In-situ measurement method for electromagnetic shielding effectiveness of spherical light window

Abstract

The invention discloses a spherical light window electromagnetic shielding effectiveness in-situ measurement method, and belongs to the field of microwave measurement. The measuring device is composed of a vector network analyzer, a radio frequency connecting line, a transmitting-receiving measuring antenna, a spherical light window and a fixing device of the spherical light window. According to the method, the amplitude of a spherical light window reflection coefficient is obtained through single-end measurement, then the electromagnetic shielding effectiveness is calculated through the measured reflection coefficient amplitude, the calculation process combines the spherical surface resolution and the electromagnetic wave oblique incidence theory, and the calculation thought is from overall reflection to local reflection to local transmission and finally to overall transmission. Finally, the in-situ measurement of the electromagnetic shielding effectiveness of the spherical light window is realized. According to the method, on-site in-situ measurement of the electromagnetic shielding effectiveness of the spherical light window can be realized, and the measurement precision is relatively high. The method can also be popularized and applied to other curved-surface light windows with complex shapes.

Description

Technical Field

[0001] The invention belongs to the field of microwave measurement, and in particular relates to an in-situ measurement method for the electromagnetic shielding effectiveness of a spherical optical window. Background Art

[0002] Since the establishment of electromagnetic theory, electromagnetic fields have been widely used in human society. In the field of wireless communications, mobile communications, satellite communications, and other fields all require the use of electromagnetic waves as information carriers. In the medical field, medical imaging equipment such as MRI (magnetic resonance imaging) and CT (computed tomography) use electromagnetic fields to acquire images. However, the application of electromagnetic fields also brings many problems, such as electromagnetic interference that can affect the operation of precision electronic equipment and the impact of strong electromagnetic radiation on human health. These problems have promoted the development of electromagnetic shielding technology. A key issue in electromagnetic shielding technology is addressing the electromagnetic shielding requirements of visual observation scenarios. Applications include: aircraft optical windows, medical electromagnetic isolation observation windows, and touch screens and display screens that require electromagnetic shielding.

[0003] Optical windows are widely used and come in a variety of forms, such as flat optical windows in medical electromagnetic isolation observation windows and spherical optical windows in missile seekers. To ensure that optical windows maintain excellent electromagnetic shielding performance during use, a special measurement method is required to determine their electromagnetic shielding effectiveness. This measurement method is unique in two key respects: first, it is extremely convenient, enabling the convenient measurement of the electromagnetic shielding effectiveness of optical windows at any time; and second, it is extremely versatile, capable of measuring not only flat optical windows but also spherical optical windows and other more complex curved optical windows.

[0004] Numerous studies have been conducted on electromagnetic shielding effectiveness measurement methods, which can be broadly categorized into two types: single-ended and double-ended. However, these existing methods lack both high portability and wide applicability, and therefore cannot achieve in-situ measurement of the electromagnetic shielding effectiveness of spherical optical windows.

[0005] 1. Patent 202310544430.9, "A Single-Ended Measurement Method for the Electromagnetic Shielding Effectiveness of a Metal Mesh Window," describes a single-ended measurement method for the electromagnetic shielding effectiveness of a planar optical window using a co-located transmit and receive antenna. This method indirectly measures the electromagnetic shielding effectiveness of a metal mesh window by measuring the amplitude and phase of the reflection coefficient of the metal mesh window and combining it with a two-port network transmission matrix calculation method. This single-ended measurement method enables in-situ measurement of the electromagnetic shielding effectiveness of a planar optical window, facilitating on-site measurement and evaluation of the electromagnetic shielding effectiveness of metal mesh windows.

[0006] 2. Patent 202210655696.6, "An In-Situ Test Device and Method for the Electromagnetic Shielding Effectiveness of a Planar Window," describes a single-ended measurement method for the electromagnetic shielding effectiveness of a planar window based on a dielectric resonator. This method utilizes the relationship between energy storage and energy consumption in a dielectric resonator to measure the equivalent microwave surface resistance of the conductive mesh within the planar window. The equivalent conductivity of the conductive mesh is then calculated, and the electromagnetic shielding effectiveness of the planar window is determined based on the relationship between conductivity and electromagnetic shielding effectiveness. This device, which uses a single-ended measurement method with a sensor loaded on one side, enables in-situ measurement of the electromagnetic shielding effectiveness of a planar window.

