Method for testing total scattering cross section of stirrer of reverberation chamber based on mirror image principle and application

Abstract

The invention relates to the technical field of microwave measurement and reverberation chambers, in particular to a reverberation chamber stirrer total scattering cross section test model based on the mirror image principle and application, and the method comprises the steps: constructing a mirror image model, and obtaining the number of mirror image objects after multiple reflections and the total surface area of the mirror image model; acquiring a time constant of the reverberation chamber; obtaining a damping time constant of the stirrer; and constructing a test model of the total scattering cross section of the reverberation chamber stirrer. According to the invention, the propagation mechanism of the electromagnetic wave in the reverberation chamber and the scattering characteristic of the stirrer to the electromagnetic wave are visually reflected, a certain guiding effect is provided for optimization of the stirrer and test configuration, meanwhile, unstirred energy in the reverberation chamber can be understood, analyzed and reduced, and finally, the performance of the reverberation chamber is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical fields of microwave measurement and reverberation chamber, and particularly relates to a test model and application of the total scattering cross-section of a reverberation chamber stirrer based on the mirror principle. Background Art

[0002] A microwave reverberation chamber is a high-quality factor metal resonant cavity, usually equipped with one or more metal stirrers with irregular shapes inside. By rotating the stirrer and other methods, the electromagnetic fields in its working area exhibit physical characteristics such as statistical uniformity, isotropy, and random polarization. The reverberation chamber has advantages such as low construction cost and large test space, and can also excite a high environmental field strength with a small input power. Therefore, it is widely used in the field of electromagnetic compatibility testing, especially for the high-intensity radiation field testing of electrical and electronic systems and equipment. In recent years, with its flexible and efficient testing methods and good wireless channel reproduction ability, the reverberation chamber technology has rapidly expanded into the air interface testing field. The Wireless Communication and Internet Association recognized the reverberation chamber as a standardized air interface testing technology for large-sized devices in 2016, and then recognized it as a standardized air interface testing technology for single-input single-output systems in 2022. The formulation of reverberation chamber-related standards reflects the consensus on the application of the reverberation chamber in the fields of electromagnetic compatibility and air interface testing.

[0003] The uniform characteristics of the electromagnetic fields in the reverberation chamber are presented in a statistical sense. The more independent samples there are, the more ideal the statistical characteristics are, and the better the field uniformity is. Currently, reverberation chamber tests mainly obtain independent samples through three stirring methods: mechanical stirring, source stirring, and frequency stirring. Mechanical stirring changes the boundary conditions of the electromagnetic fields by rotating the stirrer; frequency stirring multiplexes electromagnetic modes within a certain frequency band through post-processing of experimental data; source stirring achieves the purpose of exciting multiple electromagnetic modes by changing the position, direction, polarization, etc. of the excitation source. The effectiveness of the stirring method directly determines the reliability and accuracy of reverberation chamber tests. Therefore, how to effectively evaluate the performance of the stirring technology is an important research direction in the reverberation chamber field. Given that mechanical stirring is the most commonly used stirring method in reverberation chamber tests and the stirrer is a representative of the scatterers in the reverberation chamber, an effective stirrer performance evaluation method is crucial for the development and optimization of reverberation chamber tests.

[0004] At present, there are mainly three evaluation indexes for the performance of reverberation chamber stirrers: the independent sampling number, the field uniformity, and the total scattering cross-section. Both the independent sampling number and the field uniformity use statistical theory to analyze the measured values of electric fields or scattering parameters, without considering the working characteristics of the stirrer (which is different from methods such as source stirring and frequency stirring). Although the independent sampling number and the field uniformity can be used as general indexes for evaluating stirring techniques, they cannot reflect the true working characteristics of the stirrer, nor can they guide the optimization design of the stirrer. The scattering cross-section of an object is defined as the ratio of the scattered energy of the object to the incident power density. In view of the statistical uniformity characteristics of the electromagnetic field in the reverberation chamber, the concept of the total scattering cross-section is usually adopted in the field of reverberation chambers. The total scattering cross-section of the stirrer can directly reflect the scattering ability of the stirrer for electromagnetic waves in different directions and polarization states, and it is a characteristic quantity of the stirrer's own structure, and is not sensitive to the position of the excitation, the radiation pattern, and whether the cavity is loaded. It can be seen that the total scattering cross-section of the stirrer is an effective parameter for measuring the performance of the stirrer.

