JP2015045590A - Device and method for measuring electromagnetic wave loss using electromagnetic wave absorption layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring device capable of measuring a loss relating to an electromagnetic wave in a frequency band exceeding 1 GHz.SOLUTION: A measuring device 1 includes: an emission waveguide 11 having a region that becomes wider in cross-section opening along an advancing direction of an electromagnetic wave between a power supply terminal and an emission opening; a first ridge 14 arranged inside the waveguide 11; an incident waveguide 12 having a region that becomes narrower in cross-section opening along the advancing direction of the electromagnetic wave between an emission opening and a detection terminal; a second ridge 15 arranged inside the waveguide 12; and an electromagnetic wave absorption layer including a material for absorbing the electromagnetic wave and covering inner surfaces of the emission waveguide 11 and the incident wave guide 12. The electromagnetic wave absorption layer preferably has a layer thickness distribution in which a layer thickness of a layer portion covering the inner surface of the emission opening becomes larger than the layer thickness of the layer portion covering the inner surface of the power supply terminal. Thereby, resonance of the electromagnetic wave in the emission waveguide 11 is suppressed so as to allow a shield effect in a high frequency band to be measured.

Description

  The present invention relates to a technique for measuring loss characteristics related to electromagnetic waves in a sample such as an electromagnetic shielding material.

  In recent years, with the advancement of sophistication in society, electromagnetic waves in a high frequency band are widely used in wireless communication. Also, various electronic devices used in various scenes radiate high-frequency electromagnetic waves along with their operations. In this way, various electromagnetic shielding materials are currently used in order to prevent malfunction of electronic devices, circuit destruction, and adverse effects on human bodies and the like due to electromagnetic waves that are full of environment. In particular, it is indispensable to apply an electromagnetic shielding material as an EMC (Electro-Magnetic Compatibility) measure for electronic equipment.

  As the electromagnetic shielding material, various materials such as conductive fibers and conductive polymer materials have been developed in place of metal materials, which are traditional materials, due to demands for weight reduction and cost reduction. At this time, it is important to accurately grasp the shielding effect of these electromagnetic wave shielding materials in advance in order to exhibit shielding performance suitable for the application. Conventionally, for example, a KEC (Kansai Electronic industry development Center) method described in Non-Patent Document 1 has been widely used as a method for measuring the shielding effect.

  The shield effect measuring device by the KEC method has an electromagnetic wave transmitting jig and an electromagnetic wave receiving jig, a measurement sample (electromagnetic wave shielding material) is arranged between both jigs, and the transmitted electromagnetic wave signal is transmitted. Measure how much it has attenuated on the receiving side. That is, this apparatus measures the transmission loss of electromagnetic waves and derives the shielding effect of the measurement sample from the result.

Risaburo Sato et al., "EMC Electromagnetic Environment Handbook", Science and Technology Publishing Co., Ltd., September 2009, 597-607 pages

  At present, the frequency of electromagnetic waves used is further increased. For example, the frequency of electromagnetic waves used in mobile phone networks has reached about 0.7 to 2 gigahertz (GHz), and a frequency of about 5 GHz is also used in wireless LANs. Under such circumstances, there are many cases where an electromagnetic shielding material is actually required to guarantee a shielding effect in a frequency band exceeding 10 GHz, for example.

  However, it is difficult for the conventional shield effect measuring apparatus to measure the shield effect in a frequency band exceeding 1 GHz. In fact, when such a high-frequency electromagnetic wave is excited in a conventional apparatus to irradiate the measurement sample, strong resonance occurs between the excited high-frequency electromagnetic wave and the transmitting jig and the receiving jig. . As a result, the high-frequency power obtained as an output fluctuates greatly and contains a large amount of noise, and as a result, an accurate shielding effect cannot be calculated.

  In view of such a problem, an object of the present invention is to provide a measuring apparatus and a measuring method capable of measuring a loss related to an electromagnetic wave in a frequency band exceeding 1 GHz.

  In order to solve the above-described problem, the present invention provides an output waveguide having a portion in which a cross-sectional opening is widened along an electromagnetic wave traveling direction between a power supply end on a power supply side and an output opening from which an electromagnetic wave is output. A first ridge that protrudes from the inner surface of the output waveguide, and an incident opening that faces the output opening of the output waveguide and allows a sample to be placed between the output opening. An incident waveguide having a portion where the cross-sectional opening becomes narrower along the electromagnetic wave traveling direction between the incident opening and the detection end on the electromagnetic wave detecting side, and is arranged to protrude from the inner surface of the incident waveguide A measuring device having a second ridge and an electromagnetic wave absorbing layer that includes a material that absorbs electromagnetic waves and covers the inner surfaces of the outgoing waveguide and the incoming waveguide is provided.

