RFID system

Abstract

The purpose of the present invention is to provide an RFID system capable of reducing misreading of an RFID tag by a simple technique. In order to read an RFID tag, the RFID system includes an RFID reader / writer, an RFID antenna connected to the RFID reader / writer, and a controller that controls the RFID reader / writer. The RFID antenna includes one or more antenna groups including a first antenna member and a second antenna member. The first and second antenna members are arranged adjacent to each other in a passing direction of the RFID tag with a divergence angle difference that diverges their optical axis directions forward to each other. The RFID reader / writer processes a detection signal retrieved from the RFID tag while selectively operating the first and second antenna members, and determines whether the RFID tag has passed beside the RFID antenna based on a temporal change in the detection signal.

Description

Technical Field

[0001] The present invention relates to an RFID system that detects the presence of an RFID tag attached to a product or the like, and more particularly, to an RFID system that detects the passage of an RFID tag by selectively operating a plurality of antenna members. Background Art

[0002] Some RFID systems incorporate RFID antennas into gates to detect RFID tags passing in front of or between gates. Due to reflections and multipath effects, these systems can misread RFID tags located far away, leading to false alarms. To address this phenomenon, a known anti-misreading technology uses data processing to detect the passage of RFID tags in front of a gate using information about the intensity and phase of received radio waves (Patent Document 1).

[0003] However, since the above-mentioned method using phase information involves a relatively complex algorithmic process, a system with a slow processor may not be able to execute the process in a timely manner. Although a system with a high-speed processor can reduce misreading, there is a problem that the improvement in accuracy is not commensurate with the cost of such a system.

[0004] Prior art literature Patent Literature Patent Document 1: JP2013-37633A Summary of the Invention

[0005] The present invention has been developed in view of the above background technology. An object of the present invention is to provide an RFID system that can reduce erroneous RFID tag reading using a simple technique.

[0006] To achieve the above-mentioned object, the RFID system according to the present invention includes an RFID reader / writer, an RFID antenna connected to the RFID reader / writer, and a controller for controlling the RFID reader / writer for reading RFID tags. The RFID antenna includes one or more antenna groups, which include a first antenna component and a second antenna component. The first and second antenna components are arranged adjacent to each other in the direction of passage of the RFID tag with a divergence angle difference, and the divergence angle difference causes their visual axis directions to diverge forward from each other. The RFID reader / writer processes the detection signal retrieved from the RFID tag while selectively operating the first and second antenna components, and determines whether the RFID tag has passed by the RFID antenna based on the time change of the detection signal.

[0007] The aforementioned RFID system performs reading by selectively operating first and second antenna components, which are arranged with a divergence angle difference that causes their visual axis directions to diverge forward from each other. Consequently, the aforementioned RFID system ensures a sufficient time difference between the temporal changes in signal strength obtained from the two antenna components, even when these components are closely positioned. This improves the accuracy of detecting the passage of an RFID tag based on the temporal changes in the detection signals obtained by the two antenna components, thereby ensuring the reliability of passage detection. It should be noted that placing the two antenna components closely together allows for a compact RFID antenna, which in turn makes the entire device or gate compact. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a conceptual perspective view showing an RFID system according to a first embodiment; Figure 2 is a block diagram showing a circuit configuration of an RFID system; Figure 3A is a plan view showing an antenna group of a specific example, and Figure 3B shows the detection pattern when the RFID tag moves in the passing direction; Figure 4A is a plan view showing an antenna group of a comparative example, and Figure 4B shows the detection pattern when the RFID tag moves in the passing direction; Figure 5 is a diagram showing one example of a detection operation of an RFID system; Figure 6 is a diagram showing a modified example of the detection operation; Figure 7 is a diagram showing an RFID system according to a second embodiment; Figure 8 is a diagram showing an RFID system according to a third embodiment; Figure 9 is a plan view showing a modified example that allows angle adjustment of an antenna group. DETAILED DESCRIPTION

[0009] [First embodiment] Reference below Figure 1 A description is given of an RFID system according to a first embodiment of the present invention.