[0005] However, in the prior art, the total scattering cross-section of the stirrer is mainly determined by calculating the damping time constant. This method simultaneously considers the attenuation characteristics of the un-stirred energy and the total average energy in the reverberation chamber, extracts the damping time constant according to the attenuation rate of the ratio of the un-stirred energy to the total average energy, and then determines the total scattering cross-section of the stirrer. This method cannot intuitively reflect the propagation mechanism of electromagnetic waves in the reverberation chamber and the interaction mechanism between the stirrer and the electromagnetic waves. Therefore, it is difficult to support the key requirements of improving the performance of the stirrer, optimizing the test configuration, and reducing the un-stirred energy in the field of reverberation chambers.

[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] The present 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 measuring 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 is realized to solve the 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 solutions, including: According to the mirror principle, establish a mirror model of the reverberation chamber test system, and obtain the number of mirror objects after multiple reflections and the total surface area of the mirror model; Equivalent all the losses in the reverberation chamber system to the losses of the reverberation chamber cavity wall, and obtain the electric field strength of the electromagnetic wave after multiple reflections based on the initial electric field strength; Obtain the first electric field energy in the reverberation chamber after multiple reflections of electromagnetic waves based on the electric field strength 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; Obtain the time constant of the reverberation chamber according to 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 of electromagnetic waves; Obtain the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections according to the inner surface area of the reverberation chamber and the total scattering cross-section of the stirrer; Obtain the second electric field energy in the reverberation chamber that is not scattered by the stirrer after multiple reflections of electromagnetic waves according to the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections, the electric field strength 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; Obtain the damping time constant of the stirrer 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; Construct a test model for the total scattering cross-section of the reverberation chamber stirrer according to the damping time constant of the stirrer, the typical distance, and the inner surface area of the reverberation chamber, where the typical distance is the average propagation distance between reflection points during the entire reflection process of the electromagnetic wave.

[0009] Preferably, the expression for the electric field strength after multiple reflections of electromagnetic waves is:

[0010] In the formula, represents the electric field strength after times of reflections of the electromagnetic wave; represents the initial electric field strength; represents the average reflection coefficient under all incident directions and polarization states.

[0011] Preferably, the expression for the first electric field energy in the reverberation chamber after multiple reflections of electromagnetic waves is:

[0012] In the formula, represents the first electric field energy in the reverberation chamber after times of reflections of the electromagnetic wave within the propagation time ; represents the first electric field energy in the reverberation chamber after times of reflections of the electromagnetic wave; represents the initial electric field energy; represents the speed of light; represents the typical distance, that is, the average propagation distance between reflection points during the entire reflection process of the electromagnetic wave; represents the natural logarithm operation; represents the propagation time of an electromagnetic wave after reflections; represents the average reflection coefficient over all incident directions and polarization states; represents the initial electric field strength; represents after reflections, the number of mirror objects; represents after reflections, the total surface area of the mirror model.

[0013] Preferably, the time constant of the reverberation chamber satisfies the expression:

[0014] wherein, represents the time constant of the reverberation chamber; represents the speed of light; represents a typical distance, i.e., the average propagation distance between reflection points of the electromagnetic wave during the entire reflection process; represents the average reflection coefficient over all incident directions and polarization states.

[0015] Preferably, the expression for the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections is:

[0016] wherein, represents the probability that the electromagnetic wave is not scattered by the stirrer after reflections; represents the probability that the electromagnetic wave is scattered by the stirrer after 0 reflections; represents the probability that the electromagnetic wave is scattered by the stirrer after the th reflection; represents the total scattering cross-section of the stirrer; represents the inner surface area of the reverberation chamber.

[0017] Preferably, the expression for the second electric field energy in the reverberation chamber that is not scattered by the stirrer after multiple reflections of the electromagnetic wave is:

[0018] wherein, represents the second electric field energy in the reverberation chamber that is not scattered by the stirrer after reflections of the electromagnetic wave during the propagation time ; represents the second electric field energy in the reverberation chamber that is not scattered by the stirrer after reflections; 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 electromagnetic waves during the entire reflection process; represents the total scattering cross-section of the stirrer; represents the inner surface area of the reverberation chamber; represents the average reflection coefficient under all incident directions and polarization states; represents that the electromagnetic wave passes through the propagation time of represents that after passing through the number of mirror objects after represents that after passing through the total surface area of the mirror model after represents that after passing through the electric field strength that is not stirred after represents the initial electric field strength.

[0019] Preferably, the damping time constant of the stirrer satisfies the expression:

[0020] wherein, represents the damping time constant of the stirrer; represents the time constant of the reverberation chamber; represents the second electric field energy that is not scattered by the stirrer in the reverberation chamber after the electromagnetic wave passes through within the propagation time after represents the initial electric field energy.

