JP2005318102A - Rfid tag and method for adjusting resonant frequency thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an RFID tag with a simple constitution capable of stably maintaining a desired resonant frequency, even when environmental changes occur, and also is capable of reducing costs, and to provide a method for adjusting its resonant frequency. <P>SOLUTION: The RFID tag 1 has a coil conductor pattern 12 operated by a prescribed resonant frequency and is provided with an FPC 11, the coil conductor pattern 12, a crossover pattern 13, and an IC 14. The coil conductor pattern 12 includes a detour pattern 12b, which is connected in parallel to a part of a linear conductor 12a constituting the main part of an antenna coil. The inductance of the overall coil conductor pattern 12 can be adjusted, by cutting off a prescribed position of the detour pattern 12b. By this, the resonant frequency of the RFID tag can be adjusted properly. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an RFID (Radio Frequency Identification) tag having a coil conductor pattern as an antenna coil that operates at a predetermined resonance frequency and a method for adjusting the resonance frequency.

  Conventionally, RFID tags have been used in fields such as article management. The RFID tag includes an antenna coil and an element such as an IC connected to the antenna coil. The antenna tag receives a predetermined frequency transmitted from the interrogator and activates the RFID tag to drive the element such as the IC. It is configured. Thus, communication can be performed between the RFID tag and the interrogator using radio waves, and data stored in the IC element can be read and new data can be written, which can be used for managing articles. .

Usually, in communication between an RFID tag and an interrogator, a predetermined frequency band such as a 13.56 MHz band is defined. When configuring the RFID tag, it is necessary to optimally adjust the resonance frequency by appropriately configuring the structure of the antenna coil and its peripheral circuit. For example, an antenna coil is formed on an FPC (Flexible Print Circuit Board), a capacitor is formed by an FPC base material and electrodes formed on both sides of the FPC, and the capacitor electrode is partially cut to reduce the area. A method of adjusting the resonance frequency of the RFID tag by modifying the changed capacitance value is known (see, for example, Patent Document 1).
JP 2003-187207 A

  In the RFID tag configured to adjust the resonance frequency by correcting the capacitance value of the capacitor formed on the FPC as in the conventional case, the characteristics of the base material of the FPC depend on, for example, environmental conditions such as temperature and humidity. Changes, the capacitance value of the capacitor fluctuates, and as a result, the resonance frequency fluctuates. In this case, for example, even when the resonance frequency of the RFID tag is adjusted under a predetermined temperature and humidity in the manufacturing process, if the environment where the RFID tag is actually used differs from the environment of the manufacturing process, the capacitance value of the capacitor May fluctuate and the resonance frequency may deviate from the value at the time of adjustment. As described above, the resonance frequency of the RFID tag is shifted due to environmental fluctuations, which causes a problem that the RFID tag cannot exhibit desired performance. In addition, since the RFID tag having the above-described conventional configuration is provided with a capacitor using both sides of the FPC, it is necessary to connect both sides of the FPC, so that the wiring structure becomes complicated and the cost of the RFID tag increases. Become.

  Therefore, the present invention has been made to solve these problems. In application of the present invention, even when environmental fluctuations such as temperature and humidity occur, an RFID tag that can maintain a desired resonance frequency stably, has a simple configuration, and can reduce costs, and a method for adjusting the resonance frequency The purpose is to provide.

  In order to solve the above problem, the RFID tag according to claim 1 is an RFID tag having a coil conductor pattern that operates at a predetermined resonance frequency, and the coil conductor pattern constitutes a main part of the antenna coil. A bypass pattern connected in parallel to a part of the linear conductor is included, and the inductance of the entire coil conductor pattern can be adjusted by cutting a predetermined position of the bypass pattern.

  According to the present invention, the resonance frequency of the RFID tag can be adjusted by adjusting the inductance of the coil conductor pattern as the antenna coil by cutting the bypass pattern. At this time, since the bypass pattern is connected in parallel to the linear conductor of the coil conductor pattern, the inductance can be easily adjusted by changing the cutting position of the bypass pattern. Therefore, a highly reliable RFID tag can be realized with a simple configuration and low cost by stably maintaining the resonance frequency even when fluctuations in temperature, humidity, and the like occur.

