JP2008047594A - Radio wave absorber and radio wave shielding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio wave absorber that is provided with a radio wave absorbing layer for absorbing entering waves and a radio wave reflection layer that is arranged on the rear side of the radio wave absorbing layer, and reflects the waves transmitting the radio wave absorbing layer; and that shields waves in a specific frequency band and allows waves in other than the specific frequency band to transmit. <P>SOLUTION: A frequency selection film is used as a radio wave reflection layer 2, wherein waves in at least one frequency band is selectively reflected by a plurality of conductive part 4, 4 and so on. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radio wave absorber that absorbs radio waves or a radio wave shield that blocks radio waves, and more particularly, to a measure that allows transmission of radio waves of frequencies other than a specific frequency band.

  In recent years, there has been a concern about deterioration of the radio wave environment, and accordingly, a radio wave absorber that shields the radio wave by absorbing the incident radio wave has attracted attention.

  As such a radio wave absorber, for example, a radio wave reflection layer (metal plate or low resistance layer) disposed on the back surface of a radio wave absorption layer containing ferrite or carbon is known. In this device, the radio wave transmitted through the radio wave absorption layer while being attenuated is reflected by the radio wave reflection layer, so that the radio wave is attenuated again in the radio wave absorption layer.

  However, in the conventional radio wave absorber, the radio wave reflection layer reflects all the radio waves transmitted through the radio wave absorption layer, so that all the incident radio waves are shielded. There is a disadvantage that even necessary radio waves, such as radio waves in the frequency band used for the radio, cannot be used.

  The present invention has been made in view of such points, and its main object is to use a specific frequency in a radio wave absorber or radio wave shield in which a radio wave reflection layer is disposed on the back side of a radio wave absorption layer or the like. The band radio wave is shielded, while the radio wave other than the specific frequency band is allowed to be transmitted.

In order to achieve the above object, the present invention focuses on a frequency selective film (FSS “Frequency Selective Surface”) that selectively reflects radio waves in a specific frequency band, and uses this for the radio wave reflection layer.
It was arranged on the back side of the radio wave absorption layer.

  Specifically, in the present invention, a radio wave absorption layer that absorbs incident radio waves, and a radio wave reflection layer that is disposed on the back side of the radio wave absorption layer and reflects radio waves transmitted through the radio wave absorption layer are provided. It is assumed that the electromagnetic wave absorber is provided.

  The radio wave reflection layer is made of a frequency selection film that selectively reflects radio waves in at least one frequency band with a plurality of conductive portions, while allowing transmission of radio waves outside the frequency band.

  In the above configuration, each of the conductive portions of the frequency selective film includes three first element portions extending radially from one point, and extending in a direction intersecting with the corresponding first element portion. And a second element portion coupled to the tip. Further, the frequency selective film may be provided so as to reflect a plurality of radio waves having different frequency bands.

  In addition, the frequency selective film described above is arranged on the side opposite to the radio wave incident side of the resistance film, which reflects a part of the incident radio wave and allows the remaining part of the radio wave to pass therethrough. An internal reflection of a predetermined frequency band reflected by the radio wave reflection layer with respect to a surface reflection wave of a predetermined frequency band which is disposed between the radio wave reflection layer and the resistance film and the radio wave reflection layer and is reflected by the resistance film. It can also be used as a radio wave reflecting layer in a radio wave absorber provided with a dielectric layer provided so that a wave has an opposite phase in the resistive film.

  Further, when the configuration of the present invention is viewed from the frequency selective film side, that is, as a radio wave shield provided with a frequency selective film that selectively reflects radio waves in at least one frequency band with a plurality of conductive portions. In this case, it can be considered that the frequency selective film is disposed on the back side of the radio wave absorption layer that absorbs the incident radio wave. In this case, there is an advantage that the frequency band of the shielded radio wave is widened compared to the case where the frequency selective membrane is used alone.

  According to the present invention, on the back side of the radio wave absorption layer, the radio wave reflection layer made of the frequency selective film reflects only radio waves in a specific frequency band and does not reflect radio waves in other frequency bands. While absorbing and shielding only radio waves in the frequency band, transmission of radio waves of other frequencies can be allowed.

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

(Embodiment 1)
FIG. 1 is a cross-sectional view schematically showing the overall configuration of a radio wave absorption board according to Embodiment 1 of the present invention, and this radio wave absorption board reduces reflection of radio waves by absorbing incident radio waves. A board main body 1 as a radio wave absorption layer and a frequency selection film 2 as a radio wave reflection layer which is disposed on the back side of the board main body 1 and reflects radio waves transmitted through the board main body 1 are provided.

The board body 1 is composed of a composition comprising calcium carbonate and talc (magnesium hydrated silicate) as an inorganic base material, a binder resin as a binder, a foaming agent, and conductive carbon as a radio wave loss material. It is a lightweight foamed calcium carbonate board formed by heating and foaming, and has flame retardancy. As the thickness of the board body 1, about 2 to 50 mm, the density is preferably 0.05~0.20g / cm ³ order (more preferably, 0.15 g / cm ³ or less) .

  Here, an example of the manufacturing method of the board body 1 will be briefly described. The composition is placed in a kneader and mixed for 5 minutes, and then 50 parts by weight of organic solvent per 40 parts by weight of calcium carbonate. (Toluene or the like) is gradually added and kneaded for 1 hour. Then, the composition obtained is filled in the mold without any gaps while being pressurized by kneading, sealed with a lid, and pressed with a press. In this state, the binder resin is heated to 170 ° C. to gel, and at the same time, the foaming agent is decomposed. After sufficiently gelling and decomposing, the mold is cooled to room temperature in a pressurized state, the foam is taken out, and heated to 150 ° C. at normal pressure to expand to a predetermined size. Thereafter, the organic solvent is evaporated and completely removed by once cooling to room temperature and then gradually heating to 100 ° C. The board body 1 of this embodiment can be obtained by slicing the foam obtained as described above.

  In addition, it is preferable that it is 50 / 50-95 / 5 as a compounding ratio (calcium carbonate / talc weight ratio) of the said inorganic base material, and it is preferable that it is 50-300 micrometers as an average particle diameter. Examples of the binder resin include vinyl chloride resins, EVA resins, acrylic resins, and the like, and it is preferable to use them in the form of a paste resin having an average particle size of 10 to 30 μm. Moreover, as the content, it is preferable that it is 10-100 weight part with respect to 100 weight part inorganic base material. The foaming agent is not particularly limited as long as it is a substance that decomposes by heating to generate gas. Examples of the foaming agent include organic foaming agents azodicarbonamide, azobisisobutylnitrile, dinitrosopentatetramine, p. -Toluenesulfonyl hydrazide, p, p'-oxybis (benzenesulfonyl hydrazide), sodium bicarbonate as an inorganic blowing agent, ammonium chloride and the like. Moreover, as the content, it is preferable that it is 10-120 weight part with respect to 100 weight part inorganic base material.

