A replacement wall and its use, a method and system for shielding a measurement of an electromagnetic field inside a cavity

Abstract

The application belongs to the field of electromagnetic wave measurement, and particularly relates to a replacement wall and application thereof, and a method and system for measuring an electromagnetic field inside a shielding cavity. The cavity replacement wall is composed of a light-transmissive conductor material, and a light-transmissive conductor layer presents the characteristics of a metal cavity wall and can maintain the original environment inside the cavity. By plating a light-transmissive conductor film on the surface of a substrate glass, the glass presents the characteristics of a metal, and the original cavity wall can be simulated, so that the characteristics of the metal cavity remain unchanged. Thanks to the high transmissivity of the glass plated with the light-transmissive conductor film to laser, a photosensitive semiconductor material layer is introduced inside the glass, and by using a light-controlled plasma scattering measurement technology, the field distribution inside the metal cavity can be measured. By using this technology, the measurement of the inherent electromagnetic environment inside the metal cavity can be realized without destroying the metal characteristics of the metal cavity, so that the problem that the field distribution inside a closed cavity cannot be directly measured for a long time is solved.

Description

Technical Field

[0001] This application belongs to the field of electromagnetic wave measurement, specifically relating to a replacement wall and its application, and a method and system for measuring the electromagnetic field inside a shielded cavity. Background Technology

[0002] In recent years, various measurement technologies have developed rapidly, and the methods for measuring electromagnetic fields have become increasingly diversified. However, the electric field distribution inside cavity environments such as circuit systems and chip packages is difficult to measure and can only be evaluated based on experience or indirect methods. Nevertheless, the measurement of the electric field inside the cavity is of great value for the design of shielding, packaging, or shielding structures of electronic and electrical systems. For an unknown closed or semi-closed metal cavity, there is currently no specific means to directly observe the electromagnetic field distribution inside. However, the electromagnetic field distribution inside a closed cavity has practical engineering significance and research value in microwave devices, such as cavity filters, waveguide slot antennas, and electromagnetic compatibility fields, such as the field distribution inside a shielded enclosure.

[0003] A photoelectric control plasma scattering measurement technique based on the photoconductivity effect was proposed. This technique uses laser to excite photosensitive semiconductor materials to generate photogenerated plasma. By using the electromagnetic scattering signal of the plasma, the electromagnetic field to be measured can be inverted and measured (Patent No.: CN202110759705.1). This indirect measurement technique using plasma scattering signals makes it possible to measure the field distribution in closed / semi-closed cavities. Summary of the Invention

[0004] Technical Problem: This application proposes a novel method and system for measuring the electric field distribution inside a closed or semi-closed cavity based on transparent conductors, glass, and photosensitive semiconductor materials. The aim is to provide a shielded cavity electromagnetic field measurement scheme that is highly accurate, efficient, adaptable, and easy to implement. Technical solution

[0005] A replacement wall for a shielded cavity includes a light-transmitting conductor layer, a substrate glass layer, and a photosensitive semiconductor layer, wherein the photosensitive semiconductor layer is located inside the cavity. Here, "inner side" refers to the photosensitive semiconductor layer being closer to the inner cavity of the shielded cavity than the other two layers; that is, the light-transmitting conductor layer and the substrate glass layer meet the requirements of the replacement wall's metallic and light-transmitting properties, enabling a laser beam to pass through the first two layers and irradiate the inner photosensitive semiconductor layer to generate plasma. This, in turn, allows for the scattering of the electromagnetic field within the cavity by the plasma.

