Parallel coupled line resonator, chip-less tag and method for reading tag information thereof, tag information detection method, and tag information detection circuit

Abstract

To provide a parallel coupled line resonator that uses a coupled line resonator composed of a vertically and horizontally symmetrical structure as a basic resonator of a chip-less tag and being applied to microwave-band chip-less tag that employs a magnetic field coupling for resonant frequency detection to achieve multiple bits and improvement of detection accuracy, a chip-less tag that applies the parallel coupled line resonator, a method for reading tag information thereof, a tag information detection method, and a tag information detection circuit.SOLUTION: A parallel coupled line resonator 300 is defined as a chip-less tag resonator in which two sets of a second parallel two wire coupled line 301B having the same structure as a first parallel two wire coupled line 301A are arranged separately in a vertical direction on a dielectric substrate, being connected to each other by a third parallel two wire coupling line 302 having a different structure, and a central portion of the third parallel two wire coupling line 302 is configured to be coupled by a fourth single line 303 to form a H-shape to have a vertically and horizontally symmetrical structure.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a parallel coupled line resonator applied to a chipless tag that assigns code information by changing the resonant frequency of a resonator using a transmission line, and a chipless tag to which this parallel coupled line resonator is applied, as well as a tag information reading method, tag information detection method, and tag information detection circuit. [Background technology]

[0002] Barcodes are often used for inventory management, logistics management, and entrance / exit management. Their greatest advantage is that the codes can be created by printing, making them extremely inexpensive, and reading devices can be implemented using digital cameras, making them inexpensive as tag systems. As a result, barcodes have become widespread as a basic technology related to the Internet of Things (IoT).

[0003] However, barcode information has no confidentiality (it is completely visible), it can be misrecognized due to dirt, it can be easily duplicated (copied), there is a risk of it being tampered with, and other drawbacks make it unreliable. It also has a narrow reading area and cannot be read if there is an obstacle.

[0004] Furthermore, RFID (Radio Frequency Identification) using semiconductor chips, which has recently become increasingly popular, overcomes these drawbacks and has the excellent feature of being able to read as well as write, but because it uses semiconductor chips, the cost of the tag is high due to the chip and board mounting, it cannot be used in high temperature or strong radiation environments where semiconductors malfunction, and there are also issues such as the size of the reader being large due to the antenna, high power consumption, difficulty in portability, and high device cost.Therefore, there is no universal tag that can be used under all usage conditions and environments, and it is necessary to select a tag that suits the purpose of use and the environment.

[0005] In order to solve these problems with RFID, chipless RFID that complements the functions of barcodes has been developed and put to practical use, as described in the following document.

[0006] Non-Patent Document 1 is an explanatory paper on chipless RFID tags, and discloses general technology in this field. Figure 11 in Non-Patent Document 1 shows a configuration example using multiple resonator elements, and shows a notch filter configuration for detecting the resonant frequency of a resonator in a multi-resonator configuration in which one resonator basically corresponds to one bit.

[0007] Non-Patent Document 2 discloses an encoding method for chipless tags using a multi-mode resonant frequency with one stepped impedance resonator (SIR).

[0008] Non-Patent Document 3 discloses a technique that uses a near electromagnetic field instead of an antenna to read resonance frequency information of a tag resonator made of a multi-mode SIR.

[0009] Moreover, Patent Document 1 discloses an encoding method for chipless tags using SIR.

[0010] Patent Document 2 discloses a method of detecting a probe using a near electromagnetic field, targeting tags having an SIR configuration.

[0011] Patent Document 3 discloses a notch filter type multi-resonator tag that applies SIR to the tag, which has a simpler configuration and can handle an expanded amount of information, can be used over a wide frequency band, and can easily write information to the tag at low cost. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Patent No. 6453058 [Patent Document 2] Patent No. 6636336 [Patent Document 3] Patent No. 6762006

[0013] [Non-Patent Document 1] P. Preradovic and NCKarmakar, "Chipless RFID: Bar Code of the Future," IEEE Microwave Magazine, vol.11, No.7, pp.87-97, Dec.2010 [Non-Patent Document 2] Makimoto, Sakai, and Wada, "Study on Chipless RFID Using Multi-mode Stepped Impedance Resonators", Institute of Electronics, Information and Communication Engineers, IEICE Technical Report SRW2014-37(2014-37), pp.11-16, December 2014. [Non-Patent Document 3] F.Sakai, M.Makimoto and K.Wada, “Near-field chipless RFID tag system using inductive coupling between a multimode resonator and detection probes,” Trans. IEICE Com., Vol.E102-B, No.4, pp.722-731, Apr. 2019 Summary of the Invention [Problem to be solved by the invention]

[0014] As disclosed in Non-Patent Document 1, in chipless tags that have a notch filter configuration using multiple resonators, with each resonator corresponding to one bit, the resonators must be precisely manufactured in order to accurately detect tag information, and there are problems such as the tag becoming larger as the number of bits increases.