  The conductive carbon content in the composition is 5 to 20 parts by weight, preferably 10 to 15 parts by weight with respect to 100 parts by weight of the total amount of the inorganic base material, the binder resin and the foaming agent. . That is, if the content is less than 5 parts by weight, sufficient radio wave absorption capability is not exhibited, while if it is more than 20 parts by weight, uniform foaming is hindered for the increase in radio wave absorption performance. . Incidentally, when the content is within the above range, if the thickness of the board body 1 is 2 to 50 mm (preferably 8 to 15 mm), the return loss with respect to the radio wave in the 5.8 GHz band is 10 dB or more. It becomes. The radio wave loss material may be other than conductive carbon, and by appropriately adopting a known material, it is possible to obtain a return loss of 15 dB or more, further 20 dB or more.

  In this embodiment, a frequency selection sheet 3 as shown in FIG. 2 is used to provide the frequency selection film 2 on the board body 1. In this frequency selection sheet 3, a frequency selection film 2 is formed on a film base 3a, and an adhesive layer 3b and a release liner 3c are sequentially formed on the surface of the film base 3a opposite to the frequency selection film 2. It is layered and rolled up. Then, the frequency selection film 2 can be provided on the board body 1 by cutting the necessary length, peeling off the release liner 3c and sticking it to the board body 1. The film substrate 3a is preferably a polymer film that can be easily formed into a thin roll and has excellent flexibility. In particular, the thickness is generally 10 to 500 μm, preferably 30 to 150 μm, and more preferably 50 to 120 μm.

  On the frequency selective film 2, antennas 4, 4,... As a plurality of conductive portions are regularly arranged. These antennas 4, 4,... Both have frequency selectivity that selectively reflects only radio waves in a specific frequency band, and therefore the frequency selection film 2 reflects only radio waves in the specific frequency band. On the other hand, radio waves of other frequencies are transmitted. Specifically, each antenna 4 has conductivity, and the radio wave reflectance of the antenna 4 with respect to radio waves in a specific frequency band correlates with the conductivity of the antenna 4. That is, the higher the conductivity of the antenna 4 (the smaller the electric resistance of the antenna 4), the higher the radio wave reflectance of the antenna 4. Therefore, by increasing the conductivity of the antenna 4, it is possible to increase the radio wave reflectance of the antenna 4 with respect to radio waves in a specific frequency band. Examples of such a conductive material include aluminum, silver, copper, gold, platinum, iron, carbon, graphite, indium tin oxide (ITO), indium zinc oxide (IZO), a mixture or an alloy thereof. The antenna 4 preferably contains one of copper, aluminum, and silver. This is because copper, aluminum and silver have a relatively low electric resistance among conductive materials and are inexpensive. Among the above conductive materials, silver is particularly preferable from the viewpoint of realizing higher electromagnetic shielding properties and lower costs.

  Each antenna 4 may include fine particles of a conductive material such as copper, aluminum, and silver. For example, a conductive paste in which a powdery conductive material is contained in a binder is used as a film base. It can be obtained by applying uniformly so that a predetermined pattern is formed on the material 3a, and then drying. Specifically, after forming a predetermined pattern of the conductive paste, the antenna 4 is dried by drying for 10 minutes or more and 5 hours or less in an atmosphere of 100 ° C. or higher and 200 ° C. or lower, for example. Obtainable. As such a conductive paste, a powdery conductive material (for example, silver) may be dispersed and mixed in a polyester resin. In this case, the content of the conductive material is preferably 40% by weight or more and 80% by weight or less, more preferably 50% by weight or more and 70% by weight or less. When the content of the conductive material is less than 40% by weight, the conductivity of the antenna 4 tends to decrease. On the other hand, if the content of the conductive material is more than 80% by weight, it tends to be difficult to uniformly disperse and mix in the resin. The antenna 4 may be composed of a conductive film made of a conductive material and an antioxidant film that covers the conductive film.

  In addition, about the formation method of the antenna 4, it is not limited to said method, You may form by another method. For example, a conductive film (for example, an aluminum film or a silver film) is formed on the board body 1 by a film formation method such as vapor deposition, sputtering, or chemical vapor deposition (CVD), and patterning such as photolithography is performed. You may make it pattern to a predetermined shape dimension by the method. In addition, the antenna 4 is formed by, for example, silk printing, pattern pressing, etching, sputtering, vapor deposition (for example, chemical vapor deposition (CVD)), mist coating, or mold fitting. It can also be performed by an embedding method or the like. The thickness T of the antenna 4 is preferably 10 μm or more and 20 μm or less (10 μm ≦ T ≦ 20 μm). That is, when the thickness T of the antenna 4 is smaller than 10 μm (T <10 μm), the conductivity of the antenna 4 tends to be lowered, while the thickness T of the antenna 4 is larger than 20 μm (T> 20 μm). The formability of the antenna 4 tends to decrease.

  In this embodiment, the antennas 4, 4,... Are arranged in a matrix as shown in FIG. These antennas 4, 4,... Are arranged at regular intervals so that adjacent antennas 4, 4 do not contact each other. Each antenna 4 has three first element portions 4a, 4a,... And three second element portions 4b, 4b,. The three first element portions 4a, 4a,... Extend radially from the antenna center C and are formed in a straight line having an angle of 120 ° with each other. Each second element portion 4b extends linearly in a direction orthogonal to the corresponding first element portion 4a, and is coupled to the outer end of the first element portion 4a at the center in the length direction. In the illustrated example, the lengths L1 and L2 of the first and second element portions 4a and 4b are the same (L1 = L2), and the width W1 of the first element portion 4a and the lengths of the second element portions 4b The width W2 is also the same (W1 = W2).

The first element portion length L1 and the second element portion length L2 may be different from each other (L1 ≠ L2). In this case, the relational expression 0 <L2 <2 × 3 ^1/2 × L1 Will be satisfied. That is, when L2 ≧ 2 × 3 ^1/2 × L1, the adjacent second element portions 4b and 4b come into contact with each other, and a desired electromagnetic wave shielding effect cannot be obtained. Furthermore, from the viewpoint of realizing a high shielding rate for a specific frequency band, the second element portion length L2 is not less than 0.5 times and not more than twice the first element portion length L1 (0.5 × L1 ≦ L2). ≦ 2 × L1) is preferable, and 0.75 times or more and 2 times or less (0.75 × L1 ≦ L2 ≦ 2 × L1) is more preferable. Also, the first and second element portion widths W1, W2 may be different from each other (W1 ≠ W2). In the present embodiment, the first and second element portions 4a and 4b are orthogonal to each other, but may be crossed at an angle other than 90 °. Further, the coupling position of the second element part 4b with respect to the first element part 4a may be a position other than the center in the length direction of the second element part 4b.