[0021] Preferably, the expression of the test model for the total scattering cross-section of the reverberation chamber stirrer is:

[0022] wherein, represents the total scattering cross-section of the stirrer; represents the damping time constant of the stirrer; represents the inner surface area of the reverberation chamber; represents the speed of light; represents the typical distance, i.e., the average propagation distance between reflection points of electromagnetic waves during the entire reflection process.

[0023] An 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: Substitute the inner surface area 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 into the test model, and calculate the total scattering cross-section of the stirrer to be measured.

[0024] Preferably, 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 based on the transmission coefficient.

[0025] The beneficial effects of the present invention are as follows: Based on the mirror principle, the present invention constructs a mirror model of the reverberation chamber test system, which intuitively shows the propagation path of electromagnetic waves in the reverberation chamber through the mirror model of the reverberation chamber test system, and simplifies the analysis of the electromagnetic wave propagation mechanism; then, based on the mirror model of the reverberation chamber test system, the initial electric field strength and the initial electric field 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 inner surface area of the reverberation chamber, a test model for the total scattering cross-section of the reverberation chamber stirrer is constructed; the test model for the total scattering cross-section of the reverberation chamber stirrer based on the mirror principle intuitively and clearly shows the path of electromagnetic waves being (or not being) scattered by the stirrer, which is helpful for analyzing the relative position between the excitation source and the stirrer in a specific scenario, and has a certain guiding role for the configuration optimization such as the selection of the excitation source position; the test model for the total scattering cross-section of the reverberation chamber stirrer based on the mirror principle is applied to measure the total scattering cross-section of the stirrer, and can quickly and accurately measure the total scattering cross-section of the stirrer, and is not sensitive to the position, radiation pattern, and whether the cavity is loaded of the excitation source, with stable performance and easy to implement.

[0026] Secondly, the present invention applies the mirror principle to the field of reverberation chambers, realizing fast and accurate evaluation of the performance of stirrers, and the present invention can be extended and applied to the measurement of the performance of other scatterers (such as scatter balls, swinging walls), enriching the evaluation theory of reverberation chamber stirring technology, and contributing to promoting the design optimization of stirring technology and the overall reverberation chamber. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings without creative efforts based on these drawings.

[0028] Figure 1 It is a schematic flow chart of a test model for the total scattering cross-section of a reverberation chamber stirrer based on the mirror principle of the present invention; Figure 2 It is a schematic plan view of the mirror model of the reverberation chamber used in the embodiment of the present invention; Figure 3 It is a schematic view of the reverberation chamber environment for measuring the total scattering cross-section of the stirrer in the embodiment of the present invention; Figure 4Monte Carlo simulation flowchart of the typical distance of the reverberation chamber used in the embodiments of the present invention; Figure 5 Schematic diagram of the Monte Carlo simulation results of the typical distance of the reverberation chamber used in the embodiments of the present invention; Figure 6 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; Figure 7 Schematic diagram of the measurement results of the second electric field energy in the reverberation chamber without stirring at 3.2 GHz under three scenarios of the stirrers to be measured adopted in the embodiments of the present invention; Figure 8 Schematic diagram of the measurement results of the damping time constant under three scenarios of the stirrers to be measured adopted in the embodiments of the present invention; Figure 9 Schematic diagram of the measurement results of the total scattering cross-section of the stirrers to be measured based on the mirror principle and traditional methods under three scenarios of the stirrers to be measured adopted in the embodiments of the present invention. Specific embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] An embodiment of a test model and application of the total scattering cross-section of a reverberation chamber stirrer based on the mirror principle of the present invention is as Figure 1 shown and includes: S1. Construct a mirror model and obtain the number of mirror objects after multiple reflections and the total surface area of the mirror model; Specifically, according to the mirror principle, establish a mirror model of the reverberation chamber test system, and obtain the number of mirror objects after multiple reflections and the total surface area of the mirror model; it should be noted that the reverberation chamber test system includes a reverberation chamber cavity and a transmitting antenna.

[0031] S2. Obtain the time constant of the reverberation chamber; Specifically, all the losses in the reverberation chamber system are equivalent to the losses of the chamber walls, and the electric field strength after multiple reflections of the electromagnetic wave is obtained based on the initial electric field strength; the first electric field energy in the reverberation chamber after multiple reflections of the electromagnetic wave is obtained based on the electric field strength after multiple reflections of the electromagnetic wave, 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 typical distance, the average reflection coefficient in all incident directions and polarization states, and the first electric field energy in the reverberation chamber after multiple reflections of the electromagnetic wave.

