RFID Systems

Abstract

To provide an RFID system which reduces erroneous reading of an RFID tag by a simple method.SOLUTION: In an RFID system 100, a main gate 10a includes, for the purpose of reading an RFID tag, an RFID reader / writer 21, an RFID antenna 23 connected to the RFID reader / writer, and a controller 22 for controlling the RFID reader / writer. The RFID antenna comprises one or more antenna sets S(k) each of which has a first antenna member A1(k) and a second antenna member A2(k), and the first and second antenna members are arranged adjacent to each other in a passing direction of the RFID tag and are arranged with a separation angle difference so that a pair of directivity directions are separated from each other in a forward direction. The RFID reader / writer processes a detection signal of the RFID tag read with switching between the first antenna member and the second antenna member and determines whether the RFID tag has passed through the vicinity of the RFID antenna or not on the basis of a temporal change of the detection signal.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an RFID system for detecting the presence of an RFID tag attached to a product or the like, and more particularly to an RFID system that switches between and operates multiple antenna members to detect the passage of an RFID tag. [Background technology]

[0002] There are RFID systems that incorporate RFID antennas into gates to detect RFID tags that pass in front of or between gates. In such RFID systems, RFID tags located far away may be misread due to the effects of reflection or multipath, resulting in false alarms. To improve this phenomenon, a technology is known that uses radio wave reception strength and phase information to determine through data processing that an RFID tag has passed in front of a gate, thereby taking measures against misreading (Patent Document 1).

[0003] However, the above-mentioned method using phase information, etc., involves fairly complex algorithm processing, and therefore systems incorporating slow processing devices are unable to keep up with the processing, and systems incorporating high-speed processing devices have the problem that, even if they are able to reduce misreadings, they do not achieve an improvement in accuracy that is commensurate with the cost. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-37663 A Summary of the Invention

[0005] The present invention has been made in view of the above-mentioned background art, and has an object to provide an RFID system that can reduce erroneous reading of RFID tags using a simple technique.

[0006] In order to achieve the above-mentioned object, the RFID system of the present invention comprises an RFID reader / writer for reading an RFID tag, an RFID antenna connected to the RFID reader / writer, and a controller for controlling the RFID reader / writer, wherein the RFID antenna comprises one or more antenna sets having a first antenna member and a second antenna member, the first antenna member and the second antenna member being arranged adjacent to each other in the direction in which the RFID tag passes and with an angle difference between them so that the pair of directional directions move away from each other forward, and the RFID reader / writer processes the detection signal of the RFID tag read while switching between the first antenna member and the second antenna member, and identifies whether the RFID tag has passed near the RFID antenna based on changes in the detection signal over time.

[0007] According to the above RFID system, reading is performed by switching between the first antenna member and the second antenna member, which are arranged with a difference in the angle of separation so that the directivity directions are separated from each other in the front, so that even if the two antenna members are brought close to each other, a sufficient time difference can be set in terms of the change over time in the signal strength obtained from these antenna members. This makes it possible to increase the accuracy of the process of identifying the passage of an RFID tag based on the change over time in the detection signals obtained by the two antenna members, and ensure the reliability of the passage determination. Furthermore, by bringing the two antenna members close to each other, the RFID antenna can be made compact, and the size of the device or gate can be made compact.

[0008] According to a specific aspect of the present invention, in the above-mentioned RFID system, the distance from the antenna set to the cross point between the half-value angle of the radiation characteristic of the first antenna member and the half-value angle of the radiation characteristic of the second antenna member is defined as the sensitivity separation distance, and the sensitivity separation distance is 20 to 70% larger than the standard state in which the directivity directions are aligned.

[0009] According to another aspect of the present invention, the RFID reader / writer extracts a change in signal strength over time from a detection signal read through an RFID antenna, and performs a filter process on the signal strength with respect to pass characteristics including the signal strength and a peak index, thereby identifying whether or not the RF tag is a tag that has moved near the RFID antenna. In this case, since the filter process on the pass characteristics including the signal strength and the peak index is performed, the reliability of the subsequent signal determination process can be easily improved.

[0010] According to another aspect of the present invention, when performing filtering, the RFID reader / writer reduces the number of stored signal strength data to a number of data points that can ensure the reliability of filtering, thereby making it possible to perform signal evaluation processing quickly and efficiently.

[0011] According to yet another aspect of the present invention, the RFID antenna includes a plurality of antenna sets in the vicinity of the reading area, and the RFID reader / writer is connected to the plurality of antenna sets. In this case, it is possible to increase the number of connected antenna sets, which makes it easy to expand the reading area. In addition, it is possible to perform signal determination processing based on detection signals from a desired number of antenna sets, which can further increase the reliability of the passage determination.

