Fast response amplitude limiting filter integrated HPM protection device based on carbon nanotube field emission

Abstract

This invention belongs to the field of microwave communication and electromagnetic protection technology, specifically providing a fast-response limiting and filtering integrated HPM protection device based on carbon nanotube field emission, to overcome many shortcomings of the existing technology. Based on existing limiting and filtering integrated high-power microwave protection devices, this invention introduces a carbon nanotube field emission limiting structure. Through carbon nanotube field emission, high-density deterministic seed electrons are provided, significantly shortening the gas breakdown avalanche setup time, thereby significantly reducing the total response time. Simultaneously, a metal-dielectric-metal three-layer coaxial DC bias structure is designed to apply a DC bias voltage to the carbon nanotube film to modulate the field emission current density, achieving real-time control of the response speed. Ultimately, the limiting and filtering integrated high-power microwave (HPM) protection device of this invention has a faster response speed, more stable limiting performance, and the response speed can be actively controlled.

Description

Technical Field

[0001] This invention belongs to the field of microwave communication and electromagnetic protection technology, and relates to a high-power microwave (HPM) protection device for the front end of a microwave receiver, and particularly provides a fast-response limiting and filtering integrated HPM protection device based on carbon nanotube (CNT) field emission. Background Technology

[0002] Currently, HPM protection in microwave front-ends mainly adopts a discrete layout of filters and limiters. The filter structure enables frequency selection of the received signal and filters out microwave power outside the frequency domain. The solid-state limiting circuit structure completes the limiting of high-power microwave pulse power within the link's operating bandwidth. Among them, the filter module and the limiting module are arranged in a serial topology and are functionally independent. They cannot complete the compatibility protection function of high-power microwave pulse signals in the time domain and frequency domain in a single device, resulting in problems such as large size and high inter-stage loss.

[0003] To address the shortcomings of traditional discrete solutions, Chinese patent document CN202110285474.5 proposes a time-domain and frequency-domain integrated microwave front-end high-power microwave protection device. This device includes a rectangular waveguide shell, N pairs of inductive diaphragms arranged axially within the shell, and a pair of capacitive diaphragms positioned between adjacent pairs of inductive diaphragms. Among the capacitive diaphragms, the three pairs with the strongest microwave field strength have a pair of conical / frustum electrodes loaded at the center of their opposite surfaces. Its working principle is as follows: in the frequency domain, the loading of capacitive diaphragms achieves a wide stopband characteristic of the protection structure (40dB stopband suppression can cover the 4th harmonic frequency range), and strong reflection of out-of-band signals enables broadband out-of-band power protection for the microwave receiver under HPM electromagnetic environment; in the time domain, the microwave plasma layer generated by the strong field breakdown of the loading conical / frustum electrodes reflects most of the HPM energy, achieving broadband in-band power protection for the microwave receiver.

[0004] However, although the aforementioned high-power microwave protection device for the microwave front-end achieves integrated protection in the time and frequency domains, it has many technical defects in practical applications; 1) The response speed is still insufficient: the device relies on the strong field breakdown of metal conical / frustum electrodes to generate plasma for limiting. The complete process of gas breakdown includes four stages: initial electron generation, electron acceleration, collisional ionization avalanche, and plasma formation. Among them, the initial electron generation depends on random processes such as natural cosmic rays or random field emission, which has a long waiting time and is unstable, resulting in obvious peak leakage in the entire response process; 2) Peak leakage is probabilistic. Fluctuations: Due to the randomness of the initial electron source, the breakdown threshold is affected by factors such as air pressure, tip morphology, and surface condition, resulting in probabilistic fluctuations and unstable peak leakage power, leading to insufficient protection reliability; 3) Unadjustable response speed: The device is an all-metal passive structure, and once fabricated, its response characteristics are fixed, making it impossible to actively adjust according to the actual HPM threat level or application scenario; 4) Limited relationship between response time and input power: Although the response time shortens with increasing input power, it is still relatively long under low input power conditions, failing to effectively protect against narrow-pulse HPM signals with steep leading edges. To address these issues, this invention proposes a metal tip discharge limiting device incorporating a carbon nanotube field emission mechanism, combined with DC bias modulation technology, to achieve integrated fast-response limiting and filtering protection with significantly improved response speed. Summary of the Invention

