Shielding effectiveness test method of shielding strip based on opposite-side probe near cavity method

Abstract

The invention relates to the technical field of shielding effectiveness testing, in particular to a shielding effectiveness testing method for a shielding strip based on a method that an opposite-side probe is close to a cavity, and the method comprises the steps: firstly, arranging a to-be-tested shielding strip on a fixing device; wherein the fixing device is composed of two adjacent cavities, a signal transmitter is arranged in one cavity of the fixing device, a signal receiver is arranged in the other cavity of the fixing device, then transmission parameters of the to-be-detected shielding strip are determined according to transmitting parameters of the signal transmitter and receiving parameters of the signal receiver, the to-be-detected shielding strip is removed, and the to-be-detected shielding strip is obtained. The method comprises the following steps: acquiring a transmission parameter when a to-be-tested shielding strip is not installed, finally determining the shielding effectiveness of the to-be-tested shielding strip according to the transmission parameter of the to-be-tested shielding strip and the transmission parameter when the to-be-tested shielding strip is not installed, and carrying out convenient evaluation between frequencies on a shielding gasket in a frequency range as high as 40GHz through a near-field shielding test of a cavity by the cavity. And compared with the traditional same-side single-pole probe configuration, the precision is higher.

Description

Technical Field

[0001] This invention relates to the field of shielding effectiveness testing technology, and specifically to a shielding effectiveness testing method for shielding strips based on the adjacent cavity method of the opposite side probe. Background Technology

[0002] Electromagnetic interference (EMI) sealing gaskets are specialized components used to establish a connection between metal components within a metal enclosure and a printed circuit board (PCB), electronic chassis, equipment housing, or electromagnetic chamber, thereby achieving EMI shielding and sealing. With the continuous increase in operating frequencies and packaging density on PCBs, stringent requirements have been placed on EMI shielding to avoid issues related to regulatory electromagnetic compatibility (EMC) and internal noise. A common method for shielding PCBs is to use a metal enclosure with multiple cavities. This enclosure is electrically connected to the PCB's grounding path using a sealant made of conductive silicone. Evaluations of the shielding effectiveness of conductive materials in the telecommunications industry primarily focus on achieving internal isolation from one cavity to another.

[0003] Several standard methods exist for measuring the electromagnetic shielding effectiveness of EMI gaskets, depending on the application environment and the specific method used. The method chosen depends on the gasket's electromagnetic characteristics and its installation method. IEC 61000-4-23 specifies a test method designed to protect equipment from high-altitude electromagnetic pulses (HEMPs) and other forms of radiated interference. This method verifies that the conductive seal establishes a conductive path between two parts of the equipment housing. The measurement method uses a four-electrode approach to measure resistivity and represents the seal opening via an equivalent circuit where resistance and capacitance are connected in parallel and in series with an inductance representing the current path within the housing wall. SAE ARP 6248 describes a method for measuring the equivalent inductance of a seal using a stripline test method. ASTM D4935-18 and SAE ARP 1705C provide methods based on coaxial transmission line characteristics for measuring the shielding performance of samples made of various materials over a wide frequency range. MIL-DTL-83528G-2017 evaluates conductive materials by measuring the attenuation of radiated radio frequency signals at a 24×24 opening within a shielded enclosure; this method is widely used in manufacturers' datasheets. SAE ARP 1173 places the gasket under test between the housing and the cover, providing a suitable technique for measuring the electromagnetic interference (EMI) shielding effectiveness of gaskets made of different materials. IEC 61000-4-21 and IEEE Std 299.1 detail the function and application of reverberation chambers in electromagnetic measurements, providing a method for evaluating the EMI shielding effectiveness of EMI gaskets using such chambers. IEEE Std 2716TM-2022 provides a series of methods for characterizing the EMI shielding effectiveness of board-level shielding, covering the characteristics of shielding gaskets up to 40 GHz, and provides a reference for selecting appropriate measurement techniques. The IEEE STD 1302-2019 standard provides an in-depth analysis of the advantages and disadvantages of each recommended EMI shielding effectiveness measurement method and provides detailed documentation for each method. However, existing testing methods and systems still need further improvement in several key aspects: simplification of operation, ease of installation, measurement accuracy, dynamic range, and repeatability. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a shielding effectiveness testing method for shielding strips based on the adjacent cavity method of the opposite side probe, so as to overcome the problems existing in the current prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This application provides a method for testing the shielding effectiveness of a shielding strip based on the adjacent cavity method using a side probe, including: The shielding strip to be tested is mounted on a fixing device; wherein the fixing device consists of two adjacent cavities; A signal transmitter is provided in one cavity of the fixing device, and a signal receiver is provided in the other cavity of the fixing device; The transmission parameters of the shielding strip under test are determined based on the transmission parameters of the signal transmitter and the reception parameters of the signal receiver. Remove the shielding strip to be tested and obtain the transmission parameters when the shielding strip to be tested is not installed; The shielding effectiveness of the shielding strip under test is determined based on the transmission parameters of the shielding strip under test and the transmission parameters when the shielding strip under test is not installed.

