Electromagnetic wave testing device and electromagnetic wave testing method

Abstract

To provide an electromagnetic wave testing device that can improve the uniformity of the electric field strength on a grounded metal mounting table when conducting a radiation immunity test using a low frequency band in a reflection box.SOLUTION: An electromagnetic wave testing device includes: a reflection box; an antenna installed in the reflection box and radiating electromagnetic waves at a frequency lower than the resonant frequency of the reflection box; a flat-plate-shaped mounting table having a conductive mounting surface including a first side and a second side opposite the first side on which a test piece is placed; a first grounding part electrically connecting an object at ground potential to the first side; and a second grounding part electrically connecting the object to the second side.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an electromagnetic wave testing device and an electromagnetic wave testing method. [Background technology]

[0002] Research and development is underway on electromagnetic wave testing equipment that uses a reverberation chamber to perform radiated immunity testing. Radiated immunity testing involves applying a uniform, high-intensity electric field to an electronic device placed inside a reverberation chamber as a test piece to verify whether the device operates normally. Note that in this specification, the term "electric field" may be interpreted as either a magnetic field or an electromagnetic field.

[0003] A reverberation chamber may, for example, be comprised of a metal cavity resonator, an antenna device that radiates electromagnetic waves into the cavity resonator, and an electromagnetic stirrer that stirs the electromagnetic waves radiated from the antenna device. The reverberation chamber generates an electric field applied to a test specimen through the resonance phenomenon of the electromagnetic waves within the cavity resonator. The distribution of the intensity of the electric field thus generated is subject to variations in intensity due to the dimensions of the cavity resonator. In other words, the distribution of the intensity of the electric field generated by the cavity resonator is non-uniform. Therefore, the electromagnetic stirrer stirs the electromagnetic waves within the cavity resonator, bringing the distribution of the intensity of the electric field generated by the cavity resonator closer to a uniform distribution. This allows users to perform radiated immunity tests with high test quality. For convenience of explanation, this specification will refer to this method of performing radiated immunity tests using the resonance phenomenon within a reverberation chamber as the reverberation chamber method.

[0004] In the resonator chamber method, it is known that the resonant frequency of the cavity resonator is inversely proportional to the size of the cavity resonator. Therefore, in radiated immunity testing using the resonator chamber method, the lower the frequency of the electric field generated in the resonator chamber using the resonance phenomenon, the larger the volume of the resonator chamber must be.

[0005] On the other hand, in radiated immunity testing using an anechoic chamber instead of a reverberation chamber, a low-frequency electric field is applied to electronic devices inside the anechoic chamber. The low-frequency band refers to a frequency band below the lowest usable frequency (LUF) at which the reverberation chamber functions, or below the lowest resonant frequency (i.e., the first resonant frequency) of the reverberation chamber. If a radiated immunity test using such a low-frequency electric field is performed inside a reverberation chamber, the dimensions of the reverberation chamber would be approximately 10 km. A reverberation chamber with such dimensions is undesirable because it limits the flexibility of its installation location. For this reason, in recent years, there has been a demand for reverberation chambers that are equipped with equipment capable of performing radiated immunity testing using low-frequency bands and are large enough to accommodate electrical devices.

[0006] A device known as a transmission line system (TLS) is a device capable of performing radiated immunity testing using low frequency bands in a reverberation chamber. Examples of transmission line systems include devices that apply an electric field to electronic equipment from antennas such as a TEM (Transverse Electro-Magnetic) plate antenna or a stripline. For ease of explanation, this specification will refer to the method of performing radiated immunity testing using a transmission line system as the transmission line system method.

[0007] Here, a known mounting table on which a test specimen to be subjected to radiation immunity testing using an anechoic chamber is placed includes a top plate, legs provided on the bottom side of the top plate to support the top plate, a ground plate made of a metallic material provided on the surface of the top plate, and a connecting arm member that connects the ground plate to the metal wall plate of the anechoic chamber, the top plate having a housing section that extends from the inner part to the outer edge and has an opening at the outer edge to house the connecting arm member so that it can move back and forth, the connecting arm member having an arm section that extends along the housing section, is movably attached within the housing section, and is connected to the ground plate, and a connecting section that is provided at the tip of the arm section and protrudes from the housing section to be connected to the metal wall plate of the anechoic chamber (see Patent Document 1). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-127870 Summary of the Invention [Problem to be solved by the invention]

[0009] However, a method of using a mounting table such as that described in Patent Document 1 in a radiation immunity test using a low frequency band in a reverberation box has not been established up to now.

[0010] The present disclosure has been made in consideration of the above circumstances, and aims to provide an electromagnetic wave testing device and an electromagnetic wave testing method that can improve the uniformity of the electric field strength on a grounded metal mounting table when conducting a radiation immunity test using a low frequency band inside a reverberation box. [Means for solving the problem]

[0011] One aspect of the present disclosure is an electromagnetic wave testing device comprising: a reflection box; an antenna installed within the reflection box and radiating electromagnetic waves at a frequency lower than the resonant frequency of the reflection box; a flat-plate-shaped mounting table having a conductive mounting surface including a first side and a second side opposite the first side on which a test piece is placed; a first grounding section electrically connecting an object at ground potential to the first side; and a second grounding section electrically connecting the object to the second side.

[0012] Another aspect of the present disclosure is an electromagnetic wave testing device comprising: a reflection box; a flat-plate-shaped mounting table having a conductive mounting surface including a first side and a second side opposite the first side on which a test piece is placed; a first grounding portion electrically connecting an object at ground potential to the first side; and a second grounding portion electrically connecting the object to the second side, wherein an antenna is installed in the reflection box to radiate electromagnetic waves at a frequency lower than the resonant frequency of the reflection box.

[0013] Furthermore, one aspect of the present disclosure is an electromagnetic wave testing method using an electromagnetic wave testing device including a reflection box, an antenna installed in the reflection box and radiating electromagnetic waves at a frequency lower than the resonant frequency of the reflection box, and a flat-plate-shaped mounting table having a conductive mounting surface on which a test piece is placed, the mounting surface including a first side and a second side opposite the first side, wherein an object at ground potential and the first side are electrically connected by a first grounding part, and the object and the second side are electrically connected by a second grounding part. [Effects of the Invention]