[0005] The purpose of this invention is to provide a fast-response, amplitude-limiting, and filtering integrated high-power microwave protection device based on carbon nanotube field emission, overcoming many shortcomings of the existing technology. Based on existing amplitude-limiting and filtering integrated high-power microwave protection devices, this invention introduces a carbon nanotube field emission limiting structure. Through carbon nanotube field emission, high-density deterministic seed electrons are provided, significantly shortening the gas breakdown avalanche setup time, thereby significantly reducing the total response time. Simultaneously, a metal-dielectric-metal three-layer coaxial DC bias structure is designed to apply a DC bias voltage to the carbon nanotube film to modulate the field emission current density, achieving real-time control of the response speed. Ultimately, the amplitude-limiting and filtering integrated high-power microwave (HPM) protection device of this invention has a faster response speed, more stable amplitude-limiting performance, and the response speed can be actively controlled.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A fast-response limiting and filtering integrated HPM protection device based on carbon nanotube field emission, characterized in that it comprises:

[0008] The main body of the waveguide filter includes: a rectangular waveguide shell and N pairs of inductive diaphragms arranged along the axial direction inside it, and capacitive diaphragms arranged between two adjacent pairs of inductive diaphragms;

[0009] A carbon nanotube field emission limiting structure is disposed at the center of the opposite surface of at least one pair of capacitive films with the strongest microwave field strength, comprising: a conductive substrate and a carbon nanotube film coated on the tip surface of the conductive substrate, wherein the carbon nanotube film provides initial seed electrons through field emission mechanism under the action of a strong microwave electric field;

[0010] A coaxial DC bias structure, corresponding to a carbon nanotube field emission limiting structure, includes: a central conductor, a dielectric layer sleeved outside the central conductor, and a metal sleeve sleeved outside the dielectric layer. The central conductor is connected to the conductive substrate of the carbon nanotube field emission limiting structure and applies a DC bias voltage to the carbon nanotube film to modulate the field emission current density.

[0011] Furthermore, in the main body of the waveguide filter, N pairs of inductive diaphragms divide the rectangular waveguide shell into N-1 resonant cavities; the pair of inductive diaphragms are two inductive diaphragms of the same size symmetrically arranged on the two narrow sides of the rectangular waveguide shell, and the pair of capacitive diaphragms are two capacitive diaphragms of the same size symmetrically arranged on the two wide sides of the rectangular waveguide shell.

[0012] Furthermore, in the main body of the waveguide filter, if a carbon nanotube field emission limiting structure is not provided at the center position of the opposite face of the three pairs of capacitive films located at the strongest microwave field strength, a conical electrode is loaded accordingly.

[0013] Furthermore, in the coaxial DC bias structure, the metal sleeve is connected to the positive terminal of the DC bias power supply, the center conductor is connected to the negative terminal of the DC bias power supply, and the DC bias power supply is introduced into the device through a low-pass filter.

[0014] Furthermore, the end face of the coaxial DC bias structure is flush with the capacitive diaphragm.

[0015] Furthermore, the thickness of the carbon nanotube film is 0.1 μm to 10 μm.

[0016] Furthermore, the dielectric layer is a polytetrafluoroethylene sleeve with a thickness of 0.1 mm to 1 mm.

[0017] Furthermore, the DC bias voltage can be adjusted within a range of 0 to 500V.

[0018] Furthermore, the device maintains a low-pressure environment inside, with a pressure range of 10 Pa to 1000 Pa.

[0019] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0020] This invention provides a high-power microwave protection device integrating fast response limiting and filtering based on carbon nanotube field emission, which has the following advantages:

[0021] 1) Significantly improved response speed: High-density deterministic seed electrons are provided by field emission of carbon nanotubes, which significantly shortens the gas breakdown avalanche setup time. The response time gradually shortens with increasing input power, and is approximately inversely proportional to the input power. It is significantly better than the metal tip structure of the prior art at the same input power.

[0022] 2) More stable peak leakage: The deterministic quantum tunneling mechanism of carbon nanotube field emission replaces the random natural electron generation process, making the breakdown threshold more stable, significantly reducing the fluctuation of peak leakage power, and improving protection reliability;

[0023] 3) Actively adjustable response speed: The response speed can be adjusted in real time by actively modulating the field emission current density through DC bias voltage; under low input power conditions, the response speed can be compensated by increasing the bias voltage; the protection strategy can be flexibly adjusted under different threat levels.

