Low-profile ultra-wideband folding horn antenna

Abstract

The low-profile ultra-wideband folding horn antenna comprises a dielectric lens, a horn antenna body and a metal back cavity which are sequentially arranged from top to bottom, the horn antenna body is arranged in the metal back cavity, and the metal back cavity wraps the bottom of the horn antenna body and at least two symmetrically-arranged side walls. According to the invention, the coaxial cable is adopted for direct feeding, and the multiple bent radiation arms are introduced, so that the profile height of the horn antenna is greatly reduced and the antenna structure is simplified; meanwhile, by loading the dielectric lens and the metal side wall, the gain in the working frequency band is remarkably improved, and the dielectric lens and the shielding cover are integrally formed, so that processing and mounting are facilitated. The antenna has the ultra-wideband characteristic, and the low-frequency gain performance is stable; the cross polarization level is lower than-34 dB, the radiation pattern is symmetrical and good in directivity, and the overall radiation performance is stable. The antenna is low in profile, simple in structure, small in size, low in manufacturing cost and capable of meeting the requirements of a 5G communication indoor distribution system.

Description

Technical Field

[0001] The present invention belongs to the technical field of antennas, and in particular relates to a low-profile ultra-wideband folded horn antenna. Background Art

[0002] The 5G communication system is a complex network architecture that integrates multiple technologies and covers all scenarios. It consists of three core components: the core network, the transmission network, and the access network. These components work together to implement the entire communication process, 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 and micro base stations, and indoor distribution systems. Indoor distribution systems are primarily used in enclosed indoor environments (such as office buildings, shopping malls, subways, and basements). They evenly distribute 5G signals within enclosed spaces, addressing the significant signal penetration loss of macro base stations and preventing "signal blind spots" or areas of weak coverage. Directional antennas, with their high gain and directivity, can improve coverage distance and signal penetration through walls, while reducing multipath effects. They are suitable for complex indoor environments such as offices and multi-story residential buildings. Indoor distribution systems achieve comprehensive indoor signal coverage by deploying directional antennas in various locations to receive and transmit signals.

[0003] Antennas, as the signal transmitters and receivers of the entire indoor distribution system, are crucial to communication quality. Antennas that provide wideband coverage can reduce the complexity of multi-antenna systems. For example, China Mobile's 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 bands, providing 2G / 3G / 4G / 5G communication services simultaneously while saving space. Furthermore, antenna gain directly affects signal propagation distance, while directivity determines signal coverage uniformity. Stable radiation performance is extremely important. When deploying antennas indoors, the design must balance cost and the installation environment. A simple structure and a low profile can reduce indoor space usage and processing costs. In summary, when designing indoor distributed directional antennas for 5G communications, the antennas should meet requirements such as wide-band coverage, high gain, symmetrical radiation pattern, and low profile.

[0004] TEM mode horn antennas are a type of high-gain antenna that combines ultra-wideband and good directivity. However, ultra-wideband performance often corresponds to a larger antenna size, and miniaturization design is difficult. The current miniaturization method mainly uses end loading. End loading achieves miniaturization by reducing the reflected current on the low-frequency antenna surface, but it increases losses and antenna design complexity, and the miniaturization method needs to be improved. However, some relatively small TEM mode horn antennas have disadvantages such as low gain and low power capacity, and their radiation performance needs to be improved. The antenna gain can be increased through methods such as dielectric filling or dielectric lens loading. In summary, optimizing the miniaturization method and radiation performance of traditional TEM mode horn antennas is of great significance to the practical application of 5G communication indoor distribution systems. Summary of the Invention

