High-efficiency transmission method of high-power microwaves and biconical horn transmission antenna thereof

Abstract

The invention discloses a high-efficiency transmission method for high-power microwaves and a biconical horn transmission antenna thereof, and the method comprises the steps: accessing the high-power microwaves through employing a transition circular waveguide, enabling the high-power microwaves to be preliminarily matched with the impedance characteristics of a transmission airspace through a small-angle beam-expanding transmission space, and reducing the near-field reflection; and the mode field impedance is further gradually changed to the free space impedance through the large-angle beam expanding transmission space, so that the guided wave is converted into the radiation wave, and finally the radiation wave is radiated in the free space through the low-loss sealing layer. The large conical horn mouth surface is sealed by the high molecular weight polyethylene antenna housing, so that an airtight environment in which inert gas is filled or vacuumized can be realized, the risk of air breakdown is effectively avoided, and the high power endurance capability of the antenna is greatly improved. The horn taper angle and transition structure design is matched with the low-loss high-molecular antenna housing, so that efficient transmission and radiation of broadband electromagnetic waves are realized. And the large conical horns and the large conical horns adopt a segmented processing mode, so that the processing difficulty is reduced.

Description

Technical Field

[0001] This invention relates to an efficient transmission method for high-power microwaves and its dual-cone horn transmission antenna. Background Technology

[0002] In practical applications of microwave technology, circular waveguide TE11 mode high-power microwaves, due to their highly concentrated energy vertical beam characteristics, exhibit advantages such as high radiation efficiency and long transmission distance. Furthermore, they can be directly and efficiently radiated through conventional horn antennas, thus finding widespread application in numerous microwave transmission and radiation systems. However, in the high-power microwave field, core microwave sources such as relativistic antiwave tubes and virtual cathode oscillators output electromagnetic wave modes that differ significantly from those in conventional applications. These modes are mostly low-order, angularly uniformly distributed, typically represented by circular waveguide TM01 mode, TE01 mode, and coaxial TEM mode. In GW-level high-power microwave testing, mode matching and efficient transmission are key technical challenges. Because existing mainstream radiating antennas (such as horn antennas based on the TE11 mode) are incompatible with the output modes of high-power microwave sources, mode converters are required to achieve conversion between different electromagnetic wave modes. This increases the complexity of the testing system, generates power loss, and may introduce risks such as signal reflection and radio frequency breakdown, affecting the stability and accuracy of the test, and in severe cases, even damaging the test equipment or the microwave source itself. Summary of the Invention

[0003] The purpose of this invention is to address the problems of incompatible output modes in existing radiating antennas, which may even introduce risks such as signal reflection and radio frequency breakdown, affecting the stability and accuracy of testing. This invention provides a radiating antenna that can directly adapt to the output of the TM01 high-power microwave source, and has the advantages of lightweight design, high power capacity and broadband characteristics. This is a key requirement for breaking through the current bottleneck of high-power microwave testing technology.

[0004] The technical solution of the present invention: A high-efficiency transmission method for high-power microwaves and its dual-conical horn transmission antenna, comprising the following steps: Step 1: Use a transition circular waveguide to connect to high-power microwaves. Step 2: By expanding the beam at a small angle, the high-power microwave is initially matched to the impedance characteristics of the transmission space, thereby reducing near-field reflections; Step 3: By expanding the beam at a large angle and transmitting it into space, the mode field impedance is gradually changed to the free space impedance, thus transforming the guided wave into a radiated wave. Step 4: Allow the radiation wave to radiate into free space through a low-loss sealing layer.

[0005] The transition circular waveguide has an inner diameter of 0.64λ and a length of 0.48λ, with a smooth metal inner wall. High-power microwaves are transmitted linearly along the axis of the transition circular waveguide.

[0006] The small-angle beam-expanding transmission space has a small radius of 0.64λ, a large radius of 1.44λ, and a length of 3.456λ, and the cone angle satisfies the impedance gradient rate ≤ 5% / λ.