  Here, in the electromagnetic wave absorption layer, the layer thickness of the layer portion covering the inner surface of the exit opening portion covers the inner surface of the feeding end portion on at least the waveguide inner surfaces facing each other at the base of the first ridge. It is preferable to have a layer thickness distribution that is greater than the layer thickness of the layer portion.

  According to the present invention, there is further provided a method for measuring a loss related to an electromagnetic wave of a sample, in which a first ridge is disposed between a feeding end on a power supply side and an emission opening from which the electromagnetic wave is emitted. The inner surface of the output waveguide having a portion where the cross-sectional opening becomes wider along the traveling direction of the electromagnetic wave, the second ridge is disposed inside, and the detection of the incident opening facing the output opening and the side detecting the electromagnetic wave Cover the inner surface of the incident waveguide having a portion where the cross-sectional opening becomes narrower along the traveling direction of the electromagnetic wave with the end with an electromagnetic wave absorbing layer containing a material that absorbs the electromagnetic wave, and between the outgoing opening and the incident opening. A measurement method is provided in which a sample is placed on the sample, and the sample is irradiated with electromagnetic waves excited by supplying power from the power supply end side, and the power generated by the electromagnetic waves transmitted through the sample is detected from the detection end side.

  According to the present invention, it is possible to measure a loss related to an electromagnetic wave in a frequency band exceeding 1 GHz.

It is a perspective view which shows one Example of the shielding effect measuring apparatus by this invention. It is a perspective sectional view by the yz plane of the outgoing horn shown in FIG. It is a top view of the radiation | emission horn shown in FIG. It is a schematic diagram which shows the output ridge arrange | positioned in the output horn shown in FIG. It is a perspective sectional view of the yz plane which shows the outgoing horn of a measuring device without an electromagnetic wave absorption layer. It is a perspective sectional view of the yz plane showing an output horn of a measuring device provided with an electromagnetic wave absorption layer. It is a current density distribution figure in a measuring device in case there is no electromagnetic wave absorption layer. It is a current density distribution figure in a measuring device in case an electromagnetic wave absorption layer is installed. FIG. 4 is a yz-plane cross-sectional view of an output horn for explaining the electromagnetic wave absorbing layer shown in FIGS. 2 and 3. It is yz surface sectional drawing of the output horn which shows the other Example of the electromagnetic wave absorption layer which concerns on this invention. It is yz surface sectional drawing of the output horn which shows other Example of the electromagnetic wave absorption layer which concerns on this invention. It is a top view of the radiation | emission horn which shows other Example of the electromagnetic wave absorption layer which concerns on this invention. It is a front view which shows the apparatus model of the shield effect measuring apparatus which implemented the simulation experiment of the shield effect measurement. It is a graph which shows the simulation experiment result of the shield effect measurement at the time of installing the electromagnetic wave absorption layer with the constant layer thickness shown in FIG. It is a schematic diagram which shows the punching metal used for the Example of the following shield effect measurement. It is a graph which shows the simulation experiment result of the shield effect measurement in the case where the electromagnetic wave absorbing layer having a constant layer thickness is installed and the electromagnetic wave absorbing layer having a layer thickness distribution is installed. It is a graph which shows the simulation result of the shield effect measurement in case the excitation electromagnetic waves by the apparatus model without a guide waveguide part and the installed apparatus model are 3 GHz. It is a graph which shows the simulation result of the shield effect measurement in case the excitation electromagnetic waves by the apparatus model which does not have a guide waveguide part, and the installed apparatus model is 9 GHz.

DESCRIPTION OF EMBODIMENTS Next, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.
[Shielding effect measuring device]
FIG. 1 is a perspective view showing an embodiment of a shield effect measuring apparatus according to the present invention. In the subsequent drawings, an xyz axis coordinate system indicating the orientation of the object shown is displayed as necessary. Here, the z-axis is set as an axis facing the traveling direction of the electromagnetic wave propagating in the apparatus.

  According to FIG. 1, a shield effect measuring apparatus 1 according to the present invention includes an output horn 11 and an input horn 12, and can measure the transmission loss of electromagnetic waves in a measurement sample disposed between both horns. In this embodiment, a guide waveguide section 13 is further provided that relays the output horn 11 and the incident horn 12 while sandwiching the measurement sample. Here, it is preferable that the measurement sample to be held has a plate shape or a sheet shape so that the transmission loss can be easily measured.

