A magnetic field adjustment device for testing electromagnetic shielding rooms

Abstract

This invention discloses a magnetic field adjustment device for testing electromagnetic shielding chambers, belonging to the technical field of magnetic field adjustment devices. It includes a support frame, on which a programmable electromagnetic wall and a magnetic field generating component are mounted. An acoustic recognition component is located at the end of the magnetic field generating component furthest from the programmable electromagnetic wall. Through the combined use of the resonant cavity and the acoustic recognition component, this invention can automatically identify the coil model and load a matching compensation coding matrix, achieving synergy between physical hardware and electromagnetic control. By establishing a functional relationship between the resonant frequency and temperature, it can dynamically compensate for magnetic field drift caused by coil heating, achieving adaptive stability of the magnetic field output. By dynamically adjusting the phase of the radiating surface layer through the programmable electromagnetic wall, the equivalent center of the virtual mirror field moves with the target receiver, enabling the virtual mirror field to move with the receiver, thus simulating a dynamic wireless charging scenario.

Description

Technical Field

[0001] This invention relates to the field of magnetic field conditioning equipment technology, and in particular to a magnetic field conditioning device for testing electromagnetic shielding rooms. Background Technology

[0002] Wireless charging technology refers to the non-contact transmission of electrical energy from the transmitter to the receiver through physical fields such as electromagnetic fields, electric fields, or microwaves. During the development of wireless charging systems, testing is required in an electromagnetically shielded room. In wireless charging test scenarios that require generating a large-area uniform magnetic field, researchers typically use a Helmholtz coil system. Two coils with the same radius and number of turns are placed parallel and coaxially, with a distance equal to the coil radius, and are supplied with current in the same direction, generating a large-area uniform magnetic field in the central region. By placing the receiver within this uniform region, its performance response under any position and orientation can be measured. Once the two coils of a Helmholtz coil are wound, their radius, number of turns, and spacing are fixed. When it is necessary to test receivers of different sizes, in order to obtain the optimal uniform area size and magnetic field strength, theoretically, Helmholtz coils of different specifications should be used. However, existing equipment can only achieve this by replacing the entire set of coils, which is cumbersome and frequent coil replacement can easily introduce mechanical positioning errors. During long-term wireless charging tests, the coil temperature rises due to Joule heating, which increases resistance and causes the magnetic field strength to decrease slowly. At the same time, the thermal expansion of the coil frame may change the coil geometry and spacing, affecting the uniformity of the magnetic field. However, the existing Helmholtz coil system is an open-loop structure, which cannot detect the changes in coil thermal expansion, nor can it automatically compensate for them. One of the cutting-edge research directions in wireless charging technology is to achieve dynamic charging of mobile devices, such as charging electric vehicles while they are in motion. Dynamic charging testing requires real-time monitoring of changes in transmission efficiency as the receiver moves and evaluation of the control system's response to coupling changes. The magnetic field distribution of traditional Helmholtz coils is fixed and cannot be dynamically adjusted according to changes in the receiver's position to optimize coupling efficiency, making it difficult to meet the testing requirements of dynamic wireless charging systems. To address this issue, a magnetic field adjustment device for testing electromagnetic shielding chambers is proposed. Summary of the Invention