[0007] The large-angle beam-expanding transmission space has a small radius of 1.424λ, a large radius of 5.52λ, and a length of 5.728λ. It is divided into three nonlinear gradient sections according to the target broadband. The low-frequency band is transmitted with a slow gradient rate of 3% / λ, the center frequency band is transmitted with a uniform gradient rate of 5% / λ, and the high-frequency band is transmitted with a fast gradient rate of 7% / λ. A fine-tuning section of 0.1λ is provided at the end of the high-frequency band.

[0008] The inner wall of the transition section is a smooth curved surface, with the radius smoothly transitioning from a small cone with a large radius of 1.44λ to a large cone with a small radius of 1.424λ. The inner wall is coated with a 0.01λ thick dielectric film with a dielectric constant of 2.2, and the reflection coefficient is optimized to below -25dB.

[0009] The high-power microwave propagates along a hyperboloid trajectory within a large-angle beam-expanding transmission space, with an inner wall conductivity ≥ 5.8 × 10⁻⁶. 7 The surface roughness is ≤0.1μm and the surface area is S / m.

[0010] The hyperboloid trajectory equation x² / a²-y² / b²=1 has its focus coinciding with the center of the output end of the small cone.

[0011] The output end of the large-angle beam-expanding transmission space is sealed by a low-loss polymer antenna radome, and the transmission space is filled with inert gas.

[0012] It includes a transition circular waveguide, a small conical horn, and a large conical horn. One end of the transition circular waveguide is equipped with a waveguide flange, and the other end is fixedly connected to the small diameter end of the small conical horn. The large diameter end of the small conical horn is connected to the small diameter end of the large conical horn through the waveguide flange, and the large diameter end of the large conical horn is sealed by an antenna radome.

[0013] The connection between the small conical horn and the transition circular waveguide is chamfered, and the waveguide flange end face that docks with the large conical horn is provided with a sealing groove and a sealing ring is installed.

[0014] The beneficial effects of this invention are as follows: The large conical horn aperture is sealed with a high-molecular-weight polyethylene radome, enabling an airtight environment by filling it with inert gas or evacuating it, effectively avoiding the risk of air breakdown and significantly improving the antenna's high-power withstand capability. The horn cone angle and transition structure design, combined with the low-loss polymer radome, achieves efficient transmission and radiation of broadband electromagnetic waves. The large conical horn and the large conical horn are manufactured in segments, reducing manufacturing difficulty. Attached Figure Description

[0015] Figure 1This is a schematic diagram of a horn antenna.

[0016] Figure 2 This is a schematic diagram of the impedance bandwidth of the double conical horn of the present invention.

[0017] Figure 3 This is a schematic diagram of the gain direction of a double conical horn.

[0018] Reference numerals: 1-waveguide flange, 2-transition circular waveguide, 3-small conical horn, 4-large conical horn, 5-radome. Detailed Implementation

[0019] Example 1 This embodiment is used for a GW-level high-power microwave test system in the C-band 4-5.4GHz, which is compatible with the TM01 mode output of microwave sources such as relativistic anti-wave tubes and virtual cathode oscillators, and needs to meet the requirements of wideband high-efficiency transmission and lightweight integration. Based on a center frequency of 4.7 GHz, the center wavelength is calculated to be approximately 63.83 mm (speed of light c = 3 × 10⁻⁶). 8 m / s, λ0=c / f0, the parameters of each key component are designed according to λ0 (λ0 is the center wavelength of the target operating frequency band):

[0020] Mode purification and stable transmission: The transition circular waveguide is bolted to the output end of the high-power microwave source through a flange with through holes to ensure that there is no gap at the interface; after the high-power microwave is fed in, it is transmitted along the axis of the smooth metal wall. The chamfered structure avoids electric field concentration. The mode purity is tested to be ≥99.5%. Preliminary impedance matching and smooth beam expansion: When the electromagnetic wave enters the small conical horn, it is smoothly expanded at an impedance gradient of ≤5% / λ. The field distribution transitions from a guiding wave type to a conical wave type, and the near-field reflection coefficient is ≤-20dB. Optimized depth impedance gradient and wide-angle beam expander: Arc-shaped transition: The electromagnetic wave smoothly transitions from a 19.15mm long arc-shaped transition section with a radius of 92.01mm to 90.90mm. The inner wall dielectric film compensates for impedance deviation, and the reflection coefficient is optimized to -28dB. Dynamic impedance gradient transmission: Low frequency band (4-4.5GHz) gradually changes by 3% / λ, center frequency band (4.5-4.9GHz) gradually changes by 5% / λ evenly, high frequency band (4.9-5.4GHz) gradually changes by 7% / λ quickly, and an 8mm fine-tuning segment at the end compensates for impedance offset.