  The exit horn 11 has a cross-sectional opening (in a cross section perpendicular to the z-axis) along the electromagnetic wave traveling direction (z-axis direction) between the feeding end 112 on the power supply side and the exit opening 111 from which the electromagnetic wave exits. Is an output waveguide having a widened area. In the tube of the output horn 11, an output ridge 14 as a first ridge is disposed so as to protrude from the inner surface of the output horn 11. On the other hand, the incident horn 12 is disposed along the electromagnetic wave traveling direction (z-axis direction) between the incident opening 121 where the electromagnetic wave is incident and the detection end 122 on the electromagnetic wave detection side (in a cross section perpendicular to the z-axis). It is an incident waveguide having a portion where the cross-sectional opening becomes narrow. In the tube of the incident horn 12, an incident ridge 15 as a second ridge is disposed so as to protrude from the inner surface of the incident horn 12. The exit aperture 111 of the exit horn 11 and the entrance aperture 121 of the entrance horn 12 are opposed to each other via the guide waveguide portion 13, and the measurement sample is held between the guide waveguide portion 13. It is installed between.

  The exit horn 11 (and the exit ridge 14) and the entrance horn 12 (and the entrance ridge 15) each constitute a pyramid-shaped ridge horn antenna having a frequency band of 1 to 18 GHz in this embodiment. High frequency power is supplied from an RF input connector 17 attached to the feeding end 112 side of the output horn 11, and high frequency electromagnetic waves are excited. The high-frequency electromagnetic wave propagates through the output horn 11 to the position of the measurement sample, passes through the measurement sample, and then propagates through the incident horn 12 and then from the RF input connector 18 attached to the detection end 122 side of the incident horn 12. It is taken out as electric power.

  FIG. 2 is a perspective sectional view of the output horn 11 taken along the yz plane. FIG. 3 is a top view of the output horn 11.

  2 and 3, the electromagnetic wave absorption layers 161 and 162 having the characteristic of absorbing electromagnetic waves are provided so as to cover the inner surface of the waveguide (horn) of the output horn 11. The electromagnetic wave absorbing layer 161 is disposed on each of the horn inner surfaces facing each other at the root of the output ridge 14, while the electromagnetic wave absorbing layer 162 is disposed on the horn inner surface facing each other with the output ridge 14 therebetween. It is installed on each.

  Among these, the electromagnetic wave absorption layer 161 has a layer thickness distribution in which the layer thickness of the layer portion covering the inner surface of the exit opening 111 site is larger than the layer thickness of the layer portion covering the inner surface of the feeding end 112 site. The electromagnetic wave absorbing layer 161 of the present embodiment further exhibits a layer thickness distribution that increases along the electromagnetic wave traveling direction (z-axis direction), and has layer surfaces that are parallel to this direction and parallel to each other.

  On the other hand, the electromagnetic wave absorption layer 162 has a constant layer thickness distribution in the present embodiment, but has a distribution in which the layer thickness increases along the electromagnetic wave traveling direction (z-axis direction) as with the electromagnetic wave absorption layer 161. Also good. Here, it is preferable that the entire horn inner surface of the output horn 11 is covered with the electromagnetic wave absorbing layer. This is because if an exposed portion is present on the inner surface of the horn, electromagnetic wave resonance tends to occur at that position. The layer thicknesses of the electromagnetic wave absorbing layers 161 and 162 are the thicknesses in the normal direction of the inner surface of the output horn 11. Here, when the layer is obliquely cut at the layer end face position on the emission opening 111 side, the thickness at the layer end face position is not regarded as the layer thickness.

  Both the electromagnetic wave absorbing layers 161 and 162 can be a layer including a urethane type wave absorber impregnated with carbon particles, for example. For example, the electromagnetic wave absorbing layers 161 and 162 may be formed by attaching a urethane type electromagnetic wave absorbing sheet on the inner surface of the horn. Of course, other types of electromagnetic wave absorbers, such as those obtained by mixing magnetic powder such as ferrite or conductive fibers, etc., or absorbers using a matrix such as polystyrene or rubber are used. And 162 can be configured. Further, the electromagnetic wave absorbing layers 161 and 162 may be formed by solidifying a predetermined liquid obtained by diffusing dielectric powder or fiber, conductor powder or fiber, or magnetic powder or fiber.

  Further, the electromagnetic wave absorbing layers 161 and 162 may have a multilayer structure of two or more layers having different dielectric constants, and the thickness of the entire layer may be reduced or the high frequency electromagnetic wave absorbing performance may be improved. The dielectric constant of each layer can be adjusted, for example, by changing the amount of carbon impregnation. Or you may laminate | stack the layer which consists of a different kind of electromagnetic wave absorber. In the case of such a multilayer structure, the number of layers and the dielectric constant of each layer are determined so that the apparent dielectric constant of the entire multilayer structure is a value suitable for the frequency range of the electromagnetic wave used in the measurement.

