CN115453213A - Machine surface light window electromagnetic shielding effectiveness detection method based on wave-to-wave converter - Google Patents

Machine surface light window electromagnetic shielding effectiveness detection method based on wave-to-wave converter Download PDF

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CN115453213A
CN115453213A CN202210991892.0A CN202210991892A CN115453213A CN 115453213 A CN115453213 A CN 115453213A CN 202210991892 A CN202210991892 A CN 202210991892A CN 115453213 A CN115453213 A CN 115453213A
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optical window
wave
electromagnetic shielding
converter
shielding effectiveness
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孔歌星
杜微
何映锋
邓乐武
崔鹏
黄玉璐
袁雪蒂
刘小翠
潘春霞
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Chengdu Aircraft Industrial Group Co Ltd
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Chengdu Aircraft Industrial Group Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
    • G01R29/08—Measuring electromagnetic field characteristics
    • G01R29/0807—Measuring electromagnetic field characteristics characterised by the application
    • G01R29/0814—Field measurements related to measuring influence on or from apparatus, components or humans, e.g. in ESD, EMI, EMC, EMP testing, measuring radiation leakage; detecting presence of micro- or radiowave emitters; dosimetry; testing shielding; measurements related to lightning
    • G01R29/0835—Testing shielding, e.g. for efficiency

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  • General Physics & Mathematics (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)

Abstract

The invention discloses a method for detecting electromagnetic shielding effectiveness of a machine surface light window based on a wavelength converter, and belongs to the field of microwave testing. Placing the wave-co-converter at a position which is at a distance h away from the opening surface of the equivalent model of the optical window, wherein the opening surface of the wave-co-converter is vertical to the surface of the optical window, and the emission direction and the return direction of microwaves are ensured to be vertical to the surface of the optical window; connecting a coaxial feed port of the wave and wave converter with a microwave transceiver; and judging the condition of good electromagnetic shielding effectiveness of the optical window according to the scattering coefficient result of the optical window equivalent model detected by the microwave transceiver. The method can be used for detecting the electromagnetic shielding efficiency of the surface light window of the machine in situ in real time, has the advantages of low cost, strong applicability and the like, and has the potential of rapid in-situ online detection.