[0007] 3. The national standard GB / T 30142-2013, "Measurement Methods for the Shielding Effectiveness of Planar Electromagnetic Shielding Materials," describes two measurement methods: the flange coaxial device method and the shielded chamber method. Both are two-terminal measurement methods. The former measures frequencies from 30 MHz to 3 GHz, while the latter measures frequencies from 10 kHz to 40 GHz. Both methods can achieve high-precision measurements of the electromagnetic shielding effectiveness of planar optical windows, but are not fully applicable to spherical optical windows and other more complex curved optical windows, and in-situ measurements are difficult to achieve.

[0008] 4. The international standard IEEE Std 2715-2023, "IEEE Guide for the Characterization of the Shielding Effectiveness of Planar Materials," describes two types of measurement methods: standard and non-standard. Both methods are two-terminal. The reverberation chamber method is a standard measurement method that can be used to measure the electromagnetic shielding effectiveness of planar optical windows. The quasi-optical method, also known as the focused beam method, is a non-standard measurement method that can be used to measure the electromagnetic shielding effectiveness of planar optical windows. This method is also often used to measure the electromagnetic shielding effectiveness of spherical or other complex curved optical windows.

[0009] In summary, the main defects of the prior art are:

[0010] 1. The single-ended measurement method can meet the requirements of high convenience and can be used for in-situ measurement, but this type of method can often only be applied to the measurement of the electromagnetic shielding effectiveness of planar optical windows. In the microwave frequency band, the beam width of the co-located transmitting and receiving antennas and the size of the dielectric resonator can be achieved in the order of centimeters, so the size of the measurement area of the two on the optical window is also in the order of centimeters. When measuring an optical window with a spherical or other curved shape with a sufficiently large radius of curvature, the measurement area can be considered as a planar optical window, so this method can also measure curved optical windows with a sufficiently large radius of curvature, but at this time, there are very high requirements for the size of the curvature radius of the curved optical window to be measured, and the electromagnetic shielding effectiveness data finally obtained is also approximate data, and there is always a certain error with the real data. Therefore, the existing single-ended measurement method has a very narrow application range and does not meet the requirements of wide applicability.

[0011] 2. The two-terminal measurement method has been used to measure curved optical windows, but the accuracy of the results is unknown. Therefore, it is not yet certain that this method is fully applicable to curved optical windows, and its broad applicability is questionable. Furthermore, the two-terminal measurement method does not meet the requirements for high portability and cannot be used as a method for in-situ measurement. Therefore, the two-terminal measurement method does not meet the requirements for high portability and is uncertain about its broad applicability. Therefore, this method cannot be used for in-situ measurement of the electromagnetic shielding effectiveness of spherical optical windows. Summary of the Invention

[0012] The purpose of the present invention is to overcome the problem that existing measurement methods cannot simultaneously meet the requirements of high convenience and wide applicability, and to propose a method for measuring the electromagnetic shielding effectiveness of optical windows that is both highly convenient and widely applicable. The present invention takes spherical optical windows as the research object and proposes a complete set of measurement and calculation methods. Although the core idea of the present invention is based on spherical optical windows, it is not only applicable to spherical optical windows, but also to plane optical windows and complex curved optical windows, and is truly widely applicable. At the same time, the measuring device proposed in the present invention belongs to a single-ended measurement method measuring device, which can meet the requirements of high convenience.

[0013] The present invention aims to achieve in-situ measurement of the electromagnetic shielding effectiveness of a spherical light window, and mainly includes two parts: one is to obtain the reflection coefficient amplitude of the spherical light window by using a single-ended measurement device; the other is to obtain the electromagnetic shielding effectiveness by calculating the measured reflection coefficient amplitude.

[0014] 1. Use a single-ended measurement device to obtain the reflection coefficient amplitude of the spherical optical window. Error calibration is required during the measurement process. For spherical optical windows, the reflection coefficient amplitude error is easy to calibrate, but the reflection coefficient phase error is difficult to calibrate. Therefore, this section can only accurately obtain the reflection coefficient amplitude data, not the reflection coefficient phase data. The specific steps are as follows:

[0015] I. Prepare the components for the single-ended measurement setup. The setup's main components include a vector network analyzer, RF cables, a co-located transmit / receive measurement antenna, the spherical optical window to be measured, and its mounting fixture. The co-located transmit / receive measurement antenna is a focusing antenna, generating linearly polarized waves, with the electromagnetic waves near its focus being approximately plane waves. The setup also includes calibration components, including a vector network analyzer standard calibration piece and a spherical metal plate short-circuit calibration piece of the same size as the spherical optical window. The vector network analyzer standard calibration pieces include open-circuit calibration pieces, short-circuit calibration pieces, and matched calibration pieces.

