensity. The radar 2 is disposed above the ID tag 1. The radar 2 irradiates radio waves to the ID tag 1 at a depression angle of 30° from positions with azimuth angles of 0°, 120°, and 240° relative to the ID tag 1. The radar 2 acquires values ​​from the distance intensity distribution of the radio waves re-emitted from the ID tag 1.

[0076] 12 shows the distance intensity distribution of the radio waves re-emitted by the radar 2 from the ID tag 1. Here, power of 20db or more is set to "1" and power of less than 20db is set to "0".

[0077] Figure 12(a) shows the distance intensity distribution read from the direction Da. The value "1101" can be read from Figure 12(a).

[0078] Figure 12(b) shows the distance intensity distribution read from the direction Db. The value "1001" can be read from Figure 12(b).

[0079] Figure 12(c) shows the distance intensity distribution read from the direction Dc. The value of "0010" can be read from Figure 12(c).

[0080] In this way, the ID tag 1 using chipless RFID technology is a chipless RFID and can present a different ID in each of a plurality of directions.

[0081] (Details of the scatterer shape) The inventors discovered that RCS in a specific direction can be suppressed by cutting the aperture surface of the corner reflector. This is because the RCS of a corner reflector is proportional to the overlapping area of ​​triangle ABC and triangle A"B"C", as shown in Figure 13(a). By changing the position of triangle A"B"C" that is overlapped with triangle ABC by changing its angle, RCS in a specific direction can be suppressed.

[0082] When the angle of the incident wave is defined as an elevation angle θ and an azimuth angle φ in the coordinate system of FIG. 13(a), the RCSσ(θ,φ) is expressed by equation (5).

[0083]

number

[0084] Here, the coordinates of the centers of gravity of triangle ABC and triangle A”B”C” are expressed by equation (6).

[0085]

number

[0086] As shown in Fig. 13(b), Fig. 14(a) and (b), the effective area A of the corner reflector is determined by the angles (θ, φ) of the triangles A”B”C”. eff It can be seen that (θ,φ) and σ change. From Fig. 13(b) and Fig. 14(a) and (b), it can be seen that a specific region is involved in the RCS in a specific direction.

[0087] Furthermore, in Fig. 15 and Fig. 16, by trimming the opening in the "Trimmed area" portion, the effective area when the incident wave is in a specific direction can be set to zero, and RCS can be suppressed. By trimming the opening in the "Trimmed area" portion in Fig. 15(a), the RCS of the trimmed portion can be set to zero, and the effective area of ​​RCS can be limited to the dot-hatched portion, as shown in Fig. 15(b). Similarly, by trimming the opening in the "Trimmed area" portion in Fig. 16(a), the RCS of the trimmed portion can be set to zero, and the effective area of ​​RCS can be limited to the dot-hatched portion, as shown in Fig. 16(b).

[0088] Fig. 17 shows the angular characteristics of RCS obtained by electromagnetic field simulation in the scatterer 11 shown in Fig. 15, and the approximate value of RCS obtained from the effective area. Since the angular characteristics obtained by electromagnetic field simulation and the approximate value of RCS obtained from the effective area are consistent, the method of suppressing RCS by reducing the aperture was verified.

[0089] In the present disclosure, based on the above verification, the RCS in a predetermined direction is controlled by controlling the opening area and opening portion of the corner reflector.

[0090] In the present disclosure, the scatterer 11 has all patterns of strong and weak reflection characteristics for each combination of multiple azimuth angles at which the ID tag 1 presents an ID, regardless of where the scatterer 11 is disposed on the ID tag 1. For example, the scatterer 11 has four patterns combining strong and weak reflection intensities for two azimuth angles, a first and a second. The four patterns are (i) having a strong reflection intensity for the first and second azimuth angles, (ii) having a strong reflection intensity for the first azimuth angle and a weak reflection intensity for the second azimuth angle, (iii) having a weak reflection intensity for the first azimuth angle and a strong reflection intensity for the second azimuth angle, and (iv) having a weak reflection intensity for the first and second azimuth angles.