[0003] The purpose of this invention is to solve the problem that existing magnetic field adjustment devices cannot meet the needs of cutting-edge research in wireless charging technology, and to propose a magnetic field adjustment device for testing electromagnetic shielding rooms.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A magnetic field adjustment device for testing an electromagnetic shielding room includes a support frame, an electromagnetic wall mounting bracket at one end of the support frame, a programmable electromagnetic wall on the electromagnetic wall mounting bracket, casters at the bottom of the support frame, and an adjustment frame on the support frame. A magnetic field generating component is provided at the end of the adjustment frame facing the programmable electromagnetic wall, and an acoustic recognition component is provided at the end of the adjustment frame away from the programmable electromagnetic wall. The programmable electromagnetic wall includes a shielding shell, a control box on the side of the shielding shell away from the magnetic field generating component, an FPGA controller inside the control box, and the shielding shell is open on the side facing the magnetic field generating component. Inside the shielding shell, from the inside out, there are a network layer, a copper layer, a dielectric substrate and a radiating surface layer, which are used to synthesize a virtual mirror field that matches the magnetic field generating component. The magnetic field generating component includes a frame, with fixing ears on both sides and the bottom of the frame. The fixing ears are detachably connected to the adjustment frame. A coil is wound on the frame, and three resonant cavities are equally spaced on the side of the frame facing the acoustic recognition component. The acoustic recognition component includes a bracket, a speaker mount at the top of the bracket, an interrogation speaker installed inside the speaker mount, three cantilever arms on the outer side wall of the bracket, microphone mounts at the ends of the cantilever arms, and echo microphones installed inside the microphone mounts.

[0005] Preferably, the radiating surface layer is composed of multiple metal patch units arranged in an array, and the metal patch units are arranged in a cross-shaped configuration.

[0006] Preferably, the back side of the dielectric substrate is provided with a plurality of PIN diodes corresponding to the metal patch unit. The PIN diodes are electrically connected to the network layer to form an addressing bias network, which is used to independently control the reflection phase of each metal patch unit to synthesize a virtual mirror field that meets the conditions.

[0007] Preferably, the reflectance of the metal patch unit is... The bias voltage of the PIN diode Control, satisfy:

[0008] Where m and n are the row and column indices of the metal patch cells in the array. It is a natural constant. The imaginary unit, The amplitude of reflection, For adjustable reflection phase, Indicates the application of the first line, number The bias voltage on the metal patch unit; Discrete phase states are achieved through digital encoding:

[0009] in, Number of bits; The synthesis of the virtual mirror field is determined by the far-field superposition of the array, at the target point. The magnetic field generated at the location for:

[0010] in, For the first Metal patch unit in position The unit magnetic field response produced at point r when the source is located at point r. and These represent the number of rows and columns of the metal patch cell array on the programmable electromagnetic wall, respectively. The FPGA controller is based on a preset virtual mirror field target distribution. The phase distribution is solved by an optimization algorithm. :

[0011] The virtual mirror field is dynamically synthesized.

[0012] Preferably, the resonant cavity includes a cavity formed on the frame and an acoustically transparent diaphragm covering the opening of the cavity. The plurality of resonant cavities have different geometric dimensions to form an acoustic fingerprint corresponding to different coil models.

[0013] Preferably, the interrogation speaker is a piezoelectric ceramic speaker, which is electrically connected to the control box of the programmable electromagnetic wall and is used to emit a wideband sweep sound wave when the magnetic field generating component stops working. The echo microphone is used to receive the sound wave echo reflected by the resonant cavity, and the control box identifies the model of the magnetic field generating component based on the spectral characteristics of the sound wave echo.

[0014] Preferably, the acquisition and processing of the acoustic echo follows the following formula: Suppose the frequency sweep sound wave emitted by the interrogation speaker is The total signal received by the echo microphone for:

[0015] in, For sound wave propagation path index, For the first The attenuation coefficient of the path, For the first The propagation delay of each path, For environmental noise, It is a time variable; Selecting a time window using time-domain gating Extracting target echo:

[0016] in, , , and Let be the minimum and maximum possible distances from the opening of the resonant cavity on the coil to the echo microphone. For the speed of sound, The target echo signal after time-domain gating extraction; right The spectrum is obtained by performing a Fourier transform. :

[0017] in As a frequency variable, the three resonant cavities each have a preset resonant frequency. , , In the spectrum Extract the presence of peaks near these three frequencies to form a three-dimensional acoustic fingerprint vector:

[0018] in, , and This is an indicator function; it takes a value of 1 when a significant peak is detected, and 0 otherwise. Will The fingerprints are matched against standard fingerprints in the database, and the coil model number with the highest matching degree is recorded as the identification number. The FPGA controller according to Load the corresponding compensation encoding matrix This is used to control the phase distribution of the radiating surface layer so that the synthesized virtual mirror field matches the current coil. Preferably, the acoustic recognition component is also used to monitor the amplitude and resonant frequency of the acoustic echo signal, and to determine the mechanical state of the skeleton according to a preset threshold. Let the theoretical resonant frequency of the x-th resonant cavity be... The theoretical echo amplitude is ,in In the actual spectrum In the theoretical frequency Extracting the actual peak amplitude from the vicinity and actual peak frequency ; Define amplitude deviation rate: ,

[0019] Define frequency deviation rate: ,

[0020] in, It is the first The echo sound pressure amplitude deviation rate of each resonant cavity, when any If the value exceeds a preset threshold, it is determined that the coil has become loose or its position has shifted. It is the first The return frequency deviation rate of each resonant cavity, when any When the value exceeds a preset threshold, the skeleton is determined to be deformed. Before leaving the factory, the functional relationship between the resonant frequency and temperature is calibrated through a temperature rise test. :

[0021] in, This is the current temperature at the resonant cavity. For ambient temperature, For the first The linear thermistor of each resonant cavity, For the first The nonlinear thermistor coefficient of a resonant cavity; During online operation, the current temperature at the resonant cavity is obtained by solving the following equation. :

[0022] Right now:

[0023] The temperature was measured in each of the three resonant cavities. , , Calculate the average temperature rise and temperature gradient characteristics Together they form the thermal state vector. :

[0024]

[0025]

[0026] When running online, the FPGA controller determines the current thermal state vector. By looking up the table from the thermal compensation matrix The required phase compensation amount for each metal patch unit is obtained in the following way:

[0027] The phase compensation amount The phase distribution superimposed on the radiating surface layer enables automatic compensation for magnetic field thermal drift.

[0028] Preferably, the three cantilever arms on the support are respectively positioned to correspond to the positions of the three resonant cavities, so that the echo microphone at the end of each cantilever arm is aligned with the opening of the corresponding resonant cavity.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention sets resonant cavities of different geometric sizes at equal intervals on the skeleton, and combines the wideband sweep sound waves and echoes emitted by the acoustic recognition component during the working gap to form a three-dimensional acoustic fingerprint vector. After matching with the pre-stored database, it automatically identifies the model of the currently installed coil. The programmable electromagnetic wall automatically loads the compensation coding matrix that matches the coil model according to the identification result, and dynamically synthesizes the optimal virtual mirror field, realizing the synergy between physical hardware and electromagnetic control.

[0030] 2. This invention establishes a functional relationship between the resonant frequency and the coil temperature, transforming the measured frequency offset into a thermal state vector. The programmable electromagnetic wall dynamically adjusts the phase and amplitude distribution of the virtual mirror field based on the coil thermal state information obtained from acoustic feedback, and compensates in real time for magnetic field drift caused by coil heating, so that the synthesized magnetic field is always maintained within the target accuracy range, achieving adaptive matching between magnetic field output and environmental changes.

[0031] 3. By setting up a programmable electromagnetic wall, this invention can dynamically adjust the phase distribution of the radiating surface layer in simulated dynamic wireless charging scenarios, so that the equivalent center of the virtual mirror field moves with the target receiver and maintains the optimal magnetic field coupling state during the movement of the target receiver. This expands the testing of wireless charging systems from static position testing to dynamic scenario simulation, providing a testing platform that is closer to real working conditions for the research and evaluation of practical application scenarios such as dynamic charging of electric vehicles. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of a magnetic field adjustment device for testing an electromagnetic shielding room, as proposed in this invention. Figure 2 This is a schematic diagram of the magnetic field generating component in a magnetic field conditioning device for testing an electromagnetic shielding room, as proposed in this invention. Figure 3 This is a cross-sectional view of the resonant cavity structure in a magnetic field adjustment device for testing an electromagnetic shielding room, as proposed in this invention. Figure 4This is a structural assembly diagram of a programmable electromagnetic wall in a magnetic field conditioning device for testing an electromagnetic shielding room, as proposed in this invention. Figure 5 Figure 4 Enlarged view of the structure at point A in the middle; Figure 6 This is an assembly diagram of the back structure of the dielectric substrate in a magnetic field conditioning device for testing an electromagnetic shielding room, as proposed in this invention. Figure 7 This is a schematic diagram of the back structure of the programmable electromagnetic wall in a magnetic field adjustment device for testing an electromagnetic shielding room, as proposed in this invention. Figure 8 This is a structural assembly diagram of the acoustic identification component in a magnetic field adjustment device for testing an electromagnetic shielding room, as proposed in this invention. Figure 9 This is a front structural diagram of the acoustic recognition component in a magnetic field adjustment device for testing an electromagnetic shielding room, as proposed in this invention.

