JP2015026915A - Antenna and antenna manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foldable antenna.SOLUTION: An antenna 100 includes a dielectric layer 2, bases 3, resonators 4 and conductive layers 5. The plurality of bases 3 are formed in juxtaposition in an X direction on the dielectric layer 2, apart from one another. The conductive layers 5 constituting open transmission lines are respectively disposed on the plurality of bases 3. The resonators 4 are respectively disposed on the plurality of bases 3 and connected to the conductive layers 5. The resonators 4 disposed on adjacent bases 3 are electromagnetically coupled.

Description

  The present invention relates to an antenna.

  An antenna that leaches out an electromagnetic field only in an adjacent region has been proposed for use in sensing in an adjacent region. In such an application, a flat antenna may be used. In the antenna on a flat plate, for example, a configuration in which electromagnetic waves travel between two conductive layers arranged opposite to each other is used.

  In addition, a configuration in which one conductive layer of a flat antenna is a mesh-like conductive layer has been proposed (Patent Document 1). In this example, a dielectric layer is provided between two conductive layers. In this case, electromagnetic waves traveling through the conductive layer (dielectric layer) are leached from the mesh-shaped conductive layer. The intensity of the leached electromagnetic field decreases exponentially according to the distance from the mesh-like conductive layer. Thereby, the antenna can hold | maintain an electromagnetic field only to the area | region which adjoins.

JP 2010-114696 A

  However, the inventors have found that the configuration of Patent Document 1 has the following problems. In general, an antenna on a flat plate has a large area depending on the application, so it is desirable that the antenna can be folded and stored and transported. However, in the configuration of Patent Document 1, it is necessary to increase the thickness of the conductive layer and the dielectric layer in order to maintain the mechanical strength of the antenna. In this case, the rigidity of the conductive layer and the dielectric layer is increased, and the antenna cannot be bent. Therefore, the configuration of Patent Document 1 is not suitable for increasing the size of a flat antenna.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to realize a foldable antenna.

  An antenna that is one embodiment of the present invention includes a flexible dielectric layer, a plurality of base portions formed on the flexible dielectric layer, and spaced apart from each other and arranged in a certain direction, and the plurality of the plurality of platform portions. A conductive layer constituting an open-type transmission line provided on each of the pedestal portions; and a plurality of resonators provided on each of the plurality of pedestal portions and connected to the conductive layer, and adjacent to the pedestal The resonators of the part are electromagnetically coupled.

  According to an antenna manufacturing method which is one embodiment of the present invention, a plurality of bases are formed on a flexible dielectric layer so as to be spaced apart from each other and aligned in a certain direction, thereby forming an open transmission line. A layer is formed on each of the plurality of base parts, and a plurality of resonators are formed on each of the plurality of base parts in connection with the conductive layer. It is electromagnetically coupled.

  According to the present invention, a foldable antenna can be realized.

1 is a perspective view schematically showing a configuration of an antenna 100 according to a first embodiment. 1 is a plan view schematically showing a configuration of an antenna 100 according to a first embodiment. 1 is a front view schematically showing a configuration of an antenna 100 according to a first embodiment. It is a front view which shows typically the aspect at the time of winding up the antenna 100 concerning Embodiment 1. FIG. FIG. 6 is a plan view of the vicinity of a resonator 4 showing the simulation conditions of the antenna 100. It is a graph which shows the simulation result of the insertion loss of the antenna 100. FIG. FIG. 6 is an enlarged view of a main part in the vicinity of a resonator of an antenna 200 according to a second embodiment. FIG. 6 is an enlarged view of a main part in the vicinity of a resonator of an antenna 300 according to a third embodiment. FIG. 10 is a configuration diagram schematically showing a configuration of an article management system 4000 according to a fourth embodiment. FIG. 6 is a top view schematically showing a configuration of an article management system 4000 according to a fourth embodiment. It is a front view of the article | item management system 4000 concerning Embodiment 4. FIG. It is a side view of the article management system 4000 concerning Embodiment 4. It is a table | surface which shows the dependence regarding the distance (gamma) normalized with wavelength (lambda) about the relative intensity | strength of the quasi-electrostatic field in the electric field E ( _theta) , an induction electric field, and a radiation electric field. It is a top view which shows typically the structure of the article | item management system 5000 concerning Embodiment 5. FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted as necessary.

Embodiment 1
The antenna 100 according to the first embodiment will be described. FIG. 1 is a perspective view schematically showing the configuration of the antenna 100 according to the first embodiment. FIG. 2 is a plan view schematically showing the configuration of the antenna 100 according to the first embodiment. FIG. 3 is a front view schematically showing the configuration of the antenna 100 according to the first embodiment. The antenna 100 includes a conductive layer 1, a dielectric layer 2, a base 3, a resonator 4, and a conductive layer 5. 1 to 3, the antenna 100 is formed to extend in the X direction, but only a part of the antenna 100 is displayed for simplification of the drawing.

  The conductive layer 1 is a sheet-like member made of a conductive material such as aluminum, and is a flexible member that can be easily bent. The dielectric layer 2 is formed on the conductive layer 1. The dielectric layer 2 is a sheet-like member made of a dielectric material such as highly foamed polyethylene, and is a flexible member that can be easily bent.

  The base parts 3 are arranged side by side. In FIG. 1, the base 3 is arranged side by side in the X direction, which is a direction parallel to the main surface of the dielectric layer 2. In FIG. 1, the Y direction perpendicular to the X direction and parallel to the main surface of the dielectric layer 2 and the Z direction perpendicular to the X direction and the Y direction are shown together. The pedestal 3 has a slope 31 extending in the Y direction. The base 3 is formed such that the width of the top 32 is equal to the width of the bottom 33 or smaller than the width of the bottom 33. That is, the valley portion 34 is formed so as to be sandwiched between the slopes 31 of the adjacent base portions 3. The base 3 is made of a dielectric material, for example. At this time, the base part 3 may have a hollow structure.

  Resonators 4 are formed on the two slopes 31 of the single base 3. The resonator 4 is configured as a parallel coupled transmission line. It is desirable that the two resonators 4 included in one base part 3 are formed apart from each other in the Y direction. Two resonators 4 included in one base 3 are electrically connected via a conductive layer 5 formed on the top 32 and the slope 31. Further, the resonators 4 of the two adjacent base parts 3 are formed so as to face each other with the valley part 34 interposed therebetween. The resonators 4 that face each other across the valley 34 are electromagnetically coupled by resonating. Thereby, the conductive layer 5 and the conductive layer 1 of the plurality of base parts 3 can function as a microstrip line which is one form of an open transmission line. With this configuration, it is possible to radiate an electromagnetic field to an adjacent region in the Z direction in FIGS.

  As described above, the conductive layer 1 and the dielectric layer 2 of the antenna 100 are formed of a flexible member. Therefore, the antenna 100 can be wound around an axis parallel to the Y direction. FIG. 4 is a front view schematically showing an aspect when the antenna 100 according to the first embodiment is wound. As shown in FIG. 4, the conductive layer 1 and the dielectric layer 2 below the trough 34 are bent, and as a result, the trough 34 is narrowed so that the antenna 100 is wound around an axis parallel to the Y direction. Can be stored. Therefore, according to this structure, the antenna which can be folded is realizable.

  Further, in this configuration, the mechanical strength of the antenna 100 can be increased without changing the thickness of the conductive layer 1 and the dielectric layer 2 by increasing the thickness of the base portion 3. Therefore, according to this configuration, the mechanical strength of the antenna can be increased without impairing the folding performance.