[0006] Furthermore, the light-transmitting conductor layer is one or more of indium tin oxide, graphene, metal nanowires, carbon nanotubes, conductive polymers, and thin films of silver, copper, and aluminum. The light-transmitting conductor layer can be formed independently and arranged in a way that is bonded or parallel to the substrate glass layer. To enhance the metallic properties of the replacement wall, a transparent conductive layer can be deposited onto the substrate glass using methods such as coating, lamination, and magnetron sputtering. This completely simulates the original cavity environment, thus avoiding disruption of the original cavity's electromagnetic environment during the replacement of one wall. Magnetron sputtering can be performed at room temperature or low temperature, avoiding damage to the glass substrate from high temperatures (such as softening of sodium-calcium substrates), and producing a uniform coating with a nanometer-thickness (50-200 nm), ensuring a transmittance >85% and low surface resistivity. Sputtering uses higher-energy particles, promoting atomic bonding between the coating and the substrate and reducing the risk of peeling. It also operates at lower temperatures than chemical vapor deposition (CVD), avoiding thermal deformation of the glass. In laser applications, sputtered coatings offer better optical smoothness, reducing scattering losses to the laser beam.

[0007] Furthermore, the substrate glass is one or more of sodium-calcium-based or borosilicate-based substrate glasses. These two types of substrate glasses have lower coefficients of thermal expansion compared to other materials, and their uniform refractive index and low birefringence reduce laser beam distortion, ensuring plasma excitation efficiency. The heat resistance (>500°C vs <100°C), hardness, and chemical stability of sodium-calcium-based and borosilicate-based glasses far exceed those of polymers, making them suitable for high-power lasers and chemical exposure environments. The glass substrate supports high-temperature deposition of TCOs (such as ITO, deposition temperature ~300°C).

[0008] Furthermore, the light-transmitting conductor layer and the substrate glass are attached and connected in any order to form a metallic light-transmitting layer. The photosensitive semiconductor layer is attached to the inner wall of the metallic light-transmitting layer, or the photosensitive semiconductor layer is placed inside the cavity at any distance parallel to the metallic light-transmitting layer. The optimal position for collecting scattered signals can be found by adjusting the position of the photosensitive semiconductor inside the cavity, or multi-point measurements at different locations in three-dimensional space inside the cavity can be achieved.

[0009] This application also provides an application for a replacement wall used to measure electromagnetic fields inside a closed or semi-closed cavity. The purpose is to illustrate that this replacement wall is used to simulate a metal wall, thereby enabling electromagnetic field measurements within a shielded cavity.

[0010] This application also provides a method for measuring the electromagnetic field inside a shielded cavity based on the photoconductive effect. This method is applied to the aforementioned replacement wall and includes the following steps: S1: Replace one of the metal walls of the cavity to be tested with the cavity replacement wall mentioned above; S2: Using signal processing and control devices, the area to be measured and measurement parameters are set, and the scanning path of a single beam or the illumination position of an array of beams and the measurement positions thereon are calculated; S3: The operation of the light source control device causes the laser light source to irradiate the designated position of the photosensitive semiconductor material in the metal replacement wall. The initial position on the scanning path is irradiated by the light-transmitting conductor layer and glass to the photosensitive semiconductor layer. Under the action of semiconductor photoelectric effect, plasma is generated and scattered with the electromagnetic signal in the cavity at that position, generating a scattered electromagnetic signal. S4: The receiving device detects the scattered electromagnetic signal received at the port of the cavity under test and transmits it to the signal processing and control device. S5: The signal processing and control device records the amplitude and phase of the scattered electromagnetic signal detected by the receiving device at the current irradiation position; S6: Repeat steps S3 to S5 to complete the comprehensive measurement of the electromagnetic field distribution inside the cavity to be measured, and obtain the amplitude and phase distribution of the electromagnetic field to be measured in the cavity.

[0011] This application also provides a system for measuring the electromagnetic field inside a shielded cavity, characterized in that it comprises: A laser light source used to generate a laser beam; A light source control device is used to control the laser beam to illuminate a designated position on the photosensitive semiconductor chip. The position is determined by the signal processing and control device. The cavity replacement wall is made of a light-transmitting conductive material. The light-transmitting conductive layer exhibits the characteristics of a metal cavity wall, which can maintain the original environment inside the cavity.

[0012] The photosensitive conductor layer is used to receive laser beam irradiation and form a plasma spot at the beam irradiation location. The plasma spot scatters the unknown electromagnetic field, generating a scattered electromagnetic signal.