[0012] According to yet another aspect of the present invention, an antenna switch is provided between the RFID reader / writer and the RFID antenna, which makes it possible to increase the number of antenna sets while suppressing an increase in the number of RFID reader / writers.

[0013] According to yet another aspect of the present invention, the RFID reader / writer, the RFID antenna, and the antenna switch are incorporated in the same housing. In this case, the housing and its interior can be used as a gate member.

[0014] According to yet another aspect of the present invention, a human detection infrared module is further provided to detect people passing through the reading area, and the RFID tag passing judgment is performed by combining the passing judgment of the human detection infrared module. In this case, the passing judgment of the human detection infrared module can be used as an auxiliary to increase the reliability of the judgment.

[0015] According to yet another aspect of the present invention, a human detection camera module that detects people passing through the reading area is further provided, and the RFID tag passing determination and the human detection camera module passing detection are combined to perform the determination. In this case, the reliability of the determination can be improved by utilizing the human detection camera module passing detection as an auxiliary.

[0016] According to yet another aspect of the present invention, the device further includes a database related to authentication of RFID tags. In this case, the signal of the RFID tag read by the RFID reader / writer can be authenticated at high speed without accessing a higher-level system or the like.

[0017] According to yet another aspect of the present invention, the database is a simplified database in which only objects permitted or prohibited from passing are extracted from the original database. In this case, the amount of data stored in the database can be reduced, and since there is no need to search a huge database, the processing speed of the control device can be increased.

[0018] According to yet another aspect of the present invention, an angle adjustment member for adjusting the separation angle difference is further provided. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a conceptual perspective view illustrating an RFID system according to a first embodiment. [Diagram 2] FIG. 2 is a block diagram illustrating a circuit configuration of an RFID system. [Diagram 3] 1A is a plan view illustrating an antenna set of a specific example, and FIG. 1B shows a detection pattern when an RFID tag moves in the passing direction. [Figure 4] FIG. 1A is a plan view illustrating an antenna set of a comparative example, and FIG. 1B shows a detection pattern when an RFID tag moves in the passing direction. [Diagram 5] FIG. 10 is a diagram illustrating an example of a determination operation in the RFID system. [Figure 6] 13 is a chart illustrating a modified example of the determination operation. [Figure 7] FIG. 11 is a diagram illustrating an RFID system according to a second embodiment. [Figure 8] FIG. 11 is a diagram illustrating an RFID system according to a third embodiment. [Figure 9] FIG. 13 is a plan view illustrating a modified example in which the angle of the antenna set can be adjusted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] [First embodiment] Hereinafter, an RFID system according to a first embodiment of the present invention will be described with reference to FIG.

[0021] The RFID system 100 includes a gate device 10 arranged on either side of an aisle PW, and an upper level management device 30 that manages the gate device 10. The gate device 10 includes a main gate 10a and a sub-gate 10b as a pair of gate members. The area above the aisle PW between the main gate 10a and the sub-gate 10b is a reading area DA, which is a monitored zone that detects the passage of an RFID tag TG attached to an object OB. The main gate 10a is directly connected to the upper level management device 30, and the sub-gate 10b is connected to the main gate 10a via a cable CA.

[0022] 2 is a block diagram illustrating the RFID system 100. The main gate 10a includes an RFID reader / writer 21, an RFID antenna 23 indirectly connected to the RFID reader / writer 21, an antenna switch 24 interposed between the RFID reader / writer 21 and the RFID antenna 23, and a control device 25 that controls the overall operation. The main gate 10a further includes a first infrared light source 27a, a second infrared light source 28a, and an alarm 29 that operate under the control of the control device 25. The sub-gate 10b includes the RFID antenna 23, and further includes a first infrared sensor 27b, a second infrared sensor 28b, and an alarm 29.

[0023] The RFID reader / writer 21 has a control circuit 21a including a CPU 21c and a memory 21m, and operates based on an installed program. The RFID reader / writer 21 feeds power to the RFID antenna 23, outputs radio waves in a predetermined band (specifically, for example, radio waves in the UHF band of 860 to 960 MHz), receives a response wave from the RFID tag TG passing through the passage PW, and identifies the RFID tag TG. In other words, the RFID reader / writer 21 processes the detection signal of the RFID tag TG, and identifies whether the RFID tag TG has passed near the RFID antenna 23 based on the change in the detection signal over time.