[0014] According to the present disclosure, when a radiation immunity test using a low frequency band is performed in a reverberation box, the uniformity of the electric field strength on a grounded metal mounting table can be improved. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing an example of the configuration of an electromagnetic wave test apparatus 1 according to an embodiment. [Figure 2] FIG. 2 is an enlarged perspective view of the mounting table 12 shown in FIG. [Figure 3] 1 is an enlarged perspective view of the mounting table 12 to which the first grounding portion ST1 and the second grounding portion ST2 are connected. [Figure 4] 10 is a diagram illustrating an example of a frequency spectrum of an electric field intensity detected by an electric field sensor installed near the center of the placement surface. FIG. [Figure 5] This figure shows an example of the results of a finite element analysis of the distribution of 27.5 MHz electric field strength inside the reflector box 10 when the reflector box 10 without the mounting table 12 installed is viewed in the negative direction of the Z axis. [Figure 6] This figure shows an example of the results of a finite element analysis of the distribution of the electric field strength at 27.5 MHz inside the reflector box 10 when the reflector box 10 without the mounting table 12 installed is viewed in the negative direction of the Y axis. [Figure 7]This figure shows an example of the results of an analysis using the finite element method of the distribution of the electric field strength at 27.5 MHz within the reflector box 10, when the reflector box 10 is installed with the mounting table 12 to which the first grounding portion ST1 is connected, as shown in Figure 2, and is viewed in the negative direction of the Z axis. [Figure 8] This figure shows an example of the results of an analysis using the finite element method of the distribution of the electric field strength at 27.5 MHz within the reflector box 10, when the reflector box 10 is installed with the mounting table 12 to which the first grounding portion ST1 is connected, as shown in Figure 2, and is viewed in the negative direction of the Y axis. [Figure 9] This figure shows an example of the results of an analysis using the finite element method of the distribution of the electric field strength at 27.5 MHz within the reflector box 10, when the reflector box 10 is installed with a mounting table 12 to which the first grounding portion ST1 and the second grounding portion ST2 are connected, as shown in Figure 3, and is viewed in the negative direction of the Z axis. [Figure 10] This figure shows an example of the results of an analysis using the finite element method of the distribution of the electric field strength at 27.5 MHz inside the reflector box 10, when the reflector box 10 is installed with a mounting table 12 to which the first grounding portion ST1 and the second grounding portion ST2 are connected, as shown in Figure 3, and is viewed in the negative direction of the Y axis. [Figure 11] FIG. 10 is a diagram showing an example of a table for comparing the measurement results of the reference field strength with the measurement results of the first to third field strengths. [Figure 12] FIG. 12 is a diagram showing an example of a graph in which the frequency spectrum shown in FIG. 11 is plotted. [Figure 13] FIG. 10 is a diagram showing an example of a table for comparing the measurement results of the reference field intensity with the measurement results of the fourth to sixth field intensities. [Figure 14] FIG. 14 is a diagram showing an example of a graph in which the frequency spectrum shown in FIG. 13 is plotted. [Figure 15] FIG. 10 is a diagram showing an example of a table for comparing the measurement results of the reference field strength with the measurement results of the seventh field strength and the eighth field strength. [Figure 16] FIG. 16 is a diagram showing an example of a graph in which the frequency spectrum shown in FIG. 15 is plotted. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Embodiment> Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. For simplicity, the following description will be given assuming that there is no or almost no potential difference between multiple components having ground potential. In the following description, the term "electric field" may be interpreted as either a magnetic field or an electromagnetic field. For ease of explanation, the intensity of the electric field will be referred to simply as "electric field intensity." The three-dimensional coordinate system TC shown in some of the drawings referenced in this specification is a three-dimensional Cartesian coordinate system indicating the directions in each drawing. For ease of explanation, the X-axis in the three-dimensional coordinate system TC will be referred to simply as the X-axis. For ease of explanation, the Y-axis in the three-dimensional coordinate system TC will be referred to simply as the Y-axis. For ease of explanation, the Z-axis in the three-dimensional coordinate system TC will be referred to simply as the Z-axis. For example, the following description will assume that the negative direction of the Z-axis in each drawing of the three-dimensional coordinate system TC is aligned with the vertical direction, i.e., the direction of gravity. Therefore, for convenience of explanation, the positive direction of the Z axis will be referred to as the up or upward direction, and the negative direction of the Z axis will be referred to as the down or downward direction.

[0017] <Configuration of electromagnetic wave test equipment> First, the configuration of an electromagnetic wave test apparatus 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing an example of the configuration of an electromagnetic wave test apparatus 1 according to an embodiment.

[0018] The electromagnetic wave test device 1 is a device that performs a radiated immunity test on a test subject TM, which is an electronic device that is the target of the radiated immunity test. The radiated immunity test is a test in which a uniform, high-intensity electric field is applied to the test subject TM to check whether the test subject TM operates normally. As an example, the following describes a case in which the test subject TM is an electronic device that has an overall rectangular parallelepiped shape, as shown in FIG. 1. Note that the electronic device that is the target of the radiated immunity test as the test subject TM may be any device that is electrically controlled. For this reason, the test subject TM may be an electrically controlled device such as a multi-function mobile phone terminal (smartphone), a mobile phone terminal, a drive recorder, or various computers, but is not limited to these.

[0019] The electromagnetic wave test equipment 1 also performs a radiated immunity test using a hybrid method. The hybrid method is a method of performing a radiated immunity test by combining the reverberation chamber method and the transmission line system (TLS) method. The reverberation chamber method is a method of performing a radiated immunity test using a resonance phenomenon inside a reverberation chamber. The transmission line system method is a method of performing a radiated immunity test using a transmission line system. The transmission line system is a device that applies an electric field to an electronic device from an antenna such as a TEM (Transverse Electro-Magnetic) plate antenna or a stripline.

[0020] The electromagnetic wave test apparatus 1 includes a reflection box 10, an antenna 11, a mounting table 12, and an electromagnetic stirrer 13. The electromagnetic wave test apparatus 1 may not include the antenna 11. In this case, an external antenna 11 is installed in the electromagnetic wave test apparatus 1. The electromagnetic wave test apparatus 1 may not include the electromagnetic stirrer 13. In this case, an external electromagnetic stirrer 13 is installed in the electromagnetic wave test apparatus 1.

[0021] The reflective box 10 is, for example, a cavity resonator configured as a metal housing capable of accommodating a test specimen TM. In the following, as an example, a case will be described in which the reflective box 10 is a rectangular parallelepiped metal cavity resonator capable of accommodating a test specimen TM therein, as shown in FIG. 1 . The shape of the reflective box 10 may be other shapes capable of accommodating a test specimen TM instead of a rectangular parallelepiped shape. However, a rectangular parallelepiped shape is preferable for the shape of the reflective box 10, as this makes it easier to calculate the resonant frequency of the reflective box 10. In the following, for convenience of explanation, the lowest-order resonant frequency of the reflective box 10 will be referred to as the first resonant frequency. The reflective box 10 may be configured with a cavity resonator configured as a metal housing capable of accommodating a test specimen TM, an antenna 11, and an electromagnetic stirrer 13. In this case, the electromagnetic wave testing apparatus 1 includes the reflective box 10 and a mounting table 12.

[0022] The antenna 11 radiates electromagnetic waves with a frequency lower than the first resonant frequency. The antenna 11 may be any antenna that can be used for TLS, such as a TEM (Transverse Electro-Magnetic) plate antenna, a stripline, or a septum. That is, the antenna 11 is installed inside the reflection box 10, and the electromagnetic wave test apparatus 1 functions as a TLS. The antenna 11 is also connected to an information processing device 2 installed outside the reflection box 10 via a communication cable. That is, the antenna 11 acquires an RF (Radio Frequency) signal from the information processing device 2 and radiates electromagnetic waves corresponding to the acquired RF signal. The electromagnetic wave test apparatus 1 may be configured to include the information processing device 2.

[0023] The mounting table 12 is a flat table having a conductive mounting surface on which the specimen TM is placed. The mounting table 12 may be entirely made of a conductor, or at least a portion of the portion other than the mounting surface may be non-conductive. The following describes, as an example, a case where the mounting table 12 is entirely made of metal, i.e., the entire mounting table 12 is made of a conductor. The mounting surface may be made of a conductor other than metal. The mounting surface of the mounting table 12 is grounded by a component not shown in FIG. 1 for simplification. Therefore, the potential of the mounting surface of the mounting table 12 is ground potential. For this reason, the mounting table 12 is sometimes referred to as a ground plane, a reference ground plane, or the like. The following describes, as an example, a case where the mounting surface is parallel to the floor of the reflective chamber 10. The following also describes, as an example, a case where the floor of the reflective chamber 10 is perpendicular to the Z-axis. The mounting surface may be non-parallel to the floor of the reflective chamber 10. The floor surface of the reflective box 10 may be configured to be oblique to the Z axis. The mounting base 12 is supported by a support (not shown in Fig. 1) so that the height of the mounting base 12 from the floor surface of the reflective box 10 is a predetermined height. The support is insulated from the floor surface of the reflective box 10. For example, the support is made of aluminum, and is insulated from the floor surface of the reflective box 10 by resin casters.

[0024] The mounting surface of the mounting base 12 includes a first side 121 and a second side 122 opposite to the first side 121. The first side 121 and the second side 122 are also sides that constitute the outer shape of the mounting base 12. The shape of the mounting base 12 may be any shape as long as it has a mounting surface that includes the first side 121 and the second side 122. In the following, as an example, a case will be described in which the shape of the mounting base 12 when viewed in a direction perpendicular to the mounting surface toward the floor surface of the reflective box 10 is a rectangle having the first side 121 and the second side 122 as long sides. That is, in this example, the shape of the mounting base 12 is a rectangular flat plate. In this example, the mounting surface is the upper surface of the mounting base 12. In the following, for convenience of explanation, the direction perpendicular to the mounting surface toward the floor surface of the reflective box 10 will be referred to as a first direction. In this example, the first direction coincides with the direction of gravity.

[0025] For example, in accordance with the international standard ISO 11452-2, the shape of the mounting table 12 is specified as a rectangular flat plate with long sides of 2000 mm or more, short sides of 1000 mm or more, and a thickness of 0.5 mm or more. It is also specified that the mounting table 12 must be made of copper, brass, or zinc-plated steel. However, these specifications are based on the ISO 11452-2 standard. The mounting table 12 according to this embodiment does not necessarily have to comply with these specifications. This is because ISO 11452-2 is an international standard for radiated immunity testing using an anechoic chamber, but is not an international standard for radiated immunity testing using the hybrid method. If an international standard for radiated immunity testing using the hybrid method is established, the mounting table 12 may be formed in a shape that complies with the established international standard.