  Further, the electromagnetic wave absorbing layers 161 and 162 may have a dielectric constant distribution in which the dielectric constant in the layer changes in the layer thickness direction. This also makes it possible to reduce the thickness of the entire layer and improve the absorption performance of high-frequency electromagnetic waves. Such a dielectric constant distribution can be realized, for example, by changing the carbon impregnation amount in the layer thickness direction.

  In addition, the incident horn 12 and the incident ridge 15, and the electromagnetic wave absorbing layer on the inner surface of the incident horn 12 can also have the same configuration as that shown in FIGS. Two ridge horn antennas having the same structure may be matched to form an output horn 11 and an output ridge 14, and an input horn 12 and an input ridge 15.

  FIG. 4 is a schematic diagram showing the output ridge 14 disposed in the output horn 11.

  According to FIGS. 4, 2, and 3, the output ridge 14 protrudes from the center of each of the horn inner surfaces facing each other in the output horn 11 and widens the distance between each other along the electromagnetic wave traveling direction (z-axis direction). It is two blade-shaped metal plates arrange | positioned in the extended form. Further, a coaxial power feeding portion 141 for supplying high frequency power is provided between these metal plates. The coaxial power feeding unit 141 is connected to the RF input connector 17 and takes in high-frequency power from the outside via the RF input connector 17.

  By supplying high-frequency power from the coaxial power feeding section 141, an electric field is generated between the output ridge 14 and the output horn 11, and high-frequency electromagnetic waves are excited in the output horn 11. The excited high-frequency electromagnetic wave propagates in the z-axis direction (direction toward the measurement sample) on the same principle as a TEM wave (Transverse Electro-Magnetic Wave) travels in the TEM cell in a direction perpendicular to the electric field and magnetic field. A part of the electromagnetic wave incident on the measurement sample is absorbed or reflected, but the electromagnetic wave transmitted through the measurement sample generates an electric field between the incident ridge 15 and the incident horn 12 and z in the incident horn 12 It propagates in the axial direction and is taken out as output power from the RF output connector 18.

The incident ridge 15 can also have the same structure as in FIG. In this case, the coaxial power feeding unit 141 in FIG. 4 serves as a power outlet.
[Electromagnetic wave absorption layer]
FIG. 5 and FIG. 6 are perspective sectional views of the yz plane showing the output horn of the measuring device without the electromagnetic wave absorbing layer and the measuring device provided with the electromagnetic wave absorbing layer, respectively. FIGS. 7 and 8 are current density distribution diagrams in the measuring apparatus when there is no electromagnetic wave absorbing layer and when it is installed. Further, FIG. 9 is a yz plane cross-sectional view of the output horn 11 for explaining the electromagnetic wave absorbing layer 161 shown in FIGS.

  The current density distribution diagram of FIG. 7 shows the current density distribution on the horn inner surface and the ridge surface when an 8 GHz high frequency electromagnetic wave is excited in the horn without the electromagnetic wave absorbing layer shown in FIG. Yes. On the other hand, the current density distribution diagram of FIG. 8 shows the inner surface of the horn when an electromagnetic wave absorbing layer having a constant layer thickness distribution shown in FIG. The current density distribution on the ridge surface is shown. In the distribution diagrams of FIG. 7 and FIG. 8, portions having the same lightness are portions having the same current density, and the higher the lightness, the higher the current density.

  According to FIG. 7, it can be seen that when there is no electromagnetic wave absorbing layer, the excited electromagnetic wave is reflected by the entire horn and ridge and resonates to generate a current in a wide range. On the other hand, according to FIG. 8, when the electromagnetic wave absorption layer is installed, the generation of current is suppressed as a whole, but current is still generated in the ridge root portion near the exit opening and the entrance opening of the horn. Resonance related to the portion remains. Thus, it can be seen that by installing the electromagnetic wave absorbing layer having a constant layer thickness distribution, the resonance of the electromagnetic wave due to the shape of the horn and the ridge is considerably reduced. On the other hand, it is understood that even when the electromagnetic wave absorbing layer is provided, the resonance related to the root portion of the ridge near the exit aperture and the entrance aperture remains.