  Next, a simulation regarding the insertion loss of the antenna 100 will be described. FIG. 5 is a plan view of the vicinity of the resonator 4 showing the simulation conditions of the antenna 100. In this simulation, the thicknesses of the dielectric layer 2 and the base 3 were both 1 mm and the dielectric constant was 4.3. Further, the dimensions shown in FIG. 5 are as follows: W1 = 0.5 mm, W2 = 22.5 mm, W3 = 3 mm, W4 = 8 mm, W5 = 1.74 mm, W6 = 3.92 mm, L1 = 115 mm, L2 = 88 mm, L3 = 32 mm.

FIG. 6 is a graph showing a simulation result of the insertion loss of the antenna 100. In Figure 6, between the two resonators, the S parameter S ₁₁ showing the reflection loss by broken lines, displaying the S ₂₁ indicating the insertion loss by the solid line. As shown in FIG. 6, when the band to be used is in the vicinity of 950 MHz, the insertion loss is about -0.4 dB, and good signal transmission can be realized.

Embodiment 2
An antenna 200 according to the second embodiment will be described. FIG. 7 is an enlarged view of a main part near the resonator of the antenna 200 according to the second embodiment. The antenna 200 has a configuration in which the resonator 4 of the antenna 100 is replaced with a resonator 6. Since the configuration of the antenna 200 other than the resonator is the same as that of the antenna 100, description thereof is omitted.

  In the antenna 100 according to the first embodiment, the resonator 4 is configured as a parallel coupled transmission line resonator. On the other hand, in the antenna 200, the resonator 6 is configured as an open ring resonator. In this example, the resonators 6 facing each other with the valley portion 34 interposed therebetween are formed so that the open portion of the ring faces the valley portion 34 side.

  As shown in this embodiment mode, an antenna that can be wound and housed similarly to the antenna 100 can be configured using an open ring resonator as well as a parallel coupled transmission line resonator. Is possible.

Embodiment 3
An antenna 300 according to the third embodiment will be described. FIG. 8 is an enlarged view of a main part near the resonator of the antenna 300 according to the third embodiment. The antenna 300 has a configuration in which the resonator 4 of the antenna 100 is replaced with a resonator 7. Since the configuration of the antenna 300 other than the resonator is the same as that of the antenna 100, description thereof is omitted.

  In the antenna 100 according to the first embodiment, the resonator 4 is configured as a parallel coupled transmission line resonator. On the other hand, in the antenna 300, the resonator 7 is configured as a spiral coil resonator. In this example, the resonators 7 facing each other with the valley portion 34 interposed therebetween are formed such that the spiral coil winding direction is reversed.

  As shown in the present embodiment, an antenna that can be rewound and housed similarly to the antenna 100 is configured by using not only a parallel coupled transmission line resonator but also a spiral coil resonator resonator as a resonator. It is possible.

Embodiment 4
An article management system 4000 according to the fourth embodiment will be described. The article management system 4000 incorporates the antenna described in the above embodiment. FIG. 9 is a configuration diagram schematically illustrating a configuration of an article management system 4000 according to the fourth embodiment. An article management system 4000 according to the fourth embodiment includes an antenna 400, a spacer 402, an RFID reader 403, an RF tag 404, an article to be managed 405, and a matching termination resistance Rt.

  The antenna 400 has the same configuration as the antenna 100 according to the first embodiment. In the present embodiment, an example in which the antenna 400 includes four base parts 3 will be described. The conductive layer 5 disposed on the top portion 32 of the base portion 3 functions as a reader antenna for reading the RF tag 404. The RF tag 404 is disposed above each conductive layer 5 via, for example, a non-conductive spacer 402.

  The RFID reader 403 is connected to the end of the conductive layer 5 of the base 3 located at one end of the four bases 3. The RFID reader 403 transmits a transmission signal to the conductive layer 5 and receives a response signal output from the tag antenna of the RF tag 404 via the conductive layer 5. The RFID reader 403 sends the generated transmission signal to the conductive layer 5 and transmits the transmission signal to the tag antenna of the RF tag 404 that is electromagnetically coupled to the conductive layer 5. On the other hand, the RFID reader 403 receives a response signal generated by the RF tag 404 transmitted to the conductive layer 5 by wireless communication. A matching termination resistor Rt is connected to the end of the conductive layer 5 of the base part 3 located at the other end of the four base parts 3.

  The RF tag 404 is installed at a position where the object to be managed can be seen from the conductive layer 5 in a state where the article to be managed is placed in the vicinity and is electromagnetically coupled to the conductive layer 5. Although an example in which a passive tag is used as the RF tag 404 is described in this embodiment, an active tag can also be used as the RF tag 404. When the passive tag receives a signal for inquiring an ID (hereinafter referred to as tag information) from the conductive layer 5, the passive tag automatically uses a power circuit (not shown) in the chip by a part of the signal obtained via the tag antenna. Generates power to operate the chip. Further, the passive tag decodes a part of the received signal and generates reception data. The passive tag collates the tag information stored in the memory circuit in the chip with the received data. If the tag information matches the received data, the passive tag operates the modulation circuit (not shown) to generate the modulated signal. And the modulation signal is transmitted to the conductive layer 5 through the tag antenna.

  The management target article 405 is installed at a position where the tag antenna of the RF tag 404 is electromagnetically coupled. Hereinafter, the position where the management target article 405 is placed is referred to as a management target article placement area 410. The management target article 405 preferably includes a material having a high dielectric constant such as moisture or a metal, but is not limited thereto. More specifically, in addition to PET bottle drinks, can drinks, snack foods packed in aluminum packages, bundles of thick paper such as books, rice balls, bread, side dishes in plastic packs, human bodies with hands and feet, and shoes It can be an article. The correspondence to various articles such as an article having a lot of moisture is caused by using an RFID system in a UHF band or a microwave band. In an RFID system used in a frequency band of 13.56 MHz or lower, first, the skin thickness becomes long, so the reaction to moisture becomes extremely weak. In these frequency bands, electromagnetic induction is used for coupling between the reader and the tag. Since electromagnetic induction is coupling by a magnetic field, it is sensitive to relative permeability, but is not sensitive to differences in relative permittivity. Therefore, even if the relative dielectric constant of water is as high as 80, the operation of the tag antenna does not react sensitively to moisture in the case of electromagnetic induction. In general, the relative permeability takes a value in the vicinity of 1 unless many of the substances are magnetic materials. On the other hand, the dielectric constant is often very different from 1. Furthermore, unlike the RFID system that relies only on electromagnetic induction, the present invention uses the electromagnetic field components of the quasi-electrostatic magnetic field, the induction electromagnetic field, and the radiated electromagnetic field. Get higher. For example, as in an RFID system using electromagnetic induction, it is not necessary to perform alignment so that the magnetic flux generated by the reader antenna penetrates the coiled antenna of the tag, or the demand for alignment is reduced. In addition, as the frequency band used is high, the data rate is also higher than in the case of an RFID system using electromagnetic induction. Therefore, it is desirable to use UHF band or microwave band RFID systems. Although the RF tag 404 is covered with a plastic plate or the like, there is a case where a minute amount of moisture such as condensation has adhered to the surface of the RF tag. It is also possible to eliminate the influence of a minute amount of moisture by adjusting the coupling coefficient between them.

  Here, the operation of the article management system 4000 according to the fourth embodiment will be described. The article management system 4000 detects the presence / absence of an article to be managed based on the tag information of the RF tag 404. In performing this detection operation, the article management system 4000 first sends a tag information read command from the RFID reader 403 through the conductive layer 5 as a transmission signal.

