Test method for total scattering cross section of reverberation chamber stirrer based on mirror principle and application

Abstract

The present application relates to the technical field of microwave measurement and reverberation chamber, and particularly relates to a test model of total scattering cross section of a reverberation chamber stirrer based on mirror principle and application, comprising: constructing a mirror model, and obtaining the number of mirror objects after multiple reflections and the total surface area of the mirror model; obtaining the time constant of the reverberation chamber; obtaining the damping time constant of the stirrer; and constructing the test model of the total scattering cross section of the reverberation chamber stirrer. The present application directly reflects the propagation mechanism of electromagnetic waves in the reverberation chamber and the scattering characteristics of the stirrer on the electromagnetic waves, has a certain guiding effect on the optimization of the stirrer and the test configuration, helps to understand, analyze and reduce the un-stirred energy in the reverberation chamber, and finally realizes the effective improvement of the performance of the reverberation chamber.

Description

Technical Field

[0001] This invention relates to the fields of microwave measurement and reverberation chamber technology, specifically to a test model and application of the total scattering cross section of a reverberation chamber stirrer based on the mirror principle. Background Technology

[0002] A microwave reverberation chamber is a high-quality-factor metallic resonant cavity, typically containing one or more irregularly shaped metal stirrers. By rotating these stirrers, the electromagnetic field within its operating area exhibits statistically uniform, isotropic, and randomly polarized physical properties. Reverberation chambers offer advantages such as low construction cost and large test space, and can excite high ambient field strength with relatively low input power. Therefore, they are widely used in electromagnetic compatibility (EMC) testing, especially for high-intensity radiated field testing of electrical and electronic systems and equipment. In recent years, reverberation chamber technology has rapidly expanded into the air interface testing field due to its flexible and efficient testing methods and excellent wireless channel reproduction capabilities. The Wireless Communications and Internet Society (WCSIS) recognized reverberation chambers as a standardized air interface testing technology for large-size devices in 2016, and subsequently as a standardized air interface testing technology for single-input single-output (SIO) systems in 2022. The development of relevant standards for reverberation chambers reflects the consensus reached regarding their application in EMC and air interface testing.

[0003] The uniformity of the electromagnetic field within a reverberation chamber is statistically determined; the more independent samples, the more ideal the statistical characteristics and the better the field uniformity. Currently, reverberation chamber testing primarily obtains independent sample numbers through three stirring methods: mechanical stirring, source stirring, and frequency stirring. Mechanical stirring alters the boundary conditions of the electromagnetic field by rotating the stirrer; frequency stirring reuses electromagnetic modes within a specific frequency band through post-processing of experimental data; and source stirring achieves the excitation of multiple electromagnetic modes by changing the position, direction, and polarization of the excitation source. The effectiveness of the stirring method directly determines the reliability and accuracy of reverberation chamber testing; therefore, effectively evaluating the performance of stirring techniques is a crucial research direction in the field of reverberation chambers. Given that mechanical stirring is the most commonly used stirring method in reverberation chamber testing, and the stirrer is a representative scatterer within the reverberation chamber, effective stirrer performance evaluation methods are essential for the implementation and optimization of reverberation chamber testing.

[0004] Currently, there are three main evaluation metrics for reverberation chamber stirrers: independent sample count, field uniformity, and total scattering cross section (TSS). Independent sample count and field uniformity are measurements of electric field or scattering parameters obtained through statistical theory analysis, without considering the stirrer's operating characteristics (unlike source stirring and frequency stirring methods). While independent sample count and field uniformity can serve as general indicators for evaluating stirring technology, they fail to reflect the true operating characteristics of the stirrer and cannot guide its optimal design. The scattering cross section of an object is defined as the ratio of scattered energy to incident power density. Given the statistically uniform characteristics of the electromagnetic field in a reverberation chamber, the concept of TSS is commonly used in the reverberation chamber field. The TSS of a stirrer directly reflects its ability to scatter electromagnetic waves from different directions and polarization states, and it is a characteristic quantity of the stirrer's own structure, not sensitive to the excitation location, radiation pattern, or whether the cavity is loaded. Therefore, the TSS of a stirrer is an effective parameter for measuring its performance.

[0005] However, in existing technologies, the total scattering cross section of the stirrer is mainly determined by calculating the damping time constant. This method considers the attenuation characteristics of both unstirred energy and total average energy in the reverberation chamber, extracting the damping time constant based on the attenuation rate of the ratio of unstirred energy to total average energy, and thus determining the total scattering cross section of the stirrer. This method cannot intuitively reflect the propagation mechanism of electromagnetic waves in the reverberation chamber, nor the interaction mechanism between the stirrer and electromagnetic waves. Therefore, it is difficult to support the critical needs in the reverberation chamber field for improving stirrer performance, optimizing test configurations, and reducing unstirred energy.

