Dynamic electromagnetic reverberation chamber based on plasma regulation and control and control method thereof

Abstract

The invention discloses a dynamic electromagnetic reverberation chamber based on plasma regulation and control and a control method thereof, and belongs to the technical field of electromagnetic testing. A plasma array module and a driving control module are arranged on the inner wall surface of a cavity of the reverberation chamber; the electronic density and the collision frequency of the plasma unit are changed by adjusting the discharge parameters of the plasma unit in real time, so that the equivalent quality factor Q value, the normalized field intensity and the energy attenuation time constant of the reverberation chamber are dynamically and continuously adjusted and controlled; the limitation that a traditional reverberation chamber depends on a fixed wave-absorbing material or a mechanical stirrer is broken through, millisecond-level rapid switching of key electromagnetic parameters is achieved, the device has the advantages of being high in space efficiency, compatible in broadband and flexible in working mode, and the testing efficiency and the application range of the reverberation chamber are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic testing technology, specifically to a dynamic electromagnetic reverberation chamber based on plasma control and its control method. Background Technology

[0002] An electromagnetic reverberation chamber is a testing device capable of generating a statistically uniform, isotropic electromagnetic field environment. It is widely used in electromagnetic compatibility testing, antenna efficiency measurement, and research on the electromagnetic properties of materials. Traditional reverberation chambers mainly achieve field homogenization by altering the modal distribution of the cavity through mechanical stirring with rotating metal blades or frequency tuning.

[0003] However, traditional reverberation chambers have inherent technical limitations: First, their quality factor (Q) is mainly determined by the chamber structure, metal wall losses, and fixed absorbing materials. Once constructed, it is difficult to dynamically adjust, making it inflexible to adapt to different testing scenarios, such as detecting weak signals with high Q values ​​and rapid energy decay with low Q values. Second, mechanical stirrers suffer from slow response times (usually greater than 100ms) and large occupancy of internal chamber space (usually exceeding 15% of the volume), limiting testing efficiency and layout flexibility. Finally, frequency tuning methods can only achieve high field strength at discrete resonant frequencies, making it difficult to meet the needs of wideband continuous testing.

[0004] As the fourth state of matter, plasma's equivalent dielectric constant and conductivity can be dynamically adjusted through discharge parameters such as voltage and frequency, thereby enabling flexible control over the reflection and absorption characteristics of electromagnetic waves. Currently, plasma technology has been applied in fields such as radar stealth and communication filtering, but there is no publicly available scheme that combines plasma technology with a reverberation chamber to achieve dynamic control of the chamber's electromagnetic parameters.

[0005] Therefore, developing a novel reverberation chamber capable of dynamically, rapidly, and continuously adjusting key electromagnetic parameters has become a pressing technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a dynamic electromagnetic reverberation chamber based on plasma control and its control method. The plasma unit is embedded in the wall of the reverberation chamber, and the reflection / absorption characteristics of the electromagnetic waves are changed by adjusting the plasma discharge parameters in real time, so as to realize the dynamic control of the cavity Q value, normalized field strength and time constant.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a dynamic electromagnetic reverberation chamber based on plasma control, comprising a reverberation chamber body, a plasma array module, a drive control module, and a feedback monitoring module; the plasma array module is embedded in the six inner walls of the reverberation chamber body, the drive control module is electrically connected to the plasma array module, and dynamically adjusts the equivalent quality factor Q value of the reverberation chamber; the feedback monitoring module is disposed within the reverberation chamber body and is signal-connected to the drive control module;

[0008] The plasma array module is composed of multiple plasma units arranged in a honeycomb pattern. By adjusting the driving voltage and pulse frequency, the plasma electron density and collision frequency are controlled, thereby changing its equivalent electromagnetic parameters.

[0009] The drive control module includes a high-voltage pulse generator and a zone control logic unit; it is used to output pulse signals with adjustable parameters and realize independent zone control of the plasma array.

