Antenna pattern and antenna sheet

Abstract

To provide an antenna pattern for a wireless communication relay capable of covering a plurality of bandwidths (channels) in a frequency band of a radio wave to be received and performing a stable wireless communication without a power supply by a simple method even in the presence of obstacles that interfere with communication and to provide an antenna sheet including the same.SOLUTION: An antenna pattern composed of a conductive wire includes at least one pair of line-symmetrical antenna elements formed by arranging the conductive wires in a folded arrangement. The antenna elements each include a first straight part of a length a, a second straight part of a length b provided parallel to the first straight part, and a folded part of a length c connecting the first straight part and the second straight part. The length a of the first straight part differs from the length b of the second straight part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antenna pattern and an antenna sheet, and more particularly to an antenna pattern and an antenna sheet for wireless communication, which are antenna patterns and antenna sheets for wireless communication relay that can extend communication distances without a power source even when there are obstacles that block or attenuate radio waves, and an antenna sheet including such an antenna pattern. [Background technology]

[0002] In modern society, mobile communication systems using wireless communication such as mobile phones, smartphones, and mobile notebook computers have become an indispensable technology.

[0003] Wireless communication always requires an antenna to receive radio waves. Generally, when connecting a PC or smartphone to the Internet, it is connected to the Internet line via a modem or router that acts as a repeater. When using a wireless LAN router (Wi-Fi router) to wirelessly connect devices such as PCs and smartphones located in different locations to the Internet, there is no need to connect the parent wireless LAN router and the child wireless LAN devices, such as PCs, with a cable. This is aesthetically pleasing and convenient, but when used indoors, for example at home, the materials that make up the doors, walls, and ceilings can block or attenuate radio waves, resulting in insufficient communication. In such cases, installing a repeater or relay antenna can extend the communication distance and enable communication in blind spots where radio waves cannot reach.

[0004] For example, Patent Document 1 describes an indoor relay planar antenna including a first planar antenna installed on a first wall surface indoors, a second planar antenna installed on a second wall surface indoors or outdoors, and a high-frequency transmission cable connecting the first and second planar antennas, the high-frequency transmission cable being disposed in a non-residential space and not visible from inside the room.The document describes that by connecting the first and second planar antennas with a high-frequency transmission cable that passes through the non-residential space, a wireless signal received by one planar antenna can be transmitted to the other planar antenna while suppressing attenuation of the electric field strength. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-096607 Summary of the Invention [Problem to be solved by the invention]

[0006] In order for wireless LAN devices to send and receive data, they need to use channels with the same bandwidth. However, because wireless LAN uses radio waves, depending on the environment and frequency band used, problems such as communication interruptions due to radio wave interference can occur. Therefore, to prevent radio wave interference, it may be necessary to set nearby access points to use different channels.

[0007] Furthermore, from the viewpoint of antenna installation costs and ease of maintenance, it is preferable that the antenna has as simple a structure as possible and can function without a power source.

[0008] The present invention was completed in consideration of the above-mentioned problems, and in one embodiment, its objective is to provide an antenna pattern for wireless communication relay that can cover multiple bandwidths (channels) in the frequency band of the radio waves to be received and that can perform stable wireless communication without a power source in a simple manner, even in the presence of obstacles that cause communication interference, and an antenna sheet equipped with such an antenna pattern. [Means for solving the problem]

[0009] After extensive research, the inventors have found that the above-mentioned problems can be solved by controlling the length of the straight line portion of the antenna element of the antenna pattern. More specifically, by configuring the parallel first and second straight line portions of the antenna element to have different lengths, it is possible to cover multiple bandwidths (channels) in the frequency band of the received radio waves, and to perform stable wireless communication without a power source in a simple manner. The present invention was completed based on the above findings, and is exemplified below.

[0010] In one aspect, the present invention provides an antenna pattern made of a conductive line, the antenna pattern including at least one pair of line-symmetric antenna elements formed by folding back the conductive line, The antenna element comprises a first straight portion having a length a, a second straight portion having a length b that is parallel to the first straight portion, and a folded portion having a length c that connects the first straight portion and the second straight portion, and the length a of the first straight portion is different from the length b of the second straight portion. This is the antenna pattern.

[0011] In one embodiment of the present invention, one of the length a+c obtained by adding the length a of the first straight portion and the length c of the turned-back portion, and the length b+c obtained by adding the length b of the second straight portion and the length c of the turned-back portion, can be configured to correspond to 1 / 4λ of the maximum reception frequency in the frequency band of the radio waves to be received, and the other can be configured to correspond to 1 / 4λ of the minimum reception frequency in the frequency band of the radio waves to be received.

[0012] In one embodiment of the present invention, a plurality of pairs of antenna elements may be provided via a feeder line.

[0013] In one embodiment of the present invention, the pair of antenna elements at the most distal ends of the antenna pattern are connected as a single conductive line, thereby providing the antenna pattern as a whole as a single continuous linear conductive pattern.