[0032] Exemplarily, in one embodiment, the expression of the electric field strength after multiple reflections of the electromagnetic wave is: (1) In the formula, represents the electric field strength after times of reflections of the electromagnetic wave; represents the initial electric field strength; represents the average reflection coefficient in all incident directions and polarization states.

[0033] Exemplarily, the expression of the first electric field energy in the reverberation chamber after multiple reflections of the electromagnetic wave is: (2) (3) According to formula (1) and formula (2), there is: (4) In the formula, represents the first electric field energy in the reverberation chamber after times of reflections of the electromagnetic wave during the propagation time ; represents the first electric field energy in the reverberation chamber after times of reflections of the electromagnetic wave; represents the initial electric field energy; represents the speed of light; represents the typical distance, that is, the average propagation distance between the reflection points during the whole reflection process of the electromagnetic wave; represents the natural logarithm operation; represents the propagation time of the electromagnetic wave after times of reflections; represents the average reflection coefficient in all incident directions and polarization states; represents the initial electric field strength; represents the number of mirror objects after times of reflections; represents the total surface area of the mirror model after times of reflections.

[0034] Exemplarily, the time constant of the reverberation chamber satisfies the expression: (5) That is, it is obtained: (6) In the formula, represents the time constant of the reverberation chamber; represents the speed of light; represents the typical distance, that is, the average propagation distance between the reflection points during the entire reflection process of the electromagnetic wave; represents the average reflection coefficient under all incident directions and polarization states.

[0035] S3. Obtain the damping time constant of the stirrer; Specifically, according to the inner surface area of the reverberation chamber and the total scattering cross-section of the stirrer, obtain the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections; according to the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections, the electric field strength of the electromagnetic wave 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, obtain the second electric field energy in the reverberation chamber that is not scattered by the stirrer after multiple reflections of the electromagnetic wave; 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 the electromagnetic wave, obtain the damping time constant of the stirrer.

[0036] Exemplarily, in one embodiment, the expression for the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections is: (7) In the formula, represents the probability that the electromagnetic wave is not scattered by the stirrer after times of reflections; represents the probability that the electromagnetic wave is scattered by the stirrer after 0 times of reflections; represents the probability that the electromagnetic wave is scattered by the stirrer after the th reflection; represents the total scattering cross-section of the stirrer; represents the inner surface area of the reverberation chamber.

[0037] Exemplarily, in one embodiment, the expression for the second electric field energy in the reverberation chamber that is not scattered by the stirrer after multiple reflections of the electromagnetic wave is: (8) (9) In the formula, represents the electromagnetic wave during the propagation time within The second electric field energy in the reverberation chamber that is not scattered by the stirrer after the secondary reflection; Indicates that the electromagnetic wave passes through The second electric field energy in the reverberation chamber that is not scattered by the stirrer after the secondary reflection; Indicates the initial electric field energy; Indicates the speed of light; Indicates a typical distance, i.e., the average propagation distance between the reflection points during the entire reflection process of the electromagnetic wave; Indicates the total scattering cross-section of the stirrer; Indicates the inner surface area of the reverberation chamber; Indicates the average reflection coefficient in all incident directions and polarization states; Indicates that the electromagnetic wave passes through The propagation time of the secondary reflection; Indicates after passing through The number of mirror objects after the secondary reflection; Indicates after passing through The total surface area of the reverberation chamber mirror model after the secondary reflection; Indicates after passing through The electric field strength that is not stirred after the secondary reflection; Indicates the initial electric field strength.

[0038] Exemplarily, in one embodiment, the damping time constant of the stirrer satisfies the expression: (10) In the formula, Indicates the damping time constant of the stirrer; Indicates the time constant of the reverberation chamber; Indicates that the electromagnetic wave passes through during the propagation time within The second electric field energy in the reverberation chamber that is not scattered by the stirrer after the secondary reflection; Indicates the initial electric field energy.

[0039] S4. Construct a test model for the total scattering cross-section of the reverberation chamber stirrer; Specifically, construct a test model for the total scattering cross-section of the reverberation chamber stirrer according to the damping time constant of the stirrer and the inner surface area of the reverberation chamber.

[0040] Exemplarily, the expression of the test model for the total scattering cross-section of the reverberation chamber stirrer is: (11) In the formula, Indicates the total scattering cross-section of the stirrer; Indicates the damping time constant of the stirrer; Indicates the inner surface area of the reverberation chamber; Indicates the speed of light; Represents the typical distance, which is the average propagation distance between reflection points during the entire reflection process of electromagnetic waves, and the typical distance is determined by Monte Carlo simulation.

