JP5548868B2 - Antenna fabric - Google Patents

Description

  The present invention relates to a fabric that can be used as an antenna for wireless communication.

  In recent years, wireless ID tags such as RFID have been miniaturized, and a system for identifying a wireless ID tag by attaching it to various mobile bodies has been developed. In order to recognize the wireless ID tag, an antenna for transmitting and receiving information to and from the wireless ID tag is required.

  Due to the miniaturization of the wireless ID tag, there are fewer restrictions on the mounting position with respect to the moving body. For example, even when attaching to a human being, the wireless ID tag is attached to an existing object to be worn such as clothes, personal belongings and personal belongings to identify and position the person. Recognition is possible. Therefore, the antenna that transmits and receives to / from the wireless ID tag is also attached to various existing items close to the wireless ID tag when the person moves, so that identification and position recognition can be performed in a natural operation without restricting human movement. It is desired to do.

  In response to such a request, for example, in Patent Document 1, a flexible fabric such as a felt fabric is used as a dielectric substrate, and a ground plate, a microstrip patch, and a power supply body to be attached to the dielectric substrate are formed of a conductive cloth. A strip antenna is described, and it is said that by using such an antenna, it is easy to attach to a non-planar place that is light and flexible and does not easily wrinkle, and can be sewn to clothes or a hat. In Patent Document 2, a metal wire such as a copper wire is coiled, a copper foil or the like is bonded to a synthetic resin film, or a vacuum-deposited metal film is etched to obtain a coiled antenna portion. A wrist mounting antenna configured by being attached to a belt-like body such as the above is described.

  For example, in Patent Document 3, a synthetic fiber made conductive by any one of plating, metal deposition, sputtering, and conductive paint is used as a method for supporting electrical characteristics on a fabric. A stretchable conductive fiber material knitted using a composite yarn that covers a stretchable yarn is described. Further, Patent Document 4 describes a fabric antenna woven using a non-electrically conductive yarn made of polyester fiber or the like as a warp and an electrically conductive yarn made of metal fiber or the like as a weft. Has been. Further, in Patent Document 5, at least part or all of the conductive region and the insulation formed by the arrangement pattern of the conductive portion on the woven fabric constituted by the gold and silver thread having the conductive portion and the silk yarn having the insulating property. An antenna comprising a slot having a characteristic is described.

JP 2003-258539 A JP 2002-352199 A JP 2007-191811 A JP 2008-546209 A JP 2009-044439 A

  As in Patent Document 1 described above, when a conductive cloth serving as an antenna is sewed on a cloth, the entire thickness is thicker than that of a normal cloth, and wrinkles are less likely to occur, but the stretchability is not the same as that of a normal cloth. It becomes. In addition, as in Patent Document 2, when a coiled metal wire is pasted on a fabric or a synthetic resin film on which a coil is formed is pasted, it is inferior to a normal fabric in terms of flexibility and stretchability. Become.

  In Patent Document 3, covering is performed using a synthetic fiber that is made conductive by plating or the like. However, such a fiber having a metal film has a high electric resistance, and is a metal having conductivity by bending or stretching. There is a drawback that the coating is easily broken, which is not preferable as a material for the antenna.

  Moreover, although the metal fiber is used in patent document 4, when a metal fiber is scarcely stretchable and it combines with a synthetic fiber to make a woven fabric, it will be disconnected or bent without following the expansion and contraction of the synthetic fiber. Yes, it is difficult to use as an antenna material.

  In Patent Document 5, a gold-silver thread obtained by vapor-depositing aluminum on a base material made of PET is used as the conductive thread. However, the gold-silver thread has a drawback that it is easily disconnected and has high electrical resistance. When the gold and silver thread is used in a twisted state, there is a problem in that the antenna characteristics are not constant because the conductive part is not uniform in the twisted part when viewed from a predetermined direction.

  Accordingly, an object of the present invention is to provide a fabric for an antenna that is thin and has flexibility and stretchability in the same manner as a normal fabric.

