A low-profile ultrawideband folded horn antenna

Abstract

This invention discloses a low-profile ultra-wideband folded horn antenna, comprising a dielectric lens, a horn antenna, and a metal back cavity arranged sequentially from top to bottom. The horn antenna is placed within the metal back cavity, which encloses the bottom of the horn antenna and at least two symmetrically arranged sidewalls. This invention employs direct coaxial cable feeding and introduces multiple bent radiating arms, significantly reducing the profile height of the horn antenna and simplifying its structure. Simultaneously, by loading the dielectric lens and metal sidewalls, the gain within the operating frequency band is significantly improved. The dielectric lens and shielding cover are integrally formed, facilitating processing and installation. This antenna exhibits ultra-wideband characteristics, stable low-frequency gain, a cross-polarization level below -34dB, a symmetrical radiation pattern with good directivity, and stable overall radiation performance. This invention's antenna features a low profile, simple structure, compact size, and low manufacturing cost, meeting the requirements of 5G communication indoor distribution systems.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, specifically relating to a low-profile ultra-wideband folded horn antenna. Background Technology

[0002] The 5G communication system is a complex network architecture integrating multiple technologies and covering all scenarios. It can be divided into three core components: the core network, the transmission network, and the access network. These components work collaboratively to achieve end-to-end communication functions, from terminal access to data transmission and signal processing. The access network is responsible for converting wireless signals into wired signals and connecting them to the transmission network. Its components include macro base stations, small cell base stations, and indoor distribution systems. Indoor distribution systems are mainly used in enclosed indoor environments (such as office buildings, shopping malls, subways, and basements) to evenly distribute 5G signals within the enclosed space, solving the problem of high signal penetration loss in macro base stations and avoiding "signal dead zones" or "weak coverage areas." Directional antennas, with their high gain and high directionality, can improve the coverage distance and signal penetration ability of the target area, reduce multipath effects, and are suitable for complex indoor environments such as offices and multi-story residential buildings. Indoor distribution systems can receive and transmit signals by distributing directional antennas in various directions, thereby achieving comprehensive indoor signal coverage.

[0003] As the signal transceiver device for the entire indoor distribution system, the performance of the antenna is crucial to communication quality. Achieving wideband coverage reduces the complexity of multi-antenna systems. Taking China Mobile as an example, its frequency bands are divided into 900MHz (Band 8), 1800MHz (Band 3), 1.9GHz (Band 39), 2GHz (Band 34), 2.3GHz (Band 40), 2.6GHz (Band 41), and 4.9GHz (n79). Traditional narrowband antennas require multiple antennas to cover different frequency bands, while wideband antennas can integrate multiple frequency band functions, simultaneously providing 2G / 3G / 4G / 5G communication services and saving space. Furthermore, the antenna gain directly affects the signal propagation distance, directivity determines the uniformity of signal coverage, and stable radiation performance is extremely important. When deploying antennas indoors, the antenna design also needs to consider cost and installation environment. A simple structure and a low profile can reduce the space occupied and processing costs. In summary, when designing indoor distributed directional antennas for 5G communication, the antennas should meet requirements such as wide bandwidth coverage, high gain, symmetrical radiation pattern, and low profile.

[0004] TEM-mode horn antennas are a type of high-gain antenna that balances ultra-wideband performance with good directivity. However, ultra-wideband performance often corresponds to a large antenna size, making miniaturization challenging. Current miniaturization methods primarily rely on end-loading. End-loading achieves miniaturization by reducing reflected current on the low-frequency antenna surface, but this increases losses and antenna design complexity, necessitating improvements to the miniaturization method. Meanwhile, some relatively small TEM-mode horn antennas suffer from low gain and limited power capacity, requiring improved radiation performance. This can be achieved through methods such as dielectric filling or dielectric lens loading to enhance antenna gain. In conclusion, optimizing the miniaturization methods and radiation performance of traditional TEM-mode horn antennas is of significant importance for the practical application of 5G communication indoor distribution systems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of TEM-mode horn antennas in terms of profile height and radiation performance by proposing an ultra-wideband folded horn antenna applicable to 5G communication indoor distribution systems. This antenna features wide bandwidth coverage, low profile, and high gain. The invention employs direct coaxial cable feeding and introduces multiple bent radiating arms, significantly reducing the profile height of the horn antenna and simplifying its structure. Simultaneously, by loading a dielectric lens and metal sidewalls, the gain within the operating frequency band is significantly improved. The dielectric lens and housing are integrally formed, facilitating fabrication and installation. This antenna exhibits ultra-wideband characteristics, with a relative bandwidth of 152.1% (0.68-5GHz, VSWR < 2); a gain of 6-13.6 dBi within the operating frequency band, with stable low-frequency gain; a cross-polarization level below -34 dB; a symmetrical radiation pattern with good directivity; and stable overall radiation performance. Furthermore, the antenna profile height is 0.24λ. g (λ) g The wavelength corresponding to the lowest operating frequency of the folded horn antenna is not only simple in structure and small in size, but also low in manufacturing cost, which can meet the needs of 5G communication indoor distribution systems and has broad application prospects.