[0010] The feedback monitoring module includes a broadband electric field probe array and an adaptive control unit, which are used to collect field strength data in the cavity in real time and generate parameter adjustment commands to achieve closed-loop control.

[0011] Furthermore, the plasma unit employs a dielectric barrier discharge structure or a radio frequency driven ionization source. Each unit contains two layers of metal electrodes with an intermediate dielectric layer. The metal electrode thickness of the plasma unit is 0.1 mm, and the intermediate dielectric layer is an Al2O3 ceramic or PVC film with a thickness of 1 mm. The size of the plasma unit is 10 cm × 10 cm, and the spacing between two adjacent plasma units is 1 / 8 to 1 / 4 of the lowest frequency wavelength in the operating frequency band. The plasma array module controls the electron density n by adjusting the driving parameters. e The range is 10 9 -10 12 cm -3 Collision frequency v c The range is 10 8 -10 11 Hz.

[0012] Furthermore, the high-voltage pulse generator of the drive control module adopts a full-bridge inverter topology, with an output drive voltage range of 0-10kV and a pulse frequency range of 1kHz-10MHz; the partition control logic unit divides the plasma array module into multiple independent control regions and supports switching between global mode and gradient mode operating modes.

[0013] Furthermore, the broadband electric field probe array of the feedback monitoring module consists of several broadband electric field probes arranged at equal intervals inside the reverberation chamber body, with a frequency range of 100MHz-20GHz. The adaptive algorithm unit fits the field strength data based on the least squares method, generates plasma parameter adjustment commands, and realizes closed-loop control. The response time of the closed-loop control is <10ms.

[0014] Furthermore, the reverberation chamber has three operating modes:

[0015] Total Internal Reflection High Q Mode: All plasma units are turned off, the reverberation chamber wall is equivalent to an all-metal surface, and the Q value is determined by the inherent losses of the reverberation chamber; Q > 50,000; suitable for high-sensitivity receiver testing and weak electromagnetic signal detection scenarios.

[0016] Full absorption low-Q mode: Apply a high-frequency pulse of >5MHz and a high-voltage pulse of >8kV to all plasma units, so that ω p Significantly higher than the operating frequency, the Q value drops to the 200-500 range; suitable for pulse testing to quickly clear residual energy from the cavity;

[0017] Gradient loss mode: Independently control plasma parameters in different wall regions to form a non-uniform field distribution in the reverberation chamber body, optimize the field uniformity in specific regions, and achieve a field strength standard deviation of <1dB.

[0018] Furthermore, the plasma layer formed by the plasma array module has a thickness of 3-5 cm and a power consumption of <200 W / m² in the activated state.

[0019] A control method for the aforementioned plasma-controlled dynamic electromagnetic reverberation chamber, characterized in that it includes:

[0020] System initialization: Complete the connection and calibration of the plasma array, drive control module and feedback monitoring module, and determine the initial operating parameters;

[0021] Target parameter input: Set the target quality factor, normalized field strength, and energy decay time constant of the electromagnetic reverberation chamber according to the test requirements;

[0022] Plasma parameter control: The drive control module outputs pulse signals according to the target parameters to adjust the plasma electron density and collision frequency, thereby changing its equivalent dielectric constant and conductivity.

[0023] Closed-loop optimization: The feedback monitoring module collects field strength data in real time, generates adjustment instructions through an adaptive algorithm, and dynamically corrects the plasma operating parameters until the target value is reached.