[0041] An application of a test model for the total scattering cross-section of a reverberation chamber stirrer based on the mirror principle, including: substituting the inner surface area 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 into the test model to calculate the total scattering cross-section of the stirrer to be measured; this method can quickly and accurately measure the total scattering cross-section of the reverberation chamber stirrer, and is not sensitive to the position, direction pattern of the excitation source, and whether the cavity is loaded, and can directly reflect the scattering ability of the stirrer to electromagnetic waves, which is helpful for the design optimization of the stirrer.

[0042] Exemplarily, in the process of obtaining the total scattering cross-section of the reverberation chamber stirrer using the 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 stirrer to be measured.

[0043] Exemplarily, the steps to obtain the typical distance are: determine the inner surface area of the reverberation chamber according to the size of the reverberation chamber for the test, and at the same time determine the typical distance through Monte Carlo simulation, that is, as Figure 4 shown, the steps to determine the typical distance through Monte Carlo simulation are: 1. Set the simulation parameters, and the simulation parameters include the number of excitation sources , the number of propagation directions , the number of reflections ; 2. Set the boundary conditions of the simulation according to the size of the reverberation chamber; 3. Randomly set the coordinate position of the i th ( ) excitation source in the reverberation chamber; 4. For the i th excitation source, randomly set the j th ( ) initial propagation direction; 5. Simulate the reflection under the condition that the i th excitation source is incident from the j th initial direction, and determine the propagation distance, reflection point, and reflection wave direction of the reflected wave; 6. Set the reflection point determined in step 5 as the new excitation source position, and at the same time set the reflection wave direction determined in step 5 as the new propagation direction, and repeat step 5 until the number of reflections in the simulation reaches the number of reflections set in step 1; 7. Repeat steps 4-6 until the number of propagation directions in the simulation reaches the number of propagation directions set in step 1; 8. Repeat steps 3-7 until the number of excitation sources in the simulation reaches the number of excitation sources set in step 1; 9. Calculate the typical distance according to the simulation data.

[0044] Exemplarily, the steps of obtaining the time constant of the reverberation chamber and the damping time constant of the stirrer to be measured are as follows: Set the number of stirring positions of 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 to be measured. Among them, connect the transmitting antenna and the receiving antenna to the two ports of the vector network analyzer respectively, and obtain the transmission coefficient between the transmitting antenna and the receiving antenna through the vector network analyzer ( ), draw the power delay spectrum of the reverberation chamber according to the transmission coefficient, and obtain the time constant of the reverberation chamber by extracting the attenuation rate of the power delay spectrum. The process of obtaining the damping time constant is as follows: Connect the transmitting antenna and the receiving antenna to the two ports of the vector network analyzer respectively, obtain the transmission coefficient between the transmitting antenna and the receiving antenna through the vector network analyzer, draw the power delay spectrum of the reverberation chamber (i.e., the first electric field energy spectrum) and the non-stirred energy spectrum (i.e., the second electric field energy spectrum) according to the transmission coefficient, and obtain the damping time constant by extracting the attenuation rates of the power delay spectrum and the non-stirred energy spectrum.

[0045] The following specifically describes this embodiment in conjunction with the attached Figures 2 - 8 drawings: As Figure 2 shown, the schematic plan view of the mirror model of the reverberation chamber used in the embodiment of the present invention includes multiple rectangles (reverberation chambers). The subscript in the rectangle () indicates that this rectangle is the mirror image generated when the electromagnetic wave undergoes the th reflection. In addition, Figure 2 clearly shows an example of the propagation path of the electromagnetic wave scattered (stirred) by the stirrer (or not) in practice and its equivalent propagation path in the mirror model.

[0046] The schematic diagram of the reverberation chamber used in the embodiment of the present invention is as Figure 3As shown, the reverberation chamber has dimensions of 1.50 m × 1.44 m × 0.92 m. The reverberation chamber is equipped with two stirrers to be tested, one horizontal stirrer and one vertical stirrer. The horizontal stirrer has a length of 0.7 m, and the vertical stirrer has a height of 1.2 m. The rotation radii of both stirrers to be tested are 0.41 m. In addition, the reverberation chamber is also equipped with a mechanical turntable, on which an antenna support with adjustable height is installed. Both the transmitting antenna and the receiving antenna are standard horn antennas. The transmitting antenna is installed on the support at the bottom surface of the reverberation chamber, and its main radiation direction points to the horizontal stirrer. The receiving antenna is installed on the support of the turntable and is offset 20 cm from the center of the turntable (the turntable diameter is 60 cm). The transmitting antenna and the receiving antenna are respectively connected to two ports of a network analyzer. The test frequency band of the embodiment of the present invention is 2.4 GHz - 4 GHz. The stirrers and the turntable rotate independently, and each has 20 positions in one rotation. Therefore, there are 400 stirring positions in one test. During the entire test process, the position of the transmitting antenna remains unchanged.