[0026] FIG. 2 is an enlarged perspective view of the mounting table 12 shown in FIG. 1. Note that the support body described above is omitted from FIG. 2 to avoid cluttering the drawing. As shown in FIG. 2, a first grounding portion ST1 is provided on a first side 121 of the mounting table 12, electrically connecting the object at ground potential and the mounting table 12. In the example shown in FIG. 2, the object at ground potential is the floor surface of the reflective box 10. Note that instead of the floor surface of the reflective box 10, the object at ground potential may be a side wall surface of the reflective box 10 or a ceiling surface of the reflective box 10, or may be an object separate from the reflective box 10 as long as it is at ground potential.

[0027] In the example shown in FIG. 2, the first grounding section ST1 includes seven conductive first grounding members ST10 that electrically connect the floor surface of the reflective box 10 to the first side 121. Each of these seven first grounding members ST10 is, for example, a belt-shaped member whose short side has a predetermined first width and connects the floor surface to the first side 121 at the shortest distance. Note that the shape of some or all of the seven first grounding members ST10 may be other shapes instead of the belt shape. The number of first grounding members ST10 included in the first grounding section ST1 may be one, or two to six or eight or more. Therefore, the first width may be any width as long as it is equal to or less than the width of the first side 121 in the direction parallel to the Y-axis. In the example shown in FIG. 2, two adjacent first grounding members ST10 among the seven first grounding members ST10 are spaced apart from each other in the Y-axis direction. However, some or all of the two adjacent first ground contact members ST10 among these seven first ground contact members ST10 do not have to be spaced apart from each other in the direction.

[0028] In addition, the distance between each pair of adjacent first grounding members ST10 among the seven first grounding members ST10 is specified to not exceed 300 mm in accordance with ISO 11452-2. Furthermore, in this case, the maximum ratio between the height of each of the seven first grounding members ST10 in the direction parallel to the Z axis and the width of each of the seven first grounding members ST10 in the direction parallel to the Y axis is specified to be 7:1. However, as with the mounting table 12, each of the seven first grounding members ST10 does not necessarily have to comply with these specifications.

[0029] 2, the second side 122 of the mounting table 12 does not have a member that electrically connects the object at ground potential to the mounting table 12. However, the mounting table 12 may have a configuration in which the first ground portion ST1 is provided on the first side 121 and the second ground portion ST2 is provided on the second side 122, as shown in FIG.

[0030] 3 is an enlarged perspective view of the mounting table 12 to which the first grounding portion ST1 and the second grounding portion ST2 are connected. Note that, in FIG. 3 as well, the aforementioned support is omitted to avoid cluttering the drawing. Similar to the example shown in FIG. 2, the first grounding portion ST1 electrically connects the floor of the reflective box 10 and the mounting table 12 to a first side 121 of the mounting table 12 shown in FIG. 3. Meanwhile, the second side 122 of the mounting table 12 shown in FIG. 3 is provided with a second grounding portion ST2 electrically connects the floor of the reflective box 10 and the mounting table 12 to a second side. Note that, in the example shown in FIG. 3 as well, the floor of the reflective box 10 is an example of an object at ground potential.

[0031] The configuration of the first grounding portion ST1 shown in FIG. 3 is the same as that of the first grounding portion ST1 shown in FIG. 2. Therefore, the description of the first grounding portion ST1 is omitted in FIG. 3. On the other hand, the second grounding portion ST2 includes seven conductive second grounding members ST20 that electrically connect the floor surface of the reflective box 10 and the second side 122. Each of these seven second grounding members ST20 is, for example, a belt-shaped member whose short side has a predetermined second width and connects the floor surface and the second side 122 over the shortest distance. Note that the shape of some or all of the seven second grounding members ST20 may be other shapes instead of the belt-like shape. Furthermore, the number of second grounding members ST20 included in the second grounding portion ST2 may be one, or may be two to six or more, or may be eight or more. Therefore, the second width may be any width as long as it is equal to or less than the width of the second side 122 in the direction parallel to the Y axis. 3, two adjacent second grounding members ST20 among the seven second grounding members ST20 are spaced apart from each other in the direction. However, some or all of two adjacent second grounding members ST20 among the seven second grounding members ST20 do not have to be spaced apart from each other in the direction.

[0032] In addition, the distance between each pair of adjacent second grounding members ST20 among the seven second grounding members ST20 is also specified to not exceed 300 mm in accordance with ISO 11452-2. In this case, the maximum ratio between the height of each of the seven second grounding members ST20 in the direction parallel to the Z axis and the width of each of the seven second grounding members ST20 in the direction parallel to the Y axis is also specified to be 7:1. However, just like the mounting table 12 and the first grounding members ST10, each of the seven second grounding members ST20 does not necessarily have to comply with these specifications.

[0033] As described above, the mounting table 12 is grounded by the first grounding portion ST1, or by both the first grounding portion ST1 and the second grounding portion ST2. This allows the electromagnetic wave testing apparatus 1 to prevent the potential of the mounting table 12 from changing the results of the radiation immunity test.

[0034] The electromagnetic agitator 13 agitates the electromagnetic waves in the reflective chamber 10. This allows the reflective chamber 10 to reduce variations in the electric field strength within the reflective chamber 10. The electromagnetic agitator 13 may have any configuration as long as it is capable of agitating the electromagnetic waves in the reflective chamber 10. In the example shown in FIG. 1 , the electromagnetic agitator 13 includes a shaft, four flat, rectangular agitating blades arranged along the shaft, and a drive unit that rotates the shaft. In this case, the electromagnetic agitator 13 is controlled by the information processing device 2, and the electromagnetic waves in the reflective chamber 10 are agitated by the four agitating blades that rotate together with the shaft. Therefore, the information processing device 2 controls the drive unit to rotate the shaft. For this reason, the electromagnetic agitator 13 is connected to the information processing device 2 via a communication cable.

[0035] <Uniformity of electric field strength inside a reverberation chamber in radiated immunity testing using the hybrid method> The uniformity of the electric field strength inside the reflective box in the radiated immunity test using the hybrid method will be described below. When the mounting table 12 is installed inside the reflective box 10, it is often installed near the center of the reflective box 10. Therefore, the following will describe, as an example, the case where the mounting table 12 is installed near the center of the reflective box 10. The mounting table 12 may also be installed at a position other than near the center of the reflective box 10.

[0036] In the transmission line system method, the electric field strength inside the reverberation chamber 10 for a radiated immunity test is adjusted when only the antenna 11 and the electromagnetic stirrer 13 are installed inside the reverberation chamber 10. In other words, the adjustment is performed when the mounting base 12 is not installed inside the reverberation chamber 10. More specifically, the adjustment is performed so that the average value of the electric field strength at each of a plurality of predetermined measurement positions inside the reverberation chamber 10 without the mounting base 12 becomes the predetermined electric field strength to be applied to the test specimen TM in the radiated immunity test. Then, the mounting base 12 is installed inside the reverberation chamber 10 after the adjustment, and the test specimen TM is placed on the mounting base 12. Hereinafter, for convenience of explanation, the predetermined electric field strength to be applied to the test specimen TM in the radiated immunity test will be referred to as the test electric field strength. Also, for convenience of explanation, the average value after the adjustment will be referred to as the adjusted electric field strength.

[0037] FIG. 4 is a diagram illustrating a frequency spectrum of the electric field strength detected by an electric field sensor installed near the center of the mounting surface. FIG. 4 shows a frequency spectrum in the range of 20 MHz to 40 MHz. The horizontal axis of the graph shown in FIG. 4 represents frequency. The vertical axis of the graph represents electric field strength. A curve F11 plotted on the graph shows an example of the frequency spectrum of the electric field strength detected by the electric field sensor when the floor of the reflective box 10 and the mounting base 12 are connected by the first grounding portion ST1 and not by the second grounding portion ST2. In the example shown in FIG. 4, the curve F11 is indicated by the label "single-sided grounding." Furthermore, a curve F12 plotted on the graph shows an example of the frequency spectrum of the electric field strength detected by the electric field sensor when the floor of the reflective box 10 and the mounting base 12 are connected by both the first grounding portion ST1 and the second grounding portion ST2. In the example shown in FIG. 4, the curve F12 is indicated by the label "double-sided grounding."