[0013] The receiving port is used to receive scattered electromagnetic signals; A receiving device, electrically connected to a receiving port, is used to detect the scattered electromagnetic signals received by the receiving port; The signal processing and control device is electrically connected to the receiving device and the light source control device. Based on the set measurement range parameters, it calculates the beam scanning path and the measurement positions along it, controls the light source control device to make the beam illuminate each position in sequence, reads and records the scattered signal detected by the receiving device at the corresponding position, and obtains the amplitude and phase distribution of the electromagnetic field to be measured in the region.

[0014] Furthermore, the receiving port includes one or more of the newly added ports fixed on the replacement wall or the original cavity wall, or the original ports contained in the device itself within the cavity.

[0015] The beneficial effects of this application are that, 1. By depositing a light-transmitting conductive film onto the surface of a glass substrate, the glass exhibits metallic properties, simulating the original cavity walls and ensuring the unchanged characteristics of the metal cavity. Benefiting from the high laser transmittance of the glass coated with the light-transmitting conductive film, a photosensitive semiconductor material layer is introduced inside this glass. Using photo-controlled plasma scattering measurement technology, the field distribution inside the metal cavity can be measured. This technology allows for the measurement of the inherent electromagnetic environment within the metal cavity without damaging its metallic properties, thus solving the long-standing problem of directly measuring the field distribution within a closed cavity. This measurement technology, combined with plasma scattering, enables direct measurement of the electric field distribution within a closed or semi-closed cavity. It overcomes the shortcomings of traditional techniques in measuring the electromagnetic field inside metal cavities. This invention can measure the electromagnetic field within metal cavities with arbitrarily replaceable walls, effectively preserving the original electromagnetic environment inside the cavity. Furthermore, the combination of plasma scattering measurement technology significantly accelerates the measurement speed and improves accuracy. 2. Place the photosensitive semiconductor layer parallel to the metallic light-transmitting layer inside the cavity at an arbitrary distance. The optimal position for collecting scattered signals can be found by adjusting the position of the photosensitive semiconductor inside the cavity, or multi-point measurements can be achieved at different locations in three-dimensional space within the cavity.

[0016] 3. This measuring device is also more adaptable to cavity structures. Existing technologies often have relatively strict requirements for cavity structures, such as requiring special port configurations or having specific limitations on cavity shape. However, this invention overcomes these structural limitations by using ITO glass with silicon inlaid on the inner side of one side of the cavity, allowing a port to be added to the replacement wall. This method and system are applicable to cavities of almost all shapes and sizes, requiring no large-scale modification of the cavity, exhibiting wide applicability and good compatibility, and can be easily integrated into existing cavity systems.

[0017] 4. It can quickly assess the electromagnetic wave characteristics within a shielded cavity, making it suitable for dynamic environments such as nuclear fusion plasma or high-power laser welding. Its rapid detection capability supports real-time monitoring, reducing downtime in testing scenarios and improving safety and minimizing impact on the existing working environment by avoiding direct contact with electromagnetic fields. Attached Figure Description

[0018] Figure 1 This is a system topology diagram of this application. Detailed Implementation Example

[0019] A replacement wall for a shielding cavity. The "replacement wall" is a multi-layered, thin component with a total thickness controlled between 1.0 and 2.5 mm to ensure mechanical stability, high optical transmittance (>80% for 1064 nm laser), and electromagnetic shielding effectiveness (>20 dB for the GHz range). The layer sequence from the outside to the inside is as follows: First layer: Light-transmitting conductor layer (outermost layer, facing the outside of the cavity) It is composed of indium tin oxide (ITO, In:Sn ratio 90:10) or other transparent conductive oxides. It simulates the electromagnetic shielding characteristics of a metal wall (surface resistance <30Ω / sq, providing >20dB attenuation), while allowing lasers to pass through.

[0020] With a thickness of 50-150 nanometers, the thin-layer design reduces laser absorption and maintains high light transmittance.

[0021] An external ITO layer ensures that the laser can penetrate directly from the outside to the internal photosensitive layer, while providing a Faraday cage effect to shield external electromagnetic interference and protect the actual working condition measurement environment inside the cavity.