[0006] Furthermore, in the method described above, determining the transmission parameters of the shielding strip under test based on the transmission parameters of the signal transmitter and the reception parameters of the signal receiver includes: Based on the transmission parameters of the signal transmitter and the reception parameters of the signal receiver, the transmission parameters of the shielding strip under test are determined by the transmission parameter calculation formula. The formula for calculating the transmission parameters is as follows:

[0007] Among them, S 21 P1 represents the transmission parameters of the shielding strip under test, P2 represents the transmission parameters of the signal transmitter, and P3 represents the reception parameters of the signal receiver.

[0008] Furthermore, the method described above, wherein determining the shielding effectiveness of the shielding strip under test based on the transmission parameters of the shielding strip under test and the transmission parameters when the shielding strip under test is not installed, includes: The lowest resonant frequency of the cavity in the fixing device is calculated according to the formula for calculating the resonant frequency supported by a six-sided lossless rectangular cavity. The center frequency of the transmission parameters is obtained, and when the center frequency is greater than the minimum resonant frequency and the average bandwidth used by the transmission parameters is greater than the preset bandwidth, the number of resonant modes that the cavity in the fixed device can support is calculated using the formula for calculating the number of resonant modes. Based on the number of resonance modes, the average transmission parameters of the shielding strip under test and the average transmission parameters when the shielding strip under test is not installed are calculated using the average transmission parameter calculation formula. The shielding effectiveness of the shielding strip under test is calculated using the shielding effectiveness calculation formula based on the average transmission parameters of the shielding strip under test and the average transmission parameters when the shielding strip under test is not installed.

[0009] Furthermore, in the method described above, the formula for calculating the resonant frequency supported by the six-sided lossless rectangular cavity is as follows:

[0010] Among them, f ijk ε is the resonant frequency supported by the six-sided lossless rectangular cavity, μ is the permeability of the free space in the cavity, ε is the dielectric constant of the free space in the cavity, l, w and h represent the length, width and height of the cavity, respectively, and i, j and k are positive integers, with at most one of them being zero at any given time.

[0011] Furthermore, in the above-described method, the bandwidth used for the frequency averaging of the transmission parameters is greater than a preset bandwidth, including:

[0012] Wherein, BW is the bandwidth used for the frequency average of the transmission parameters, f is the center frequency, and V is the volume of the cavity in the fixed device.

[0013] Furthermore, in the method described above, the formula for calculating the number of resonance modes is:

[0014] Wherein, N is the number of resonance modes that the cavity in the fixing device can support. It is the frequency step size in the received parameters.

[0015] Furthermore, in the method described above, the formula for calculating the average transmission parameters is as follows:

[0016] Among them, <|S 21 | 2 > represents the average transmission parameters of the shielding strip under test, and fi represents the frequency at the i-th point on the bandwidth BW to be determined.

[0017] Furthermore, in the method described above, the formula for calculating the shielding effectiveness is:

[0018] Where SE(dB) represents the shielding effectiveness of the shielding strip under test, <|S' 21 | 2 > represents the average transmission parameters when the shielding strip under test is not installed.

[0019] Furthermore, the methods described above also include: The quality factor of the cavity in the fixing device is calculated using the quality factor calculation formula. The material of the cavity in the fixing device is selected based on the quality factor.

[0020] Furthermore, the methods described above also include: The skin depth of the shielding strip to be tested is calculated according to the skin depth calculation formula. The shielding effectiveness of the shielding strip under test is evaluated based on the skin depth.

