JP2008103849A - Frequency selective surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frequency selective surface which has a plurality of antennas disposed on the same plane crossing an incident direction of a radio wave, the frequency selective surface being capable of providing transmission/attenuation quantity characteristics for radio waves of two specified frequency bands using one kind of antenna. <P>SOLUTION: Each of the antennas 10 comprises a conductive edge portion 10a which has three or more element portions 11 extending radially from one point P and forms a closed circuit shape extending along an outline of the antenna 10, and a nonconductive void portion 10b enclosed with the edge portion 10a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement in a frequency selective film for two waves that selectively shields radio waves in two different specific frequency bands.

  In recent years, with the development of various communication systems that use radio waves with different frequency bands, such as mobile phones and wireless LANs, only radio waves in a specific frequency band are selectively shielded, while radio waves of other frequencies are transmitted. In order to allow the above, frequency selective membranes (FSS: Frequency Selective Surfaces) in which a large number of antennas having a predetermined shape are arranged on the same plane have attracted attention.

  By the way, for example, in a wireless LAN, radio waves in two frequency bands of 2.45 GHz band and 5.2 GHz band are used. In such an environment, only radio waves in the two frequency bands used are selectively used. It is necessary to allow transmission of radio waves of other frequencies that are not used (for example, radio waves used for mobile phones, TV broadcasts, etc.), while preventing leakage of information. In such a case, a combination of two types of antennas for a low frequency band and a high frequency band is known as a frequency selective film.

  For example, Patent Document 1 describes combining a first antenna having a Y shape with a second antenna having a hollow Y shape surrounding the periphery of the first antenna.

In addition, in the patent document 2, as shown in FIG. 13, the inventors of the present application are connected to the three first element portions extending radially from one point and the tips of the first element portions, and the first element When a novel antenna comprising three second element parts extending in a direction orthogonal to the part is proposed, this antenna is used for a large antenna for a low frequency band (2 GHz band) and a high frequency band (5 GHz band). As shown in FIG. 25, there are two types of small antennas, six large antennas 100, and two first element portions 110 (12 first element portions 110 in total) of each large antenna 100 are hexagonal. The six small antennas 200 are also arranged inside the hexagon so that the two first element portions 210 of each small antenna 200 cooperate to form a hexagon. It is proposed a sequence capable of densely arranged.
Japanese Patent Laid-Open No. 10-126090 (pages 3 to 4, FIG. 6) JP 2006-233457 A (pages 14 to 15, FIG. 18)

  However, in the frequency selective film in which two types of antennas are arranged in combination as in the conventional case, two types of antennas are combined. For this reason, the high density is obtained so as to obtain a high transmission attenuation characteristic. There is a disadvantage that it is difficult to arrange.

  In addition, the arrangement of two types of antennas having different sizes and shapes is more complicated than the case of arranging a single type of antenna, and there is a problem that the appearance is not good. .

  The present invention has been made in view of such a point, and a main object of the present invention is to form a shape of an antenna in a frequency selective film that selectively shields radio waves in a specific frequency band with a plurality of antennas. By adding a contrivance, the object is to obtain transmission attenuation characteristics for radio waves in two specific frequency bands with one type of antenna.

  In order to achieve the above object, the present invention is based on the knowledge that the transmission attenuation characteristics with respect to radio waves in two specific frequency bands can be obtained even though only one type of antenna is obtained by hollowing out the antenna. Only the edge part along the outline of this was made into the electroconductive part, and the inside of this edge part was made into the nonelectroconductive hollow part.

  Specifically, the present invention is premised on a frequency selective film including a plurality of antennas arranged on the same plane intersecting the incident direction of radio waves.

  Each of the antennas has three or more element portions extending radially from one point, and has a closed edge extending along the outline of the antenna, and is surrounded by the edges. It shall consist of a non-conductive hollow part.

  In the above configuration, the number of element portions is preferably one of three or four. In the case of three elements, each of the element parts is defined as a first element part, and in addition to the three first element parts, the element parts are arranged so as to extend in a direction intersecting with the first element parts, and It can have three 2nd element parts connected with the tip of the 1st element part.

  Furthermore, the edge part of each antenna can also have translucency. Specifically, as an example, it is possible to provide a large number of fine openings (translucent holes) at the edge to impart translucency to the edge. In that case, the edge is meshed It can consist of a conductive part formed in a shape.

  According to the present invention, radio waves in two specific frequency bands can be attenuated with one type of antenna, so that it is easy to arrange with high density as compared with the conventional case where two types of antennas are combined. Yes, it can contribute to the improvement of the transmission attenuation characteristic, and can also contribute to the improvement of the appearance by suppressing the complication of the design.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a frequency selective membrane according to Embodiment 1 of the present invention. The frequency selective film includes a large number of antennas 10 regularly arranged in a predetermined pattern on the same plane, and is used in a state where the plane intersects the radio wave incident direction.

