Edge deformation mutual coupling anechoic chamber shielding effectiveness test apparatus and method

Abstract

The present application relates to a kind of boundary deformation mutual coupling reverberation chamber shielding effectiveness test device and method, it is related to electromagnetic shielding technical field of material, the test device includes flexible shielding cloth reverberation chamber, metal plate, stepper motor group, transmitting antenna, first receiving antenna, second receiving antenna, first spectrum analyzer, second spectrum analyzer and controller;Metal plate is as partition and is divided into transmitting reverberation chamber and receiving reverberation chamber by flexible shielding cloth reverberation chamber, metal plate is closely connected with flexible shielding cloth reverberation chamber around;Test window is set in the center of metal plate, for installing test material;Stepper motor group is used to control the wall deformation of transmitting reverberation chamber and receiving reverberation chamber;First spectrum analyzer is connected with first receiving antenna;Second spectrum analyzer is connected with second receiving antenna;Controller is connected with first spectrum analyzer, second spectrum analyzer and stepper motor group.The present application provides platform and method for accurately testing the shielding effectiveness of material under composite electromagnetic environment.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding technology, and in particular to a device and method for testing the shielding effectiveness of a boundary deformation mutual coupling reverberation chamber. Background Technology

[0002] With the increasing number of frequency-using devices, the electromagnetic environment in space is becoming increasingly complex and harsh. This necessitates efficient electromagnetic protection for the electronic modules and components within modern electronic equipment. Using electromagnetic shielding materials to block and attenuate the propagation of electromagnetic waves is a common electromagnetic protection technique. Shielding effectiveness is the core technical indicator for evaluating the electromagnetic protection capability of materials. Most new electromagnetic shielding materials are composite materials. Due to the influence of factors such as the material composite process and the uncertainty of metal doping, numerical simulations often struggle to obtain accurate solutions for the material's shielding effectiveness. Experimental measurement is the preferred technique for accurately assessing the electromagnetic protection capability of materials.

[0003] Commonly used shielding effectiveness tests typically employ a single plane wave perpendicularly irradiating the material surface to obtain its shielding effectiveness. However, materials used for electromagnetic shielding often operate in complex electromagnetic environments with multiple incident directions and polarization modes. Therefore, shielding effectiveness tests should also be conducted in similar complex environments. The reverberation chamber, with its spatially statistically homogeneous, isotropic, and randomly polarized electromagnetic environment, more closely resembles the environment encountered by materials in actual use, making it suitable for testing material shielding effectiveness. The International Electrotechnical Commission (IEC) has proposed... " The shielding effectiveness of a material is tested by nesting a smaller mechanically stirred reverberation chamber inside a larger one, and then mounting the test material on the test window of the smaller mechanically stirred reverberation chamber. ” This method, known as the nested reverberation chamber shielding effectiveness test method, suffers from drawbacks such as complex system structure, limited available frequency bandwidth, and large errors in test results due to an imperfect definition of shielding effectiveness.

[0004] To address this issue, some scholars have proposed a flexible dual-reverberation chamber shielding effectiveness testing method: combining two flexible shielding reverberation chambers through a test window, and using a motor to shake the reverberation chambers to obtain a statistically uniform electromagnetic environment. However, the uniform field environment of the reverberation chamber obtained by shaking results in highly random test results and cannot make the reverberation chamber operate in the standard-approved mode tuning mode; the shielding effectiveness definition method based on the principle of energy conservation leads to an overly cumbersome testing process and inaccurate test results. Therefore, a new shielding effectiveness definition method is needed.

[0005] 1. Traditional shielding effectiveness testing equipment and its shortcomings:

[0006] The traditional shielding effectiveness test device for a reverberation chamber is a small mechanically stirred reverberation chamber installed in a large mechanically stirred reverberation chamber, a test window is arranged on a cavity surface of the small mechanically stirred reverberation chamber, a shielding effectiveness is calculated according to a ratio of received powers of receiving antennas in the large and small mechanically stirred reverberation chambers, and a traditional test device block diagram is shown in Figure 1 .

[0007] The method, although providing a more actual composite electromagnetic environment for material shielding effectiveness test, has the following defects: 1. Two mechanically stirred reverberation chambers are needed, the test device is complex, and especially design and control of the large and small stirrers are technical problems; 2. A volume of the small mechanically stirred reverberation chamber cannot exceed 8% of a volume of the large mechanically stirred reverberation chamber, the volume of the small mechanically stirred reverberation chamber determines a number of internal modes, and the small volume of the small mechanically stirred reverberation chamber means that it is difficult to expand a lower limit of a usable frequency, and further leads to a narrow test bandwidth; 3. The mechanically stirred reverberation chamber is expensive; and the existence of these problems leads to difficulty in popularization and use of the nested reverberation chamber shielding effectiveness test method.