[0033] In the diagram: 1. Support frame; 2. Electromagnetic wall mounting bracket; 3. Shielding shell; 4. Control box; 5. Network layer; 6. Copper layer; 7. Dielectric substrate; 8. Radiation surface layer; 9. Skeleton; 10. Coil; 11. Resonant cavity; 12. Bracket; 13. Speaker mount; 14. Interrogation speaker; 15. Cantilever; 16. Microphone mount; 17. Echo microphone; 18. PIN diode. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] Example, refer to Figures 1 to 9 A magnetic field adjustment device for testing an electromagnetic shielding room includes a support frame 1, an electromagnetic wall mounting bracket 2 at one end of the support frame 1, a programmable electromagnetic wall on the electromagnetic wall mounting bracket 2, a counterweight plug at the other end of the support frame 1, movable wheels at the bottom of the support frame 1, an adjustment frame on the support frame 1, a magnetic field generating component at the end of the adjustment frame facing the programmable electromagnetic wall, and an acoustic recognition component at the end of the adjustment frame away from the programmable electromagnetic wall. The programmable electromagnetic wall includes a shielding shell 3. A control box 4 is provided on the side of the shielding shell 3 away from the magnetic field generating component. An FPGA controller is provided in the control box 4. The shielding shell 3 is open on the side facing the magnetic field generating component. From the inside out, a network layer 5, a copper metal layer 6, a dielectric substrate 7, and a radiating surface layer 8 are arranged in sequence to synthesize a virtual mirror field that matches the magnetic field generating component. The magnetic field generating component includes a frame 9, with fixing ears on both sides and the bottom of the frame 9. The fixing ears are detachably connected to the adjustment frame. A coil 10 is wound on the frame 9. Three resonant cavities 11 are equally spaced on the side of the frame 9 facing the acoustic recognition component. The acoustic recognition component includes a bracket 12, a speaker mount 13 at the top of the bracket 12, an interrogation speaker 14 installed inside the speaker mount 13, three cantilever arms 15 on the outer side wall of the bracket 12, a microphone mount 16 at the end of the cantilever arm 15, and an echo microphone 17 installed inside the microphone mount 16.

[0038] Furthermore, the radiating surface layer 8 is composed of multiple metal patch units arranged in an array. The metal patch units are arranged in a cross-shaped manner. The symmetrical structure of the cross-shaped metal patch units gives them consistent response characteristics to orthogonally polarized electromagnetic waves, which is beneficial for synthesizing a uniform virtual mirror field over a wide angle range. Furthermore, the back of the dielectric substrate 7 is provided with a plurality of PIN diodes 18 corresponding to the metal patch unit. The PIN diodes 18 are electrically connected to the network layer 5 to form an addressing bias network, which is used to independently control the reflection phase of each metal patch unit in order to synthesize a virtual mirror field that meets the conditions. Furthermore, the reflectivity of the metal patch unit The bias voltage of PIN diode 18 Control, satisfy:

[0039] Where m and n are the row and column indices of the metal patch cells in the array. It is a natural constant. The imaginary unit, The amplitude of reflection, For adjustable reflection phase, Indicates the application of the first line, number The bias voltage on the metal patch unit; Discrete phase states are achieved through digital encoding:

[0040] in, Number of bits; The synthesis of the virtual mirror field is determined by the far-field superposition of the array, at the target point. The magnetic field generated at the location for:

[0041] in, For the first Metal patch unit in position The unit magnetic field response produced at point r when the source is located at point r. and These represent the number of rows and columns of the metal patch cell array on the programmable electromagnetic wall, respectively. The FPGA controller distributes the target according to the preset virtual mirror field. The phase distribution is solved by an optimization algorithm. :

[0042] To achieve dynamic synthesis of virtual mirror fields; The further advantage of adopting the above is that, by independently controlling the reflection phase of each metal patch unit, the programmable electromagnetic wall can dynamically synthesize virtual mirror fields of arbitrary shapes according to different coil 10 models and test requirements. The virtual mirror field synthesized by a single coil 10 and the programmable electromagnetic wall replaces the traditional structure of two coils 10, solving the problem of fixed geometry and inability to adjust the size of the uniform region in traditional Helmholtz coils. Different equivalent spacing and different uniform region sizes can be achieved through software programming, providing flexible adaptability for the test requirements of receivers of different sizes in wireless charging system testing.

[0043] Furthermore, the resonant cavity 11 includes a cavity formed on the frame 9 and an acoustically transparent membrane covering the cavity opening. Multiple resonant cavities 11 have different geometric dimensions to form acoustic fingerprints corresponding to different coil 10 models, so that each coil 10 model can form a unique acoustic fingerprint, providing a reliable feature basis for subsequent automatic identification and avoiding errors caused by manual identification. Furthermore, the interrogation speaker 14 is a piezoelectric ceramic speaker. The interrogation speaker 14 is electrically connected to the control box 4 of the programmable electromagnetic wall and is used to emit a wideband sweep sound wave when the magnetic field generating component stops working. The echo microphone 17 is used to receive the sound wave echo reflected by the resonant cavity 11. The control box 4 identifies the model of the magnetic field generating component based on the spectral characteristics of the sound wave echo. Furthermore, the acquisition and processing of acoustic echoes follow the formula below: Suppose the frequency sweep sound wave emitted by the interrogation speaker 14 is The total signal received by echo microphone 17 for:

[0044] in, For sound wave propagation path index, For the first The attenuation coefficient of the path, For the first The propagation delay of each path, For environmental noise, It is a time variable;

[0045] in, , and Let these be the minimum and maximum possible distances from the opening of the resonant cavity 11 on coil 10 to the echo microphone 17. For the speed of sound, The target echo signal after time-domain gating extraction; right The spectrum is obtained by performing a Fourier transform. :

[0046] in As frequency variables, the three resonant cavities 11 each have a preset resonant frequency. , , In the spectrum Extract the presence of peaks near these three frequencies to form a three-dimensional acoustic fingerprint vector:

[0047] in, , and This is an indicator function; it takes a value of 1 when a significant peak is detected, and 0 otherwise. Will The fingerprints are matched against standard fingerprints in the database, and the coil model number with the highest matching degree is recorded as the identification number. FPGA controller according to Load the corresponding compensation encoding matrix It is used to control the phase distribution of the radiating surface layer 8 so that the synthesized virtual mirror field matches the current coil 10.

[0048] Furthermore, the acoustic recognition component is also used to monitor the amplitude and resonant frequency of the acoustic echo signal of the resonant cavity 11 during working intervals, determine the mechanical state of the coil 10 according to a preset threshold, and automatically correct the magnetic field deviation before the threshold is reached. Let the theoretical resonant frequency of the x-th resonant cavity 11 be... The theoretical echo amplitude is ,in In the actual spectrum In the theoretical frequency Extracting the actual peak amplitude from the vicinity and actual peak frequency ; Define amplitude deviation rate: ,