[0038] In the example shown in FIG. 4, the dimensions of the reflective box 10 are 10.08 m × 6.36 m × 4.00 m, the first resonant frequency is 80 MHz, the TLS configured with the antenna 11 having a metal wire length of 3 m is placed at a height of 1.9 m, the long side of the mounting table 12 is 3 m, the short side of the mounting table 12 is 1.5 m, the height of the mounting table 12 from the floor surface of the reflective box 10 is 0.9 m, and the number of rotation steps of the electromagnetic stirrer 13 is 6. In this example, the power supplied to the antenna 11 is the same as the power supplied to the antenna 11 when the post-adjustment field strength is adjusted to 100 V / m. In this example, when the first grounding portion ST1 is connected to the mounting table 12 and the second grounding portion ST2 is not connected to the mounting table 12, the distance between adjacent first grounding members ST10 is 300 mm. In addition, in this example, when both the first grounding portion ST1 and the second grounding portion ST2 are connected to the mounting table 12, the distance between adjacent first grounding members ST10 and the distance between adjacent second grounding members ST20 are both 300 mm. In addition, in this example, when the first grounding portion ST1 is connected to the mounting table 12 and the second grounding portion ST2 is not connected to the mounting table 12, the width of the first grounding member ST10 in the direction parallel to the Y-axis is 150 mm. In addition, in this example, when both the first grounding portion ST1 and the second grounding portion ST2 are connected to the mounting table 12, the width of the first grounding member ST10 in that direction and the width of the second grounding member ST20 in that direction are both 150 mm. Curve F11 and curve F12 shown in FIG. 3 are the results of extracting the frequency spectrum of the electric field strength in the range of 20 MHz to 40 MHz from the frequency spectrum of the electric field strength in the range of 10 kHz to 250 MHz.

[0039] Comparing curves F11 and F12, it can be seen that when the first grounding portion ST1 is connected to the mounting table 12 and the second grounding portion ST2 is not connected to the mounting table 12, the electric field intensity at a frequency of around 27.5 MHz is significantly reduced near the center of the mounting surface. In other words, comparing curves F11 and F12, it can be seen that when both the first grounding portion ST1 and the second grounding portion ST2 are connected to the mounting table 12, the reduction in electric field intensity near the center of the mounting surface is suppressed. For ease of explanation, the case where the first grounding portion ST1 is connected to the mounting table 12 and the second grounding portion ST2 is not connected to the mounting table 12 will be referred to as one-sided grounding. For ease of explanation, the case where both the first grounding portion ST1 and the second grounding portion ST2 are connected to the mounting table 12 will be referred to as two-sided grounding.

[0040] Naturally, the decrease in field strength near 27.5 MHz, as indicated by curve F11, can be corrected by amplifying the power supplied to the antenna 11. Therefore, even without the second grounding part ST2, the electromagnetic wave test equipment 1 can adequately perform a radiated immunity test using the hybrid method. However, the field strength at 27.5 MHz indicated by curve F12 is approximately nine times that indicated by curve F11. To correct this nine-fold increase in field strength, the power supplied to the antenna 11 must be increased by 81 times. The cost of introducing a power amplifier to perform such a correction is extremely high. For these reasons, it is desirable for the electromagnetic wave test equipment 1 to include the second grounding part ST2.

[0041] FIG. 5 shows an example of the results of a finite element method analysis of the distribution of 27.5 MHz electric field strength within the reflector box 10 when the reflector box 10 is viewed in the negative direction of the Z axis without the mounting base 12. FIG. 6 shows an example of the results of a finite element method analysis of the distribution of 27.5 MHz electric field strength within the reflector box 10 when the reflector box 10 is viewed in the negative direction of the Y axis without the mounting base 12. In FIGS. 5 and 6, the intensity of the hatching indicates the strength of the electric field strength. Specifically, in FIGS. 5 and 6, the electric field strength in the lightly hatched area is weaker than the electric field strength in the darkly hatched area. As shown in FIGS. 5 and 6, the electric field strength variation is small within the reflector box 10 when the mounting base 12 is not installed.

[0042] On the other hand, FIG. 7 shows an example of the results of a finite element method analysis of the distribution of the electric field strength at 27.5 MHz inside the reflector chamber 10, when the reflector chamber 10 is equipped with a one-side-grounded mounting table 12 as shown in FIG. 2 and viewed in the negative direction of the Z axis. FIG. 8 shows an example of the results of a finite element method analysis of the distribution of the electric field strength at 27.5 MHz inside the reflector chamber 10, when the reflector chamber 10 is equipped with a one-side-grounded mounting table 12 as shown in FIG. 2 and viewed in the negative direction of the Y axis. Note that in FIG. 8, the mounting table 12 and the support are depicted as a single rectangular object to avoid cluttering the illustration. In FIGS. 7 and 8, the intensity of the electric field strength is represented by the shade of hatching. Specifically, in FIGS. 7 and 8, the electric field strength in the lightly hatched areas is weaker than the electric field strength in the darkly hatched areas. As shown in Figures 7 and 8, in a reflector box 10 in which a one-side-grounded mounting table 12 is installed, the variation in electric field strength is greater than when the mounting table 12 is not installed in the reflector box 10. Specifically, in a reflector box 10 in which a one-side-grounded mounting table 12 is installed, the electric field strength near the center of the mounting surface is extremely lower than the electric field strength in other areas. However, as shown in Figures 9 and 10, in a reflector box 10 in which a double-side-grounded mounting table 12 is installed, the degree of decrease in electric field strength near the center of the mounting surface is mitigated compared to a reflector box 10 in which a one-side-grounded mounting table 12 is installed.

[0043] FIG. 9 shows an example of the results of a finite element method analysis of the distribution of the electric field strength at 27.5 MHz within the reflector chamber 10, when the reflector chamber 10 is equipped with the double-grounded mounting table 12 shown in FIG. 3 and viewed in the negative direction of the Z axis. FIG. 10 shows an example of the results of a finite element method analysis of the distribution of the electric field strength at 27.5 MHz within the reflector chamber 10, when the reflector chamber 10 is equipped with the double-grounded mounting table 12 shown in FIG. 3 and viewed in the negative direction of the Y axis. Note that in FIG. 10 as well, the mounting table 12 and the support are depicted as a single rectangular object to avoid cluttering the illustration. In FIGS. 9 and 10, the intensity of the electric field strength is represented by the shade of hatching. Specifically, in FIGS. 9 and 10, the electric field strength in the lightly hatched areas is weaker than the electric field strength in the darkly hatched areas. As shown in Figures 9 and 10, in a reverberation chamber 10 equipped with a double-grounded mounting table 12, the degree of decrease in electric field strength near the center of the mounting surface is less severe than in a reverberation chamber 10 equipped with a single-grounded mounting table 12. This result is consistent with the graph shown in Figure 3. In other words, in a radiated immunity test using the hybrid method, the electromagnetic wave test apparatus 1 can reduce the variation in electric field strength on the mounting table 12 by providing a double-grounded mounting table 12. In other words, by grounding the mounting table 12 in the reverberation chamber 10 with double grounding, the electromagnetic wave test apparatus 1 can improve the uniformity of the electric field strength on the mounting table 12. This is useful because it helps prevent the results of the radiated immunity test from being underestimated.

[0044] <Connection of the first grounding portion and the second grounding portion to the mounting table> In the analyses shown in FIGS. 9 and 10 , the width of the first ground member ST10 in the direction parallel to the Y-axis and the width of the second ground member ST20 in the same direction were both set to 150 mm. Furthermore, in the analyses, the lengths of the long sides of the mounting table 12, i.e., the lengths of the first side 121 and the second side 122, were set to 3 m. Furthermore, in the analyses, the distance between adjacent first ground members ST10 and the distance between adjacent second ground members ST20 were both set to 300 mm. That is, in the analyses, the mounting table 12 was grounded by double-side grounding, and the first ground members ST10 were spaced apart, and the second ground members ST20 were also spaced apart. However, the manner in which the first ground members ST10 and the second ground members ST20 are connected to the mounting table 12 is not limited to this. Therefore, here, specific examples of the manner in which the first ground members ST10 and the second ground members ST20 are connected to the mounting table 12 described in this embodiment will be described. In the following, for the sake of convenience, specific examples of the connection modes of the first grounding member and the second grounding member to the mounting table 12 described in this embodiment will be referred to as the first to ninth connection modes, respectively.