Description

Machine-surface optical window electromagnetic shielding effectiveness detection method based on wave-to-wave converter
Technical Field
The invention relates to the field of microwave testing, in particular to a method for detecting electromagnetic shielding effectiveness of a machine surface light window based on a wave-to-wave converter.
Background
The mechanical surface optical window is an important electromagnetic shielding component of an airborne photoelectric system, and electromagnetic shielding of the cavity is realized on the premise that optical performance requirements such as infrared light transmittance are not influenced as far as possible by plating a layer of periodically arranged metal mesh grid structure on the surface or inside of the optical window. The metal mesh is the key of the optical window electromagnetic shielding effectiveness, the side length of the metal mesh is far smaller than the wavelength of electromagnetic waves and far larger than the wavelength of infrared waves, so that the electromagnetic shielding effectiveness is ensured, and the influence on the infrared optical performance of a system is small. Since the metal mesh is a fine structure, the metal mesh structure may be damaged under the influence of external environment, so that the electromagnetic shielding performance thereof is deteriorated.
At present, the method for detecting the electromagnetic shielding effectiveness of the metal mesh grid is mainly based on a compact range radar cross section test method or a high-precision optical microscopic equipment observation method to obtain the complete condition of the metal mesh grid, so as to deduce the shielding effectiveness of an optical window. The method for detecting the electromagnetic shielding effectiveness of the optical window has the problems of machine disassembly test, low test efficiency, high cost and the like.
In the prior art, patent CN110502863A discloses a slot structure and an electromagnetic shielding effectiveness evaluation method thereof, and specifically discloses: determining structural parameters of the gap; constructing a simulation structure model with the gap according to the structure parameters of the gap; respectively arranging an electric field monitor and an electromagnetic radiation source inside and outside the simulation structure model, wherein the electromagnetic radiation source releases electromagnetic waves and simulates the simulation structure model so as to obtain a first electromagnetic numerical value through the electric field monitor; and only removing the simulation structure model, and carrying out secondary simulation to obtain a second electromagnetic value, wherein the difference value between the second electromagnetic value and the first electromagnetic value is the electromagnetic shielding effectiveness of the gap structure. This patent adopts the inboard and the outside of the structural model that awaits measuring to set up electric field monitor and electromagnetic radiation source respectively and carries out electromagnetic shielding efficiency aassessment, nevertheless can't place electromagnetic radiation source or electric field monitor in light window inside one side under the light window installation state, leads to this detection mode can't be applicable to the electromagnetic shielding efficiency aassessment of installation light window, and simultaneously, its detection mode can't be applicable to more meticulous machine table light window metal net bars structure.
Disclosure of Invention
The invention aims to solve the problems of low test efficiency, high cost and the like of machine disassembly test in the machine surface optical window electromagnetic shielding effectiveness detection in the prior art, and provides a machine surface optical window electromagnetic shielding effectiveness detection method based on a wave-to-wave converter.
In order to achieve the above object, the technical solution of the present invention is as follows:
a method for detecting electromagnetic shielding effectiveness of a machine surface light window based on a wavelength converter is characterized by comprising the following steps:
placing the wave-co-converter at a position which is at a distance h away from the opening surface of the equivalent model of the optical window, wherein the opening surface of the wave-co-converter is vertical to the surface of the optical window, and the emission direction and the return direction of microwaves are ensured to be vertical to the surface of the optical window;
connecting a coaxial feed port of the wave and wave converter with a microwave transceiver;
and judging the condition of good electromagnetic shielding effectiveness of the optical window according to the scattering coefficient result of the optical window equivalent model detected by the microwave transceiver.
Further, the determining that the electromagnetic shielding effectiveness of the optical window is intact according to the result of the scattering coefficient of the intact optical window detected by the microwave transceiver device specifically includes:
s1, calculating to obtain equivalent surface resistance of a metal mesh grid in an optical window to be measured according to the measured scattering coefficient
Figure DEST_PATH_IMAGE001
The equivalent surface resistance of the obtained metal mesh
Figure 565106DEST_PATH_IMAGE001
Substituting the following formula to obtain the equivalent conductivity of the conductive grid:
Figure 577186DEST_PATH_IMAGE002
；
in the formula (I), the compound is shown in the specification,
Figure 825765DEST_PATH_IMAGE003
in order to test the frequency of the frequency,
Figure 814450DEST_PATH_IMAGE004
is the magnetic permeability in vacuum;
s2, the obtained equivalent conductivity of the metal mesh grid is brought into the following formula to obtain the electromagnetic shielding effectiveness of the conductive mesh grid, wherein the electromagnetic shielding effectiveness is approximate to the electromagnetic shielding effectiveness of the optical window to be detected:
Figure 691139DEST_PATH_IMAGE005