[0014] In another aspect, the present invention provides an antenna sheet including a sheet-like substrate and an antenna circuit pattern formed of a conductive pattern by folding back a conductive line on one side of the sheet-like substrate, the antenna circuit pattern includes a first antenna portion, a second antenna portion provided apart from the first antenna portion, and a transmission line portion connecting the first antenna portion and the second antenna portion; The first antenna unit and the second antenna unit each include at least one pair of axisymmetric antenna elements, and the antenna elements each include a first straight portion with a length a, a second straight portion with a length b that is parallel to the first straight portion, and a folded portion with a length c that connects the first straight portion and the second straight portion, and the length a of the first straight portion is different from the length b of the second straight portion. It is an antenna sheet.

[0015] In one embodiment of the present invention, in both the first antenna unit and the second antenna unit, one of the length a+c obtained by adding the length a of the first straight portion and the length c of the folded portion, and the length b+c obtained by adding the length b of the second straight portion and the length c of the folded portion, can be configured to correspond to 1 / 4λ of the maximum reception frequency in the frequency band of the radio waves to be received, and the other can be configured to correspond to 1 / 4λ of the minimum reception frequency in the frequency band of the radio waves to be received.

[0016] In one embodiment of the present invention, at least one of the first antenna unit and the second antenna unit may include a plurality of pairs of antenna elements connected via a feeder line.

[0017] In one embodiment of the present invention, in at least one of the first antenna unit and the second antenna unit, a pair of the most distal antenna elements can be connected as a single conductive line, and the first antenna unit, the second antenna unit, and the transmission line unit can be provided as a single continuous linear conductive pattern as a whole.

[0018] In one embodiment of the present invention, the transmission line section may be a parallel transmission line in which two conductive lines are arranged in parallel.

[0019] In one embodiment of the present invention, the antenna sheet may further include a protective layer for protecting at least a portion of the antenna circuit pattern.

[0020] In one embodiment of the present invention, the antenna sheet may further include an adhesive layer provided on at least one surface of the sheet-like substrate. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide an antenna pattern for wireless communication relay that can cover multiple bandwidths (channels) in the frequency band of the radio waves to be received and that can perform stable wireless communication without a power source in a simple manner even when there are obstacles that cause communication interference, and an antenna sheet equipped with such an antenna pattern. [Brief explanation of the drawings]

[0022] [Figure 1] Fig. 1(A) is a plan view schematically showing an example of a pair of antenna elements of an antenna pattern of the present invention, and Fig. 1(B) is a plan view schematically showing another example of a pair of antenna elements of an antenna pattern of the present invention. [Figure 2] FIG. 2 is a plan view schematically showing an example of an antenna pattern in which a plurality of pairs of antenna elements are provided. [Figure 3]Fig. 3(A) is a plan view schematically showing an example of the antenna sheet of the present invention. Fig. 3(B) is a cross-sectional view schematically showing an example in which an adhesive layer is provided on the antenna sheet. Fig. 3(c) is a cross-sectional view schematically showing an example in which a protective layer is provided on the antenna sheet. [Figure 4] Fig. 4(A) shows an example of the antenna sheet of the present invention in which the conductive lines of the conductive pattern are embedded in the surface of the sheet-like substrate, and Fig. 4(B) shows an example of the antenna sheet of the present invention in which the conductive lines of the conductive pattern are partially covered by the surface of the sheet-like substrate. [Figure 5] FIG. 5 is a plan view schematically showing an example of an antenna sheet used in a comparative example. [Figure 6] Fig. 6(A) is a schematic diagram showing an example of how the antenna sheet of the present invention is attached, and Fig. 6(B) is a diagram showing the attachment mode of Fig. 6(A) as viewed from above. [Figure 7] FIG. 7 is a schematic diagram showing another example of the manner in which the antenna sheet of the present invention is attached. DETAILED DESCRIPTION OF THE INVENTION

[0023] Next, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and it should be understood that appropriate design changes, improvements, etc. may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. Note that the dimensions, scales, angles, etc. in the drawings illustrating each embodiment of the present invention are shown for convenience to aid understanding, and do not necessarily represent actual dimensions, scales, angles, etc.

[0024] (1. Antenna element) Fig. 1(A) is a plan view schematically showing an example of a pair of antenna elements of an antenna pattern of the present invention. Fig. 1(B) is a plan view schematically showing another example of a pair of antenna elements of an antenna pattern of the present invention. The antenna pattern of this embodiment is characterized by including at least one pair of such antenna elements.

[0025] As shown in FIG. 1, the antenna elements of the antenna pattern of this embodiment are formed by folding back conductive wires and are arranged symmetrically above and below the center line (dotted line) in the drawing. The upper and lower antenna elements each comprise a first straight portion of length a, a second straight portion of length b that is parallel to the first straight portion, and a folded portion of length c that connects the first and second straight portions, with the length a of the first straight portion and the length b of the second straight portion being different. The length a refers to the distance from the center line to the end that connects to the folded portion c in the vertical direction, and the length b refers to the distance from the center line to the end that connects to the folded portion c in the vertical direction. In the pair of antenna elements, it is preferable that the length a of the first straight portion and the length b of the second straight portion are equal.

[0026] By making the length a of the first straight section and the length b of the second straight section different lengths, it is possible to cover multiple bandwidths (channels) in the frequency band of the radio waves to be received, making it easier for nearby access points to receive on different channels.