[0016] II. Calibrate the vector network analyzer's internal errors and the transmission errors of the RF cable. Connect one end of the RF cable to the vector network analyzer and the other end to the open, short, and matched calibration components in the vector network analyzer's standard calibration kits. Remove the calibration components after calibration.

[0017] III. Calibrate free-space transmission error. First, complete the overall setup of the single-ended measurement setup. Connect one end of the RF cable to the vector network analyzer and the other end to the co-located transmit and receive antenna. Place the spherical metal plate short-circuit calibration fixture on the fixture of the spherical optical window to be measured, ensuring that the central axis of the co-located transmit and receive antenna coincides with the central axis of the spherical metal plate. After setup is complete, perform short-circuit calibration. Then, remove the spherical metal plate short-circuit calibration fixture and perform matching calibration.

[0018] IV. Measurement of the reflection coefficient amplitude of the spherical optical window to be tested. Place the spherical optical window to be tested on a fixed fixture and measure its reflection coefficient amplitude using a single-ended measurement device. Then, use the time domain gating function of the vector network analyzer to eliminate multiple reflection errors. The processed reflection coefficient amplitude is taken as the final measurement result. 11 |,|S 11 | is the overall reflection coefficient amplitude of the beam-illuminated area on the spherical window.

[0019] 2. Use the measured reflection coefficient amplitude to solve the electromagnetic shielding effectiveness. The measured reflection coefficient is the reflection coefficient of the entire beam irradiation area. Its amplitude is accurate, but the phase error is large. Therefore, the solution process only uses the reflection coefficient amplitude data. The incident conditions of plane electromagnetic waves irradiating the spherical light window are complex. There are not only vertical incidence conditions but also oblique incidence conditions. The calculation can be combined with the spherical structure. The solution process here is a method from "overall reflection" to "local reflection" to "local transmission" and finally to "overall transmission". The specific steps are as follows:

[0020] Ⅰ. The overall reflection coefficient amplitude obtained by measurement |S 11 |Calculate the reflection coefficient amplitude of the differential area in the center of the irradiated area|S 11⊥ Combining the spherical integral with the theory of oblique incidence of electromagnetic waves, the specific solution formula is:

[0021]

[0022] Among them, θ max It is the maximum incident angle of the incident beam on the spherical surface to be measured, and its value is related to the measurement antenna beam width and the curvature radius of the spherical optical window; f r_s With f r_p The fitting functions of the reflection coefficient amplitudes at oblique incidence of s-wave and p-wave relative to those at vertical incidence can be derived from thin film theory.

[0023] Ⅱ. Differentiate the reflection coefficient amplitude of the area from the center of the irradiated area |S 11⊥ |Solve S 11⊥ Phase. The central differential region of the spherical light window can be regarded as a plane light window, so the plane light window related theory can be used for derivation. The basic idea is to obtain the complete expression of the reflection coefficient of the differential region based on the electromagnetic theory of planar materials, so that if the amplitude is known, the corresponding phase can be obtained. The reflection coefficient of the differential region S 11⊥ The expression is:

[0024]

[0025] in:

[0026]

[0027] Where T represents the transmission coefficient of the medium interface, Г represents the reflection coefficient of the medium interface, γ represents the complex propagation constant, and d represents the layer thickness. Subscript A represents the air layer, subscripts F and f represent the equivalent metal film layer of the optical window, and subscripts B and b represent the base layer of the optical window. The order of the subscript letters from left to right represents the order in which the electromagnetic wave propagates through the medium.

[0028] III. Differentiate the regional reflection coefficient S from the center of the irradiated area 11⊥ Calculate the differential area transmission coefficient S at the center of the irradiated area 21⊥ The differential region of the spherical light window can be regarded as a plane light window, so the solution formula can be obtained by referring to the electromagnetic theory of plane materials:

[0029]

[0030] IV. Differentiate the regional transmission coefficient |S from the center of the irradiated area 21⊥ |Calculate the overall transmission coefficient amplitude of the beam-illuminated area|S 21 Combining the spherical integral with the theory of oblique incidence of electromagnetic waves, the specific solution formula is:

[0031]

[0032] Among them, f t_sWith f t_p The fitting functions of the transmission coefficient amplitudes at oblique incidence of s-wave and p-wave relative to those at vertical incidence can be derived from thin film theory.