[0021] The beneficial effects of this invention are as follows: This application first places the shielding strip under test on a fixing device. The fixing device consists of two adjacent cavities. One cavity houses a signal transmitter, and the other cavity houses a signal receiver. Then, based on the transmission parameters of the signal transmitter and the reception parameters of the signal receiver, the transmission parameters of the shielding strip under test are determined. The shielding strip is then removed, and the transmission parameters without the shielding strip are obtained. Finally, based on the transmission parameters of the shielding strip under test and the transmission parameters without the shielding strip, the shielding effectiveness of the shielding strip under test is determined. In this application, cavity-to-cavity near-field shielding testing allows for convenient inter-frequency evaluation of shielding gaskets within a frequency range up to 40 GHz, offering higher accuracy compared to traditional same-side single-pole probe configurations. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a flowchart of an embodiment of a shielding effectiveness testing method for a shielding strip based on the adjacent cavity method of the opposite probe according to the present invention; Figure 2 This is a schematic diagram of the fixing device structure provided in one embodiment of the shielding effectiveness testing method for a shielding strip based on the adjacent cavity method of the opposite probe of the present invention; Figure 3 This is an electric field distribution diagram inside the test fixture provided in an embodiment of a shielding effectiveness testing method for a shielding strip based on the adjacent cavity method of the opposite probe of the present invention. Figure 4 This is a diagram showing the relationship between frequency and scattering parameters when no shielding strip is present, provided in one embodiment of a shielding effectiveness testing method for a shielding strip based on the adjacent cavity method of the opposite probe according to the present invention. Figure 5 This is an embodiment of the shielding effectiveness testing method for a shielding strip based on the adjacent cavity method of the opposite probe of the present invention, which provides a graph showing the relationship between frequency and scattering parameters when a shielding strip is present. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] Figure 1 This is a flowchart illustrating an embodiment of a shielding effectiveness testing method for a shielding strip based on the adjacent cavity method of a contralateral probe according to the present invention. Please refer to... Figure 1 This embodiment may include the following steps: S1. Place the shielding strip to be tested on the fixing device; wherein the fixing device consists of two adjacent cavities; S2. A signal transmitter is installed in one cavity of the fixing device, and a signal receiver is installed in the other cavity of the fixing device; S3. Determine the transmission parameters of the shielding strip under test based on the transmission parameters of the signal transmitter and the reception parameters of the signal receiver; S4. Remove the shielding strip to be tested and obtain the transmission parameters when the shielding strip to be tested is not installed; S5. Determine the shielding effectiveness of the shielding strip under test based on the transmission parameters of the shielding strip under test and the transmission parameters when the shielding strip under test is not installed.

[0026] Understandably, in this embodiment, the shielding strip under test is first placed on a fixing device. This fixing device consists of two adjacent cavities. One cavity houses a signal transmitter, and the other cavity houses a signal receiver. Then, based on the transmitter's transmission parameters and the receiver's reception parameters, the transmission parameters of the shielding strip under test are determined. The shielding strip is then removed, and the transmission parameters without the strip are obtained. Finally, based on both the transmission parameters of the shielding strip and the parameters without the strip, the shielding effectiveness of the shielding strip is determined. In this embodiment, cavity-to-cavity near-field shielding testing allows for convenient inter-frequency evaluation of shielding gaskets within a frequency range up to 40 GHz, offering higher accuracy compared to traditional same-side single-pole probe configurations.

[0027] In practice, the shielding strip under test can be a sealing gasket. The fixing device used in the cavity-to-cavity test method mainly consists of two adjacent cavities, aiming to evaluate the shielding effectiveness of the sealing gasket under test. Figure 2 As shown. The left side of the testing device mainly consists of two adjacent cavity cover plates of the same size. The sealing gasket to be tested can be fixed along the red lines around the two cavities, as shown. Figure 2 As shown in (a1)-(a4), the right side of the testing device mainly consists of a substrate with two cavities, as shown in... Figure 2As shown in (b1) and (b2). Each cavity has standard threads on the left and right sides of its respective mounting bracket, which allows for the installation of microwave wall panel adapters to secure the monopole antenna within each cavity. The gaskets tested are typically form-in-place (FIP), such as... Figure 2 As shown in (c), it surrounds the cavity and maintains tight contact with the left and right portions of the fixing component. The two parts of the fixing component are secured together via eight screw holes distributed around it and sixteen spacer rings. They are secured with eight M4 screws as shown... Figure 2 They are fastened together as shown in (e).

[0028] Preferably, step S3 includes: Based on the transmission parameters of the signal transmitter and the reception parameters of the signal receiver, the transmission parameters of the shielding strip under test are determined by the transmission parameter calculation formula. The formula for calculating the transmission parameters is as follows:

[0029] Among them, S 21 P1 represents the transmission parameters of the shielding strip under test, P2 represents the transmission parameters of the signal transmitter, and P3 represents the reception parameters of the signal receiver.