[0045] In the first connection mode, one first ground member ST10, whose width in the direction parallel to the Y-axis is the same as the length of the first side 121, is connected to the first side 121, and one second ground member ST20, whose width in the same direction is the same as the length of the second side 122, is connected to the second side 122. For ease of explanation, the first ground member ST10 in the first connection mode will be referred to as the first ground member ST11, and the second ground member ST20 in the first connection mode will be referred to as the second ground member ST21. In addition, in the first connection mode, the first ground member ST11 is connected from the first side 121 to the floor surface of the reflective box 10 at the shortest distance. In addition, in the first connection mode, the second ground member ST21 is connected from the second side 122 to the floor surface at the shortest distance. Furthermore, in the first connection mode, a rectangular virtual first surface having an area on the floor surface where the first side 121 is projected onto the floor surface in the first direction and the first side 121 as two opposing sides is entirely filled with the first ground member ST11. Furthermore, in the first connection mode, a rectangular virtual second surface having an area on the floor surface where the second side 122 is projected onto the floor surface in the first direction and the second side 122 as two opposing sides is entirely filled with the second ground member ST21. That is, in the first connection mode, when the mounting table 12 is viewed in the second direction from the first side 121 to the second side 122, which is a direction perpendicular to the first surface, the first ground member ST11 completely covers the first surface except for errors due to distortion, deformation, etc. of the first ground member ST11. In the first connection mode, when the mounting table 12 is viewed in a third direction perpendicular to the second surface, from the second side 122 toward the first side 121, the second ground member ST21 completely covers the second surface, excluding errors due to distortion, deformation, etc. of the second ground member ST21. The first connection mode is illustrated in FIG. 11, which will be described later, as a diagram showing an analytical model of the first connection mode. The analytical model of the first connection mode is an analytical model used to analyze the electric field intensity near the center of the mounting surface when the first ground portion ST1 and the second ground portion ST2 are each connected to the mounting table 12 in the first connection mode.

[0046] In the second connection mode, one first ground member ST10, whose width in the direction parallel to the Y-axis is 50% of the length of the first side 121, is connected to the first side 121, and one second ground member ST20, whose width in the same direction is 50% of the length of the second side 122, is connected to the second side 122. For ease of explanation, the first ground member ST10 in the second connection mode will be referred to as the first ground member ST12, and the second ground member ST20 in the second connection mode will be referred to as the second ground member ST22. In the second connection mode, the first ground member ST12 is connected from the first side 121 to the floor surface of the reflective box 10 at the shortest distance. In the second connection mode, the second ground member ST22 is connected from the second side 122 to the floor surface at the shortest distance. In the second connection mode, the first ground member ST12 is connected to the first side 121 so that the midpoint of the first side 121 coincides with the midpoint in that direction of a first end portion of the first ground member ST12 that is connected to the first side 121. In the second connection mode, the second ground member ST22 is connected to the second side 122 so that the midpoint of the second side 122 coincides with the midpoint in that direction of a second end portion of the second ground member ST22 that is connected to the second side 122. In the second connection mode, 50% of the first surface is covered by the first ground member ST12. In the second connection mode, 50% of the second surface is covered by the second ground member ST22. That is, in the second connection mode, when the mounting table 12 is viewed in the second direction, the first ground member ST12 covers 50% of the first surface, excluding errors due to distortion, deformation, etc. of the first ground member ST12. Also, in the second connection mode, when the mounting table 12 is viewed in the third direction, the second ground member ST22 covers 50% of the second surface, excluding errors due to distortion, deformation, etc. of the second ground member ST22. The second connection mode is illustrated in FIG. 11, which will be described later, as a diagram showing an analytical model of the second connection mode. The analytical model of the second connection mode is an analytical model used to analyze the electric field intensity near the center of the mounting surface when the first ground portion ST1 and the second ground portion ST2 are each connected to the mounting table 12 in the second connection mode.

[0047] In the third connection mode, one first ground member ST10, whose width in the direction parallel to the Y-axis is 25% of the length of the first side 121, is connected to the first side 121, and one second ground member ST20, whose width in the same direction is 25% of the length of the second side 122, is connected to the second side 122. For ease of explanation, the first ground member ST10 in the third connection mode will be referred to as the first ground member ST13, and the second ground member ST20 in the third connection mode will be referred to as the second ground member ST23. In addition, in the third connection mode, the first ground member ST13 is connected from the first side 121 to the floor surface of the reflective box 10 at the shortest distance. In addition, in the third connection mode, the second ground member ST23 is connected from the second side 122 to the floor surface at the shortest distance. In the third connection mode, the first ground member ST13 is connected to the first side 121 so that the midpoint of the first side 121 coincides with the midpoint of the first end in that direction. In the third connection mode, the second ground member ST23 is connected to the second side 122 so that the midpoint of the second side 122 coincides with the midpoint of the second end in that direction. In the third connection mode, 25% of the first surface is covered by the first ground member ST13. In the third connection mode, 25% of the second surface is covered by the second ground member ST23. That is, in the third connection mode, when the mounting table 12 is viewed in the second direction, the first ground member ST13 covers 25% of the first surface, excluding errors due to distortion, deformation, etc. of the first ground member ST13. In the third connection mode, when the mounting table 12 is viewed in the third direction, the second grounding member ST23 covers 25% of the second surface, excluding errors due to distortion, deformation, etc. of the second grounding member ST23. The third connection mode is illustrated as an analytical model of the third connection mode in Fig. 11, which will be described later. The analytical model of the third connection mode is an analytical model used to analyze the electric field intensity near the center of the mounting surface when the first grounding portion ST1 and the second grounding portion ST2 are each connected to the mounting table 12 in the third connection mode.

[0048] In the fourth connection mode, six first ground members ST10 each having a width of 273 mm in the direction parallel to the Y-axis are connected to the first side 121, and six second ground members ST20 each having a width of 273 mm in the same direction are connected to the second side 122. For ease of explanation, the first ground members ST10 in the fourth connection mode will be referred to as first ground members ST14, and the second ground members ST20 in the fourth connection mode will be referred to as second ground members ST24. In addition, in the fourth connection mode, each of the six first ground members ST14 is connected to the floor surface of the reflective box 10 at the shortest distance from the first side 121. In addition, in the fourth connection mode, each of the six second ground members ST24 is connected to the floor surface at the shortest distance from the second side 122. In the fourth connection mode, adjacent first ground members ST14 among the six first ground members ST14 are spaced apart by 273 mm in the X-axis direction. In the fourth connection mode, adjacent second ground members ST24 among the six second ground members ST24 are spaced apart by 273 mm in the X-axis direction. In the fourth connection mode, the end on the positive side of the first ground member ST14 that is closest to the positive side of the X-axis among the six first ground members ST14 is connected to the end on the positive side of the first side 121. In the fourth connection mode, the end on the positive side of the second ground member ST24 that is closest to the positive side of the X-axis among the six second ground members ST24 is connected to the end on the positive side of the second side 122. The fourth connection mode is illustrated in FIG. 13, which will be described later, as a diagram showing an analysis model of the fourth connection mode. The analytical model of the fourth connection mode is an analytical model used to analyze the electric field strength near the center of the mounting surface when the first grounding portion ST1 and the second grounding portion ST2 are each connected to the mounting table 12 in the fourth connection mode.

[0049] In the fifth connection mode, three first ground members ST10 each having a width of 273 mm in the direction parallel to the Y-axis are connected to the first side 121, and three second ground members ST20 each having a width of 273 mm in the same direction are connected to the second side 122. For ease of explanation, the first ground members ST10 in the fifth connection mode will be referred to as first ground members ST15, and the second ground members ST20 in the second connection mode will be referred to as second ground members ST25. In addition, in the fifth connection mode, each of the three first ground members ST15 is connected to the floor surface of the reflective box 10 at the shortest distance from the first side 121. In addition, in the fifth connection mode, each of the three second ground members ST25 is connected to the floor surface at the shortest distance from the second side 122. In the fifth connection mode, adjacent first ground members ST15 of the three first ground members ST15 are spaced apart by 546 mm in the X-axis direction. In the fifth connection mode, adjacent second ground members ST25 of the three second ground members ST25 are spaced apart by 546 mm in the X-axis direction. In the fifth connection mode, the end of the first ground member ST15 furthest along the positive direction of the X-axis of the three first ground members ST15 is spaced apart by 546 mm in the X-axis direction from the end of the first side 121. In the fifth connection mode, the end of the second ground member ST25 furthest along the positive direction of the X-axis of the three second ground members ST25 is spaced apart by 546 mm in the X-axis direction from the end of the second side 122. The fifth connection mode is illustrated in FIG. 13, which will be described later, as a diagram showing an analysis model of the fifth connection mode. The analytical model of the fifth connection mode is an analytical model used to analyze the electric field strength near the center of the mounting surface when the first grounding portion ST1 and the second grounding portion ST2 are each connected to the mounting table 12 in the fifth connection mode.