[0006] Specifically, the present invention provides a low-profile ultra-wideband folded horn antenna, comprising a dielectric lens, a horn antenna, and a metal back cavity arranged sequentially from top to bottom, wherein the horn antenna is placed inside the metal back cavity, and the metal back cavity surrounds the bottom of the horn antenna and at least two symmetrically arranged sidewalls.

[0007] The center of the dielectric lens is located on the horizontal plane where the larger opening of the horn antenna is located, and it does not contact the horn antenna;

[0008] The horn antenna includes two axisymmetric horn antenna surfaces; a horn-shaped notch exists between the two horn antenna surfaces; each horn antenna surface is an integrally formed structure, including an antenna metal panel, a horizontal metal extension panel, a vertically bent metal arm, and a metal matching stub; the bottom end of the antenna metal panel is connected to one end of the metal matching stub, and the top end is connected to one end of the horizontal metal extension panel; the other end of the horizontal metal extension panel is connected to the top end of the vertically bent metal arm; the bottom end of the vertically bent metal arm is in contact with the metal back cavity.

[0009] Preferably, the antenna further includes a shield, wherein the dielectric lens is embedded inside the shield and the shield covers the horn antenna and the metal back cavity.

[0010] Preferably, the shielding cover is made of the same material as the dielectric lens.

[0011] Preferably, the focal point of the dielectric lens coincides with the center of the smaller opening of the horn antenna.

[0012] Preferably, the antenna metal panel is composed of multiple metal surfaces with different tilt angles, the tilt angles being set along the side of the horn-shaped notch.

[0013] Preferably, the metal matching stub has an L-shaped structure, including a horizontal metal stub and a vertical metal stub. The horizontal metal stub is connected to the antenna metal panel, and the vertical metal stub is in contact with the metal back cavity. The impedance matching of the antenna can be adjusted by adjusting the length of the horizontal metal stub.

[0014] Preferably, the width of the metal matching stub is the same as the width of the smaller opening on the horn antenna surface.

[0015] Preferably, the metal back cavity includes a metal floor and two metal sidewalls located at opposite ends of the metal floor; the metal sidewalls are perpendicular to the metal floor. There is a gap between the metal sidewalls and the horn antenna.

[0016] Preferably, when the antenna operates at low frequencies, a resonant cavity is formed between the vertically bent metal arm and the metal sidewall.

[0017] Preferably, the coaxial feed line is placed above one of the metal matching stubs, the outer conductor is connected to the same side of the horn antenna surface at the narrow end of the horn antenna, and the inner conductor extends through to the opposite side of the narrow end of the horn antenna surface and is connected thereto.

[0018] The present invention has the following advantages:

[0019] This antenna utilizes multiple bent radiating arms, resulting in a relatively low profile height of 0.24λ. g (λ) g(The wavelength corresponding to the lowest operating frequency of the folded horn antenna) is easy to manufacture.

[0020] The antenna is loaded with a dielectric lens, which can improve the antenna gain, stabilize the gain in the operating frequency band at 6-13.6 dBi, and reduce gain fluctuations in the operating frequency band.

[0021] The antenna's dielectric lens and shield are made of the same material and are 3D printed in one piece, making them easy to process and install.

[0022] The antenna is directly fed by a coaxial cable, and its overall structure is simple.

[0023] The antenna operates in the 0.68-5GHz frequency band, with a voltage standing wave ratio of less than 2, achieving full coverage of the communication frequency band and a stable radiation pattern. Attached Figure Description

[0024] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a three-dimensional structural schematic diagram (without shielding) of the low-profile ultra-wideband folded horn antenna provided in an embodiment of the present invention.

[0026] Figure 2 yes Figure 1 A schematic diagram of the structure of the dielectric lens (without shielding).

[0027] Figure 3 This is a three-dimensional structural schematic diagram (with shielding) of the low-profile ultra-wideband folded horn antenna provided in an embodiment of the present invention.