[0024] Furthermore, during the plasma parameter control process, the Q value is dynamically adjusted by switching the plasma operating state:

[0025] The expression for the plasma equivalent relative permittivity is:

[0026]

[0027] Where, ω p ω is the plasma frequency, and ω is the angular frequency of the incident electromagnetic wave. The electron collision frequency;

[0028] The plasma frequency is determined by the following formula:

[0029]

[0030] In the formula, The amount of electron charge. The vacuum permittivity, For electronic quality, Electron density;

[0031] Through plasma frequency ω p Different operating states are achieved through the relationship between the incident electromagnetic wave angular frequency ω and the frequency ω:

[0032] When the plasma frequency ω p When the incident electromagnetic wave has an angular frequency of ω, the plasma exhibits low-loss dielectric characteristics, and the electromagnetic wave is partially reflected. The cavity Q value is determined by the inherent loss, and Q>50,000.

[0033] When the plasma frequency ω p When the incident electromagnetic wave has an angular frequency of ω, the plasma exhibits the characteristics of a high-loss medium. The electromagnetic wave energy is dissipated into heat energy through collisions, and the Q value decreases significantly, dropping to the range of 200-500.

[0034] Precise control can be achieved by adjusting the drive voltage and frequency. and This allows for continuous adjustment of the Q value, thereby increasing the effective Q value of the cavity. The calculation formula is:

[0035]

[0036] Among them, U stored The energy stored in the cavity represents the total amount of electromagnetic energy stored within the cavity; P loss_plasma P represents the plasma loss power, reflecting the rate at which the plasma absorbs and consumes electromagnetic energy. loss_cavity This represents the inherent power loss of the cavity, reflecting the unavoidable energy loss of the cavity itself.

[0037] The beneficial effects of this invention are: by using electronic control, key parameters such as the Q value of the reverberation chamber, field uniformity, and energy decay time constant can be switched rapidly and continuously at the millisecond level, which greatly improves the testing efficiency, meets the testing scenarios with strict requirements for rapid response, and breaks through the limitation of fixed parameters in traditional reverberation chambers.

[0038] The plasma layer is only 3-5cm thick, saving more than 85% of space compared to traditional absorbing materials, which facilitates the installation and layout of testing equipment. It only consumes energy when activated, resulting in low operating costs. It can also work in conjunction with mechanical stirrers and frequency tuners, expanding its application scenarios.

[0039] By precisely adjusting the discharge parameters and plasma electron density, it is possible to adapt to wide-band testing requirements from MHz to GHz, effectively solving the problem that traditional technologies are only applicable to narrow bands.

[0040] It supports multiple working modes such as global uniform control and partitioned gradient control, and can meet the needs of various application scenarios, from high-sensitivity signal detection to rapid pulse testing and complex field distribution optimization. Attached Figure Description

[0041] The present invention will be further described below with reference to the accompanying drawings:

[0042] Figure 1 This is the overall system architecture diagram of the present invention;

[0043] Figure 2 The simulation shows that the Q value varies with the driving voltage, and the Q value is continuously adjustable from 50,000 (0kV) to 300 (10kV).

[0044] Figure 3 The simulation comparison chart shows the normalized field strength, and the field distribution cloud map is given for the traditional mechanical stirring mode and the mode with added plasma. The field uniformity is improved by 42% in the gradient mode.

[0045] Figure 4 This is the curve showing the relationship between the time constant τ and the plasma density, indicating that τ ranges from 12 ms to n e =0 to 0.15ms, n e =1.5×10 12 cm -3 Continuously adjustable;

[0046] Figure 5 This is a schematic diagram of a plasma unit structure. The vertical lines represent positive electrodes, the squares represent negative electrodes, and there is a thin layer of insulator separating the two electrodes. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to embodiments and specific implementation methods:

[0048] Example 1

[0049] Q-value dynamic adjustment test

[0050] Step 1: System initialization: Install 240 DBD plasma units on the inner wall of a 3m×2.5m×2.5m reverberation chamber, with a spacing of 1 / 4 of the 200MHz wavelength, 37.5cm; connect the drive control module and the field probe array, and calibrate the initial state.

[0051] Step 2: High Q mode establishment: Turn off the plasma unit, start the mechanical stirrer at 10 rpm, inject a 20W, 1GHz continuous wave signal; collect the S21 data of the test area, calculate the initial Q value to be 52,000, with an error of <3% compared to the theoretical value.