[0015] Furthermore, the technology disclosed in Non-Patent Document 2 is an encoding method for chipless tags using multi-mode resonant frequencies, and is not an encoding method that applies multiple resonators using a single mode.

[0016] Furthermore, the technology disclosed in Non-Patent Document 3 utilizes a near electromagnetic field to read resonance frequency information of a tag resonator using an SIR.

[0017] The SIR-based encoding method for chipless tags disclosed in Patent Document 1 is technically identical to that disclosed in Non-Patent Document 2.

[0018] Furthermore, Patent Document 2 discloses the method of probe detection using the near electromagnetic field of Non-Patent Document 3, which targets tags with an SIR configuration.

[0019] An example of a notch filter type chipless tag using the SIR multi-resonator in the above-mentioned Patent Document 3 is shown in Figures 14(A) and 14(B). Figure 14(A) is a schematic plan view of a chipless tag 1000 showing a basic circuit before information is written, and Figure 14(B) is a schematic plan view of a chipless tag 1000 showing a circuit after information has been written.

[0020] The basic circuit shown in FIG. 14A is a circuit in which n open-ended stepped impedance resonators (SIRs) 1201a to 1201n with different resonant frequencies are arranged in a U-shape on a main transmission line 1101 for reading information having input / output terminals 1103 and 1104, and a part of the line is electromagnetically coupled (parallel) to the main transmission line. The operation of this circuit is as follows: 1 ~f n Each resonator is a notch filter (narrow-band band-stop filter) with n attenuation poles. If the frequency characteristics of the basic circuit described above are measured, and the observation of a resonance point that is the peak of the attenuation characteristics of each resonator corresponds to '1', and the absence of a resonance point corresponds to '0', then (A) in Figure 14 represents an n-bit tag with all '1's.

[0021] Next, when writing information, a part of the line constituting the resonator is cut off, and the resonant frequency is detuned much higher than the original frequency. In the example of FIG. 14(B), resonator 1201b and resonator 1201 n-1Cut off part 1206b, 1206 n-1 By setting the resonant frequency to f 2 From f 2 ' and f n-1 From f n-1 This shows the state in which the resonator is detuned to f and the information is rewritten from '1' to '0'. Because the resonator and the line are electromagnetically coupled, the circuit responds to both the '1' and '0' states, making detection possible. For this reason, the resonant frequency for the '0' state must be set outside the band allocated to the tag system. Now, f 1 <f 2 <... <f n-1 <f n Then, in this example, f n <f 2 ' <f n-1 ' must be.

[0022] As mentioned above, chipless RFID complements the functions of barcodes, and while barcodes are read optically, this is a method that uses electromagnetic waves, and basically uses multiple transmission line resonators with different resonance frequencies to assign information to the resonance frequency, and by coating the tag's circuit pattern, it is possible to make it invisible from the outside, making the information highly confidential, difficult to copy, and much more resistant to tampering than barcodes.The above are characteristics common to all conventionally known chipless tags, but conventional chipless tags have the disadvantage that they cannot capture much information (number of codes) and have poor reading accuracy.

[0023] In other words, the basic issues with chipless tags that use electromagnetic waves are that the resonator, which is the basic element that provides information, is large in size, making it difficult to increase the number of bits, and it is difficult to couple the reading circuit and the resonator, making detection difficult and reducing reading accuracy. When using multiple resonators, a notch filter type configuration is suitable for miniaturizing the entire tag. However, electromagnetic field coupling (distributed coupling) is often used to couple the resonator and the detection circuit, and the coupling length needs to be long to strengthen the coupling, which results in an issue of tag size being large.

[0024] In addition, the use of a stepped impedance resonator (SIR) is effective in terms of miniaturization, but has the disadvantage that it is difficult to couple with the read circuit.

[0025] In view of the above-mentioned conventional situation, the present invention aims to provide a parallel coupled line resonator applicable to microwave chipless tags, which uses a coupled line resonator having a top-bottom and left-right symmetrical structure as the basic resonator of the chipless tag and employs magnetic field coupling to detect the resonant frequency, thereby achieving multi-bit operation and improved detection accuracy, as well as a chipless tag employing this parallel coupled line resonator, a tag information reading method, a tag information detection method, and a tag information detection circuit.

[0026] Another object of the present invention is to provide a parallel coupled line resonator having a structure in which a strong magnetic field is generated by lines located on upper and lower symmetrical planes, enabling detection of a resonant frequency with a short coupling length.

[0027] Another object of the present invention is to provide a chipless tag that can be miniaturized or has a large number of bits, and to provide a chipless tag in which the response waveform can be easily identified by devising the arrangement of the tag resonator.

[0028] Another object of the present invention is to enable detection of tag information by accurately determining the resonance frequency.

[0029] Another object of the present invention is to provide a tag information detection circuit capable of significantly reducing malfunctions by applying a fundamental resonance mode to tag information detection.