[0028] Figure 4 This is a schematic diagram of the shielding cover and dielectric lens of the present invention.

[0029] Figure 5 yes Figure 1 Side view of the structure in the x-direction (without shielding).

[0030] Figure 6 yes Figure 1 Front top view of the structure (without shielding).

[0031] Figure 7 This is a simulation diagram of the reflection coefficient in the operating frequency band of the present invention.

[0032] Figure 8 This is a simulation diagram of the operating frequency band gain of the present invention.

[0033] Figure 9 This is a comparison of the simulation results of the present invention under the main polarization and cross-polarization at 0.7 GHz; where (a) is the normalized E-plane and (b) is the normalized H-plane.

[0034] Figure 10 This is a comparison of the simulation results of the present invention under the main polarization and cross-polarization at 1.5 GHz; where (a) is the normalized E-plane and (b) is the normalized H-plane.

[0035] Figure 11 This is a comparison of the simulation results of the present invention under the main polarization and cross-polarization at 2GHz; where (a) is the normalized E-plane and (b) is the normalized H-plane.

[0036] Figure 12 This is a comparison of the simulation results of the present invention under the main polarization and cross-polarization at 3.3 GHz; where (a) is the normalized E-plane and (b) is the normalized H-plane.

[0037] Figure 13 This is a comparison of the simulation results of the present invention under the main polarization and cross-polarization at 4.2 GHz; where (a) is the normalized E-plane and (b) is the normalized H-plane.

[0038] Figure 14 This is a comparison of the simulation results of the present invention under the main polarization and cross-polarization at 5GHz; where (a) is the normalized E-plane and (b) is the normalized H-plane.

[0039] The markings in the diagram are: 1. Dielectric lens; 2. Horn antenna; 21. Horn antenna surface; 211. Antenna metal panel; 2111. Metal surface; 212. Horizontal metal extension panel; 213. Vertically bent metal arm; 214. Metal matching stub; 22. Horn-shaped notch; 3. Metal back cavity; 31. Metal ground plane; 32. Metal sidewall; 4. Shielding cover; 5. Coaxial feed line. Detailed Implementation

[0040] The present invention will be further analyzed below with reference to specific embodiments.

[0041] At least one embodiment provides a low-profile ultra-wideband folded horn antenna for use in 5G communication indoor distribution systems. It operates in the 0.68-5GHz frequency band with a profile height of 0.24λg, featuring wide bandwidth coverage and a low profile. A dielectric lens is placed above the antenna to improve overall antenna gain and mitigate the problem of a dip in the main radiation direction of the high-frequency radiation pattern. The profile height is significantly reduced by bending some radiating arms downwards, while the vertically bent radiating arms (i.e., vertically bent metal arms) are connected to a metal ground plane to adjust impedance matching at low frequencies. To improve the radiation performance of the folded antenna, metal sidewalls are added to both sides of the vertically bent metal arms, significantly improving low-frequency gain. The main radiating part of the antenna is a metal structure, directly fed by a coaxial cable. The overall structure is simple, with the dielectric lens and antenna shield integrally formed, making it easy to manufacture and cost-effective, suitable for mass production applications, and showing great promise for 5G communication indoor distribution systems.

[0042] Specifically, such as Figure 1 As shown, the low-profile ultra-wideband folded horn antenna has an axisymmetric structure, including a dielectric lens 1, a horn antenna 2, and a metal back cavity 3 arranged sequentially from top to bottom. The horn antenna 2 is placed inside the metal back cavity 3, and the bottom of the horn antenna 2 and at least two symmetrically arranged sidewalls are wrapped by the metal back cavity 3.

[0043] One implementation method, such as Figure 3 As shown, the antenna also includes a shield 4, wherein the height of the shield 4 is slightly higher than the height of the horn antenna 2, and both the horn antenna 2 and the metal back cavity 3 are located inside the shield 4. Specifically, the dielectric lens 1 is embedded in the upper part of the shield 4, and the shield 4 completely covers the horn antenna 2 and the metal back cavity 3 around and above.

[0044] Furthermore, such as Figure 2 As shown, the height of the metal sidewall 32 is slightly lower than the height of the vertically bent metal arm 213.

[0045] Furthermore, the shielding cover 4 is made of the same material as the dielectric lens 1, which is a weakly conductive photosensitive resin material, such as C-UV 9400EM resin with a dielectric constant of 3.6. As an example, the shielding cover 4 is a box-shaped structure with an open bottom and a closed top, with a thickness of 2 mm and a length L. s It is 320mm long and has a width of W. s It is 178mm long and has a height of H. s It is 113mm.