[0027] In Figure 1(A), to cover multiple bandwidths (channels) in the frequency band of the received radio waves, the combined length a of the first straight section (a) and the folded section (c) (a+c) can be set to a length equivalent to 1 / 4λ of the minimum reception frequency in the frequency band of the received radio waves, and the combined length b of the second straight section (b) and the folded section (c) (b+c) can be set to a length equivalent to 1 / 4λ of the maximum reception frequency in the frequency band of the received radio waves. For example, in the case of IEEE802.11a, the international standard for Wi-Fi, the available frequencies in the 5 GHz band for wireless LANs are the 5.2 GHz band (W52) with a frequency band of 5150 to 5250 MHz (four channels), the 5.3 GHz band (W53) with a frequency band of 5250 to 5350 MHz (four channels), and the 5.6 GHz band (W56) with a frequency band of 5470 to 5725 MHz (eleven channels). To cover all of these bandwidths, it is necessary to cover the frequency band from the minimum reception frequency of 5150 MHz to the maximum reception frequency of 5725 MHz. In this case, the combined length a+c of the first straight section length a and the folded section length c should be approximately 14.5 mm, which corresponds to 1 / 4λ of the minimum receiving frequency of 5150 MHz, and the combined length b+c of the second straight section length b and the folded section length c should be approximately 13 mm, which corresponds to 1 / 4λ of the maximum receiving frequency of 5725 MHz.

[0028] For IEEE802.11b, the 2.4 GHz frequency band is 2401–2495 MHz (center frequency 2412–2484 MHz), with 14 channels available in Japan. Compared to the 5 GHz band, the 2.4 GHz band has longer reach and is more resistant to obstacles like walls, allowing for a relatively wide range of use. However, because the standard limits each channel width to 22 MHz (11 MHz on either side of the center frequency), it is common to allocate three channels (maximum four channels) spaced five channels apart to avoid interference and avoid overlapping frequencies. Even in this case, to cover the entire bandwidth of 2401–2443 MHz (channels 1–5), 2426–2468 MHz (channels 6–10), 2451–2483 MHz (channels 11–13), and 2473–2495 MHz (channel 14), a frequency band from a minimum reception frequency of 2401 MHz to a maximum reception frequency of 2495 MHz is required. In this case, the combined length a+c of the first straight section length a and the folded section length c should be approximately 31 mm, which corresponds to 1 / 4λ of the minimum receiving frequency of 2401 MHz, and the combined length b+c of the second straight section length b and the folded section length c should be approximately 30 mm, which corresponds to 1 / 4λ of the maximum receiving frequency of 2495 MHz.

[0029] Furthermore, according to actual requirements, any minimum reception frequency and any maximum reception frequency in these frequency bands can be arbitrarily selected, and then the length a + c obtained by combining the length a of the first straight portion and the length c of the folded portion, and the length b + c obtained by combining the length b of the second straight portion and the length c of the folded portion can be set. Different embodiments of the present invention shall include any combination of these. Furthermore, in various antenna patterns of the present invention, pairs of different antenna elements can be combined and arranged. For example, in an antenna pattern, for some pairs of antenna elements, the length a + c obtained by combining the length a of the first straight portion and the length c of the folded portion is set to be approximately 14.5 mm corresponding to 1 / 4λ of the minimum reception frequency of 5150 MHz, and the length b + c obtained by combining the length b of the second straight portion and the length c of the folded portion is set to be approximately 13 mm corresponding to 1 / 4λ of the maximum reception frequency of 5725 MHz. For another part of the pairs of antenna elements, the length a + c obtained by combining the length a of the first straight portion and the length c of the folded portion is set to be approximately 31 mm corresponding to 1 / 4λ of the minimum reception frequency of 2401 MHz, and the length b + c obtained by combining the length b of the second straight portion and the length c of the folded portion is set to be approximately 30 mm corresponding to 1 / 4λ of the maximum reception frequency of 2495 MHz.

[0030] In the case of FIG. 1(A), in order to connect the ends of the first straight portion, the folded portion, and the second straight portion to form a single linear shape, it is necessary to make the length b + c obtained by combining the length b of the second straight portion and the folded portion c longer than the length a of the first straight portion (a < b + c). Also, although the length of the folded portion c is arbitrary, the folding rate of the folded portion c with respect to the length a of the first straight portion [c / (a + c)] and the folding rate of the folded portion c with respect to the length b of the second straight portion [c / (b + c)] should be 60% or less, preferably 40% or less. Especially when the folding rate is up to a maximum of 40% for folding, the deterioration of the radiation efficiency can be suppressed to a very small extent, which can contribute to the miniaturization of the antenna.

[0031] In the case of Fig. 1(A), a gap is provided between the second straight line portions b of each pair of vertically symmetrical antenna elements for a feeder line (or a feed point). This gap can be any size, but may be 1 mm to 5 mm, and preferably 1 mm to 3 mm. Also, in Fig. 1(A), the first straight line portions a of each pair of vertically symmetrical antenna elements are connected in a single line, but they may also have a gap therebetween, similar to the second straight line portions b. In this case, the length of the first straight line portion a should be the length from the center line of the pair of vertically symmetrical antenna elements to the end connected to the folded portion c.