[0030] Understandably, cavity-to-cavity testing methods can measure near-field shielding effectiveness to prevent radiated interference between adjacent shielding covers of electronic components mounted on printed circuit boards. Considering the physical limitations imposed by the small cavity size, probes are used to detect the internal electromagnetic fields during transmission and reception. The probes are considered comparable in performance to monopole antennas, with the left needle of the mounting device acting as the signal transmitter and the right needle as the signal receiver. Transmission parameters are acquired to evaluate the shielding effectiveness of the gaskets from one cavity to another, which measures their ability to effectively shield.

[0031] The inter-cavity testing method for determining the coupling strength between two adjacent cavities is based on the transmission parameters measured between two opposing probes.

[0032] (1) Where P1 is the transmission parameter of the signal transmitter, which is radiated into the cavity through a monopole antenna mounted on the microwave wall panel adapter. The electromagnetic radiation is received by monopole antennas in opposite directions in adjacent cavities, obtaining the reception parameter P2.

[0033] The electromagnetic interference shielding effectiveness of the tested gasket is defined as the ratio of the power of the signal receiver without the gasket to the power of the signal receiver with the tested gasket, when the transmission parameter P1 is constant at the signal transmitter.

[0034] (2) S' 21 These are the transmission parameters when the shielding strip under test is not installed.

[0035] Preferably, step S5 includes: Based on the formula for calculating the resonant frequency supported by a six-sided lossless rectangular cavity, calculate the lowest resonant frequency of the cavity in the fixed device. The center frequency of the transmission parameters is obtained, and when the center frequency is greater than the minimum resonant frequency and the bandwidth used by the average frequency of the transmission parameters is greater than the preset bandwidth, the number of resonant modes that the cavity in the fixed device can support is calculated using the formula for calculating the number of resonant modes. Based on the number of resonance modes, the average transmission parameters of the shielding strip under test and the average transmission parameters when the shielding strip under test is not installed are calculated using the average transmission parameter calculation formula. Based on the average transmission parameters of the shielding strip under test and the average transmission parameters when the shielding strip under test is not installed, the shielding effectiveness of the shielding strip under test is calculated using the shielding effectiveness calculation formula.

[0036] Preferably, the formula for calculating the resonant frequency supported by a six-sided lossless rectangular cavity is as follows:

[0037] Among them, f ijk ε is the resonant frequency supported by the six-sided lossless rectangular cavity, μ is the permeability of the free space in the cavity, ε is the dielectric constant of the free space in the cavity, l, w and h represent the length, width and height of the cavity, respectively, and i, j and k are positive integers, with at most one of them being zero at any given time.

[0038] Understandably, to ensure the accuracy of test results between cavities, and given the non-uniformity of electromagnetic field distribution at low frequencies, the lowest operating frequency should be considered. The resonant frequency f supported by a six-sided lossless rectangular cavity... ijk The definition is as follows: (3) Where μ is the permeability of the free space in the cavity (4) ×10 -7 H / m), while ε is the dielectric constant of the free space in the cavity (8.854 × 10⁻⁶). -12 F / m), l, w, and h represent the length, width, and height of the cavity, respectively, all in meters. i, j, and k are positive integers, and at most one of them can be zero at any given time.

[0039] Under ideal conditions, the lowest resonant frequency f 110 The calculation method is as follows: (4) In principle, when the conditions required for resonance are met... This will cause cavity resonance.

[0040] From a statistical perspective, the number of resonance modes that a rectangular cavity can support is: (5) Where f represents the frequency, and c is the speed of light in a vacuum, which is equal to 3 × 10⁻⁶. 8 m / s.

[0041] Preferably, the bandwidth used for averaging the transmission parameters is greater than a preset bandwidth, including:

[0042] Where BW is the bandwidth used for averaging the transmission parameters, f is the center frequency, and V is the volume of the cavity in the fixed device.

[0043] Understandably, BW is the bandwidth used for frequency averaging. To ensure a sufficient number of modes within the cavity, BW should meet the following conditions: (9) Where f is the center frequency and V is the cavity volume. An appropriate bandwidth should be selected during frequency averaging.

[0044] Preferably, the formula for calculating the number of resonance modes is:

[0045] Where N is the number of resonance modes that the cavity in the fixed device can support. It is the frequency step size in the received parameters.