[0022] Second layer: Substrate glass layer (intermediate layer) Borosilicate glass is the preferred choice, with soda-lime glass as an alternative. It provides structural support and light transmission, serves as the substrate for the outer layer, and ensures interlayer adhesion and thermal stability.

[0023] With a thickness of 1-2 mm, it combines rigidity and thinness, making it suitable for cavity integration. The substrate glass serves as an intermediate layer to isolate the internal and external environments, protecting the photosensitive semiconductor layer from external chemical or mechanical damage, while also supporting double-sided deposition processes.

[0024] Third layer: Photosensitive semiconductor layer (innermost layer, facing the inside of the cavity) Silicon, cadmium sulfide (CdS, n-type semiconductor, band gap ≈ 2.4eV) or other photosensitive materials (such as gallium arsenide, GaAs) are used.

[0025] Plasma is generated by laser excitation, which is then scattered with electromagnetic waves within the cavity to produce a measurable signal. The inner layer is positioned close to the electromagnetic field to enhance scattering efficiency.

[0026] 100-500 nanometers ensures sufficient photosensitive response while avoiding excessive laser absorption due to excessive thickness.

[0027] One way to connect with the substrate glass layer is through an attachment mode: CdS is directly deposited on the inside of the substrate glass, isolated from the ITO layer by the glass, ensuring charge transfer efficiency and a compact structure.

[0028] Another connection method is the split mode: a separate semiconductor substrate is placed inside the cavity at a certain distance from the metallic light-transmitting layer, allowing for flexible adjustment of the position to optimize laser alignment or scattering signal capture.

[0029] The inner CdS layer interacts directly with the electromagnetic waves inside the cavity, maximizing the coupling between the plasma and the electromagnetic field, while being protected by glass to reduce environmental interference.

[0030] Step 1: Preparation of substrate glass Preferred choice: Borosilicate glass (such as Schott Borofloat, coefficient of thermal expansion ≈ 3.3 × 10⁻) 6 / K, transmittance >90% at 1064nm).

[0031] Alternative: Sodium-calcium glass (cost approximately 1 / 2 to 1 / 3 that of borosilicate glass, but with a coefficient of thermal expansion ≈ 9 × 10⁻) 6 / K).

[0032] Dimensions: 10×10×1-2 mm (can be customized according to cavity size).

[0033] Surface cleaning ensures uniform ITO and CdS deposition, reducing the impact of defects on laser transmission and shielding effectiveness. Ultrasonic cleaning or plasma cleaning can be used. Ultrasonic cleaning involves sequentially soaking in acetone and isopropanol for 10 minutes each, rinsing with deionized water, and drying with nitrogen. Plasma cleaning uses oxygen plasma (100W, 5 minutes) to remove organic residues, enhance surface hydrophilicity (contact angle <10°), and improve the adhesion of subsequent layers.

[0034] Step 2: Deposition of the light-transmitting conductor layer Method: Magnetron sputtering (if lower resistance <10Ω / sq is required): ITO target (90:10In:Sn) was used in an Ar / O2 atmosphere (10⁻³ Torr), substrate temperature 200°C, deposition rate 1 nm / s, and thickness 100 nm. Post-annealing (250°C, nitrogen, 1 h) was performed to optimize crystallinity.

[0035] After molding, it has a nanocrystalline cubic structure with a surface roughness of <5nm, transmittance of >90%, and shielding effectiveness of >20dB (1-10GHz).

[0036] The outer ITO layer directly shields against external EMI, protecting the measurement environment inside the cavity; the thin-layer design minimizes laser absorption, ensuring efficient transmission to the inner CdS layer.

[0037] Alternative method: Sol-gel method, which balances cost and performance, and is suitable for substrate glass.

[0038] (1) Precursor preparation: Dissolve 1.1727gInCl3·4H2O and 0.1402gSnCl4·5H2O in 100mL of deionized water, and add 2.0mL of 25%NH3 solution with stirring until pH 9 is reached, forming a hydrated gel.