[0005] The purpose of the present invention is to address the shortcomings of the cross-sectional height and radiation performance of the TEM mode horn antenna, and to propose an ultra-wideband folded horn antenna that can be applied to the 5G communication indoor distribution system, which has the characteristics of wide-band coverage, low profile and high gain. The present invention adopts coaxial cable direct feeding and introduces multiple sections of bent radiation arms, which greatly reduces the cross-sectional height of the horn antenna and simplifies the antenna structure; at the same time, by loading the dielectric lens and the metal side wall, the gain within the working frequency band is significantly improved. The dielectric lens and the shell are formed in one piece, which is convenient for processing and installation. The antenna has ultra-wideband characteristics, with a relative bandwidth of 152.1% (0.68-5GHz, VSWR < 2); the gain within the working frequency band is 6-13.6dBi, among which the low-frequency gain performance is stable; the cross-polarization level is lower than -34dB, the radiation pattern is symmetrical and has good directionality, and the overall radiation performance is stable. In addition, the antenna cross-sectional 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 compact in size, but also low in production cost. It 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 in sequence from top to bottom, wherein the horn antenna is placed in the metal back cavity, and the metal back cavity wraps the bottom and at least two symmetrically arranged side walls of the horn antenna; The center of the dielectric lens is located at the horizontal plane where the larger opening of the horn antenna is located, and does not contact the horn antenna; The horn antenna includes two axially symmetrical horn antenna surfaces; there is a horn-shaped notch 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 branch; the bottom end of the antenna metal panel is connected to one end of the metal matching branch, 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.

[0007] Preferably, the antenna further comprises a shielding cover, wherein the dielectric lens is embedded above the inside of the shielding cover, and the shielding cover as a whole covers the surroundings and above the horn antenna and the metal back cavity.

[0008] Preferably, the shielding cover is made of the same material as the dielectric lens.

[0009] Preferably, the focus of the dielectric lens coincides with the center position of the smaller opening of the horn antenna.

[0010] Preferably, the antenna metal panel is composed of a plurality of metal surfaces with different inclination angles, and the inclination angles are set along the sides of the trumpet-shaped notch.

[0011] Preferably, the metal matching branch is an L-shaped structure, including a horizontal metal branch and a vertical metal branch. The horizontal metal branch is connected to the antenna metal panel, and the vertical metal branch is in contact with the metal back cavity. By adjusting the length of the horizontal metal branch, the impedance matching of the antenna can be adjusted.

[0012] Preferably, the width of the metal matching branch is the same as the width of the smaller opening of the horn antenna surface.

[0013] Preferably, the metal back cavity includes a metal floor and two metal side walls located at both ends of the metal floor; the metal side walls are perpendicular to the metal floor and there is a distance between the metal side walls and the horn antenna.

[0014] Preferably, when the antenna operates at a low frequency, a resonant cavity is formed between the vertically bent metal arm and the metal side wall.

[0015] Preferably, the coaxial feed line is placed above one of the metal matching branches, the outer conductor is connected to the horn antenna surface on the same side of the narrow end of the horn antenna, and the inner conductor extends through to the narrow end of the horn antenna surface on the opposite side of the narrow end of the horn antenna and is connected thereto.

[0016] The present invention has the following advantages: The antenna uses multiple curved radiating arms with a low cross-section height of 0.24λ. g (λ gis the wavelength corresponding to the lowest operating frequency of the folded horn antenna), which is easy to process.

[0017] The antenna is loaded with a dielectric lens, which can improve the antenna gain, stabilize the gain within the operating frequency band at 6-13.6dBi, and reduce gain fluctuations within the operating frequency band.

[0018] The antenna dielectric lens and shielding cover are made of the same material and are formed in one piece using 3D printing, making them easy to process and install.

[0019] The antenna is directly fed by a coaxial cable and has a simple overall structure.

[0020] The antenna operates in a frequency band of 0.68-5 GHz, with a voltage standing wave ratio of less than 2, achieving full coverage of the communication frequency band and a stable radiation pattern. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 3D schematic diagram of the low-profile ultra-wideband folded horn antenna provided by an embodiment of the present invention (without a shielding cover).

[0023] Figure 2 yes Figure 1 Schematic diagram of the structure without the dielectric lens (without shielding cover).

[0024] Figure 3 3D schematic diagram of the low-profile ultra-wideband folded horn antenna (with shielding cover) provided by an embodiment of the present invention; Figure 4 It is a schematic structural diagram of the shielding cover and dielectric lens of the present invention.