[0008] 2. Existing shielding effectiveness definition method and defects thereof:

[0009] IEC61000-4-21 gives a definition of a reverberation chamber condition shielding effectiveness as a ratio of received powers of receiving antennas in large and small mechanically stirred reverberation chambers.

[0010]

[0011] In the formula, P o，s and P i，s respectively represent received powers of the receiving antennas in the large and small mechanically stirred reverberation chambers.

[0012] However, this definition method has a serious problem, the received power P i，s of the antenna in the small mechanically stirred reverberation chamber is affected by a quality factor of the small mechanically stirred reverberation chamber, leading to a significant deviation of a test result. Figure 2 .

[0013] As can be seen from Figure 2 , at this time, the shielding effectiveness oscillates around 3dB, which is obviously inconsistent with the fact. A test error of about 3dB is caused by the quality factor of the small mechanically stirred reverberation chamber. It can be inferred that the shielding effectiveness value obtained by using the definition method is generally high, and the greater the quality factor of the small mechanically stirred reverberation chamber, the greater the test result error.

[0014] To eliminate the problem of non-zero shielding effectiveness test results for empty windows, the literature [A. Gifuni, M. Migliaccio. Use of nested reverberating chambers to measure shielding effectiveness of nonreciprocal samples taking into account multiple interactions[J]. IEEE transactions on electromagnetic compatibility, 2008, 50(4):783-786.] proposes a new method for defining shielding effectiveness, defining the shielding effectiveness as "the ratio of the antenna received power in the small reverberation chamber before and after placing the test material".

[0015]

[0016] In the formula P i，ns and P i，s These represent the received power of the antenna before and after the test material is installed in the small reverberation chamber test window.

[0017] Obviously, if the test window is not fitted with the test material, then P i，ns With P i，s If they are equal, the test result is 0, which effectively solves the problem of inaccurate results in the empty window test.

[0018] However, this formula is based on the premise that the power density in the large reverberation chamber remains unchanged before and after the test material is installed in the test window.

[0019]

[0020] In formula (3), <P r > is the received power of the high reverberation indoor antenna, S is the power density, A is the equivalent area of ​​the receiving antenna, and P is the power density. t Here, is the transmit power of the large reverberation chamber, and Q is the quality factor of the large reverberation chamber. It can be seen that the power density within the large reverberation chamber depends not only on the input power of the transmitting antenna but also on the quality factor of the large reverberation chamber. However, the quality factor is affected by whether the test material is loaded within the test window of the small reverberation chamber; the loading effect of the test window is discussed in [reference needed]. Figure 3 .

[0021] from Figure 3It can be seen that the average received power of the receiving antenna in the reverberation chamber is affected by the test window loading, and the effect is more obvious as the frequency increases. When the input of the large reverberation chamber remains unchanged, the test window loading of the test material causes the power density inside the large reverberation chamber to increase. Since the premise of formula (2) is that the power density inside the large reverberation chamber is equal before and after the test material is loaded, the loading effect of the test material makes formula (2) inaccurate, and the test result is smaller.

[0022] [C.L. Holloway, D.A. Hill, J. Ladbury, G. Koepke. Shielding effectiveness measurements of materials using nested reverber-ation chambers [J]. IEEE Transactions on Electromagnetic Compatibility, 2003, 45(2): 350-356.] uses the power balance method to propose a new shielding effectiveness definition method, and the calculation formula is

[0023]

[0024] In the formula, P r，in，s and P r，in，ns respectively represent the received power of the antenna in the small reverberation chamber with and without the installation of the test material; P r，o，s and P r，o，ns respectively represent the received power of the antenna in the large reverberation chamber with and without the installation of the test material; P rQ，in，s and P rQ，in，ns respectively represent the received power of the antenna in the small reverberation chamber when the transmitting antenna is placed in the small reverberation chamber with and without the installation of the test material; P tx，in，s and P tx，in，ns respectively represent the transmitting power of the transmitting antenna in the small reverberation chamber with and without the installation of the test material.