[0006] Therefore, it is necessary to provide a test model and application for the total scattering cross section of a reverberation chamber stirrer based on the mirror principle to solve the above problems. Summary of the Invention

[0007] This invention provides a test model and application for the total scattering cross section of a reverberation chamber stirrer based on the mirror principle. By establishing a test model for the total scattering cross section of the reverberation chamber stirrer according to the specified reverberation chamber test environment and stirrer characteristics, the accurate measurement of the total scattering cross section of the stirrer can be achieved, thereby solving existing problems.

[0008] The test model for the total scattering cross section of a reverberation chamber stirrer based on the mirror principle of the present invention adopts the following technical solution, including:

[0009] Based on the mirror principle, a mirror model of the reverberation chamber test system is established, and the number of mirror objects after multiple reflections and the total surface area of ​​the mirror model are obtained.

[0010] All losses within the reverberation chamber system are equivalent to the losses of the reverberation chamber cavity wall, and the electric field strength of the electromagnetic wave after multiple reflections is obtained based on the initial electric field strength.

[0011] The first electric field energy in the reverberation chamber after multiple reflections of electromagnetic waves is obtained based on the electric field strength after multiple reflections, the initial electric field energy, the number of mirror objects after multiple reflections, and the total surface area of ​​the mirror model.

[0012] Based on typical distances, average reflection coefficients for all incident directions and polarization states, and the first electric field energy in the reverberation chamber after multiple reflections of electromagnetic waves, the time constant of the reverberation chamber is obtained.

[0013] Based on the surface area inside the reverberation chamber and the total scattering cross section of the stirrer, the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections is obtained.

[0014] Based on the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections, the electric field strength after multiple reflections, the initial electric field energy, the number of mirror objects after multiple reflections, and the total surface area of ​​the mirror model, the second electric field energy in the reverberation chamber after multiple reflections of the electromagnetic wave is obtained.

[0015] Based on the time constant of the reverberation chamber and the energy of the second electric field in the reverberation chamber that was not scattered by the stirrer after multiple reflections of the electromagnetic wave, the damping time constant of the stirrer is obtained.

[0016] Based on the damping time constant of the stirrer, the typical distance, and the surface area inside the reverberation chamber, a test model of the total scattering cross section of the stirrer in the reverberation chamber is constructed. The typical distance is the average propagation distance between reflection points of the electromagnetic wave during the entire reflection process.

[0017] Preferably, the expression for the electric field strength of the electromagnetic wave after multiple reflections is:

[0018]

[0019] In the formula, Indicates the passage of electromagnetic waves Electric field strength after secondary reflection; Indicates the initial electric field strength; This represents the average reflection coefficient under all incident directions and polarization states.

[0020] Preferably, the expression for the energy of the first electric field in the reverberation chamber after multiple reflections of the electromagnetic wave is:

[0021]

[0022] In the formula, Indicates the propagation time of electromagnetic waves Internal Path The energy of the first electric field in the reverberation chamber after the second reflection; Indicates the passage of electromagnetic waves The energy of the first electric field in the reverberation chamber after the second reflection; This represents the initial electric field energy; Represents the speed of light; This represents the typical distance, which is the average propagation distance between reflection points during the entire reflection process of the electromagnetic wave; Represents the natural logarithm operation; Indicates the passage of electromagnetic waves The propagation time of the second reflection; This represents the average reflection coefficient under all incident directions and polarization states; Indicates the initial electric field strength; Indicates the process Number of mirrored objects after secondary reflection; Indicates the process The total surface area of ​​the mirror model after secondary reflection.

[0023] Preferably, the time constant of the reverberation chamber satisfies the expression:

[0024]

[0025] In the formula, Indicates the time constant of the reverberation chamber; Represents the speed of light; This represents the typical distance, which is the average propagation distance between reflection points during the entire reflection process of the electromagnetic wave; This represents the average reflection coefficient under all incident directions and polarization states.

[0026] Preferably, the expression for the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections is:

[0027]

[0028] In the formula, Indicates the passage of electromagnetic waves The probability that the secondary reflection is not scattered by the stirrer; This represents the probability that an electromagnetic wave is scattered by the stirrer after zero reflections. Indicates the electromagnetic wave passing through the first The probability of being scattered by the stirrer after the second reflection; This represents the total scattering cross section of the stirrer; This indicates the surface area inside the reverberation chamber.

[0029] Preferably, the expression for the energy of the second electric field in the reverberation chamber that is not scattered by the stirrer after multiple reflections of the electromagnetic wave is:

[0030]

[0031] In the formula, Indicates the propagation time of electromagnetic waves Internal Path The second electric field energy in the reverberation chamber after the second reflection that was not scattered by the stirrer; Indicates the passage of electromagnetic waves The second electric field energy in the reverberation chamber after the second reflection that was not scattered by the stirrer; This represents the initial electric field energy; Represents the speed of light; This represents the typical distance, which is the average propagation distance between reflection points during the entire reflection process of the electromagnetic wave; This represents the total scattering cross section of the stirrer; This indicates the internal surface area of ​​the reverberation chamber; This represents the average reflection coefficient under all incident directions and polarization states; Indicates the passage of electromagnetic waves The propagation time of the second reflection; Indicates the process Number of mirrored objects after secondary reflection; Indicates the process The total surface area of ​​the mirror model after secondary reflection; Indicates the process The electric field strength after the second reflection when the field is not stirred; This represents the initial electric field strength.