[0030] Furthermore, while conventionally, the resonant frequency has been detected by detecting the amplitude response level, the present invention introduces a new detection method that focuses on the phase change of the resonator, thereby providing a tag information detection circuit that can accurately determine the resonant frequency and detect tag information.

[0031] In other words, by applying these new methods, the present invention provides new technology that enables chipless tags to have multiple bits and improve detection accuracy.

[0032] Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the following description of the embodiments. [Means for solving the problem]

[0033] In the present invention, two identical U-shaped SIRs are used to configure an H-shaped resonator so that it is vertically and horizontally symmetrical, and a parallel coupled line resonator is constructed in which a strong magnetic field is generated by the lines that form the vertical symmetrical plane in the center of the resonator. This makes it possible to detect the resonance frequency with a short coupling length, and detection is possible without shortening the coupling interval between the resonator and the reading line. In addition, the interval between the tag resonators can be set narrower, making it possible to miniaturize the tag or increase the number of bits.

[0034] That is, the present invention is a parallel coupled line resonator, characterized in that two sets of second parallel two-wire coupled lines having the same structure as the first parallel two-wire coupled line are arranged separately in the vertical direction on a dielectric substrate, and are connected to each other by a third parallel two-wire coupled line having a different structure, and the central parts of the third parallel two-wire coupled lines are coupled by a fourth single line, forming an H-shape and having a vertically and horizontally symmetrical structure.

[0035] The present invention also provides a chipless tag configured by implementing a plurality of the above-mentioned parallel coupled line resonators, characterized in that a plurality of the above-mentioned parallel coupled line resonators having different resonant frequencies are prepared by changing the structural parameters of each line, and information is assigned to each parallel coupled line resonator or each corresponding resonant frequency.

[0036] The chipless tag of the present invention can be configured such that the central portion of the fourth single line of the parallel coupled line resonator is cut to shift the resonant frequency to a higher frequency, thereby controlling the resonant frequency, and assigning a code of '1' to the initial state and a code of '0' to the state after the cut.

[0037] In addition, in the present invention, the fundamental resonance mode is applied to detect tag information. In a chipless tag configured by implementing multiple parallel coupled line resonators as described above, the higher resonance mode adjacent to the fundamental resonance mode does not allow current to flow in the central line and does not generate a magnetic field, so that the resonance characteristics are not detected, resulting in a detection circuit in which malfunctions can be significantly reduced.

[0038] That is, the present invention is a tag information reading method, characterized in that the tag information is read by detecting a magnetic field generated in the fourth single line of the parallel coupled line resonator provided in the chipless tag.

[0039] The present invention also provides a tag information detection method for detecting the resonance frequency of the chipless tag, characterized in that a linear microstrip line is provided on a dielectric substrate, the direction of the line is aligned with the direction of a fourth single line of a parallel coupled line resonator provided in the chipless tag, and the microstrip line and the fourth single line of the parallel coupled line resonator are arranged so as to generate magnetic field coupling with each other to detect the resonance frequency of the tag.

[0040] Furthermore, the present invention introduces a new detection method that focuses on the phase change of the resonator, making it possible to accurately determine the resonance frequency and detect tag information.

[0041] That is, the present invention is a tag information detection circuit for detecting tag information of the chipless tag, characterized in comprising two straight microstrip lines having the same shape and characteristics, and a phase difference detection means for using one of the two straight microstrip lines as a transmission line for detecting the tag information and the other as a reference transmission line, and detecting the phase difference between the detection transmission line and the reference transmission line when detecting tag information, thereby extracting the phase characteristics of only the parallel coupled line resonator provided in the chipless tag.

[0042] Furthermore, in the present invention, in a chipless tag to which multi-bit tag information is assigned, the tag resonators are arranged in a way that makes the response waveform easily identifiable, and the resonant frequencies of adjacent tag resonators are as far apart as possible.

[0043] That is, the present invention provides a chipless tag to which multi-bit tag information is assigned, The present invention is characterized in that a plurality of parallel coupled line resonators are arranged in ascending order of resonant frequency and divided into two groups, a low-frequency group and a high-frequency group, and one resonant frequency is selected from each group in ascending order of resonant frequency and arranged alternately, thereby arranging the resonant frequencies of adjacent parallel coupled line resonators so as to be separated from each other, thereby reducing coupling between the parallel coupled line resonators. Effect of the Invention

[0044] In the present invention, two U-shaped SIRs of the same structure are used to configure an H-shaped resonator so that it is symmetrical vertically and horizontally, and a parallel coupled line resonator is configured to generate a strong magnetic field in the lines that form the vertical symmetrical plane at the center of the resonator.This makes it possible to detect the resonance frequency with a short coupling length, shorten the coupling length between the resonator and the read line, and set the resonator spacing narrower, making it possible to miniaturize the tag or increase the number of bits.