[0025] This definition method obtains the shielding effectiveness by measuring 8 parameters in the large and small reverberation chambers. However, this definition method has errors, and the factor is the ratio of the received power of the antenna in the small reverberation chamber with and without the test material, and the factor is the ratio of the received power of the antenna in the small reverberation chamber when the transmitting antenna is placed in the small reverberation chamber with and without the test material, has included the test error caused by the loading of the test material, The existence of the factor The ratio of input power in the small reverberation chamber is generally simplified as 1. The definition method needs to place the transmitting antenna in the small reverberation chamber respectively, and test the power of the receiving antenna and the power of the transmitting antenna before and after the installation of the test material, which is very tedious.

[0026] The shielding effectiveness of a certain material obtained by the above three shielding effectiveness definition methods is shown in the following table. Figure 4

[0027] From Figure 4 It can be seen that the overall trend of the shielding effectiveness obtained by different methods is consistent, but the fluctuation of formula (2) and formula (4) is large, especially at the frequency point of 6GHz, the test results of the two definition methods differ by about 30dB. According to the above analysis, the result of formula (1) is larger, the result of formula (2) is smaller, and the test result of formula (4) is larger than that of formula (1), so it is also verified that the definition method has an error. SUMMARY

[0028] The purpose of the present application is to provide a boundary deformation mutual coupling reverberation chamber shielding effectiveness testing device and method, which provides a platform and method for accurately testing the shielding effectiveness of materials in a complex electromagnetic environment.

[0029] To achieve the above purpose, the present application provides the following scheme:

[0030] A boundary deformation mutual coupling reverberation chamber shielding effectiveness testing device, comprising: a flexible shielding cloth reverberation chamber, a metal plate, a stepping motor set, a transmitting antenna, a first receiving antenna, a second receiving antenna, a first spectrum analyzer, a second spectrum analyzer and a controller.

[0031] The metal plate serves as a partition to divide the flexible shielding cloth reverberation chamber into a transmitting reverberation chamber and a receiving reverberation chamber, and the metal plate is tightly connected with the flexible shielding cloth reverberation chamber around.

[0032] A test window is provided in the center of the metal plate for installing a test material, and the test material is electrically connected with the metal plate.

[0033] The stepping motor set is used to control the deformation of the walls of the transmitting reverberation chamber and the receiving reverberation chamber.

[0034] The transmitting antenna and the first receiving antenna are placed in the transmitting reverberation chamber.

[0035] The second receiving antenna is placed in the receiving reverberation chamber.

[0036] The first spectrum analyzer is connected with the first receiving antenna.

[0037] The second spectrum analyzer is connected with the second receiving antenna. ​

[0038] The controller is connected with the first spectrum analyzer, the second spectrum analyzer and the stepper motor group.

[0039] Optionally, the stepper motor group includes six stepper motors in orthogonal directions, and the transmitting reverberation chamber and the receiving reverberation chamber are both driven by three stepper motors in orthogonal directions.

[0040] The stepper motor reciprocates along the normal direction of the surface of the cavity connected therewith.

[0041] Optionally, the stroke and the moving speed of the stepper motor are adjustable.

[0042] Optionally, the test window is square or circular.

[0043] Optionally, the transmitting antenna and the first receiving antenna are two double-ridge broadband horn antennas.

[0044] Optionally, the second receiving antenna is one horn antenna.

[0045] Optionally, the first receiving antenna is placed inside the transmitting reverberation chamber at any position with a distance from the cavity boundary greater than or equal to 1 / 4 of the wavelength of the test frequency.

[0046] Optionally, the second receiving antenna is placed inside the receiving reverberation chamber at any position with a distance from the cavity boundary greater than or equal to 1 / 4 of the wavelength of the test frequency.

[0047] A method for testing the shielding effectiveness of a boundary deformation mutual coupling reverberation chamber, comprising:

[0048] Setting the stroke and the moving speed of the six stepper motors to determine the deformation state of the mutual coupling reverberation chamber;

[0049] Setting the range of the output frequency, the frequency interval and the signal amplitude of the signal source;

[0050] Adjusting the gain of the power amplifier according to the signal strength in the reverberation chamber;

[0051] Setting the sweep bandwidth and the resolution bandwidth of the first spectrum analyzer and the second spectrum analyzer;

[0052] Installing the test material in the test window to ensure that there is no electromagnetic leakage between the test material and the test window;

[0053] Testing the receiving power of the antenna in the transmitting reverberation chamber and the receiving power of the antenna in the receiving reverberation chamber;

[0054] Removing the test material;

[0055] Testing the receiving power of the antenna in the transmitting reverberation chamber and the receiving power of the antenna in the receiving reverberation chamber when the test window is empty;

[0056] The shielding effectiveness of the test material is calculated using the formula o，s P is the power received by the transmitting antenna in the anechoic chamber after the test material is installed, i，s P is the power received by the receiving antenna in the anechoic chamber after the test material is installed, o，ns P is the power received by the transmitting antenna in the anechoic chamber after the test material is removed, i，ns P is the power received by the receiving antenna in the anechoic chamber after the test material is removed.