；
d is the thickness of the conductive mesh,
Figure 841497DEST_PATH_IMAGE006
in order to have a dielectric constant in a vacuum,
Figure 577372DEST_PATH_IMAGE008
satisfies the following conditions:
Figure 874142DEST_PATH_IMAGE009
。
further, the wave is with converter includes coaxial and waveguide, constitutes coaxial inner conductor structure and includes two diameter size cylinders, and the bottom at the minor diameter cylinder is connected to the major diameter cylinder, and the distance h1=1.5mm of the top surface of major diameter cylinder to waveguide, the height h2=4mm of major diameter cylinder, the upper end setting chamfer r of major diameter cylinder =0.75mm.
Further, the optical window equivalent model comprises a dielectric substrate and a metal mesh grid arranged on the surface of the dielectric substrate, and the dielectric constant of the dielectric substrate is 8.2.
Further, the metal mesh is made of gold.
Further, the distance h =5mm from the optical window equivalent model to the wave and the converter aperture plane.
The working principle of the detection device is as follows: the energy is excited by a microwave transceiver at a coaxial port of the wave-to-converter to generate microwave signals, and under different damage conditions of a metal mesh structure in the optical window, due to the fact that the surface resistance of the damaged metal mesh changes, partial energy loss is caused, the returned energy is reduced, the scattering coefficient of the corresponding wave-to-converter has a certain linear change relation, the electromagnetic shielding effectiveness change condition of the optical window can be represented through the result of the scattering coefficient, and therefore the damage degree of the optical window can be inferred.
In summary, the invention has the following advantages:
the method can detect the electromagnetic shielding effectiveness of the surface optical window of the machine in situ in real time, thereby avoiding the condition that the scattering magnitude of the whole machine is changed due to the deterioration of the electromagnetic shielding effectiveness of the optical window.
Drawings
FIG. 1 is a schematic view of a detecting device;
FIG. 2 is a schematic diagram of the content portion of the WAVE CONDITIONER;
FIG. 3 is a model of an on-off slit metal mesh structured light window;
FIG. 4 is a model of a mesh fracture metal grid structured light window;
FIG. 5 is a model of an optical window with a metal grid structure without a break-make crack;
FIG. 6 is a scattering coefficient result from a wave to wave converter simulation;
FIG. 7 is a scattering coefficient result for different distances from the optical window equivalent model to the wave-to-converter aperture plane;
FIG. 8 is a result of a scattering coefficient simulation of test example 1 in example 2;
FIG. 9 is a result of a scattering coefficient simulation of test example 2 in example 2;
FIG. 10 is a result of a scattering coefficient simulation of test example 3 in example 2;
in the figure:
1 is a wave identity converter;
1a is a coaxial line feed port of the wave-to-wave converter;
1b is a waveguide of a wave converter;
1c is the inner conductor structure of the WAVE-AND-CON converter;
2 is an optical window equivalent model;
2a is an optical window medium substrate;
and 2b is a light window metal mesh grid.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
Example 1
The invention provides a method for detecting electromagnetic shielding effectiveness of a machine surface light window based on a wavelength converter, which is realized by adopting a detection device shown in figure 1. The detection device is composed of a wave-to-wave converter and an optical window equivalent model with the distance h from the wave-to-converter to the aperture plane. The detection principle of the detection device is as follows: the energy is excited by a microwave transceiver at a coaxial port of the wave-to-converter to generate a microwave signal, and under different damage conditions of a metal mesh structure in the optical window, part of energy is lost due to the surface resistance change of the damaged metal mesh, so that the returned energy is reduced, and the reflection coefficient of the corresponding wave-to-converter has a certain linear change relationship, so that the electromagnetic shielding effectiveness change condition of the optical window can be represented through the result of the reflection coefficient, and the damage degree of the optical window can be inferred.
The method for detecting the electromagnetic shielding effectiveness of the optical window by using the wavelength converter of the detection device comprises the following steps:
placing a wave-to-wave converter at a position which is at a distance h away from the opening surface of the equivalent model of the optical window, wherein the opening surface of the wave-to-wave converter is vertical to the surface of the optical window, and the emission direction and the reflection direction of microwaves are ensured to be vertical to the surface of the optical window;
connecting a coaxial feed port of the wave and converter with a microwave transceiver, and exciting a microwave signal at the coaxial port of the wave and converter by the microwave transceiver; the microwave transceiver is a device comprising a microwave source, a microwave transmitting device and a microwave receiving device, and can adopt a vector network analyzer;
step three, according to the scattering coefficient result of the optical window that microwave transceiver detects, judge the electromagnetic shielding effectiveness condition of the optical window, include specifically: carrying out simulation software test according to the obtained scattering coefficient result to obtain the equivalent surface resistance of the metal mesh grid in the optical window to be tested
Figure 746283DEST_PATH_IMAGE010
The equivalent surface resistance of the obtained metal mesh
Figure 333122DEST_PATH_IMAGE010
Substituting the following formula to obtain the equivalent conductivity of the metal mesh:
Figure 556293DEST_PATH_IMAGE002
；（1）
in the formula (I), the compound is shown in the specification,
Figure 886781DEST_PATH_IMAGE003
in order to test the frequency of the frequency,
Figure 738062DEST_PATH_IMAGE004
is the magnetic permeability in vacuum;
and substituting the obtained equivalent conductivity of the metal mesh grid into the following formula to obtain the electromagnetic shielding effectiveness of the conductive mesh grid, wherein the electromagnetic shielding effectiveness is approximate to the electromagnetic shielding effectiveness of the optical window to be detected:
Figure 902327DEST_PATH_IMAGE005
；（2）
d is the thickness of the conductive mesh,
Figure 612794DEST_PATH_IMAGE006
in order to have a dielectric constant in a vacuum,
Figure 248437DEST_PATH_IMAGE008
satisfies the following conditions:
Figure 360749DEST_PATH_IMAGE009
。
and step five, according to the formula, the electromagnetic shielding effectiveness of the optical window and the scattering coefficient present a positive correlation, so that the electromagnetic shielding effectiveness of the optical window can be judged subsequently based on the scattering coefficient result of the wavelength converter.
Example 2
Based on the detection method of embodiment 1, this embodiment optimally designs the structure and size of the inner conductor of the diplexer. The waveguide-coaxial converter shown in fig. 2 includes a coaxial structure and a waveguide, and the coaxial structure of the inner conductor shown in fig. 2 (b) includes two cylinders with different diameters, wherein the large diameter cylinder is connected to the bottom of the small diameter cylinder, the distance h1=1.5mm from the top surface of the large diameter cylinder to the waveguide, the height h2=4mm of the large diameter cylinder, and the upper end of the large diameter cylinder is provided with a chamfer r =0.75mm. The scattering coefficient result obtained by the simulation of the wave and converter is shown in fig. 6, wherein S21 represents a transmission coefficient, and S11 represents a reflection coefficient, and the result shows that the wave and converter has better matching characteristic and transmission characteristic.
As shown in fig. 1, the optical window equivalent model is composed of a dielectric substrate and a metal mesh, the metal mesh is attached to the surface of the dielectric substrate, the dielectric constant of the dielectric substrate is 8.2, and the metal mesh is made of gold.
Based on the distance h from the optical window equivalent model to the aperture surface of the diplexer by the detection device, the port of the coaxial line is connected with the microwave transceiver to feed the diplexer, and full-wave simulation analysis is performed, with the result shown in fig. 7. When the optical window sealing wave is in the same plane with the converter interface (i.e. h = 0), a resonance phenomenon occurs in a narrow frequency band, and the amplitude of the whole scattering coefficient is large, which is not favorable for the safety and stability of the test equipment. The distance h from the optical window to the wave and the converter mouth surface is continuously optimized, when h is set to be 5mm, the scattering coefficient result is relatively good, and meanwhile, the stable scattering coefficient result is achieved in a wide frequency band range. Therefore, in the subsequent simulation analysis process of the optical window equivalent models with different damage conditions, the distance h is set to be 5mm.
(1) Test example 1: the metal grid is broken to be connected and disconnected, wherein the connection and disconnection means that the metal grid is divided into two disconnected parts by a broken gap, and the model is shown in fig. 3. The results of the scattering coefficients obtained by full-wave simulation analysis with the widths of the broken gaps of the metal mesh set to 2 mm, 4mm, 6 mm, 8 mm, and 10 mm are shown in fig. 8, and the scattering coefficients tend to decrease as the widths of the gaps of the broken metal mesh become larger.
(2) Test example 2: the metal mesh was subjected to a fracture treatment to make the meshes thereof discontinuous, and the model thereof is shown in FIG. 4. The results of full-wave simulation analysis with the slit widths set to 2 mm, 4mm, 6 mm, 8 mm and 10 mm are shown in fig. 9, and the scattering coefficient tends to decrease as the slit width of the fractured metal mesh increases.
(3) Test example 3: the metal grid is subjected to fracture treatment so as not to be switched on and off, and the disconnection means that the metal grids are disconnected by fracture gaps, but connected metal grids still exist around the metal grids, and the model is shown in fig. 5. The results of full-wave simulation analysis with the slit widths set to 2 mm, 4mm, 6 mm, 8 mm, and 10 mm are shown in fig. 10, and the scattering coefficient tends to decrease as the slit width of the fractured metal mesh increases.
According to the above example, the amplitude values of different types of damaged optical windows under different damaged widths show a corresponding relationship, and the smaller the reflection amplitude of the same type of damaged optical window is, the greater the damage degree of the metal mesh grid of the optical window can be inferred, so that the damage condition of the optical window can be displayed according to the amplitude result.
By combining the simulation results of the model of the embodiment, the metal mesh electromagnetic shielding effectiveness detection method based on the wave-to-converter can intuitively display the complete damage condition of the watch crystal window of the watch crystal according to the change of the scattering coefficient amplitude.
While the present invention has been described in detail with reference to the illustrated embodiments, it should not be construed as limited to the scope of the present patent. Various modifications and changes may be made by those skilled in the art without inventive work within the scope of the appended claims.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.