[0046] Furthermore, the dielectric lens 1 is placed above the horn antenna 2 and at a certain distance, with its center located on the horizontal plane where the larger opening of the horn antenna 2 is located; furthermore, the focal point of the dielectric lens 1 coincides with the center position of the smaller opening of the horn antenna 2.

[0047] As an example, such as Figure 4 As shown, the dielectric lens 1 is semi-cylindrical, with its length matching the width of the metal ground plate 31, and is suspended directly above the radiating aperture of the horn antenna 2. In this embodiment, the dielectric lens 1 is semi-cylindrical, with its rectangular surface connected to the upper plane inside the shielding cover 4, and its curved surface facing downwards towards the horn antenna 2, thus focusing electromagnetic waves. Its diameter L... m It is 72mm in diameter and has a length of W. m The diameter is 168mm. Besides the semi-cylindrical shape, other shapes can also be used to achieve the same result. The dielectric lens 1 and the shielding cover 4 are integrally formed, which can be achieved by 3D printing for easy processing and installation.

[0048] like Figure 2 As shown, the horn antenna 2 includes two axisymmetric horn antenna surfaces 21; a horn-shaped notch 22 exists between the two horn antenna surfaces 21, and the two horn antenna surfaces 21 do not contact each other; each horn antenna surface 21 is an integrally formed structure, including an antenna metal panel 211, a horizontal metal extension panel 212, a vertically bent metal arm 213, and a metal matching branch 214; the bottom end of the antenna metal panel 211 is connected to one end of the metal matching branch 214, and the top end is connected to one end of the horizontal metal extension panel 212; the other end of the horizontal metal extension panel 212 is connected to the top end of the vertically bent metal arm 213; the bottom end of the vertically bent metal arm 213 contacts the metal back cavity 3. As an example, the horn antenna 2 is made of copper / aluminum with a thickness of 1mm, a narrow end (i.e., smaller opening) spacing of 1.7mm, and a wide end (i.e., larger opening) spacing of 182mm.

[0049] Furthermore, such as Figures 5-6 As shown, each antenna metal panel 211 facing another antenna metal panel 211 is composed of multiple metal surfaces 2111 with different tilt angles α. The tilt angle gradually decreases along the side of the horn-shaped notch 22, but the width gradually increases, and the outline is an exponential function curve. The projections of the antenna metal panel 211 in the frontal and lateral directions are different exponential function curve forms. Specifically, from the narrow end to the wide end of the horn antenna 2, the angle α between each metal surface 2111 and the horizontal plane gradually decreases.

[0050] As an example, in this embodiment, the antenna metal panel 211 uses three bent metal surfaces 2111 to fit an exponential function curve, which facilitates processing. The effects of this invention can be achieved using either an exponential function curve arc surface or a combination of bent metal planes. The first, second, and third metal surfaces are all isosceles trapezoids with an overall height H. ant It is 93mm in diameter and has a length of L. antThe first metal section is located at the narrow end of the horn antenna 3, with a vertical extension surface of width W3 of 10mm at its front end, connected to the metal matching stub. The total height of the first metal section is 20mm, and the width gradually changes from 10mm W3 to 44mm W2 as the height increases. The second metal section has a height H2 of 28mm, a length L2 of 10mm, and a width that gradually changes from 44mm W2 to 92mm W1. The third metal section has a height H1 of 45mm, a length L1 of 76mm, and similarly, a width that gradually changes from 92mm W1 to 899mm W2. gnd 168mm.

[0051] The horizontal metal extension panel 212 is rectangular, parallel to the metal floor, and its width is the same as W. gnd Consistent, length L arm It is 38mm.

[0052] Furthermore, the vertically bent metal arm 213 is an extension of the wide end of the antenna metal panel 211, perpendicular to the metal floor 31, and connects the wide end of the antenna metal panel 211 and the metal floor 31. In this embodiment, the width of the vertically bent metal arm 213 is W. gnd Height H arm It is 104mm.

[0053] As an example, the metal matching stub 214 has an L-shaped structure, located between the narrow end of the horn antenna surface 21 and the metal ground plane 31, and is used to adjust the impedance matching of the antenna. It includes a horizontal stub and a vertical stub; the horizontal stub is connected to the antenna metal panel 211, and the vertical stub contacts the metal back cavity 3. The impedance matching of the antenna is adjusted by adjusting the length of the horizontal stub. In this embodiment, the width of the vertical stub is W3, and the height is H. m The width of the horizontal branch is 6mm; the width of the horizontal branch is also W3, and the length is L. m It is 50mm.