[0052] Step 3: Low Q mode switching: Apply an 8kV, 5MHz pulse with a duty cycle of 50% to all plasma units and monitor n. e Increased to 1.5×10 11 cm -3 ;

[0053] The field strength amplitude decreased by 40%, the Q value dropped to 350, and the response time was 8ms.

[0054] After the excitation source is turned off, the time τ for the energy to decay to 1 / e is shortened from 12ms to 0.2ms.

[0055] Step 4: Continuous Q-value adjustment: Set the target Q-value to 10000, and the control module adjusts the drive voltage to 3.2kV ​​and the frequency to 1.2MHz using the PID algorithm;

[0056] The measured Q value was 9,850 with an error of 1.5%, verifying the continuous adjustment capability.

[0057] Example 2

[0058] Multi-region field uniformity optimization

[0059] Step 1: Set the gradient mode: Set the top wall plasma to high loss, n e =1.2×10 12 cm -3 Drive voltage 9kV, sidewall surface set to medium loss, n e =6×10 11 cm -3 Drive voltage 6kV, bottom maintains total reflection;

[0060] A 2-18 GHz sweep frequency signal was injected, and field strength data from 16 probes were collected.

[0061] Step 2: Field Uniformity Analysis: The standard deviation of the calculated field strength is 0.8 dB, while that of the traditional mechanical stirring mode is 1.5 dB. Figure 3 As shown, the gradient loss mode can effectively improve field uniformity and is suitable for scenarios with stringent requirements for field distribution consistency, such as multi-input multi-output antenna efficiency testing.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dynamic electromagnetic reverberation chamber based on plasma control, comprising a reverberation chamber body, a plasma array module, a drive control module, and a feedback monitoring module; characterized in that, The plasma array module is embedded in the six inner walls of the reverberation chamber body, and the drive control module is electrically connected to the plasma array module to dynamically adjust the equivalent quality factor Q value of the reverberation chamber; the feedback monitoring module is located in the reverberation chamber body and is signal-connected to the drive control module. The plasma array module is composed of multiple plasma units arranged in a honeycomb pattern. By adjusting the driving voltage and pulse frequency, the plasma electron density and collision frequency are controlled, thereby changing its equivalent electromagnetic parameters. The drive control module includes a high-voltage pulse generator and a zone control logic unit; it is used to output pulse signals with adjustable parameters and realize independent zone control of the plasma array. The feedback monitoring module includes a broadband electric field probe array and an adaptive control unit, which are used to collect field strength data in the cavity in real time and generate parameter adjustment commands to achieve closed-loop control.

2. The plasma-controlled dynamic electromagnetic reverberation chamber according to claim 1, characterized in that, The plasma unit employs a dielectric barrier discharge structure or a radio frequency driven ionization source. Each unit contains two layers of metal electrodes with an intermediate dielectric layer. The metal electrodes of the plasma unit are 0.1 mm thick, and the intermediate dielectric layer is an Al2O3 ceramic or PVC film with a thickness of 1 mm. The size of the plasma unit is 10 cm × 10 cm, and the spacing between two adjacent plasma units is 1 / 8 to 1 / 4 of the lowest frequency wavelength in the operating band. The plasma array module controls the electron density n by adjusting the driving parameters. e The range is 10 9 -10 12 cm -3 Collision frequency v c The range is 10 8 -10 11 Hz.

3. The plasma-controlled dynamic electromagnetic reverberation chamber according to claim 1, characterized in that, The high-voltage pulse generator of the drive control module adopts a full-bridge inverter topology, with an output drive voltage range of 0-10kV and a pulse frequency range of 1kHz-10MHz; the partition control logic unit divides the plasma array module into multiple independent control areas and supports switching between global mode and gradient mode.