[0024] 4) Maintaining wide stopband filtering performance: After the introduction of carbon nanotubes, the electric field distribution is close to that of the original structure. The dielectric layer of the metal-dielectric-metal coaxial structure has minimal impact on microwave transmission. The wide stopband characteristics and passband insertion loss (less than 1 dB) of the device remain within acceptable range.

[0025] 5) High process feasibility: Commercially available single-walled carbon nanotube aqueous dispersion and standardized SMA strippable coaxial cable are used as carriers, avoiding the complex in-situ growth process of carbon nanotubes, reducing the preparation difficulty and cost, and facilitating engineering implementation;

[0026] 6) Modular upgrade feature: Based on the existing technology (CN202110285474.5), the metal conical / frustum electrode can be directly replaced with a carbon nanotube field emission structure without changing the main design of the waveguide filter, which has good technical inheritance and upgrade compatibility. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the high-power microwave protection device based on carbon nanotube field emission, which features fast response limiting and filtering. In this invention, 1 is a rectangular waveguide shell, 2 is an inductive diaphragm, 3 is a capacitive diaphragm, 4 is a conical electrode, 5 is a metal-dielectric-metal three-layer coaxial DC bias structure, 6 is an SMA connector, and 7 is a carbon nanotube field emission limiting structure.

[0028] Figure 2 This is a partially enlarged view of the high-power microwave protection device based on carbon nanotube field emission, which features fast response limiting and filtering.

[0029] Figure 3 This is a schematic diagram of the three-layer coaxial DC bias structure of metal-dielectric-metal in this invention.

[0030] Figure 4 This is an electric field distribution diagram of the high-power microwave protection device with fast response limiting and filtering based on carbon nanotube field emission in this invention.

[0031] Figure 5 The figure shows the S-parameter simulation results of the high-power microwave protection device with fast response limiting and filtering based on carbon nanotube field emission in this invention.

[0032] Figure 6 This is a response time diagram from particle simulation of the high-power microwave protection device based on carbon nanotube field emission, which features fast response amplitude limiting and filtering.

[0033] Figure 7 This is a peak leakage power diagram from particle simulation of the high-power microwave protection device based on carbon nanotube field emission, which features fast response limiting and filtering.

[0034] Figure 8 The diagram shows the input and output waveforms of the high-power microwave protection device based on carbon nanotube field emission with fast response limiting and filtering in this invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0036] This embodiment provides a high-power microwave protection device based on carbon nanotube field emission, featuring fast response, amplitude limiting, and filtering. Building upon existing amplitude limiting and filtering devices, it retains the main structure of a wide-stopband filter consisting of a rectangular waveguide shell, an inductive diaphragm, and a capacitive diaphragm. The key upgrade is to replace the core amplitude limiting structure: the metal conical / frustum electrodes of the prior art are replaced with a carbon nanotube field emission structure. A metal-dielectric-metal three-layer coaxial DC bias structure is introduced into this structure. By actively modulating the field emission current density with an applied DC voltage, the gas breakdown avalanche setup time is significantly shortened, achieving fast response, low fluctuation, and adjustable amplitude limiting protection.

[0037] like Figure 1 and Figure 2 As shown, the fast-response limiting and filtering integrated microwave protection device based on carbon nanotube field emission includes:

[0038] The waveguide filter body includes a rectangular waveguide shell 1 and N pairs of inductive diaphragms 2 arranged axially inside it, with a pair of capacitive diaphragms 3 arranged between adjacent pairs of inductive diaphragms. The N pairs of inductive diaphragms divide the rectangular waveguide shell into N-1 resonant cavities. Each pair of inductive diaphragms consists of two identical inductive diaphragms symmetrically arranged on the two narrow sides of the rectangular waveguide shell, and each pair of capacitive diaphragms consists of two identical capacitive diaphragms symmetrically arranged on the two wide sides of the rectangular waveguide shell. For the three pairs of capacitive diaphragms with the strongest microwave field strength, a pair of conical electrodes 4 are loaded at the center of their opposite faces. Among the three pairs of capacitive diaphragms, at least one conical electrode loaded on at least one pair of capacitive diaphragms with the strongest microwave field strength is replaced with a carbon nanotube field emission limiting structure.

[0039] The carbon nanotube field emission limiting structure 7 is disposed at the center of the opposite surface of at least one pair of capacitive films with the strongest microwave field strength in the capacitive film, and includes: a conductive substrate and a carbon nanotube film coated on the tip surface of the conductive substrate. The carbon nanotube film is used to provide high-density initial seed electrons through field emission mechanism under the action of strong microwave electric field, so as to shorten the gas breakdown avalanche establishment time.