[0054] Furthermore, the width of the metal matching stub 214 is the same as the width of the smaller opening of the horn antenna surface 21.

[0055] As an example, the metal back cavity 3 includes a metal floor 31 and two metal sidewalls 32 located at both ends of the metal floor 31. The metal sidewalls 32 are placed parallel to both sides of the vertically bent metal arm 213, connected to the metal floor 31 and perpendicular to the metal floor 31. There is a gap between the metal sidewalls 32 and the horn antenna 2. In this embodiment, the metal floor 31 is located below the entire antenna and has a length L. gnd It is 310mm long and the width is W. gnd The metal sidewall 32 maintains a certain distance from the vertically bent metal arm 213, and its width is the same as the width of the metal floor 31, with a height H. gnd It is 99mm.

[0056] Furthermore, when the antenna operates at low frequencies, a resonant cavity is formed between the vertically bent metal arm 213 and the metal sidewall 32.

[0057] Furthermore, such as Figure 1 , 3 As shown, the coaxial feed line 5 is placed above one of the metal matching stubs 214. The outer conductor is connected to the narrow end of the horn antenna 2 on the same side, and the inner conductor extends through to the narrow end of the horn antenna surface 21 on the opposite side and is connected to it.

[0058] Specific working principle: The folded horn antenna is connected to a 50Ω coaxial feed line 5. A TEM wave is excited at the narrow end of the horn antenna 2 and propagates along the horn antenna surface 2-1. When the TEM wave reaches the opening at the narrow end of the horn antenna 2, as the conductor spacing gradually increases, the electric field expands outward from the vertical distribution at the narrow end, and the magnetic field gradually expands from the closed loop. Some energy escapes the conductor's constraint, forming a radiation field, and the electromagnetic field transitions from a bound state to a free-space radiation state. To reduce the antenna's profile, the upward-extending radiating arm of the horn antenna 2 is bent to a metal ground plane. The vertically bent metal arm 213, connecting the horn antenna surface 21 and the metal ground plane 31, can adjust the antenna's reactance characteristics, thereby improving the antenna's impedance matching and achieving broadband characteristics. Since the folded horn antenna has low low-frequency gain, metal sidewalls 32 are added to both sides of the vertically bent metal arm 213. When the antenna operates at low frequencies, more current is distributed on the vertically bent metal arm 213 and the metal sidewalls 32 to form a resonant cavity, enhancing the low-frequency gain. At higher frequencies, the folded horn antenna may excite higher-order modes, leading to main lobe splitting in the radiation pattern and a decrease in forward gain. Therefore, a dielectric lens 1 is loaded onto the larger opening surface of the horn notch 22 of the horn antenna 2. The dielectric lens 1 adjusts the optical path of the electromagnetic wave in the medium. The divergent spherical wave is refracted by the dielectric lens 1 and converted into a parallel plane wave, compensating for the phase difference and concentrating the energy within a narrow beam, significantly improving the antenna gain. Reducing the electric field phase difference at the horn aperture avoids main lobe splitting at high frequencies, thus improving the forward gain at high frequencies. To minimize the impact of the dielectric lens 1 on impedance matching, its size is minimized, and it is only added directly above the horn aperture.

[0059] Figure 7 The figure shows the voltage standing wave ratio (VSWR) simulation results of the low-profile ultra-wideband folded horn antenna of the present invention applied to the indoor distribution system of 5G communication. The VSWR is less than 2 in the range of 0.68-5GHz, the relative bandwidth is 152.1%, the antenna has the characteristics of wide bandwidth coverage, and the impedance matching is good.

[0060] Figure 8The figure shows the gain simulation results of the low-profile ultra-wideband folded horn antenna of the present invention applied to the indoor distribution system of 5G communication. The gain is 6-13.6 dBi in the operating frequency band. The low-frequency gain is relatively stable and has the characteristics of high gain.