[0049] Define frequency deviation rate: ,

[0050] in, It is the first The echo sound pressure amplitude deviation rate of each resonant cavity 11, when any If the value exceeds a preset threshold, it is determined that coil 10 has become loose or shifted in position. It is the first The echo frequency deviation rate of each resonant cavity 11, when any When the value exceeds a preset threshold, it is determined that the coil 10 frame 9 has deformed; Before leaving the factory, the functional relationship between the resonant frequency and temperature is calibrated through a temperature rise test:

[0051] in, For temperature, For ambient temperature, For the first The linear thermistor coefficient of each resonant cavity 11, For the first The nonlinear thermistor coefficient of each resonant cavity 11; During online operation, the current temperature at resonant cavity 11 is obtained by solving the following equation. :

[0052] Right now:

[0053] The temperatures of the three resonant cavities 11 were measured respectively. , , Calculate the average temperature rise and temperature gradient characteristics Together they form the thermal state vector. :

[0054]

[0055]

[0056] When running online, the FPGA controller determines the current thermal state vector. By looking up the table from the thermal compensation matrix The required phase compensation amount for each metal patch unit is obtained in the following way:

[0057] Phase compensation amount The phase distribution superimposed on the radiating surface layer 8 enables automatic compensation for magnetic field thermal drift; It should be noted that the thermal compensation matrix needs to be pre-calibrated for each type of coil before leaving the factory.

[0058] The further advantage of adopting the above is that, during the interval when the magnetic field generating component stops working, the acoustic recognition component can be used to determine online whether the coil 10 has become loose, shifted in position, or deformed in the frame 9, thereby realizing the function of sensing changes in its own mechanical state. At the same time, it can compensate for magnetic field drift caused by the heating of the coil 10 in real time, so that the equipment can maintain the stability of the magnetic field output during long-term continuous operation and improve the repeatability and reliability of test data.

[0059] Furthermore, the three cantilever arms 15 on the bracket 12 are respectively positioned to correspond to the positions of the three resonant cavities 11, so that the echo microphone 17 at the end of each cantilever arm 15 is aligned with the opening of the corresponding resonant cavity 11. When using this invention, the device is moved to the predetermined test position in the electromagnetic shielding room by the movable wheels, the movable wheels are locked to fix the device, and the magnetic field generating component of the corresponding specification is selected according to the specific requirements of the test. Different specifications of coil 10 correspond to different magnetic field strength ranges and uniform area sizes. The installation of coil 10 is completed by the quick-change structure of the fixing lug and the adjustment frame, and the axial distance between the magnetic field generating component and the programmable electromagnetic wall is precisely adjusted to the preset position by the adjustment frame. After the device is powered on, the acoustic recognition component starts. The interrogation speaker 14 emits a wideband sweep sound wave when the magnetic field generating component is not powered on. The three echo microphones 17 receive the sound wave echoes reflected by the three resonant cavities 11 respectively. The signal processing unit metal patch unit in the control box 4 performs time-domain gated filtering and spectrum analysis on the echo signal, extracts the characteristic frequencies of the three resonant cavities 11, forms a three-dimensional acoustic fingerprint vector, and automatically identifies the model of the currently installed coil 10 after matching with the pre-stored database. After the identification is completed, the acoustic recognition component is powered off to avoid affecting the test magnetic field. The specific working method of this acoustic recognition component will not be described in detail below. In the test of simulating dynamic wireless charging scenario, the receiver under test is placed on a motion platform in the existing technology. During the test, the equivalent center of the virtual mirror field can be adjusted to follow the movement of the receiver on the motion platform, thereby maintaining stable magnetic field coupling conditions during the movement of the receiver and realizing the scenario of simulating the target device supplying power while in motion.

[0060] During the test interval, the acoustic recognition component was activated again to monitor the acoustic echo characteristics of the resonant cavity 11 in real time. The calculated echo sound pressure amplitude deviation rate... Or echo frequency deviation rate When the frequency deviation exceeds the preset fault threshold, the system determines that the magnetic field generating component has a mechanical fault such as loosening, displacement or deformation, and issues an alarm. When the frequency deviation rate does not exceed the fault threshold, the system calculates the current temperature of coil 10 based on the frequency deviation and controls the programmable electromagnetic wall to compensate for the thermal drift of the magnetic field. This enables the equipment to automatically suppress the magnetic field changes caused by the heating of coil 10 during long-term continuous operation without manual intervention or shutdown for cooling, thereby improving the stability of the magnetic field output and the repeatability of test data.