[0010] The RFID system 100 includes gate devices 10 arranged on either side of a passageway PW, and an advanced management device 30 that manages the gate devices 10. The gate devices 10 include a pair of gate members: a main gate 10a and a sub-gate 10b. The area above passageway PW between the main gate 10a and the sub-gate 10b is designated as a read area DA, a monitoring area for detecting the passage of RFID tags TG attached to objects OB. The main gate 10a is directly connected to the advanced management device 30, while the sub-gate 10b is connected to the main gate 10a via a cable CA.

[0011] Figure 2 is a block diagram showing an 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 coupled between the RFID reader / writer 21 and the RFID antenna 23, and a control device 25 that manages the overall operation. The RFID reader / writer 21, the RFID antenna 23, the antenna switch 24, and the control device 25 are housed in a single housing (i.e., housing 10f). In this case, the housing 10f and its internal components can be used as a gate member. The main gate 10a also includes a first infrared light source 27a, a second infrared light source 28a, and an alarm unit 29, which operate under the control of the control device 25. The sub-gate 10b includes an RFID antenna 23, and also includes a first infrared sensor 27b, a second infrared sensor 28b, and an alarm unit 29.

[0012] The RFID reader / writer 21 includes a control circuit 21a including a CPU 21c and a memory 21m, and operates based on an installed program. The RFID reader / writer 21 supplies power to the RFID antenna 23, causing the RFID antenna 23 to transmit radio waves within a predetermined band (specifically, for example, radio waves in the UHF band of 860 to 960 MHz). The RFID reader / writer 21 then receives a response wave from an RFID tag TG passing through the channel PW, thereby identifying the RFID tag TG. In other words, the RFID reader / writer 21 processes the detection signal from the RFID tag TG and determines whether the RFID tag TG has passed by the RFID antenna 23 based on the temporal change in the detection signal.

[0013] In the example shown, the RFID antenna 23 included in the main gate 10a includes a plurality of antenna groups S(1), S(2), ..., and S(m), where m is a natural number greater than or equal to 3. The antenna groups S(1), S(2), ..., and S(m) are arranged beside the reading area DA (see Figure 1). The RFID antenna 23 includes a plurality of antenna groups S(1), S(2), ... next to the reading area DA, and the RFID reader / writer is connected to these plurality of antenna groups. This configuration allows the number of antenna groups S(1), S(2), ... to be increased, thereby facilitating the expansion of the reading area. In addition, this configuration enables signal determination processing based on signals detected by a desired number of antenna groups S(1), S(2), ..., thereby enhancing the reliability of through detection.

[0014] The first antenna group S(1) includes a first antenna member A1(1) and a second antenna member A2(1), the second antenna group S(2) includes a first antenna member A1(2) and a second antenna member A2(2), and the mth antenna group S(m) includes a first antenna member A1(m) and a second antenna member A2(m) arranged along the pass direction PD. The first antenna group S(1) is arranged at, for example, the bottom of the reading area DA (see FIG. Figure 1 ), the second antenna member A2(2) is arranged at, for example, the top of the reading area DA, and the mth antenna group S(m) is arranged in the middle of the reading area DA. Each antenna group S(k) (where k is any natural number from 1 to m) includes 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 group (S(k)) - that is, the first antenna (A1(k)) and the second antenna (A2(k)) - is connected to the RFID reader / writer 21. Each antenna group S(k) operates at different timings under the control of the RFID reader / writer 21. In addition, within each antenna group S(k), the first antenna member A1(k) and the second antenna member A2(k) are selectively operated by the RFID reader / writer 21 to operate at different timings. As described above, operating the antenna members A1(k) and A2(k) at different timings makes it possible to clearly identify and specify to which of the antenna members A1(k) and A2(k) the RFID tag TG has responded while avoiding the problem of interference.

[0015] The configuration of the RFID antenna 23 installed in the sub-gate 10b is similar to that of the RFID antenna 23 installed in the main gate 10a.