[0040] The metal-dielectric-metal three-layer coaxial DC bias structure 5, embedded in the waveguide filter body at the carbon nanotube field emission limiting structure, includes: a central conductor, a dielectric layer sleeved outside the central conductor, and a metal sleeve sleeved outside the dielectric layer. The central conductor is connected to a needle-shaped conductive substrate and applies a DC bias voltage to the carbon nanotube film to modulate the field emission current density, thereby achieving active control of the response speed. The metal-dielectric-metal three-layer coaxial DC bias structure 5 is connected to a DC bias power supply through an SMA connector 6.

[0041] In this embodiment, the waveguide filter body adopts the same rectangular waveguide shell structure as the prior art, with N pairs of inductive diaphragms (N ranging from 5 to 12) arranged axially inside, and a pair of capacitive diaphragms arranged between adjacent pairs of inductive diaphragms; the N pairs of inductive diaphragms divide the rectangular waveguide shell into N-1 resonant cavities of different lengths; each pair of inductive diaphragms consists of two identical inductive diaphragms symmetrically arranged on the two narrow sides of the rectangular waveguide shell, and each pair of capacitive diaphragms consists of two identical capacitive diaphragms symmetrically arranged on the two wide sides of the rectangular waveguide shell; for The three pairs of capacitive diaphragms with the strongest microwave field strength each have a pair of conical electrodes loaded at the center of their opposite surfaces. At least one conical electrode loaded on at least one pair of capacitive diaphragms with the strongest microwave field strength is replaced with a carbon nanotube field emission limiting structure. The waveguide filter body achieves wide stopband characteristics of the protection structure in the frequency domain by loading capacitive diaphragms. The 40dB stopband suppression can cover the 4th harmonic frequency range. The strong reflection of out-of-band signals enables the broadband out-of-band power protection function of the microwave receiver in HPM electromagnetic environment.

[0042] The carbon nanotube field emission limiting structure and the metal-dielectric-metal three-layer coaxial DC bias structure are fabricated simultaneously using a single-ended SMA strippable coaxial cable. One end of the SMA coaxial cable has its outer shielding layer removed to expose the central conductor, which serves as the conductive substrate for the carbon nanotube field emission limiting structure. A commercially available single-walled carbon nanotube (SWCNT) aqueous dispersion is applied to the tip of the conductive substrate by drop coating or dip coating to form a carbon nanotube film. After drying at room temperature or at low temperature (<100°C), a stable field emitter is formed. Due to its high aspect ratio structure (typical aspect ratio >1000), the carbon nanotube has an extremely high electric field enhancement factor (β>1000), which is much higher than that of traditional metal tips (β about 10~50). Under the same applied electric field, it can generate several orders of magnitude higher field emission current densities. The dielectric layer of the SMA coaxial cable is made of polytetrafluoroethylene (PTFE) with a thickness of 0.325 mm, which is used to achieve electrical isolation between microwave signals and DC voltage, while allowing normal transmission of microwave signals. The outer metal sheath of the SMA coaxial cable is connected to the positive terminal of the DC bias power supply through a wire, and the center conductor is connected to the negative terminal of the DC bias power supply through a wire. The DC bias power supply is introduced into the device through a low-pass filter, and the low-pass filter can prevent high-power microwave signals from damaging the DC power supply.

[0043] In terms of working principle:

[0044] 1. Physical mechanism of field emission from carbon nanotubes;

[0045] Field emission is the process by which electrons, under the influence of a strong electric field, tunnel through a surface barrier into a vacuum / gas through the quantum tunneling effect. The Fowler-Nordheim (FN) formula describes the relationship between the field emission current density and the electric field:

[0046] ,

[0047] Where J is the emission current density, E is the applied electric field strength, and β is the electric field enhancement factor. Let A and B be the material work function, where A and B are constants.

[0048] Due to its high aspect ratio structure, carbon nanotubes have an extremely small radius of curvature at their tips (about 10 nm), which allows them to obtain an extremely high electric field enhancement factor (β>1000), far exceeding that of traditional metal tips (β about 10~50). Therefore, under the same applied electric field, carbon nanotubes can generate emission current densities several orders of magnitude higher, forming a high-density, deterministic initial seed electron flow.