  By the way, the lengths L1 and L2 of the first and second element portions 4a and 4b of the antenna 4 correlate with the frequency band (specific frequency band) of the radio wave reflected by the antenna 4. For this reason, the length L1 of the first element portion 4a and the length L2 of the second element portion 4b can be appropriately determined according to the frequency band of the radio wave to be shielded by the radio wave absorption board. For example, when the length L1 of the first element portion 4a and the length L2 of the second element portion 4b are the same (L1 = L2), the total length L of the elements of the antenna 4 (L = 3 × L1 + 3 × L2) Hereinafter, the specific frequency band can be lowered by increasing the element length L). Conversely, the specific frequency band can be increased by shortening the element length L.

  Hereinafter, the electromagnetic wave shielding characteristics of the radio wave absorption board according to the lengths L1 and L2 of the first and second element portions 4a and 4b will be described in detail. Here, the first and second element portion widths W1, W2 are both 0.7 mm (W1 = W2 = 0.7 mm).

  First, when the length L1 of the first element portion 4a and the length L2 of the second element portion 4b are the same (L1 = L2), the first element portion length L1 is set to L1 = 10.6 mm. As shown in the characteristic diagram of FIG. 5, the transmittance of radio waves having a frequency in the vicinity of 2.7 GHz is selectively reduced. That is, of the radio waves incident on the radio wave absorption board, radio waves of approximately 2.7 GHz are selectively shielded. This is because the antenna 4 in the frequency selective film 2 of the radio wave absorbing board selectively reflects radio waves having a frequency of approximately 2.7 GHz among the incident radio waves having various frequencies. For measuring the transmission attenuation, a “network analyzer” manufactured by Agilent, USA is used.

  Next, the relationship between the length L1 of the first element portion 4a of the antenna 4 and the frequency band of the radio wave reflected by the antenna 4 is shown in FIG. As can be seen from this characteristic diagram, the frequency band of the radio wave reflected by the antenna 4 becomes lower as the element length L (here, L = 6 × L1) becomes longer. In other words, the longer the element length L, the longer the wavelength of the radio wave reflected by the antenna 4. Therefore, as the element length L becomes shorter, the frequency of the radio wave reflected by the antenna 4 becomes higher (the wavelength becomes shorter). On the other hand, the frequency of the reflected radio wave does not greatly correlate with the widths W1 and W2 of the first and second element portions 4a and 4b, respectively. That is, the frequency of the reflected radio wave is mainly determined by the element length L. Therefore, an appropriate element length L can be obtained from the frequency band (specific frequency band) of the radio wave desired to be reflected by the antenna 4 based on the characteristic diagram of FIG. For example, it is understood that the length L1 of the first element portion 4a should be set to L1≈6 mm in order to shield radio waves having a frequency of about 5 GHz.

  On the other hand, when the first and second element portion lengths L1 and L2 are different from each other (L1 ≠ L2), for example, the length L1 of the first element portion 4a is fixed and only the length L2 of the second element portion 4b is fixed. In other words, the specific frequency band can also be adjusted by changing the ratio (L2 / L1) of the second element portion length L2 to the first element portion length L1. Specifically, the specific frequency band can be lowered by increasing the length L2 of the second element portion 4b, while the specific frequency band can be increased by shortening the length L2 of the second element portion 4b. can do.

  That is, for example, in the case of an antenna having a Y shape (see FIG. 12), the specific frequency band can be adjusted only by changing the first element portion length L1. On the other hand, in the radio wave absorption board according to the present embodiment, as described above, the specific frequency band is also changed by changing both the length L1 of the first element portion 4a and the length L2 of the second element portion 4b. Not only can it be adjusted, but also the specific frequency band can be adjusted by changing the ratio (L2 / L1) of the second element length L2 to the first element length L1, so that the degree of freedom in design is great. A radio wave absorption board can be realized.

  In addition to the above, 800 MHz (800 MHz band) / 900 MHz (900 MHz band) [810 to 957 MHz: mobile phone], 1.5 GHz (1.5 GHz band) [1429] To 1516 MHz: mobile phone] 1.9 GHz (1.9 GHz band) [1884.5 to 1919.5 MHz: PHS], 2 GHz (2 GHz band) [1925 to 2170 MHz: mobile phone], 2.45 GHz (2.45 GHz band) ) [2412 to 2484 MHz: wireless LAN and other ISM bands] 5.25 GHz (5.25 GHz band) [5150 to 5350 MHz: wireless LAN and other ISM bands] It can be applied as appropriate.

  Therefore, in the radio wave absorption board according to the present embodiment, it is specified by a plurality of antennas 4, 4,... Regularly arranged on one surface of the board body 1 made of lightweight foamed calcium carbonate having radio wave absorption. Since the frequency selective film 2 that selectively shields electromagnetic waves in the frequency band is arranged as a radio wave reflecting layer, only the radio waves in the specific frequency band are absorbed and shielded, while the radio waves of other frequencies are The permeation can be allowed. Further, when this radio wave absorbing board is regarded as a radio wave shield having frequency selectivity, when the frequency selective film 2 is used alone, if the frequency band to be shielded is wide, the frequency selectivity is desired. However, in the case of this embodiment, the frequency band of radio waves that can be shielded is widened by a synergistic effect with the board body 1 as a radio wave absorption layer. There is a merit.

  In the present embodiment, electrical grounding is performed when construction is performed to prevent leakage by shielding the radio waves without deteriorating the radio wave environment of equipment using radio waves other than the specific frequency band. There is no need, and since the board main body 1 is lightweight, it does not take time, and since it has nonflammability, it can also be used for parts that require nonflammability.

  In the above embodiment, an example of a manufacturing method in which a binder resin is used as a binder and conductive carbon is used as a radio wave loss material is shown. However, as a binder, rubber or an inorganic material (ceramics, Of course, it can be produced by a known production method using carbonyl iron powder, ferrite powder or the like as a radio wave loss material.

  Moreover, in said embodiment, although the board main body 1 shall be made from the calcium carbonate which is lightweight and has nonflammability, it does not specifically limit as a radio wave absorption layer in this invention. .