Antenna cloth according to the present invention, the ratio a ground structure composed of a woven fabric having a dielectric constant using 4 below ground yarns in warp and weft was around the ground yarn same core yarn and then covering machining of metal fibers It is made of conductive yarn having a resistance of 5 Ω / m to 15 Ω / m, and is arranged in a part of the warp direction and / or the weft direction of the ground structure and held so as to be in close contact with one side of the ground structure. Features. Further, the ground structure is made of a woven fabric woven by double weaving, and the antenna wire is held tightly on one side of the double woven fabric of the ground texture. . Further, the conductive yarn is characterized in that the metal fiber is covered with a twist number of 3000 or more. Further, the length of the antenna line is set based on the number of yarns held so as to cross the antenna line.

  In the present invention, the antenna wire made of conductive yarn having a resistance of 5 Ω / m to 15 Ω / m is held in close contact with the ground structure made of a fiber material having a relative dielectric constant of 4 or less by having the configuration as described above. Therefore, it can be used as a highly sensitive antenna by using a low-resistance antenna wire for the ground structure of the insulator.

  In addition, since the conductive wire with metal fiber covering the core yarn is used as the antenna wire, the antenna wire is excellent in flexibility and stretchability, and the ground structure is curved in a state of being held in close contact with the ground tissue. Even when it is deformed, it can follow the deformation of the ground structure. And since the metal wire is covered so as to be wound around the core yarn, it has the same mechanical characteristics as the yarn made of synthetic fiber, and even when the antenna wire is curved, it does not break, and The metal fiber does not bend.

  Therefore, the antenna fabric of the present invention has the same flexibility and stretchability as the fabric used for existing textile products such as clothes and curtains. On the other hand, it can follow without impairing the characteristics of the antenna.

  In addition, by using the same thread as the ground yarn of the ground structure as the core thread of the conductive thread, the conductive thread can have the same flexibility and stretchability as the ground thread, and the antenna wire is held in close contact with the ground structure. In this state, both can be deformed in the same way without shifting.

  If the antenna wire is inserted in the warp direction and / or the weft direction of the ground structure and held by the intersecting ground yarn, the antenna line can be securely held in close contact with the ground structure. Further, even if the antenna line is held by a sewing thread that is sewn into the ground structure so as to intersect the antenna line, the antenna line can be securely held in close contact with the ground structure.

  Further, if the conductive yarn is twisted and the metal fiber is covered with a twist number of 3000 or more, the conductive yarn can have substantially the same characteristics as the flexibility and stretchability of the core yarn.

  Also, if the length of the antenna line is set based on the number of yarns that cross and hold the antenna line, the length of the antenna line when determining the antenna characteristics can be set with high accuracy.

It is a schematic plan view regarding the embodiment which concerns on this invention. It is a partially expanded view regarding a conductive yarn. It is a graph which shows the relationship between the twist number of an electrically conductive yarn, and strong elongation. It is a graph which shows the relationship between the twist number of an electrically conductive yarn, and an elasticity modulus. It is a partial enlarged plan view regarding the part A shown in FIG. It is the elements on larger scale regarding the part A in the case of sewing. It is a schematic plan view regarding another embodiment which concerns on this invention. It is a graph which shows the relationship between a resonant frequency and antenna element length. It is a graph which shows the relationship between a return loss and antenna element length. It is a map which shows the measurement result regarding the recognition distance of the fabric for antennas of a Yagi antenna shape. It is a map which shows the measurement result regarding the recognition distance of the fabric for antennas of a loop antenna shape. It is a table | surface which shows the result of having measured the recognition distance in the deformation | transformation state of the fabric for antennas.

  Hereinafter, embodiments according to the present invention will be described in detail. The embodiments described below are preferable specific examples for carrying out the present invention, and thus various technical limitations are made. However, the present invention is particularly limited in the following description. Unless otherwise specified, the present invention is not limited to these forms.