[0033] V. Calculate the electromagnetic shielding effectiveness using the following formula:

[0034] SE = -10log 10 (|S 21 | 2 )

[0035] At this point, after the above two parts (a total of nine steps), the in-situ measurement of the electromagnetic shielding effectiveness of the spherical optical window can be achieved.

[0036] The innovation and good effects of the present invention are:

[0037] 1. A complete set of methods that can solve the problem of in-situ measurement of the electromagnetic shielding effectiveness of spherical light windows is proposed. Previous measurement methods are usually only applicable to flat light windows. Before the present invention, there has been no in-situ measurement method for the electromagnetic shielding effectiveness of spherical light windows. The present invention makes the in-situ measurement of the electromagnetic shielding effectiveness of spherical light windows theoretically analyzable and practically feasible, and to a certain extent fills the gap in the field of in-situ measurement of the electromagnetic shielding effectiveness of curved materials. The in-situ measurement method of the electromagnetic shielding effectiveness of spherical light windows proposed by the present invention is an indirect measurement method. It is necessary to first use a reflection method measurement device to measure the reflection coefficient amplitude of the spherical light window, and then deduce the electromagnetic shielding effectiveness from the reflection coefficient amplitude.

[0038] 2. A reflectometry measurement device suitable for spherical light windows is proposed. If the reflectometry measurement device used for a flat light window is still used to measure the reflectometry amplitude of a spherical light window, the measured value will deviate significantly from the actual reflectometry amplitude of the spherical light window. To address this issue, the present invention innovatively introduces a spherical metal plate of the same size as the spherical light window as a short-circuit calibration component, replacing the flat metal plate short-circuit calibration component for short-circuit calibration, thereby obtaining more accurate spherical light window reflectometry amplitude measurements.

[0039] 3. A method for calculating the electromagnetic shielding effectiveness of spherical windows is proposed. This method derives the electromagnetic shielding effectiveness from the measured reflection coefficient amplitude. This method innovatively combines the spherical integral with the theory of oblique incidence of electromagnetic waves. This method proposes a novel approach to calculating the electromagnetic shielding effectiveness of spherical windows: from "global reflection" to "local reflection" to "local transmission" and finally to "global transmission." This method fully accounts for the effects of oblique incidence and can improve the accuracy of indirect measurements of the electromagnetic shielding effectiveness of spherical windows.

[0040] 4. It is both highly convenient and widely applicable. It can not only realize the in-situ measurement of the electromagnetic shielding effectiveness of spherical optical windows, but is also suitable for the in-situ measurement of the electromagnetic shielding effectiveness of flat optical windows. It can also be extended to the in-situ measurement of the electromagnetic shielding effectiveness of curved optical windows with more complex shapes.

[0041] Given the aforementioned innovations and excellent results achieved, this invention has significant application value in the field of in-situ measurement of the electromagnetic shielding effectiveness of spherical optical windows. It also has implications for the in-situ measurement of the electromagnetic shielding effectiveness of optical windows with other complex curved shapes, and has potential application value in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solution adopted by the present invention, the following briefly introduces the drawings required for the technical method adopted or proposed by the present invention.

[0043] Figure 1 This is the spherical light window that is the measurement object of the present invention.

[0044] Figure 2 This is a diagram of the single-ended measurement experimental setup described in the present invention. Part Numbers: 1—Vector Network Analyzer, 2—RF Connection Cable, 3—Co-located Transmitter and Receiver Measurement Antenna, 4—Spherical Metal Plate Short-Circuit Calibration Piece, 5—Fixture Fixture.

[0045] Figure 3 It is the spherical window reflection coefficient amplitude data finally measured by the single-ended measurement experimental device.

[0046] Figure 4 It is a schematic diagram of the spherical light window beam illumination area (2w) and the central differential area (dw).

[0047] Figure 5 This is a schematic diagram of the electromagnetic transmission of a plane light window obtained by equivalently dividing the differential area of a spherical light window.

[0048] Figure 6 It is a signal flow diagram of a plane light window obtained by equivalently dividing the differential area of a spherical light window.

[0049] Figure 7 Theory and simulation 21⊥ Amplitude comparison chart, used to verify the S 11⊥ Solve S 21⊥ The accuracy of the formula.