[0045] In addition, in the present invention, in a chipless tag configured by mounting a plurality of the above-mentioned parallel coupled line resonators, the adjacent higher-order resonance modes do not detect resonance characteristics because no current flows in the central line and no magnetic field is generated. Therefore, the fundamental resonance mode is applied to tag information detection, making it possible to provide a detection circuit that can significantly reduce malfunctions.

[0046] Furthermore, in the present invention, by focusing on the phase change of the resonator and detecting the phase difference between the detection transmission line and the reference transmission line when detecting tag information, the phase characteristics of only the parallel coupled line resonator provided in the chipless tag can be extracted, making it possible to accurately determine the resonant frequency and detect tag information.

[0047] Therefore, according to the present invention, it is possible to provide a parallel coupled line resonator applicable to microwave chipless tags which uses a coupled line resonator having a top-bottom and left-right symmetrical structure as the basic resonator of a chipless tag and employs magnetic field coupling to detect the resonant frequency, thereby achieving multi-bit operation and improved detection accuracy, as well as a chipless tag which applies this parallel coupled line resonator, as well as a tag information reading method, tag information detection method, and tag information detection circuit. [Brief description of the drawings]

[0048] [Figure 1] FIG. 1 is a schematic plan view showing the basic configuration of a parallel coupled line resonator according to the present invention. [Diagram 2] 2(A) and (B) are diagrams showing the resonance modes of the above-mentioned parallel coupled line resonator, where (A) is a schematic plan view of a parallel coupled line resonator showing a fundamental resonance mode, and (B) is a schematic plan view of a parallel coupled line resonator showing a higher-order (second-order) resonance mode. [Diagram 3] FIG. 3 is a schematic plan view of a parallel coupled line resonator according to the present invention, showing an example of a design for the microwave band. [Figure 4] FIG. 4 is a characteristic diagram showing the relationship between the line spacing and the resonant frequency in the parallel coupled line resonator. [Diagram 5] 5(A) and (B) are diagrams showing an example of writing data to a parallel coupled line resonator according to the present invention, where (A) is a schematic plan view showing the parallel coupled line resonator before data is written, and (B) is a schematic plan view showing the parallel coupled line resonator after data has been written. [Figure 6] FIG. 6 is a schematic plan view showing a 4-bit chipless tag constructed using a parallel coupled line resonator according to the present invention. [Figure 7] 7(A) and (B) are diagrams showing a tag information reading circuit used in the present invention, where (A) is a plan view of the reading circuit and (B) is a side view of the reading circuit. [Figure 8] FIG. 8 is a perspective view showing the positional relationship between the chipless tag and a reading circuit when reading tag information. [Figure 9] 9(A), (B), (C), and (D) are diagrams showing examples of detected waveforms at the resonance point of the parallel coupled line resonator according to the present invention, where (A) shows the detected waveform of the amplitude characteristic, (B) shows the measurement result of the phase change, (C) shows the result of phase difference detection, and (D) shows the result of frequency differentiation of the phase difference characteristic. [Figure 10] FIG. 10 is a circuit diagram showing an example of a tag information detection circuit for extracting the phase characteristic of a parallel coupled line resonator alone according to the present invention. [Figure 11] FIG. 11 is a diagram showing a simulation example of detection of a 1-bit tag designed with a resonant frequency of 8 GHz. [Figure 12] Figures 12(A) and (B) show a simulation example of the detection of a 4-bit tag designed with a resonant frequency of 8 GHz, where (A) shows the detection waveform for tag information

[1111] , and (B) shows the detection waveform for tag information

[1001] . [Figure 13] FIG. 13 is a schematic plan view of a chipless tag for explaining the arrangement of a tag resonator when the tag has multiple bits. [Figure 14] Figures 14(A) and (B) are diagrams showing examples of notch filter type chipless tags using a conventional SIR multi-resonator, where (A) is a schematic plan view of the chipless tag before information is written to it, and (B) is a schematic plan view of the chipless tag after information has been written to it. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] A preferred embodiment of the present invention will be described in detail below. Note that the embodiment described below does not unduly limit the content of the present invention described in the claims, and all of the configurations described in the embodiment are not necessarily essential as the solution of the present invention.

[0050] FIG. 1 is a schematic plan view showing the basic configuration of a parallel coupled-line resonator 300 according to the present invention.

[0051] The parallel coupled line resonator 300 has a configuration in which a first parallel two-wire coupled line 301A having a line width W1 and a line spacing S1 and a second parallel two-wire coupled line 301B of the same structure are arranged in the same direction and connected to each other by a third parallel two-wire coupled line 302 having a line width W2 and a line spacing S2, and a fourth single line 303 is provided in the center of the third parallel two-wire coupled line 302 to connect the parallel lines.

[0052] With this configuration, the parallel coupled line resonator 300 has a plane of symmetry in the vertical direction at the center of the fourth single line 303, and a left-right symmetrical structure at the center of the parallel lines, as shown in Fig. 1. The plane of symmetry is the center line of the parallel lines, and therefore serves as a virtual ground point.