(Embodiment 2)
FIG. 7 shows an antenna arrangement in the frequency selective film of the radio wave absorption board according to the second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In this embodiment, each pair of two adjacent antennas 4 and 4 is set so that a pair of second element portions 4b and 4b face each other in parallel as shown in an enlarged view in FIG. An antenna unit 5a is formed in the proximity. Further, the three adjacent antenna units 5a, 5a,... Are formed in a regular hexagonal shape in which the corresponding three sets of second element portions 4b, 4b are arranged close to each other so as to face each other in parallel and are continuously developed in two dimensions. Antenna assembly 5 (array unit). In other words, the antenna assembly 5 is composed of six antennas 4, 4,... Arranged in a regular hexagonal shape in which six pairs of corresponding second element portions 4b, 4b face each other in parallel. Thus, since the antenna assembly 5 has a regular hexagonal shape, it is possible to exhibit a relatively stable electromagnetic wave shielding performance against radio waves incident at various incident angles.

  Further, the six antennas 4, 4,... Constituting the antenna assembly 5 are the 12 second elements of the 18 second element portions 4b, 4b,. The element parts 4b, 4b,... Are arranged in a state in which the corresponding six sets of second element parts 4b, 4b are close to each other, so that the antennas 4 can be arranged with high density. The radio wave reflectivity (electromagnetic wave shielding rate) for radio waves in a specific frequency band can be further improved, and a radio wave absorption board having a high electromagnetic wave shielding rate for radio waves in a specific frequency band can be realized.

  The density of the antennas 4, 4,... Increases as the distance X between the opposing second element portions 4b, 4b decreases. Specifically, the distance X between the second element portions 4b and 4b is preferably 3.0 mm or less (X ≦ 3.0 mm), and more preferably 1.0 mm or less (X ≦ 1.0 mm). ). That is, when the distance X is larger than 3.0 mm (X> 3.0 mm), the electromagnetic wave shielding rate tends to decrease. If the distance X is too small, the second element portions 4b and 4b are likely to contact each other undesirably depending on the method of forming the antenna 4. Therefore, 0.05 mm or more (X ≧ 0.05 mm) is ensured. It is preferable to do so.

  Here, it will be specifically described with reference to FIGS. 9 to 13 that the radio wave absorbing board configured as described above has a relatively high frequency selectivity.

  FIG. 9 is a characteristic diagram showing the electromagnetic wave shielding characteristics of the radio wave absorption board according to the present embodiment. As can be seen from the figure, in the case of the present embodiment, the ratio of the 10 dB bandwidth to the resonance frequency F0 [{(F2−F1) / F0} × 100 (%)] is very small as 10.4%. . That is, the frequency selectivity is very high. On the other hand, for example, in the case of antennas 104, 104,... Having a so-called Jerusalem cross shape as in Modification 1 shown in FIG. The ratio of 10 dB bandwidth (F2-F1) to F0 is 17.0% (> 10.4%), which is larger than in the present embodiment. Further, in the case of the Y-shaped antennas 204, 204,... Arranged in a matrix as in Modification 2 shown in FIG. 12, the electromagnetic wave shielding characteristic is 10 dB with respect to the resonance frequency F0 as shown in FIG. The ratio of bandwidth (F2-F1) is 33.0% (> 10.4%), which is even greater than in the present embodiment. In the above three characteristic diagrams (FIGS. 9, 11, and 13), the resonance frequencies F0 are different from each other, but the 10 dB bandwidth (F2-F1) does not depend on the resonance frequency F0. There is no particular problem. The arrangement distance (vertical / horizontal distance) of Comparative Example 2 is the same as that of Comparative Example 1.

  Therefore, in this embodiment, in addition to the same effects as those in the first embodiment, the 10 dB bandwidth (F2-F1) of the frequency selective film 2 is narrow (high frequency selectivity). There is an advantage that it is difficult to cause deterioration of the radio wave environment.

-Experimental example-
The length L1 of the first element portion 4a of each antenna 4 in the frequency selection film 2 of the radio wave absorption board is fixed to L1 = 12.24 mm, while the length L2 of the second element portion 4b is changed variously. Five types of radio wave absorption boards were produced. The width W1 of the first element portion 4a and the width W2 of the second element portion 4b are W1 = W2 = 1.2 mm.

  Specifically, silver paste was applied onto the board body 1 and dried to form five types of antennas of Examples 1 to 4 and Comparative Example, respectively. At that time, in Example 1, the second element portion length L2 was L2 = 24.48 mm (L1: L2 = 1: 2). In Example 2, the second element portion length L2 was set to L2 = 15.30 mm (L1: L2 = 1: 1.25). In Example 3, the second element portion length L2 was set to L2 = 12.24 mm (L1: L2 = 1: 1). In Example 4, the length L2 of the second element portion was L2 = 9.2 mm (L1: L2≈1: 0.75). In Example 5, the second element portion length L2 was set to L2 = 0 mm. That is, “Y-shaped antenna”.

  The relationship between the frequency and the amount of transmission attenuation in Examples 1 to 5 is shown in the characteristic diagram of FIG. Moreover, the relationship between each ratio (L2 / L1) of the first element portion length L1 and the second element portion length L2 in Examples 1 to 5 and the resonance frequency is also shown in the characteristic diagram of FIG.

  As can be seen from FIG. 14, in Examples 1 to 4 having the second element portion 4b, the electromagnetic wave shielding rate was higher than that in Example 5. From this result, it can be seen that in Examples 1 to 4, radio waves in a specific frequency band can be shielded with a higher electromagnetic wave shielding rate than in Example 5. Moreover, in the case of Examples 1-4, it has a sharper peak than the case of Example 5. That is, it can also be seen that Examples 1 to 4 have higher frequency selectivity than Example 5 and shield radio waves in a specific frequency band with higher selectivity.

  Further, as can be seen from FIG. 15, the resonance frequency tends to decrease as the ratio (L2 / L1) of the first element portion length L1 to the second element portion length L2 increases. From this, it can be seen that the resonance frequency can be adjusted by changing the length L2 of the second element portion 4b.

(Embodiment 3)
FIG. 16 shows a configuration of a radio wave absorption board according to Embodiment 3 of the present invention, and the frequency selection film 2 of this embodiment is a large and small 2 provided to shield radio waves in two different frequency bands. It has various types of antennas 4 and 6. Since the large antenna 4 has substantially the same size and shape as the antenna 4 of the first embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the present embodiment, the frequency selective film 2 includes a plurality of large antennas 4, 4,... And a plurality of small antennas 6, 6,. . The large antennas 4, 4,... And the small antennas 6, 6,... Are arranged at regular intervals so as not to interfere with each other.