[0061] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A magnetic field adjustment device for testing electromagnetic shielding chambers, comprising a support frame (1), characterized in that, The support frame (1) is provided with an electromagnetic wall mounting bracket (2) at one end. The electromagnetic wall mounting bracket (2) is provided with a programmable electromagnetic wall. The support frame (1) is provided with a movable wheel at the bottom. The support frame (1) is provided with an adjustment frame. The end of the adjustment frame facing the programmable electromagnetic wall is provided with a magnetic field generating component. The end of the adjustment frame away from the programmable electromagnetic wall is provided with an acoustic recognition component. The programmable electromagnetic wall includes a shielding shell (3), and a control box (4) is provided on the side of the shielding shell (3) away from the magnetic field generating component. An FPGA controller is provided in the control box (4). The shielding shell (3) is open on the side facing the magnetic field generating component. Its interior is provided with a network layer (5), a copper metal layer (6), a dielectric substrate (7) and a radiating surface layer (8) from the inside out, for synthesizing a virtual mirror field that matches the magnetic field generating component. The magnetic field generating component includes a frame (9), with fixing ears on both sides and bottom of the frame (9). The fixing ears are detachably connected to the adjustment frame. A coil (10) is wound on the frame (9). Three resonant cavities (11) are equally spaced on the side of the frame (9) facing the acoustic recognition component. The acoustic recognition component includes a bracket (12), a speaker mount (13) is provided at the top of the bracket (12), an interrogation speaker (14) is installed in the speaker mount (13), three cantilever arms (15) are provided on the outer side wall of the bracket (12), a microphone mount (16) is provided at the end of the cantilever arms (15), and an echo microphone (17) is installed in the microphone mount (16).

2. The magnetic field adjustment device for testing an electromagnetic shielding room according to claim 1, characterized in that, The radiating surface layer (8) is composed of multiple metal patch units arranged in an array, and the metal patch units are arranged in a cross shape.

3. The magnetic field adjustment device for testing an electromagnetic shielding room according to claim 2, characterized in that, The back of the dielectric substrate (7) is provided with a plurality of PIN diodes (18) corresponding to the metal patch unit. The PIN diodes (18) are electrically connected to the network layer (5) to form an addressing bias network, which is used to independently control the reflection phase of each metal patch unit to synthesize a virtual mirror field that meets the conditions.

4. The magnetic field adjustment device for testing an electromagnetic shielding room according to claim 3, characterized in that, The reflectance of the metal patch unit The bias voltage of the PIN diode (18) Control, satisfy: Where m and n are the row and column indices of the metal patch cells in the array. It is a natural constant. The imaginary unit, The amplitude of reflection, For adjustable reflection phase, Indicates the application of the first line, number The bias voltage on the metal patch unit; Discrete phase states are achieved through digital encoding: in, Number of bits; The synthesis of the virtual mirror field is determined by the far-field superposition of the array, at the target point. The magnetic field generated at the location for: in, For the first Metal patch unit in position The unit magnetic field response produced at point r when the source is located at point r. and These represent the number of rows and columns of the metal patch cell array on the programmable electromagnetic wall, respectively. The FPGA controller is based on a preset virtual mirror field target distribution. The phase distribution is solved by an optimization algorithm. : The virtual mirror field is dynamically synthesized.

5. The magnetic field adjustment device for testing an electromagnetic shielding room according to claim 1, characterized in that, The resonant cavity (11) includes a cavity formed on the frame (9) and a sound-permeable membrane covering the cavity opening. Multiple resonant cavities (11) have different geometric dimensions to form acoustic fingerprints corresponding to different coil (10) models.