[0053] That is, in this parallel coupled line resonator 300, two sets of second parallel two-wire coupled lines 301B having the same structure as the first parallel two-wire coupled line 301A are arranged separately in the vertical direction on a dielectric substrate, and are connected to each other by a third parallel two-wire coupled line 302 having a different structure. The central parts of the third parallel two-wire coupled lines 302 are coupled by a fourth single line 303, forming an H-shape with vertical and left-right symmetry.

[0054] In the conventional example shown in FIG. 14, the substrate has a ground conductor, but in this parallel coupled line resonator 300, a ground conductor is not necessary.

[0055] Next, (A) and (B) of Figure 2 are diagrams showing the resonance modes of the parallel coupled line resonator 300. (A) is a schematic plan view of the parallel coupled line resonator 300 showing the fundamental resonance mode, and (B) is a schematic plan view of the parallel coupled line resonator 300 showing a higher-order (second-order) resonance mode.

[0056] The electric field at the two open ends of the parallel coupled line resonator 300 is distributed positively and negatively (+,-) at the time of resonance, as shown in Fig. 2(A) and (B). However, in the case of fundamental resonance, as shown in Fig. 2(A), the electric potential at the two open ends is distributed positively (+) and negatively (-) with respect to the virtual ground plane, and the electric field directions are the same, but in the case of the second-order mode, as shown in Fig. 2(B), the electric field directions are opposite to each other. Therefore, in the fourth single line 303 at the center of the resonator, currents flow in an added manner in the fundamental resonance mode, as shown by the arrow in Fig. 2(A), but in the case of the second-order higher-order mode, currents flow in opposite directions, as shown by the arrow in Fig. 2(B), and they cancel each other out, becoming zero, so no current flows.

[0057] Therefore, to detect resonance, as described below, a method is used to detect the magnetic field generated in the fourth single line 303. However, for higher modes, no current flows in the fourth single line 303 and no magnetic field is generated, so even if resonance occurs, it will not be detected.

[0058] The vertical symmetric plane indicates symmetry in terms of structure, but in the fundamental mode, it is also a symmetric plane in terms of electrical circuitry. Therefore, the circuit can be divided into two U-shaped resonators at this symmetric plane, and the basic characteristics such as resonance conditions can be examined by considering the U-shaped resonator, and can be performed by the SIR analysis method shown in Patent Document 3. In addition, the parallel coupled line resonator 300 according to the present invention, which is configured by connecting two resonators, is characterized in that, during resonance, the currents of the respective U-shaped resonators are added to the fourth single line 303 at the connection part, so that twice the current flows, the generated magnetic field becomes larger, and the detection level becomes higher.

[0059] The parallel coupled line resonator 300 according to the present invention is used as a plurality of tag resonators 401 constituting a chipless tag 400 as described below.

[0060] FIG. 3 is a schematic plan view of a parallel coupled line resonator 300 according to the present invention, showing a design example in the microwave band used as a resonator for a tag.

[0061] The parallel coupled line resonator 300 of the design example shown in FIG. 3 is mounted on a dielectric substrate having a relative dielectric constant of 3.2 and a thickness of 0.25 mm, and the structural parameters shown in FIG. 1 are set as follows: L1 = 2.3 mm, L2 = 4.0 mm, L3 = 2.0 mm, and W2 = W3 = 1.0 mm. The resonance conditions were examined by simulation by changing W1 and S1 under the condition of Wt = 2W1 + S1 = 4.0 mm.

[0062] FIG. 4 is a characteristic diagram showing the relationship between line spacing S1 and resonant frequency in parallel coupled line resonator 300 of the above design example from which the results were obtained.

[0063] As can be seen from this result, in the parallel coupled line resonator 300 of the above design example, the resonant frequency can be changed from 7.2 GHz to 10.2 GHz in a 3 GHz band by changing the line spacing S1 from 0.2 mm to 2.0 mm. Since there are five other design parameters, it can be understood that a resonator with high design freedom can be realized. In addition, this simulation confirmed that when the dielectric loss tangent tanδ of the dielectric substrate is 0.005, the unloaded Q of the resonator is 300 or more in the entire band.

[0064] Next, (A) and (B) of Figure 5 are diagrams showing an example of writing data to the parallel coupled line resonator 300 according to the present invention, where (A) is a schematic plan view showing the parallel coupled line resonator 300A before writing data, and (B) is a schematic plan view showing the parallel coupled line resonator 300B after writing data.

[0065] The state of the parallel coupled line resonator 300A before writing the data shown in Fig. 5(A) corresponds to data '1'. At this time, the fourth single line 303 in the center of the resonator is as shown in Fig. 2, and the resonant frequency is the fundamental mode.

[0066] Moreover, parallel coupled line resonator 300B in which the data shown in FIG. 5B has been written is in a state in which fourth single line 303 is cut at cut portion 304, and this corresponds to data '0'.