  The RFID tag according to claim 2 is the RFID tag according to claim 1, wherein a plurality of detour paths are arranged in parallel in the detour pattern, and the cutting is set at one end of each of the plurality of detour paths. The inductance of the entire coil conductor pattern can be adjusted in a plurality of stages by cutting at a cutting position selected from among the positions.

  According to the present invention, in addition to the operation of the above-described invention, when adjusting the inductance of the coil conductor pattern, it is only necessary to select a predetermined detour path after providing a plurality of detour paths. If the shape is set appropriately, the resonance frequency can be finely adjusted according to the characteristics of the RFID tag.

  The RFID tag according to claim 3 is the RFID tag according to claim 1 or 2, wherein the coil conductor pattern is formed on one surface of a flat FPC.

  According to this invention, in addition to the operation of the above-described invention, the coil conductor pattern is formed on one surface of the planar FPC, so that the wiring structure can be simplified and the low-cost RFID tag can be obtained. Can be realized.

  The RFID tag according to claim 4 is the RFID tag according to claim 1 or 2, wherein the coil conductor pattern is formed on one surface of the FPC wound around the magnetic core material. It is characterized by.

  According to this invention, in addition to the operation of the above-described invention, the antenna coil is configured by winding the FPC around the magnetic core material, so that a small RFID tag can be realized.

  The RFID tag according to claim 5 is the RFID tag according to claim 4, wherein the plurality of linear conductors are arranged in parallel on one surface of the FPC, and the FPC is wound around the magnetic core material. The adjacent linear conductors are electrically connected to each other so that an integrated linear conductor can be formed, and one end and the other end of the integrated linear conductor are electrically connected. A connecting conductor is further provided.

  According to this invention, in addition to the operation of the above-described invention, the FPC wound around the magnetic core material sequentially connects the adjacent linear conductors and configures the antenna coil using the connection conductor. By using only one of the surfaces, the influence of environmental fluctuations of the substrate can be greatly reduced, and the reliability of the RFID tag can be further improved.

  The method for adjusting the resonance frequency of the RFID tag according to claim 6 is a method for adjusting the resonance frequency of an RFID tag having a coil conductor pattern that operates at a predetermined resonance frequency, and comprises an antenna coil in the coil conductor pattern. A resonance frequency of the RFID tag is measured in a state including a bypass pattern connected in parallel to a part of the linear conductor to be determined, a cutting method of the bypass pattern is determined based on a measurement result, and the cutting method of the bypass pattern is determined according to the determined cutting method The resonance frequency is adjusted by cutting a bypass pattern.

  The method for adjusting the resonance frequency of the RFID tag according to claim 7 is the method for adjusting the resonance frequency of the RFID tag according to claim 6, wherein a plurality of bypass paths are arranged in parallel in the bypass pattern, A plurality of cutting positions are respectively set at one end of the plurality of detour paths, and as a detour pattern cutting method, the presence or absence of cutting of the detour pattern is determined, and a predetermined cutting position is selectively selected from the plurality of cutting positions. It is characterized by determining.

  According to the present invention, among the coil conductor patterns of the RFID tag, the bypass pattern connected in parallel to a part of the linear conductor is cut at a predetermined position so that the inductance can be adjusted. Even if this occurs, after adjusting the desired resonance frequency in conjunction with the inductance, an RFID tag and a method for adjusting the resonance frequency that can keep the resonance frequency stable, have a simple structure, and can reduce costs It becomes possible.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. In this embodiment, a case where the present invention is applied to two types of a flat RFID tag without a magnetic core material around which an antenna coil is wound and a plate-like RFID tag with a magnetic core material around which an antenna coil is wound will be described. To do. The structure of the planar RFID tag is shown in FIG. 1, and the structure of the plate-like RFID tag is shown in FIGS.

  First, FIG. 1 is a diagram illustrating a configuration of a planar RFID tag 1 according to the present embodiment. The RFID tag 1 shown in FIG. 1 has a configuration in which a coil conductor pattern 12 is formed on an FPC 11 formed in a square planar shape and operates as an antenna coil having a desired resonance frequency. The RFID tag 1 having the configuration shown in FIG. 1 is formed in a card shape, for example, in an integrated state inside the case.