[0039] (2) Centrifuge, wash with deionized water and ethanol, redisperse in 25 mL of ethanol, and add 0.1 w / v% polyvinylpyrrolidone (PVP) stabilizer (solid content 3.5 w / v%).

[0040] (3) Sedimentation: Spin-coat 50µL of sol (3000rpm, 30s) on the outside of the substrate glass (facing the outside of the cavity).

[0041] Repeat 1-3 times (without intermediate heating) to control the thickness to 50-150 nanometers.

[0042] Annealing: Anneal in air at 550°C (silicon boron-based) or 400°C (sodium calcium-based, avoiding softening point ≈700°C) for 30 minutes to form crystalline ITO, with surface resistivity reduced to 10-30Ω / sq and transmittance >90% (633nm).

[0043] Step 3: Photosensitive semiconductor layer (1) Attachment mode (direct deposition on the inside of the substrate glass): Method: Chemical bath deposition (CBD), low temperature (<100°C), suitable for glass substrates.

[0044] Process: Precursor preparation: Mix 10 mL of 0.05 M CdCl2, 20 mL of 0.5 M sodium citrate, 5 mL of 0.3 M KOH, 5 mL of borate buffer (pH 10), 10 mL of 0.5 M thiourea, and 40 mL of deionized water.

[0045] Deposition: Immerse the inside of the substrate glass (ITO side up, to protect against deposition) in a 40°C bath for 3 hours to form a 100-500 nm CdS layer.

[0046] Post-treatment: Air annealing at 250°C for 5 minutes to adjust the band gap (2.55eV→2.38eV) and enhance crystallinity (hexagonal / cubic phase). Transmittance ≈ 70% (445nm), polycrystalline particles (100-600nm), photosensitivity suitable for laser-excited plasma. Attaching CdS simplifies the structure, reduces laser path loss, allows direct interaction with the electromagnetic field, and enhances the scattering signal.

[0047] Method: CdS is deposited on another thin substrate glass (0.5-1 mm thick, borosilicate-based or sodium-calcium-based) using CBD, with the same process as above.

[0048] Assembly: Place the CdS element in the cavity, 1-5 mm from the replacement wall, and fix it with mechanical clamps or optical adhesive, aligning it with the laser path.

[0049] Alternative method: Pulsed laser deposition (PLD) to improve film quality: Using an Nd:YAG laser (355nm, 5ns pulse, 10Hz, 4.3J / cm²).

[0050] In 10⁻ 7 Under Torr vacuum and substrate temperature of 250°C, with a target-substrate distance of 6 cm, 200 nm of CdS (band gap 2.35 eV) was deposited. It exhibits high crystallinity, fast response speed, and is suitable for high-frequency electromagnetic wave scattering.

[0051] The split-mode allows for independent optimization of CdS positions, reduces thermal coupling interference, and allows for flexible adjustment of scattering geometry. Example

[0052] A method and system for measuring the electromagnetic field distribution inside a (closed / semi-closed) shielded cavity based on the photoconductivity effect. Figure 1 The figure shows a method and system for measuring the electromagnetic field distribution inside a (closed / semi-closed) shielded cavity with photoconductive effect, as described in the first embodiment of the present invention. Figure 1 As shown in the figure, this is the overall structural diagram of the system. The key design feature of this invention is that one side of the cavity under test is replaced with a three-layer structure consisting of a light-transmitting conductor, a substrate glass, and a photosensitive semiconductor. This replacement wall is a three-layer structure consisting of a light-transmitting conductor 88, a substrate glass 77, and a photosensitive semiconductor 96, and is used to replace one side of the cavity under test. Furthermore, an output port is designed on this replacement wall to allow the internal scattered signals to be transmitted.

[0053] The aforementioned transparent conductive films with metallic properties include, but are not limited to, ITO (indium tin oxide), graphene, metal nanowires, carbon nanotubes, conductive polymers, and silver, copper, and aluminum films.