[0067] By cutting the fourth single line 303, the resonant frequency of the parallel coupled line resonator 300 shifts to the higher side. As will be explained later, the resonant frequency is detected by detecting the magnetic field generated in the fourth single line 303, but since the magnetic field is no longer generated by this cutting, it becomes difficult to detect the resonant frequency after cutting. Therefore, it can be seen that this is a detection method with good accuracy and good discrimination between data '1' and '0'.

[0068] Therefore, the parallel coupled line resonator 300 can be configured to cut the central portion of the fourth single line 303 to shift the resonant frequency to a higher frequency, thereby controlling the resonant frequency, and assigning a code of '1' to the initial state and a code of '0' to the state after cutting. A plurality of such resonators can be implemented as tag resonators to form a chipless tag.

[0069] The chipless tag of the present invention uses a plurality of parallel coupled line resonators 300 with different resonant frequencies as tag resonators, and assigns one bit to each of them to form the tag.

[0070] Here, FIG. 6 is a schematic plan view showing a 4-bit chipless tag 400 configured using the parallel coupled line resonator 300 according to the present invention.

[0071] This chipless tag 400 is realized by arranging tag resonators #1 (401A), #2 (401B), #3 (401C), and #4 (401D) at regular intervals so that the upper and lower symmetrical planes of each resonator coincide with the center line CC' 402 of a tag substrate 405 made of a dielectric substrate. In the chipless tag 400 shown in FIG. 6, the tag resonator #1 (401A) and the tag resonator #4 (401D) are data '1', and the tag resonator #2 (401B) and the tag resonator #3 (401C) are data '0'. The tag resonators must be spaced apart so that they are not coupled to each other.

[0072] 7(A) and (B) are diagrams showing a tag information reading circuit 100 used in the present invention, where (A) is a plan view of the reading circuit 100 and (B) is a side view of the reading circuit 100. This reading circuit 100 has an extremely simple configuration and is a linear microstrip transmission line 101 provided on a dielectric substrate 105 having a ground conductor 106. An input terminal 103 and an output terminal 104 are connected to both ends of this microstrip transmission line 101. The line impedance is usually set to 50 Ω to match the impedance of the input / output devices.

[0073] The reading circuit 100 spatially couples a tag resonator to the microstrip transmission line 101 and detects the notch resonance frequency.

[0074] FIG. 8 is a perspective view showing the positional relationship between the chipless tag 400 and the reading circuit 100 when reading tag information.

[0075] That is, when reading tag information from the 4-bit chipless tag 400 shown in Figure 6 above, as shown in Figure 8, the tag substrate 405 of the chipless tag 400 and the dielectric substrate 105 of the reading circuit 100 are arranged parallel to one another, and the substrate center line (CC') 402 of the tag substrate 405 and the straight microstrip line 101 of the reading circuit 100 are aligned in the same direction, and the substrate center line (CC') 402 of the tag substrate 405 is positioned directly above the microstrip line 101 and are arranged spatially close to each other. In this state, the direction of the magnetic field generated in the fourth single line 303 in the center of the tag resonators #1 (401A), #2 (401B), #3 (401C), and #4 (401D) is the same as the direction of the magnetic field in the microstrip line 101, so that a strong magnetic coupling occurs between the two, and an attenuation point (notch characteristic) appears in the transmission characteristics of the reading circuit 100, making it possible to detect the resonant frequency of the tag.

[0076] Next, (A), (B), (C), and (D) of FIG. 9 are diagrams showing examples of detected waveforms of the resonance point of the parallel coupled line resonator 400 according to the present invention, where (A) shows the detected waveform of the amplitude characteristic, (B) shows the measurement result of the phase change, (C) shows the result of the phase difference detection, and (D) shows the result of frequency differentiation of the phase difference characteristic.

[0077] The output characteristics of the reading circuit 100 have attenuation points at each resonance point of the tag resonators #1 (401A), #2 (401B), #3 (401C), and #4 (401D), and the changes can be measured in amplitude and phase.

[0078] Here, Fig. 9 (A), (B), (C), and (D) show an example of a simulation of a 1-bit tag at 8 GHz microwave frequency.

[0079] FIG. 9(A) shows the detected waveform of the amplitude characteristic, with a peak level of -2.3 dB and a half-width (frequency width at 1 / 2 the peak level) of 28 MHz.

[0080] FIG. 9B shows the measured phase change. In this case, the large linear phase change of the transmission line is superimposed, masking the small change of the resonator and making it impossible to measure accurately.

[0081] For this reason, it is necessary to remove the phase change of the transmission line and extract only the phase change of the resonator (difference detection). By doing so, the characteristic shown in Figure 9(C) is obtained, making it possible to clearly capture the phase change at the resonance point.

[0082] Furthermore, when this phase difference characteristic is frequency differentiated, a sharp single peak characteristic is obtained as shown in Figure 9(D). The half-width of the characteristic shown in Figure 9(D) is 12 MHz, and a characteristic that is easier to distinguish is obtained than the level detection waveform in Figure 9(A).

[0083] From the above, it is understood that phase detection is more suitable for the present invention.