[0057] According to the specific embodiments provided by the present application, the following technical effects are achieved:

[0058] (1) The boundary deformation shielding cloth anechoic chamber is used to replace the traditional mechanical stirring anechoic chamber, the test device is simplified, and the cost is also reduced.

[0059] (2) The mutual coupling anechoic chamber is used to replace the nested anechoic chamber, the volume of the mutual coupling anechoic chamber can be the same, and a large anechoic chamber is not needed, because the small anechoic chamber determines the lower limit of the available test frequency, and the mutual coupling anechoic chamber widens the test frequency band.

[0060] (3) A large flexible shielding cloth anechoic chamber is first made, and then a metal plate is used as a partition to divide the large anechoic chamber made of shielding cloth into two, and the shielding cloth and the metal plate are fixed around to ensure no electromagnetic leakage, thereby forming two flexible shielding cloth anechoic chambers. The two anechoic chambers share a metal plate as a wall, which solves the problem of good electrical connection between the mutual coupling anechoic chambers. The problem of good electrical connection between the mutual coupling anechoic chambers is a difficult point and has a high cost.

[0061] (4) The step motor drives the surface deformation of the cavity, instead of the step motor driving the whole anechoic chamber to shake, so that the anechoic chamber can work in the mode of simulated stirring and in the mode of simulated tuning.

[0062] (5) The test device is simple, cheap, has multiple working modes, and is easy to use and promote. DETAILED DESCRIPTION

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0064] Figure 1 It is a block diagram of the shielding effectiveness test device of the nested anechoic chamber method in the prior art;

[0065] Figure 2 ​Diagram for shielding effectiveness test for empty window;

[0066] Figure 3 Diagram for loading effect for test window;

[0067] Figure 4 Diagram for shielding effectiveness test result of material;

[0068] Figure 5 Diagram for shielding effectiveness test device of boundary deformation mutual coupling reverberation chamber of the present application;

[0069] Figure 6 Diagram for dynamic range of test device;

[0070] Figure 7 Diagram for electric field distribution uniformity of transmitting reverberation chamber;

[0071] Figure 8 Diagram for electric field distribution uniformity of receiving reverberation chamber;

[0072] Figure 9 Diagram for comparison of test results of different definition methods;

[0073] Figure 10 Diagram for repeatability of test results of new definition method. DETAILED DESCRIPTION

[0074] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0075] The purpose of the present application is to provide a shielding effectiveness test device and method of boundary deformation mutual coupling reverberation chamber, which improves the existing test device and method, and provides a platform and method basis for accurately testing the shielding effectiveness of materials in a complex electromagnetic environment.

[0076] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0077] 1. Construction of boundary deformation mutual coupling reverberation chamber

[0078] The block diagram of the shielding effectiveness test device of the boundary deformation mutual coupling reverberation chamber of the present application is shown in Figure 5 .

[0079] Firstly, a large flexible shielding cloth reverberation chamber is made, and then a metal plate is used as a partition to divide the large reverberation chamber made of shielding cloth into two flexible shielding cloth reverberation chambers, and the shielding cloth is tightly connected with the metal plate around to ensure no electromagnetic leakage.

[0080] In the two flexible shielding cloth reverberation chambers, any one is used as a transmitting reverberation chamber and the other is used as a receiving reverberation chamber, and the two flexible shielding cloth reverberation chambers share a metal plate as a wall, so that the problem of good electrical connection between the mutually coupled reverberation chambers is solved. Electromagnetic energy is transmitted from the transmitting reverberation chamber to the receiving reverberation chamber through a test window on the shared metal plate.

[0081] The transmitting reverberation chamber and the receiving reverberation chamber are both driven by three orthogonal step motors to deform the wall. The three step motors of the transmitting reverberation chamber are controlled by a first motor controller, and the three step motors of the receiving reverberation chamber are controlled by a second motor controller. Each step motor reciprocates along the normal direction of the surface of the connected cavity, and the stroke and speed of the step motor are adjustable, so that the reverberation chamber can work in a mode of mode tuning. Since no mechanical stirrer needs to be placed inside the reverberation chamber, and the shell is made of shielding cloth, the production is simple and the cost is extremely low, only one percent of the cost of a metal reverberation chamber of the same volume.

