Hilbert fractal medium-short wave antenna

Abstract

The utility model discloses a Hilbert fractal medium-short wave antenna, which belongs to the field of antennas and comprises a radiation part, an earth screen part and a feed part. The radiation part comprises a metal supporting rod, a Hilbert fractal structure and a wave trap, an original surface current distribution path is cut off, a cascade inductor is introduced, and the high-frequency skin effect is inhibited. The earth screen system is of a double-layer structure, a middle earth screen intercepts space waves, and a bottom earth screen is connected with ferrite magnetic beads in series to absorb common-mode noise. A balun and a pi-T mixed matching network are arranged in the feed system, and the standing-wave ratio is smaller than or equal to 1.5. The working bandwidth of the antenna is 526.5 KHz-28 MHz, the interference suppression depth is-35 dB, and the antenna is suitable for portable emergency communication and fixed monitoring stations.

Description

Technical Field

[0001] This utility model relates to the field of radio antenna technology, specifically to a Hilbert fractal medium-shortwave antenna. Background Technology

[0002] Currently, medium and shortwave receiving antennas generally suffer from three major drawbacks: narrow spectrum, such as traditional rod antennas with a single resonant point, making it difficult to cover the entire frequency band of 526.5KHz-28MHz; low efficiency, such as compact loop antennas with insufficient effective height and weak signal acquisition capability; and large footprint, such as high-efficiency line antennas requiring tens of meters of installation space, which limits mobile monitoring scenarios.

[0003] While existing patent CN222015684 U introduces Minkowski fractals to improve bandwidth, its linear splicing structure has limited current path extension and does not optimize multi-band impedance matching. In contrast, the spatial folding characteristics of Hilbert fractals can significantly reduce volume, making it particularly suitable for mobile reception and testing, such as rapid outdoor deployment, omnidirectional transmission and reception of medium and shortwave signals, fixed monitoring stations, and unattended rooftop remote control stations for long-term radio spectrum reception. Furthermore, the Hilbert fractal order in this application is scalable; in practice, it can be further fractalized to the fifth or seventh order to adapt to different frequency bands and bandwidths, depending on the requirements. Utility Model Content

[0004] This invention aims to provide a Hilbert fractal mid-shortwave antenna that extends the current path through a spatial folding structure and combines a rhomboid grid, a dual ground network, and a π-T matching network to achieve wide-spectrum, high interference immunity, and portable mid-shortwave full-band transmission and reception.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] A Hilbert fractal mid-to-shortwave antenna includes a radiating section, a ground grid section, and a feed section.

[0007] The radiating section includes a metal support rod, a Hilbert fractal structure, and a notch filter;

[0008] The Hilbert fractal structure is welded to the top of the metal support rod.

[0009] Hilbert fractal structure is a folded metal wire with a diamond grid structure on the surface;

[0010] The notch filter is positioned on the side of the Hilbert fractal structure and the metal support rod.

[0011] Furthermore, the diamond grid has a depth of 1mm, a line width of 1mm, and an inclination angle of 45°±5%, which makes the surface current flow around the edge of the slot in a tortuous manner, thus lengthening the path and effectively introducing cascaded inductance.

[0012] Furthermore, the rhomboid grid can be formed by laser etching, chemical etching, or precision stamping.

[0013] Furthermore, the metal support rod is equipped with a diamond-shaped grid structure.

[0014] Furthermore, the Hilbert fractal structure can be replaced with a Koch fractal result, a tree fractal result, or a metal ring structure.

[0015] Furthermore, the grounding grid consists of a central grounding grid and a bottom grounding grid, with the bottom grounding grid connected in series with ferrite beads.

[0016] The central grounding grid is set in the middle of the metal support rod, and the bottom grounding grid is welded to the bottom of the metal support rod.

[0017] Furthermore, the central grounding grid is laid out radially with metal wires to intercept spatial electromagnetic waves; the bottom grounding grid is laid out radially with metal wires and buried underground; and series-connected ferrite beads absorb common-mode noise.

[0018] Furthermore, the power supply section includes a balun box; the balun box has a built-in 1:1 balun and π-T hybrid matching network; the balun box is connected to an external feeder, a bottom grounding grid, and a metal support rod.

[0019] Furthermore, the balun box is connected to the bottom ground grid and the metal support rod by metal bolts, and the balun box is connected to the external feeder via the female square plate RF head.