[0024] In the illustrated example, the RFID antenna 23 built into the main gate 10a includes a number of antenna sets S(1), S(2), ... S(m), which are arranged in the vicinity of the reading area DA (see FIG. 1). The first antenna set S(1) has a first antenna member A1(1) and a second antenna member A2(1), the second antenna set S(2) has a first antenna member A1(2) and a second antenna member A2(2), and the m-th antenna set S(m) has a first antenna member A1(m) and a second antenna member A2(m) arranged along the passing direction PD. The first antenna set S(1) is arranged, for example, at the bottom of the reading area DA (see FIG. 1), the second antenna member A2(2) is arranged, for example, at the top of the reading area DA, and the m-th antenna set S(m) is arranged in the middle of the reading area DA. Each antenna set S(k), where k is any natural number between 1 and m, has a first antenna member A1(k) arranged along the passing direction PD and a second antenna member A2(k) arranged along the passing direction PD. Each antenna set S(k), that is, the first antenna member A1(k) and the second antenna member A2(k), are connected to an RFID reader / writer 21. Each antenna set S(k) operates at different timings under the control of the RFID reader / writer 21. Furthermore, in each antenna set S(k), the first antenna member A1(k) and the second antenna member A2(k) are mutually switched by the RFID reader / writer 21 to operate at different timings. In this way, by switching the timings at which the antenna members A1(k) and A2(k) operate, it is possible to clearly identify and specify which antenna members A1(k) and A2(k) the RFID tag TG has responded to while avoiding the problem of interference.

[0025] The RFID antenna 23 installed in the sub-gate 10b is similar to the RFID antenna 23 installed in the main gate 10a.

[0026] The antenna switch 24 operates under the control of the RFID reader / writer 21, and selects a specific antenna member from a plurality of first antenna members A1(k) and a plurality of second antenna members A2(k) and connects it to the RFID reader / writer 21. In a specific example, in a specific antenna set S(k), the first antenna member A1(k) is connected to the RFID reader / writer 21 first, and the second antenna member A2(k) is connected to the RFID reader / writer 21 later. The RFID antenna 23 incorporated in the sub-gate 10b is connected to the antenna switch 24 incorporated in the main gate 10a, and operates at a different timing from the RFID antenna 23 incorporated in the main gate 10a.

[0027] The control device 25 is the controller 22 composed of, for example, a microcomputer. The control device 25 has a CPU 25a, a memory 25b, a communication circuit 25c, etc., and operates based on an installed program. The control device 25 manages the operating states of the RFID reader / writer 21, the infrared light sources 27a, 28a, the infrared sensors 27b, 28b, and the alarm 29, but does not need to be independent of the RFID reader / writer 21, and can be incorporated into the RFID reader / writer 21 as a function of the control circuit 21a of the RFID reader / writer 21. In this case, the RFID reader / writer 21 includes an RFID reader / writer in the narrow sense and the controller 22. The control device 25 may be a function realized by the computer of the upper management device 30 shown in FIG. 1. In this case, the RFID reader / writer 21 is directly managed by the upper management device 30.

[0028] The first infrared light source 27a and the second infrared light source 28a are fixed to a case 10f which is the housing of the main gate 10a shown in FIG. 1, and the first infrared sensor 27b and the second infrared sensor 28b are fixed to a case 10f of the sub-gate 10b.

[0029] The first infrared light source 27a operates under the control of the control device 25 or the RFID reader / writer 21, and emits light continuously or periodically. The first infrared sensor 27b detects infrared light emitted from the first infrared light source 27a. The control device 25 or the RFID reader / writer 21 detects the passage of a person or the like based on the detection result of the first infrared sensor 27b. In the above, the first infrared light source 27a and the first infrared sensor 27b function as a first person detection infrared module 27 that detects a person passing through the reading area DA. The second infrared light source 28a operates under the control of the control device 25 or the RFID reader / writer 21, and emits light continuously or periodically. The second infrared sensor 28b detects infrared light emitted from the second infrared light source 28a. The control device 25 or the RFID reader / writer 21 detects the passage of a person or the like based on the detection result of the second infrared sensor 28b. In the above, the second infrared light source 28a and the second infrared sensor 28b function as a second human detection infrared module 28 that detects a person passing through the reading area DA. First, when the first human detection infrared module 27 detects the passage of a relatively large object, and then the second human detection infrared module 28 detects the passage of a relatively large object, it is determined that an object such as a person passing forward through the passage PW has passed. That is, the control device 25 or the RFID reader / writer 21 performs a determination by combining the passage determination using the RFID tag TG and the passage detection by the human detection infrared modules 27, 28. Specifically, when the passage is determined using the RFID tag TG and the passage is determined using the human detection infrared modules 27, 28, it is determined that a person carrying the RFID tag TG has passed through the reading area DA. In this case, the reliability of the determination can be improved by auxiliary use of the passage detection by the human detection infrared modules 27, 28.