[0032] Preferably, the damping time constant of the stirrer satisfies the expression:

[0033]

[0034] In the formula, This represents the damping time constant of the stirrer; Indicates the time constant of the reverberation chamber; Indicates the propagation time of electromagnetic waves Internal Path The second electric field energy in the reverberation chamber after the second reflection that was not scattered by the stirrer; This represents the initial electric field energy.

[0035] Preferably, the expression for the test model of the total scattering cross section of the reverberation chamber agitator is:

[0036]

[0037] In the formula, This represents the total scattering cross section of the stirrer; This represents the damping time constant of the stirrer; This indicates the internal surface area of ​​the reverberation chamber; Represents the speed of light; This represents the typical distance, which is the average propagation distance between reflection points during the entire reflection process of an electromagnetic wave.

[0038] The application of a test model for the total scattering cross section of a reverberation chamber stirrer based on the mirror principle adopts the following technical solution, including:

[0039] The total scattering cross section of the stirrer under test is calculated by substituting the reverberation chamber's internal surface area, typical distance, reverberation chamber's time constant, and the stirrer's damping time constant into the test model.

[0040] Preferably, the typical distance is determined by Monte Carlo simulation; the transmission coefficient between the transmitting and receiving antennas is measured at all stirring positions, and the time constant of the reverberation chamber and the damping time constant of the stirrer under test are obtained based on the transmission coefficient.

[0041] The beneficial effects of this invention are:

[0042] This invention, based on the mirror principle, constructs a mirror model of a reverberation chamber testing system. This model visually demonstrates the propagation path of electromagnetic waves within the reverberation chamber, simplifying the analysis of the electromagnetic wave propagation mechanism. Then, based on the mirror model and the initial electric field strength and energy, the time constant of the reverberation chamber and the damping time constant of the stirrer are obtained. Finally, based on the damping time constant of the stirrer and the surface area within the reverberation chamber, a test model for the total scattering cross section of the stirrer in the reverberation chamber is constructed. This mirror-based test model for the total scattering cross section of the stirrer in the reverberation chamber intuitively and clearly shows the path of electromagnetic waves scattered (or not scattered) by the stirrer, which helps in analyzing the relative positions of the excitation source and the stirrer in specific scenarios and provides guidance for optimizing configurations such as the selection of the excitation source position. When applied to measuring the total scattering cross section of the stirrer, this model can quickly and accurately measure the total scattering cross section of the stirrer, and is insensitive to the position of the excitation source, radiation pattern, and whether the cavity is loaded. It is stable and easy to implement.

[0043] Secondly, this invention applies the mirror principle to the field of reverberation chambers, enabling rapid and accurate evaluation of stirrer performance. Furthermore, this invention can be extended and applied to the measurement of the performance of other scattering bodies (such as scattering spheres and oscillating walls), enriching the evaluation theory of reverberation chamber stirring technology and helping to promote the design optimization of stirring technology and the overall reverberation chamber. Attached Figure Description

[0044] 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.

[0045] Figure 1This is a schematic flowchart of a test model for the total scattering cross section of a reverberation chamber stirrer based on the mirror principle according to the present invention.

[0046] Figure 2 This is a schematic plan view of a mirror model of the reverberation chamber used in an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of the reverberation chamber environment for measuring the total scattering cross section of the stirrer according to an embodiment of the present invention;

[0048] Figure 4 Monte Carlo simulation flowchart for typical distances of the reverberation chamber used in embodiments of the present invention;

[0049] Figure 5 A schematic diagram of Monte Carlo simulation results for a typical distance of the reverberation chamber used in the embodiments of the present invention;

[0050] Figure 6 The power delay spectra of the reverberation chamber used in the embodiments of the present invention at 2.7 GHz, 3.2 GHz, and 3.7 GHz are shown.

[0051] Figure 7 This is a schematic diagram showing the measurement results of the second electric field energy in the reverberation chamber at 3.2 GHz under three different stirrer scenarios used in the embodiments of the present invention.

[0052] Figure 8 This is a schematic diagram showing the measurement results of the damping time constant under three different stirrer scenarios used in the embodiments of the present invention;

[0053] Figure 9 This is a schematic diagram showing the measurement results of the total scattering cross section of the stirrer under test in three scenarios of stirrer under test, based on the mirror principle and the traditional method, in the embodiments of the present invention. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] This invention provides a test model for the total scattering cross section of a reverberation chamber stirrer based on the mirror principle, and an embodiment of its application, such as... Figure 1 As shown, it includes:

[0056] S1. Construct a mirror model and obtain the number of mirrored objects and the total surface area of ​​the mirror model after multiple reflections.