  Subsequently, the RF tag 404 receives a transmission signal via the conductive layer 5. Then, the RF tag 404 generates power using a part of the received signal and starts operation. Thereafter, the RF tag 404 decodes the received signal and reproduces the received data included in the received signal. The RF tag 404 refers to the received data and the tag information included in the built-in storage circuit, and sends the modulated signal as a response signal to the conductive layer 5 if the tag information and the received data match.

  At this time, the RFID reader 403 determines the presence / absence of an article to be managed based on the presence / absence of a response signal from the RF tag 404 corresponding to the transmitted tag information read command. More specifically, if the signal strength of the response signal from the RF tag 404 is strong, the RFID reader 403 determines that there is an article to be managed, and if the signal strength of the response signal from the RF tag 404 is weak, the article to be managed is Judge that there is no. For example, in the example shown in FIG. 9, since there is no article to be managed on the RF tag 404 arranged on the rightmost side of the drawing, this RF tag 404 can send a response signal with a strong signal strength. Yes, the RFID reader 403 determines that there is no managed object 405 at the position of the RF tag 404. On the other hand, since the management target article 405 is placed on the other three RF tags 404 in FIG. 9, the signal strength of the response signals transmitted by the other three RF tags 404 is weakened. Therefore, the RFID reader 403 determines that there is a management target article 405 at the position of the other three RF tags 404. Note that the RFID reader 403 is connected to a computer or functions as a part of the computer, and the computer determines whether or not the management target article 405 is present.

  Here, the signal intensity of the response signal changes as described above because the managed object 405 and the tag antenna of the RF tag 404 are electromagnetically coupled. Therefore, in the following, the positional relationship among the management target article 405, the RF tag 404, and the conductive layer 5 will be described in more detail.

  FIG. 10 is a top view schematically showing the configuration of the article management system 4000 according to the fourth embodiment. In FIG. 10, the figure which expanded the area | region where one management object article 405 is placed was shown. As shown in FIG. 10, in the article management system 4000, the RF tag 404 is installed above the conductive layer 5. Furthermore, a management target article arrangement area 410 is set in which a management target article is placed at a position above the RF tag 404 and covered with the RF tag 404. The RF tag 404 includes an RFID chip 411 and a tag antenna 412.

  FIG. 11 is a front view of the article management system 4000 according to the fourth embodiment. In FIG. 11, as in FIG. 10, an enlarged view of a region where one managed object 405 is placed is shown. As shown in FIG. 11, one end of the conductive layer 5 and the conductive layer 1 are connected via a matching termination resistor Rt. An RFID reader 403 is connected to the other end of the conductive layer 5. On the connection side of the RFID reader 403, the conductive layer 1 is installed. With this connection, the conductive layer 5 is terminated with matching.

  Further, as illustrated in FIG. 11, the management target article 405 is disposed at a position where the distance between the RF tag 404 and the tag antenna 412 is the first distance L1. The tag antenna 412 of the RF tag 404 is disposed at a position where the distance from the conductive layer 5 is the second distance L2. The first distance L1 and the second distance L2 are set to have a relationship of L1 <L2. FIG. 3 shows only the distance relationship between the management target article 405, the tag antenna 412, and the conductive layer 5. However, in order to satisfy the above distance relationship, for example, the RF tag 404 is covered with a plastic plate or the like. In addition, the thickness of the plastic plate can be used. That is, the relationship between the first distance L1 and the second distance L2 can be ensured by incorporating the RF tag 404 in a plastic plate and forming a sheet in which the RF tag is incorporated by the plastic plate. Note that the method of forming a sheet with a plastic plate is one form for securing the relationship between the first distance L1 and the second distance L2, and other methods can be used.

  FIG. 12 is a side view of the article management system 4000 according to the fourth embodiment. In FIG. 12, the figure which expanded the area | region where one management object article 405 is put was shown like FIG. As shown in FIG. 12, in the fourth embodiment, the conductive layer 5 is disposed on a part of the lower portion of the RF tag 404. In the article management system 4000, the RF tag 404 and the management target article 405 are installed so that the relationship between the first distance L1 and the second distance L2 satisfies the condition of L1 <L2 also in a side view.

  Here, with reference to FIGS. 10 to 12 described above, the effect of the relationship between the components of the article management system 4000 will be described in more detail.

  First, as shown in FIG. 10, in the article management system 4000, the management target article 405 is disposed above the tag antenna 412 of the RF tag 404 at a position where the distance is the first distance L1. Further, the conductive layer 5 connected to the RFID reader 403 is disposed below the RF tag 404, and the line-of-sight distance between the conductive layer 5 and the tag antenna 412 is separated by the second distance L2. As described above, in the article management system 4000, the article to be managed 405 is disposed outside the region sandwiched between the conductive layer 5 and the RF tag 404. Therefore, the line of sight between the conductive layer 5 and the RF tag 404 is not blocked by the management target article 405. In the article management system 4000, the distance between the conductive layer 5 and the tag antenna 412 is set as the second distance L2.

  As described above, in the article management system 4000, the first distance L1 between the managed article 405 and the tag antenna 412 and the second distance L2 that is the line-of-sight distance between the tag antenna 412 and the conductive layer 5 are adjusted. To do. In the article management system 4000, the coupling coefficient k2 between the managed article 405 and the tag antenna 412 and the coupling coefficient between the tag antenna 412 and the conductive layer 5 are adjusted by adjusting the first distance L1 and the second distance L2. Adjust k1. Then, in the article management system 4000, the signal intensity between the tag antenna 412 and the conductive layer 5 is changed according to the coupling coefficient k2 that changes depending on the presence / absence of the article to be managed 405, and the article to be managed 405 is changed by the change in the signal intensity. Determine the presence or absence.

  Therefore, the relationship between the first distance L1, the second distance L2, the coupling coefficients k1, k2, and the effect of the article management system 4000 according to the fourth embodiment based on the setting will be described below. First, in the present invention, electromagnetic coupling is used, but the coupling coefficient indicating the strength of this electromagnetic coupling can be evaluated relatively easily by an electromagnetic simulator. In the description of the electromagnetic field coupling, when the wavelength of the radio signal between the tag antenna 412 and the conductive layer 5 is λ, the distance from the wave source (for example, the antenna) is λ / 2π (π is the circumference). The near region is reactive near-field, the distance is longer than λ / 2π, and the region closer to λ is the radiative near-field, and these two regions are combined to produce the near field ( near-field region).

In this near field, the electromagnetic field has a complex aspect, and there exists a non-negligible intensity ratio between the quasi-electrostatic magnetic field, the induction electromagnetic field, and the radiated electromagnetic field, and the resultant electromagnetic field vector is also spatial. , Changes in time variously. As an example, when the wave source is a minute dipole antenna, the electric field E [V / m] and the magnetic field H [A / m] formed by this antenna are shown in a spherical coordinate system (γ, θ, φ) and a phasor display. It can show by Formula (1)-Formula (4).

Here, in the above formulas (1) to (4), the charge stored in the minute dipole antenna is q [C], the length of the antenna is l [m], the wavelength is λ [m], and from the wave source to the observation point Was set to γ [m]. Further, π is a circular constant, ε is a dielectric constant, and μ is a magnetic permeability. In the equations (1) to (4), a term proportional to 1 / γ ³ is a quasi-electrostatic magnetic field, a term proportional to 1 / γ ² is an induction electromagnetic field, and a term proportional to 1 / γ is radiated. The electromagnetic field is shown. Since these electromagnetic field components have different dependencies on the distance γ, the relative strength changes depending on the distance γ.