[0050] Figure 8 This is a comparison curve of the electromagnetic shielding effectiveness obtained by the single-ended measurement method described in the present invention and the double-ended measurement method (focused beam method) commonly used in previous studies. DETAILED DESCRIPTION

[0051] The present invention will be further described below with reference to the accompanying drawings and examples.

[0052] I. Preparation of experimental measurement equipment. The main equipment includes a vector network analyzer, RF connection line, co-located transmit and receive measurement antenna, spherical optical window to be measured and its fixing fixture. The spherical optical window is an ultra-thin metal film type optical window with a curvature radius of 50mm, such as Figure 1 As shown, it features an "ITO / Ag-Al / ITO / substrate" film structure. The antenna is a dielectric lens horn antenna, generating linearly polarized waves with a focal length of 60mm, a 3dB beamwidth of 20mm, and a maximum phase difference of 9.1° within the focal spot. The calibration components prepared include a standard calibration component (using the 85052D calibration kit) and a spherical metal plate short-circuit calibration component (50mm radius of curvature, 1mm thickness, made of aluminum alloy) of the same size as the spherical optical window.

[0053] II. Calibrate the internal errors of the vector network and the transmission errors of the RF cable. Connect one end of the RF cable to the vector network analyzer and the other end to the open-circuit calibration component, short-circuit calibration component, and matching calibration component in the vector network analyzer's standard calibration kit. After calibration, remove the calibration components.

[0054] III. Calibrate the free-space transmission error. First, complete the overall construction of the single-ended measurement device. Connect one end of the RF cable to the vector network analyzer and the other end to the co-located measurement antenna. Place the spherical metal plate short-circuit calibration component on the fixed fixture of the spherical optical window to be measured. Ensure that the central axis of the co-located antenna and the central axis of the spherical metal plate coincide with each other. Figure 2 After the installation is complete, perform short-circuit calibration. Then remove the spherical metal plate short-circuit calibration component and perform matching calibration.

[0055] IV. Spherical Window Reflection Coefficient Amplitude Measurement. Place the spherical window to be measured on a fixed fixture and measure its reflection coefficient amplitude using a single-ended measurement device. The time domain gating function of the vector network analyzer is then used to eliminate multiple reflection errors. The processed reflection coefficient amplitude is taken as the final measurement result. 11 |,|S 11 | is the overall reflection coefficient amplitude of the beam illumination area on the spherical light window. Note that only the reflection coefficient amplitude is taken as the effective measurement data. Figure 3 is the measured reflection coefficient amplitude.

[0056] V. Overall reflection coefficient amplitude obtained from measurement |S 11 |Calculate the reflection coefficient amplitude of the differential area in the center of the irradiated area|S 11⊥ |, reference Figure 4 To understand the relationship between the overall area and the central differential area, the specific solution formula is:

[0057]

[0058] Among them, θ max It is the maximum incident angle of the incident beam on the spherical surface to be measured, and its value is related to the measurement antenna beam width and the curvature radius of the spherical optical window; f r_s With f r_p The fitting functions of the reflection coefficient amplitudes at oblique incidence of s-wave and p-wave relative to those at vertical incidence can be derived from thin film theory.

[0059] VI. Differentiate the reflection coefficient amplitude of the area from the center of the irradiated area |S 11⊥ |Solve S 11⊥ Phase, reference Figure 5 The derivation formula is as follows:

[0060]

[0061] in:

[0062]

[0063] Where T represents the transmission coefficient of the medium interface, Г represents the reflection coefficient of the medium interface, γ represents the complex propagation constant, and d represents the layer thickness. Subscript A represents the air layer, subscripts F and f represent the equivalent metal film layer of the optical window, and subscripts B and b represent the base layer of the optical window. The order of the subscript letters from left to right represents the order in which the electromagnetic wave propagates through the medium.

[0064] VII. Differentiate the regional reflection coefficient S from the center of the illuminated area 11⊥ Calculate the differential area transmission coefficient S at the center of the irradiated area 21⊥ ,refer to Figure 6 The derivation formula is:

[0065]

[0066] The solution formula can be verified by simulation data, such as Figure 7 ,The solution formula is consistent with the simulation data and has high accuracy.

[0067] VIII. Differentiate the regional transmission coefficient |S from the center of the illuminated area 21⊥ |Calculate the overall transmission coefficient of the beam-illuminated area|S 21 |, the solution formula is:

[0068]

[0069] Among them, f t_s With f t_p The fitting functions of the transmission coefficient amplitudes at oblique incidence of s-wave and p-wave relative to those at vertical incidence can be derived from thin film theory.