6. The magnetic field adjustment device for testing an electromagnetic shielding room according to claim 5, characterized in that, The interrogation speaker (14) is a piezoelectric ceramic speaker. The interrogation speaker (14) is electrically connected to the control box (4) of the programmable electromagnetic wall and is used to emit a wideband sweep sound wave when the magnetic field generating component stops working. The echo microphone (17) is used to receive the sound wave echo reflected by the resonant cavity (11). The control box (4) identifies the model of the magnetic field generating component based on the spectral characteristics of the sound wave echo.

7. The magnetic field adjustment device for testing an electromagnetic shielding room according to claim 6, characterized in that, The acquisition and processing of the acoustic echo follow the following formula: Suppose the frequency sweeping sound wave emitted by the interrogation loudspeaker (14) is The total signal received by the echo microphone (17) for: in, For sound wave propagation path index, For the first The attenuation coefficient of the path, For the first The propagation delay of each path, For environmental noise, It is a time variable; Selecting a time window using time-domain gating Extracting target echo: in, , , and Let the minimum and maximum possible distances be the opening of the resonant cavity (11) on the coil (10) to the echo microphone (17). For the speed of sound, The target echo signal after time-domain gating extraction; right The spectrum is obtained by performing a Fourier transform. : in As a frequency variable, the three resonant cavities (11) each have a preset resonant frequency. , , In the spectrum Extract the presence of peaks near these three frequencies to form a three-dimensional acoustic fingerprint vector: in, , and This is an indicator function; it takes a value of 1 when a significant peak is detected, and 0 otherwise. Will The fingerprints are matched against standard fingerprints in the database, and the coil (10) model number with the highest matching degree is recorded as the identification number. The FPGA controller according to Load the corresponding compensation encoding matrix , used to control the phase distribution of the radiating surface layer (8) so that the synthesized virtual mirror field matches the current coil (10).

8. The magnetic field adjustment device for testing an electromagnetic shielding room according to claim 7, characterized in that, The acoustic recognition component is also used to monitor the amplitude and resonant frequency of the acoustic echo signal, and to determine the mechanical state of the skeleton (9) according to a preset threshold. Let the theoretical resonant frequency of the x-th resonant cavity (11) be... The theoretical echo amplitude is ,in In the actual spectrum In the theoretical frequency Extracting the actual peak amplitude from the vicinity and actual peak frequency ; Define amplitude deviation rate: ， Define frequency deviation rate: ， in, It is the first The echo sound pressure amplitude deviation rate of each resonant cavity (11), when any When the value exceeds a preset threshold, it is determined that the coil (10) has become loose or shifted in position. It is the first The echo frequency deviation rate of the resonant cavity (11), when any When the value exceeds the preset threshold, the skeleton (9) is determined to be deformed; Before leaving the factory, the functional relationship between the resonant frequency and temperature is calibrated through a temperature rise test: in, The current temperature at the resonant cavity (11) is... For ambient temperature, For the first The linear thermistor coefficient of each resonant cavity (11), For the first The nonlinear thermistor coefficient of each resonant cavity (11); During online operation, the current temperature at the resonant cavity (11) is obtained by solving the following equation. : Right now: The temperatures of the three resonant cavities (11) were measured respectively. , , Calculate the average temperature rise and temperature gradient characteristics Together they form the thermal state vector. : When running online, the FPGA controller determines the current thermal state vector. By looking up the table from the thermal compensation matrix The required phase compensation amount for each metal patch unit is obtained in the following way: The phase compensation amount The phase distribution superimposed on the radiation surface layer (8) enables automatic compensation for magnetic field thermal drift.

9. The magnetic field adjustment device for testing an electromagnetic shielding room according to claim 1, characterized in that, The three cantilever arms (15) on the bracket (12) are respectively positioned to correspond to the positions of the three resonant cavities (11), so that the echo microphone (17) at the end of each cantilever arm (15) is aligned with the opening of the corresponding resonant cavity (11).

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