[0082] A test window is arranged in the center of the shared metal plate, which can be square or circular, and preferably a square test window of 60cm*60cm. During testing, the test material is installed on the test window and is in good electrical contact with the test window.

[0083] Two double-ridge broadband horn antennas are used inside the transmitting reverberation chamber as a radiation antenna and a first receiving antenna, and one horn antenna is used inside the receiving reverberation chamber as a second receiving antenna. The transmitting antenna is placed in a corner of the reverberation chamber, and the first receiving antenna and the second receiving antenna are placed at any position inside the reverberation chamber within a distance greater than or equal to 1 / 4 wavelength (corresponding to the test frequency) from the cavity boundary.

[0084] The first receiving antenna and the second receiving antenna are respectively connected with a first spectrum analyzer and a second spectrum analyzer outside.

[0085] Specifically, the functions of each component in the device of the present application are as follows:

[0086] Transmitting antenna: radiate radio frequency electromagnetic waves through the driving of a high-power radio frequency amplifier.

[0087] First receiving antenna: receive electromagnetic wave signals in the transmitting reverberation chamber and transmit them to the first spectrum analyzer.

[0088] Second receiving antenna: receive electromagnetic wave signals in the receiving reverberation chamber and transmit them to the second spectrum analyzer.

[0089] Directional coupler and power meter: used together to monitor the power of the power amplifier output to the reverberation chamber antenna and the reflected power of the antenna in real time.

[0090] Power amplifier: amplify the small power signal output by the signal source into a large power signal to the transmitting antenna.

[0091] RF signal source: generate electromagnetic signals of certain frequency required for reverberation chamber testing, signal frequency, modulation mode, amplitude controlled by computer.

[0092] First spectrum analyzer: record the signal strength received by the first antenna in the frequency domain.

[0093] Second spectrum analyzer: record the signal strength received by the second antenna in the frequency domain.

[0094] First motor controller: control the movement of the step motor connected to the three walls of the transmitting reverberation chamber, thereby driving the wall deformation.

[0095] Second motor controller: control the movement of the step motor connected to the three walls of the receiving reverberation chamber, thereby driving the wall deformation.

[0096] 2. Correction method for shielding effectiveness definition based on window loading effect

[0097] The overall logic of the method is as follows:

[0098] Step 1: According to existing literature research, the shielding effectiveness is defined as the ratio of the received power of the antenna in the small reverberation chamber before and after placing the test material

[0099]

[0100] In the formula, P i，ns and P i，s represent the received power of the antenna before and after the test material is installed in the test window of the small reverberation chamber.

[0101] Step 2: Based on the shielding effectiveness definition formula in step 1, normalize the received power of the antenna in the reverberation chamber, and introduce the quality factor of the large reverberation chamber to correct the shielding effectiveness expression formula.

[0102] Formula (2) is the most clear in physical meaning, the main problem is that the external electromagnetic radiation before and after placing the test material is not consistent, that is, P i，ns and P i，s The corresponding power density in the large reverberation chamber changes, the main reason for the change is that the test window covered material changes the quality factor of the large reverberation chamber, resulting in a drift in the power density inside the large reverberation chamber under the same input power, so the power density in the large reverberation chamber needs to be normalized.

[0103] Step 3: Since the received power of the antenna in the reverberation chamber is equal to the product of the power density and the equivalent area of the antenna, the normalization of the power density is converted to the normalization of the received power of the antenna.

[0104] Step 4: Normalize P i，ns and P i，s in the shielding effectiveness calculation formula.

[0105]

[0106] where Q is the quality factor of the reverberation chamber, P t and P r represent the input power and the average received power, respectively, V is the volume of the reverberation chamber, and λ is the wavelength.

[0107] After installing the test material in the small reverberation chamber, the input power of the large reverberation chamber is P i，ns and P i，s , and the received power of the antenna in the large reverberation chamber is

[0108]

[0109]

[0110] It can be seen that P o，ns and P o，s are proportional to the quality factor of the large reverberation chamber.