  The FPC 11 includes a coil conductor pattern 12 formed on one surface of a base material on which a flexible resin is formed with a thickness of about 30 μm, and a crossover pattern 13 formed on the other surface. As the resin for the base material of the FPC 11, for example, PET, PI, PEN, liquid crystal polymer, or the like is used. The coil conductor pattern 12 formed on the FPC 11 is connected to an IC 14 disposed at a predetermined location. The IC 14 plays a role of transmitting predetermined data in response to a request from the interrogator and storing data transmitted from the interrogator.

  The coil conductor pattern 12 formed on one surface of the FPC 11 includes a linear conductor 12a constituting a main part of the antenna coil and a bypass pattern 12b as a conductor pattern that partially bypasses the linear conductor 12a. In the example of FIG. 1, the bypass pattern 12b has four bypass paths arranged in parallel, and plays a role of adjusting the resonance frequency of the antenna coil by cutting a predetermined position of the bypass pattern 12b. With such a configuration, the RFID tag 1 according to the present embodiment does not require a capacitor for adjusting the resonance frequency. The method for adjusting the resonance frequency by cutting the bypass pattern 12b will be described later in detail.

  The crossover pattern 13 functioning as a connection conductor plays a role of constituting an integral antenna coil by electrically connecting two predetermined portions of the coil conductor pattern 12. The crossover pattern 13 needs to be provided on the back surface of the FPC 11 in order to avoid crossing with each part of the other linear conductor 12a.

  The coil conductor pattern 12 and the crossover pattern 13 formed on the FPC 11 are formed by, for example, etching of copper or aluminum or printing using a silver paste. The crossover pattern 13 is electrically connected to the coil conductor pattern 12 through the base material of the FPC 11 at two locations, one end and the other end.

  On the other hand, FIG. 2 is a perspective view showing the structure of the plate-like RFID tag 2 according to the present embodiment. FIG. 3 is a diagram showing the configuration of the FPC 22 in the RFID tag 2 of FIG. As shown in FIG. 2, the plate-like RFID tag 2 according to the present embodiment has a structure in which an FPC 22 is wound around a magnetic core material 21 formed in a plate shape. As shown in FIG. 3, the FPC 22 is formed with a coil conductor pattern 23 constituting a main part as an antenna coil. The coil conductor pattern 23 includes a linear conductor 23a and a bypass pattern 23b. With this configuration, the RFID tag 2 operates as an antenna coil having a desired resonance frequency, like the RFID tag 1 of FIG. In general, the RFID tag 2 having a structure as shown in FIG. 2 is formed in a card shape having a thickness in an integrated state inside a resin case.

  In FIG. 2, the magnetic core material 21 is preferably formed using ferrite, a ferrite kneaded resin, an amorphous sheet, or the like.

  The FPC 22 can be formed of the same material as that of the FPC 11 in FIG. 1, but the FPC 22 in FIG. 3 only has a coil conductor pattern 23 formed on one surface and a crossover pattern on the other surface. Is not formed. On the other hand, the RFID tag 1 of FIG. 2 is configured to electrically connect the end 23c (FIG. 3) and the end 23d of the linear conductor 23a by the connecting conductor 24. In addition to the case where the connecting conductor 24 is formed using the FPC attached to the FPC 22, the connecting conductor 24 may be formed so as to be able to be joined to the FPC 22 using another wire member or other conductor member.

  An IC 25 arranged at a predetermined location is connected to the coil conductor pattern 23 formed on the FPC 22. The IC 25 has the same function as the IC 14 of FIG.

  When the FPC 22 is wound around the magnetic core material 21, the surface of the FPC 22 on which the coil conductor pattern 23 is formed may be disposed on either the outer side or the inner side with respect to the magnetic core material 21. At this time, as shown in FIG. 3, it is necessary to join the ends of the linear conductors 23 a adjacent to each other on the side surface of the magnetic core material 21 in a state where the FPC 22 is wound around the magnetic core material 21. Thus, when joining the edge parts of the linear conductor 23a, what is necessary is just to electrically join by soldering, ultrasonic welding, etc. With this configuration, the linear conductor 23a is integrated as an antenna coil, and the RFID tag 2 can be operated at a desired resonance frequency.