Subsequently, shows a table shown in FIG. 13 quasi-electrostatic field in an electric field E _theta, induced electric field, the dependence on the distance γ normalized by the wavelength λ for the relative intensity of the radiation field. The second row of the table shown in FIG. 13 shows the distance converted with a free space wavelength of 950 MHz which is substantially the same as the frequency of UHF (Ultra High Frequency) band RFID permitted by the domestic radio law.

  As can be seen from the table shown in FIG. 13, as the distance γ increases, each electric field strength decreases, and each component ratio also changes. For example, in the region of γ <λ / 2π, the electric field strength increases in the order of quasi-electrostatic field, induction field, and radiation field, and in the region of γ> λ / 2π, the field strength decreases in order of quasi-electrostatic field, induction field, and radiation field. . Furthermore, the contribution of the quasi-electrostatic field and the induced electric field is extremely small in the region where γ> λ, and only the radiation field component is present in the far field where γ> 2λ. On the other hand, in the region of γ <λ, the contribution of the quasi-electrostatic field and the induced electric field remains sufficiently, and in the reactive near field of γ <λ / 2π, the quasi-electrostatic field and the induced electric field make a large contribution. Further, as seen in the equations (1) to (4), compared to the radiated electric field, the quasi-electrostatic magnetic field and the induction electromagnetic field have a γ direction component and a φ direction component in addition to the θ direction component, It has components in various directions.

  In general, compared to the radiated electromagnetic field radiated from the antenna into space, the quasi-electrostatic field and the induced electromagnetic field that remain in the vicinity of the antenna are dominant in the reactive near field. Strong electromagnetic field strength. In the near field of radiation, in general, the absolute electromagnetic field strength becomes weaker as the distance from the wave source becomes longer. Further, the relative strength of the quasi-electrostatic magnetic field and the induction electromagnetic field is weakened, and the relative strength of the radiated electromagnetic field is increased. As described above, there are quasi-electrostatic magnetic field and induction electromagnetic field in the near field, and these electromagnetic fields cause coupling between the conductive layer 5 and the tag antenna 412 and between the tag antenna 412 and the managed object 405. Create a bond.

  In a passive RFID system using a normal UHF band or microwave band, the distance γ between the conductive layer 5 and the tag antenna 412 satisfies the relationship γ> λ, and a radiated electromagnetic field is used for communication. In order to efficiently generate the radiated electromagnetic field, the conductive layer 5 is a resonant antenna typified by a patch antenna. When such a resonant antenna is used in the near field where γ <λ, the electromagnetic field strength varies greatly depending on the location due to the standing wave in the resonant antenna. For example, the amplitude is the largest near the top of the standing wave, and the amplitude is 0 at the midpoint of the standing wave. Therefore, when the distance γ between the conductive layer 5 using such a resonant antenna and the tag antenna 412 satisfies the relationship γ <λ, the portion near the midpoint of the standing wave in the reader antenna is separated from the reader antenna. The signal cannot be received by the tag antenna, or the received signal strength becomes extremely weak. That is, an insensitive area is created, which hinders use.

  For this reason, in a general article management system using RFID, a reader antenna that is sufficiently smaller than the shelf is installed by sufficiently separating the RFID reader from the shelf on which the article is placed, the management target article 405, and the RF tag. Radio waves are radiated from the area, and there is no choice but to take a wide cover area. Therefore, a large space is required between the RFID reader and the RF tag. Further, depending on the material of the shelf, especially in the case of a shelf made of metal, a multipath phenomenon may occur, and the tag reading may become unstable due to radio wave interference, and the tag information may not be read. Also, if a person or object enters between the reader antenna and the place where the article is placed, the tag cannot be read in the same way as there is an article, and it is falsely detected that there is no article. Produce.

  On the other hand, a coupling circuit can be formed by electromagnetic coupling between antennas through a quasi-electrostatic magnetic field and an induction electromagnetic field that exist in the near field of γ <λ, and more preferably in the reactive near field of γ <λ / 2π. . In this case, a large space is not required between the RFID reader and the RF tag according to the conditions. However, if a resonant antenna is simply used for the conductive layer 5, a dead area is created, which hinders use. In addition, the standing wave antenna is generally about λ in size, and when used in proximity to the tag, the cover area becomes extremely narrow.

  Therefore, in the article management system 4000 according to the fourth embodiment, the conductive layer 5 connected to the RFID reader 403 is matched and terminated so that the conductive layer 5 and the tag antenna 412 of the RF tag 404 are electromagnetically coupled. A tag 404 is arranged. In the article management system 4000, the conductive layer 5 of the RFID reader 403 uses an open transmission line that emits less radio waves, thereby passing through the quasi-electrostatic magnetic field and the induction electromagnetic field generated around the open transmission line. And the tag antenna 412 are electromagnetically coupled to form a coupling circuit. That is, an open transmission line is used as a traveling wave antenna that operates in the near field. With this configuration, a large space is not required between the conductive layer 5 and the RF tag 404. In addition, since the communication between the conductive layer 5 and the tag antenna 412 is performed at a short distance through the coupling circuit, there is no human or the like between the occurrence of the multipath phenomenon and the place where the conductive layer 5 and the managed article 405 are disposed. It is possible to suppress erroneous detection due to a thing entering. Furthermore, since an open transmission line terminated with matching is used as the conductive layer 5, the main component of the electromagnetic wave propagating in the antenna does not generate a standing wave but propagates as a traveling wave to the matching end. Here, strictly speaking, the fact that a standing wave does not occur means that the standing wave is sufficiently small. Usually, the standing wave ratio is 2 or less, preferably 1.2 or less. means.

  When the end of the transmission line is matched with sufficient accuracy, or when the electromagnetic wave propagating in the transmission line is sufficiently attenuated near the end of the transmission line, a traveling wave is generated without generating a large standing wave in the transmission line. Becomes the main component. A traveling wave antenna can be formed by utilizing the electromagnetic field distribution in such a transmission line. Further, the electromagnetic field formed in the space around the line has a relatively small radiated electromagnetic field, and an electrostatic magnetic field and an induction electromagnetic field are main components. The electromagnetic field intensity of the electrostatic magnetic field and the induction electromagnetic field is stronger than the intensity of the radiated electromagnetic field, and the electromagnetic field intensity with which the RF tag 404 can be obtained is strong even when the reader is operating with the same output. In other words, it is possible to form an environment in which the radiation electromagnetic field is not scattered around while guaranteeing the operation of the tag.

  In a standing wave type antenna such as a patch antenna that is normally used, the electromagnetic field distribution in the vicinity of the antenna is extremely non-uniform according to the standing wave inside the antenna. The area where 405 can be managed is limited. On the other hand, in the case of a traveling wave antenna composed of an open transmission line described in the present embodiment, there is no portion that does not change like a node in the electromagnetic field distribution even in the vicinity of the antenna, and it always changes everywhere. Accordingly, since there is no electromagnetic field non-uniformity associated with the standing wave along the antenna even in the near field, there is no area where the tag information of the RF tag 404 cannot be read. That is, the degree of freedom of arrangement of the conductive layer 5 and the tag antenna 412 is improved.

  Further, in the article management system 4000, since this traveling wave is used as a signal to communicate through electromagnetic coupling between the conductive layer 5 and the tag antenna 412, unlike the resonant antenna, there is no insensitive area, which hinders use. It does not occur. Accordingly, the article management system 4000 extends the transmission line regardless of the wavelength within a range in which the strength of the quasi-electrostatic magnetic field and the induction electromagnetic field generated around the open transmission line is sufficiently large to operate the RF tag 404. A large cover area can be taken. That is, in the article management system 4000 according to the fourth embodiment, by using the above-described open transmission line, the radiation loss of power is suppressed and the cover area can be easily expanded.