[0111] Step 5: Assuming that the input power of the large reverberation chamber remains unchanged, then

[0112]

[0113] Therefore, the shielding effectiveness calculation formula can be converted to

[0114]

[0115] where P o，s and P i，s represent the received power of the antenna in the large and small reverberation chambers after installing the test material, respectively; P o，ns and P i，ns represent the received power of the antenna in the large and small reverberation chambers before installing the test material, respectively. Corresponding to the mutual coupling reverberation chamber, P o，s and P i，s represent the received power of the antenna in the transmitting and receiving reverberation chambers after installing the test material, respectively; P o，ns and P i，ns represent the received power of the antenna in the transmitting and receiving reverberation chambers before installing the test material, respectively.

[0116] The first factor in formula (9) The second factor is equivalent to formula (1) The shielding effectiveness of the receiving reverberation chamber without the test material installed is the loading effect of the shielding effectiveness test device. The corrected formula is equal to formula (1) minus the error brought by the test device.

[0117] Step 6: Write formula (9) as follows:

[0118]

[0119] The first factor is equivalent to formula (2) The second factor is equivalent to formula (1) Reflects the change in the quality factor of the transmitting reverberation chamber before and after the test material is installed, which is a correction for the loading effect.

[0120] 3. Test method for the shielding effectiveness of a boundary deformation mutual coupling reverberation chamber

[0121] Before testing, first ensure that the electromagnetic environment inside the reverberation chamber is spatially statistically uniform, then test the receiving power of the antennas inside the transmitting and receiving reverberation chambers before and after the test material is installed, and then calculate the shielding effectiveness of the material according to formula (9) or (10).

[0122] The material shielding effectiveness test process is as follows:

[0123] Parameter setting before testing: Set the stroke and running speed of the 6 stepper motors to determine the deformation state of the mutual coupling reverberation chamber.

[0124] Set the range of the signal source output frequency, the frequency interval, and the signal amplitude.

[0125] Adjust the power amplifier to an appropriate gain to ensure that the signal strength inside the reverberation chamber is moderate.

[0126] Set the sweep bandwidth of the spectrum analyzer to 100 kHz and the resolution bandwidth to 100 Hz to ensure that the test data is accurate and reliable.

[0127] Install the test material in the test window to ensure that there is no electromagnetic leakage between the test material and the test window. First, the signal source outputs the starting frequency, and the first and second spectrum analyzers read the receiving power of the antennas inside the transmitting and receiving reverberation chambers at fixed intervals, respectively, and read 12 data; then change the next test frequency according to the frequency step set in advance, repeat the above test process until all frequencies are tested.

[0128] The test material is removed, and the test window is empty. First, the signal source outputs the initial frequency, and the first spectrum analyzer and the second spectrum analyzer read the received power of the internal antennas of the transmitting reverberation chamber and the receiving reverberation chamber at fixed time intervals, and 12 data are read. Then, the next test frequency is changed according to the frequency step set in advance, and the above test process is repeated until all frequencies are tested.

[0129] After the test is completed, the data is saved and the test device is turned off, and the shielding effectiveness of the test material is calculated according to formula (9) or (10).

[0130] Embodiment:

[0131] The boundary deformation mutual coupling reverberation chamber shielding effectiveness test device is developed based on the technical concept of the application. The geometric size of the two reverberation chambers is 1.6m x 1.2m x 1m, and the lowest available frequency is about 650MHz. Due to the limitation of the test device hardware, the test frequency range is set to 1GHz-10GHz, and the step is 250MHz.

[0132] Before starting the test, the dynamic range of the system needs to be obtained to ensure that the test data is reliable.

[0133] Then start the test, and the dynamic range of the shielding effectiveness test device is as shown in Figure 6 .

[0134] From Figure 6 , it can be seen that the dynamic range of the system gradually decreases from 90dB to about 60dB in the frequency range of 1GHz-10GHz. Configuring a high-power power amplifier to increase the input power, or using a receiver or spectrum analyzer with higher precision, a larger dynamic range can be obtained.

[0135] Figure 7 and Figure 8 are the spatial electric field uniformities of the system obtained by testing. The results are obtained by testing the electric field intensity at 8 vertex positions of the test area, and then calculating according to the standard tolerance calculation method of the reverberation chamber. It can be seen that the electric field standard deviations of the transmitting reverberation chamber and the receiving reverberation chamber in the test frequency range are both less than 3dB, fully meeting the requirements of the uniformity of the reverberation chamber, and can be used for shielding effectiveness test.

[0136] Figure 9 is the experimental result obtained by using the shielding effectiveness definition correction method proposed in the application. In the entire test frequency range, the test result is relatively stable, and the fluctuation rate is much smaller than the calculation result using formula (2), and is basically comparable to formula (1). In most frequency points, the test result is less than formula (1) and greater than formula (2), which is relatively reasonable.