4. The plasma-controlled dynamic electromagnetic reverberation chamber according to claim 1, characterized in that, The broadband electric field probe array of the feedback monitoring module consists of several broadband electric field probes arranged at equal intervals inside the reverberation chamber body, with a frequency range of 100MHz-20GHz. The adaptive algorithm unit fits the field strength data based on the least squares method, generates plasma parameter adjustment commands, and realizes closed-loop control. The response time of the closed-loop control is <10ms.

5. The plasma-controlled dynamic electromagnetic reverberation chamber according to claim 1, characterized in that, The reverberation chamber has three operating modes: Total Internal Reflection High Q Mode: All plasma units are turned off, the reverberation chamber wall is equivalent to an all-metal surface, and the Q value is determined by the inherent losses of the reverberation chamber; Q > 50,000; suitable for high-sensitivity receiver testing and weak electromagnetic signal detection scenarios. Full absorption low-Q mode: Apply a high-frequency pulse of >5MHz and a high-voltage pulse of >8kV to all plasma units, so that ω p Significantly higher than the operating frequency, the Q value drops to the 200-500 range; suitable for pulse testing to quickly clear residual energy from the cavity; Gradient loss mode: Independently control plasma parameters in different wall regions to form a non-uniform field distribution in the reverberation chamber body, optimize the field uniformity in specific regions, and achieve a field strength standard deviation of <1dB.

6. The plasma-controlled dynamic electromagnetic reverberation chamber according to claim 1, characterized in that, The plasma layer formed by the plasma array module has a thickness of 3-5cm and a power consumption of <200W / m² in the activated state.

7. A control method for controlling a plasma-controlled dynamic electromagnetic reverberation chamber as described in any one of claims 1-6, characterized in that, include: System initialization: Complete the connection and calibration of the plasma array, drive control module and feedback monitoring module, and determine the initial operating parameters; Target parameter input: Set the target quality factor, normalized field strength, and energy decay time constant of the electromagnetic reverberation chamber according to the test requirements; Plasma parameter control: The drive control module outputs pulse signals according to the target parameters to adjust the plasma electron density and collision frequency, thereby changing its equivalent dielectric constant and conductivity. Closed-loop optimization: The feedback monitoring module collects field strength data in real time, generates adjustment instructions through an adaptive algorithm, and dynamically corrects the plasma operating parameters until the target value is reached.

8. The method according to claim 7, characterized in that, During the plasma parameter control process, the Q value is dynamically adjusted by switching the plasma operating state: The expression for the plasma equivalent relative permittivity is: ， Where, ω p ω is the plasma frequency, and ω is the angular frequency of the incident electromagnetic wave. The electron collision frequency; The plasma frequency is determined by the following formula: ， In the formula, The amount of electron charge. The vacuum permittivity, For electronic quality, Electron density; Through plasma frequency ω p Different operating states are achieved through the relationship between the incident electromagnetic wave angular frequency ω and the frequency ω: When the plasma frequency ω p When the incident electromagnetic wave has an angular frequency of ω, the plasma exhibits low-loss dielectric characteristics, and the electromagnetic wave is partially reflected. The cavity Q value is determined by the inherent loss, and Q>50,000. When the plasma frequency ω p When the incident electromagnetic wave has an angular frequency of ω, the plasma exhibits the characteristics of a high-loss medium. The electromagnetic wave energy is dissipated into heat energy through collisions, and the Q value decreases significantly, dropping to the range of 200-500. By adjusting the driving voltage and frequency, the Q value can be precisely controlled, thus achieving continuous adjustment. The formula for calculating the effective Q value of the cavity is: ， Among them, U stored The energy stored in the cavity represents the total amount of electromagnetic energy stored within the cavity; P loss_plasma P represents the plasma loss power, reflecting the rate at which the plasma absorbs and consumes electromagnetic energy. loss_cavity This represents the inherent power loss of the cavity, reflecting the unavoidable energy loss of the cavity itself.

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