[0016] 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) to be connected to the RFID reader / writer 21. In a specific example, in a specific antenna group S(k), the first antenna member A1(k) is first connected to the RFID reader / writer 21, and then the second antenna member A2(k) is connected to the RFID reader / writer 21. The RFID antenna 23 included in the sub-gate 10b is connected to the antenna switch 24 included in the main gate 10a and operates at a timing different from that of the RFID antenna 23 included in the main gate 10a. Providing the antenna switch 24 between the RFID reader / writer 21 and the RFID antenna 23 makes it possible to increase the number of antenna groups S(1), S(2), ... while preventing an increase in the number of RFID readers / writers 21.

[0017] The control device 25 is, for example, a microcomputer-based controller 22. The control device 25 includes a CPU 25a, a memory 25b, and a communication circuit 25c, 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 unit 29. The control device 25 does not need to be separated from the RFID reader / writer 21 and may 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 a narrow sense of the RFID reader / writer and the controller 22. The control device 25 may be a Figure 1 The functions shown are performed by the computer of the high-level management device 30. In this case, the RFID reader / writer 21 is directly managed by the high-level management device 30.

[0018] The first infrared light source 27a and the second infrared light source 28a are fixed to the housing 10f. The housing 10f is Figure 1 The outer shell of the main gate 10a is shown, and the first infrared sensor 27b and the second infrared sensor 28b are fixed to the housing 10f of the sub-gate 10b.

[0019] 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 the 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 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 the first person detection infrared module 27, which 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 the infrared light emitted from the first infrared light source 28a. The control device 25 or the RFID reader / writer 21 detects the passage of a person 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 the second person detection infrared module 28, which detects a person passing through the reading area DA. When the passage of a relatively large object is first detected by the first person detection infrared module 27 and then by the second person detection infrared module 28, it is determined that the human-like object has advanced through passage PW. In other words, the control device 25 or RFID reader / writer 21 makes this determination based on a combination of passage detection using the RFID tag TG and passage detection by the person detection infrared modules 27 and 28. Specifically, when passage is detected using the RFID tag TG and also by the person detection infrared modules 27 and 28, the control device 25 or RFID reader / writer 21 determines that the person carrying the RFID tag TG has passed through the read area DA. In this case, the reliability of this determination can be improved by supplementing the passage detection using the person detection infrared modules 27 and 28.

[0020] The alarm unit 29 includes a speaker and a lamp. When the control device 25 or the RFID reader / writer 21 determines that the RFID tag TG exists, the alarm unit 29 issues an alarm regarding the detection of the RFID tag TG in response to a command from the control device 25 or the RFID reader / writer.

[0021] Figure 1 The high-level management device 30 is shown connected to a server 70 having a database via a communication network. The server 70 is a device external to the RFID system 100.

[0022] Figure 3Ais a plan view illustrating an antenna group S(k) in a specific example. The outer shell of the main gate 10a, or housing 10f, houses therein a first antenna element A1(k) and a second antenna element A2(k), which form the antenna group S(k). The first antenna element A1(k) and the second antenna element A2(k) are arranged along the passage direction PD. The first antenna element A1(k) and the second antenna element A2(k) are arranged adjacent to each other in the passage direction PD of the RFID tag TG and have a divergence angle difference α such that the visual axis direction D1 of the first antenna element A1(k) and the visual axis direction D2 of the second antenna element A2(k) diverge forward from each other. More specifically, the visual axis direction D1 of the first antenna element A1(k) is tilted counterclockwise relative to the front direction, while the visual axis direction D2 of the second antenna element A2(k) is tilted clockwise relative to the front direction. The divergence angle difference α is adjusted to reduce the partial overlap between the sensing areas of the first antenna element A1(k) and the second antenna element A2(k) in the read area DA. Excessive separation between the sensing areas of the first antenna element A1(k) and the second antenna element A2(k) due to a large divergence angle difference α increases the thickness of the RFID antenna 23, making it difficult to detect an RFID tag TG moving from in front of the first antenna element A1(k) to in front of the second antenna element A2(k) with a time difference approximately corresponding to the travel distance, and also making it difficult to obtain a sufficiently strong detection signal. The degree of separation between the first and second antenna elements A1(k) and A2(k) can be measured using the sensitivity separation distance SD as a metric. The sensitivity separation distance SD is given as the distance between the antenna group S(k) and the intersection point XP between the half-value angle θ of the radiation characteristic of the first antenna element A1(k) and the half-value angle θ of the radiation characteristic of the second antenna element A2(k).