[0054] The cavity wall structure includes, but is not limited to, a three-layer structure of light-transmitting conductor 88, substrate glass 77, and photosensitive semiconductor 96. Alternatively, the photosensitive semiconductor sheet can be placed in a cavity at any distance from the glass without contacting the glass coated with a light-transmitting conductor film.

[0055] When the system controls the laser to irradiate through the light-transmitting conductor layer 88 and the glass layer 77 to the corresponding position of the photosensitive semiconductor layer 96, plasma 20 will be generated at this position, scattering the electromagnetic field in the cavity at this position. As a result, the scattered signal 34 will be transmitted from the port 28. This process, by using the structure with metallic properties designed in this invention, completely preserves the original electromagnetic environment of the cavity, and the laser can pass through it. It utilizes plasma measurement technology, which is a relatively comprehensive measurement method.

[0056] The method and system for measuring the electromagnetic field distribution inside a (closed / semi-closed) shielded cavity with photoconductive effect in this example include: a laser source 67 for generating a laser beam 25; a source control device 58 for controlling the laser beam 25 to irradiate a set position on an ITO glass with a silicon layer on its inner surface, the position being determined by a signal processing and control device 53; a replacement wall with a three-layer structure consisting of a light-transmitting conductor 88, a substrate glass 77, and a photosensitive semiconductor 96, for receiving the irradiation of the laser beam 67 and forming a plasma spot 20 at the beam irradiation position, the plasma spot 20 scattering the unknown electromagnetic field 30 and generating a scattered electromagnetic signal 34; and a cavity 10 to be measured. Receiver port 28 is a receiver port installed on the wall of the designed cavity, but it is not limited to other cavity ports that have their own ports. For example, the cavity filter itself has a port, and its own port can also be used. In other instances, this port can be any input or output port that it has on its own. The receiving device 36 is electrically connected to the receiving port 28 and is used to detect the scattered electromagnetic signal 84 received by the receiving antenna; The signal processing and control device 53 is electrically connected to the receiving device 36 and the light source control device 58. According to the set measurement parameters, it calculates the beam scanning path and the measurement positions on it, controls the light source control device 58 to make the beam 25 illuminate each position in sequence, reads and records the scattered signal 34 detected by the receiving device at the corresponding position, and obtains the amplitude and phase distribution of the electromagnetic field to be measured in the region.

[0057] The specific implementation steps are as follows: Step 1: Replace one side of cavity 10 with the replacement wall 12 of the three layers of transparent conductor 88, substrate glass 77 and photosensitive semiconductor 96, and face this side toward the direction of laser 25 irradiation.

[0058] Step 2: Using the signal processing and control device 53, set the area to be measured and the measurement parameters, and calculate the beam scanning path and the measurement positions on it.

[0059] Step 3: Control the light source control device 58 to make the beam 25 generated by the laser light source 67 irradiate the initial position on the scanning path. The laser passes through the light-transmitting conductor layer and glass to irradiate the photosensitive semiconductor layer. Under the action of semiconductor photoelectric effect, plasma 20 is generated and the electromagnetic signal in the cavity to be tested at the position is scattered to generate a scattered electromagnetic signal 34.

[0060] Step 4: The output port 28 on the cavity replacement wall receives the scattered electromagnetic signal 34 and transmits it to the receiving device 36.

[0061] Step 5: The receiving device 36 detects the scattered electromagnetic signal 28 received by the port 28 of the cavity under test and transmits it to the signal processing and control device 53.

[0062] Step 6: The signal processing and control device 53 records the amplitude and phase of the scattered electromagnetic signal 34 detected by the receiving device 36 at the current irradiation position. Step 7: Repeat steps 3 to 6 to complete the comprehensive measurement of the electromagnetic field distribution in the area to be measured, and obtain the amplitude and phase distribution of the electromagnetic field to be measured in the area.

[0063] The electromagnetic field inside an unknown metal cavity can be accurately and quickly measured by following the above steps. This preserves the original internal environment of the cavity and uses optical measurement methods for fast and accurate measurement, greatly improving the quality and efficiency of electromagnetic field measurement inside the cavity.