  The small antenna 6 is similar to the large antenna 4 and differs from the large antenna 4 only in size. Specifically, as shown in an enlarged view in FIG. 17, the small antenna 6 has three first element portions 6a, 6a,... And three second element portions 6b, as in the case of the large antenna 4. , 6b,... The three first element portions 6a, 6a,... Extend radially from the antenna center Cs and form an angle of 120 ° with each other. Each second element portion 6b extends linearly in a direction orthogonal to the corresponding first element portion 6a, and is coupled to the outer end of the first element portion 6a at the center in the length direction. In the illustrated example, the lengths Ls1, Ls2 of the first and second element portions 6a, 6b are the same (Ls1 = Ls2), and the width Ws1 of the first element portion 6a and the length of the second element portion 6b The width Ws2 is also the same (Ws1 = Ws2).

The first element portion length Ls1 and the second element portion length Ls2 may be different from each other (Ls1 ≠ Ls2). In this case, the relationship 0 <Ls2 <2 × 3 ^1/2 × Ls1 Will satisfy the equation. That is, if Ls ≧ 2 × 3 ^1/2 × Ls1, adjacent second element portions 6b and 6b come into contact with each other, and a desired electromagnetic wave shielding effect cannot be obtained. Further, from the viewpoint of realizing a high shielding rate in a specific frequency band, the second element portion length Ls2 is not less than 0.5 times and not more than twice the first element portion length Ls1 (0.5 × Ls1 ≦ Ls2). ≦ 2 × Ls1) is preferable, and 0.75 times or more and 2 times or less (0.75 × Ls1 ≦ Ls2 ≦ 2 × Ls1) is more preferable. Further, the widths Ws1 and W2 of the first and second element portions 6a and 6b may be different from each other (Ws1 ≠ Ws2). In the present embodiment, the first and second element portions 6a and 6b are orthogonal to each other, but may be crossed at an angle other than 90 °. Further, the coupling position of the second element part 6b with respect to the first element part 6a may be a position other than the center in the length direction of the second element part 6b.

  Furthermore, although only two types of antennas are used for the frequency selective film 2 in the present embodiment, the large antenna 4 and the small antenna 6, an antenna having a shape or size different from that of the large antenna 4 and the small antenna 6 may be used. Good. For example, in an environment where radio waves of three or more types of frequency bands are used, the frequency selective film 2 may be configured by three or more types of antennas having different sizes.

  Each of the large antenna 4 and the small antenna 6 has frequency selectivity. Specifically, the large antenna 4 reflects radio waves in the first frequency band, and the small antenna 6 reflects radio waves in the second frequency band (> first frequency band) higher than the first frequency band. For this reason, the radio wave absorption board according to the present embodiment selectively shields both radio waves in the first frequency band and the second frequency band, and transmits radio waves in other frequency bands.

  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. A radio wave absorption board that shields against leakage of information while transmitting radio waves in other frequency bands that are not used (for example, radio waves used for mobile phones and TV broadcasts). Needed. On the other hand, the radio wave absorption board according to the present embodiment is preferable because it can selectively shield radio waves in two specific frequency bands and transmit radio waves in other frequency bands as described above. It is.

  Here, in the radio wave absorption board configured as described above, the lengths L1 and L2 and the widths W1 and W2 of the first and second element portions 4a and 4b of the large antenna 4 are 11.19 mm (L1 = L2), respectively. = 1.19 mm) and 0.7 mm (W1 = W2 = 0.7 mm), and the lengths Ls1, Ls2 and widths Ws1, Ws2 of the first and second element portions 6a, 6b of the small antenna 6 are 6 respectively. The electromagnetic wave shielding characteristics when 0.05 mm (Ls1 = Ls2 = 6.05 mm) and 0.7 mm (Ws1 = Ws2 = 0.7 mm) will be described.

  FIG. 18 shows the relationship between the frequency of the radio wave incident on the frequency selective film 2 and the transmission attenuation when the radio wave passes through the frequency selective film 2. As can be seen from the figure, radio waves in two frequency bands among the incident radio waves, specifically, radio waves in the 2.45 GHz band and radio waves in the 5.2 GHz band are attenuated together by the radio wave absorption board. In other words, of the incident radio waves, two radio waves in the 2.45 GHz band and the 5.2 GHz band are selectively shielded. This is because radio waves in two specific frequency bands are selectively reflected by the large antenna 4 and the small antenna 6 of the frequency selective film 2. Specifically, the large antenna 4 reflects radio waves in the low first frequency band (2.45 GHz band), and the small antenna 6 reflects radio waves in the second frequency band (5.2 GHz band).

  By the way, in the case of a Y-shaped antenna, it is difficult to arrange two types of large and small linear antennas corresponding to a wireless LAN efficiently and with high density. That is, as in Modification 1 of the present embodiment shown in FIG. 19, when the six large antennas 204, 204,... Adjacent to each other are arranged close to each other in a state where the element portions 204a, 204a face each other in parallel, As for the small antennas 206, 206,..., It is difficult to place the small antennas 206, 206 close to each other, not to mention that the element portions 206a, 206a face each other in parallel, and the large antennas 204, 204,. Can be arranged at a high density, but the number of small antennas 206, 206,... Must be smaller than that of the large antennas 204, 204,. For this reason, the shielding rate for radio waves targeted by the small antennas 206, 206,... Is considerably lower than the shielding rate for radio waves targeted by the large antennas 204, 204,. That is, in the case of a Y-shaped antenna, it is difficult to arrange both the large and small antennas 204 and 206 at a high density, and accordingly, a plurality of radio waves having different frequency bands are shielded with a high shielding rate at the same level. Is difficult.

  Such a situation is the same even when a Jerusalem cross-type antenna is used. That is, when the large antennas 104, 104,... Are arranged close to each other in a matrix shape in which the second element portions 104b, 104b face each other in parallel as in Modification 2 of the present embodiment shown in FIG. As for the antennas 106, 106,..., It is difficult to place the small antennas 106, 106 close to each other as well as the second element portions 106b, 106b face each other in parallel. .. Can be arranged with high density, but the small antennas 106, 106,... Inevitably have a smaller number per unit area than the large antenna 104, and are difficult to arrange with high density. As in the third modification shown in FIG. 21, if only the small antennas 106, 106,... Arranged in the horizontal direction are arranged close to each other so that the second element portions 106b, 106b face each other in parallel, Although the density of the antennas 106, 106,... Increases slightly, this time, the density of the large antenna 104 decreases in the vertical direction. It is difficult to place. Further, in this case, although radio waves in a specific frequency band incident along the arrangement direction of the large and small antennas 104 and 106 (left and right direction in FIG. 21) can be well shielded, the arrangement of the large and small antennas 104 and 106 In the direction that intersects the direction (for example, the vertical direction in the figure), the large antennas 104 and 104 and the small antennas 106 and 106 that are adjacent to each other in the same direction are separated from each other. In other words, the incident angle dependency problem that the electromagnetic wave shielding rate varies greatly depending on the incident direction of the radio wave is caused.