[0021] Hyperboloid beam expansion trajectory adaptation: The inner wall of the large cone is machined into a hyperboloid of revolution (equation x² / 127.66²-y² / 159.58²=1), and a copper plating is used (conductivity 5.8×10). 7S / m, surface roughness 0.08μm, wall loss 0.09dB. Low-loss, airtight radiation: The radome and the large conical flange are airtightly connected via a sealing ring, with a sealing performance test result of 8×10. -5 Pa・m³ / s, low-loss electromagnetic wave transmission. High-efficiency free-space radiation: The final radiated wave is a highly directional spherical wave with a wideband average standing wave ratio of 1.15, an impedance matching bandwidth of 48%, a radiation gain of 10.5dB, and a field strength of 620V / m, meeting the requirements for 5GW-level power output. Through simulation and physical testing, this embodiment shows that the energy loss is 2.3% across the entire C-band frequency band, high power tolerance is stable, there is no ionization breakdown, the radiation main lobe energy is concentrated, and the sidelobe suppression ratio is ≥30dB, which is fully suitable for the requirements of high power microwave testing scenarios. Example 2 This embodiment is used for mobile portable high-power microwave testing equipment. While ensuring core performance, it is necessary to reduce the overall weight, enhance structural integration, and adapt to narrow installation spaces. Material optimization: The transition circular waveguide, small conical horn, and large conical horn use aluminum alloy substrate (density 2.7g / cm³), with silver plating on the inner wall (thickness 0.05mm), replacing the traditional copper substrate and reducing weight by 35%. Structural integration: The small conical horn and the arc transition section are machined as a single unit, reducing the number of flange connections, increasing structural compactness by 40%, and reducing installation space requirements by 25%. Parameter adaptation: Keeping the core proportion parameters unchanged, the size is adjusted based on the need for lightweight design: center frequency 4.6GHz, λ0≈65.22mm, and the length of the large conical horn is shortened to 350mm. The small conical horn and the arc-shaped transition section are machined in one piece with a machining accuracy controlled within ±0.008λ to avoid dimensional deviations caused by the integrated structure. The aluminum alloy substrate is pretreated before silver plating to ensure that the coating adhesion is ≥5N / mm², reduce skin effect loss, and control the wall loss to within 0.1dB. The radome is made of ultra-thin high molecular weight polyethylene (6mm thick), combined with a lightweight flange structure, reducing the overall weight by 32% compared to Example 1. This embodiment has an overall weight of ≤15kg, a compact structure, a wideband VSWR of 1.18, an impedance matching bandwidth of 46%, a radiation gain of 10.2dB, and an energy loss of 2.7%, meeting the lightweight and integrated requirements of mobile portable devices while maintaining high power tolerance and efficient transmission performance. Example 3 This embodiment is used in ultra-high power (10GW level microwave radiation scenarios) scenarios, which need to minimize the risk of air breakdown, enhance high power tolerance stability, and adapt to extreme field strength environments. Vacuum environment upgrade: The large conical horn is evacuated to a vacuum level of 1×10. -4 Pa, the number of residual gas molecules ≤3×10¹² / m³, completely eliminating the risk of ionization breakdown. Enhanced Sealing Structure: The connection points of the transition circular waveguide, small conical horn, large conical horn, and radome employ a double sealing ring design, achieving a sealing performance of 5×10⁻⁶. -5 Pa・m³ / s, vacuum holding time ≥72 hours. Structural strength optimization: The wall thickness of the large conical horn is increased to 8mm, and the flange adopts a reinforcing rib design to withstand the pressure difference under vacuum conditions without structural deformation. Vacuum pretreatment: All metal parts are degreased and dried to prevent residual moisture from affecting the vacuum level. The radome is made of vacuum-compatible material and there is no gas release. Vacuum pumping and detection: The interior is evacuated to the target vacuum level using a dedicated vacuum pumping system, and a helium mass spectrometer is used to detect leaks to ensure there are no leaks.