[0057] Specifically, based on the mirror principle, a mirror model of the reverberation chamber test system is established, and the number of mirror objects after multiple reflections and the total surface area of ​​the mirror model are obtained. It should be noted that the reverberation chamber test system includes a reverberation chamber cavity and a transmitting antenna.

[0058] S2. Obtain the time constant of the reverberation chamber;

[0059] Specifically, all losses within the reverberation chamber system are equivalent to the losses of the reverberation chamber walls, and the electric field intensity of the electromagnetic wave after multiple reflections is obtained based on the initial electric field intensity. The first electric field energy in the reverberation chamber after multiple reflections is obtained based on the electric field intensity after multiple reflections, the initial electric field energy, the number of mirror objects after multiple reflections, and the total surface area of ​​the mirror model. The time constant of the reverberation chamber is obtained based on the typical distance, the average reflection coefficient under all incident directions and polarization states, and the first electric field energy in the reverberation chamber after multiple reflections.

[0060] For example, in one embodiment, the electric field strength of an electromagnetic wave after multiple reflections is expressed as follows:

[0061] (1)

[0062] In the formula, Indicates the passage of electromagnetic waves Electric field strength after secondary reflection; Indicates the initial electric field strength; This represents the average reflection coefficient under all incident directions and polarization states.

[0063] For example, the expression for the energy of the first electric field in the reverberation chamber after multiple reflections of the electromagnetic wave is:

[0064] (2)

[0065] (3)

[0066] According to equations (1) and (2), we have:

[0067] (4)

[0068] In the formula, Indicates the propagation time of electromagnetic waves Internal Path The energy of the first electric field in the reverberation chamber after the second reflection; Indicates the passage of electromagnetic waves The energy of the first electric field in the reverberation chamber after the second reflection; This represents the initial electric field energy; Represents the speed of light; This represents the typical distance, which is the average propagation distance between reflection points during the entire reflection process of the electromagnetic wave; Represents the natural logarithm operation; Indicates the passage of electromagnetic waves The propagation time of the second reflection; This represents the average reflection coefficient under all incident directions and polarization states; Indicates the initial electric field strength; Indicates the process Number of mirrored objects after secondary reflection; Indicates the process The total surface area of ​​the mirror model after secondary reflection.

[0069] For example, the time constant of the reverberation chamber satisfies the expression:

[0070] (5)

[0071] That is, we get:

[0072] (6)

[0073] In the formula, Indicates the time constant of the reverberation chamber; Represents the speed of light; This represents the typical distance, which is the average propagation distance between reflection points during the entire reflection process of the electromagnetic wave; This represents the average reflection coefficient under all incident directions and polarization states.

[0074] S3. Obtain the damping time constant of the stirrer;

[0075] Specifically, based on the surface area inside the reverberation chamber and the total scattering cross-section of the stirrer, the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections is obtained; based on the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections, the electric field strength after multiple reflections, the initial electric field energy, the number of mirror objects after multiple reflections, and the total surface area of ​​the mirror model, the second electric field energy in the reverberation chamber that is not scattered by the stirrer after multiple reflections is obtained; based on the time constant of the reverberation chamber and the second electric field energy in the reverberation chamber that is not scattered by the stirrer after multiple reflections, the damping time constant of the stirrer is obtained.

[0076] For example, in one embodiment, the expression for the probability that an electromagnetic wave is not scattered by the stirrer after multiple reflections is:

[0077] (7)

[0078] In the formula, Indicates the passage of electromagnetic waves The probability that the secondary reflection is not scattered by the stirrer; This represents the probability that an electromagnetic wave is scattered by the stirrer after zero reflections. Indicates the electromagnetic wave passing through the first The probability of being scattered by the stirrer after the second reflection; This represents the total scattering cross section of the stirrer; This indicates the surface area inside the reverberation chamber.

[0079] For example, in one embodiment, the expression for the energy of the second electric field in the reverberation chamber that is not scattered by the stirrer after multiple reflections of the electromagnetic wave is:

[0080] (8)

[0081] (9)

[0082] In the formula, Indicates the propagation time of electromagnetic waves Internal Path The second electric field energy in the reverberation chamber after the second reflection that was not scattered by the stirrer; Indicates the passage of electromagnetic waves The second electric field energy in the reverberation chamber after the second reflection that was not scattered by the stirrer; This represents the initial electric field energy; Represents the speed of light; This represents the typical distance, which is the average propagation distance between reflection points during the entire reflection process of the electromagnetic wave; This represents the total scattering cross section of the stirrer; This indicates the internal surface area of ​​the reverberation chamber; This represents the average reflection coefficient under all incident directions and polarization states; Indicates the passage of electromagnetic waves The propagation time of the second reflection; Indicates the process Number of mirrored objects after secondary reflection; Indicates the process The total surface area of ​​the mirror model of the reverberation chamber after the second reflection; Indicates the process The electric field strength after the second reflection when the field is not stirred; This represents the initial electric field strength.