  The open transmission line here is basically a transmission line for the purpose of transmitting electromagnetic waves in the longitudinal direction of the line while suppressing radiation, and indicates an open type. Examples include balanced two-wire transmission lines and similar transmission lines, transmission lines such as microstrip lines, coplanar lines, and slot lines, and grounded coplanar lines and triplate lines that are modifications of these transmission lines. In addition, an antenna that spreads in a plane that transmits signals by changing the electromagnetic field in the gap region sandwiched between the mesh-like conductor portion and the sheet-like conductor portion and the leaching region on the outer side of the mesh-like conductor portion depends on the conditions. It is possible to use. This planar antenna has a standing wave mixed therein and operates as a traveling wave antenna although it is incomplete, and can be used if the non-uniformity of the electromagnetic field distribution caused by the standing wave can be ignored. On the other hand, a shielded transmission line that does not generate such an electromagnetic field around the transmission line such as a coaxial cable or a waveguide that shields the periphery of the transmission line cannot be used.

  In addition, an electromagnetic field exists in a region between the opposing conductive sheet bodies, and the electromagnetic field is changed by changing the voltage between the two conductive sheet bodies. There is an electromagnetic wave transmission sheet that changes the voltage between them to advance the electromagnetic field in a desired direction. In a broader sense, this electromagnetic wave transmission sheet may be regarded as a kind of the open transmission line of the present invention when viewed in the longitudinal direction of the sheet. However, the electromagnetic wave transmission sheet fluctuates in the transmission coefficient due to the standing wave in the sheet, so that the standing wave is considerably large and is not necessarily optimal for the implementation of the present invention. In the case of the electromagnetic wave transmission sheet, the upper surface of the waveguide becomes a metal mesh sufficiently finer than the wavelength, and the evanescent wave can be regarded as leaking from the upper surface. Such a transmission line having a plurality of slots in which electromagnetic fields leak at intervals, widths, and lengths generally less than 1/10 of the wavelength is an open transmission line of the article management system 4000 according to the fourth embodiment. Can be regarded as a kind of

  On the other hand, so-called crankline antennas and meander lines are designed to obtain a constant radiated electromagnetic field strength by designing the crank shape with the intention of radiating from an open transmission line or by actively using higher-order modes. The traveling wave antenna for electromagnetic radiation in the far field using an antenna, a leaky coaxial cable, etc. is different from the open transmission line of the article management system 4000 according to the first embodiment. These are preferentially radiated from a crank shape or slot periodically provided with a size of about the wavelength, generally 1/10 or more of the wavelength. The intensity varies greatly depending on the location. Therefore, when using in the near field, the reading of tag information may become unstable, or the tag may not be read depending on the location. Furthermore, in the UHF band RFID system, the allocated frequency is different in each country in the world, and is distributed in a band of approximately 860 to 960 MHz. This has a wide range of about 10% as a specific band, and requires a significant change in the design of the resonance point of the resonance antenna and the cycle of the crank, meander, and slot. On the other hand, in the article management system 4000 according to the fourth embodiment, since an open transmission line having an extremely wide band is originally used, the same antenna can be used as the conductive layer 5 without any particular change.

  Further, according to the article management system 4000 according to the fourth embodiment, the managed object 405 is placed apart from the RF tag 404 so that the managed object 405 and the tag antenna 412 of the RF tag 404 are electromagnetically coupled. A management target article arrangement area 410 is provided. Accordingly, when the management target article 405 is present, the management target article 405 and the tag antenna 412 form a coupling circuit, so that the resonance frequency of the tag antenna 412 changes compared to the case where the management target article 405 is not present, The feed point impedance of the antenna 412 changes. Since the tag antenna 412 resonates at the frequency of the signal used for communication in free space, the feed point impedance is adjusted, and the reception sensitivity is maximized, the above change lowers the reception sensitivity. Furthermore, the operation of the tag antenna 412 when sending a reflected signal to the RFID reader 403 is also adversely affected. As a result, the power reception sensitivity with respect to the signal used for communication falls. Further, the transmission output of the signal reflected by the RF tag 404 is also reduced. Therefore, the RF tag 404 cannot receive a signal from the RFID reader 403, or the signal receiving strength is low, and the tag cannot have enough operating power, or the tag cannot generate a reflected electromagnetic field with sufficient strength. As a result, the RFID reader 403 cannot read the tag information of the RF tag 404. Alternatively, the intensity and phase of the reflected electromagnetic field that reaches the RFID reader 403 changes greatly with changes in the resonance frequency of the tag. That is, when the management target article 405 is in the management target article placement area 410, the tag information cannot be read, or the intensity or phase of the reflected electromagnetic field from the RF tag 404 is lower than when there is no management target article 405. Since it changes greatly, the RFID reader 403 can detect that there is an article to be managed 405. That is, as a result of the change in the operational characteristics of the tag antenna 412 due to the presence / absence of the management target article 405, the RFID reader 403 can detect the intensity and phase change of the reflected signal from the RF tag 404, and the management result is detected from the detection result. The presence or absence of the target article can be detected.

  As described above, in the article management system 4000 according to the fourth embodiment, it is not always necessary for the management target article 405 to block the prospects of the RF tag 404 and the RFID reader 403 in order to detect the presence or absence of the management target article 405. Since it is only necessary to provide a place where the article to be managed 405 is placed apart from the tag antenna 412 (or the RF tag 404) so that the tag 405 is electromagnetically coupled to the tag antenna 412, the arrangement of the article to be managed is not necessarily RFID. The arrangement is not limited between the reader 403 and the RF tag 404, and a free arrangement is possible.

  Further, the article management system 4000 according to the fourth embodiment does not look at the fact that the article is arranged in the vicinity of the tag antenna 412 that is simply supplied with power from the change in the operating characteristics of the antenna, but the operation of the tag antenna 412. A change in characteristics is determined based on whether or not the tag information read result of the RFID reader 403 is acceptable. Thereby, since the freedom degree of the relative position of the conductive layer 5 and the RF tag 404 can be set high, the freedom of the relative position of the place which arrange | positions the conductive layer 5 and the management target article 405 by interposing the RF tag 404. The degree can be improved. Further, the electromagnetic field formed at the place where the tag antenna 412 places the management target article 405 includes a quasi-electrostatic magnetic field and an induction electromagnetic field component in addition to the radiated electromagnetic field. Therefore, the electromagnetic field component spreads in various directions as compared with a normal far-field radiation electromagnetic field component. Therefore, the article management system 4000 according to the fourth embodiment can improve the degree of freedom of the relative position between the article to be managed and the tag.

  Further, the article management system 4000 according to the fourth embodiment is based on an RFID system, and the RF tag 404 has a unique ID (tag information), and multiple access is possible based on the tag information. Therefore, if the tag information of the RF tag 404 and the location where the management target article 405 is arranged are linked, the location of the management target article 405 can be specified from the tag information of the RF tag 404 that cannot be read. On the other hand, when there is no management target article 405, the RF tag 404 responds to a signal from the RFID reader 403, and the RFID reader 403 can read the tag information of the RF tag 404. Therefore, when there is no management target article 405, the tag information of the RF tag 404 can be read with the intensity of the normal reflected electromagnetic field, so that it can be detected that there is no management target article 405. Further, the location where the management target article 405 is not present can be identified from the tag information of the read RF tag 404. Also, when managing a plurality of management target articles 405, the tag information attached to the location where the management target article 405 is arranged is different, so that the location can be specified and the article management can be performed. Since the presence / absence of the management target article 405 can be detected as described above, the article management system 4000 according to the fourth embodiment can manage the presence / absence of the management target article 405 without having to attach the RF tag 404 to the management article.