[0020] Furthermore, to prevent the feeder from introducing externally induced alternating current, the feeder is first wound around a ferrite core before connecting to the female connector square board RF head.

[0021] Compared with existing technologies, this invention adopts a Hilbert fractal structure with a space-filling curve design, which extends the current path by 3.2 times within a limited volume compared to a linear antenna of the same size. The fractal structure naturally generates four resonant points, achieving wideband transmission and reception with a -10dB return loss curve, covering the 526.5KHz-28MHz frequency band. Dual ground grid coupling uses a central ground grid to intercept spatial electromagnetic waves and a bottom ground grid to absorb induced current from the ground surface, effectively improving the signal-to-noise ratio. The grid structure extends the surface current path, constrains high-frequency current to the edge of the etched groove, reduces internal conductor losses, and suppresses the skin effect, thereby improving medium and shortwave transmission and reception performance. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the Hilbert fractal shortwave antenna of this utility model;

[0023] Figure 2 This is a schematic diagram of the internal and external wiring of the Hilbert fractal medium-shortwave antenna balun box of this utility model;

[0024] Figure 3 This is a schematic diagram of the Hilbert fractal shortwave antenna notch filter of this utility model;

[0025] Figure 4 This is a partial schematic diagram of the grounding grid installation in the middle of the Hilbert fractal medium-shortwave antenna of this utility model;

[0026] Figure 5 This is a schematic diagram of the metal support rod bracket for the Hilbert fractal medium-shortwave antenna of this utility model;

[0027] In the diagram: 101-Middle ground grid, 102-Bottom ground grid, 2-Metal support rod, 3-Hilbert fractal structure, 401-Notch filter, 402-Ballon box, 5-Female square plate RF head, 6-Feeder line, 7-Ni-Zinc magnetic ring, 8-Metal bolt, 9-Enameled wire, 10-Ferrite core, 11-Ferrite bead. Detailed Implementation

[0028] Example 1

[0029] refer to Figure 1 This application provides a Hilbert fractal mid-to-shortwave antenna, including a radiating section, a ground grid section, and a feeding section.

[0030] The radiating section includes a metal support rod 2, a Hilbert fractal structure 3, and a notch filter 401;

[0031] The Hilbert fractal structure 3 is welded to the top of the metal support rod 2. The Hilbert fractal structure 3 is a third-order spatial folded metal wire, with each order having a length ≈ λ / 4. The total length L of the Hilbert fractal structure 3 satisfies:

[0032]

[0033] Where λ k λ is the center wavelength of the k-th order fractal target frequency band, with a total length range of 5.6λ to 8.2λ, where λ is the wavelength of the lowest frequency point.

[0034] Metal support rod 2 and Hilbert fractal structure 3 are etched with a rhombus grid; the rhombus grid has a depth of 1mm, a line width of 1mm, and an inclination angle of 45°±5%, causing the surface current to flow around the edge of the slot in a tortuous manner, thus lengthening the path and effectively introducing cascaded inductance; this constrains the high-frequency current path, suppresses the skin effect, and reduces conductor loss; the rhombus grid can be formed by laser etching, chemical etching, or precision stamping. The Hilbert fractal structure 3 can be replaced with a Koch fractal result, a tree-like fractal result, or a metal ring structure. Notch filter 401 is disposed on the side of Hilbert fractal structure 3 and metal support rod 2; it suppresses specific interference frequencies, such as 1.8MHz and 7.1MHz.

[0035] refer to Figure 1 , 4 The grounding grid includes a central grounding grid 101 and a bottom grounding grid 102, with the bottom grounding grid 102 connected in series with ferrite beads 11. The central grounding grid 101 is located in the middle of the metal support rod 2, and the bottom grounding grid 102 is welded to the bottom of the metal support rod 2. The central grounding grid 101 is laid radially with metal wire to intercept spatial electromagnetic waves; the bottom grounding grid 102 is laid radially with metal wire and buried underground; the series-connected ferrite beads 11 absorb common-mode noise.

[0036] refer to Figure 2 The power supply section includes a balun 402; the balun 402 has a built-in 1:1 balun and π-T hybrid matching network; the balun 402 has an external feed line 6, a bottom ground grid 102, and a metal support rod 2; the balun 402 is connected to the bottom ground grid 102 and the metal support rod 2 by metal bolts 8, and the balun 402 has an external feed line 6 connected by a female square plate RF connector 5. The antenna has an IP65 protection rating, and the notch filter 401 and the balun 402 are filled with silicone gel for waterproofing.