[0083] For example, in one embodiment, the damping time constant of the stirrer satisfies the expression:

[0084] (10)

[0085] In the formula, This represents the damping time constant of the stirrer; Indicates the time constant of the reverberation chamber; Indicates the propagation time of electromagnetic waves Internal Path The second electric field energy in the reverberation chamber after the second reflection that was not scattered by the stirrer; This represents the initial electric field energy.

[0086] S4. Construct a test model of the total scattering cross section of the reverberation chamber agitator;

[0087] Specifically, a test model for the total scattering cross section of the agitator in the reverberation chamber is constructed based on the damping time constant of the agitator and the surface area inside the reverberation chamber.

[0088] For example, the expression for the test model of the total scattering cross section of the reverberation chamber agitator is:

[0089] (11)

[0090] In the formula, This represents the total scattering cross section of the stirrer; This represents the damping time constant of the stirrer; This indicates the internal surface area of ​​the reverberation chamber; Represents the speed of light; The typical distance represents the average propagation distance between reflection points during the entire reflection process of an electromagnetic wave. The typical distance is determined through Monte Carlo simulation.

[0091] An application of a test model for the total scattering cross section of a reverberation chamber stirrer based on the mirror principle includes: substituting the internal surface area of ​​the reverberation chamber, typical distance, time constant of the reverberation chamber, and damping time constant of the stirrer under test into the test model to calculate the total scattering cross section of the stirrer under test; this method can quickly and accurately measure the total scattering cross section of the reverberation chamber stirrer, and is not sensitive to the position of the excitation source, the radiation pattern, or whether the cavity is loaded, and can directly reflect the stirrer's ability to scatter electromagnetic waves, which is helpful for the design optimization of the stirrer.

[0092] For example, in the process of obtaining the total scattering cross section of the reverberation chamber agitator using a test model, it is first necessary to obtain the typical distance, the time constant of the reverberation chamber, and the damping time constant of the agitator under test.

[0093] For example, the steps to obtain the typical distance are: determining the inner surface area of ​​the reverberation chamber based on the dimensions of the reverberation chamber being tested, and simultaneously determining the typical distance through Monte Carlo simulation, i.e. Figure 4 As shown, the steps for determining a typical distance using Monte Carlo simulation are as follows: 1. Set the simulation parameters, including the number of excitation sources. Number of propagation directions Number of reflections 2. Set the simulation boundary conditions according to the size of the reverberation chamber; 3. Randomly set the first boundary conditions within the reverberation chamber.i indivual( 4. The coordinate position of the excitation source; i The incentive source is randomly set. j indivual( 5. Initial propagation direction; Simulation in the 1st... i The incentive source is from the first j 6. Under the initial incident conditions, determine the propagation distance, reflection point, and direction of the reflected wave; 7. Set the reflection point determined in step 5 as the new excitation source position, and set the reflected wave direction determined in step 5 as the new propagation direction. Repeat step 5 until the number of reflections in the simulation reaches the number of reflections set in step 1; 8. Repeat steps 4-6 until the number of propagation directions in the simulation reaches the number of propagation directions set in step 1; 9. Repeat steps 3-7 until the number of excitation sources in the simulation reaches the number of excitation sources set in step 1; 10. Calculate the typical distance based on the simulation data.

[0094] For example, the steps for obtaining the time constant of the reverberation chamber and the damping time constant of the stirrer under test are as follows: Set the number of stirring positions for the source stirrer and the stirrer; measure the transmission coefficient between the transmitting antenna and the receiving antenna at all stirring positions; and calculate the time constant of the reverberation chamber and the damping time constant of the stirrer under test. Specifically, the transmitting antenna and the receiving antenna are connected to two ports of a vector network analyzer, and the transmission coefficient between the transmitting antenna and the receiving antenna is obtained through the vector network analyzer. The power delay spectrum of the reverberation chamber is plotted based on the transmission coefficient, and the time constant of the reverberation chamber is obtained by extracting the decay rate of the power delay spectrum. The process of obtaining the damping time constant is as follows: the transmitting and receiving antennas are connected to the two ports of a vector network analyzer, respectively. The transmission coefficient between the transmitting and receiving antennas is obtained through the vector network analyzer. Based on the transmission coefficient, the power delay spectrum (i.e., the first electric field energy spectrum) and the unstirred energy spectrum (i.e., the second electric field energy spectrum) of the reverberation chamber are plotted. The damping time constant is obtained by extracting the decay rate of the power delay spectrum and the unstirred energy spectrum.

[0095] The following is in conjunction with the appendix Figure 2-8 This embodiment will be described in detail below:

[0096] like Figure 2 As shown, the mirror model planar schematic diagram of the reverberation chamber used in this embodiment of the invention includes multiple rectangles (reverberation chambers), and the subscripts in the rectangles are... ( This indicates that the rectangle represents the point through which the electromagnetic wave passes. The image produced during secondary reflection. Furthermore, Figure 2 It clearly demonstrates examples of electromagnetic wave propagation paths scattered (stirred) by (or not stirred) stirrers in real-world scenarios, and their equivalent propagation paths in a mirror model.