[0050] In the sixth connection mode, three first ground members ST10 each having a width of 273 mm in the direction parallel to the Y-axis are connected to the first side 121, and three second ground members ST20 each having a width of 273 mm in the same direction are connected to the second side 122. For ease of explanation, the first ground members ST10 in the sixth connection mode will be referred to as first ground members ST16, and the second ground members ST20 in the sixth connection mode will be referred to as second ground members ST26. In addition, in the sixth connection mode, each of the three first ground members ST16 is connected from the first side 121 to the floor surface of the reflective box 10 at the shortest distance. In addition, in the sixth connection mode, each of the three second ground members ST26 is connected from the second side 122 to the floor surface at the shortest distance. In the sixth connection mode, adjacent first ground members ST16 among the three first ground members ST16 are spaced apart by 273 mm in the X-axis direction. In the sixth connection mode, adjacent second ground members ST26 among the three second ground members ST26 are spaced apart by 273 mm in the X-axis direction. In the sixth connection mode, the end on the positive side of the first ground member ST16 that is furthest along the positive direction of the X-axis among the three first ground members ST16 is connected to the end on the positive side of the first side 121. In the sixth connection mode, the end on the negative side of the second ground member ST26 that is furthest along the negative direction of the X-axis among the three second ground members ST26 is connected to the end on the negative side of the second side 122. The sixth connection mode is illustrated in FIG. 13, which will be described later, as a diagram showing an analysis model of the sixth connection mode. The analytical model of the sixth connection mode is an analytical model used to analyze the electric field strength near the center of the mounting surface when the first grounding portion ST1 and the second grounding portion ST2 are each connected to the mounting table 12 in the sixth connection mode.

[0051] In the seventh connection mode, three first ground members ST10 each having a width of 300 mm in the direction parallel to the Y-axis are connected to the first side 121, and three second ground members ST20 each having a width of 300 mm in the same direction are connected to the second side 122. For ease of explanation, the first ground members ST10 in the seventh connection mode will be referred to as first ground members ST17, and the second ground members ST20 in the seventh connection mode will be referred to as second ground members ST27. In addition, in the seventh connection mode, each of the three first ground members ST17 is connected from the first side 121 to the floor surface of the reflective box 10 at the shortest distance. In addition, in the seventh connection mode, each of the three second ground members ST27 is connected from the second side 122 to the floor surface at the shortest distance. In the seventh connection mode, adjacent first ground members ST17 among the three first ground members ST17 are spaced 600 mm apart in the X-axis direction. In the seventh connection mode, adjacent second ground members ST27 among the three second ground members ST27 are spaced 600 mm apart in the X-axis direction. In the seventh connection mode, the end on the positive side of the first ground member ST17 that is closest to the positive side of the X-axis among the three first ground members ST17 is spaced 600 mm apart in the X-axis direction from the end on the positive side of the first side 121. In the seventh connection mode, the end on the positive side of the second ground member ST27 that is closest to the positive side of the X-axis among the three second ground members ST27 is spaced 600 mm apart in the X-axis direction from the end on the positive side of the second side 122. The seventh connection mode is illustrated in FIG. 15, which will be described later, as a diagram showing an analysis model of the seventh connection mode. The analytical model of the seventh connection mode is an analytical model used to analyze the electric field strength near the center of the mounting surface when the first grounding portion ST1 and the second grounding portion ST2 are each connected to the mounting table 12 in the seventh connection mode.

[0052] In the eighth connection mode, three first ground members ST10 each having a width of 300 mm in the direction parallel to the Y-axis are connected to the first side 121, and three second ground members ST20 each having a width of 300 mm in the same direction are connected to the second side 122. For ease of explanation, the first ground members ST10 in the eighth connection mode will be referred to as first ground members ST18, and the second ground members ST20 in the eighth connection mode will be referred to as second ground members ST28. In addition, in the eighth connection mode, each of the three first ground members ST18 is connected from the first side 121 to the floor surface of the reflective box 10 at the shortest distance. In addition, in the eighth connection mode, each of the three second ground members ST28 is connected from the second side 122 to the floor surface at the shortest distance. In the eighth connection mode, adjacent first ground members ST18 of the three first ground members ST18 are spaced apart by 600 mm in the X-axis direction. In the eighth connection mode, adjacent second ground members ST28 of the three second ground members ST28 are spaced apart by 600 mm in the X-axis direction. In the eighth connection mode, each of the three first ground members ST18 is spaced apart by 300 mm from the first side 121 in the second direction. In the eighth connection mode, each of the three second ground members ST28 is spaced apart by 300 mm from the second side 122 in the third direction. In the eighth connection mode, the end of the first ground member ST18 that is furthest along the positive side of the X-axis among the three first ground members ST18 is spaced apart by 600 mm in the negative direction of the X-axis from the end of the mounting table 12 that is on the positive side. In the eighth connection mode, the end portion of the second grounding member ST28 that is furthest along the positive side of the X-axis among the three second grounding members ST28 is spaced 600 mm in the negative direction of the X-axis from the end portion of the mounting table 12 that is furthest along the positive side. The eighth connection mode is illustrated in FIG. 15, which will be described later, as a diagram showing an analytical model of the eighth connection mode. The analytical model of the eighth connection mode is an analytical model used to analyze the electric field intensity near the center of the mounting surface when the first grounding portion ST1 and the second grounding portion ST2 are each connected to the mounting table 12 in the eighth connection mode.

[0053] <Analysis results of electric field strength inside the reverberation box for each connection type> The analysis results of the first to eighth electric field intensities will be described below. In this embodiment, the nth electric field intensity refers to the electric field intensity inside the reflector box 10 in the nth connection mode. Here, n is any integer from 1 to 9. In this embodiment, the electric field intensity inside the reflector box 10 in the nth connection mode refers to the electric field intensity near the center of the mounting surface when the first grounding portion ST1 and the second grounding portion ST2 are each connected to the mounting table 12 in the nth connection mode. In this embodiment, the analysis result of the nth electric field intensity refers to the frequency spectrum of the nth electric field intensity obtained as a result of analysis by the finite element method using the analytical model of the nth connection mode.

[0054] FIG. 11 is a diagram showing an example of a table comparing the analysis results of the reference field strength with the analysis results of the first to third field strengths. Here, the reference field strength refers to the field strength inside the reflector box 10 in the reference connection mode. The reference connection mode is a connection mode in which the first ground member ST11 is connected to the first side 121 of the mounting table 12, as in the first connection mode, but unlike the first connection mode, the second ground member ST21 is not connected to the second side 122 of the mounting table 12. That is, in the reference connection mode, the electromagnetic wave test apparatus 1 does not include the second ground portion ST2. In this embodiment, the field strength inside the reflector box 10 in the reference connection mode refers to the field strength near the center of the mounting surface when the first ground portion ST1 is connected to the mounting table 12 in the reference connection mode. In this embodiment, the analysis result of the reference field strength refers to the frequency spectrum of the reference field strength obtained as a result of analysis by the finite element method using the analytical model of the reference connection mode shown in FIG. 11.

[0055] Fig. 11 shows a table illustrating an example of the analysis results for the reference field strength, the first field strength, the second field strength, and the third field strength. The frequency band of the frequency spectrum shown in Fig. 11 is 20 MHz to 30 MHz, and the interval between frequencies is 0.5 MHz. Fig. 12 shows an example of a graph plotting the frequency spectrum shown in Fig. 11.