[0023] Figure 3B The figure shows the situation when the RFID tag TG moves in the passing direction PD along the channel PW. Figure 3A The detection pattern of the arrangement of the first antenna member A1(k) and the second antenna member A2(k) is shown. The detection peak PK2 of the second antenna member A2(k) is detected with a delay after the detection peak PK1 of the first antenna member A1(k), and the two detection peaks PK1 and PK2 are sufficiently separated along the time axis. This provides a sufficient time difference for the temporal changes in the signal strengths obtained from these antenna members A1(k) and A2(k).

[0024] Figure 4A: is a plan view showing an antenna group S(k) of a comparative example. This configuration corresponds to a standard state in which 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, with their visual axis directions oriented in the same direction. In the standard state, the visual axis direction D1 of the first antenna member A1(k) and the visual axis direction D2 of the second antenna member A2(k) are set to be parallel, resulting in a divergence angle difference α of zero. Using the Figure 4A The sensitivity separation distance SD0 in the case where the visual axis direction D1 of the first antenna member A1(k) and the visual axis direction D2 of the second antenna member A2(k) are parallel is used as a reference. Figure 3A The sensitivity separation distance SD in the illustrated state, where the visual axis direction D1 of the first antenna member A1(k) and the visual axis direction D2 of the second antenna member A2(k) are offset from each other, is approximately 30% greater than the sensitivity separation distance SD0 corresponding to the standard state. In other words, SD ≈ 1.3 × SD0. Increasing the sensitivity separation distance SD by approximately 20% or more compared to the sensitivity separation distance SD0 of the comparative example prevents excessive overlap between the sensing areas of the first antenna member A1(k) and the second antenna member A2(k). At the same time, increasing the sensitivity separation distance SD by approximately 70% or less compared to the sensitivity separation distance SD0 of the comparative example avoids significant timing differences and processing delays caused by excessive separation between the sensing areas of the first antenna member A1(k) and the second antenna member A2(k).

[0025] Figure 4B The figure shows the situation when the RFID tag TG moves in the passing direction PD along the channel PW. Figure 4A Detection pattern of the arrangement of the first antenna member A1(k) and the second antenna member A2(k) is shown. Although the detection peak PK2 of the second antenna member A2(k) is detected delayed after the detection peak PK1 of the first antenna member A1(k), the two detection peaks PK1 and PK2 are not sufficiently separated along the time axis, resulting in insufficient time difference in the temporal change of the signal strength obtained from the two antenna members A1(k) and A2(k).

[0026] Figure 5is a diagram illustrating an example of a determination operation in the RFID system 100. The CPU 21c of the RFID reader / writer 21 determines whether the signal strength P1 of a series of responses from a specific RFID tag TG obtained using the first antenna element A1(k) exceeds a predetermined threshold value V1 stored in the memory 21m (step S10). Subsequently, the CPU 21c determines whether the number D1 of data points having increasing signal strength P1 for the series of responses from the specific RFID tag TG obtained using the first antenna element A1(k) exceeds a predetermined threshold value V2 stored in the memory 21m (step S11). Subsequently, the CPU 21c comprehensively evaluates the temporal change characteristics of the signal strength P1 of the series of responses from the specific RFID tag TG obtained using the first antenna element A1(k) and determines whether the peak value P1max in the temporal change characteristics exceeds a predetermined threshold value V3 stored in the memory 21m (step S12). Subsequently, the CPU 21c determines whether the difference between the peak value P1max and the average value P1ave in the time-varying characteristics exceeds a predetermined threshold value V4 stored in the memory 21m by comprehensively evaluating the time-varying characteristics of the signal strength P1 of a series of responses obtained from the specific RFID tag TG using the first antenna member A1(k) (step S13). Subsequently, the CPU 21c determines whether the kurtosis P1S of the time-varying characteristics exceeds a predetermined threshold value V5 stored in the memory 21m by comprehensively evaluating the time-varying characteristics of the signal strength P1 of a series of responses obtained from the specific RFID tag TG using the first antenna member A1(k) (step S14). The time-varying characteristics of the signal strength P1 can be represented by a line graph connecting detection points and line segments, or by an approximation in which a curve is fitted to the detection points. The kurtosis P1S refers to the increase in the signal strength P1 per unit time measured at the time point when the rate of increase in the time-varying characteristics is at its maximum.