In order to suppress this remaining resonance, the layer thickness of the electromagnetic wave absorbing layer 161 near the emission opening 111 is increased as shown in FIG. Specifically, a layer thickness distribution that changes from the minimum layer thickness t _min to the maximum layer thickness t _max is set in the electromagnetic wave absorption layer 161 along the electromagnetic wave traveling direction (z-axis direction). By realizing such a layer thickness distribution of the electromagnetic wave absorbing layer 161, an electromagnetic wave positioned between the opposing maximum layer thickness t _max portions of the electromagnetic wave absorbing layer 161 is caused between the ridges in the emission opening 111 shown in FIG. Concentration at the center F eliminates the concentration of the current density distribution as shown in FIG. Thereby, resonance of electromagnetic waves can be sufficiently suppressed.

  In particular, in the electromagnetic wave absorption layer 161, by increasing the layer thickness of the layer portion covering the inner surface of the exit opening 111, the above-described concentration of the current density distribution is more effectively eliminated. Thus, the layer thickness distribution of the electromagnetic wave absorbing layer 161 is preferably determined so as to reduce the maximum value of the current density on the inner horn surface of the output horn 11 and the surface of the output ridge.

  Here, it is also preferable to increase the thickness of the electromagnetic wave absorption layer in the vicinity of the incident aperture 121 of the incident horn 12. Thereby, the resonance of the electromagnetic wave can be sufficiently suppressed even in the incident horn 12. That is, also in the incident horn 12, it is preferable to determine the layer thickness distribution of the electromagnetic wave absorbing layer so as to reduce the maximum value of the current density on the inner surface of the horn and the surface of the output ridge.

  It is also possible to take out the output horn side of the shield effect measuring apparatus 1 having the electromagnetic wave absorption layer described above and irradiate the measurement sample with the electromagnetic wave emitted from the exit opening of the exit horn. In this case, since the electromagnetic wave in which the resonance noise is suppressed is irradiated, for example, the reflection loss (reflection coefficient) in the high frequency band of the measurement sample can be measured more accurately than before.

  FIGS. 10 and 11 are yz-plane cross-sectional views of an output horn showing another embodiment of the electromagnetic wave absorption layer according to the present invention, and FIG. 12 shows still another embodiment of the electromagnetic wave absorption layer according to the present invention. It is a top view of an output horn.

  According to FIG. 10, the electromagnetic wave absorbing layer 163 is disposed on each of the horn inner surfaces facing each other at the base of the emission ridge. The layer thickness of the electromagnetic wave absorbing layer 163 increases along the electromagnetic wave traveling direction (z-axis direction), but the distance between the opposing layer surfaces is narrowed along the electromagnetic wave traveling direction (z-axis direction). On the other hand, according to FIG. 11, the electromagnetic wave absorbing layer 164 is also disposed on each of the horn inner surfaces facing each other at the base of the emission ridge. Further, the layer thickness of the electromagnetic wave absorbing layer 164 also increases along the electromagnetic wave traveling direction (z-axis direction), but the interval between the opposing layer surfaces is increased along the electromagnetic wave traveling direction (z-axis direction). . Also with the electromagnetic wave absorbing layer of these embodiments, the excited electromagnetic wave can be concentrated at the center between the ridges in the emission opening, and the resonance of the electromagnetic wave can be sufficiently suppressed.

According to FIG. 12, the electromagnetic wave absorption layer 166 has a layer thickness distribution in which the layer thickness increases along the electromagnetic wave traveling direction (z-axis direction), like the electromagnetic wave absorption layer 165. That is, not only the electromagnetic wave absorbing layer 165 disposed on the inner surface of the horn facing each other at the base of the outgoing ridge, but also the electromagnetic wave absorbing layer 166 installed on the inner surface of the horn facing each other with the outgoing ridge interposed therebetween. In addition, the layer thickness distribution of the layer portion covering the inner surface of the exit opening portion is larger than the layer thickness of the layer portion covering the inner surface of the feeding end portion. The electromagnetic wave absorbing layer having such an aspect can also concentrate the excited electromagnetic wave at the center between the ridges in the emission opening, and sufficiently suppress the resonance of the electromagnetic wave.
[Shield effect measurement]
Examples of shield effect measurement by the shield effect measuring apparatus of the present invention will be described below. First, the shielding effect will be described. The shield effect SE is generally calculated by the following equation (1).

Here, E ₀ is the electric field strength (transmission level) at the incident horn 12 when the measurement sample is not installed in the apparatus 1 (in the case of a blank), and _ES is when the measurement sample is installed in the apparatus 1. The electric field strength (transmission level) at the incident horn 12 (in the electromagnetic wave transmitted through the sample). P ₀ is the power output from the RF output connector 18 (FIG. 1) of the incident horn 12 in the case of a blank, and P _S is output from the RF output connector 18 when the measurement sample is installed in the apparatus 1. Electric power.

  FIG. 13 is a front view showing a device model of the shield effect measuring device 1 in which a simulation experiment for shield effect measurement was performed.