[0030] The alarm 29 includes a speaker and a lamp, and when the control device 25 or the RFID reader / writer 21 determines that an RFID tag TG is present, the alarm device 29 receives a command from the control device 25 or the RFID reader / writer to issue an alarm regarding the detection of the RFID tag TG.

[0031] 1 is connected to a server 70 having a database via a communication network. The server 70 is a device outside the RFID system 100.

[0032] FIG. 3(A) is a plan view for explaining an antenna set S(k) of a specific example. In the housing of the main gate 10a, that is, in the case 10f, a first antenna member A1(k) and a second antenna member A2(k) are incorporated as the antenna set S(k), and the first antenna member A1(k) and the second antenna member A2(k) are arranged along the passing direction PD. The first antenna member A1(k) and the second antenna member A2(k) are arranged adjacent to each other in the passing direction PD of the RFID tag TG, and are arranged with a separation angle difference α such that the directivity direction D1 of the first antenna member A1(k) and the directivity direction D2 of the second antenna member A2(k) are separated from each other in the front. More specifically, the directivity direction D1 of the first antenna member A1(k) is inclined counterclockwise with respect to the front direction, and the directivity direction D2 of the second antenna member A2(k) is inclined clockwise with respect to the front direction. The separation angle difference α can reduce the area where the sensitivity area of ​​the first antenna member A1(k) and the sensitivity area of ​​the second antenna member A2(k) overlap in the reading area DA. On the other hand, if the separation angle difference α is increased and the sensitivity area of ​​the first antenna member A1(k) and the sensitivity area of ​​the second antenna member A2(k) are excessively separated, the thickness of the RFID antenna 23 increases, making it difficult to detect the RFID tag TG moving from in front of the first antenna member A1(k) to in front of the second antenna member A2(k) with a time difference of about the moving distance, and it becomes difficult to obtain a detection signal with sufficient strength. The degree of separation between the first antenna member A1(k) and the second antenna member A2(k) can be measured using a scale called the sensitivity separation distance SD. The sensitivity separation distance SD is given as the distance from the antenna set S(k) to the cross point XP between the half-value angle θ of the radiation characteristic of the first antenna member A1(k) and the half-value angle θ of the radiation characteristic of the second antenna member A2(k).

[0033] Fig. 3(B) shows a detection pattern when an RFID tag TG moves in a passing direction PD along a passage PW when the first antenna member A1(k) and the second antenna member A2(k) are arranged as shown in Fig. 3(A). A detection peak PK2 of the second antenna member A2(k) is detected after a detection peak PK1 of the first antenna member A1(k), and both detection peaks PK1, PK2 are sufficiently separated in the direction of the time axis, making it possible to set a sufficient time difference with respect to the change over time in the signal strength obtained from these antenna members A1(k) and A2(k).

[0034] Fig. 4(A) is a plan view for explaining an antenna set S(k) of a comparative example. In this case, the first antenna member A1(k) and the second antenna member A2(k) are arranged adjacent to each other in the passing direction PD of the RFID tag TG, but the directivity direction D1 of the first antenna member A1(k) and the directivity direction D2 of the second antenna member A2(k) are set parallel to each other, and the separation angle difference α is zero. As shown in Fig. 4(A), when the directivity direction D1 of the first antenna member A1(k) and the directivity direction D2 of the second antenna member A2(k) are parallel to each other, the sensitivity separation distance SD corresponding to the state in which the directivity direction D1 of the first antenna member A1(k) and the directivity direction D2 of the second antenna member A2(k) are separated from each other is about 30% larger than the sensitivity separation distance SD0. In addition, by making the sensitivity separation distance SD about 20% or more larger than the sensitivity separation distance SD0 of the comparative example, it is possible to prevent the overlapping area between the sensitivity area of ​​the first antenna member A1(k) and the sensitivity area of ​​the second antenna member A2(k) from becoming too large. In addition, by making the sensitivity separation distance SD about 70% or less larger than the sensitivity separation distance SD0 of the comparative example, it is possible to avoid a timing difference becoming large and processing delays occurring due to an excessive separation between the sensitivity areas of the first antenna member A1(k) and the second antenna member A2(k).