[0027] If the determinations in steps S10 to S14 above are affirmative, the CPU 21c of the RFID reader / writer 21 recognizes that the RFID tag TG has been detected by the first antenna element A1(k) with a predetermined degree of reliability or higher, and determines whether the signal strength P2 of the series of responses obtained from the specific RFID tag TG using the second antenna element A2(k) exceeds a predetermined threshold value V1 stored in the memory 21m (step S15). The CPU 21c then determines whether the number D2 of data points with increasing signal strength P2 in the series of responses from the specific RFID tag TG obtained using the second antenna element A2(k) exceeds a predetermined threshold value V2 stored in the memory 21m (step S16). The CPU 21c then comprehensively evaluates the temporal change characteristics of the signal strength P2 of the series of responses from the specific RFID tag TG obtained using the first antenna element A2(k) and determines whether the peak value P2max in the temporal change characteristics exceeds a predetermined threshold value V3 stored in the memory 21m (step S17). Subsequently, the CPU 21c determines whether the difference between the peak value P2max and the average value P2ave in the time-varying characteristics exceeds a predetermined threshold value V4 stored in the memory 21m by comprehensively evaluating the time-varying characteristics of the signal strength P2 of the series of responses received from the specific RFID tag TG using the first antenna member A2(k) (step S18). Subsequently, the CPU 21c determines whether the kurtosis P2S of the time-varying characteristics exceeds a predetermined threshold value V5 stored in the memory 21m by comprehensively evaluating the time-varying characteristics of the signal strength P2 of the series of responses received from the specific RFID tag TG using the first antenna member A2(k) (step S19).

[0028] If the determinations in steps S15 to S19 are affirmative, the CPU 21c of the RFID reader / writer 21 recognizes that the second antenna assembly A2(k) has detected the RFID tag TG with a predetermined degree of reliability or higher, and performs a comprehensive determination. Specifically, the CPU 21c determines whether the absolute value of the difference between the peak value P1max of the time-varying characteristics of the series of responses from the specific RFID tag TG obtained using the first antenna assembly A1(k) and the peak value P2max of the time-varying characteristics of the series of responses from the specific RFID tag TG obtained using the second antenna assembly A2(k) exceeds a predetermined threshold value V6 stored in the memory 21m (step S20). Furthermore, the CPU 21c determines whether the difference between the appearance time P1T of the peak value P1max in the time-varying characteristics obtained using the first antenna assembly A1(k) and the appearance time P2T of the peak value P2max in the time-varying characteristics obtained using the second antenna assembly A2(k) exceeds a predetermined threshold value V6 stored in the memory 21m (step S21).

[0029] If the difference in peak values ​​|P1max-P2max| is less than the predetermined threshold value V6 as determined in step S20 above, and the difference in peak occurrence times P2T-P1T is less than the threshold value V7 as determined in step S21 above, the CPU 21c of the RFID reader / writer 21 assumes that the same RFID tag TG has been detected with sufficient reliability, and determines that the detected RFID tag TG is a mobile tag and that the RFID tag TG has passed through the read area DA serving as a gate (step S22). If the difference in peak values ​​|P1max-P2max| is greater than or equal to the predetermined threshold value V6 as determined in step S20 above ("No" in step S20), or if the difference in peak occurrence times P2T-P1T is greater than or equal to the threshold value V7 as determined in step S21 above ("No" in step S21), the CPU 21c of the RFID reader / writer 21 determines that the detected RFID tag TG is a stationary tag and that the RFID tag TG has not passed through the read area DA serving as a gate (step S23).