  As shown in an enlarged view in FIG. 2, each antenna 10 extends in a direction intersecting with each of the first element portions 11 and three first element portions 11 extending radially from one point P. It consists of a second element part 12 connected to the tip of the first element part 11 at the center. The first element part 11 and the second element part 12 are each linear, and the three first element parts 11 are positioned around the above point with an interval of 120 °. Further, the first element portion 11 and the second element portion 12 corresponding to the first element portion 11 form an angle of 90 °.

  Furthermore, as for the dimensions of the respective parts of the first and second element parts 11 and 12, as an example, the length L1 of the first element part 11 is L1 = 9.0 mm, and the length L2 of the second element part 12 L2 = 8.0 mm, and the widths W1 and W2 of the first and second element portions 11 and 12 are W1 = W2 = 2.0 mm.

  In the present embodiment, each of the antennas 10 includes a conductive edge portion 10a having a closed circuit shape extending along the outline of the antenna 10, and a non-conductive hollow portion surrounded by the edge portion 10a. 10b.

  Specifically, the width Wi1 of the portion of the hollow portion 10b corresponding to the first element portion 11 and the width Wi2 of the portion of the hollow portion 10b corresponding to the second element portion 12 are Wi1 = Wi2 = 1. 0 mm. That is, the line widths Wo1 and Wo2 of the edge portion 10a in the first and second element portions 11 and 12 are Wo1 = Wo2 = 0.5 mm over the entire line of the edge portion 10a. The antennas 10 are arranged so that the center points P of the antennas 10 are positioned at the vertices of equilateral triangles of the same size arranged without gaps, and the lateral pitch C1 between the adjacent antennas 10 and 10 is C1. = 11.4 mm, and the vertical pitch C2 is C2 = 13.2 mm. Here, the horizontal pitch means the pitch in the horizontal direction of the figure, and the vertical pitch means the pitch in the vertical direction of the figure.

  As an example of a specific mode (particularly manufacturing method) of the frequency selective membrane, a powdery material such as copper, aluminum, silver or the like on a surface material (for example, polyethylene terephthalate film) having good radio wave permeability. The antenna 10 may be formed by uniformly applying and drying a conductive paste containing the conductive material in a binder so as to obtain a predetermined pattern.

  Here, in the frequency selective membrane configured as described above, the relationship between the frequency [unit: GHz] and the transmission attenuation [unit: dB] (hereinafter referred to as transmission attenuation characteristic) is examined. Explain the test. As a test object, the length L2 of the second element portion 12 of each antenna 10 is L2 = 8.0 mm (Example 1), 7.0 mm (Example 2), 6.0 mm (Example 3). , 5.0 mm (Example 4). Further, the horizontal pitch C1 and the vertical pitch C2 between the antennas 10 and 10 are C1 = 11.4 mm and C2 = 13.2 mm in the first embodiment, and C1 = 11.2 mm and C2 = 12.mm in the second embodiment. In Example 2, C1 = 10.9 mm and C2 = 12.6 mm, and in Example 2, C1 = 10.7 mm and C2 = 12.3 mm. Table 1 below shows the dimensions of each part and each pitch in Examples 1 to 4. The above results are also shown in FIG.

  As can be seen from FIG. 3, when the transmission attenuation amount on the low frequency side is compared with the transmission attenuation amount on the high frequency side, the transmission attenuation amount on the low frequency side is larger in any case. Each transmission attenuation amount on the high frequency side is 10 dB or more.

  Further, the peak of each transmission attenuation amount on the low frequency side and the high frequency side becomes higher on both the low frequency side and the high frequency side as the length L2 of the second element portion 12 of the antenna 10 becomes shorter. There is a shift. The shift amount at that time is larger on the high frequency side than on the low frequency side.

  Further, as the second element portion length L2 becomes shorter, the peak value of the transmission attenuation on the low frequency side can be seen to decrease slightly, whereas the peak of the transmission attenuation on the high frequency side can be seen. For, there is a clear upward trend.

  Therefore, according to the present embodiment, radio waves in two specific frequency bands can be attenuated with one type of antenna 10, so that the antennas are arranged at a higher density than in the conventional case where two types of antennas are combined. In addition to being able to contribute to the improvement of the transmission attenuation characteristic, it is also possible to contribute to the improvement of appearance by suppressing the complication of the design.