[0084] Next, FIG. 10 is a circuit configuration diagram showing an example of a tag information detection circuit for extracting the phase characteristic of a single parallel coupled line resonator according to the present invention.

[0085] Here, the phase characteristics of the resonator alone can be obtained by acquiring and storing the transmission characteristics of only the transmission line of the reading circuit without bringing the tag close to the reading circuit, and then calculating the difference after measuring the tag. However, this has the disadvantages of taking a long time to measure, requiring memory and calculation processing, and not being able to process in real time.

[0086] Therefore, in the present invention, as shown in the tag information detection circuit 200 in FIG. 10, two straight microstrip lines having the same shape and characteristics are provided on a reading circuit board, one of the two straight microstrip lines is used as the tag information detection transmission line 101A and the other is used as the reference transmission line 101B, and the difference in their transmission characteristics is constantly measured. When tag information is detected, a phase difference detection means detects the phase difference between the detection transmission line 101A and the reference transmission line 101B, thereby extracting the phase characteristics of only the parallel coupled line resonator provided in the chipless tag.

[0087] In the tag information detection circuit 200 shown in FIG. 10, a signal inputted from an input terminal 103 is divided into two by an in-phase (0°) power splitter 501 and inputted to two transmission lines (linear microstrip lines) 101A and 101B. A tag is coupled to a detection transmission line 101A to acquire tag information, and after being divided into two by an in-phase (0°) power splitter 502, one of the signals is inputted to an amplitude detector 503. This amplitude detector 503 detects the amplitude of the one of the signals to detect the peak of the tag resonator and outputs it to an amplitude output terminal 104A. In addition, the other signal of the power splitter 502 becomes one input of a phase detector 504. The other input of this phase detector 504 is a signal propagated through the reference transmission line 101B, and the phase difference between the two signals is detected by phase detection. The phase difference output signal from this phase detector 504 is input to a differentiation circuit 505, which outputs a peak signal of the above phase difference output signal to a phase output terminal 104B. With this method, the resonance point of the tag resonator based on the amplitude and phase information during measurement can be detected simultaneously and continuously in real time, and the two detection data can be compared and complemented, which is expected to improve the detection accuracy.

[0088] That is, in this tag information detection circuit 200, two straight microstrip lines having the same shape and characteristics are prepared, one straight microstrip line is used as the tag information detection transmission line 101A, and the other straight microstrip line is used as the reference transmission line 101B.When detecting tag information, the phase difference between the detection transmission line 101A and the reference transmission line 101B is detected to extract the phase characteristics of only the parallel coupled line resonator provided in the chipless tag, i.e., the tag resonator.

[0089] Next, FIG. 11 is a diagram showing a simulation example of detection of a 1-bit tag designed with a resonant frequency of 8 GHz.

[0090] In this simulation example, information is read using the arrangement shown in Figure 8, and examples of the detected waveforms of the phase difference differential output when the substrate distance Lg between the chipless tag 400 and the reading circuit 100 is set to 1.5 mm, 1.0 mm, and 0.7 mm are shown in Figure 11.

[0091] If the board spacing Lg is narrow, the response is large, but the resonance frequency shifts to a lower range. If Lg is widened, the response is small, but it can be seen that even a spacing of 1.5 mm is sufficient for detection. In this simulation, the range that can be detected with good accuracy is about 1.1 ± 0.4 mm, and in this case the frequency fluctuation range is 20 MHz or less, which is no problem in practice.

[0092] Furthermore, Figures 12(A) and (B) show a simulation example of the detection of a 4-bit tag designed with a resonant frequency of 8 GHz, where (A) shows the detection waveform for tag information

[1111] , and (B) shows the detection waveform for tag information

[1001] .

[0093] Figure 12 shows an example of the detection waveform when the tag in Figure 11 is made 4 bits. In the figure, (A) shows the case where the information is ('1', '1', '1', '1'), and (B) shows the case where the information is ('1', '0', '0', '1').

[0094] Here again, the board spacing Lg was set to 1.5 mm, 1.0 mm, and 0.7 mm, and it can be seen that there were no problems with detection in any case. Also, in this example, a design in which the resonance frequency spacing between adjacent tag resonators is 100 MHz, it can be confirmed that the resonance peaks do not overlap and each peak frequency can be accurately identified. Therefore, with a usable microwave band of 3 GHz, it is expected that tags with approximately 30 bits can be realized.

[0095] Next, FIG. 13 is a schematic plan view of a chipless tag 450 for explaining the arrangement of a tag resonator when the tag has multiple bits.