[0032] Figure 1(B) shows an antenna pattern in which the combined length a of the first straight section a and the folded section c, a + c, is set to a length equivalent to 1 / 4λ of the maximum reception frequency in the frequency band of the radio waves to be received, and the combined length b of the second straight section b and the folded section c, b + c, is set to a length equivalent to 1 / 4λ of the minimum reception frequency in the frequency band of the radio waves to be received. In Figure 1(B), the trapezoidal linear pattern formed by the first straight section a, the folded section c, and the second straight section b in Figure 1(A) is inverted. Even in this case, as with the antenna pattern in Figure 1(A), it is possible to cover multiple bandwidths (channels) in the frequency band of the radio waves to be received.

[0033] (2. Antenna Pattern) FIG. 2 is a plan view schematically illustrating an example of an antenna pattern having multiple pairs of antenna elements according to the embodiment of the present invention. As shown in FIG. 2, multiple pairs of antenna elements, each formed by a first straight portion a, a folded portion c, and a second straight portion b, are provided via a feeder line. In addition to the pairs of antenna elements according to the embodiment of the present invention, pairs of antenna elements having other shapes may also be arranged in the antenna pattern. However, preferably, all pairs of antenna elements are pairs of antenna elements according to the embodiment of the present invention. When multiple pairs of antenna elements according to the embodiment of the present invention are arranged, it is preferable to arrange them so that their respective first straight portions and second straight portions are all parallel. The total number of pairs of antenna elements may be two or more. However, since an increase in the number increases the dimensions of the antenna sheet, the total number may be 10 or less, preferably 5 or less. Furthermore, the distance d between two adjacent pairs of antenna elements is preferably 2 mm to 20 mm, preferably 3 mm to 10 mm. The total number and distance between pairs of antenna elements offer a high degree of design freedom, allowing for adjustment of directivity and reception sensitivity to some extent.

[0034] When multiple pairs of antenna elements according to the embodiment of the present invention are arranged, the length a of the first straight portion, the length b of the second straight portion, and the length c of the folded portion in one pair of antenna elements may be the same as or different from those in the other pairs of antenna elements. Preferably, the length a of the first straight portion, the length b of the second straight portion, and the length c of the folded portion are configured to be the same in all pairs of antenna elements.

[0035] In Fig. 2, the pair of antenna elements at the forefront of the antenna pattern are spaced apart similarly to the feeder line, but by connecting the pair of antenna elements at the forefront as a single conductive line, the antenna pattern as a whole can be provided as a single continuous linear conductive pattern (see Fig. 3(A)). In the embodiment of Fig. 2, the pair of antenna elements at the forefront of the antenna pattern refers to the pair of antenna elements located at the leftmost position.

[0036] (3. Antenna sheet) Fig. 3(A) is a plan view schematically showing an example of the antenna sheet of the present invention. Fig. 3(B) is a cross-sectional view schematically showing an example in which an adhesive layer is provided on the antenna sheet. Fig. 3(c) is a cross-sectional view schematically showing an example in which a protective layer is provided on the antenna sheet.

[0037] According to Figure 3(A), the antenna sheet 1 includes a sheet-like substrate 2 and an antenna circuit pattern 3 consisting of a conductive pattern formed by folding a conductive wire on one side of the sheet-like substrate 2, and the antenna circuit pattern 3 includes a first antenna portion 31, a second antenna portion 32 disposed apart from the first antenna portion 31, and a transmission line portion 4 connecting the first antenna portion 31 and the second antenna portion 32.

[0038] 1 or 2, each of the first antenna unit 31 and the second antenna unit 32 has an antenna element arranged axisymmetrically, the antenna element being made up of a first straight portion of length a, a second straight portion of length b arranged parallel to the first straight portion, and a folded portion of length c connecting the first straight portion and the second straight portion, and the length a of the first straight portion is different from the length b of the second straight portion. Also, in the embodiment of Fig. 3(A), each of the first antenna unit 31 and the second antenna unit 32 has four pairs of antenna elements formed by the first straight portion, the folded portion, and the second straight portion arranged symmetrically above and below via a feeder line.

[0039] The transmission line section 4 connecting the first antenna section 31 and the second antenna section 32 is a transmission path for transmitting a power signal between the first antenna section 31 and the second antenna section 32, and is composed of two parallel straight lines. There is no particular limit to the length of the transmission line section 4, but it is suitable to have a length of, for example, 5 mm to 500 mm, preferably 10 mm to 100 mm. The parallel spacing is also suitable to have a length of 1 mm to 5 mm, preferably 1.5 mm to 3 mm.

[0040] According to the antenna sheet 1 of this embodiment illustrated in Figure 3(A), radio waves received by the first antenna section 31 can be transmitted from the second antenna section 32, and even if there is an obstacle that interferes with communication, it is possible to provide an antenna sheet 1 for wireless communication relay that can perform stable wireless communication without a power source in a simple manner.