[0056] As shown in FIG. 12, the first to third electric field intensities all decrease around 27.5 MHz. However, the first to third electric field intensities are all stronger than the reference electric field intensity around 27.5 MHz. This indicates that the first to third connection modes each suppress the decrease in electric field intensity near the center of the mounting surface of the mounting table 12 compared to the reference connection mode. The first electric field intensity around 27.5 MHz is substantially the same as the second electric field intensity around 27.5 MHz. The first and second electric field intensities around 27.5 MHz are stronger than the third electric field intensity around 27.5 MHz. The proportion of the first surface covered by the first grounding portion ST1 when the mounting table 12 is grounded in the first connection mode is greater than the proportion of the first surface covered by the first grounding portion ST1 when the mounting table 12 is grounded in the second connection mode. The same applies to the proportion of the second surface covered by the second grounding portion ST2. Furthermore, when the mounting table 12 is grounded in the second connection mode, the proportion of the first surface covered by the first grounding portion ST1 is greater than the proportion of the first surface covered by the first grounding portion ST1 when the mounting table 12 is grounded in the third connection mode. The same applies to the proportion of the second surface covered by the second grounding portion ST2. In light of these facts, it can be seen that, when electromagnetic waves are radiated from the antenna 11, the reduction in electric field strength around 27.5 MHz inside the reflective chamber 10 tends to be suppressed as the area of ​​the first surface covered by the first grounding portion ST1 increases. However, by comparing the frequency spectra shown in FIG. 12, it can be seen that when the proportion of the first surface covered by the first grounding portion ST1 exceeds 50%, the effect of suppressing the reduction in electric field strength around 27.5 MHz decreases.

[0057] For simplicity, illustrations are omitted. For example, when the first grounding portion ST1 is connected to the first side 121 so as to cover a certain percentage of the first surface, the effect of reducing the electric field intensity obtained by covering the first surface with a plurality of first grounding members ST10 at that percentage is substantially the same as the effect of covering the first surface with a single first grounding member ST10 at that percentage. The same applies to the second surface. Therefore, when the mounting table 12 is grounded using the first connection mode, the first surface may be covered by a plurality of first grounding members. In addition, in this case, the second surface may be covered by a plurality of second grounding members. In either of these cases, the frequency spectrum of the first electric field intensity is substantially the same as the frequency spectrum of the first electric field intensity shown in FIG. 12. These facts are also true when the mounting table 12 is grounded using the second connection mode and when the mounting table 12 is grounded using the third connection mode.

[0058] Next, FIG. 13 is a diagram showing an example of a table for comparing the analysis result of the reference field intensity with the analysis results of each of the fourth to sixth field intensities.

[0059] Fig. 13 shows a table illustrating an example of the analysis results for the reference field strength, the fourth field strength, the fifth field strength, and the sixth field strength. However, the frequency band of the frequency spectrum shown in Fig. 13 is also 20 MHz to 30 MHz, and the interval between frequencies is also 0.5 MHz. Fig. 14 shows an example of a graph plotting the frequency spectrum shown in Fig. 13.

[0060] As shown in FIG. 14, the fourth to sixth electric field intensities all decrease near 27.5 MHz. However, the fourth to sixth electric field intensities are all stronger than the reference electric field intensity at 27.5 MHz. This indicates that the fourth to sixth connection modes each suppress the decrease in electric field intensity near the center of the mounting surface of the mounting table 12 compared to the reference connection mode. The fifth electric field intensity at 27.5 MHz is stronger than the fourth electric field intensity at 27.5 MHz. The fourth electric field intensity at 27.5 MHz is stronger than the sixth electric field intensity at 27.5 MHz. The proportion of the first surface covered by the first grounding portion ST1 when the mounting table 12 is grounded in the fourth connection mode is greater than the proportion of the first surface covered by the first grounding portion ST1 when the mounting table 12 is grounded in the fifth connection mode. The same applies to the proportion of the second surface covered by the second grounding portion ST2. Furthermore, when the mounting table 12 is grounded using the fifth connection mode, the proportion of the first surface covered by the first grounding portion ST1 is the same as the proportion of the first surface covered by the first grounding portion ST1 when the mounting table 12 is grounded using the sixth connection mode. The same is true for the proportion of the second surface covered by the second grounding portion ST2. However, in the fifth connection mode, each of the first grounding members of the first grounding portion ST1 faces one of the second grounding members of the second grounding portion ST2 without overlapping with the other, whereas in the sixth connection mode, each of the first grounding members of the first grounding portion ST1 does not face one of the second grounding members of the second grounding portion ST2. In light of these facts, it can be seen that when electromagnetic waves are radiated from the antenna 11, the reduction in electric field intensity around 27.5 MHz inside the reflector box 10 tends to be suppressed as the area of ​​the first surface covered by the first grounding portion ST1 increases, even if the first grounding members ST10 and the second grounding members ST20 are spaced apart from each other. However, by comparing the frequency spectra shown in Figure 12, it can be seen that when the first grounding member ST10 and the second grounding member ST20 are not opposed to each other, the effect of suppressing the decrease in electric field strength at 27.5 MHz is reduced.

[0061] Next, FIG. 15 is a diagram showing an example of a table for comparing the analysis results of the reference field intensity with the analysis results of the seventh field intensity and the eighth field intensity.

[0062] Fig. 15 shows a table illustrating an example of the analysis results for the reference field strength, the seventh field strength, and the eighth field strength. However, the frequency band of the frequency spectrum shown in Fig. 15 is also 20 MHz to 30 MHz, and the interval between frequencies is also 0.5 MHz. Fig. 16 shows an example of a graph plotting the frequency spectrum shown in Fig. 15.

[0063] As shown in FIG. 16 , both the seventh and eighth electric field intensities decrease near 27.5 MHz. However, both the seventh and eighth electric field intensities are stronger than the reference electric field intensity at 27.5 MHz. This indicates that the seventh and eighth connection modes each suppress the decrease in electric field intensity near the center of the mounting surface of the mounting table 12 compared to the reference connection mode. Furthermore, the seventh electric field intensity at 27.5 MHz is stronger than the eighth electric field intensity at 27.5 MHz. Unlike the seventh connection mode, when the mounting table 12 is viewed in the negative direction of the Z axis, the first ground portion ST1 in the eighth connection mode is located between the first side 121 and a center line located at the center between the first side 121 and the second side 122 among imaginary straight lines parallel to each of the first side 121 and the second side 122, and does not overlap with the first side 121. Furthermore, in the eighth connection mode, unlike the seventh connection mode, when the mounting table 12 is viewed in the negative direction of the Z axis, the second grounding portion ST2 is located between the center line and the second side 122, and does not overlap with the second side 122. In view of these, it can be seen that when electromagnetic waves are radiated from the antenna 11, inside the reflection box 10, the reduction in electric field strength around 27.5 MHz tends to decrease as the first grounding portion ST1 and the second grounding portion ST2 are connected to the mounting table 12 closer to the center line.

[0064] For simplicity of explanation, illustrations are omitted, but when viewing the mounting table 12 in the first direction, it is desirable that, assuming that the shortest distance between the center line and the first side 121 is 1, the shortest distance from the center line to the first ground portion ST1 is a distance that falls within a range of 0.6 or more and less than 1, and that, assuming that the shortest distance between the center line and the second side 122 is 1, the shortest distance from the center line to the second ground portion ST2 is a distance that falls within this range. This is because, according to analysis results, when these two shortest distances are within this range, it can be determined that the electric field strength in the vicinity of 27.5 MHz is sufficiently stronger than the reference electric field strength at 27.5 MHz.

[0065] As described above, the electromagnetic wave testing apparatus 1 according to the embodiment includes the reflective box 10, the antenna 11 that is installed in the reflective box 10 and that radiates electromagnetic waves at a frequency lower than the first resonant frequency, the mounting table 12, the first grounding part ST1, and the second grounding part ST2. As a result, the electromagnetic wave testing apparatus 1 can improve the uniformity of the electric field intensity on the grounded metallic mounting table 12 when performing a radiation immunity test using a low frequency band inside the reflective box 10, compared to when the second grounding part ST2 is not provided.

[0066] The above-described items may be combined in any manner.