[0091] In addition, in the present disclosure, the scatterer 11 has a triangular shape and its orientation is not constant. In the present disclosure, as shown in Fig. 8, not only a direction that realizes a strong reflection intensity, but also a side direction or a vertex direction realizes a strong reflection intensity. In this way, depending on the shape and arrangement direction of the scatterer 11, further patterns may be added.

[0092] In this way, the scatterers 11 are prepared for each pattern, and at each placement position on the ID tag 1, the scatterers 11 that match the pattern required for that placement position are placed.

[0093] In this case, in the arrangement method of scatterers 11 proposed in the present disclosure, each of the multiple scatterers lined up at the same distance from a first position has a common azimuth angle characteristic with respect to the first position, and each of the multiple scatterers lined up at the same distance from a second position has a common azimuth angle characteristic with respect to the second position. Here, the "azimuth angle characteristic" refers to whether a scatterer presents a strong reflection characteristic or a weak reflection characteristic with respect to a predetermined position.

[0094] When a plurality of scatterers arranged at the same distance from the first position present a value corresponding to a reflection intensity equal to or greater than a predetermined value with respect to the first position, each of the plurality of scatterers arranged at the same distance from the first position has strong reflection characteristics with respect to the first position.When a plurality of scatterers arranged at the same distance from the first position present a value corresponding to a reflection intensity less than a predetermined value with respect to the first position, each of the plurality of scatterers arranged at the same distance from the first position has weak reflection characteristics with respect to the first position.

[0095] Furthermore, a scatterer 11 that presents a value corresponding to a reflection intensity equal to or greater than a predetermined value for a first position and presents a value corresponding to a reflection intensity less than the predetermined value for a second position has a stronger reflection intensity for the first position than for the second position.

[0096] Due to these features, the reflection characteristics for the first and second positions are determined by the arrangement positions of the scatterers 11, so that the pattern of the scatterers 11 arranged at each arrangement position can be uniquely and easily specified. Also, although the case where the ID tag 1 presents two azimuth directions has been described here, the same applies to three or more directions.

[0097] A scatterer 11 that presents a value corresponding to a reflection intensity equal to or greater than a predetermined value at a first position and a value corresponding to a reflection intensity less than the predetermined value at a second position has an opening at a portion of its bottom surface close to a first direction and is covered with a metal material at a portion close to a second direction. According to the findings of the inventors, the azimuth angle characteristics of the reflection intensity are determined according to the opening state of the bottom surface of the scatterer 11. In an open state, the reflection intensity is strong, and in a covered state, the reflection intensity is nullified. By forming the scatterer 11 according to this characteristic, a scatterer 11 having desired azimuth angle characteristics can be manufactured.

[0098] An example of a method for arranging the scatterers 11 according to the present disclosure will be described with reference to Fig. 18. In the arranging method, the processes of steps S101 to S107 are performed for each position of the scatterers 11 on the ID tag 1.

[0099] In step S101, it is determined whether the azimuth angle characteristic required for the scatterer 11 placed at the position to be processed has a strong reflection intensity to the first position. Here, a strong reflection intensity to the first position specifically means that a scatterer 11 placed at a position equidistant from the first position, including the position to be processed, presents a value corresponding to a reflection intensity equal to or greater than a predetermined value. Also, a weak reflection intensity to the first position specifically means that a scatterer 11 placed at a position equidistant from the first position, including the position to be processed, presents a value corresponding to a reflection intensity less than a predetermined value.

[0100] In step S101, if the azimuth angle characteristic required for the scatterer 11 placed at the position to be processed is that the reflection intensity to the first position is strong, the process proceeds to step S102, and if it is weak, the process proceeds to step S105.

[0101] In step S102, it is determined whether the azimuth angle characteristic required for the scatterer 11 placed at the processing target position has a strong reflection intensity to the second position. If it is strong, the process proceeds to step S103, and if it is weak, the process proceeds to step S104.

[0102] In step S103, a scatterer 11 having strong reflection intensity is placed at a first position and a second position at the position to be processed. In step S104, a scatterer 11 having strong reflection intensity at the first position and weak reflection intensity at the second position is placed at the position to be processed.