[0047] In the embodiments of the present invention, the total scattering cross-sections of the stirrers are measured respectively under three scenarios of stirrers to be tested. The schematic diagram of the reverberation chamber test scenario is as Figure 3 shown. In test scenario 1 of the reverberation chamber, the horizontal stirrer rotates independently and the vertical stirrer remains stationary; in test scenario 2 of the reverberation chamber, the vertical stirrer rotates independently and the horizontal stirrer remains stationary; in test scenario 3 of the reverberation chamber, the horizontal and vertical stirrers rotate synchronously.

[0048] To verify the feasibility and effectiveness of obtaining the total scattering cross-section using the test model, the verification steps adopted in the present invention are as follows: Step 1: Conduct Monte Carlo simulation on the typical distances of the used reverberation chamber to determine the values of the typical distances; Step 2: According to Scenario 1, Scenario 2, and Scenario 3, set the working states of the stirrers to be tested in the reverberation chamber and conduct tests to obtain 400 groups of (transmission coefficient) parameters in each scenario; Step 3: According to the parameters measured in Step 2, calculate the damping time constants of the stirrers in the reverberation chamber under the three scenarios respectively; Step 4: Use the typical distances obtained in Step 1 and the damping time constants obtained in Step 3 to calculate the total scattering cross-section based on the mirror principle. At the same time, use the damping time constants obtained in Step 3 to calculate the total scattering cross-section based on the traditional method, and compare and verify the total scattering cross-sections obtained by the two methods.

[0049] The power delay profile (PDP) of the reverberation chamber can be calculated by Equation (12) below. The unstirred power (PUS) in the reverberation chamber can be calculated by Equation (13) below. On this basis, the damping time constant of the stirrer can be calculated by Equation (14). The damping time constant of the stirrer is a characteristic quantity of the stirrer's own structure. The smaller its value, the stronger the scattering ability of the stirrer to electromagnetic waves.

[0050] (12) (13) According to and we get: (14) In the formula, represents the f th frequency point recorded by the network analyzer S 21 parameter; IFFT represents the inverse fast Fourier transform algorithm; represents the statistical average of N samples; represents the number of stirrer samples; represents the number of turntable samples. In this embodiment . ln represents the natural logarithm operation, slope The operation is solved by curve fitting and the slope of the linear part.

[0051] The total scattering cross-section of the reverberation chamber stirrer based on the mirror principle can be calculated by Equation (14) (14) In the formula, S represents the inner surface area of the reverberation chamber, L represents the typical distance, c represents the speed of light, represents the damping time constant of the stirrer in the reverberation chamber.

[0052] The total scattering cross-section of the reverberation chamber stirrer based on the traditional method can be calculated by Equation (15) (15) In the formula, V is the inner volume of the reverberation chamber.

[0053] The Monte Carlo simulation process of the typical distance of the reverberation chamber used in this embodiment is as Figure 4As shown. Under the conditions of different numbers of propagation directions and different numbers of reflections, the Monte Carlo simulation results of the typical distance are as Figure 5 shown. It can be seen that the simulated values of the typical distance gradually tend to a stable value with the increase of the number of propagation directions and the number of reflections, that is, the true value of the typical distance. When the number of propagation directions reaches and the number of reflections reaches after that, the increase of the number of propagation directions and the number of reflections no longer significantly affects the simulated value of the typical distance. It should be noted that for reverberation chambers of different sizes, the number of propagation directions and the number of reflections at the time of simulation convergence may vary. Generally speaking, through simulation, the typical distance of the reverberation chamber used in this embodiment can be determined to be 0.808 m. In practice, appropriate simulation parameters can be set according to requirements such as calculation time and accuracy to determine the typical distance of the used reverberation chamber.