  In the article management system 4000 according to the fourth embodiment, a place for placing the management target article 405 is provided so as to be separated from the RF tag 404 so that the management target article 405 is electromagnetically coupled to the tag antenna 412 of the RF tag 404. Since the RF tag 404 is not attached to the management target article 405 and the RF tag 404 can be used repeatedly, the tag cost per article is substantially divided by the number of times the tag is used. . That is, it goes without saying that the problem of the high cost of the RF tag 404 can be solved by repeating a sufficient number of times of use.

  Further, in the article management system 4000 according to the fourth embodiment, since the RF tag 404 is not attached to the management target article 405, privacy infringement or information caused by illegally reading the RF tag 404 attached to the management target article 405. Does not cause security problems. That is, the article management system 4000 according to the fourth embodiment does not cause a problem of illegal reading of tag information by a third party.

  In addition, the article management system 4000 according to the fourth embodiment has a first wavelength between the management target article 405 and the tag antenna 412 when the wavelength of a signal used for communication between the RFID reader 403 and the RF tag 404 is λ. A management target article arrangement area 410 is provided in which the management target articles 405 are placed so that the distance L1 satisfies the relationship L1 ≦ λ. In the article management system 4000 according to the fourth embodiment, the second distance L2 that is the line-of-sight distance between the conductive layer 5 of the RFID reader 403 and the tag antenna 412 of the RF tag 404 satisfies the relationship of L2 ≦ λ. . Note that the distance in the article management system 4000 according to the fourth embodiment is a distance in radio wave propagation, and substantially coincides with the shortest geometric distance.

  If the distance L1 between the management object placement area 410 where the management target article 405 is placed and the tag antenna 412 of the RF tag 404 satisfies the relationship of L1 ≦ λ, the place where the article is placed when viewed from the RF tag 404 Is in the range of the near field. Therefore, the contribution of the quasi-electrostatic field and the induction electric field is sufficient, and the managed article 405 includes a material having a high dielectric constant such as moisture or a metal, and the managed article 405 is placed in the managed article placement area 410. If there is, the tag antenna 412 and the management object 405 can be electromagnetically coupled through a quasi-electrostatic magnetic field or an induction electromagnetic field. Since the human body also contains a large amount of moisture as the management target article 405, it can be detected and used for human flow line management.

  By setting the first distance L1 to a value satisfying L1 ≦ λ, the components of the quasi-electrostatic magnetic field and the induction electromagnetic field are present in the near field of the tag antenna 412 with non-negligible intensities. The component generates electromagnetic field coupling between the tag antenna 412 and the management target article 405 through mutual inductance, capacitance, or the like. Therefore, the circuit constant of the tag antenna 412 changes depending on the presence / absence of the management target article 405, and the operation characteristics of the tag antenna 412 change. Further, as a more easily understandable change depending on the presence / absence of the management target article 405, the resonance frequency of the tag antenna 412 changes. If a commercially available RF tag is used as the RF tag 404 for system cost reduction, the tag antenna 412 is a standing wave antenna based on a dipole antenna. In such an RF tag 404, high sensitivity is realized by setting the resonance frequency of the tag antenna 412 according to the frequency of wireless communication. Thus, the state in which the resonance frequency of the tag antenna 412 resonates at the set frequency corresponds to the state in which there is no managed object 405.

  Next, when the management target article 405 is placed on the RF tag 404, the tag antenna 412 is coupled to the management target article 405, so that the resonance frequency generally decreases. Therefore, the sensitivity of the tag antenna 412 at the radio communication frequency is greatly reduced. For example, when the operating power of the RFID chip 411 cannot be provided due to a decrease in reception sensitivity, the RF tag 404 does not respond to an inquiry from the RFID reader 403. Alternatively, even when operating power is covered, the tag antenna 412 cannot cause a change in electromagnetic field in a sufficiently strong space due to the modulation signal generated by the RFID chip 411.

  As a result, the RF tag 404 does not respond to the inquiry from the RFID reader 403 when the management target article 405 exists, or the reflected electromagnetic field from the RF tag 404 does not respond to the case where the management target article 405 does not exist. The intensity changes greatly. By detecting the change in the intensity of the reflected electromagnetic field by the RFID reader 403, it can be determined that there is no managed object 405. This determination process can be performed by, for example, a computer. As described above, the article management system 4000 according to the fourth embodiment detects the presence / absence of the management target article 405 and manages the presence / absence of the management target article 405 without attaching the RF tag 404 to the management target article 405. be able to.

  Further, in the article management system 4000 according to the fourth embodiment, in order to change the response of the RF tag 404 depending on the presence / absence of the management target article 405, the first distance between the RF tag 404 and the management target article 405 is used. L1 only needs to satisfy the relationship of L1 ≦ λ, and the prospect of the RF tag 404 and the conductive layer 5 does not need to be blocked by the management target article 405. That is, the arrangement of the management target article 405 is not limited between the tag antenna 412 and the RF tag 404 of the RFID reader 403, and the degree of freedom of arrangement is improved. For example, when detecting the presence / absence of a product on a product display shelf, the conductive layer 5 and the RF tag 404 can be incorporated into the shelf board, and the antenna is hidden, so that the appearance is extremely excellent.

  Although a method for detecting a change in signal strength mainly due to the resonance frequency of the tag antenna 412 deviating from the wireless communication frequency has been described here, the present invention is not limited to this. If the resonance frequency is shifted, the presence / absence of the article may be detected by sweeping the wireless communication frequency within a range legally permitted by the reader and detecting the deviation of the resonance frequency. Also, the phase changes greatly before and after the resonance frequency. Therefore, it goes without saying that the presence / absence of an article can also be detected by observing the phase change.

  Similarly to the first distance L1, if the line-of-sight distance L2 between the tag antenna 412 and the conductive layer 5 satisfies the relationship L2 ≦ λ, the conductive layer 5 and the tag antenna 412 are within the range of the near field. Be inside. Here, the line-of-sight distance l2L2 means the distance between the strip conductor that becomes a particularly strong wave source in the conductive layer 5 and the tag antenna 412. By setting the line-of-sight distance L2 to be λ or less, the contribution of the quasi-electrostatic field and the induction field is sufficient, and the conductive layer 5 and the tag antenna 412 can be electromagnetically coupled. In particular, in the article management system 4000 according to the first embodiment, since the presence / absence of an article is determined based on an analog quantity, that is, the intensity of the reflected electromagnetic field from the RF tag 404, a change in the reflected electromagnetic field intensity due to radio wave interference causes erroneous detection. Cheap. However, with this configuration, in the article management system 4000 according to the first embodiment, the wireless communication between the conductive layer 5 and the tag antenna 412 is centered on the direct wave, and radio wave interference due to the multipath phenomenon hardly occurs. Therefore, erroneous detection can be suppressed. Further, the electromagnetic field formed by each antenna of the RFID reader 403 and the RF tag 404 includes a quasi-electrostatic magnetic field and an induction electromagnetic field component in addition to the radiated electromagnetic field. Therefore, the electromagnetic field component spreads in various directions as compared with the case of only a normal far-field radiation electromagnetic field component. Therefore, in the article management system 4000 according to the first embodiment, the degree of freedom of the relative position between the conductive layer 5 and the RF tag 404 can be improved.