[0046] Preferably, the formula for calculating the average transmission parameters is:

[0047] Among them, <|S 21 | 2 > represents the average transmission parameters of the shielding strip under test, and fi represents the frequency at the i-th point on the bandwidth BW to be determined.

[0048] Preferably, the formula for calculating shielding effectiveness is:

[0049] Where SE(dB) represents the shielding effectiveness of the shielding strip under test, <|S' 21 | 2 >This represents the average transmission parameters without the shielding strip under test installed.

[0050] Understandably, since multiple modes exist within a cavity in a specific frequency band, the electromagnetic shielding effectiveness of the test gasket can be statistically calculated. (6) This represents the average value calculated within a specific frequency bandwidth. The calculation method is as follows: (7) The method for calculating the value of N is as follows: (8) Where BW is the bandwidth used for frequency averaging. It is the frequency step size in data acquisition.

[0051] Preferred options also include: The quality factor of the cavity in the fixed device is calculated using the quality factor calculation formula. Select the material for the cavity in the fixing device based on the quality factor.

[0052] It is understandable that, such as Figure 2 As shown, the left side of the fixture contains two identical adjacent cavities (each with dimensions L3×W3×H3) separated by a width of W6. These cavities have rounded corners with a radius of R1 in the height direction, but otherwise retain the characteristics of rectangular cavities.

[0053] The quality factor Q is defined as the ratio of stored energy to dissipated energy during each oscillation cycle, reflecting the energy loss characteristics of the resonant cavity. This parameter can be calculated using the following formula: (10) Among them, f r It is the minimum resonant frequency of the cavity. It refers to the electrical conductivity of the material.

[0054] For a shielded cavity made of gold-plated copper, its surface penetration depth is 0.733 at a frequency of 11.18 GHz. The quality factor is 1705, a sufficiently high value to handle a large amount of energy. During the measurement process, the test fixture is wrapped with copper shielding tape to prevent electromagnetic leakage between the two parts of the test fixture into the air, thus obtaining more accurate results.

[0055] Preferred options also include: Calculate the skin depth of the shielding strip under test according to the skin depth calculation formula; The shielding effectiveness of the shielding strip under test is evaluated based on skin depth.

[0056] It is understandable that, such as Figure 2 As shown in (d), the washer to be tested is located around the two adjacent cavities indicated by the red line on the left side of the fixture. All eight spacing rings are identical, as shown... Figure 2 (c) shows the left and right parts used to connect the test fixture, with the distance between the two parts fixed at (H8–H5). For the elastic gasket to be tested, such as a positioning gasket, its height H7 can be slightly higher than the distance fixed by (H8–H5) to more accurately simulate actual use conditions, thereby more precisely evaluating its shielding performance. Similarly, its widths W8 and W9 can also be adjusted to suit actual use conditions.

[0057] When an electromagnetic field propagates inside the gasket under test, the concept of skin depth must be considered. Skin depth refers to the distance required for the electric field to decay to 1 / e (approximately 0.368 times its original value), and its calculation formula is as follows: (11) Where μ is the permeability, σ is the conductivity, and f is the frequency. The conductivity of the gasket being tested is typically over 1000 S / m; for simplicity, we assume it to be 1000 S / m. The operating frequency is 0.26 GHz when the skin depth is 1 mm. Conversely, the skin depth is 0.15 mm at the lowest operating frequency of 11.18 GHz. According to formula (11), the skin depth decreases as the frequency increases. Therefore, at the operating frequency, the current and electromagnetic field are confined to a thin area. Given that the gasket material itself can achieve high shielding effectiveness, it is necessary to evaluate the influence of other factors, such as the installation method, through simulation under actual conditions.

[0058] In practical applications, the electric field distribution inside the test fixture (such as...) Figure 3 The results (shown) were simulated at a frequency of 30 GHz. Port 1 serves as the transmitting monopole antenna, while port 2 serves as the receiving monopole antenna. A probe (1.25 mm in diameter and 2 mm in extension, used as a monopole antenna) is mounted on the microwave main adapter. The electric field strength near port 1 (as the excitation source) is significantly higher than that near port 2. Theoretically, the number of resonant modes supported by the cavity can be calculated using Equation 8; statistically, it can also be determined using Equation 5.

[0059] At the lowest operating frequency of 11.18 GHz, the relationship between frequency and scattering parameters is shown in the graph below. Figure 4 and Figure 5 As shown, S11 is -8.292dB and S21 is -4.339dB. Therefore, S21 can be used to determine the minimum operating frequency. The minimum resonant frequency can support various modes within the cavity, and since the value of S21 is not too low, the minimum test frequency is considered appropriate.