Claims

1. A method for efficient transmission of high-power microwaves, comprising the following steps: Step 1: Use a transition circular waveguide to connect to high-power microwaves. Step 2: By expanding the beam at a small angle, the high-power microwave is initially matched to the impedance characteristics of the transmission space, thereby reducing near-field reflections; Step 3: By expanding the beam at a large angle and transmitting it into space, the mode field impedance is gradually changed to the free space impedance, thus transforming the guided wave into a radiated wave. Step 4: Allow the radiation wave to radiate into free space through a low-loss sealing layer.

2. The high-efficiency transmission method for high-power microwaves as described in claim 1, characterized in that: The transition circular waveguide has an inner diameter of 0.64λ and a length of 0.48λ, with a smooth metal inner wall. High-power microwaves are transmitted linearly along the axis of the transition circular waveguide.

3. The high-efficiency transmission method for high-power microwaves and its dual-conical horn transmission antenna as described in claim 1, characterized in that: The small-angle beam-expanding transmission space has a small radius of 0.64λ, a large radius of 1.44λ, and a length of 3.456λ, and the cone angle satisfies the impedance gradient rate ≤ 5% / λ.

4. The high-efficiency transmission method for high-power microwaves as described in claim 1, characterized in that: The large-angle beam-expanding transmission space has a small radius of 1.424λ, a large radius of 5.52λ, and a length of 5.728λ. It is divided into three nonlinear gradient sections according to the target broadband. The low-frequency band is transmitted with a slow gradient rate of 3% / λ, the center frequency band is transmitted with a uniform gradient rate of 5% / λ, and the high-frequency band is transmitted with a fast gradient rate of 7% / λ. A fine-tuning section of 0.1λ is provided at the end of the high-frequency band.

5. The high-efficiency transmission method for high-power microwaves as described in claim 1, characterized in that: The inner wall of the transition section is a smooth curved surface, with the radius smoothly transitioning from a small cone with a large radius of 1.44λ to a large cone with a small radius of 1.424λ. The inner wall is coated with a 0.01λ thick dielectric film with a dielectric constant of 2.2, and the reflection coefficient is optimized to below -25dB.

6. The high-efficiency transmission method for high-power microwaves as described in claim 1, characterized in that: The high-power microwave propagates along a hyperboloid trajectory within a large-angle beam-expanding transmission space, with an inner wall conductivity ≥ 5.8 × 10⁻⁶. 7 The surface roughness is ≤0.1μm and the surface area is S / m.

7. The high-efficiency transmission method for high-power microwaves as described in claim 6, characterized in that: The hyperboloid trajectory equation x² / a²-y² / b²=1 has its focus coinciding with the center of the output end of the small cone.

8. The high-efficiency transmission method for high-power microwaves as described in claim 1, characterized in that: The output end of the large-angle beam-expanding transmission space is sealed by a low-loss polymer antenna radome, and the transmission space is filled with inert gas.

9. A high-power microwave dual-conical horn transmission antenna as described in claims 1-8, characterized in that: It includes a transition circular waveguide (2), a small conical horn (3), and a large conical horn (4). One end of the transition circular waveguide (2) is equipped with a waveguide flange (1), and the other end is fixedly connected to the small diameter end of the small conical horn (2). The large diameter end of the small conical horn (2) is connected to the small diameter end of the large conical horn (4) through the waveguide flange (1). The large diameter end of the large conical horn (4) is closed by an antenna cover (5).

10. A high-power microwave dual-conical horn transmission antenna as described in claim 9, characterized in that: The connection between the small conical horn (3) and the transition circular waveguide (2) is chamfered, and the waveguide flange (1) that docks with the large conical horn (4) is provided with a sealing groove and a sealing ring.

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