  Therefore, according to the present embodiment, when the two types of large and small antennas 4 and 6 for shielding radio waves in two different frequency bands are arranged on the frequency selection film 2 of the radio wave absorption board, the large antenna 4 As described above, each of the first element portions 4a, 4a,... Extending radially from the antenna center C extends in a direction perpendicular to the corresponding first element portion 4a. While having three second element portions 4b, 4b,... Coupled to the outer end, each of the small antennas 6 includes three first element portions 6a, 6a extending radially from the antenna center Cs. ,..., Each extending in a direction perpendicular to the corresponding first element portion 6a, and three second element portions 6b, 6b,... Coupled to the outer end of the first element portion 6a. Since both the large and small antennas 4 and 6 can be arranged with high density, the radio waves in the two frequency bands are shielded (reflected) with the same electromagnetic wave shielding rate at the same level. As a result, for example, in the case of a wireless LAN environment that uses radio waves of two frequency bands of 2.45 GHz band and 5.2 GHz band, a device such as a mobile phone that uses radio waves of other frequencies Leakage of radio waves from the wireless LAN can be suppressed without deteriorating the radio wave environment.

(Embodiment 4)
22 shows an arrangement of large antennas 4, 4,... And small antennas 6, 6,... In the frequency selective film 2 of the radio wave absorption board according to Embodiment 4 of the present invention. Since the configurations of the large antenna 4 and the small antenna 6 are the same as those in the third embodiment, the same portions are denoted by the same reference numerals and description thereof is omitted. Further, the arrangement of the large antennas 4 is the same regular hexagonal shape as in the second embodiment, and the two large antennas 4 and 4 are arranged close to each other so that the second element portions 4b and 4b face each other in parallel. The pair constitutes a large antenna unit 5a, and three large antenna units 5a, 5a,... Arranged close to each other so that the corresponding three sets of second element portions 4b, 4b face each other in parallel are one large. An antenna assembly 5 is formed. The adjacent large antenna assemblies 5 are arranged close to each other so that the corresponding second element portions 4b and 4b face each other in parallel. In this way, a large number of large antenna assemblies 5 and 5 are arranged. , ... are continuously expanded in two dimensions.

  The small antennas 6 of this embodiment are also arranged in the same manner as the large antennas 4, 4,. That is, the pair of the two small antennas 6 and 6 that are arranged close to each other so that the second element portions 6b and 6b face each other in parallel form a small antenna unit 7a, and corresponding three sets of the second sets. Three small antenna units 7a, 7a,... Arranged close to each other so that the element portions 6b, 6b face each other in parallel constitute a small antenna assembly 7. However, the small antenna assemblies 7 are arranged for each large antenna assembly 5 one by one inside the large antenna assembly 5 in a state of being separated from the other small antenna assemblies 7, 7,. Precisely, the small antenna assemblies 7 are arranged one by one on the inner side of each large antenna assembly 5 and in a portion surrounded by three adjacent large antenna assemblies 5, 5,.

  Similar to the case of the large antenna 4, the radio wave reflectance of the small antenna 6 increases as the small antennas 6 are arranged at a high density so that the distance between the opposing second element portions 6b and 6b is reduced. Specifically, as shown in an enlarged view in FIG. 23, the distance Xs between the opposing second element portions 6b and 6b is preferably 3.0 mm or less (Xs ≦ 3.0 mm), and more preferably in a range. Is 1.0 mm or less (Xs ≦ 1.0 mm). That is, when the distance Xs is larger than 3.0 mm (Xs> 3.0 mm), the radio wave shielding rate tends to decrease. If the distance Xs is too small, the second element portions 6b, 6b are likely to contact each other undesirably depending on the method of forming the small antennas 6, 6,. It is preferable to ensure 0.05 mm or more (Xs ≧ 0.05 mm).

  In order to allow the relatively small antenna 6 to be disposed without shortening the second element portion length L2 of the large antenna 4, the large antenna assembly 5 (first The small antenna assembly 7 (six small antennas 6, 6,... Arranged in a hexagonal shape) in the six large antennas 4, 4,. A relatively small angle θ (for example, θ = 10 °) may be relatively rotated around the center. Also by doing this, it is possible to avoid the second element portion 4b of the large antenna 4 and the second element portion 6b of the small antenna 6 from interfering with each other.

  Therefore, according to the present embodiment, when the frequency selection film 2 of the radio wave absorption board has two types of large and small antennas 4 and 6 that shield two types of radio waves having different frequency bands, the large antennas 4 and 4 Are arranged in a state in which the second element portions 4b, 4b face each other in parallel to form a regular hexagonal large antenna assembly 5, and inside each large antenna assembly 5, there are six small elements. The antennas 6, 6,... Are arranged in a state in which the second element portions 6b, 6b face each other in parallel to form a regular hexagonal small antenna assembly 7. Therefore, the large antennas 4, 4,. And the small antennas 6, 6,... Can be arranged at a high density, so that the radio wave shielding rate (radio wave absorption rate) for the two types of radio waves can be further improved.

  In the above embodiment, the large antenna assembly 5 and the small antenna assembly 7 are both closely packed, but depending on the desired electromagnetic wave shielding rate, they are not closely packed. The number of the bodies 5 and 7 can be adjusted as appropriate.

(Embodiment 5)
FIG. 25 schematically shows a cross section of the radio wave absorption board according to the fifth embodiment of the present invention.

  The present embodiment is the same as the first embodiment in that the frequency selection film 2 is provided on the board body 1 using the frequency selection sheet 3, but the position of the frequency selection film 2 with respect to the board body 1 is the same. Along with this, the configuration of the frequency selection sheet 3 used for providing the frequency selection film 2 is also different.

  In other words, in the case of the first embodiment, the frequency selection film 2 faces the side opposite to the board body 1 (upper side in FIG. 1), whereas in the present embodiment, the frequency selection film 2 is the board. It faces the side of the main body 1 (the lower side in FIG. 25). That is, in the frequency selection sheet 3 of the present embodiment, unlike the case of the first embodiment, as shown in FIG. 26, the frequency selection film 2 is on the same side as the adhesive layer 3b and the release liner 3c in the film substrate 3a. The adhesive layer 3b and the release liner 3c are sequentially laminated on the frequency selective film 2.