[0097] A schematic diagram of the reverberation chamber used in the embodiments of the present invention is shown below. Figure 3 As shown, the reverberation chamber measures 1.50 m × 1.44 m × 0.92 m. It contains two stirrers under test: one horizontal and one vertical. The horizontal stirrer is 0.7 m long, and the vertical stirrer is 1.2 m high. The rotation radius of both stirrers is 0.41 m. The reverberation chamber also includes a mechanical turntable with a height-adjustable antenna support. Both the transmitting and receiving antennas are standard horn antennas. The transmitting antenna is mounted on a support on the bottom of the reverberation chamber, with its main radiation direction pointing towards the horizontal stirrer. The receiving antenna is mounted on a support on the turntable, offset 20 cm from the turntable center (turntable diameter 60 cm). The transmitting and receiving antennas are connected to two ports of a network analyzer. The test frequency band of this embodiment is 2.4 GHz - 4 GHz. The stirrers and turntable rotate independently, with 20 positions per revolution, resulting in 400 stirring positions in a single test. The position of the transmitting antenna remains constant throughout the test.

[0098] In this embodiment of the invention, the total scattering cross-section of the stirrer was measured under three different stirrer testing scenarios. A schematic diagram of the reverberation chamber test scenario is shown below. Figure 3 As shown, in reverberation chamber test scenario 1, the horizontal stirrer rotates independently while the vertical stirrer remains stationary; in reverberation chamber test scenario 2, the vertical stirrer rotates independently while the horizontal stirrer remains stationary; and in reverberation chamber test scenario 3, the horizontal and vertical stirrers rotate synchronously.

[0099] To verify the feasibility and effectiveness of using a test model to obtain the total scattering cross section, the verification steps adopted in this invention are as follows:

[0100] Step 1: Perform Monte Carlo simulation on the typical distances of the reverberation chamber to determine the values ​​of the typical distances;

[0101] Step 2: Based on scenarios 1, 2, and 3, set the operating state of the stirrer under test in the reverberation chamber and conduct tests to obtain 400 sets of results for each scenario. (Transmission coefficient) parameter;

[0102] Step 3: Based on the measurements obtained in Step 2 The parameters were used to calculate the damping time constant of the reverberation chamber agitator under three different scenarios.

[0103] Step 4: Using the typical distance obtained in Step 1 and the damping time constant obtained in Step 3, calculate the total scattering cross section based on the mirror principle. At the same time, using the damping time constant obtained in Step 3, calculate the total scattering cross section based on the traditional method. Compare and verify the total scattering cross sections obtained by the two methods.

[0104] The power delay profile (PDP) of the reverberation chamber can be calculated using equation (12). The unstirred power (PUS) of the second electric field in the reverberation chamber can be calculated using equation (13). Based on this, the damping time constant of the stirrer can be calculated using equation (14). The damping time constant of the stirrer is a characteristic quantity of the stirrer's structure. The smaller its value, the stronger the stirrer's ability to scatter electromagnetic waves.

[0105] (12)

[0106] (13)

[0107] according to and get:

[0108] (14)

[0109] In the formula, This indicates the number of records made by the network analyzer. f frequency points S 21 Parameters; IFFT stands for Inverse Fast Fourier Transform algorithm; Expressing the request N The statistical average of the samples; Indicates the number of stirrer samples; This represents the number of turntable samples, in this embodiment. ln represents the natural logarithm operation. slope The calculation is solved by curve fitting. and The slope of the linear portion.

[0110] The total scattering cross section of the reverberation chamber stirrer based on the mirror principle can be calculated by the following formula (14).

[0111] (14)

[0112] In the formula, S This represents the internal surface area of ​​the reverberation chamber. L Indicates typical distance, c Represents the speed of light. This represents the damping time constant of the stirrer in the reverberation chamber.

[0113] The total scattering cross section of the reverberation chamber stirrer based on the traditional method can be calculated by the following formula (15).

[0114] (15)

[0115] In the formula, V It is the internal volume of the reverberation chamber.

[0116] The Monte Carlo simulation process for the typical distance of the reverberation chamber used in this embodiment is as follows: Figure 4 As shown. Monte Carlo simulation results for typical distances under different propagation direction numbers and different reflection counts are as follows. Figure 5 As shown in the figure, it can be seen that the simulated typical distance gradually tends to a stable value, i.e., the true value of the typical distance, as the number of propagation directions and the number of reflections increase. When the number of propagation directions reaches... And the number of reflections reached Subsequently, the increase in the number of propagation directions and the number of reflections no longer has a significant impact on the simulated typical distance. It should be noted that the number of propagation directions and the number of reflections at simulation convergence may differ for reverberation chambers of different sizes. In general, simulation shows that the typical distance of the reverberation chamber used in this embodiment is 0.808 m. In practice, appropriate simulation parameters can be set to determine the typical distance of the reverberation chamber used, based on requirements such as computation time and accuracy.