As shown in FIG. 13, in the embodiment shown below, unless otherwise specified, the measurement sample is sandwiched and installed in the guide waveguide portion 13 of the device model of the shield effect measuring device 1. Further, the length L _z in the z-axis direction of the output horn 11 and the incident horn 12 of the measurement model was 152 mm. The length 2L _g in the z-axis direction of the guide waveguide portion 13 was 100 mm (L _g = 50 mm). Further, the width W _x (FIG. 3) in the x-axis direction of the exit aperture was 240 mm, and the height H _y (FIG. 3) in the y-axis direction of the exit aperture was 139 mm. The thicknesses of the exit ridge 14 and the entrance ridge 15 were 8.6 mm.

  FIG. 14 is a graph showing the results of a simulation experiment for measuring the shielding effect when the electromagnetic wave absorbing layer having a constant layer thickness shown in FIG. 6 is installed.

In this example, a simulation experiment for measuring the shielding effect was performed using the apparatus model in which the electromagnetic wave absorbing layer having a constant layer thickness shown in FIG. 6 was installed. The measurement sample has a relative dielectric constant of 9, a thickness of 0.5 micrometers (μm), and conductivity σ of 5.8 × 10 ⁴ S / m, 5.8 × 10 ⁵ S / m, and 5.8 × 10 ⁶ S, respectively. There were 4 types of / m and 5.8 × 10 ⁷ S / m. In the graph of FIG. 14, the frequency (GHz) of the excited electromagnetic wave is plotted on the horizontal axis, and the measured shielding effect (dB) is plotted on the vertical axis. The solid line in the graph is obtained as a result of performing spline interpolation on the simulation value of the shielding effect. The broken line indicates the theoretical value of the shielding effect calculated using the equivalent transmission path method approximated by plane waves.

According to FIG. 14, the shielding effect shows a value close to the theoretical value in any measurement sample. That is, by installing an electromagnetic wave absorbing layer, the shielding effect close to the theoretical value is obtained in the frequency range of 1 to 13 GHz for a measurement sample having an electrical conductivity σ ranging from 5.8 × 10 ⁴ S / m to 5.8 × 10 ⁷ S / m. Measurements can be obtained. However, fluctuations in the shielding effect can be seen along the horizontal axis (frequency). As described with reference to FIG. 8, this variation is caused by resonance that remains even if an electromagnetic wave absorption layer having a constant layer thickness is provided.

  FIG. 15 is a schematic diagram showing a punching metal used in Examples of the following shielding effect measurement.

  As shown in FIG. 15, the punching metal is a metal plate having a thickness t in which through holes having a diameter d are arranged in a square lattice pattern with a pitch a. The theoretical value of the shielding effect SE of the punching metal is calculated by the following equation (2).

Here, λ ₀ is the wavelength of the electromagnetic wave irradiated to the punching metal. The theoretical value of the shielding effect of the formula (2) is a value when a plane wave is vertically irradiated onto a punching metal having an infinite surface.

  Hereinafter, two examples in which a simulation experiment of shield effect measurement was performed using a punching metal from which a theoretical value of the shield effect SE was derived will be described.

  Here, in one example, a simulation experiment for measuring the shielding effect of punching metal was performed using an apparatus model including the electromagnetic wave absorbing layer 167 having a constant layer thickness shown in FIG. In the other embodiment, a simulation experiment for measuring the shielding effect of the punching metal was carried out by the apparatus model including the electromagnetic wave absorbing layer 161 having the layer thickness distribution shown in FIG. 2 and the electromagnetic wave absorbing layer 162 having a constant layer thickness. . Three types of punching metal having a pitch a of 3 millimeters (mm), a thickness of 0.5 mm, and through-hole diameters d of 1 mm, 2 mm, and 3 mm were used.

The constant thickness of the electromagnetic wave absorbing layer 167 was 10 mm. On the other hand, the electromagnetic wave absorbing layer 161 had a layer thickness distribution in which the maximum layer thickness t _max (FIG. 9) was 36 mm and the minimum layer thickness t _min (FIG. 9) was 1 mm. The constant thickness of the electromagnetic wave absorbing layer 162 was 10 mm. Furthermore, the relative dielectric constant of the electromagnetic wave absorbing layer 167 and the electromagnetic wave absorbing layers 161 and 162 was 2, and the conductivity was 0.8 S / m.

  FIG. 16 is a graph showing the results of a simulation experiment for measuring the shielding effect when an electromagnetic wave absorbing layer having a constant layer thickness is installed and when an electromagnetic wave absorbing layer having a layer thickness distribution is installed.