[0049] 2. Fast response mechanism;

[0050] The complete process of gas breakdown consists of four stages:

[0051] The first stage: initial electron generation. Traditional devices rely on natural cosmic rays or random field emission to provide initial seed electrons. This process is random and has a long waiting time.

[0052] Second stage: Electron acceleration, seed electrons are accelerated in an electric field to gain energy;

[0053] The third stage: collisional ionization, where high-energy electrons collide with gas molecules to produce secondary electrons (avalanche process).

[0054] Fourth stage: Plasma formation, electron density reaches a critical value, forming a self-sustaining discharge plasma;

[0055] This invention utilizes carbon nanotube field emission to actively and densely inject initial seed electrons, transforming the first stage from a random waiting process into an active and controllable electron injection process. This skips or significantly shortens the waiting time of the first stage and directly initiates the avalanche process. Since the emission current density of carbon nanotubes is several orders of magnitude higher than that of the natural process, the initiation time of the second to fourth stages is also significantly advanced, thereby significantly shortening the total response time.

[0056] 3. DC bias modulation mechanism;

[0057] An external DC bias voltage is applied to the tip of the carbon nanotube through a metal-dielectric-metal coaxial structure, and superimposed with the microwave electric field, as shown in the following:

[0058] ,

[0059] Among them, E RF For microwave electric fields, E DC The DC electric field ensures that the carbon nanotube tip is in a pre-enhanced field state before the microwave signal arrives. When the HPM pulse arrives, the total electric field far exceeds the field emission threshold, instantly generating an extremely high-density electron flow, further shortening the response time. By adjusting the DC bias voltage amplitude, the field emission current density can be actively controlled, thereby achieving active regulation of the response speed. Simulations show that, in the overall trend, for the same input power, the ordinary conical electrode loaded structure has the longest response time and the largest peak leakage power. The field emission structure with carbon nanotubes without voltage has a relatively shorter response time and a relatively smaller peak leakage power. The field emission structure with carbon nanotubes with 50V voltage has the shortest response time and the smallest peak leakage power.

[0060] 4. Structural compatibility design;

[0061] After introducing a metal-dielectric-metal three-layer coaxial DC bias structure and a carbon nanotube field emission limiting structure, the maximum electric field at 9.9 GHz of the device is 187425 V / m, which is close to the electric field strength of 190571 V / m of the original structure. This verifies that the present invention achieves fast response design while maintaining the original electric field enhancement effect, and does not significantly change the microwave transmission characteristics of the device, ensuring that the original wide stopband filtering performance of the device is maintained.

[0062] Based on the above working principle, the beneficial effects of the present invention will be explained in detail below with reference to specific simulation tests.

[0063] In this embodiment, the waveguide filter body adopts the same waveguide filter body structure as the prior art (CN202110285474.5); wherein, the rectangular waveguide shell adopts the standard rectangular waveguide BJ100 (wide side length a=22.86mm, narrow side height b=10.16mm), and the material is aluminum LY12; inside the rectangular waveguide shell, six pairs of aluminum inductive diaphragms with a thickness of 0.65mm are arranged along the axial direction of the narrow side, and the spacing between two adjacent pairs of inductive diaphragms are L1=L5=6.34mm, L2=L4=6.86mm, L3=8.25mm, and the opening size is respectively. d1=d6=13.51mm, d2=d5=6.33mm, d3=d4=5.47mm; the six pairs of inductive diaphragms divide the rectangular waveguide housing into five resonant cavities; each resonant cavity has a pair of aluminum capacitive diaphragms at its center, and the opening heights h1~h5 of the five pairs of capacitive diaphragms are 2.16mm, 1.52mm, 2.08mm, 1.52mm, and 2.16mm from left to right; the diaphragm thicknesses are t1=t5=2.18mm, t2=t4=2.41mm, and t3=3.1mm, respectively; the passband center frequency is 9.9GHz, and the bandwidth is 400MHz.

[0064] In this embodiment, the carbon nanotube field emission limiting structure uses a single-ended SMA strippable coaxial cable (characteristic impedance 50Ω) as the carbon nanotube carrier and tip substrate; the outer shielding layer and dielectric layer of the cable are stripped to expose the central conductor, retaining a length of approximately 0.84 mm; a commercially available single-walled carbon nanotube (SWCNT) aqueous dispersion (carbon nanotube diameter 1~2 nm, length 5~30 μm) is used; the carbon nanotube dispersion is drop-coated onto the polished tip using a micropipette, or the tip is dip-coated to adsorb the carbon nanotubes; it is then naturally dried at room temperature for 24 hours, or placed in a 60~80°C oven for low-temperature drying for 2~4 hours to form a stable carbon nanotube film; the thickness of the carbon nanotube film is controlled at 0.1~10 μm to ensure that the tip curvature radius remains in the nanometer range to maintain a high electric field enhancement factor.