[0137] Figure 10The test repeatability is obtained by using the newly defined method, wherein the positions of the receiving antennas in the two anechoic chambers are changed in Experiment 1 to Experiment 4, and the receiving antenna position is consistent with that in Experiment 1, but the anechoic chamber shape change amplitude and motor running speed are adjusted. From the test results, the repeatability of the data of the five experiments is good, and the deviation of different test results is large at 1.5 GHz and 2.5 GHz frequency points, and the maximum is 5.7 dB.

[0138] To quantify the repeatability of the test results of the five times, the coefficient of variation is used to reflect the dispersion degree of the test data, which is defined as the ratio of the standard deviation to the average value of the test data. Table 1 is the repeatability test data of the shielding effectiveness.

[0139] Table 1 Shielding effectiveness repeatability test results

[0140]

[0141] According to Table 1, the average shielding effectiveness fluctuates between 28 dB and 34 dB in the test frequency range, and the result stability is good; the maximum standard deviation of different groups of test data is 1.24 dB, and the coefficient of variation is also less than 4%, which indicates that the test result repeatability is very good.

[0142] However, due to the test data is interval 1GHz, the 1.5GHz and 2.5GHz two frequency points fluctuate relatively large in the Figure 10 After calculation, the average value of 1.5GHz is 38.53dB, the standard deviation is 1.61dB, and the coefficient of variation is 4.18%; the average value of 2.5GHz is 24.31dB, the standard deviation is 1.96dB, and the coefficient of variation is 8.05%. All the data reflect that the test result has good repeatability.

[0143] The present application also discloses the following technical effects:

[0144] Regarding the test device:

[0145] (1) The anechoic chamber with boundary deformation shielding cloth is used instead of the traditional mechanical stirring anechoic chamber, the test device is simplified, and the cost is also reduced.

[0146] (2) The mutual coupling anechoic chamber is used instead of the nested anechoic chamber, the volume of the mutual coupling anechoic chamber can be as large, and a large anechoic chamber is not needed, because the small anechoic chamber determines the lower limit of the available test frequency, and the mutual coupling anechoic chamber widens the test frequency band.

[0147] (3) A metal plate is used as a partition to divide the large anechoic chamber made of shielding cloth into two, so that the two anechoic chambers share a metal plate as a wall, which solves the problem of good electrical connection between the mutual coupling anechoic chambers.

[0148] (4) The shielding cloth is tightly connected with the metal plate around, no electromagnetic leakage, and two flexible shielding cloth reverberation chambers are formed, and the problem of good electrical bonding of the mutual coupling reverberation chamber is solved.

[0149] (5) The stepping motor drives the surface deformation of the cavity, instead of the stepping motor driving the whole reverberation chamber to shake, so that the reverberation chamber can work in the mode of mode stirring and mode tuning, and especially some domestic and international standards only recognize the mode tuning mode, for example: aviation standard RTCA DO-160G 'environmental conditions and test procedures for airborne equipment', domestic standard GJB151B-2013'military equipment and subsystem electromagnetic emission and sensitivity requirements and measurement'.

[0150] Summary: The test device is simple, the cost is low, the working mode is multiple, and the use is easy to promote.

[0151] Regarding the definition method:

[0152] The traditional definition method (1) is simple to test, but the result is large. The traditional definition method (2) is generally complex in test procedure, but the result is small, and the result fluctuation is large. The traditional definition method (3) is particularly complex in test procedure, the result is large, and the test result fluctuation is large. The test procedure of the method of the application is equivalent to the definition method (2), the test result is relatively stable, the repeatability is good, the data is smaller than the definition method (1) and larger than the definition method (2), and meets the expected idea.

[0153] Summary: The test result is relatively stable, the repeatability is good, and the test value meets the expected idea.

[0154] Regarding the test method:

[0155] According to the new definition method, the test method is proposed, and four data need to be tested. The test method of the definition method (1) only needs to be tested once, and two parameters are needed. The test method of the definition method (2) needs to be tested twice, and two parameters are needed. Compared with the test method of the definition method (1), the new definition method needs to configure the same equipment, but needs to be tested before and after the installation of the test material. Compared with the test method of the definition method (2), the new definition method needs to place an additional receiving antenna in the transmitting reverberation chamber, and the test procedure is the same, and two additional parameters need to be recorded.

[0156] Summary: The test method is relatively simple, and the required instrument equipment is not much.