[0041] The sheet-like substrate 2 used in one embodiment of the present invention has a predetermined thickness and is composed of a single layer or multiple layers, and each layer can be made of paper, synthetic paper, a thermoplastic resin sheet, or the like. From the viewpoint of flexibility, if the sheet-like substrate 2 is a single layer, it is preferable that the layer be made of a resin material, and if the sheet-like substrate 2 is composed of multiple layers, it is preferable that at least one layer be made of a resin material. It is desirable to use a thermoplastic resin as the resin material that constitutes at least one layer of the sheet-like substrate 2.

[0042] Examples of thermoplastic resins that can be used include ethylene-based resins, propylene-based resins, polyolefin-based resins, thermoplastic polyester-based resins, polyamide-based resins, polyvinyl chloride, polycarbonate, and ABS resins. These materials may be used alone or in combination of two or more.

[0043] An example of the sheet-like substrate 2 being made up of multiple layers is a paper substrate coated or laminated with a thermoplastic resin.

[0044] When the sheet-like substrate 2 is made of a thermoplastic resin, it is preferable to use a transparent or translucent thermoplastic resin, since this makes it possible to produce an overall transparent or translucent antenna sheet 1. The overall transparent or translucent antenna sheet 1 for wireless communication relay can be attached without impairing the design of the adherend, such as a building to which it is attached.

[0045] The sheet-like substrate 2 may contain inorganic fine powder or organic filler, dispersant, antioxidant, compatibilizer, ultraviolet stabilizer, antiblocking agent, antistatic agent, etc. as appropriate.

[0046] In order to maintain the strength of the sheet-like substrate 2 and to perform the function of supporting the conductive pattern 3, the thickness of the sheet-like substrate 2 is preferably 0.030 mm or more, and more preferably 0.050 mm or more. On the other hand, from the viewpoint of maintaining the flexibility of the sheet-like substrate 2, the thickness of the sheet-like substrate 2 is preferably 1.000 mm or less, and more preferably 0.500 mm or less.

[0047] As described above, the sheet-like substrate 2 may be composed of a single layer or multiple layers (or a combination of layers made of different materials), but it is preferable that the sheet-like substrate 2 as a whole has flexibility or plasticity, because this allows it to be used in a folded state, as shown in Figures 6 and 7 described later.

[0048] The means for arranging the conductive pattern 3 is not limited, but it can be formed by printing using conductive ink such as silver paste, by etching metal foil such as copper foil, or by arranging circular conductive wires with a certain diameter in a cross-sectional view in a predetermined pattern.

[0049] In the printing method, a conductive ink such as silver paste can be used to form a desired antenna circuit pattern as a printed antenna on one side of the sheet-like substrate 2 using a printing method such as screen printing, offset printing, or inkjet printing.

[0050] In the case of formation by etching, a substrate in which copper foil or aluminum foil is bonded to an insulating film is etched to form a desired antenna circuit pattern as an etching antenna. In the case of formation by etching, the insulating film may be used as is as the sheet-like substrate 2, or the sheet-like substrate 2 may be bonded to the surface of the insulating film on which the antenna circuit pattern is formed, so that the antenna circuit pattern is sandwiched between the insulating film and the sheet-like substrate 2.

[0051] When the conductive pattern 3 is formed of conductive wires, the conductive wires include at least metal wires, preferably metal wires coated with a self-adhesive insulating coating. Examples of metal wires that can be used include copper, iron, gold, silver, copper-nickel, nickel-chromium, and iron-nickel-chromium, but other conductive materials can also be used. From the viewpoints of communication characteristics, durability, and cost, copper or a copper alloy is preferred for the metal wire. Examples of copper alloys that can be used include copper alloys made of zinc, lead, tin, silver, aluminum, nickel, beryllium, zirconium, and the like, either singly or in combination.

[0052] The insulating coating covering the metal wire is an insulating resin coating, and the conductive wire covered with the insulating coating can be a commercially available enameled wire. Specific examples of insulating resin coatings include polyester, polyethylene, polyurethane, polyvinyl chloride, polyamide, polyimide, polyesterimide, polyamideimide, and fluororesin. The insulating coating is typically black, but may be colored any color to match the color of the substrate to which it is attached.

[0053] Considering communication characteristics, the diameter of the conductive wires constituting the conductive pattern 3 can be, for example, 0.03 mm to 0.2 mm. Although it may not be easy to form thin conductive wires, it is better for the conductive wires to be as thin as possible so as not to impair the transparency and design of the adherend to which they are attached, and the diameter of the conductive wires is preferably 0.05 mm to 0.15 mm.

[0054] In one preferred embodiment of the present invention, the conductive pattern 3 can be formed by a single continuous conductive line including the first antenna portion 31, the second antenna portion 32, and the transmission line portion 4. FIG. 3(A) shows an example in which the first linear portions of the pair of antenna elements at the forefront of the first antenna portion 31 are connected by a single conductive line, and the first antenna portion 31, the second antenna portion 32, and the transmission line portion 4 are provided as a continuous conductive pattern made up of a single conductive line as a whole. Note that the pair of antenna elements at the forefront of the first antenna portion 31 refers to the pair of antenna elements that are farthest from the transmission line portion 4.