  Next, a method of cutting the detour patterns 12b and 23b when adjusting the resonance frequencies of the above-described two types of RFID tags 1 and 2 will be described. In the following, the case of the RFID tag 1 of FIG. 1 will be described as a representative. However, since the basic adjustment method of the resonance frequency is common to the RFID tag 2 as well, the following description can be applied.

  FIG. 4 is an enlarged view of the periphery of the detour pattern 12 b in the configuration example of the coil conductor pattern 12 of the RFID tag 1. In the example shown in FIG. 4, the coil conductor patterns 12 are arranged in the order of the detour paths P1, P2, P3, and P4 from one end of the coil conductor pattern 12, and are in a positional relationship in which they are connected in parallel. When cutting the detour pattern 12, four cutting positions C1 to C4 that are close to one end of the detour paths P1 to P4 are set. By changing these cutting positions C1 to C4, the number of detour paths connected to the coil conductor pattern 12 can be increased or decreased.

  That is, when cutting the detour pattern 12b, all the detour paths P1 to P4 are not connected in parallel to the linear conductor 12a when cut at the cutting position C1, and only three detour paths P1 are linear when cut at the cutting position C2. When connected at the cutting position C3, the two bypass paths P1 and P2 are connected in parallel to the linear conductor 12a, and when disconnected at the cutting position C4, the three bypass paths P1 to P3 are connected in parallel to the linear conductor 12a. Connected. Thus, the inductance of the entire coil conductor pattern 12 is changed by changing the number of bypass paths P1 to P4 connected in parallel (or the number of bypass paths P1 to P4 to be disconnected) according to the cutting positions C1 to C4. Can be adjusted. As a result, the resonance frequency of the RFID tag 1 that changes in conjunction with the inductance of the coil conductor pattern 12 can be adjusted.

  Here, a method for adjusting the resonance frequency of the RFID tag 1 will be described with reference to FIG. FIG. 5 is a flowchart illustrating an example of processing performed in the manufacturing process of the RFID tag 1, for example. When the process of FIG. 5 is started, the resonance frequency of the RFID tag 1 is measured using a measuring device capable of emitting radio waves of an arbitrary frequency to the RFID tag 1 to be manufactured (step S101). Then, a difference between the desired resonance frequency Fx based on the specification of the RFID tag 1 and the resonance frequency Fm measured in step S101 is obtained, and the amount of frequency deviation is determined (step S102).

  Next, based on the frequency shift amount determined in step S102, a cutting method (cutting presence / absence, cutting position) for the detour pattern 12b is determined (step S103). As the cutting method in step S103, taking FIG. 4 as an example, five methods can be selected: when the detour pattern 12b is not cut and when cutting is performed at any one of the cutting positions C1 to C4. The case where the detour pattern 12b is not cut is determined when the frequency shift amount is substantially zero. On the other hand, in order to determine the cutting position in step S102, it is necessary to grasp in advance the resonance frequency characteristics corresponding to the cutting position in the detour pattern 12b for the RFID tag 1 to be manufactured. Will be described later.

  Next, according to the cutting method determined in step S103, the detour pattern 12b that needs to be cut is cut (step S104). In the cutting process in step S104, for example, when cutting the detour pattern 12b, there is a method of cutting a predetermined portion using a router or the like, or irradiating a laser to cut the predetermined portion. If it is determined in step S103 that the detour pattern 12b is not cut, the cutting process in step S104 is omitted.

  Next, the resonance frequency is measured for the RFID tag 1 subjected to the cutting process in step S104 in the same manner as in step S101 (step S105). If it is determined that the measured resonance frequency is within the preset allowable range after determining the above-described frequency deviation amount (step S106: YES), the adjustment of the resonance frequency of the RFID tag 1 is completed. As a result, the processing of FIG. On the other hand, when it is determined that the measured resonance frequency is out of the preset allowable range (step S106: NO), a predetermined process defined in the manufacturing process is performed (step S107). In step S107, for example, it may be determined that the processing after step S103 is performed again.