[0157] In the specification, each embodiment is described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other.

[0158] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In conclusion, the content of the present specification should not be understood as the limitation of the present application.

Claims

1. A test device for the shielding effectiveness of a boundary deformation mutually coupled reverberation chamber, characterized in that, include: The reverberation chamber is made of flexible shielding cloth, metal plate, stepper motor assembly, transmitting antenna, first receiving antenna, second receiving antenna, first spectrum analyzer, second spectrum analyzer and controller; The metal plate serves as a partition, dividing the flexible shielding cloth reverberation chamber into a transmitting reverberation chamber and a receiving reverberation chamber. The metal plate is tightly connected to the perimeter of the flexible shielding cloth reverberation chamber. The metal plate has a test window at its center for mounting the test material; the test material is electrically connected to the metal plate. The stepper motor assembly is used to control the wall deformation of the transmitting reverberation chamber and the receiving reverberation chamber; The transmitting antenna and the first receiving antenna are placed inside the transmitting reverberation chamber; The second receiving antenna is placed inside the receiving reverberation chamber; The first spectrum analyzer is connected to the first receiving antenna; The second spectrum analyzer is connected to the second receiving antenna; The controller is connected to the first spectrum analyzer, the second spectrum analyzer, and the stepper motor assembly.

2. The boundary deformation mutual coupling reverberation chamber shielding effectiveness testing device according to claim 1, characterized in that, The stepper motor assembly includes six stepper motors in orthogonal directions, and the wall deformation of both the transmitting reverberation chamber and the receiving reverberation chamber is driven by three orthogonal stepper motors.

3. The boundary deformation mutual coupling reverberation chamber shielding effectiveness testing device according to claim 2, characterized in that, The stepper motor reciprocates along the normal direction of the surface of the cavity it is connected to.

4. The boundary deformation mutual coupling reverberation chamber shielding effectiveness testing device according to claim 2 or 3, characterized in that, The stepper motor's stroke and speed are adjustable.

5. The boundary deformation mutual coupling reverberation chamber shielding effectiveness testing device according to claim 1, characterized in that, The test window can be square or circular.

6. The boundary deformation mutual coupling reverberation chamber shielding effectiveness testing device according to claim 1, characterized in that, The transmitting antenna and the first receiving antenna are two dual-ridge broadband horn antennas.

7. The boundary deformation mutual coupling reverberation chamber shielding effectiveness testing device according to claim 1, characterized in that, The second receiving antenna is a horn antenna.

8. The boundary deformation mutual coupling reverberation chamber shielding effectiveness testing device according to claim 1, characterized in that, The first receiving antenna is placed at any position inside the transmitting reverberation chamber at a distance greater than or equal to 1 / 4 of the test frequency wavelength from the cavity boundary.

9. The boundary deformation mutual coupling reverberation chamber shielding effectiveness testing device according to claim 1, characterized in that, The second receiving antenna is placed at any position inside the receiving reverberation chamber at a distance greater than or equal to 1 / 4 of the test frequency wavelength from the cavity boundary.

10. A method for testing the shielding effectiveness of a boundary deformation mutually coupled reverberation chamber, characterized in that, The boundary deformation mutual coupling reverberation chamber shielding effectiveness testing method is applied to the boundary deformation mutual coupling reverberation chamber shielding effectiveness testing device according to any one of claims 1-9, comprising: Set the stroke and running speed of six stepper motors to determine the deformation state of the intercoupled reverberation chamber; Set the range, frequency interval, and signal amplitude of the signal source output frequency; Adjust the power amplifier gain according to the signal strength in the reverberation chamber; Set the sweep bandwidth and resolution bandwidth of the first and second spectrum analyzers; Install the test material in the test window and ensure that there is no electromagnetic leakage between the test material and the test window; Test the received power of the transmitting reverberant indoor antenna and the received power of the receiving reverberant indoor antenna; Remove the test materials; The test window was empty when the received power of the transmitting reverberant indoor antenna and the received power of the receiving reverberant indoor antenna were tested. Using formula Calculate the shielding effectiveness of the test material, where SE is the shielding effectiveness of the test material, and P is the shielding effectiveness of the test material. o,s To determine the received power of the reverberation chamber antenna after the test material is installed, P i,s To receive the received power of the reverberation chamber antenna after the test material is installed, P o,ns To determine the received antenna power in the reverberation chamber after the test material is removed, P i,ns The received power of the reverberation chamber antenna was obtained after the test material was removed.

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