[0103] In step S105, if the azimuth angle characteristic required for the scatterer 11 placed at the processing target position is that the reflection intensity to the first position is strong, the process proceeds to step S106, and if it is weak, the process proceeds to step S107.

[0104] In step S106, a scatterer 11 having a weak reflection intensity at a first position and a strong reflection intensity at a second position is placed at a processing target position. In step S07, a scatterer 11 having a weak reflection intensity is placed at the first position and the second position.

[0105] When steps S101 to S107 are completed for each position of the ID tag 1, the process ends.

[0106] According to the present disclosure, it is possible to re-emit modulated waves with different bit strings embedded therein in response to incident waves from different directions by utilizing the azimuth angle characteristics of the scatterer 11 on the ID tag 1. This allows the ID tag 1 to present different bit strings in different directions.

[0107] The present disclosure is not limited to the above-described embodiment, and various modifications are possible within the scope of the present disclosure. [Explanation of symbols]

[0108] 1 ID Tag 2. Radar 5. Measurement System 11 Scatterer

Claims

1. A plurality of scatterers are arranged two-dimensionally, Each of the plurality of scatterers has a different azimuth angle characteristic for re-radiating a radio wave irradiated from a predetermined azimuth angle with a predetermined reflection intensity, The plurality of scatterers are A combination of a plurality of scatterers located at equal distances from a first position; forming a combination of a plurality of scatterers that are equidistant from a second position that is at least different in azimuth angle from the first position with respect to the plurality of scatterers; ID tag.

2. A one-bit binary value is presented to the first position based on a sum of reflection intensities of a plurality of scatterers located at equal distances from the first position, the sum being reflected by the first position; A one-bit binary value is presented to the second position based on the sum of the reflection intensities of a plurality of scatterers located at equal distances from the second position. The ID tag according to claim 1 .

3. a first combination of a plurality of scatterers located a first distance from the first location; a second combination of a plurality of scatterers located a second distance from the first location; Presenting a two-bit binary value at said first location The ID tag according to claim 1 .

4. An ID tag; a radar that irradiates radio waves to the ID tag and acquires values ​​from a distance intensity distribution of the radio waves re-emitted from the ID tag; The ID tag is A plurality of scatterers are arranged two-dimensionally, Each of the plurality of scatterers has a different azimuth angle characteristic for re-radiating a radio wave irradiated from a predetermined azimuth angle with a predetermined reflection intensity, The plurality of scatterers are A combination of a plurality of scatterers located at equal distances from a first position; forming a combination of a plurality of scatterers that are equidistant from a second position that is at least different in azimuth angle from the first position with respect to the plurality of scatterers; Measurement system.

5. The radar acquires a first value at the first location and acquires a second value at the second location.

5. The measurement system of claim 4.

6. A method for arranging a plurality of scatterers in an ID tag, comprising the steps of: Each of the plurality of scatterers has a different azimuth angle characteristic for re-radiating a radio wave irradiated from a predetermined azimuth angle with a predetermined reflection intensity, identifying azimuth angle characteristics of each of the plurality of scatterers included in the first combination and each of the plurality of scatterers included in the second combination such that a sum of reflection intensities at a first position by the plurality of scatterers included in the first combination becomes a predetermined value, and a sum of reflection intensities at a second position by the plurality of scatterers included in the second combination becomes a predetermined value; placing each scatterer included in the first combination at a position equidistant from the first position on the ID tag; placing each scatterer included in the second combination at a position equidistant from the second position on the ID tag; The second position has a different azimuth angle with respect to the ID tag from the first position. Placement method.

7. the different azimuth angle characteristics are identified by a combination of a reflection intensity for the first position being higher or lower than a predetermined value and a reflection intensity for the second position being higher or lower than a predetermined value; In the scatterers belonging to both the first combination and the second combination, The reflection intensity for a position where the sum of the first position and the second position is equal to or greater than a predetermined value is The reflection intensity is stronger than the reflection intensity at a position where the sum of the first position and the second position is less than a predetermined value. The method of claim 6.

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