[0035] Fig. 4(B) shows a detection pattern when the RFID tag TG moves in the passage direction PD along the passage PW when the first antenna member A1(k) and the second antenna member A2(k) are arranged as shown in Fig. 4(A). A detection peak PK2 of the second antenna member A2(k) is detected after a detection peak PK1 of the first antenna member A1(k), but the two detection peaks PK1, PK2 are not sufficiently separated in the direction of the time axis, and a sufficient time difference cannot be set with respect to the change over time in the signal strength obtained from these antenna members A1(k) and A2(k).

[0036] 5 is a diagram for explaining an example of a judgment operation in the RFID system 100. The CPU 21c of the RFID reader / writer 21 judges whether or not the signal strength P1 exceeds a predetermined threshold value V1 stored in the memory 21m with respect to a series of responses from the specific RFID tag TG obtained using the first antenna member A1(k) (step S10). Next, the CPU 21c judges whether or not the number of data points (points) DP1 of the signal strength P1 increasing to the right with respect to a series of responses from the specific RFID tag TG obtained using the first antenna member A1(k) exceeds a predetermined threshold value V2 stored in the memory 21m (step S11). Next, the CPU 21c comprehensively judges the time-dependent change characteristics of the signal strength P1 with respect to a series of responses from the specific RFID tag TG obtained using the first antenna member A1(k), and judges whether or not the peak value P1max in the time-dependent change characteristics exceeds a predetermined threshold value V3 stored in the memory 21m (step S12). Next, the CPU 21c comprehensively judges the time-dependent change characteristic of the signal strength P1 with respect to a series of responses from the specific RFID tag TG obtained using the first antenna member A1(k), and judges whether or not the difference between the peak value P1max and the average value P1ave in the time-dependent change characteristic exceeds a predetermined threshold value V4 stored in the memory 21m (step S13). Next, the CPU 21c comprehensively judges the time-dependent change characteristic of the signal strength P1 with respect to a series of responses from the specific RFID tag TG obtained using the first antenna member A1(k), and judges whether or not the kurtosis P1S of the time-dependent change characteristic exceeds a predetermined threshold value V5 stored in the memory 21m (step S14). Here, the time-dependent change characteristic of the signal strength P1 may be a line graph in which the detection points are connected by a line segment, or may be a curve fitted to the detection points. The kurtosis P1S means the increase amount at the point where the increase amount of the signal strength P1 per unit time is maximum in the time-dependent change characteristic, that is, the maximum slope.

[0037] If the determination is Yes in the above steps S10 to S14, assuming that the detection RFID tag TG has been detected with a certain degree of reliability or higher by the first antenna member A1(k), the CPU 21c of the RFID reader / writer 21 determines whether or not the signal strength P2 of the series of responses from the specific RFID tag TG obtained using the second antenna member A2(k) exceeds a certain threshold value V1 stored in the memory 21m (step S15). Next, the CPU 21c determines whether or not the number of data points (points) DP2 of the signal strength P2 increasing to the right exceeds a certain threshold value V2 stored in the memory 21m (step S16). Next, the CPU 21c comprehensively judges the time-dependent change characteristics of the signal strength P2 for a series of responses from the specific RFID tag TG obtained using the second antenna member A2(k), and judges whether the peak value P2max in the time-dependent change characteristics exceeds a predetermined threshold value V3 stored in the memory 21m (step S17). Next, the CPU 21c comprehensively judges the time-dependent change characteristics of the signal strength P2 for a series of responses from the specific RFID tag TG obtained using the second antenna member A2(k), and judges whether the difference between the peak value P2max and the average value P2ave in the time-dependent change characteristics exceeds a predetermined threshold value V4 stored in the memory 21m (step S18). Next, the CPU 21c comprehensively judges the time-dependent change characteristics of the signal strength P2 for a series of responses from the specific RFID tag TG obtained using the second antenna member A2(k), and judges whether the kurtosis P2S of the time-dependent change characteristics exceeds a predetermined threshold value V5 stored in the memory 21m (step S19).

[0038] If the determination is Yes in the above steps S15 to S19, the CPU 21c of the RFID reader / writer 21 performs a comprehensive determination assuming that the RFID tag TG has been detected with a certain degree of reliability or higher by the second antenna member A2(k). That is, the CPU 21c determines whether or not the absolute value of the difference between the peak value P1max in the time-varying characteristic including a series of responses from the specific RFID tag TG obtained using the first antenna member A1(k) and the peak value P2max in the time-varying characteristic including a series of responses from the specific RFID tag TG obtained using the second antenna member A2(k) exceeds a predetermined threshold value V6 stored in the memory 21m (step S20). In addition, the CPU 21c determines whether the difference between the occurrence time P2T of the peak value P2max in the time-varying characteristic obtained using the second antenna member A2(k) and the occurrence time P1T of the peak value P1max in the time-varying characteristic obtained using the first antenna member A1(k) exceeds a predetermined threshold value V7 stored in the memory 21m (step S21).