[0117] The power delay spectra of the reverberation chamber used in this embodiment at 2.7 GHz, 3.2 GHz, and 3.7 GHz are as follows: Figure 6 As shown. Since the power delay spectrum of the reverberation chamber (at a specific frequency) depends only on the energy decay characteristics within the reverberation chamber and is independent of the stirrer rotation configuration, in order to accurately calculate and clearly display the power delay spectrum of the reverberation chamber, Figure 6 Only the measurement results for a scenario where two stirrers rotate synchronously are plotted. Figure 6 It can be seen that the PDP curves of the reverberation chamber at different frequencies all exhibit typical exponential decay characteristics. Meanwhile, as the frequency increases, the decay rate of the power delay spectrum decreases slightly, but because the spacing between the three frequency points is not large, the difference in decay rate is not significant.

[0118] The measurement results of the unstirred energy in the reverberation chamber at 3.2 GHz under the three stirrer test scenarios used in the embodiments of the present invention are as follows: Figure 7 As shown. By Figure 7It can be seen that the decay rate of unstirred energy in scenario 3 is significantly greater than that in scenarios 1 and 2, with scenario 1 exhibiting the slowest decay rate. This is because the rotational regions (i.e., equivalent boundaries) of the stirrers differ in the three scenarios: in scenario 1, only the horizontal stirrer (0.7 m in length, 0.41 m in rotation radius) rotates; in scenario 2, only the vertical stirrer (1.2 m in length, 0.41 m in rotation radius) rotates; and in scenario 3, both stirrers rotate synchronously. Therefore, the larger the rotational region, the faster the decay rate of unstirred energy. In general, the performance of the stirrer is related to the size of its rotational region, and the decay rate of unstirred energy increases with the increase of the stirrer's rotational region.

[0119] The measurement results of the damping time constant of the reverberation chamber under three agitator scenarios are as follows: Figure 8 As shown. In this embodiment, the inverse Fourier transform bandwidth is 600MHz, therefore the time constant is plotted in the range of 2.7GHz - 3.7GHz. (From...) Figure 8 It can be seen that for a specific stirrer, the corresponding damping time constant does not change significantly with frequency. Furthermore, the damping time constant directly reflects the stirrer's ability to stir electromagnetic waves, and it increases with the increase of the stirrer's rotational region. Since the damping time constant is extracted from the decay curve of unstirred energy in the reverberation chamber, therefore... Figure 7 and Figure 8 The conclusions regarding the unstirred energy decay characteristics at 3.2 GHz are consistent. However, Figure 7 It can only reflect the attenuation characteristics of unstirred energy at a specific frequency, while Figure 8 It can clearly show the decay rate of unstirred energy across the entire frequency band.

[0120] The embodiments of the present invention measure the total scattering cross section of the stirrer under test in three stirrer scenarios based on the mirror principle and traditional methods, as follows: Figure 9 As shown. By Figure 9 It can be seen that the calculation results of the total scattering cross section of the stirrer based on the mirror principle and the traditional method are basically consistent, and are independent of the test frequency and test scenario. This result fully demonstrates the effectiveness, feasibility and stability of the test method for the total scattering cross section of the reverberation chamber stirrer based on the mirror principle proposed in this invention.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for constructing a test model of the total scattering cross section of a reverberation chamber stirrer based on the mirror principle, characterized in that, The method comprises the following steps: According to the mirror principle, a mirror model of the reverberation chamber test system is established, and the number of mirror objects after multiple reflections and the total surface area of the mirror model are obtained; All the losses in the reverberation chamber system are equivalent to the losses of the cavity wall of the reverberation chamber, and the electric field intensity after multiple reflections of electromagnetic waves is obtained based on the initial electric field intensity; The first electric field energy in the reverberation chamber after multiple reflections of electromagnetic waves is obtained based on the electric field intensity after multiple reflections of electromagnetic waves, the initial electric field energy, the number of mirror objects after multiple reflections, and the total surface area of the mirror model; The time constant of the reverberation chamber is obtained according to the average reflection coefficient under the typical distance, all incident directions and polarization states, and the first electric field energy in the reverberation chamber after multiple reflections of electromagnetic waves; The probability that electromagnetic waves are not scattered by the stirrer after multiple reflections is obtained according to the total scattering cross section of the stirrer and the internal surface area of the cavity of the reverberation chamber; The second electric field energy in the reverberation chamber that is not scattered by the stirrer after multiple reflections of electromagnetic waves is obtained according to the probability that electromagnetic waves are not scattered by the stirrer after multiple reflections, the electric field intensity after multiple reflections of electromagnetic waves, the initial electric field energy, the number of mirror objects after multiple reflections, and the total surface area of the mirror model; The damping time constant of the stirrer is obtained according to the time constant of the reverberation chamber and the second electric field energy in the reverberation chamber that is not scattered by the stirrer after multiple reflections of electromagnetic waves; A test model of the total scattering cross section of the stirrer in the reverberation chamber is constructed according to the damping time constant of the stirrer, the typical distance, and the internal surface area of the cavity of the reverberation chamber, wherein the typical distance is the average propagation distance between reflection points of electromagnetic waves in the entire reflection process.