[0055] A typical method for forming such a conductive pattern is to route conductive wires on one surface of the sheet-like substrate 2 to form a predetermined pattern, and then embed and fix the conductive wires in at least one surface of the sheet-like substrate 2. Here, "embedded" means that the portion of the sheet in contact with the conductive wire is positioned higher than the lower end of the conductive wire. For example, as shown in FIG. 4(A), the lower end of the conductive wire may be embedded deeper than the surface of the sheet-like substrate 2. Alternatively, as shown in FIG. 4(B), the lower end of the conductive wire may be at the same height as or higher than the sheet surface, but a portion of the sheet surface may be raised to cover part of the lower end of the conductive wire.

[0056] A desirable method for embedding conductive wires in the surface of the sheet-like substrate 2 is, for example, to use a sheet-like substrate 2 having at least one surface made of a thermoplastic resin, and to embed the conductive wires in the surface of the sheet-like substrate 2 using the principle of ultrasonic fusion. When performing ultrasonic fusion, a wiring drawing device can be used that melts the surface of the sheet-like substrate 2 made of a thermoplastic resin while feeding out the conductive wire, thereby embedding the conductive wire in the surface of the sheet-like substrate 2. The ultrasonic head included in such a wiring drawing device can be used to feed the conductive wire onto the surface of the sheet-like substrate 2, and embed the conductive wire in the surface of the sheet-like substrate 2 by vibration and pressure.

[0057] Embedding the conductive wires in the surface of the sheet-like substrate 2 allows the conductive pattern 3 to be positioned on the sheet-like substrate 2, and prevents the conductive wires from being displaced due to external impact, etc. Furthermore, embedding the conductive wires in the surface of the sheet-like substrate 2 reduces the degree of unevenness on the surface of the sheet-like substrate 2 caused by arranging the conductive wires on the surface of the sheet-like substrate 2.

[0058] (4. Adhesive layer) In one embodiment of the present invention, an adhesive layer can be provided on at least one surface of the sheet-like substrate 2. More specifically, an adhesive layer 5 can be provided on at least one of the surface of the sheet-like substrate 2 on which the conductive pattern 3 is provided and the other surface of the sheet-like substrate 2 on which the conductive pattern 3 is not provided. In Fig. 3(B), an adhesive layer 5 is provided on the other surface of the sheet-like substrate 2 on which the conductive pattern 3 is not provided.

[0059] The adhesive layer is attached to an adherend such as a building or architectural fixture to which the antenna sheet 1 of the present invention is to be attached. For the adhesive layer, for example, an acrylic, urethane, epoxy, rubber, polyester, cellulose, emulsion, or other adhesive can be used. If necessary, fillers, tackifiers, curing agents, and the like can be used as additives to improve the properties of the adhesive.

[0060] The thickness of the adhesive layer 5 is not particularly limited as long as it has sufficient adhesive strength, and is usually 20 μm or more, preferably 25 μm or more. There is no particular upper limit to the thickness of the adhesive layer 5, but it is usually 200 μm or less, preferably 75 μm or less. When forming the adhesive layer 5, the adhesive can be formed using a coating method such as gravure coating, gravure reverse coating, comma coating, knife coating, or die coating.

[0061] (5.Protective layer) In one embodiment of the present invention, a protective layer 6 can be provided to protect at least a portion of the conductive pattern 3. More specifically, a protective layer 6 can be provided on one surface of the sheet-like substrate 2 on which the conductive pattern 3 is provided, to protect at least a portion of the conductive pattern 3. In FIG. 3(C), the conductive pattern 3 is provided on one surface of the sheet-like substrate 2, and the protective layer 6 is provided on the entire surface of the sheet-like substrate 2 on which the conductive pattern 3 is provided, so as to cover the conductive pattern 3.

[0062] The protective layer 6 protects the conductive pattern 3 provided on one side of the sheet-like base material 2 from being exposed to the outside. If the conductive pattern 3 is a conductive wire covered with a self-fusing insulating layer, the protective layer 6 is not necessarily required, but the protective layer 6 can prevent the conductive pattern 3 from peeling off from the sheet-like base material 2 due to friction or from being broken by impact.

[0063] Specific examples of materials for the protective layer 6 include compositions containing, as the main component, one or more of the monomers, prepolymers, oligomers, or polymers that constitute polyvinyl chloride resins, polyvinyl acetate resins, polyacrylic or polymethacrylic resins, polyvinyl alcohol resins, ethylene copolymers, polyvinyl acetal resins, rubber resins, polyester resins, polyamide resins, polyimide resins, polyamideimide resins, polyolefin resins, phenol resins, aminoplast resins, epoxy resins, polyurethane resins, polyesterurethane resins, silicone resins, and cellulose resins.

[0064] The protective layer 6 can be formed by a printing method such as offset printing, gravure printing, or screen printing. Alternatively, a transparent or translucent thermoplastic resin sheet similar to the sheet-like substrate 2 can be laminated by hot pressing, with an adhesive layer interposed between them as needed. When the sheet-like substrate 2 and the protective layer 6 are transparent or translucent, an antenna sheet 1 that is transparent or translucent as a whole can be suitably produced. The antenna sheet 1 that is transparent or translucent as a whole can be attached without impairing the design of the adherend, such as a building to which it is attached.