[0070] IX. Calculate the electromagnetic shielding effectiveness using the following formula:

[0071] SE = -10log 10 (|S 21 | 2 )

[0072] At this point, the electromagnetic shielding effectiveness data of the spherical optical window calculated under in-situ measurement can be obtained, and this data is compared with the electromagnetic shielding effectiveness data obtained by the double-end measurement method (focused beam method) commonly used in previous studies, such as Figure 8 At 12-18 GHz, the maximum error between the two is 1.7 dB, indicating that the in-situ measurement technology for electromagnetic shielding effectiveness of spherical optical windows proposed in the present invention has high accuracy.

[0073] The above description is only one specific example of the present invention. Obviously, for professionals in this field, after understanding the content and principles of the present invention, it is possible to make various modifications and changes in form and details without departing from the principles and structure of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A method for in-situ measurement of electromagnetic shielding effectiveness of a spherical optical window, characterized by: The method includes two parts: the first part is to obtain the reflection coefficient amplitude of the spherical light window using a single-ended measurement device, which corresponds to the following steps I, II, III and IV; the second part is to calculate the electromagnetic shielding effectiveness using the measured reflection coefficient amplitude, which corresponds to the following steps V, VI, VII, VIII and IX. The method includes the following steps: I. Prepare the components related to the single-ended measurement device. The main components of the device include a vector network analyzer, RF connecting cables, a co-located transceiver measurement antenna, and a fixture for fixing the spherical optical window to be measured. The co-located transceiver measurement antenna is a focusing antenna that generates linearly polarized waves, and the electromagnetic waves near its focus are approximately plane waves. The device also includes calibration components, including a vector network analyzer standard calibration piece and a spherical metal plate short-circuit calibration piece of the same size as the spherical optical window. The vector network analyzer standard calibration pieces include open-circuit calibration pieces, short-circuit calibration pieces, and matched calibration pieces. II. Calibrate the internal error of the vector network analyzer and the transmission error of the RF cable. Connect one end of the RF cable to the vector network analyzer and the other end to the open-circuit calibration component, short-circuit calibration component, and matching calibration component of the vector network analyzer standard calibration kit. After calibration, remove the calibration components. III. Calibrate free-space transmission error. First, complete the overall construction of the single-ended measurement setup. Connect one end of the RF cable to the vector network analyzer and the other end to the co-located transmit and receive measurement antenna. Place the spherical metal plate short-circuit calibration fixture on the fixed fixture of the spherical optical window to be measured. Ensure that the central axis of the co-located transmit and receive antenna coincides with the central axis of the spherical metal plate. After the setup is complete, perform short-circuit calibration. Then, remove the spherical metal plate short-circuit calibration fixture and perform matching calibration. IV. Measurement of the reflection coefficient amplitude of the spherical optical window to be measured: Place the spherical optical window to be measured on its fixing fixture and measure its reflection coefficient amplitude using a single-ended measurement device. Then, use the time domain gating function of the vector network analyzer to eliminate multiple reflection errors and take the reflection coefficient amplitude after processing as the final measurement result. 11 |,|S 11 | is the overall reflection coefficient amplitude of the beam illumination area on the spherical light window; V. Overall reflection coefficient amplitude obtained from measurement |S 11 |Calculate the reflection coefficient amplitude of the differential area in the center of the irradiated area|S 11⊥ |, combining the spherical surface integral and the oblique incidence theory of electromagnetic waves, the specific solution formula is: Among them, θ max It is the maximum incident angle of the incident beam on the spherical surface to be measured, and its value is related to the measurement antenna beam width and the curvature radius of the spherical optical window; f r_s With f r_p are the fitting functions of the reflection coefficient amplitudes at oblique incidence of s-wave and p-wave relative to those at normal incidence, which can be derived from thin film theory; VI. Differentiate the reflection coefficient amplitude of the area from the center of the irradiated area |S 11⊥ |Solve S 11⊥ Phase, the central differential region of the spherical light window can be regarded as a plane light window, so it can be derived using the plane light window related theory. The basic idea is to obtain the complete expression of the reflection coefficient of the differential region based on the electromagnetic theory of plane materials. In this way, if the amplitude is known, the corresponding phase can be obtained. The reflection coefficient S of the differential region 11⊥ The expression is: in: Where T represents the transmission coefficient of the medium interface, Г represents the reflection coefficient of the medium interface; γ represents the complex propagation constant, and d represents the layer thickness; subscript A represents the air layer, subscripts F and f represent the window equivalent metal film layer, and subscripts B and b represent the window base layer. The order of the subscript letters from left to right represents the order in which the electromagnetic wave propagates through the medium. VII. Differentiate the regional reflection coefficient S from the center of the illuminated area 11⊥ Calculate the differential area transmission coefficient S at the center of the irradiated area 21⊥ , the differential region of the spherical light window can be regarded as a plane light window, so the solution formula can be obtained by referring to the electromagnetic theory of plane materials: VIII. Differentiate the transmission coefficient amplitude of the region from the center of the irradiated region |S 21⊥ |Calculate the overall transmission coefficient amplitude of the beam-illuminated area|S 21 |, combining the spherical surface integral and the oblique incidence theory of electromagnetic waves, the specific solution formula is: Among them, f t_s With f t_p are the fitting functions of the transmission coefficient amplitudes at oblique incidence of s-wave and p-wave relative to the transmission coefficient amplitudes at normal incidence, which can be derived from thin film theory; IX. Calculate the electromagnetic shielding effectiveness using the following formula: SE = -10log 10 (|S 21 | 2 ) Where SE is the electromagnetic shielding effectiveness.