Claims (6)

1. A method for detecting electromagnetic shielding effectiveness of a machine surface light window based on a wavelength converter is characterized by comprising the following steps:
placing the wave-co-converter at a position which is at a distance h away from the opening surface of the equivalent model of the optical window, wherein the opening surface of the wave-co-converter is vertical to the surface of the optical window, and the emission direction and the return direction of microwaves are ensured to be vertical to the surface of the optical window;
connecting a coaxial feed port of the wave and wave converter with a microwave transceiver;
and judging the perfect electromagnetic shielding effectiveness of the optical window according to the scattering coefficient result of the optical window equivalent model detected by the microwave transceiver.
2. The method as claimed in claim 1, wherein said determining the integrity of the electromagnetic shielding effectiveness of the optical window according to the result of the scattering coefficient of the intact optical window detected by the microwave transceiver device specifically comprises:
s1, calculating to obtain equivalent surface resistance of a metal mesh grid in the optical window to be measured according to the measured scattering coefficient
Figure 38215DEST_PATH_IMAGE001
The equivalent surface resistance of the obtained metal mesh
Figure 254171DEST_PATH_IMAGE001
Substituting the following formula to obtain the equivalent conductivity of the conductive grid:
Figure 852642DEST_PATH_IMAGE002
；
in the formula (I), the compound is shown in the specification,
Figure 870277DEST_PATH_IMAGE003
in order to test the frequency of the frequency,
Figure 161581DEST_PATH_IMAGE004
is the magnetic permeability in vacuum;
s2, the obtained equivalent conductivity of the metal mesh grid is brought into the following formula to obtain the electromagnetic shielding effectiveness of the conductive mesh grid, wherein the electromagnetic shielding effectiveness is approximate to the electromagnetic shielding effectiveness of the optical window to be detected:
Figure DEST_PATH_IMAGE005
；
d is the thickness of the conductive mesh,
Figure 366297DEST_PATH_IMAGE006
in order to have a dielectric constant in a vacuum,
Figure 538434DEST_PATH_IMAGE007
satisfies the following conditions:
Figure 676154DEST_PATH_IMAGE008
。
3. the method of claim 1, wherein the WAC comprises a coaxial line and a waveguide, the coaxial inner conductor structure comprises two cylinders with different diameters, the large diameter cylinder is connected to the bottom of the small diameter cylinder, the distance h1=1.5mm from the top surface of the large diameter cylinder to the waveguide, the height h2=4mm of the large diameter cylinder, and the upper end of the large diameter cylinder is provided with a chamfer r =0.75mm.
4. The detection method according to claim 1, wherein the optical window equivalent model comprises a dielectric substrate and a metal grid attached to a surface of the dielectric substrate, and the dielectric constant of the dielectric substrate is 8.2.
5. The detection method according to claim 4, wherein the metal mesh is made of gold.
6. The detection method according to claim 4, wherein the distance h =5mm from the light window equivalent model to the wave-to-converter aperture plane.
CN202210991892.0A 2022-08-18 2022-08-18 Machine surface light window electromagnetic shielding effectiveness detection method based on wave-to-wave converter Pending CN115453213A (en)

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