  Next, FIG. 6 is a diagram showing a specific example of the state of the detour pattern 12b actually cut in step S104 in the configuration example shown in FIG. In FIG. 6, the detour pattern 12b in a state of being cut at the cutting position C4 of FIG. 4 is shown. In this case, the coil conductor pattern 12 of the RFID tag 1 is in a state where three detour paths P1, P2, and P3 are connected in parallel to the linear conductor 12a. That is, this corresponds to a state in which the detour path P4 is disconnected from the linear conductor 12a.

  Next, the relationship between the cutting method of the detour patterns 12b and 23b in the RFID tags 1 and 2 and the characteristics of the RFID tags 1 and 2 will be described. In Table 1 below, the RFID tag 2 having the structure of FIG. 2 is targeted, and the verification results by experiments on the relationship between the cutting positions C1 to C4 shown in FIG. 4 in the bypass pattern 23b and the inductance and resonance frequency of the RFID tag 2 are shown. Show.

表１に示されるように、迂回パターン２３ｂを切断しない状態でコイル導体パターン２３のインダクタンスが最小となり、切断位置に応じて線状導体２３ｂに並列接続される迂回経路数が減少するにつれ、インダクタンスが次第に大きくなる。このように、ＲＦＩＤタグ２では、元の線状導体２３ａで定まるインダクタンスに比べ、迂回経路を並列接続させることによってインダクタンスが減少する作用がある。一方、ＲＦＩＤ１の共振周波数は、インダタンスと逆の変化をするので、迂回パターン２３ｂを切断しない状態で最大となり、切断位置に応じて線状導体２３ｂに並列接続される迂回経路数が減少するにつれ、共振周波数が次第に小さくなる。

As shown in Table 1, the inductance of the coil conductor pattern 23 is minimized without cutting the bypass pattern 23b, and the inductance decreases as the number of bypass paths connected in parallel to the linear conductor 23b decreases according to the cutting position. Gradually grows. As described above, the RFID tag 2 has an effect of reducing the inductance by connecting the detour paths in parallel as compared with the inductance determined by the original linear conductor 23a. On the other hand, since the resonance frequency of RFID1 changes opposite to the inductance, it becomes the maximum without cutting the bypass pattern 23b, and as the number of bypass paths connected in parallel to the linear conductor 23b decreases according to the cutting position, The resonance frequency is gradually reduced.

  It has been confirmed that the characteristics shown in Table 1 change according to the shape of the bypass pattern 23b. Therefore, in the configuration of FIG. 2, parameters related to the shape of the bypass pattern 23b are set so that a desired resonance frequency adjustment range can be obtained within the range from the state where the bypass pattern 23b is not cut to the state of the cutting position C1. There is a need to. Specifically, regarding the detour pattern 23b, parameters such as the number of detour paths, the line width and interval of the detour paths, and the length of the detour paths may be appropriately set to optimize the adjustment range of the resonance frequency.

  Next, the influence of the environment such as temperature and humidity on the resonance frequency of the RFID tag 2 will be described. FIG. 7 is a diagram illustrating temperature characteristics of the resonance frequency of the RFID tag 2. In FIG. 7, an RFID tag 2 having the configuration of the present embodiment (shown by (A) in the figure) and an RFID tag configured to adjust the resonance frequency by a capacitor as in the past (in the figure) (B) is compared, and the amount of resonance frequency deviation in the temperature range of −10 to 70 ° is shown. The frequency shift amount in FIG. 7 is obtained by determining the ratio f / fx between the resonance frequency fx at the reference temperature and the frequency f measured at each temperature.

  As shown in FIG. 7, it can be seen that the amount of frequency deviation due to temperature change is markedly smaller in the RFID tag 2 of the present embodiment than in the RFID tag having the conventional configuration. In the conventional configuration, since the capacitor for adjusting the resonance frequency is provided by providing electrodes on both sides of the FPC, the characteristics of the FPC base material change due to the temperature change, resulting in the capacitance of the capacitor. Since the value fluctuates, the frequency shift amount is considered to increase. On the other hand, in the configuration of the present embodiment, no capacitor is provided in the FPC, and the inductance of the coil conductor pattern 12 on one side is adjusted, so that it is not affected by the temperature change of the base material of the FPC. As shown in FIG. 7, good temperature characteristics can be obtained.