[0030] Performing the determination in the above steps S10 to S14 by comparing the signal intensity P1, the number of data points showing an increase D1, the peak value P1max, the peak-to-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 is equivalent to extracting the temporal change in signal intensity from the detection signal and performing a filtering process on the signal intensity with respect to a through characteristic including the signal intensity and the peak index. Accordingly, performing the determination in the above steps S15 to S19 by comparing the signal intensity P2, the number of data points showing an increase D2, the peak value P2max, the peak-to-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 is equivalent to extracting the temporal change in signal intensity and performing a filtering process on the signal intensity with respect to a through characteristic including the signal intensity and the peak index. In addition, evaluating the difference between the peak occurrence times P2T-P1T and the difference between the peak values ​​|P1max-P2max| is also equivalent to performing filtering. As described above, by performing filtering with respect to the pass characteristics including the signal strength and the peak index, the reliability of the subsequent signal determination processing can be easily improved.

[0031] Figure 6is a diagram illustrating a modified example of a determination operation. In the diagram, the time-varying characteristic of signal strength (which is a series of responses from a specific RFID tag TG obtained using the first antenna element A1(k)) corresponds to actual measurement data comprising 12 measurement points. Simultaneously, the time-varying characteristic of signal strength, which is a series of responses from a specific RFID tag TG obtained using the second antenna element A2(k), corresponds to stored data comprising 14 measurement points. For simplicity, the actual measurement data is decimated for ease of processing, and detection target data with fewer data points is used for passing detection of the specific RFID tag TG. In other words, during the filtering process, the RFID reader / writer 21 reduces the amount of stored signal strength data to a number of data points sufficient to ensure the reliability of the filtering process. Specifically, detection target data for the first antenna element A1(k) and the second antenna element A2(k) is obtained by leaving only three points from the waveform (i.e., the time-varying characteristic): the starting point, the maximum point, and the end point. For ease of explanation, the detection target data is shown as shifted upward relative to the intensity in the diagram. As described above, using detection target data with fewer data points, simplified by decimation, achieves high-speed and efficient signal determination processing.

[0032] Although the above description records that the RFID system 100 includes a main gate 10a and a sub-gate 10b arranged on either side of the channel PW, the RFID system 100 may be a non-gate type, in which a device including circuits and antennas similar to those of the main gate 10a (i.e., an RFID reader / writer 21 and an RFID antenna 23) is located near one side of the channel PW or the reading area DA.

[0033] Although the above description describes that the antenna switch 24 is coupled between the RFID reader / writer 21 and the RFID antenna 23, the antenna switch 24 may be omitted. In this case, the RFID reader / writer 21 detects the RFID tag TG by selectively operating the first antenna member A1(k) and the second antenna member A2(k) constituting the RFID antenna 23.

[0034] The RFID system 100 of the first embodiment described above includes an RFID reader / writer 21, an RFID antenna 23 connected to the RFID reader / writer 21, and a controller 22 that controls the RFID reader / writer 21 to read an RFID tag TG. The RFID antenna 23 includes one or more antenna groups, each comprising a first antenna element A1(k) and a second antenna element A2(k). The first and second antenna elements A1(k) and A2(k) are arranged adjacent to each other in the direction of passage of the RFID tag TG, with a divergence angle difference α such that their visual axis directions diverge forward from each other. The RFID reader / writer 21 processes detection signals retrieved from the RFID tag while selectively operating the first and second antenna elements A1(k) and A2(k), and determines whether the RFID tag has passed by the RFID antenna based on temporal changes in the detection signals.