2. The in-situ measurement method for electromagnetic shielding effectiveness of a spherical light window according to claim 1, characterized in that: In "Obtaining the Reflection Coefficient Amplitude of a Spherical Optical Window Using a Single-Ended Measurement Device," the co-located transmit and receive antenna in step I is a near-field focusing antenna, and the spherical optical window and the spherical metal plate short-circuit calibration fixture are the same size. The short-circuit calibration fixture in step III is a spherical metal plate rather than a flat metal plate.

3. The in-situ measurement method for electromagnetic shielding effectiveness of a spherical light window according to claim 1, characterized in that: In "Using the Measured Reflection Coefficient Amplitude to Determine the Electromagnetic Shielding Effectiveness," the solution proceeds from "overall reflection" to "local reflection," then to "local transmission," and finally to "overall transmission." Breaking down the entire solution approach yields five steps: Steps V, VI, VII, VIII, and IX.

4. The in-situ measurement method for electromagnetic shielding effectiveness of a spherical light window according to claim 1, characterized in that: In "Calculating the Electromagnetic Shielding Effectiveness Using the Measured Reflection Coefficient Amplitude", step V utilizes the theory of oblique incidence of electromagnetic waves to obtain the reflection coefficient of each point on the spherical light window. The reflection coefficient of each point can be expressed as a multiple function of the normal incidence reflection coefficient. Then, using spherical surface integration from an energy perspective, the relationship between the overall reflection coefficient amplitude and the reflection coefficient amplitude in the central differential region (normal incidence) is finally obtained. Steps VI and VII both utilize the equivalent square resistance film method. Unlike the existing equivalent circuit method and the equivalent thin film method based on the equivalent refractive index model, the equivalent square resistance film method regards the electromagnetic shielding layer in the spherical light window as a metal film layer with a certain square resistance. Step VIII utilizes the theory of oblique incidence of electromagnetic waves to obtain the transmission coefficient of each point on the spherical light window. The transmission coefficient of each point can be expressed as a multiple function of the normal incidence transmission coefficient. Then, using spherical surface integration from an energy perspective, the relationship between the overall transmission coefficient amplitude and the transmission coefficient amplitude in the central differential region (normal incidence) is finally obtained.

5. The in-situ measurement method for electromagnetic shielding effectiveness of a spherical light window according to claim 1, characterized in that: This method is applicable not only to spherical light windows, but also to plane light windows and other curved light windows. For plane light windows, the short-circuit calibration piece in step III should be a flat metal plate instead of a spherical metal plate. The solution formula in step V automatically becomes |S due to the change in the shape of the light window. 11 |=|S 11⊥ |, steps VI and VII remain unchanged, and the solution formula in step VIII automatically becomes |S due to the change in the shape of the light window 21 |=|S 21⊥ For other curved light windows, the short-circuit calibration component in step III should be a curved metal plate with the same structure as the curved light window. The spherical integrals in the solution formulas in steps V and VIII should be converted to surface integrals. Steps VI and VII remain unchanged.

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