[0060] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0061] It should be noted that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.

[0062] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0063] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0064] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0065] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0066] The storage media mentioned above can be read-only memory, disk, or optical disk, etc.

[0067] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0068] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for testing the shielding effectiveness of a shielding strip based on the adjacent cavity method using a contralateral probe, characterized in that, include: The shielding strip to be tested is mounted on a fixing device; wherein the fixing device consists of two adjacent cavities; A signal transmitter is provided in one cavity of the fixing device, and a signal receiver is provided in the other cavity of the fixing device; The transmission parameters of the shielding strip under test are determined based on the transmission parameters of the signal transmitter and the reception parameters of the signal receiver. Remove the shielding strip to be tested and obtain the transmission parameters when the shielding strip to be tested is not installed; The shielding effectiveness of the shielding strip under test is determined based on the transmission parameters of the shielding strip under test and the transmission parameters when the shielding strip under test is not installed.

2. The method according to claim 1, characterized in that, The step of determining the transmission parameters of the shielding strip under test based on the transmission parameters of the signal transmitter and the reception parameters of the signal receiver includes: Based on the transmission parameters of the signal transmitter and the reception parameters of the signal receiver, the transmission parameters of the shielding strip under test are determined by the transmission parameter calculation formula. The formula for calculating the transmission parameters is as follows: Among them, S 21 P1 represents the transmission parameters of the shielding strip under test, P2 represents the transmission parameters of the signal transmitter, and P3 represents the reception parameters of the signal receiver.

3. The method according to claim 2, characterized in that, The step of determining the shielding effectiveness of the shielding strip under test based on the transmission parameters of the shielding strip under test and the transmission parameters when the shielding strip under test is not installed includes: The lowest resonant frequency of the cavity in the fixing device is calculated according to the formula for calculating the resonant frequency supported by a six-sided lossless rectangular cavity. The center frequency of the transmission parameters is obtained, and when the center frequency is greater than the minimum resonant frequency and the average bandwidth used by the transmission parameters is greater than the preset bandwidth, the number of resonant modes that the cavity in the fixed device can support is calculated using the formula for calculating the number of resonant modes. Based on the number of resonance modes, the average transmission parameters of the shielding strip under test and the average transmission parameters when the shielding strip under test is not installed are calculated using the average transmission parameter calculation formula. The shielding effectiveness of the shielding strip under test is calculated using the shielding effectiveness calculation formula based on the average transmission parameters of the shielding strip under test and the average transmission parameters when the shielding strip under test is not installed.

4. The method according to claim 3, characterized in that, The formula for calculating the resonant frequency supported by the six-sided lossless rectangular cavity is as follows: Among them, f ijk ε is the resonant frequency supported by the six-sided lossless rectangular cavity, μ is the permeability of the free space in the cavity, ε is the dielectric constant of the free space in the cavity, l, w and h represent the length, width and height of the cavity, respectively, and i, j and k are positive integers, with at most one of them being zero at any given time.

5. The method according to claim 4, characterized in that, The bandwidth used for the frequency average of the transmission parameters is greater than the preset bandwidth, including: Wherein, BW is the bandwidth used for the frequency average of the transmission parameters, f is the center frequency, and V is the volume of the cavity in the fixed device.

6. The method according to claim 5, characterized in that, The formula for calculating the number of resonance modes is: Wherein, N is the number of resonance modes that the cavity in the fixing device can support. It is the frequency step size in the received parameters.

7. The method according to claim 6, characterized in that, The formula for calculating the average transmission parameters is as follows: Among them, <|S 21 | 2 > represents the average transmission parameters of the shielding strip under test, and fi represents the frequency at the i-th point on the bandwidth BW to be determined.

8. The method according to claim 7, characterized in that, The formula for calculating the shielding effectiveness is: Where SE(dB) represents the shielding effectiveness of the shielding strip under test, <|S' 21 | 2 > represents the average transmission parameters when the shielding strip under test is not installed.

9. The method according to claim 8, characterized in that, Also includes: The quality factor of the cavity in the fixing device is calculated using the quality factor calculation formula. The material of the cavity in the fixing device is selected based on the quality factor.

10. The method according to claim 9, characterized in that, Also includes: The skin depth of the shielding strip to be tested is calculated according to the skin depth calculation formula. The shielding effectiveness of the shielding strip under test is evaluated based on the skin depth.

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