[0035] The aforementioned RFID system 100 performs reading by selectively operating the first and second antenna members A1(k) and A2(k), which are arranged with a divergence angle difference α so that their visual axis directions D1 and D2 diverge forward from each other. Therefore, even when these antenna members A1(k) and A2(k) are placed close to each other, the aforementioned RFID system can ensure that there is a sufficient time difference in the temporal changes in the signal strength obtained from the two antenna members A1(k) and A2(k). This improves the accuracy of the process of detecting the passage of the RFID tag TG based on the temporal changes in the detection signals obtained by the two antenna members, thereby ensuring the reliability of the passage detection. It should be noted that positioning the two antenna members A1(k) and A2(k) closely together makes the RFID antenna 23 compact, which makes the entire device or gate compact.

[0036] [Second embodiment] Reference below Figure 7 A description is given of an RFID system according to a second embodiment.The RFID system according to the second embodiment is a partial modification of the RFID system according to the first embodiment, and like features are denoted by like reference numerals and will not be described again.

[0037] refer to Figure 7 , a camera 51 is installed in the main gate 10a of the RFID system 100, which captures an image of a reading area DA located above the passage PW.

[0038] The camera 51, driven by the control device 25, captures an image of the read area DA located above the passage PW, extracts an image of a person passing through the passage PW through image processing, and determines whether the 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 read area DA. The RFID system 100 performs this determination based on a combination of the RFID reader / writer 21 detecting the passage of the RFID tag TG and the human detection camera module 50 detecting the passage.

[0039] The RFID system 100 of the second embodiment that performs determination based on a combination of passage detection of the RFID tag TG and passage detection of the human detection camera module 50 can improve detection reliability by secondary use of passage detection of the human detection camera module 50 .

[0040] [Third embodiment] Reference below Figure 8 A description is given of an RFID system according to a third embodiment.The RFID system according to the third embodiment is a partial modification of the RFID system according to the first embodiment, and like features are denoted by like reference numerals and will not be described again.

[0041] refer to Figure 8 In the main gate 10a of the RFID system 100, the control device 25 includes a database 25u. Database 25u processes and manages unique information about RFID tags TG, such as their IDs, retrieved by the RFID reader / writer 21 without accessing higher-level systems. In this case, high-speed authentication can be performed using only a master unit, such as the main gate 10a, eliminating the need for authentication query requests to the higher-level management device 30 or server 70. In other words, high-speed authentication can be performed based on signals retrieved from RFID tags TG by the RFID reader / writer 21, without accessing higher-level systems.

[0042] The standard RFID system 100 requires the advanced management device 30 for authentication because authentication-related data must be verified by the server 70 via the advanced management device 30. When the data retrieved by the RFID reader / writer 21 undergoes the authentication-related verification request process to the server 70 via the advanced management device 30, the large amount of data leads to a problem of increased time required for verification. Furthermore, the software of the advanced management device 30 needs to be adapted to perform this process, which complicates the advanced management device 30. In contrast, an implementation in which the database 25u is integrated into the control device 25 of the main gate 10a and the data stored in the control device 25 is minimized for authentication purposes eliminates the need for verification in a higher-level system when reading tags, significantly reducing the load imposed on the higher-level system and allowing the RFID system 100 to independently perform verification.

[0043] It should be noted that there are two ways to integrate the database 25u into the RFID system 100, as follows: (1) Integrate a simple database. The minimum required data is stored in a simple database. (2) Integrate a complete database. The complete database actually stores data that is equivalent or similar to the data in the original database on the server of the higher-level system.In the implementation where an LCD display is installed at the main gate 10a to display the retrieved data, data equivalent to the data stored in the server of the higher-level system is required.

[0044] For example, when the RFID system 100 is used for library lending management, the system can be configured to issue an alert for RFID tags TG attached to books for which no data is found, by separately storing data indicating that the lending process has been completed in the simplified database 25u. When the RFID system 100 is implemented in a retail store, an alert is triggered for any product with an unregistered RFID tag TG, because only purchased product data is stored in the simplified database 25u.