2. The method according to claim 1, wherein the method is characterized by: The expression of the electric field intensity after multiple reflections of electromagnetic waves is: wherein represents the electric field intensity after the electromagnetic wave has passed through the second reflection; represents the initial electric field intensity; represents the average reflection coefficient for all incident directions and polarization states.

3. The method according to claim 2, wherein the method is characterized by, The expression of the first electric field energy in the reverberation chamber after multiple reflections of electromagnetic waves is: In the formula, Indicates the propagation time of electromagnetic waves Internal Path The energy of the first electric field in the reverberation chamber after the second reflection; Indicates the passage of electromagnetic waves The energy of the first electric field in the reverberation chamber after the second reflection; This represents the initial electric field energy; Represents the speed of light; This represents the typical distance, which is the average propagation distance between reflection points during the entire reflection process of the electromagnetic wave; Represents the natural logarithm operation; Indicates the passage of electromagnetic waves The propagation time of the second reflection; This represents the average reflection coefficient under all incident directions and polarization states; Indicates the process Number of mirrored objects after secondary reflection; Indicates the process The total surface area of ​​the mirror model after secondary reflection.

4. The method according to claim 3, wherein the method is characterized by, The time constant of the reverberation chamber satisfies the expression: wherein denotes the time constant of the reverberation chamber; denotes the speed of light; denotes the typical distance, i.e. the average propagation distance between reflection points during the entire reflection process; denotes the average reflection coefficient over all incidence directions and polarization states.

5. The method according to claim 1, wherein the method is characterized by: The expression of the probability that electromagnetic waves are not scattered by the stirrer after multiple reflections is: wherein P0represents the probability that the electromagnetic wave is not scattered by the stirrer after 0 reflections; Pnrepresents the probability that the electromagnetic wave is not scattered by the stirrer after n reflections; P0represents the probability that the electromagnetic wave is not scattered by the stirrer after 0 reflections; Pnrepresents the probability that the electromagnetic wave is not scattered by the stirrer after n reflections; Pnrepresents the probability that the electromagnetic wave is not scattered by the stirrer after n reflections; Ptotai represents the total scattering cross section of the stirrer; S represents the internal surface area of the reverberation chamber.

6. The method according to claim 5, wherein the method is characterized by: The expression of the second electric field energy in the reverberation chamber that is not scattered by the stirrer after multiple reflections of electromagnetic waves is: where represents the propagation time of the electromagnetic wave through the reverberation chamber after the second reflection; represents the second electric field energy in the reverberation chamber not scattered by the stirrers after the second reflection; represents the initial electric field energy; represents the speed of light; represents the typical distance, i.e. the average propagation distance between reflection points of the electromagnetic wave during the whole reflection process; represents the total scattering cross section of the stirrers; represents the internal surface area of the reverberation chamber; represents the average reflection coefficient for all incident directions and polarization states; represents the propagation time of the electromagnetic wave through the reverberation chamber after the second reflection; represents the number of mirror images after the second reflection; represents the total surface area of the mirror image model after the second reflection; represents the electric field intensity in the reverberation chamber not stirred after the second reflection; represents the initial electric field intensity.

7. The method according to claim 1, wherein the method is characterized by: The damping time constant of the stirrer satisfies the expression: wherein represents the damping time constant of the stirrer; represents the time constant of the reverberation chamber; represents the propagation time of the electromagnetic wave through represents the second electric field energy in the reverberation chamber after reflections not scattered by the stirrer; represents the initial electric field energy.

8. The method according to claim 1, wherein the method is characterized by: The expression of the test model of the total scattering cross section of the stirrer in the reverberation chamber is: wherein denotes the total scattering cross section of the stirrer; denotes the damping time constant of the stirrer; denotes the internal surface area of the reverberation chamber; denotes the speed of light; denotes the typical distance, i.e. the average propagation distance between reflection points of the electromagnetic waves during the entire reflection process.

9. Use of a test model of the total scattering cross section of a reverberation chamber stirrer based on the mirror principle, characterized in that, The method comprises the following steps: The internal surface area of the cavity of the reverberation chamber, the typical distance, the time constant of the reverberation chamber, and the damping time constant of the stirrer to be measured are substituted into the test model constructed by the method of any one of claims 1-8, and the total scattering cross section of the stirrer to be measured is calculated.

10. The use of a test model of the total scattering cross section of a reverberation chamber stirrer based on the mirror principle according to claim 9, characterized in that, The typical distance is determined by Monte Carlo simulation; the transmission coefficient between the transmitting antenna and the receiving antenna is measured at all stirring positions, and the time constant of the reverberation chamber and the damping time constant of the stirrer to be measured are obtained according to the transmission coefficient.

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