[0039] If it is determined in step S20 that the difference in peak values ​​|P1max-P2max| is smaller than the predetermined threshold value V6 and if it is determined in step S21 that the difference in peak occurrence times P2T-P1T is smaller than the threshold value V7, the CPU 21c of the RFID reader / writer 21 determines that the detected RFID tag TG is a moving tag and determines that this RFID tag TG has passed through the reading area DA, which is a gate, on the premise that the same RFID tag TG can be detected with sufficient reliability (step S22). On the other hand, if it is determined in step S20 that the difference in peak values ​​|P1max-P2max| is larger than the predetermined threshold value V6 or if it is determined in step S21 that the difference in peak occurrence times P2T-P1T is larger than the threshold value V7, the CPU 21c of the RFID reader / writer 21 determines that the detected RFID tag TG is a stationary tag and determines that this RFID tag TG has not passed through the reading area DA, which is a gate (step S23).

[0040] In the above steps S10 to S14, comparing the signal strength P1, the number of data DP1 with a right-sloping trend, the peak value P1max, the peak average difference P1max-P1ave (the difference between the peak value P1max and the average value P1ave), and the kurtosis P1S with a predetermined threshold value and making a judgment corresponds to extracting a change in the signal strength over time and performing a filter process on the signal strength with respect to the pass characteristic including the signal strength and the peak index. Similarly, in the above steps S15 to S19, comparing the signal strength P2, the number of data DP2 with a right-sloping trend, the peak value P2max, the peak average difference P2max-P2ave (the difference between the peak value P2max and the average value P2ave), and the kurtosis P2S with a predetermined threshold value and making a judgment corresponds to extracting a change in the signal strength over time and performing a filter process on the signal strength with respect to the pass characteristic including the signal strength and the peak index. Furthermore, judging the difference P2T-P1T of the peak occurrence times and the difference |P1max-P2max| of the peak values ​​also corresponds to performing a filter process.

[0041] FIG. 6 is a diagram for explaining a modified example of the judgment operation. In the chart, the time-dependent change characteristic of the signal strength, which is a series of responses from the specific RFID tag TG obtained using the first antenna member A1(k), is actual measurement data including 12 measurement points. Also, the time-dependent change characteristic of the signal strength, which is a series of responses from the specific RFID tag TG obtained using the second antenna member A2(k), is actual measurement data including 15 measurement points and is stored data. The actual measurement data is simplified by thinning out to simplify the processing, and judgment target data with fewer data points is used to judge the passage of the specific RFID tag TG. Specifically, the judgment target data related to the first antenna member A1(k) and the second antenna member A2(k) is obtained by leaving only three points, the start point, the maximum point, and the end point, from the waveform, which is the time-dependent change characteristic. Note that the judgment target data is displayed at a position shifted upward in terms of intensity on the chart for convenience of explanation. In this way, by using the judgment target data that has been simplified by thinning out and has fewer data points, the signal judgment process can be made quick and efficient.

[0042] In the above explanation, the RFID system 100 includes a main gate 10a and a sub-gate 10b arranged on either side of the passage PW, but the RFID system 100 may be of a non-gated type in which devices including circuits and antennas similar to those of the main gate 10a, i.e., an RFID reader / writer 21 and an RFID antenna 23, are arranged near one side of the passage PW or the reading area DA.

[0043] In the above description, the antenna switch 24 is interposed between the RFID reader / writer 21 and the RFID antenna 23, but the antenna switch 24 can be omitted. In this case, the RFID reader / writer 21 detects the RFID tag TG by switching between the first antenna member A1(k) and the second antenna member A2(k) constituting the RFID antenna 23.

[0044] The RFID system 100 of the first embodiment described above includes an RFID reader / writer 21 for reading an RFID tag TG, an RFID antenna 23 connected to the RFID reader / writer 21, and a controller 22 for controlling the RFID reader / writer 21. The RFID antenna 23 includes one or more antenna sets S(k) having a first antenna member A1(k) and a second antenna member A2(k). The first antenna member A1(k) and the second antenna member A2(k) are arranged adjacent to each other in the passing direction of the RFID tag TG and are arranged with a separation angle difference α such that a pair of directivity directions D1, D2 move away from each other in the front. The RFID reader / writer 21 processes a detection signal of the RFID tag TG read while switching between the first antenna member A1(k) and the second antenna member A2(k), and identifies whether the RFID tag TG has passed near the RFID antenna 23 based on a change in the detection signal over time.