[0045] The data stored in the simplified database 25u is not limited to whitelist data (data that does not trigger an alarm); the stored data may also include blacklist data (data that triggers an alarm). The simplified database 25u storing whitelist data or blacklist data is obtained by extracting only the objects that are allowed or prohibited from passing from the original database. Integrating the simplified database 25u within the control device 25 can reduce the amount of data stored in the database 25u by storing only the minimum data required for authentication. This improves the processing speed of the control device 25 because it no longer needs to search a large database.

[0046] Although not shown, the above-mentioned database 25 u may be integrated into the RFID reader / writer 21 instead of the control device 25 , or may be integrated as a circuit independent of the control device 25 or the RFID reader / writer 21 .

[0047] like Figure 9 As shown, the first antenna member A1(k) and the second antenna member A2(k) can be installed in a manner that allows the angle between them to 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 with respect to the hinge 10h. The hinge 10h and the angle fixing member 10k serve as an angle adjustment member 10x for adjusting the divergence angle difference α. The pair of frame members 10fa and 10fb are housed in a housing 10f, and the angle between them can be changed. For example, the frame members 10fa and 10fb can be in a state shown by a solid line or a dotted line. This makes it possible to adjust a pair of visual axis directions D1 and D2, thereby allowing adjustment of the divergence angle difference α to be increased or decreased. It should be noted that the divergence angle difference α can be adjusted by adjusting the divergence angle difference α. Figure 3B The time difference between the detection peaks PK1 and PK2 shown in is the separation.

[0048] While the present invention has been specifically described with respect to the above embodiment, the present invention is not limited to the above embodiment. Although the RFID system 100 can manage book checkouts in a library, for example, it is not limited to such applications.

[0049] This application claims priority based on Japanese Patent Application No. 2023-008771, filed on January 24, 2023, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. An RFID system for reading an RFID tag, comprising: RFID reader / writer; An RFID antenna connected to an RFID reader / writer; and A controller that controls the RFID reader / writer, wherein the RFID antenna comprises one or more antenna groups, wherein the antenna group comprises a first antenna component and a second antenna component, wherein the first antenna member and the second antenna member are arranged adjacent to each other in the passing direction of the RFID tag with a divergence angle difference, the divergence angle difference causing a pair of visual axis directions of the first antenna member and the second antenna member to diverge forward from each other, and The RFID reader / writer processes a detection signal retrieved from the RFID tag while selectively operating the first and second antenna members, and determines whether the RFID tag has passed by the RFID antenna based on a temporal change in the detection signal.

2. The RFID system according to claim 1, wherein: The sensitivity separation distance is defined as the distance between the antenna group and the intersection point, which is the intersection 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, and The sensitivity separation distance is 20% to 70% greater than the standard state where the visual axis direction is oriented in the same direction.

3. The RFID system according to claim 1, wherein: The RFID reader / writer extracts a temporal change in signal strength from a detection signal retrieved via the RFID antenna, and determines whether the RFID tag is a tag that has passed by the RFID antenna by performing filtering processing on the signal strength with respect to a passing characteristic including signal strength and a peak index.

4. The RFID system according to claim 3, wherein: During the filtering process, the RFID reader / writer reduces the amount of stored data of signal strength to the number of data points that ensures the reliability of the filtering process.

5. The RFID system according to claim 1, wherein: The one or more antenna groups of the RFID antenna include multiple antenna groups next to the reading area, and Wherein the RFID reader / writer is connected to multiple antenna groups.

6. The RFID system of claim 5, further comprising an antenna switch coupled 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 housed in a single housing.

8. The RFID system according to claim 1, further comprising an infrared human detection module, wherein the infrared human detection module detects a person passing through the reading area. The RFID system makes the determination based on a combination of the passing detection of the RFID tag and the passing detection of the infrared human detection module.

9. The RFID system according to claim 1 , further comprising a human detection camera module configured to detect a person passing through the reading area. The RFID system makes the determination based on a combination of the passage detection of the RFID tag TG and the passage detection of the human detection camera module.

10. The RFID system of claim 1, further comprising a database associated with authentication of the RFID tag.

11. The RFID system according to claim 10, wherein: The database includes a simplified database obtained by extracting only objects whose passage is permitted or prohibited from an original database.

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

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