  FIG. 1 is a schematic plan view of an embodiment according to the present invention. In the antenna fabric, the antenna wire 2 is held in close contact with the ground structure 1. The antenna line 2 is set in a dipole antenna shape in which a pair of conductive yarns arranged in a straight line is combined. The adjacent ends of the conductive yarns constituting the antenna line 2 are spaced apart from each other by a predetermined distance, and the frequency characteristics of the antenna are determined based on the distance L between the separated ends. In addition, the conductive yarns are arranged in the orthogonal direction at the opposite ends of the conductive yarns to form connection lines 3 to the external circuit. In this example, one connection line 3 is not connected to the antenna line 2 but is arranged in parallel along it. The position where the connection line 3 and the antenna line 2 are electrically connected is determined by actually measuring the characteristics of the antenna line and searching for the optimum position. In addition, the space | interval L mentioned above is not the actual length of a conductive thread but the linear distance between the edge parts by planar view.

  The ground structure 1 is a fabric made of a fiber material such as a woven fabric, a knitted fabric, or a non-woven fabric. The fiber material is an electrically insulating material having a relative dielectric constant of 4 or less, specifically, PET (polyethylene terephthalate). ), Polyester fiber such as PTT (polytrimethylene terephthalate) or PBT (polybutylene terephthalate), nylon (polyamide fiber), aramid (aromatic polyamide fiber), polyolefin fiber such as polypropylene or polyethylene, synthetic fiber such as acrylic , Chemical fibers such as rayon and acetate, and natural fibers such as cotton, hemp, wool, and silk. Moreover, you may use the composite fiber which mixed multiple types of these fibers.

  The conductive yarn used for the antenna wire 2 is obtained by covering metal fibers such as copper fiber, tin bronze fiber, and stainless fiber around the core yarn. As the core yarn, polyester fiber such as PET (polyethylene terephthalate), PTT (polytrimethylene terephthalate) or PBT (polybutylene terephthalate), nylon (polyamide fiber), aramid (aromatic polyamide fiber), polypropylene or polyethylene, etc. Polyolefin fibers, synthetic fibers such as acrylic, chemical fibers such as rayon and acetate, and yarns such as natural fibers such as cotton, hemp, wool, and silk may be used. From composite fibers in which these fibers are mixed. May be used.

  As the covering process, there are a single covering process and a double covering process. FIG. 2 shows a conductive thread subjected to a double covering process in which metal fibers 2b are wound around the core thread 2a. Yes.

  The electrically conductive yarn desirably has an electrically low resistance, and the electrical resistance is preferably set to 5 Ω / m to 15 Ω / m. When the electric resistance exceeds 15 Ω / m, the sensitivity as an antenna deteriorates.

  As for the mechanical properties of the conductive yarn, when the number of twists of the metal fiber to be covered is 3000 T / m or more, it has almost the same properties as the core yarn. FIG. 3 is a graph showing the strength and elongation of a conductive yarn created by double covering using a yarn (84 dtex / 36f) made of PET as a core yarn and a copper fiber (diameter 50 μm) as a metal fiber, Conductive yarn was prepared by setting the number of twists of the metal fiber to 500 T / m, 1000 T / m, 2000 T / m, 3000 T / m, 3500 T / m, and tensile strength test (JIS L 1013 8.5.1). The test result which performed was shown. As can be seen from the graph shown in FIG. 3, when the number of twists is 3000 T / m or more, it has substantially the same characteristics as the core yarn. FIG. 4 is a graph showing the change in the elastic modulus of the conductive yarn depending on the number of twists based on the test results performed in FIG. As seen from this graph, the twist number is 3000 T / m or more and the elastic modulus is almost the same as that of the core yarn.

  Thus, by using the conductive wire in which the metal fiber is covered in the core yarn as the antenna wire, the antenna wire 2 having flexibility and stretchability can be obtained, and the antenna wire 2 is held in close contact with the ground structure 1. In this case, even if the ground structure 1 is curved or stretched, the antenna wire 2 can follow the deformation of the ground structure 1 without being disconnected or displaced. Therefore, even when attached to existing textile products such as clothes and curtains, wireless communication can be performed without being affected by the characteristics of the antenna.