  In the graph of FIG. 16, the horizontal axis represents the frequency (GHz) of the excited electromagnetic wave, and the vertical axis represents the measured shielding effect (dB). The solid and dotted lines in the graph are obtained as a result of performing spline interpolation on the simulation value of the shielding effect in the case of an electromagnetic wave absorption layer having a constant layer thickness and in the case of an electromagnetic wave absorption layer having a layer thickness distribution, respectively. It is a thing.

  According to FIG. 16, in the case of an electromagnetic wave absorption layer having a constant layer thickness, fluctuations showing resonance are observed in the measured frequency range of 2 to 10 GHz at any of d = 1, 2 and 3 (mm). In particular, a peak showing strong resonance appears at a frequency of around 3.1 GHz. This corresponds to the resonance corresponding to the current density distribution concentrated at the root portion of the ridge near the exit opening and the entrance opening of the horn described in FIG.

  On the other hand, in the case of an electromagnetic wave absorption layer having a layer thickness distribution, compared to the case of an electromagnetic wave absorption layer with a constant layer thickness, fluctuations corresponding to resonance are suppressed in the frequency range of 2 to 10 GHz, and stable measurement results are obtained. It can be seen that Incidentally, in the graph of FIG. 16, when the layer thickness is constant (dotted line), many ripples generated by the smoothing process are removed, but when the layer thickness distribution is given (solid line), the smoothing process is not performed. Nevertheless, an output with suppressed ripples is obtained.

  Next, the influence of the guide waveguide unit 13 on the shield effect measurement will be examined.

  FIG. 17 is a graph showing a simulation result of the shielding effect measurement when the excitation electromagnetic wave is 3 GHz by the device model without the guide waveguide portion 13 and the installed device model. FIG. 18 is a graph showing a simulation result of the shield effect measurement when the excitation electromagnetic wave is 9 GHz by the device model without the guide waveguide section 13 and the installed device model.

The electromagnetic wave absorbing layers installed in both device models were the electromagnetic wave absorbing layers 161 and 162 in FIG. The electromagnetic wave absorbing layer 161 had a layer thickness distribution in which the maximum layer thickness t _max (FIG. 9) was 36 mm and the minimum layer thickness t _min (FIG. 9) was 1 mm. The constant thickness of the electromagnetic wave absorbing layer 162 was 10 mm. Furthermore, the relative dielectric constants of the electromagnetic wave absorbing layers 161 and 162 were 2, and the electrical conductivity was 0.8 S / m.

  In the graphs of FIGS. 17 and 18, the horizontal axis represents the pitch a (mm) of the punching metal as the measurement sample, and the vertical axis represents the shielding effect (dB). Here, the shielding effect (dB) is plotted so that the value increases downward on the vertical axis. In addition, the simulation result of the measurement of the shielding effect of the punching metal by the device model without the guide waveguide portion is indicated by a triangle mark, while the measurement of the shielding effect of the punching metal by the device model including the guide waveguide portion 13 is simulated. The result is shown by a dotted line.

  According to FIG. 17, when the frequency of the excitation electromagnetic wave is 3 GHz, both the case where the guide waveguide unit 13 is not provided and the case where the guide waveguide unit 13 is installed generally show values as theoretical values. The result is closer to the theoretical value. On the other hand, according to FIG. 18, when the frequency of the excitation electromagnetic wave is 9 GHz, both the case where the guide waveguide portion 13 is not provided and the case where the guide waveguide portion 13 is installed generally show values close to the theoretical values, and the results of both are almost the same.

  As described above, even when the guide waveguide unit 13 is installed, a shielding effect almost as the theoretical value is obtained as a measurement result. Incidentally, the fact that the measured value of the shielding effect matches the theoretical value indicates that the electromagnetic wave irradiated to the measurement sample in this measurement device (model) is almost a plane wave and is incident on the measurement sample perpendicularly. ing.

  As described above, according to the present invention, the electromagnetic wave loss of the measurement sample, particularly the shielding effect, can be measured even in a frequency band exceeding 1 GHz by installing the electromagnetic wave absorption layer on the inner surface of the horn. Thereby, for example, it becomes possible to appropriately evaluate the shielding performance in the high-frequency band of the electromagnetic shielding material that is expected to increase in demand in the future.

  In addition, by using an electromagnetic wave absorption layer having a layer thickness distribution in which the layer thickness of the layer portion that covers the inner surface of the exit opening portion and the entrance opening portion of the horn is larger, a frequency band whose upper limit exceeds 10 GHz, for example, 1 In addition, accurate measurement of shielding effect in the range of 18GHz is also possible.