  The frequency selective film 2 can selectively reflect radio waves in a specific frequency band even when facing the board body 1 side as in the present embodiment. However, compared to the case where the antenna 4 faces the atmosphere as in the first embodiment, the frequency of the radio wave reflected (shielded) by the antenna 4 even if the shape and the material of the antenna 4 are the same. The band (specific frequency band) is different. Here, FIG. 27 shows the relationship between the first element portion length L1 (1/6 of the element length L) of the antenna 4 and the resonance frequency in the frequency selection film 2 of the radio wave absorption board configured as described above. According to the figure, as can be seen from the case of the first embodiment (see FIG. 4), when the frequency selective film 2 is covered by the board body 1, the frequency selective film 2 is in contact with air. The frequency of the radio wave reflected (shielded) by the frequency selective film 2 becomes lower than the case.

(Embodiment 6)
FIG. 28 is a cross-sectional view showing a configuration of a radio wave absorption board according to Embodiment 6 of the present invention.

  In the present embodiment, unlike the first to fifth embodiments, the frequency selection sheet is not used, and the frequency selection film 2 (actually one type or a plurality of types of antennas) is directly on the board body 1. Is formed. In addition, since the other structure is the same as the case of Embodiment 1-5, description is abbreviate | omitted.

  As a specific method for forming the frequency selective film 2 as described above, as an example, as in the case of the first embodiment, a conductive material in which a powdery conductive material such as copper, aluminum, or silver is contained in a binder. For example, a paste may be used. That is, this conductive paste may be applied uniformly on the board body 1 so that a predetermined pattern is formed, and then dried.

  Therefore, according to the present embodiment, in providing the frequency selective film 2 on the board main body 1, there is no convenience as in the case of the first to fifth embodiments, but in other respects, there are substantially the same effects. Can do.

(Embodiment 7)
FIG. 29 is a cross-sectional view schematically showing the overall configuration of the radio wave absorber according to the seventh embodiment of the present invention.

  The radio wave absorber reflects a part of the incident radio wave, while allowing the remaining part of the radio wave to pass therethrough, and a side opposite to the radio wave incident side of the resistance film 10 (right side in FIG. 29). ), And between the resistance film 10 and the radio wave reflection layer 11, and reflected by the radio wave reflection layer with respect to the surface reflected wave of a predetermined frequency band reflected by the resistance film 10. And an air layer 12 as a dielectric layer provided so that the internal reflection wave in the predetermined frequency band is in reverse phase in the resistive film 10.

  In the present embodiment, the radio wave reflection layer 11 selectively reflects radio waves in at least one frequency band including radio waves in the predetermined frequency band with the antennas 4, 4,. On the other hand, the radio wave other than the above frequency band is composed of a frequency selective film that allows its transmission.

  Specifically, the resistance film 10 is made of a conductive film such as an ITO film, and is formed on a base material 13 such as a polyethylene terephthalate (PET) film. The radio wave reflection layer 11 is also formed on a base material 14 such as a PET film. These base materials 13 and 14 are all arranged on the side opposite to the air layer 12 in order to protect the resistance film 10 and the radio wave reflection layer 11. Furthermore, a spacer 15 that keeps the layer thickness D of the air layer 12 constant is disposed between the resistance film 10 and the base material 14 that carries the radio wave reflection layer 11. In this embodiment, the layer thickness D of the air layer 12 is set to ¼ (D = λ / 4) of the wavelength λ of the radio wave in the predetermined frequency band to be absorbed by the radio wave absorber. The radio wave absorber according to this embodiment is generally called a λ / 4 type radio wave absorber.

  In the radio wave absorber configured as described above, a part of the incident radio wave is reflected on the surface of the resistance film 10, while the remainder of the radio wave is transmitted through the resistance film 10 to the radio wave reflection layer 11. Reach. Of the radio waves that reach the radio wave reflection layer 11, radio waves in a predetermined frequency band are reflected by the radio wave reflection layer 11. Radio waves outside the predetermined frequency band are transmitted through the radio wave reflection layer 11. When the reflected radio wave (internally reflected wave) in the predetermined frequency band reaches the resistance film 10, the phase of the internal reflected wave is the same frequency band radio wave (surface) reflected by the surface of the resistance film 10. Compared with the reflected wave), it is delayed by a distance of twice the layer thickness D of the air layer 12, and the delay is a half wavelength ([λ / 4] × 2 = λ / 2). That is, on the resistance film 10, the internal reflected wave in the predetermined frequency band has an opposite phase to the surface reflected wave in the same frequency band. As a result, the surface reflected wave in the predetermined frequency band among the surface reflected waves is canceled by the internal reflected wave and becomes correspondingly smaller, and as a result, is absorbed by the radio wave absorber.

  On the other hand, since radio waves outside the predetermined frequency band pass through the radio wave reflection layer 11, in the case of the conventional λ / 4 type wave absorber, radio waves other than the predetermined frequency band are internally reflected together with radio waves in the predetermined frequency band. Unlike being shielded, it is not shielded.

  Therefore, according to the present embodiment, the resistance film 10 that reflects a part of the incident radio wave and allows the remainder of the radio wave to pass therethrough is disposed on the opposite side of the resistance film 10 from the radio wave incident side. A radio wave reflection layer 11 that reflects radio waves that have passed through the resistance film 10, and is disposed between the resistance film 10 and the radio wave reflection layer 11. In the λ / 4 type wave absorber, which includes a spacer 15 for ensuring the formation of an air layer 12 having a layer thickness D of ¼ of λ, and absorbs radio waves in a predetermined frequency band, the radio wave reflection layer 11 As described above, a frequency selective film that selectively reflects radio waves in a predetermined frequency band with a plurality of antennas 4, 4,... While allowing transmission of radio waves other than the predetermined frequency band is used. Radio waves other than Unlike the conventional case of shielding them, they can be transmitted.

In the above embodiment, the dielectric is formed between the resistance film 10 and the radio wave reflection layer 11 by the air layer 12 having a layer thickness D of 1/4 of the wavelength λ of radio waves in a predetermined frequency band to be absorbed. Although the layers are configured, a known technique can be appropriately applied as necessary to the configuration of the dielectric layer. Specifically, if the electrical length of the dielectric layer (= free space length × εr ^1/2 [εr: relative dielectric constant of the dielectric layer]) between the resistance film 10 and the radio wave reflection layer 11 is λ / 4. Therefore, a resin layer, a ceramic layer, or the like can be applied to the dielectric layer. In the above embodiment, the frequency selection film as the radio wave reflection layer 11 reflects only radio waves in a predetermined frequency band. However, it is also possible to reflect radio waves in a plurality of frequency bands including the predetermined frequency band.