[0045] According to the RFID system 100, reading is performed by switching between the first antenna member A1(k) and the second antenna member A2(k), which are arranged with a separation angle difference α so that the directivity directions D1 and D2 are separated from each other in the front, so that even if the two antenna members A1(k) and A2(k) are brought close to each other, a sufficient time difference can be set for the change over time in the signal strength obtained from these antenna members A1(k) and A2(k). This makes it possible to increase the accuracy of the process of identifying the passage of the RFID tag TG based on the change over time in the detection signal obtained by the two antenna members, and ensure the reliability of the passage determination. In addition, by bringing the two antenna members A1(k) and A2(k) close to each other, the RFID antenna 23 can be made compact, and the size of the device and gate can be made compact.

[0046] [Second embodiment] Hereinafter, the RFID system of the second embodiment will be described with reference to Fig. 7. The RFID system of the second embodiment is a partial modification of the RFID system of the first embodiment, and the same parts are denoted by the same reference numerals and will not be described again.

[0047] 7, at the main gate 10a of the RFID system 100, a camera 51 is provided for photographing a reading area DA above the passage PW.

[0048] The camera 51 is driven by the control device 25 to capture an image of the reading area DA above the passage PW, extracts an image of a person passing through the passage PW by image processing, and determines whether or not a person has passed through the passage PW. In other words, the camera 51 and the control device 25 function as a human detection camera module 50 that detects a person passing through the reading area DA. The RFID system 100 makes a determination by combining the passage determination of the RFID tag TG by the RFID reader / writer 21 and the passage detection by the human detection camera module 50.

[0049] In the RFID system 100 of the second embodiment, a judgment is made by combining the passage judgment of the RFID tag TG with the passage detection of the human detection camera module 50, so that the passage detection of the human detection camera module 50 can be used as an auxiliary to increase the reliability of the judgment.

[0050] [Third embodiment] Hereinafter, an RFID system according to the third embodiment will be described with reference to Fig. 8. The RFID system according to the third embodiment is a partial modification of the RFID system according to the first embodiment, and the same parts are denoted by the same reference numerals and will not be described again.

[0051] 8, a database 25u is incorporated in the control device 25 at the main gate 10a of the RFID system 100. The database 25u processes and manages unique information relating to the ID and the like of the RFID tag TG read by the RFID reader / writer 21 without accessing a higher-level system. In this case, high-speed authentication is possible only by the main body of the main gate 10a, etc., and there is no need to perform a query request process for authentication to the higher-level management device 30 or server 70.

[0052] In a normal RFID system 100, the host management device 30 is essential for authentication, and data related to authentication must be collated with the server 70 via the host management device 30. When the data read by the RFID reader / writer 21 is subjected to a process of requesting a query for authentication to the server 70 via the host management device 30, if the amount of data is large, there is a problem that it takes time to collate. In addition, in order to realize such a process, it becomes necessary to make the software of the host management device 30 compatible, which makes the host management device 30 complicated. In response to this, by incorporating a database 25u in the control device 25 of the main gate 10a and limiting the data held in the control device 25 to the minimum data necessary for authentication, there is no need to collate with the host system when reading the tag, and the load on the host system is very small, and the RFID system 100 alone can realize the collation.

[0053] There are two methods for incorporating the database 25u in the RFID system 100, as follows. (1) Case where a simple database is built in The simple database stores the minimum necessary data. (2) Case where a complete database is built in The complete database literally stores data that is equivalent to or close to the original database in the host system server. If an LCD display is provided at the main gate 10a to display the read data, data equivalent to that in the host system server is required.

[0054] For example, when the RFID system 100 is used for library lending management, the simplified database 25u stores only data for which lending processing has been completed, and the system issues an alert for RFID tags TG attached to books for which no data is available.When applied to a retail store, the simplified database 25u stores only purchased product data, and issues an alert for products with unregistered RFID tags TG attached.

[0055] The data stored in the simplified database 25u is not limited to whitelist data (data that does not trigger an alert) and can be blacklist data (data that triggers an alert). When the simplified database 25u is incorporated in the control device 25, the amount of data stored in the database 25u can be reduced by limiting the data to the minimum amount necessary for authentication, and since there is no need to search an enormous database, the processing speed of the control device 25 can be increased.

[0056] Although not illustrated, the database 25u described above can be incorporated in the RFID reader / writer 21 instead of the control device 25, or can be incorporated as a circuit independent of the control device 25 or the RFID reader / writer 21.