[0061] Figure 9 (a) Figure 9 (b) Figure 10 (a) Figure 10 (b) Figure 11 (a) Figure 11 (b) Figure 12 (a) Figure 12 (b) Figure 13 (a) Figure 13 (b) Figure 14 (a) Figure 14 Figure (b) shows a comparison of the simulation results of the normalized E-plane and H-plane main polarization and cross-polarization of the present invention at 0.7 GHz, 1.5 GHz, 2 GHz, 3.3 GHz, 4.2 GHz, and 5 GHz. The horn antenna designed in this invention has a symmetrical radiation pattern with no dips in the main radiation direction, exhibiting good directivity. The cross-polarization curves in the figure clearly show that the antenna has a low cross-polarization level, all less than -34 dB. This antenna demonstrates stable radiation performance and is an excellent directional antenna.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the implementation of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and all such improvements and modifications should be included within the scope of protection of the claims of the present invention.

Claims

1. A low-profile ultrawideband folded horn antenna, characterized in that, It includes a dielectric lens (1), a horn antenna (2), and a metal back cavity (3) arranged sequentially from top to bottom, wherein the horn antenna (2) is placed inside the metal back cavity (3), and the bottom of the horn antenna (2) and at least two symmetrically arranged side walls are wrapped by the metal back cavity (3); The center of the dielectric lens (1) is located on the horizontal plane where the larger opening of the horn antenna (2) is located, and it does not contact the horn antenna (2); the focal point of the dielectric lens (1) coincides with the center of the smaller opening of the horn antenna (2); the dielectric lens (1) is semi-cylindrical, with the arc surface facing the horn antenna (2) below. The horn antenna (2) includes two axisymmetric horn antenna surfaces (21); a horn-shaped notch (22) exists between the two horn antenna surfaces (21); each horn antenna surface (21) is an integrally formed structure, including an antenna metal panel (211), a horizontal metal extension panel (212), a vertically bent metal arm (213), and a metal matching stub (214); the bottom end of the antenna metal panel (211) is connected to one end of the metal matching stub (214), and the top end is connected to one end of the horizontal metal extension panel (212); the other end of the horizontal metal extension panel (212) is connected to the top end of the vertically bent metal arm (213); the bottom end of the vertically bent metal arm (213) is in contact with the metal back cavity (3); Each antenna metal panel (211) faces another antenna metal panel (211), and is composed of multiple metal surfaces (2111) with different tilt angles α. The tilt angle gradually decreases along the side of the horn-shaped notch (22), but the width gradually increases. The outline is an exponential function curve. The projection of the antenna metal panel (211) in the front and side directions are different exponential function curve forms. TEM waves are excited in the smaller opening of the horn antenna (2) and propagate along the horn antenna surface (21). When the TEM waves reach the smaller opening of the horn antenna (2), as the conductor spacing gradually increases, the electric field starts to expand outward from the vertical distribution of the smaller opening, the magnetic field gradually expands from the closed loop, some energy breaks free from the conductor binding and forms a radiation field, and the electromagnetic field transitions from the bound state to the free space radiation state. Metal sidewalls (32) are added on both sides of the vertically bent metal arm (213). When the antenna works at low frequency, the current is more distributed on the vertically bent metal arm (213) and the metal sidewalls (32) to form a resonant cavity and enhance the low frequency gain. A dielectric lens (1) is added only directly above the horn aperture.

2. The antenna according to claim 1, characterized in that, Includes a shield (4), wherein the dielectric lens (1) is embedded above the inside of the shield (4), and the shield (4) covers the horn antenna (2) and the metal back cavity (3) around and above.

3. The antenna according to claim 2, characterized in that, The shield (4) is made of the same material as the dielectric lens (1).

4. The antenna according to claim 1, characterized in that, The metal matching stub (214) is an L-shaped structure, including a horizontal metal stub and a vertical metal stub. The horizontal metal stub is connected to the antenna metal panel (211), and the vertical metal stub is in contact with the metal back cavity (3). The impedance matching of the antenna can be adjusted by adjusting the length of the horizontal metal stub.

5. The antenna according to claim 1, characterized in that, The width of the metal matching stub (214) is the same as the width of the smaller opening of the horn antenna surface (21).

6. The antenna according to claim 1, characterized in that, The metal back cavity (3) includes a metal floor (31) and two metal sidewalls (32) located at both ends of the metal floor (31); the metal sidewalls (32) are arranged perpendicularly to the metal floor (31); and there is a gap between the metal sidewalls (32) and the horn antenna (2).

7. The antenna according to claim 1, characterized in that, The coaxial feed line (5) is placed above one of the metal matching stubs (214). The outer conductor is connected to the same side of the horn antenna surface (21) at the narrow end of the horn antenna (2), and the inner conductor extends through to the opposite side of the narrow end of the horn antenna surface (21) at the narrow end of the horn antenna (2) and is connected thereto.

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