It is sectional drawing which shows typically the structure of the electromagnetic wave absorption board which concerns on Embodiment 1 of this invention. It is the whole figure (a) and principal part expanded sectional view (b) which show the roll-shaped frequency selection sheet | seat formed separately from the board main body. It is a top view which shows the pattern of the antenna in the frequency selection film | membrane of a radio wave absorption board. It is a top view which expands and shows one antenna. It is a characteristic view which shows the relationship between the frequency and transmission attenuation amount in the electromagnetic wave absorption board whose 1st element part length is 10.6 mm. It is a characteristic view which shows the relationship between the 1st element part length and resonance frequency in an antenna. FIG. FIG. 4 is a view corresponding to FIG. 3 and showing antenna patterns in the frequency selective film of the radio wave absorption board according to Embodiment 2 of the present invention. It is a top view which expands and shows two adjacent antennas. FIG. 6 is a diagram corresponding to FIG. 5 and illustrating the relationship between the frequency and transmission attenuation in the antenna. It is a top view which shows the pattern in which the Jerusalem cross-shaped antenna is arranged in the matrix form as the modification 1 of this embodiment. It is a characteristic view which shows the relationship between the frequency and the amount of transmission attenuation in the modification 1. It is a top view which shows the pattern in which the Y-shaped antenna is arranged in the matrix form as the modification 2 of this embodiment. FIG. 12 is a diagram corresponding to FIG. 11 and illustrating a relationship between a frequency and a transmission attenuation amount in Modification 2. It is a characteristic view which shows together each relationship between the frequency in Example 1-5 of an experiment example, and transmission attenuation amount. It is a characteristic view which shows the relationship between (2nd element part length / 1st element part length) and resonance frequency in an experiment example. It is the FIG. 2 equivalent view which shows the pattern of two types of large and small antennas in the frequency selective film of the electromagnetic wave absorption board which concerns on Embodiment 3 of this invention. FIG. 4 is an enlarged view of a small antenna corresponding to FIG. 3. It is a characteristic view which shows the relationship between the frequency when each 1st element part length of two types of large and small antennas is 11.19 mm and 6.05 mm, respectively, and a transmission attenuation amount. It is a top view which shows the pattern in which two types of large and small Y-shaped antennas are arranged as the modification 1 of this embodiment. FIG. 20 is a view corresponding to FIG. 19 showing a pattern in which two types of large and small Jerusalem cross antennas are arranged as a second modification of the present embodiment. FIG. 20 is a view corresponding to FIG. 19 showing another pattern in which two types of large and small Jerusalem cross-shaped antennas are arranged as a third modification of the present embodiment. FIG. 6 is a view corresponding to FIG. 2 showing patterns of two types of large and small antennas in the frequency selective film of the radio wave absorption board according to Embodiment 4 of the present invention. FIG. 11 is an enlarged view corresponding to FIG. 10 showing two small antennas adjacent to each other. FIG. 23 is a view corresponding to FIG. 22 showing a modification of the fourth embodiment. FIG. 6 is a view corresponding to FIG. 1 schematically showing an overall configuration of a radio wave absorption board according to Embodiment 5 of the present invention. FIG. 7 is a view corresponding to FIG. 6 showing a roll-shaped frequency selection sheet formed separately from the board body. FIG. 5 is a diagram corresponding to FIG. 4 and illustrating the relationship between the length of the first element part and the resonance frequency. It is the FIG. 1 equivalent view which shows typically the whole structure of the electromagnetic wave absorption board which concerns on Embodiment 6 of this invention. It is sectional drawing which shows typically the whole structure of the electromagnetic wave absorber which concerns on Embodiment 7 of this invention. FIG. 30 is a diagram corresponding to FIG. 29 schematically showing the radio wave absorption mechanism.

Explanation of symbols

1 Board body (Radio wave absorption layer)
2 Frequency selective membrane (Radio wave reflection layer)
4 Antenna, large antenna (conductive part)
4a 1st element part 4b 2nd element part 6 Small antenna (conductive part)
6a 1st element part 6b 2nd element part 10 Resistive film 11 Radio wave reflection layer 12 Air layer (dielectric layer)
104 Y-shaped antenna, Y-shaped large antenna (conductive part)
106 Y-shaped small antenna (conductive part)
204 Jerusalem cross type antenna, Jerusalem cross type large antenna (conductive part)
206 Jerusalem Cross Small Antenna (conductive part)

Claims (6)

A radio wave absorber comprising: a radio wave absorption layer that absorbs incident radio waves; and a radio wave reflection layer that is disposed on a back side of the radio wave absorption layer and reflects radio waves that have passed through the radio wave absorption layer,
The radio wave absorption layer is composed of a frequency selection film that selectively reflects radio waves in at least one frequency band with a plurality of conductive portions, while allowing transmission of radio waves in other frequency bands. body. The radio wave absorber according to claim 1,
Each conductive part of the frequency selective membrane is
And three first element portions extending radially from one point, and a second element portion extending in a direction intersecting the corresponding first element portion and coupled to the tip of the first element portion. A featured wave absorber. The radio wave absorber according to claim 1,
The radio wave absorber, wherein the frequency selective film is provided so as to reflect a plurality of radio waves having different frequency bands. A radio wave absorber provided with a frequency selective film that selectively reflects radio waves in at least one frequency band with a plurality of conductive portions, while allowing transmission of radio waves outside the above frequency band,
It has a radio wave absorption layer that absorbs incident radio waves,
The radio wave absorber, wherein the frequency selective film is disposed on a back side of the radio wave absorption layer. A part of the incident radio wave is reflected, while a resistance film that allows the remainder of the radio wave to pass through is disposed on the side opposite to the radio wave incident side of the resistance film, and the radio wave that has passed through the resistance film is reflected. And the predetermined wave reflected by the radio wave reflection layer with respect to a surface reflected wave of a predetermined frequency band that is disposed between the radio wave reflection layer and the resistance film and the radio wave reflection layer. A radio wave absorber comprising a dielectric layer provided so that an internal reflection wave of a frequency band is in an opposite phase in the resistive film,
The radio wave reflection layer selectively reflects a radio wave of at least one frequency band including a radio wave of the predetermined frequency band with a plurality of conductive portions, and from a frequency selection film that allows transmission of a radio wave other than the frequency band. An electromagnetic wave absorber characterized by comprising: A radio wave shield comprising a frequency selective film that selectively reflects radio waves in at least one frequency band with a plurality of conductive portions, while allowing transmission of radio waves outside the above frequency band,
A radio wave shielding body comprising a radio wave absorption layer disposed on the radio wave incident side of the frequency selective film and absorbing incident radio waves.

Images