[0065] In this embodiment, the metal-dielectric-metal three-layer coaxial bias structure is as follows: Figure 3As shown: The inner layer is the center conductor of the SMA coaxial cable (coated with carbon nanotubes), serving as the field emission electron lead-out terminal, with an outer diameter Φ1 of 0.29 mm; the middle layer uses a polytetrafluoroethylene (PTFE) dielectric sheath, with an inner diameter matching the outer diameter of the SMA cable dielectric layer, an outer diameter Φ2 of 0.94 mm, and a wall thickness of 0.325 mm, fitted outside the center conductor; the outer layer uses a copper or aluminum metal sheath, with an outer diameter Φ3 of 1.19 mm, an inner diameter matching the outer diameter of the PTFE sheath, and a wall thickness of 0.125 mm, fitted outside the PTFE sheath; in addition, the coaxiality between the center conductor and the outer metal sheath is ensured to avoid microwave transmission mode distortion; the outer metal sheath is connected to the positive terminal of the DC bias power supply via a wire, and the inner center conductor is connected to the negative terminal of the DC bias power supply via a wire.

[0066] Based on the above-mentioned waveguide filter body, carbon nanotube field emission limiting structure and metal-dielectric-metal three-layer coaxial bias structure, the prepared carbon nanotube field emission structure is installed at the center of the capacitive diaphragm in the middle of the waveguide, replacing one of the metal conical electrodes in the existing structure; the tip of the carbon nanotube faces the center of the waveguide and is located in the region of strongest electric field; the DC bias power supply lead is introduced through a low-pass filter to prevent microwave leakage; the upper and lower parts of the waveguide are fastened with screws to ensure good electrical contact.

[0067] The assembled high-power microwave protection device based on carbon nanotube field emission with fast response limiting and filtering is connected to an auxiliary vacuum system (mechanical pump) to evacuate to the target pressure range (10~1000 Pa, optimized according to the working frequency band, the typical value of X band is about 100 Pa). The pressure is monitored in real time by a vacuum gauge to maintain stability.

[0068] Simultaneously, electromagnetic simulation software (such as HFSS and CST) was used for verification: a three-dimensional electromagnetic model of the device of the present invention was established, and the electric field distribution at 9.9 GHz was simulated. The results are as follows: Figure 4 As shown, the upper figure is the electric field distribution of the prior art (CN202110285474.5), and the lower figure is the electric field distribution of this embodiment. The maximum electric field intensity is recorded. As can be seen from the figure, the maximum electric field intensity of the present invention is 187425 V / m, which is close to the original structure of 190571 V / m. This indicates that the design structure of the present invention does not affect the local electric field enhancement effect of the conical electrode.

[0069] Furthermore, the passband characteristics and wide stopband suppression characteristics were verified through S-parameter simulation, and the results are as follows: Figure 5 As shown in the figure, the S-parameters have a passband center frequency of 9.9 GHz, a bandwidth of 400 MHz, and a stopband suppression of >40 dB from 10.7 to 20.7 GHz, exhibiting good wide stopband characteristics. Furthermore, the S-parameters of the device, measured using a vector network analyzer, show good agreement with the simulation results.

[0070] The PIC-MCC (Particle Cloud Mesh-Monte Carlo Collision) method was used to simulate gas breakdown particles. Two-dimensional / three-dimensional simulation models were established, and the gas composition (e.g., air, nitrogen, argon, typically air) and excitation conditions (X-band HPM pulse, power level kW~MW, pulse width 10~50ns) were set. The field emission region of carbon nanotubes was defined, and the FN formula parameters were input: carbon nanotube work function approximately 4.5~5.0 eV, electric field enhancement factor β>1000. Simulation results for three structures were compared: a standard conical electrode structure, a CNT unbiased structure, and a CNT+50V biased structure. Response time and peak leakage power were recorded and compared. Specifically, for example... Figure 6 The response time is shown below. Figure 7 The figure shows the peak leakage power. As can be seen from the figure, the response time gradually decreases with the increase of input power, and is approximately inversely proportional to the input power. Under the same input power, the CNT+50V bias structure has the shortest response time. The peak leakage power gradually increases with the increase of input power. Under the same power, the CNT+50V bias structure has the smallest peak leakage power, which shows that the structure designed in this invention has the advantages of shortening the response time and reducing the peak leakage power.