[0057] As shown in FIG. 9, the first antenna member A1(k) and the second antenna member A2(k) can be installed so that the angle can be adjusted. A hinge 10h is provided between the frame member 10fa to which the first antenna member A1(k) is attached and the frame member 10fb to which the second antenna member A2(k) is attached, and an angle fixing member 10k is provided in association with the hinge 10h. The hinge 10h and the angle fixing member 10k function as an angle adjustment member 10x that adjusts the separation angle difference α. The pair of frame members 10fa and 10fb are housed in the case 10f and are allowed to change in angle, and can be in a state shown by a solid line or a dotted line, for example. This allows the pair of directivity directions D1 and D2 to be adjusted, and the separation angle difference α can be increased or decreased. By adjusting the separation angle difference α, the time difference between the detection peaks PK1 and PK2 shown in FIG. 3(B), that is, the separation, can be adjusted.

[0058] Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment. The RFID system 100 enables management of the taking out of books in a library, for example, but is not limited to this. [Explanation of symbols]

[0059] A1(k)...first antenna member, A2(k)...second antenna member, D1, D2...direction of directivity, DA...reading area, OB...target, P1, P2...signal strength, P1max, P2max...peak value, P1S, P2S...kurtosis, P1T, P2T...occurrence time, PK1, PK2...detection peak, PW...passage, PD...passage direction, S(k)...antenna set, SD...sensitivity separation distance, TG...RFID tag, XP...cross point, α...separation angle difference, θ...half-value angle, 10...gate device, 10a...main gate, 10b...sub-gate, 10f...case, 10fa, 10fb...frame member, 10h...hinge, 10k...angle fixing member, 10x...angle adjustment member, 20...host management device, 21...RFID reader / writer, 21a...control circuit, 22...controller, 23...RFID antenna, 24...antenna switch, 25...control device, 25u...database, 27, 28...human detection infrared module, 27a, 28a...infrared light source, 27b, 28b...infrared sensor, 29...alarm, 30...host management device, 50...human detection camera module, 51...camera, 70...server, 100...RFID system

Claims

1. The device includes an RFID reader / writer for reading an RFID tag, an RFID antenna connected to the RFID reader / writer, and a controller for controlling the RFID reader / writer; the RFID antenna comprises one or more antenna sets having a first antenna member and a second antenna member; the first antenna member and the second antenna member are disposed adjacent to each other in a passing direction of the RFID tag and are disposed with a separation angle difference such that a pair of directivity directions are separated from each other in a forward direction, The RFID reader / writer processes the detection signal of the RFID tag read while switching between the first antenna member and the second antenna member, and identifies whether the RFID tag has passed near the RFID antenna based on a change in the detection signal over time.

2. The RFID system of claim 1, wherein a sensitivity separation distance is a distance from the antenna set to a cross point between a half-value angle of the radiation characteristic of the first antenna member and a half-value angle of the radiation characteristic of the second antenna member, and the sensitivity separation distance is 20 to 70% larger than a standard state in which the directivity directions are aligned.

3. The RFID system of claim 1, wherein the RFID reader / writer extracts changes in signal strength over time from the detection signal read via the RFID antenna, and performs filter processing on the signal strength with respect to pass characteristics including signal strength and peak index, thereby identifying whether the RF tag is a tag that has moved near the RFID antenna.

4. 4. The RFID system according to claim 3, wherein, when performing the filtering process, the RFID reader / writer reduces the stored data of the signal strength to a number of data points that can ensure the reliability of the filtering process.

5. The RFID antenna includes a plurality of antenna sets in the vicinity of a reading area; The RFID system according to claim 1 , wherein the RFID reader / writer is connected to a plurality of the antenna sets.

6. The RFID system according to claim 5 , further comprising an antenna switch interposed between the RFID reader / writer and the RFID antenna.

7. The RFID system according to claim 6 , wherein the RFID reader / writer, the RFID antenna, and the antenna switch are incorporated in a single housing.

8. Further comprising a human detection infrared module for detecting a person passing through the reading area; The RFID system according to claim 1 , wherein the determination is made by combining the determination of passage of the RFID tag with the detection of passage of a human detection infrared module.

9. Further comprising a human detection camera module for detecting a person passing through the reading area; The RFID system according to claim 1 , wherein the determination is made by combining the determination of passage of the RFID tag with the detection of passage of a human detection camera module.

10. The RFID system of claim 1 further comprising a database related to authentication of the RFID tags.

11. The RFID system according to claim 10, wherein the database is a simplified database in which only objects permitted or prohibited from passing are extracted from the original database.

12. The RFID system according to claim 1 , further comprising an angle adjustment member for adjusting the separation angle difference.

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