Claims

1. A replacement wall for a shielding cavity, characterized in that, It includes a light-transmitting conductor layer and a photosensitive semiconductor layer, wherein the photosensitive semiconductor layer is located inside the cavity.

2. A replacement wall as described in claim 1, characterized in that, The light-transmitting conductor layer is one or more of the following: indium tin oxide, graphene, metal nanowires, carbon nanotubes, conductive polymers, and silver, copper, and aluminum thin films; the light-transmitting conductor layer can be formed by attaching the above-mentioned light-transmitting conductor layer material combination onto a light-transmitting substrate.

3. A replacement wall as described in claim 1 or 2, characterized in that, The photosensitive semiconductor layer is attached to the inner wall of the metallic light-transmitting layer, or the photosensitive semiconductor layer and the metallic light-transmitting layer are placed at any distance inside the cavity.

4. A replacement wall as described in claim 3, characterized in that, The light-transmitting substrate includes a substrate glass layer, wherein the substrate glass is one or more of sodium-calcium-based or silicon-boron-based substrate glass, and the light-transmitting conductor layer is attached and connected to the substrate glass in any order to form a metallic light-transmitting layer.

5. An application of a replacement wall, characterized in that, The replacement wall is the replacement wall as described in claim 4, and the replacement wall is used to measure the electromagnetic field inside a closed or semi-closed cavity.

6. A method for measuring the electromagnetic field inside a shielded cavity based on the photoconductive effect, characterized in that, The method is applied to any one of the replacement walls according to claims 1-4, and the method includes the following steps: S1: Replace one metal wall of the cavity to be tested with the cavity replacement wall as described in claim 1; S2: By using signal processing and control devices, the area to be measured and measurement parameters are set, and the beam scanning path and measurement positions along it are calculated; S3: The operation of the light source control device causes the laser light source to irradiate the designated position of the photosensitive semiconductor material in the metal replacement wall. The initial position on the scanning path is irradiated by the light-transmitting conductor layer and glass to the photosensitive semiconductor layer. Under the action of semiconductor photoelectric effect, plasma is generated and the electromagnetic signal in the cavity at the position is scattered to generate a scattered electromagnetic signal. S4: The receiving device detects the scattered electromagnetic signal received at the port of the cavity under test and transmits it to the signal processing and control device. S5: The signal processing and control device records the amplitude and phase of the scattered electromagnetic signal detected by the receiving device at the current irradiation position; S6: Repeat steps S3 to S5 to complete the comprehensive measurement of the electromagnetic field distribution inside the cavity to be measured, and obtain the amplitude and phase distribution of the electromagnetic field to be measured in the cavity.

7. A system for measuring the electromagnetic field inside a shielded cavity, characterized in that, include: The replacement wall as described in claim 4 is made of a light-transmitting conductor material, and the light-transmitting conductor layer exhibits the characteristics of a metal cavity wall, which can maintain the original environment inside the cavity; Also includes: A laser light source used to generate a laser beam; A light source control device is used to control the laser beam to illuminate a designated position on a photosensitive semiconductor wafer, the position being determined by a signal processing and control device; A photosensitive conductor layer is used to receive laser beam irradiation and form a plasma spot at the beam irradiation position. The plasma spot scatters an unknown electromagnetic field and generates a scattered electromagnetic signal. The receiving port is used to receive scattered electromagnetic signals; A receiving device, electrically connected to a receiving port, is used to detect the scattered electromagnetic signals received by the receiving port; The signal processing and control device is electrically connected to the receiving device and the light source control device. Based on the set measurement range parameters, it calculates the beam scanning path and the measurement positions along it, controls the light source control device to make the beam illuminate each position in sequence, reads and records the scattered signal detected by the receiving device at the corresponding position, and obtains the amplitude and phase distribution of the electromagnetic field to be measured in the region.

8. The electromagnetic field measurement system inside a shielded cavity as described in claim 7, characterized in that, The receiving port includes one or more of the newly added ports fixed on the replacement wall or the original cavity wall, or the original ports contained in the device itself inside the cavity.

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