1 Shielding effect measuring device
11 Output horn (output waveguide)
111 Outgoing aperture
112 Feeding end
12 Incident horn (incident waveguide)
121 Entrance aperture
122 Detection end
13 Guide waveguide
14 Outgoing ridge (first ridge)
141 Coaxial feeder
15 Incident ridge (second ridge)
161, 162, 163, 164, 165, 166, 167 Electromagnetic wave absorbing layer
17 RF input connector
18 RF output connector

Claims (10)

A measuring device capable of measuring a loss related to an electromagnetic wave of a sample,
An output waveguide having a portion where the cross-sectional opening becomes wider along the electromagnetic wave traveling direction between the power supply end on the power supply side and the output opening from which the electromagnetic wave is output;
A first ridge disposed to protrude from the inner surface of the exit waveguide;
A cross-sectional opening along the electromagnetic wave traveling direction between the incident opening and a detection end on the side for detecting the electromagnetic wave is provided. An incident waveguide having a narrowed portion;
A second ridge disposed protruding from the inner surface of the incident waveguide;
A measuring device comprising a material that absorbs electromagnetic waves, and an electromagnetic wave absorbing layer that covers an inner surface of the outgoing waveguide and the incoming waveguide.   2. The measurement apparatus according to claim 1, wherein the electromagnetic wave absorbing layer has a layer thickness of a layer portion that covers the inner surface of the exit opening portion on at least the waveguide inner surfaces facing each other at the base of the first ridge. Has a layer thickness distribution which is larger than the layer thickness of the layer portion covering the inner surface of the feeding end portion.   3. The measurement apparatus according to claim 2, wherein the electromagnetic wave absorbing layer has a layer thickness of a layer portion covering an inner surface of the emission opening portion even on an inner surface of the waveguide facing each other with the first ridge interposed therebetween. Has a layer thickness distribution which is larger than the layer thickness of the layer portion covering the inner surface of the feeding end portion.   4. The measuring apparatus according to claim 2, wherein the electromagnetic wave absorbing layer is a layer portion layer that covers the inner surface of the incident opening portion even on the inner surfaces of the waveguides facing each other at the base of the second ridge. A measuring apparatus having a layer thickness distribution in which a thickness is larger than a layer thickness of a layer portion covering an inner surface of the detection end portion.   5. The measuring device according to claim 2, wherein the electromagnetic wave absorption layers are parallel to the traveling direction of the electromagnetic wave and are parallel to each other on at least the waveguide inner surfaces facing each other at the base of the first ridge. A measuring apparatus having parallel layer surfaces.   6. The measuring apparatus according to claim 2, wherein the electromagnetic wave absorbing layer is determined so as to reduce a maximum value of current density on an inner surface of the output waveguide and a surface of the first ridge. Measuring device having a distributed layer thickness distribution.   7. The measurement apparatus according to claim 1, wherein the exit waveguide and the entrance waveguide are pyramid-shaped horns, and the first ridge and the second ridge are respectively provided with the exit ridge. A measuring apparatus, characterized in that it is arranged in such a manner that it protrudes from the center of each of the waveguide and the inner surface facing each other in the incident waveguide and extends along the traveling direction of the electromagnetic wave.   8. The measurement apparatus according to claim 1, further comprising a guide waveguide section that relays and connects the exit waveguide and the entrance waveguide. apparatus. A measuring device capable of measuring a loss related to an electromagnetic wave of a sample,
An output waveguide having a portion where the cross-sectional opening becomes wider along the electromagnetic wave traveling direction between the power supply end on the power supply side and the output opening from which the electromagnetic wave is output;
A ridge disposed to protrude from the inner surface of the output waveguide;
A measuring apparatus comprising: an electromagnetic wave absorbing layer that includes a material that absorbs electromagnetic waves and covers an inner surface of the output waveguide. A method for measuring a loss related to an electromagnetic wave of a sample,
A first ridge is disposed therein, and an inner portion of an output waveguide having a portion where a cross-sectional opening is widened along an electromagnetic wave traveling direction between a feeding end on a power supply side and an output opening from which the electromagnetic wave is emitted. Incidence having a surface and a second ridge disposed therein, and a portion where the cross-sectional opening becomes narrower along the electromagnetic wave traveling direction between the incident opening facing the emission opening and the detection end on the side for detecting the electromagnetic wave Cover the inner surface of the waveguide with an electromagnetic wave absorbing layer containing a material that absorbs electromagnetic waves,
A sample is placed between the exit aperture and the entrance aperture,
A measurement method comprising: irradiating the sample with an electromagnetic wave excited by supplying power from the power supply end side; and detecting the power generated by the electromagnetic wave transmitted through the sample from the detection end side.