  FIG. 5 is an enlarged plan view of a portion A in FIG. 1 when the antenna wire 2 is held in close contact with the ground tissue 1 woven by double weaving. The antenna wire 2 is held in close contact with the fabric on the upper surface side of the double woven fabric. Conductive yarns that are antenna wires 2 are arranged between the wefts 3b, and the warp yarns 3a are alternately sandwiched between the upper and lower sides of the conductive yarns and are sandwiched in the same manner as the weft yarns 3b. Therefore, the antenna wire 2 is held tightly to the ground structure 1 and does not fall off. Further, since the conductive yarn has flexibility and stretchability, even if the ground structure 1 is deformed, it can be deformed following the deformation, and troubles such as disconnection do not occur. If the same thread as the weft 3b is used as the core yarn of the conductive yarn, the mechanical characteristics of the conductive yarn can be set almost the same as the warp, and the conductive yarn follows the deformation of the ground texture 1 more smoothly. Is possible.

  In addition, since the warp yarns 3a intersect the conductive yarns at substantially equal intervals, it is possible to set the length of the conductive yarns that are in close contact with each other based on the number of the intersecting warp yarns 3a. Therefore, when weaving the ground structure 1, a predetermined number of warp yarns are inserted as wefts to weave, and after the weaving of the ground structure, the conductive yarn is cut while leaving only the amount retained by the warp, and the antenna wire It can also be used as. By forming the antenna line in this way, the above-described distance L can be set with high accuracy, and the sensitivity of the antenna can be improved.

  In this example, since the ground structure 1 is woven by double weaving, the fabric is disposed on the lower surface of the antenna wire 2, and even when the ground structure 1 is disposed on a conductor, the antenna is provided. The line 2 is prevented from contacting the conductor.

  In the above example, the conductive yarns are arranged in the weft direction. However, the conductive yarns can be arranged and held in the warp direction. Also good.

  FIG. 6 is an enlarged plan view of a portion A in FIG. 1 when the antenna wire 2 is held tightly by the sewing thread 4 on the ground structure 1 woven by plain weaving. In this case, the antenna wire 2 is linearly arranged on the surface of the ground structure 1 and fixed with an adhesive or the like, and sewing threads 4 are alternately sewn on both sides of the antenna wire 2 by a sewing machine such as a sewing machine. The antenna wire 2 is held in close contact with the ground structure 1.

  When the antenna wire 2 is fixed by sewing, a knitted fabric or a non-woven fabric can be used as the ground structure 1 in addition to the woven fabric. Further, since the antenna wire 2 is attached to the ground structure 1 as a retrofit, the antenna wire 2 can be attached by checking whether the distance between the antenna wires 2 is set while measuring the length of the sewn conductive thread. Can be set with high accuracy. In addition, when the sewing interval of the sewing thread 4 can be set at an equal interval, the length of the antenna wire 2 may be set based on the number of times of sewing with respect to the ground structure.

  FIG. 7 is a schematic plan view of another embodiment. The antenna wire 10 is held in close contact with the ground tissue 1 in a loop shape and is set in a loop antenna shape. The antenna line 10 is set in a square shape with one side having a length M in plan view, and a connection line 11 is provided at a predetermined interval on one side. The connection line 11 is connected to an external circuit (not shown), and one connection line 11 is not connected to the antenna line 10 and is arranged in parallel along the connection line 11. The position where the connection line 11 and the antenna line 10 are electrically connected is determined by actually measuring the characteristics of the antenna line and searching for the optimum position.

  The antenna wire 10 can be attached so as to be in close contact with the ground structure 11 as in the example shown in FIG.

  Conductive yarn used for the antenna wire is double covering with a double covering machine (made by Kataoka Engineering Co., Ltd.) using a PET yarn (84 dtex / 36f) as the core yarn and a copper fiber (diameter 50 μm) as the metal fiber. And created. The number of twists was set to 3000 T / m.

  The ground texture was woven by plain weaving using yarn (56 dtex) made of PET as warp and weft.