[0054] 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 Figure 6 shown. Since the power delay spectrum (at a specific frequency) of the reverberation chamber is only related to the attenuation characteristics of the energy in the reverberation chamber and has nothing to do with the configuration of the stirrer rotation, in order to accurately calculate and clearly display the power delay spectrum of the reverberation chamber, Figure 6 only the measurement results in the scenario where the two stirrers rotate synchronously are plotted. From Figure 6 it can be seen that the PDP curves of the reverberation chamber at different frequencies all show typical exponential decay characteristics. At the same time, as the frequency increases, the attenuation rate of the power delay spectrum slightly decreases, but because the spacing between the three frequency points is not large, the difference in the attenuation rate is not significant.

[0055] Under the three scenarios of the stirrers to be measured adopted in the embodiment of the present invention, the measurement results of the energy without stirring in the reverberation chamber at 3.2 GHz are as Figure 7 shown. From Figure 7 it can be seen that the attenuation rate of the energy without stirring in Scenario 3 is significantly greater than the attenuation rates of the energy in Scenario 1 and Scenario 2, and the attenuation rate of the energy without stirring in Scenario 1 is the slowest. This is because the rotation regions (i.e., the equivalent boundaries) of the stirrers in the three scenarios are different: in Scenario 1, only the horizontal stirrer (length 0.7 m, rotation radius 0.41 m) rotates, in Scenario 2, only the vertical stirrer (length 1.2 m, rotation radius 0.41 m) rotates, and in Scenario 3, the two stirrers rotate synchronously. It can be seen that the larger the rotation region, the faster the attenuation rate of the energy without stirring. Generally speaking, the performance of the stirrer is related to the size of its rotation region, and the attenuation rate of the energy without stirring increases with the increase of the rotation region of the stirrer.

[0056] The measurement results of the damping time constant of the reverberation chamber under the three stirrer scenarios are as Figure 8As shown. In this embodiment, the inverse Fourier transform bandwidth used is 600 MHz, so the plotting range of the time constant is 2.7 GHz - 3.7 GHz. From Figure 8 It can be seen that for a specific stirrer, the corresponding damping time constant does not change significantly with frequency. In addition, the damping time constant can directly reflect the stirring ability of the stirrer to electromagnetic waves, and it increases with the increase of the rotating area of the stirrer. Since the damping time constant is extracted from the attenuation curve of the un-stirred energy in the reverberation chamber, so Figure 7 and Figure 8 the conclusions about the attenuation characteristics of the un-stirred energy at 3.2 GHz are consistent. However, Figure 7 it can only reflect the attenuation characteristics of the un-stirred energy at a specific frequency, while Figure 8 can clearly show the attenuation rate of the un-stirred energy in the entire frequency band.

[0057] In the embodiments of the present invention, the measurement results of the total scattering cross-section of the stirrer to be measured based on the mirror principle and the traditional method under three stirrer scenarios are as Figure 9 shown. From 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 the same, and are independent of the test frequency and test scenario. This result fully proves 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 by the present invention.

[0058] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A test model for the total scattering cross section of a reverberation chamber agitator based on the mirror principle, characterized in that: include: 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 losses in the reverberation chamber system are equivalent to the losses of the reverberation chamber wall, and the electric field strength of the electromagnetic wave after multiple reflections is obtained based on the initial electric field strength; The first electric field energy in the reverberation chamber after the electromagnetic wave has been reflected multiple times is obtained based on the electric field intensity after the electromagnetic wave has been reflected multiple times, the initial electric field energy, the number of mirrored objects after the electromagnetic wave has been reflected multiple times, and the total surface area of ​​the mirrored model; The time constant of the reverberation chamber is obtained according to the typical distance, the average reflection coefficient in all incident directions and polarization states, and the first electric field energy in the reverberation chamber after multiple reflections of the electromagnetic wave; According to the inner surface area of ​​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; According to the probability that the electromagnetic wave is not scattered by the stirrer after multiple reflections, the electric field strength after multiple reflections of the electromagnetic wave, the initial electric field energy, the number of mirrored objects after multiple reflections, and the total surface area of ​​the mirrored model, the second electric field energy that is not scattered by the stirrer in the reverberation chamber after multiple reflections of the electromagnetic wave is obtained; Obtaining the damping time constant of the stirrer 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 the electromagnetic wave is reflected multiple times; According to the damping time constant of the stirrer, the typical distance and the inner surface area of ​​the reverberation chamber, a test model of the total scattering cross section of the reverberation chamber stirrer is constructed, wherein the typical distance is the average propagation distance between the reflection points of the electromagnetic wave in the whole reflection process.

2. According to the test model of the total scattering cross section of the reverberation chamber agitator based on the mirror principle according to claim 1, it is characterized in that: The expression of the electric field strength of electromagnetic waves after multiple reflections is: In the formula, Indicates that electromagnetic waves pass through The electric field strength after the second reflection; represents the initial electric field strength; represents the average reflection coefficient for all incident directions and polarization states.