[0065] When the protective layer 6 is formed by a printing method, the lower limit of the thickness is 1 μm or more, preferably 5 μm or more, and the upper limit is 100 μm or less, preferably 50 μm or less. When a thermoplastic resin sheet is used, the lower limit of the thickness of the protective layer 6 is 10 μm or more, preferably 50 μm or more, and the upper limit is 500 μm or less, preferably 300 μm or less.

[0066] In the present invention, the protective layer 6 can be a concealing layer that visually conceals the conductive pattern 3. The concealing layer may be a colored protective layer 6, or the protective layer 6 itself, or a protective layer 6 with a printed design. As for the design, a decorative layer similar in appearance to the adherend, such as a building or architectural fixture, to which the sheet is to be attached can be used to make the attached wireless communication relay antenna sheet 1 less noticeable. For example, if the adherend, such as a building fixture, has a certain pattern on its surface, the decorative layer may be attached so as to appear continuous with the pattern.

[0067] In the present invention, a second adhesive layer can be further provided on the protective layer 6 on one side of the sheet-like substrate on which the conductive pattern is provided. In this case, however, it is not essential that the protective layer 6 and the second adhesive layer are in contact with each other, and another layer may be provided between them.

[0068] In one use mode of this embodiment, in a member having at least two surfaces that constitutes a building, a first antenna unit 31 is disposed on a first surface of the member, and a second antenna unit 32 is disposed on a second surface adjacent to the first surface, and the antenna sheet 1 can be used as a wireless communication relay that transmits a power signal between the first antenna unit 31 and the second antenna unit 32 via a transmission line unit 4 connected to the first antenna unit 31 and the second antenna unit 32. This is particularly suitable for use when the member that constitutes the building is a fixture of a building.

[0069] Fig. 6 is a schematic diagram showing an example in which the antenna sheet 1 of this embodiment is attached to the wall surface of a building made of concrete, mud, etc. Fig. 7 is a schematic diagram showing an example in which the antenna sheet 1 of this embodiment is attached to a fixture of a building, for example, a door.

[0070] As shown in Figures 6(A) and 6(B), by attaching the antenna sheet 1 to the corners of a building such as a concrete or mud wall, it is possible to extend the communication distance and enable communication in blind spots where radio waves cannot reach, even if there are devices that cause radio wave interference such as cordless phones, fax machines, or microwave ovens in use. Note that the corners of the building do not necessarily have to be right angles.

[0071] Furthermore, by attaching the antenna sheet 1 so that it straddles both sides of obstacles such as doors and windows that cause communication problems, as shown in Figure 7, wireless communication in a space where radio waves are blocked can be performed stably in a simple manner. [Example]

[0072] The following examples are provided to provide a better understanding of the present invention and its advantages, but the present invention is not limited to these examples.

[0073] Example 1 A thermoplastic resin sheet (Polycarbonate sheet DPI-AO manufactured by Mitsubishi Plastics, Inc., thickness 0.075 mm) was prepared as the sheet-like substrate 2, and a conductive wire (self-adhesive coated conductor wire AB15 manufactured by ELEKTRISOLA, Φ0.10 mm) was embedded on one side of the sheet-like substrate 2 using a wiring drawing device (WCE150 manufactured by Ruhlamat, settings: USP1200, speed 40%) equipped with an ultrasonic head, to form an antenna circuit pattern 3 consisting of the conductive pattern shown in Figure 3(A).

[0074] The first antenna unit 31 and the second antenna unit 32 are designed to support 19 channels in the 5 GHz band of the IEEE802.11a international standard. As shown in Figure 1A, the combined length a of the first straight section a and the folded section c is approximately 14.5 mm, which corresponds to 1 / 4 λ of the minimum receiving frequency of 5150 MHz. The combined length b of the second straight section b and the folded section c is approximately 13 mm, which corresponds to 1 / 4 λ of the maximum receiving frequency of 5725 MHz. The folded section c is 3 mm. Also, as shown in Figure 2, the antenna elements are arranged symmetrically in four pairs, with a spacing d between adjacent pairs of antenna elements of 7.5 mm. The transmission line 4 connecting the first antenna unit 31 and the second antenna unit 32 is 50 mm long. Finally, the sheet was cut to a size of 100 mm long x 200 mm wide to produce the antenna sheet 1 shown in Figure 3A.

[0075] Example 2 The antenna sheet 1 was fabricated using the same procedure as in Example 1. At this time, referring to FIG. 1(B), the length a+c obtained by adding the length a of the first straight portion and the length c of the folded portion was set to 13 mm, which corresponds to 1 / 4λ of the maximum reception frequency of the frequency band, the length b+c obtained by adding the length b of the second straight portion and the length c of the folded portion was set to 14.5 mm, which corresponds to 1 / 4λ of the minimum reception frequency of the frequency band, and the length c of the folded portion was set to 3 mm. In other words, the antenna sheet 1 had the same configuration as that of Example 1, except that the lengths a of the first straight portion and b of the second straight portion were swapped.