  Next, FIG. 8 is a diagram illustrating humidity characteristics of the resonance frequency of the RFID tag 2. Also in FIG. 8, the RFID tag 2 having the configuration of the present embodiment (shown by (A) in the figure) is compared with the RFID tag having a capacitor as in the past (shown by (B) in the figure). , Respectively, shows the frequency shift amount of the resonance frequency within the elapsed time of 0 to 250 (h). Here, in FIG. 8, it is assumed that the FPC substrate gradually absorbs moisture over a long period of time under a predetermined moisture absorption condition (40 ° C., 93% RH).

  As is clear from FIG. 8, the RFID tag 2 of the present embodiment is greatly improved in terms of frequency deviation due to humidity change as compared with the RFID tag having the conventional configuration. In this case as well, it is considered that the FPC base material is greatly affected by the humidity change in the conventional configuration and the capacitance value fluctuates, resulting in an increase in the frequency shift amount. On the other hand, in the configuration of the present embodiment, the above-described configuration is not affected by the humidity change of the base material of the FPC, so that good humidity characteristics can be obtained as shown in FIG.

  Next, a modified example of the RFID tag 1 according to this embodiment will be described. In the present embodiment, the bypass pattern 12b of the coil conductor pattern 12 of the RFID tag 1 is not limited to the above-described configuration, and there are various variations. 9 to 12 show three types of modifications when the configuration of the detour pattern 12 of FIG. 4 is modified.

  FIG. 9 is a diagram illustrating a first modification of the bypass pattern 12b. In the first modification, the four detour paths P11 to P14 in the detour pattern 12b are arranged so as to extend in the direction perpendicular to the direction of the linear conductor 12a. That is, the directions of the four detour paths P1 to P4 extending in the direction parallel to the linear conductor 12a in FIG. 4 are changed by 90 °. Cutting positions C11 to C13 are set in the detour pattern 12b at three locations on the far end side of the linear conductor 12a.

  In the first modification, the inductance of the entire coil conductor pattern 12 can be adjusted by changing the cutting positions C11 to C13. At this time, in addition to cutting only one of the cutting positions C11 to C13, a plurality of cutting positions C11 to C13 may be cut. For example, all of the cutting positions C11 to C13 are cut. May be. Further, the number of cutting positions is not limited to three, and an arbitrary number of cutting positions can be set by changing the number of detour paths.

  FIG. 10 is a diagram illustrating a second modification of the bypass pattern 12b. In the second modification, the configuration of the detour pattern 12b itself including the detour routes P21 to P24 is the same as that in FIG. On the other hand, the cutting positions C21 to C23 set in the bypass pattern 12b are opposite to those in the case of FIG. 9, and are set on the near end side of the linear conductor 12a. In the case of the second modified example, as in the first modified example, the inductance of the entire coil conductor pattern 12 can be adjusted by changing the cutting positions C21 to C23.

  FIG. 11 is a diagram illustrating a third modification of the bypass pattern 12b. In the third modified example, the configuration of the detour pattern 12b itself including the detour routes P31 to 34 is the same as that of FIGS. 9 and 10, but the cutting positions C31 to C33 set in the detour pattern 12b are shown in FIGS. The setting is a combination of 10. That is, the three cutting positions C31 to C33 are set alternately on the far end side and the near end side of the linear conductor 12a.

  In addition, in the case of FIG. 10 and FIG. 11, in addition to the case of cutting only one of a plurality of cutting positions, it is possible to cut a plurality of points, and further, by changing the number of detour paths, A number of cutting positions can be set.

  FIG. 12 is a diagram illustrating a fourth modification of the detour pattern 12. In the fourth modification, unlike FIGS. 9 to 11, no detour path is formed in the detour pattern 12b, and the entire pattern is formed of a rectangular conductor pattern. A linear cutting position C4 is set in the detour path 12b. And the inductance of the coil conductor pattern 12 whole can be adjusted by changing suitably the cutting position 14 set to the detour path | route 12b. For example, the distance between the cutting position C4 and the linear conductor 12a may be finely adjusted in the manufacturing process. In the fourth example, the cutting position 14 can be freely set without being restricted by the pattern shape, which is suitable for fine adjustment of the inductance.