  In the article management system according to the first embodiment, the presence / absence of an article such as the intensity or phase change of the reflected electromagnetic field from the RF tag 404 or the resonance frequency change of the tag antenna 412 is determined. The accompanying radio wave interference leads to false detection. However, according to the article management system 4000 according to the first embodiment, by satisfying the relationship of L2 ≦ λ, the wireless communication between the conductive layer 5 and the tag antenna 412 is centered on the direct wave and reflects the surrounding environment. The radio interference caused by the multipath phenomenon is less likely to occur. Therefore, erroneous detection can be suppressed. In particular, when managing the presence / absence of products on the shelf, the shelf is often made of metal or a metal refrigerated case, but the system can be stably operated even in such an environment.

  Further, in the article management system 4000 according to the first embodiment, by satisfying the relationship of L2 ≦ λ, the line-of-sight distance L2 between the conductive layer 5 and the RF tag 404 is UHF, which is one of the frequencies of the RFID standard. The band is about 0.3 m or less, and the 2.4 GHz band is about 0.12 m or less. In addition, since the distance L1 between the management target article placement region 410 and the RF tag 404 also satisfies the relationship of L1 ≦ λ, in the UHF band, which is also one of the frequencies of the RFID standard, about 0.3 m or less, 2.4 GHz The band is about 0.12 m or less. Therefore, the interval between the conductive layer 5 and the management target article arrangement area 410 is also in this order and becomes narrower. Therefore, by using the article management system 4000 according to the first embodiment, by narrowing the interval between the management target article 405 and the RF tag 404 or the conductive layer 5, an object or person different from the management target article 405 may enter. Can be suppressed and erroneous detection can be suppressed.

  Further, in the article management system 4000 according to the first embodiment, the first distance L1 satisfies the relationship L1 ≦ λ / 2π when the circumference ratio is π. When the managed object 405 affects the frequency characteristics of the tag antenna 412, if the first distance L1 is located within the reactive near field that satisfies the relationship L1 ≦ λ / 2π, L1> λ / The intensity of the electromagnetic field formed by the tag antenna 412 is stronger than in the case of the 2π radiation near field. Furthermore, the contribution of the quasi-electrostatic magnetic field and the induction electromagnetic field that remain in the vicinity of the antenna becomes relatively large, and the contribution of the radiated electromagnetic field becomes small. Therefore, in the article management system 4000 according to the first embodiment, the coupling between the management target article 405 and the tag antenna 412 becomes strong. As a result, the influence of the presence / absence of the management target article 405 on the operation characteristics of the tag antenna 412 increases. Therefore, the article management system 4000 according to the first embodiment also has a large change in the reflected electromagnetic field transmitted from the RF tag 404 to the RFID reader 403, becomes an article management system that is resistant to disturbance and noise, and can suppress erroneous detection.

  In the article management system 4000 according to the first embodiment, the line-of-sight distance L2 satisfies the relationship L2 ≦ λ / 2π. As described above, when the line-of-sight distance L2 satisfies the relationship of L2 ≦ λ / 2π, the article management system 4000 according to the first embodiment is closer to the antenna than the case where the line-of-sight distance L2 is L2> λ / 2π. The contribution of the remaining quasi-electrostatic magnetic field and induction electromagnetic field is relatively large, and the coupling between the conductive layer 5 and the tag antenna 412 is strengthened. Therefore, in the article management system 4000 according to the first embodiment, communication between the RFID reader 403 and the RF tag 404 is also less susceptible to disturbance and noise. Thereby, the article management system 4000 according to the first embodiment can realize an article management system that is less susceptible to disturbance and noise. In addition, since the electromagnetic field components of the quasi-electrostatic magnetic field, the induction electromagnetic field, and the radiated electromagnetic field are mixed with sufficient intensity and the direction of the vector changes with time, the article management system 4000 according to the first embodiment. Can improve the degree of freedom of the relative orientation of the conductive layer 5 and the tag antenna 412.

  Furthermore, in the article management system 4000 according to the first embodiment, the line-of-sight distance between the conductive layer 5 and the RF tag 404 is one of the frequencies of the RFID standard by satisfying the relationship of L2 ≦ λ / 2π. The band is about 0.05 m or less and the 2.4 GHz band is about 0.02 m or less. Therefore, according to the article management system 4000 according to the first embodiment, an article management system that does not require a large space between the conductive layer 5 and the RF tag 404 can be realized. For example, the conductive layer 5, the RF tag 404, and the article to be managed can be stored in the product shelf. In addition, by narrowing the interval, it is possible to further prevent people and objects from entering between them, and to suppress erroneous detection caused by blocking the line of sight.

  On the other hand, in general, when an RF tag is attached to a well-known product on the product shelf for management, the attachment position of the RF tag varies depending on the product to which the tag is attached. Therefore, satisfying the relationship of L2 ≦ λ / 2π described above is not preferable because it restricts the type of product and limits the attachment position of the RF tag. Therefore, when the RF tag is attached to the management target article for management, an antenna using a radiated electromagnetic field that can communicate to the far field is used so that the reader antenna and the RF tag can communicate with each other even if the distance is slightly apart. There is a need. Therefore, it is not suitable for the use of an open transmission line for the purpose of basically suppressing radiation and transmitting electromagnetic waves in the longitudinal direction of the line, and a resonance type antenna or a leaky coaxial cable that is normally used is used. . However, when a reader antenna that generates a radiated electromagnetic field with such high efficiency is used, the intensity of the radiated electromagnetic field is attenuated only by 1 / γ with respect to the distance, so that the reading area is expanded. As a result, troubles in product management occur, such as reading RF tags attached to products on other adjacent shelves.

However, according to the article management system 4000 according to the first embodiment, since the RF tag 404 is not attached to the product, for example, the conductive layer 5 is laid on the bottom of the product shelf, and the coupling coefficient is adjusted on the RF tag 404 to It is easy to arrange 404 so as to satisfy the relationship of L2 ≦ λ / 2π, and to arrange a management target product thereon. Therefore, the article management system 4000 according to the first embodiment can use an open transmission line for the purpose of basically suppressing radiation and transmitting electromagnetic waves in the longitudinal direction of the line. In this way, the conductive layer 5 which suppresses radiation whose intensity is attenuated only at 1 / γ and uses a quasi-electrostatic magnetic field attenuated at 1 / γ ³ or an induced electromagnetic field attenuated at 1 / γ ² as a main electromagnetic field component. By using it, when managing the presence / absence of products on the product shelf, it becomes easy to read the RF tag 404 with one conductive layer 5 and limit the region for product management, and on the other adjacent shelf It is difficult to cause a problem that the RF tag 404 is read. In addition, although the example of merchandise management on the merchandise shelf has been described here, even in the case of managing other shelves and floor-standing items, similarly, the region where the RF tag 404 is read by one conductive layer 5 is limited. Needless to say, it is easy to limit the area for article management.

  In the article management system 4000 according to the first embodiment, the first distance L1 and the second distance L2 satisfy the relationship L2> L1. The strength of electromagnetic coupling varies depending on the structure of the antenna and resonator, and the characteristics of the medium between the antennas, but also greatly depends on the distance. According to the article management system 4000 according to the first embodiment, by setting L2> L1, the coupling coefficient k2 between the management target article placement region 410 where the management target article 405 is placed and the tag antenna 412 is set to the conductive layer. 5 and the tag antenna 412 can be made larger than the coupling coefficient k1. That is, by ensuring the relationship of L2> L1, the change in the reflected wave intensity due to the change in the frequency characteristics of the tag antenna 412 due to the presence or absence of the article becomes larger than the maintenance of the communication between the tag antenna 412 and the conductive layer 5. . That is, the article management system 4000 according to the first embodiment can reliably detect the presence / absence of the management target article 405, and thus can suppress erroneous detection.