[0096] As the number of bits increases, the spacing between tag resonators becomes narrower. However, if the resonant frequencies of adjacent tag resonators are close to each other, electrical coupling can occur between the resonators, causing the resonant waveforms to overlap and distort the waveform, making identification difficult. To avoid this, adjacent resonators should be arranged so that their frequencies are as far apart as possible. Let us consider an example of such an arrangement. Let a 2N-bit tag be represented as #2N, and their resonant frequencies be ordered in ascending order of f 1 ,f 2 ,f 2N Assume that the tags are set as follows. If the tags are divided into two groups, 1 to N and N+1 to 2N, and one tag is selected from each group and arranged in the order of #1, #N+1, #2, #N+2, . . . , #N, #2N, starting from the lowest number, the resonant frequencies of adjacent resonators can be spaced far enough apart. If the tags are an odd number of bits, 2N-1, then the tags can be divided into two groups, 1 to N and N+1 to 2N-1, and similar processing can be performed. Figure 13 shows an example of a 10-bit tag, with 10 frequencies f N The tag resonators #N are arranged on the substrate center line (CC') 402 in the order of #1, #6, #2, #7, . . ., #5, #10, based on the above-mentioned method.

[0097] As can be seen from this, the resonance frequencies of adjacent tag resonators are sufficiently far apart, so there is no coupling between the resonators, making it possible to detect a stable resonance frequency.

[0098] That is, in the chipless tag 450 to which multi-bit tag information is assigned, the tag resonators are arranged in a way that makes the response waveform easily identifiable, and multiple parallel coupled line resonators are arranged in ascending order of resonant frequency and divided into two groups, a low-frequency group and a high-frequency group, and one resonant frequency is selected from each group in ascending order of resonant frequency and arranged alternately, thereby arranging the resonant frequencies of adjacent parallel coupled line resonators so as to be separated from each other, thereby achieving a configuration in which coupling between the parallel coupled line resonators is reduced. [Explanation of symbols]

[0099] 100 reading circuit, 101 microstrip transmission line, 101A detection transmission line, 101B reference transmission line, 103 input terminal, 104 output terminal, 104A amplitude output terminal, 104B phase output terminal, 105 dielectric substrate, 106 ground conductor, 200 tag information detection circuit, 300, 300A, 300B parallel coupled line resonator, 301A first parallel two-wire coupled line, 301B second parallel two-wire coupled line, 302 third parallel two-wire coupled line, 303 fourth single line, 304 cut portion, 401, 401A to 401D tag resonator, 402 substrate center line, 400, 450 chipless tag, 405 tag substrate, 501 power splitter, 503 amplitude detector, 504 Phase detector, 505 Differentiator,

Claims

1. A parallel coupled line resonator comprising: two sets of second parallel two-wire coupled lines having the same structure as the first parallel two-wire coupled line, separated in the vertical direction on a dielectric substrate; the second sets of second parallel two-wire coupled lines having the same structure as the first parallel two-wire coupled line, connected to each other by a third parallel two-wire coupled line having a different structure; and a fourth single line coupled to the central portions of the third parallel two-wire coupled lines, configured in an H-shape and having a vertically and horizontally symmetrical structure.

2. A chipless tag comprising a plurality of parallel coupled line resonators according to claim 1, A chipless tag characterized in that a plurality of parallel coupled line resonators having different resonant frequencies are prepared by changing the structural parameters of each line, and information is assigned to each parallel coupled line resonator or each corresponding resonant frequency.

3. The chipless tag of claim 2, characterized in that the resonant frequency is controlled by cutting the central portion of the fourth single line of the parallel coupled line resonator to shift the resonant frequency to a higher frequency range, and a code of '1' is assigned to the initial state and a code of '0' is assigned to the state after cutting.

4. A tag information reading method, comprising: reading tag information by detecting a magnetic field generated in a fourth single line of a parallel coupled line resonator provided in the chipless tag according to claim 2 or 3.

5. A tag information detection method for detecting an oscillation frequency of a chipless tag according to claim 2 or 3, comprising: A tag information detection method characterized by providing a linear microstrip line on a dielectric substrate, aligning the direction of the line with the direction of a fourth single line of a parallel coupled line resonator provided in the chipless tag, and arranging the microstrip line and the fourth single line of the parallel coupled line resonator so that magnetic field coupling occurs between them, thereby detecting the resonant frequency of the tag.

6. A tag information detection circuit for detecting tag information of a chipless tag according to claim 2 or 3, comprising: Two linear microstrip lines having the same shape and characteristics; a phase difference detection means for detecting a phase difference between the detection transmission line and the reference transmission line when detecting tag information, by using one of the two linear microstrip lines as a transmission line for detecting tag information and the other as a reference transmission line, thereby extracting a phase characteristic of only the parallel coupled line resonator provided in the chipless tag; A tag information detection circuit comprising:

7. 4. The chipless tag according to claim 2 or 3, in which multi-bit tag information is provided, A chipless tag having a configuration in which a plurality of parallel coupled line resonators are arranged in ascending order of resonant frequency and divided into two groups, a low-frequency group and a high-frequency group, and one resonant frequency is selected from each group in ascending order of resonant frequency and arranged alternately, thereby arranging the resonant frequencies of adjacent parallel coupled line resonators so as to be separated from each other, thereby reducing coupling between the parallel coupled line resonators.

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