  In the first to fourth modified examples described above, when the bypass pattern 12b is compared with the same size, it is confirmed that the amount of change in inductance accompanying the change of the cutting position is smaller than that in the configuration of FIG. It was. Further, in the first to fourth modifications, the amount of change in inductance is further reduced in the second and fourth modifications compared to the first and third modifications. Therefore, when the amount of change in inductance is increased to ensure a wide adjustment range of the resonance frequency, it is desirable to provide the detour pattern 12b with a configuration corresponding to FIGS. However, when adjusting the resonance frequency in a narrow range, the first to fourth modifications may be adopted. Further, depending on the cutting method in the manufacturing process, it may be more appropriate to adopt the fourth modification.

It is a figure which shows the structure of the planar RFID tag which concerns on this embodiment. It is a perspective view which shows the structure of the plate-shaped RFID tag which concerns on this embodiment. It is a figure which shows the structure of FPC in the RFID tag of FIG. It is a figure which shows the enlarged view around a detour pattern among the structural examples about the coil conductor pattern of an RFID tag. It is a figure explaining the adjustment method of the resonant frequency of a RFID tag, and is a flowchart which shows an example of the process performed in the manufacturing process of a RFID tag, for example. FIG. 6 is a diagram showing a specific example of the state of the detour pattern 12b actually cut in step S104 of FIG. 5 in the configuration example shown in FIG. It is a figure which shows the temperature characteristic of the resonant frequency of a RFID tag. It is a figure which shows the humidity characteristic of the resonant frequency of a RFID tag. It is a figure which shows the 1st modification of a detour pattern. It is a figure which shows the 2nd modification of a detour pattern. It is a figure which shows the 3rd modification of a detour pattern. It is a figure which shows the 4th modification of a detour pattern.

Explanation of symbols

1, 2 ... RFID tag 11 ... FPC
12 ... Coil conductor pattern 12a ... Linear conductor 12b ... Detour pattern 13 ... Crossover pattern 14 ... IC
21 ... Magnetic core 22 ... FPC
23 ... Coil conductor pattern 23a ... Linear conductor 23b ... Detour pattern 23c, 23d ... End 24 of linear conductor ... Connection conductor 25 ... IC
P1, P2, P3, P4 ... detour paths C1, C2, C3, C4 ... cutting position

Claims (7)

An RFID tag having a coil conductor pattern that operates at a predetermined resonance frequency,
The coil conductor pattern includes a bypass pattern connected in parallel to a part of the linear conductor constituting the main part of the antenna coil, and the inductance of the entire coil conductor pattern is adjusted by cutting a predetermined position of the bypass pattern An RFID tag characterized by being configured.   A plurality of bypass paths are arranged in parallel in the bypass pattern, and an inductance of the entire coil conductor pattern is obtained by cutting at a cutting position selected from the cutting positions set at one end of each of the plurality of bypass paths. The RFID tag according to claim 1, wherein the RFID tag is configured to be adjustable in a plurality of stages.   3. The RFID tag according to claim 1, wherein the coil conductor pattern is formed on one surface of a flat FPC.   The RFID tag according to claim 1 or 2, wherein the coil conductor pattern is formed on one surface of an FPC wound around a magnetic core material. A plurality of the linear conductors are arranged in parallel on one surface of the FPC, and are integrated by electrically connecting adjacent linear conductors in a state where the FPC is wound around the magnetic core material. It is configured to be able to form a conductor,
5. The RFID tag according to claim 4, further comprising a connection conductor that electrically connects one end and the other end of the integrated linear conductor. A method for adjusting a resonance frequency of an RFID tag having a coil conductor pattern that operates at a predetermined resonance frequency,
A resonance frequency of the RFID tag is measured in a state including a detour pattern connected in parallel to a part of a linear conductor constituting the antenna coil of the coil conductor pattern, and a method of cutting the detour pattern based on a measurement result A method for adjusting a resonance frequency of an RFID tag, wherein the resonance frequency is adjusted by determining and cutting the bypass pattern according to the determined cutting method. In the bypass pattern, a plurality of bypass paths are arranged in parallel, and a plurality of cutting positions are set at one end of the plurality of bypass paths,
7. The RFID tag resonance according to claim 6, wherein, as the detour pattern cutting method, whether or not the detour pattern is cut is determined, and a predetermined cutting position is selectively determined from the plurality of cutting positions. How to adjust the frequency.

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