  In the above-described embodiment, the entire region of the edge portion 10a is filled with a conductive material. However, a frequency selective film is attached to a light-transmitting base material (window glass or the like). In this case, in order to provide the antenna 10 with translucency, the conductive portion is arranged in a mesh shape as in Modification 1 shown in FIGS. 4 and 5 so that the edge portion 10a has a substantially rectangular shape. A large number of such openings 20 may be provided. In addition, (a)-(c) of FIG. 5 is a top view which expands and shows the parts ac enclosed by the circle | round | yen in FIG.

  In the above embodiment, the antenna 10 is arranged so that the center point P is positioned at each vertex of the equilateral triangles arranged without gaps on the plane, but the specific arrangement of the antenna 10 is the shape of the antenna 10. It can be designed appropriately according to the required arrangement density. For example, as in Modification 2 shown in FIG. 6, the center points P may be arranged at the vertices of regular hexagons arranged without gaps on the plane.

  Furthermore, in said embodiment, pitch C1, C2 between the antennas 10 and 10 which adjoin each other, the shape of the 1st and 2nd element parts 11 and 12 of each antenna 10, and the 1st and 2nd element parts 11 and 12 Specific numerical values for the lengths L1, L2 and widths W1, W2, the widths Wi1, Wi2 of the hollow portions 10b corresponding to the first and second element portions 11, 12, the widths Wo1, Wo2 of the edge portion 10a, etc. However, these numerical values can be appropriately determined as necessary.

(Embodiment 2)
FIG. 7 shows a frequency selective membrane according to Embodiment 2 of the present invention.

  In the present embodiment, the antenna 10 has three element portions 11 extending radially from one point P as shown in an enlarged manner in FIG. Each element part 11 is linear, and is arranged so as to form a substantially Y shape with an interval of 120 ° around the center point P.

  Regarding the dimensions of each part of the antenna 10, for example, the length L of the element portion 11 is L = 11.5 mm, and the width W of the element portion 11 is W = 3.0 mm. The length Li of the portion of the hollow portion 10b corresponding to the element portion 11 is Li = 10.5 mm, and the width Wi of the hollow portion 10b is Wi = 1.0 mm. In the illustrated example, the line width Wo of the edge portion 10a is Wo = 1.0 mm (= 11.5-10.5) over the entire line. These antennas 10 are arranged so that the lateral pitch C1 between the antennas 10 and 10 is C1 = 13.0 mm and the vertical pitch C2 is C2 = 15.0 mm.

  Here, the frequency selective film having the above-described configuration is set as Example 1, and the length Li of the hollow portion 10b corresponding to the element portion 11 is changed to Li = 7.5 mm and Li = 4.5 mm, respectively. The two types of frequency selective membranes of Example 2 and Example 3 were added, and the transmission attenuation characteristics were measured for these three types of frequency selective membranes. That is, in the second and third embodiments, the line width Wo ′ of the edge portion 10a at the tip of the element portion 11 is Wo ′ = 1.0 mm in the first embodiment, whereas the second and third embodiments. Then, Wo ′ = 4.0 mm (= 11.5−7.5) and Wo ′ = 7.0 mm (= 11.5−4.5), respectively. The horizontal pitch C1 and the vertical pitch C2 between the antennas 10 and 10 are common to each other. The results are also shown in FIG. In addition, in the same figure, in addition to Example 1-Example 3, what does not have a hollow part is shown collectively as a comparative example. Table 2 below shows the dimensions of each part and each pitch in Examples 1 to 3 and the comparative example.

  As can be seen from FIG. 9, as the length Li of the hollow portion 10b corresponding to the element portion 11 becomes shorter, the peak of the transmission attenuation shifts to the high frequency side on both the low frequency side and the high frequency side. ing. It can also be seen that the transmission attenuation on the low frequency side increases while the transmission attenuation on the high frequency side decreases as the hollow portion length Li becomes shorter.

  Therefore, the present embodiment can provide substantially the same effect as that of the first embodiment.

  In the above embodiment, the pitches C1 and C2 between the adjacent antennas 10 and 10, the shape of the element part 11 of each antenna 10, the length L and width W of each element part 11, and the corresponding element part 11 are supported. The width Wi of the hollow portion 10b and the width Wo of the edge portion 10a are described with specific numerical values, but these numerical values can be appropriately determined as necessary.

(Embodiment 3)
FIG. 10 shows the configuration of the frequency selective film according to the third embodiment of the present invention.

  In the present embodiment, each antenna 10 has four element portions 11 extending radially from one point P as shown in an enlarged manner in FIG. Each element portion 11 has a linear shape and is arranged around the center point P at an angle of 90 °.