In the article management system 4000 according to the first embodiment, the coupling coefficient k1 between the conductive layer 5 and the tag antenna 412 is set to a value of 10 ⁻⁵ or more. The power receiving sensitivity that gives the operation limit of the current UHF band RF tag is approximately −20 dBm. On the other hand, the output of the high output version UHF band RFID reader is 30 dBm. Therefore, if the coupling coefficient k1 is a value of 10 ⁻⁵ or more, power for operating the UHF band RF tag can be supplied.

In the article management system 4000 according to the first embodiment, the coupling coefficient k1 between the conductive layer 5 and the tag antenna 412 is set to a value of 10 ⁻² or less. When the tag antenna 412 is regarded as a dipole resonator, the conductive layer 5 (for example, an open transmission line) and the tag antenna 412 are electromagnetically coupled to each other when the open transmission line and the resonator are coupled. Can be interpreted. Therefore, when the coupling coefficient is too strong, the operation of the open transmission line is greatly affected, and as a result, the operations of the other RF tags 404 are also affected as a coupled resonator system. A situation where a plurality of resonators are coupled in parallel to the open transmission line is considered as a circuit of a band rejection filter. In that case, if the tag antenna of the UHF band RF tag uses copper or aluminum at room temperature, since the no-load Q value is approximately 100 or less, if the coupling coefficient k1 that determines the ratio band is 10 ⁻² or less, Almost no influence on the operation of the open transmission line. Therefore, by setting the coupling coefficient k1 to a value of 10 ⁻² or less, the coupling of the tag antenna 412 can be suppressed from affecting the open transmission line, and the RFID reader 403 coupled in parallel to the open transmission line can be suppressed. The mutual influence between them can also be suppressed.

  In addition, the article management system 4000 according to the first embodiment includes the coupling coefficient k1 between the conductive layer 5 and the tag antenna 412 and the management target article 405 and the tag antenna 412 when the management target article 405 exists in the management target article placement area 410. The coupling coefficient k2 satisfies the relationship k1 <k2. According to the present invention, k1 <k2, that is, the coupling coefficient k2 between the managed article placement region 410 and the tag antenna 412 is made larger than the coupling coefficient k1 between the conductive layer 5 and the tag antenna 412. Thus, the change in the reflected signal intensity due to the change in the frequency characteristics of the tag antenna 412 due to the presence or absence of the article becomes larger than the maintenance of the communication between the conductive layer 5 and the tag antenna 412. That is, in the article management system 4000 according to the first embodiment, the presence / absence of the management target article 405 can be reliably detected, and thus erroneous detection can be suppressed.

  In the first embodiment, the positional relationship among the conductive layer 5, the RF tag 404, and the management target article 405 has been specifically described. However, the relative positions and orientations of these components are the specific examples shown in FIG. Yes it is not limited to.

Embodiment 5
An article management system 5000 according to the fifth embodiment will be described. The article management system 5000 is a modification of the article management system 4000 according to the fourth embodiment, and does not have the spacer 402 and the arrangement of the RFID tag 404 is different. The other configuration of the article management system 5000 is the same as that of the article management system 4000.

  FIG. 14 is a top view schematically showing the configuration of the article management system 5000 according to the fifth embodiment. In FIG. 14, the figure which expanded the area | region where one management object article 405 is placed was shown. As shown in FIG. 14, in the article management system 5000, the RF tag 404 is installed on the side of the conductive layer 5 so as to be separated from the conductive layer 5. Furthermore, a management target article arrangement area 410 is set in which a management target article is placed at a position above the RF tag 404 and covered with the RF tag 404.

  As described above, the RF tag 404 is disposed on the side of the conductive layer 5 so as to be separated from the conductive layer 5, so that the distance between the conductive layer 5 and the RF tag 404 can be kept constant even without the spacer 402 ( For example, it can be kept at L2). As a result, the article management system 5000 can detect the presence / absence of the management target article 405, similarly to the article management system 4000.

Other Embodiments The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention. For example, in the above-described embodiment, the open transmission line provided in the antenna has been described as a microstrip line, but this is merely an example. For example, the conductive layer 5 may be formed as a coplanar line or a slot line without providing the conductive layer 1.

  Moreover, although the example which winds up an antenna so that the base part 3 may face inward was shown in FIG. 4, how to wind up is not restricted to this. That is, you may wind up the antenna concerning the above-mentioned embodiment so that the base part 3 may face the outer side.

  In the resonator 6 of the antenna 200, the position of the open part of the open ring resonator is not limited to the above example, and can be changed as appropriate.

  The arrangement of the spiral coil resonators in the resonator 7 of the antenna 300 is not limited to the above example, and can be changed as appropriate.

  Of course, in addition to the antenna 100, other antennas according to the above-described embodiments including the antennas 200 and 300 can be applied to the article management system according to the fourth and fifth embodiments.

DESCRIPTION OF SYMBOLS 1 Conductive layer 2 Dielectric layer 3 Base part 4, 6, 7 Resonator 5 Conductive layer 31 Slope 32 Top part 33 Bottom part 34 Valley part 100, 200, 300, 400, 500 Antenna 402 Spacer 403 RFID reader 404 RFID tag 405 Management object Article 410 Managed object placement area 411 Chip 412 Tag antenna 4000, 5000 Article management system

Claims (11)

A flexible dielectric layer;
A plurality of pedestals formed on the flexible dielectric layer and spaced apart from each other and arranged in a certain direction;
A conductive layer constituting an open-type transmission line provided on each of the plurality of base parts;
A plurality of resonators provided on each of the plurality of bases and connected to the conductive layer,
The resonators of the adjacent base parts are electromagnetically coupled,
antenna. The width on the top side of the base portion of the gap between the adjacent base portions is equal to or larger than the width of the gap on the flexible dielectric layer side,
The antenna according to claim 1. The platform is
A top surface parallel to the major surface of the flexible dielectric layer;
A side surface inclined with respect to the main surface of the flexible dielectric layer,
The gap between the adjacent base parts is sandwiched between the side surfaces of the adjacent base parts,
The antenna according to claim 2. The resonators between the adjacent base parts are formed on the side surfaces of the adjacent base parts so as to face each other through the gap.
The antenna according to claim 3. The resonator provided on one side surface of one of the base parts is connected to the resonator provided on the other side surface via the conductive layer.
The antenna according to claim 4. The resonator is a parallel coupled transmission line resonator,
The antenna according to any one of claims 1 to 5. The resonator is an open ring resonator;
The antenna according to any one of claims 1 to 5. The resonator is a spiral coil resonator.
The antenna according to any one of claims 1 to 5. A flexible conductive layer formed opposite to the conductive layer across the flexible dielectric layer;
The conductive layer and the flexible conductive layer constitute a microstrip line.
The antenna according to any one of claims 1 to 8. The conductive layer is configured as a coplanar line or a slot line.
The antenna according to any one of claims 1 to 8. A plurality of pedestals are formed on the flexible dielectric layer so as to be spaced apart from each other and aligned in a certain direction,
A conductive layer constituting an open transmission line is formed on each of the plurality of base parts,
A plurality of resonators are formed on each of the plurality of base parts, connected to the conductive layer,
The resonators of the adjacent base parts are electromagnetically coupled,
Antenna manufacturing method.

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