  A radio wave characteristic test was performed with the antenna wire held in close contact with the ground tissue, and the antenna element length corresponding to the 2.45 GHz band was determined. As a method of closely holding the antenna wire, two pieces each of the one held by the fabric shown in FIG. 5 and the one held by sewing shown in FIG. 6 were prepared and tested. The test results are shown in FIGS. FIG. 8 shows the relationship between the resonance frequency and the antenna element length, and FIG. 9 shows the relationship between the return loss and the antenna element length. From these graphs, it was found that an antenna design of 2.45 GHz can be performed with an antenna element length of 22 mm in the case of woven fabric and 23 mm in the case of sewing.

  In order to evaluate the recognizability of RFID, the recognition area of both types of antennas was measured. This was done by placing graph paper (5 mm square) on the antenna and measuring the recognition area (measured at the center of the RFID tag) while moving the RFID. A 3mm thick felt (100% wool) is installed between the created antenna and graph paper, and the distance between the RFID and the felt is set to 0 mm, 6 mm, and 9 mm, and the recognition area is associated with the change in distance. The change of was measured. The measurement results are shown in FIGS.

  As shown in FIG. 10, the Yagi antenna-shaped antenna fabric has an RFID recognition area of about 50 mm × 40 mm when close, and an RFID recognition area of 30 mm × 15 mm when the distance is set to 9 mm. It becomes the area of. Since the recognition area becomes smaller as the distance increases, it can be seen that the Yagi antenna-shaped antenna fabric has performance suitable for spot recognition.

  As shown in FIG. 11, the antenna fabric in the form of a loop antenna has an RFID recognition area of about 30 mm × 40 mm when close, and an RFID recognition area of 60 mm × 50 mm when the distance is set to 9 mm. When the distance is set to 21 mm, the RFID recognition area is an area of 40 mm × 50 mm. From these measurement results, it can be seen that the antenna fabric having a loop antenna shape has a performance suitable for recognizing a wide area.

  When the created antenna fabric in the form of a loop antenna is installed on the drawer of a document locker in the office, the handle of the door, and the glass of the door, it was tested whether RFID can be recognized. It was found to be recognizable. When a Yagi antenna was installed in the same manner and an RFID was recognized, a comparative experiment was conducted. As a result, it was found that the antenna fabric of the present invention can be recognized in the same manner as the Yagi antenna.

  Assuming the case where the created antenna fabric is mounted in various parts of the body, the antenna characteristics were evaluated when the fabric was bent and stretched.

  Regarding the curved state of the fabric, when the curvature of the body part of an adult male was measured with a bending sensor (manufactured by Asakusa Giken), the curvature (1 / cm) was 1 / 5.8 for the palm and 1/5 for the arm and the second arm. It was 1/6 in the thigh and calf. Therefore, the fabric was bent with reference to these curvature data. The extensibility of the fabric for antenna was set to 2% (vertical direction and transverse direction), which is the extensibility required for fabrics used in ordinary clothes. The antenna characteristics were evaluated by measuring the recognition distance of the RFID tag at the center of the antenna. The evaluation results are shown in FIG. For comparison, the antenna fabric was also measured in a normal state with a flat surface.

  As shown in FIG. 12, it was found that the Yagi antenna-shaped antenna fabric does not deteriorate the RFID recognition characteristics even when it is given a curvature comparable to that of the body. Further, it was found that when the antenna fabric is stretched, the RFID recognition distance is reduced by 20% to 50%.

1 Ground structure 2 Antenna line 3 Connection line 4 Sewing thread
10 Antenna wire
11 Connection line

Claims (4)

The ratio a ground structure having a dielectric constant is more than 4 ground yarn from the fabric, which is used in the warp and weft, resistance to around the same core thread and the ground yarn and covering machining of metal fibers 5Ω / m~15Ω / m And an antenna wire that is disposed in a part of the warp direction and / or the weft direction of the ground structure and is held in close contact with one side of the ground structure. Antenna fabric. The ground structure is made of a woven fabric woven by double weaving, and the antenna wire is held tightly on one side of the double woven fabric of the ground texture. The antenna fabric according to 1. The antenna fabric according to claim 1 or 2, wherein the conductive yarn covers the metal fiber with a twist number of 3000 or more. 4. The antenna fabric according to claim 1, wherein a length of the antenna line is set based on a number of yarns held so as to cross the antenna line. 5.

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