[0076] (Comparative Example 1) An antenna sheet was fabricated in the same manner as in Example 1. Referring to FIG. 5, the first antenna section 31 and the second antenna section 32 had W1 of 25 mm and W2 of 12.5 mm to correspond to the center frequency of 19 channels in the 5 GHz band of the international standard IEEE802.11a. The folded section was 1 mm, and there were four pairs of antenna elements arranged symmetrically above and below, with the spacing d between two adjacent pairs of antenna elements being 2 mm. This resulted in an antenna sheet in which the first straight section and the second straight section were equal in length.

[0077] The antenna sheets of Examples 1 and 2 and Comparative Example 1 were used to evaluate the transmission and reception characteristics. The evaluation method involved arranging the antenna sheet so that the first and second antenna units were located on the outside and inside of a shielding box, respectively. The boundary (transmission line) between the first and second antenna units was sandwiched and blocked by the shielding box lid. A 5 GHz band signal radiated from a transmitting antenna connected to a signal generator outside the shielding box was received by the first antenna unit. The radio waves re-radiated from the second antenna unit inside the shielding box were received by the receiving antenna inside the shielding box, and the signal level was measured with a spectrum analyzer. This operation was performed at different frequencies. The closer the signal level (transmission and reception characteristics) was to 0, the smaller the signal attenuation.

[0078] The results are shown in Table 1. The antenna sheets of Examples 1 and 2 exhibited stable transmission and reception characteristics in the range of 5150 MHz to 5275 MHz. On the other hand, Comparative Example 1 exhibited good transmission and reception characteristics at 5350 MHz, but showed a tendency for the transmission and reception characteristics to deteriorate when the frequency deviated from the central frequency band.

[0079] [Table 1] [Explanation of symbols]

[0080] 1 Antenna sheet 2. Sheet substrate 3 Conductive pattern (antenna circuit pattern) 31 First antenna part 32 Second antenna part 4 Transmission line section 5 Adhesive layer 6 Protective layer

Claims

1. An antenna pattern made of a conductive line includes at least one pair of line-symmetric antenna elements formed by folding back the conductive line, the antenna element comprises a first straight portion having a length a, a second straight portion having a length b that is parallel to the first straight portion, and a folded portion having a length c that connects the first straight portion and the second straight portion, the length a of the first straight portion being different from the length b of the second straight portion; An antenna pattern in which a plurality of pairs of the antenna elements are provided via feeder lines, and the first linear portions and second linear portions of each are arranged so as to be all parallel to each other.

2. 2. The antenna pattern according to claim 1, wherein one of a length a+c obtained by adding the length a of the first straight portion and the length c of the folded portion and a length b+c obtained by adding the length b of the second straight portion and the length c of the folded portion is ¼λ of a maximum reception frequency in a frequency band of radio waves to be received, and the other is ¼λ of a minimum reception frequency in the frequency band of radio waves to be received.

3. 3. The antenna pattern according to claim 1, wherein the pair of antenna elements at the most distal ends of the antenna pattern are connected as a single conductive line, thereby forming the antenna pattern as a whole as a single continuous linear conductive pattern.

4. An antenna sheet including a sheet-like substrate and an antenna circuit pattern formed of a conductive pattern by folding back a conductive line on one side of the sheet-like substrate, the antenna circuit pattern includes a first antenna portion, a second antenna portion provided apart from the first antenna portion, and a transmission line portion connecting the first antenna portion and the second antenna portion; the first antenna unit and the second antenna unit each include at least one pair of axisymmetric antenna elements, each of the antenna elements comprising a first straight line portion having a length a, a second straight line portion having a length b that is parallel to the first straight line portion, and a folded portion having a length c that connects the first straight line portion and the second straight line portion, and the length a of the first straight line portion is different from the length b of the second straight line portion; An antenna sheet in which, in at least one of the first antenna section and the second antenna section, a plurality of pairs of antenna elements are provided via feeder lines, and the first straight line portions and second straight line portions of each are arranged so that they are all parallel to each other.

5. 5. The antenna sheet according to claim 4, wherein in both the first antenna section and the second antenna section, one of the length a+c obtained by adding the length a of the first straight section and the length c of the folded section and the length b+c obtained by adding the length b of the second straight section and the length c of the folded section is 1 / 4λ of the maximum reception frequency in the frequency band of the radio waves to be received, and the other is 1 / 4λ of the minimum reception frequency in the frequency band of the radio waves to be received.

6. 6. An antenna sheet as described in claim 4 or 5, wherein in at least one of the first antenna section and the second antenna section, a pair of the most distal antenna elements are connected as a single conductive line, and the first antenna section, the second antenna section, and the transmission line section are arranged as a whole as a single continuous linear conductive pattern.

7. 7. The antenna sheet according to claim 4, wherein the transmission line portion is a parallel transmission path in which two conductive lines are arranged in parallel.

8. 8. The antenna sheet according to claim 4, further comprising a protective layer for protecting at least a part of the antenna circuit pattern.

9. The antenna sheet according to any one of claims 4 to 8, further comprising an adhesive layer provided on at least one surface of the sheet-like substrate.

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