[0067] <Additional Notes> [1] An electromagnetic wave testing device comprising: a reflection box; an antenna installed in the reflection box and radiating electromagnetic waves at a frequency lower than the resonant frequency of the reflection box; a flat-plate-shaped mounting table having a conductive mounting surface including a first side and a second side opposite the first side on which a test piece is placed; a first grounding part electrically connecting an object at ground potential to the first side; and a second grounding part electrically connecting the object to the second side. [2] The electromagnetic wave testing device described in [1], wherein the shape of the mounting stand when viewed in a direction perpendicular to the mounting surface toward the floor surface of the reflector box is a rectangle having the first side and the second side as long sides. [3] The electromagnetic wave testing device according to [1] or [2], wherein the object is a floor surface of the reflection box. [3] The electromagnetic wave testing device according to [1] or [2], wherein the object is a side wall surface of the reflector box. [5] The electromagnetic wave testing device according to any one of [1] to [4], wherein the first grounding section includes a plurality of first grounding members that electrically connect the object and the first side, and the second grounding section includes a plurality of second grounding members that electrically connect the object and the second side. [6] [5] An electromagnetic wave testing device as described in [5], wherein the number of the plurality of second grounding members is the same as the number of the plurality of first grounding members, and each of the plurality of first grounding members faces without overlapping any of the plurality of second grounding members in a direction parallel to the placement surface among directions perpendicular to each of the first side and the second side. [7] The electromagnetic wave testing device according to any one of [1] to [4], wherein the first grounding section includes one first grounding member that electrically connects the object and the first side, and the second grounding section includes one second grounding member that electrically connects the object and the second side. [8] The electromagnetic wave testing device according to any one of [1] to [7], wherein a first direction is a direction perpendicular to the mounting surface toward the floor surface of the reflecting box, a first surface is a rectangular virtual surface having the first side and an area on the floor surface where the first side is projected onto the floor surface toward the first direction as two opposing sides, and a second direction is a direction perpendicular to the first surface from the first side toward the second side, and a ratio of the area of ​​the first grounding portion when viewing the first surface toward the second direction to the area of ​​the first surface is 25% or more. [9] When the mounting table is viewed in a direction perpendicular to the mounting surface toward the floor of the reflecting box, the first grounding portion is located between the first side and a center line that is located at the center between the first side and the second side among virtual straight lines that are parallel to each of the first side and the second side, and does not overlap with the first side; and when the mounting table is viewed in a direction perpendicular to the mounting surface toward the floor of the reflecting box, the second grounding portion is located between the center line and the second side and does not overlap with the second side.

[10] When the mounting table is viewed in a direction perpendicular to the mounting surface toward the floor of the reflecting box, the shortest distance from the center line to the first grounding portion is a distance that falls within the range of 0.6 or more and less than 1, where the shortest distance between the center line and the first side is 1; and when the mounting table is viewed in a direction perpendicular to the mounting surface toward the floor of the reflecting box, the shortest distance from the center line to the second grounding portion is a distance that falls within the range of 0.6 or more and less than 1, where the shortest distance between the center line and the second side is 1.

[11] An electromagnetic wave testing device comprising: a reflection box; a flat-plate-shaped mounting table having a conductive mounting surface including a first side and a second side opposite the first side on which a test piece is placed; a first grounding section that electrically connects an object at ground potential to the first side; and a second grounding section that electrically connects the object to the second side, wherein an antenna that radiates electromagnetic waves at a frequency lower than the resonant frequency of the reflection box is installed in the reflection box.

[12] An electromagnetic wave testing method using an electromagnetic wave testing device comprising: a reflection box; an antenna installed in the reflection box and radiating electromagnetic waves at a frequency lower than the resonant frequency of the reflection box; and a flat-plate-shaped mounting table having a conductive mounting surface including a first side and a second side opposite the first side on which a test piece is placed, wherein an object at ground potential and the first side are electrically connected by a first grounding part, and the object and the second side are electrically connected by a second grounding part.

[0068] The embodiments of this disclosure have been described in detail above with reference to the drawings, but the specific configuration is not limited to this embodiment, and may be changed, substituted, deleted, etc. as long as it does not deviate from the gist of this disclosure. [Explanation of symbols]

[0069] 1...electromagnetic wave testing device, 2...information processing device, 10...reflection box, 11...antenna, 12...mounting table, 13...electromagnetic stirrer, 121...first side, 122...second side, ST1...first grounding portion, ST2...second grounding portion, ST10, ST11, ST12, ST13, ST14, ST15, ST16, ST17, ST18...first grounding member, ST20, ST21, ST22, ST23, ST24, ST25, ST26, ST27, ST28...second grounding member, TC...three-dimensional coordinate system, TM...test piece

Claims

1. A reflective box and an antenna installed in the reflection box and configured to radiate electromagnetic waves having a frequency lower than the resonant frequency of the reflection box; a flat-plate-shaped mounting table having a conductive mounting surface on which a test piece is placed, the mounting surface including a first side and a second side opposite to the first side; a first ground portion that electrically connects an object at a ground potential and the first side; a second ground portion that electrically connects the object and the second side; An electromagnetic wave testing device comprising:

2. When the mounting stand is viewed in a direction perpendicular to the mounting surface toward the floor surface of the reflecting box, the shape of the mounting stand is a rectangle having the first side and the second side as long sides.

2. The electromagnetic wave testing device according to claim 1.

3. The object is the floor of the reflective box.

2. The electromagnetic wave testing device according to claim 1.

4. The object is a side wall surface of the reflective box.

2. The electromagnetic wave testing device according to claim 1.

5. the first grounding portion includes a plurality of first grounding members that electrically connect the object and the first side, the second grounding portion includes a plurality of second grounding members that electrically connect the object and the second side; 2. The electromagnetic wave testing device according to claim 1.

6. the number of the plurality of second grounding members is the same as the number of the plurality of first grounding members; each of the plurality of first grounding members faces one of the plurality of second grounding members without overlapping with the other of the plurality of second grounding members in a direction parallel to the placement surface among directions orthogonal to the first side and the second side, 6. The electromagnetic wave testing device according to claim 5.

7. the first grounding portion includes one first grounding member that electrically connects the object and the first side, the second grounding portion includes one second grounding member that electrically connects the object and the second side; 2. The electromagnetic wave testing device according to claim 1.

8. a direction perpendicular to the mounting surface toward the floor surface of the reflecting box is defined as a first direction; a first surface is a rectangular virtual surface having, as two opposing sides, an area on the floor surface where the first side is projected onto the floor surface in the first direction and the first side; a direction from the first side toward the second side among directions perpendicular to the first surface is defined as a second direction; a ratio of an area of ​​the first ground contact portion, when the first surface is viewed in the second direction, to an area of ​​the first surface is 25% or more; 2. The electromagnetic wave testing device according to claim 1.

9. When the mounting table is viewed in a direction perpendicular to the mounting surface toward a floor surface of the reflecting box, the first grounding portion is located between the first side and a center line that is located at the center between the first side and the second side among imaginary straight lines that are parallel to each of the first side and the second side, and does not overlap with the first side, When the mounting table is viewed in a direction perpendicular to the mounting surface toward a floor surface of the reflecting box, the second grounding portion is located between the center line and the second side and does not overlap with the second side.

2. The electromagnetic wave testing device according to claim 1.

10. when the mounting table is viewed in a direction perpendicular to the mounting surface toward a floor surface of the reflecting box, the shortest distance between the center line and the first side is defined as 1, and the shortest distance from the center line to the first ground portion is a distance that is within a range of 0.6 or more and less than 1; When the mounting table is viewed in a direction perpendicular to the mounting surface toward the floor surface of the reflecting box, the shortest distance between the center line and the second side is set to 1, and the shortest distance from the center line to the second ground portion is a distance that is within a range of 0.6 or more and less than 1.

10. The electromagnetic wave testing device according to claim 9.

11. A reflective box and a flat-plate-shaped mounting table having a conductive mounting surface on which a test piece is placed, the mounting surface including a first side and a second side opposite to the first side; a first ground portion that electrically connects an object at a ground potential and the first side; a second ground portion that electrically connects the object and the second side; Equipped with An antenna is installed in the reflection box to radiate electromagnetic waves having a frequency lower than the resonant frequency of the reflection box. Electromagnetic wave testing equipment.

12. A reflective box and an antenna installed in the reflection box and configured to radiate electromagnetic waves having a frequency lower than the resonant frequency of the reflection box; a flat-plate-shaped mounting table having a conductive mounting surface on which a test piece is placed, the mounting surface including a first side and a second side opposite to the first side; An electromagnetic wave testing method using an electromagnetic wave testing device comprising: an object at a ground potential and the first side are electrically connected by a first ground portion; The object and the second side are electrically connected by a second ground portion. Electromagnetic wave test methods.

Images