  Regarding the dimensions of each part of the antenna 10, the length L of the element portion 11 is L = 16.8 mm, and the width W of the element portion 11 is W = 3.0 mm. The length Li of the portion of the hollow portion 10b corresponding to each element portion 11 is Li = 15.8 mm, and the width Wi of the same portion of the hollow portion 10b is Wi = 1.0 mm. The line width Wo of the edge portion 10a is Wo = 1.0 mm over the entire line. These antennas 10 are arranged so that the lateral pitch C1 between the antennas 10 and 10 is C1 = 37.6 mm and the vertical pitch C2 is C2 = 37.6 mm.

  FIG. 12 shows the transmission attenuation characteristic of the frequency selective membrane (Example) having the above-described configuration. For comparison, the transmission attenuation characteristic of a frequency selective film (comparative example) without a hollow portion is also shown. The horizontal pitch C1 and the vertical pitch C2 between the antennas 10 and 10 are common to each other in the example and the comparative example. Table 3 below shows the dimensions of each part and each pitch in Examples and Comparative Examples.

  As can be seen from FIG. 12, in the comparative example, there is only one large peak around 4.9 GHz, whereas in the case of the example, there are two peaks at around 3.0 GHz and around 6.5 GHz. A peak is seen.

  Therefore, according to the present embodiment, substantially the same effect as that of the first embodiment can be obtained.

  In the above embodiment, the pitches C1 and C2 between the adjacent antennas 10 and 10, the shape of the element part 11 of each antenna 10, the length L and width W of each element part 11, and the corresponding element part 11 are supported. The width Wi of the hollow portion 10b and the width Wo of the edge portion 10a are described with specific numerical values, but these numerical values can be appropriately determined as necessary.

  In the first to third embodiments, the case where the number of the element portions 11 is 3 to 4 is described. However, the number of the element portions 11 can be appropriately set as necessary. is there.

  The frequency selective membrane according to the present invention is provided for noise prevention and information leakage, etc., when using radio waves in a specific frequency band without deteriorating the radio wave environment of equipment using radio waves outside the specific frequency band. 2D, such as outer wall panel, inner wall panel, roofing board material, ceiling board material, floor board material, wall covering material (wallpaper, cloth, etc.), glass window, partition (partition etc.), cloth (roll screen, curtain, etc.) By attaching a frequency selection sheet that is provided by directly forming a large number of antennas on a surface material having a wide spread, or formed in advance on a base material such as a transparent resin film It is provided and used.

FIG. 1 is a plan view showing a configuration of a frequency selective film according to Embodiment 1 of the present invention. FIG. 2 is an enlarged plan view showing the antenna. FIG. 3 is a characteristic diagram showing the transmission attenuation characteristic of each frequency selective membrane of Examples 1 to 3 in comparison with the comparative example. FIG. 4 is an enlarged view corresponding to FIG. FIGS. 5A to 5B are plan views showing the enlarged parts a to c of the antenna of the first modification. FIG. 6 is a diagram corresponding to FIG. FIG. 7 is a view corresponding to FIG. 1 and showing the configuration of the frequency selective film according to the second embodiment of the present invention. FIG. 8 is an enlarged view of the antenna shown in FIG. FIG. 9 is a diagram corresponding to FIG. 3 showing the transmission attenuation characteristics of the frequency selective membranes of Examples 1 to 3 in comparison with those of the comparative example. FIG. 10 is a view corresponding to FIG. 1 and showing the configuration of the frequency selective film according to the third embodiment of the present invention. FIG. 11 is an enlarged view of the antenna shown in FIG. FIG. 12 is a view corresponding to FIG. 3 showing the transmission attenuation characteristic of the frequency selective membrane of the example in comparison with that of the comparative example. FIG. 13 is a view corresponding to FIG. 1 showing the structure of a conventional frequency selective film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Antenna 10a Edge part 10b Hollow part 11 1st element part, element part 12 2nd element part

Claims (6)

A frequency selective membrane comprising a plurality of antennas arranged on the same plane intersecting the incident direction of radio waves,
Each of the antennas has three or more element portions extending radially from one point, and has a closed edge extending along the outline of the antenna, and a non-conductive portion surrounded by the edges. A frequency-selective membrane characterized by comprising a hollow portion of a characteristic. The frequency selective membrane according to claim 1,
A frequency selective membrane characterized in that the number of element portions of each antenna is three. The frequency selective membrane according to claim 2,
The element part of each antenna is the first element part,
Each of the antennas is arranged so as to extend in a direction intersecting with each of the first element portions in addition to the three first element portions, and is connected to the second end of the first element portion. A frequency selective membrane having an element part. The frequency selective membrane according to claim 1,
A frequency selective membrane, wherein each antenna has four element portions. The frequency selective membrane according to claim 1,
A frequency selective film, wherein an edge of each antenna has translucency. The frequency selective membrane according to claim 5,
The frequency selective membrane according to claim 1, wherein the edge of each antenna comprises a conductive portion formed in a mesh shape.

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