[0037] The balun box consists of a waterproof plastic box and a female square board RF head 5. The waterproof plastic box contains a nickel-zinc magnetic ring 7, a circuit board, and metal bolts 8. Three enameled wires 9 are wound on the magnetic ring. One side of the enameled wires 9 is connected to the female square board RF head 5, and the other side of the enameled wires 9 leads out two connectors. The two connectors are connected to the circuit board and are connected to the bottom ground grid 102 and the metal support rod 2 through the metal bolts 8.

[0038] The antenna incorporates an anti-interference design. To prevent the feed line 6 from introducing externally induced alternating current, the feed line 6 can be wound around the ferrite core 10 before connecting to the female square board RF head 5. The ferrite core model is FT-240-4310.

[0039] Example 2

[0040] This application provides a Hilbert fractal mid-shortwave antenna, which includes a radiating part, a ground grid part, and a feeding part. The radiating part includes a metal support rod 2, a Hilbert fractal structure 3, and a notch filter 401. The Hilbert fractal structure 3 is made of 2mm diameter phosphor bronze wire, which is formed by three-order spatial folding and has a total length of 8.2m. It is welded to the top of the metal support rod 2. The notch filter is RLC parallel resonant at a specific interference frequency.

[0041] The central grounding grid consists of 24 tin-plated copper wires laid radially at 15° intervals, using short 304 stainless steel poles with an arm length of 30cm and a height of 1.2m above the ground; the bottom grounding grid consists of 12 copper wires buried at a depth of 20cm.

[0042] Circuit parameters: π-T type matching network: L1 = 2.2μH, C1 = 100pF, C2 = 220pF, covering 500KHz-30MHz.

[0043] The preferred embodiments of this patent have been described in detail above. However, this patent is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, other changes can be made without departing from the spirit of this patent. For example, the Hilbert fractal structure can be replaced with a Koch / tree fractal or a metal ring (square ring / circular ring); the central ground grid can be replaced with a structure that supports multiple layers of cross short rods (3 / 5 layers) or a star-shaped structure; the ground grid density is selected to be 36 metal wires laid radially at 10° intervals and fixed with galvanized ground nails.

Claims

1. A Hilbert fractal mid-to-shortwave antenna, comprising a radiating section, a ground grid section, and a feeding section, characterized in that: The radiating section includes a metal support rod, a Hilbert fractal structure, and a notch filter; The Hilbert fractal structure is welded to the top of the metal support rod. The Hilbert fractal structure is a folded metal wire with a diamond grid structure on the surface. The notch filter is positioned on the side of the Hilbert fractal structure and the metal support rod.

2. The antenna according to claim 1, characterized in that: The diamond grid has a depth of 1mm, a line width of 1mm, and an inclination angle of 45°±5%, which makes the surface current flow around the edge of the slot in a tortuous manner, thus lengthening the path and effectively introducing cascaded inductance.

3. The antenna according to claim 1, characterized in that: The rhomboid grid can be formed by laser etching, chemical etching, or precision stamping.

4. The antenna according to claim 1, characterized in that: The metal support rod is equipped with a diamond-shaped grid structure.

5. The antenna according to any one of claims 1-4, characterized in that: The Hilbert fractal structure can be replaced by a Koch fractal result, a tree fractal result, or a metal ring structure.

6. The antenna according to claim 1, characterized in that: The grounding grid consists of a central grounding grid and a bottom grounding grid. The bottom grounding grid is connected in series with ferrite beads. The central grounding grid is located in the middle of the metal support rod, and the bottom grounding grid is welded to the bottom of the metal support rod.

7. The antenna according to claim 6, characterized in that: The central grounding grid is laid out radially with metal wires to intercept electromagnetic waves in space; the bottom grounding grid is laid out radially with metal wires and buried underground; and ferrite beads are connected in series to absorb common-mode noise.

8. The antenna according to claim 1, characterized in that: The power supply section includes a balun; the balun has a built-in 1:1 balun and π-T hybrid matching network; The balun box has an external feeder, a bottom grounding grid, and a metal support rod.

9. The antenna according to claim 8, characterized in that: The balun box is connected to the bottom ground grid and the metal support rod by metal bolts, and the balun box is connected to the external feeder via the female square board RF head.

10. The antenna according to claim 9, characterized in that: To prevent the feeder from introducing externally induced alternating current, the feeder is wound around a ferrite core before connecting to the RF head of the female connector.

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