[0071] An X-band HPM injection test platform was constructed, comprising: an HPM source (outputting high-power X-band microwave pulses, power level: kW, pulse width: 10~1000ns adjustable); an auxiliary vacuum system (maintaining a low-pressure environment inside the device); a DC bias power supply (0~500V adjustable); a test system (oscilloscope recording output waveforms and monitoring incident / reflected power); and a test condition matrix (different input powers (50~80 dBm), different pressures (10~1000 Pa), different pulse widths (10~1000ns), and different bias voltages (0V~500V). Figure 8 The figure shows the input and output waveforms under 62dBm input power, 200pa air pressure, 500ns pulse width, and 50V bias voltage. As can be seen from the figure, the HPM protection device designed in this invention produces a significant limiting effect, and the response time and peak leakage are significantly better than conventional plasma limiting devices.

[0072] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A fast response amplitude limiting filter integrated HPM protection device based on carbon nanotube field emission, characterized in that, include: The main body of the waveguide filter includes: a rectangular waveguide shell and N pairs of inductive diaphragms arranged along the axial direction inside it, and capacitive diaphragms arranged between two adjacent pairs of inductive diaphragms; A carbon nanotube field emission limiting structure is disposed at the center of the opposite surface of at least one pair of capacitive films with the strongest microwave field strength, comprising: a conductive substrate and a carbon nanotube film coated on the tip surface of the conductive substrate, wherein the carbon nanotube film provides initial seed electrons through field emission mechanism under the action of a strong microwave electric field; A coaxial DC bias structure, corresponding to a carbon nanotube field emission limiting structure, includes: a central conductor, a dielectric layer sleeved outside the central conductor, and a metal sleeve sleeved outside the dielectric layer. The central conductor is connected to the conductive substrate of the carbon nanotube field emission limiting structure and applies a DC bias voltage to the carbon nanotube film to modulate the field emission current density.

2. The fast-response integrated amplitude limiting filter HPM protection device based on carbon nanotube field emission according to claim 1, wherein, In the main body of the waveguide filter, N pairs of inductive diaphragms divide the rectangular waveguide shell into N-1 resonant cavities; the pair of inductive diaphragms are two inductive diaphragms of the same size symmetrically arranged on the two narrow sides of the rectangular waveguide shell, and the pair of capacitive diaphragms are two capacitive diaphragms of the same size symmetrically arranged on the two wide sides of the rectangular waveguide shell.

3. The fast-response integrated amplitude limiting filter HPM protection device based on carbon nanotube field emission according to claim 1, characterized in that, In the main body of the waveguide filter, if a carbon nanotube field emission limiting structure is not set at the center position of the opposite face of the three pairs of capacitive films located at the strongest microwave field strength, a conical electrode is loaded accordingly.

4. The fast-response integrated amplitude limiting filter HPM protection device based on carbon nanotube field emission according to claim 1, characterized in that, In the coaxial DC bias structure, the metal sleeve is connected to the positive terminal of the DC bias power supply, the center conductor is connected to the negative terminal of the DC bias power supply, and the DC bias power supply is introduced into the device through a low-pass filter.

5. The HPM protection device based on carbon nanotube field emission with fast response limiting and filtering as described in claim 1, characterized in that, The end face of the coaxial DC bias structure is flush with the capacitive diaphragm.

6. The HPM protection device based on carbon nanotube field emission with fast response limiting and filtering as described in claim 1, characterized in that, The thickness of the carbon nanotube film is 0.1 μm to 10 μm.

7. The HPM protection device based on carbon nanotube field emission with fast response limiting and filtering as described in claim 1, characterized in that, The dielectric layer is a polytetrafluoroethylene sleeve with a thickness of 0.1 mm to 1 mm.

8. The integrated HPM protection device based on carbon nanotube field emission with fast response limiting and filtering according to claim 1, characterized in that, The DC bias voltage can be adjusted from 0 to 500V.

9. The HPM protection device based on carbon nanotube field emission with fast response limiting and filtering as described in claim 1, characterized in that, The device maintains a low-pressure environment inside, with a pressure range of 10 Pa to 1000 Pa.

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