3. The test model of the total scattering cross section of a reverberation chamber agitator based on the mirror principle according to claim 1, characterized in that: The expression of the first electric field energy in the reverberation chamber after multiple reflections of the electromagnetic wave is: In the formula, The propagation time of electromagnetic waves Passing through The first electric field energy in the reverberation chamber after the second reflection; Indicates that electromagnetic waves pass through The first electric field energy in the reverberation chamber after the second reflection; represents the initial electric field energy; represents the speed of light; It represents the typical distance, that is, the average propagation distance between reflection points of the electromagnetic wave during the entire reflection process; represents the natural logarithm operation; Indicates that electromagnetic waves pass through The propagation time of the secondary reflection; represents the average reflection coefficient for all incident directions and polarization states; represents the initial electric field strength; Indicates passing The number of mirrored objects after reflection; Indicates passing The total surface area of ​​the mirror model after secondary reflection.

4. The test model of the total scattering cross section of a reverberation chamber agitator based on the mirror principle according to claim 1, characterized in that: The time constant of the reverberation chamber satisfies the expression: In the formula, represents the time constant of the reverberation chamber; represents the speed of light; It represents the typical distance, that is, the average propagation distance between reflection points of the electromagnetic wave during the entire reflection process; represents the average reflection coefficient for all incident directions and polarization states.

5. The test model of the total scattering cross section of a reverberation chamber agitator based on the mirror principle according to claim 1, characterized in that: The expression for the probability that an electromagnetic wave is not scattered by the stirrer after multiple reflections is: In the formula, Indicates that electromagnetic waves pass through The probability that the secondary reflection is not scattered by the stirrer; It represents the probability that the electromagnetic wave is scattered by the stirrer after 0 reflections; Indicates that electromagnetic waves pass through The probability of being scattered by the stirrer after the secondary reflection; represents the total scattering cross section of the stirrer; Represents the internal surface area of ​​the reverberation chamber.

6. The test model of the total scattering cross section of a reverberation chamber agitator based on the mirror principle according to claim 1, characterized in that: The expression of the second electric field energy in the reverberation chamber that is not scattered by the stirrer after multiple reflections of the electromagnetic wave is: In the formula, The propagation time of electromagnetic waves Passing through The second electric field energy in the reverberation chamber that is not scattered by the stirrer after the secondary reflection; Indicates that electromagnetic waves pass through The second electric field energy in the reverberation chamber that is not scattered by the stirrer after the secondary reflection; represents the initial electric field energy; represents the speed of light; It represents the typical distance, that is, the average propagation distance between reflection points of the electromagnetic wave during the entire reflection process; represents the total scattering cross section of the stirrer; Represents the inner surface area of ​​the reverberation chamber; represents the average reflection coefficient for all incident directions and polarization states; Indicates that electromagnetic waves pass through The propagation time of the secondary reflection; Indicates passing The number of mirrored objects after reflection; Indicates passing The total surface area of ​​the mirror model after secondary reflection; Indicates passing The unstirred electric field strength after the first reflection; represents the initial electric field strength.

7. The test model of the total scattering cross section of a reverberation chamber agitator based on the mirror principle according to claim 1, characterized in that: The damping time constant of the stirrer satisfies the expression: In the formula, represents the damping time constant of the stirrer; represents the time constant of the reverberation chamber; The propagation time of electromagnetic waves Passing through The second electric field energy in the reverberation chamber that is not scattered by the stirrer after the secondary reflection; represents the initial electric field energy.

8. The test model of the total scattering cross section of a reverberation chamber agitator based on the mirror principle according to claim 1, characterized in that: The expression of the test model of the total scattering cross section of the reverberation chamber agitator is: In the formula, represents the total scattering cross section of the stirrer; represents the damping time constant of the stirrer; Represents the inner surface area of ​​the reverberation chamber; represents the speed of light; It represents the typical distance, that is, the average propagation distance of the electromagnetic wave between the reflection points during the entire reflection process.

9. An application of a test model for the total scattering cross section of a reverberation chamber agitator based on the mirror principle, characterized in that: include: Substitute the inner surface area of ​​the reverberation chamber, the typical distance, the time constant of the reverberation chamber and the damping time constant of the stirrer to be tested into the test model described in any one of claims 1 to 8 to calculate the total scattering cross section of the stirrer to be tested.

10. The application of the test model of the total scattering cross section of a reverberation chamber agitator 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 tested are obtained based on the transmission coefficient.

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