[0025] Figure 5 yes Figure 1 Side view of the structure in the x-direction (without shielding cover).

[0026] Figure 6 yes Figure 1 Front view of the structure (without shielding cover).

[0027] Figure 7 It is a simulation diagram of the reflection coefficient of the working frequency band of the present invention.

[0028] Figure 8 This is a simulation diagram of the working frequency band gain of the present invention.

[0029] Figure 9This is a comparison of the main polarization and cross-polarization simulation results of the present invention at 0.7 GHz; (a) is the normalized E-plane, and (b) is the normalized H-plane.

[0030] Figure 10 This is a comparison of the main polarization and cross-polarization simulation results of the present invention at 1.5 GHz; (a) is the normalized E-plane, and (b) is the normalized H-plane.

[0031] Figure 11 This is a comparison of the simulation results of the present invention at 2 GHz for main polarization and cross polarization; (a) is the normalized E-plane, and (b) is the normalized H-plane.

[0032] Figure 12 This is a comparison of the main polarization and cross-polarization simulation results of the present invention at 3.3 GHz; (a) is the normalized E-plane, and (b) is the normalized H-plane.

[0033] Figure 13 This is a comparison of the simulation results of the present invention at 4.2 GHz for main polarization and cross polarization; (a) is the normalized E-plane, and (b) is the normalized H-plane.

[0034] Figure 14 This is a comparison of the main polarization and cross-polarization simulation results of the present invention at 5 GHz; (a) is the normalized E-plane, and (b) is the normalized H-plane.

[0035] Markings in the figure: 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 branch; 22. Horn-shaped notch; 3. Metal back cavity; 31. Metal floor; 32. Metal side wall; 4. Shielding cover; 5. Coaxial feed line. DETAILED DESCRIPTION

[0036] The present invention will be further analyzed below with reference to specific embodiments.

[0037] At least one embodiment provides a low-profile ultra-wideband folded horn antenna for use in 5G communication indoor distribution systems. Its operating frequency band is 0.68-5 GHz, and its profile height is 0.24λg. It features wideband coverage and a low profile. A dielectric lens is placed above the antenna to improve the antenna's overall gain and address the problem of a concave main radiation direction in the radiation pattern at high frequencies. By bending a portion of the radiating arm downward, the profile height is significantly reduced. The vertically bent radiating arm (i.e., a vertically bent metal arm) is connected to a metal floor to adjust impedance matching at low frequencies. To improve the folded antenna's radiation performance, metal sidewalls are added to either side of the vertically bent metal arm, significantly increasing low-frequency gain. The antenna's main radiating portion is a metal structure, directly fed by a coaxial cable. The overall structure is simple, and the dielectric lens and antenna shield are integrally formed, making it easy to process and low-cost, suitable for large-scale production applications. It has great application prospects in 5G communication indoor distribution systems.

[0038] Specifically, if 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 in sequence from top to bottom, wherein the horn antenna 2 is placed in the metal back cavity 3, and the metal back cavity 3 wraps the bottom of the horn antenna 2 and at least two symmetrically arranged side walls; One implementation method, such as Figure 3 As shown, the antenna further includes a shielding cover 4, wherein the height of the shielding cover 4 is slightly higher than that of the horn antenna 2. The horn antenna 2 and the metal back cavity 3 are both located inside the shielding cover 4. Specifically, the dielectric lens 1 is embedded above the inside of the shielding cover 4, and the shielding cover 4 entirely covers the surrounding areas and above the horn antenna 2 and the metal back cavity 3.

[0039] Furthermore, if Figure 2 As shown, the height of the metal sidewall 32 is slightly lower than the height of the vertically bent metal arm 213 .

[0040] Furthermore, the shielding cover 4 is made of the same material as the dielectric lens 1, which is a weakly conductive photosensitive resin material, for example, C-UV 9400EM resin with a dielectric constant of 3.6. As an example, the shielding cover 4 is a box with an open bottom and a closed top, with a thickness of 2 mm and a length L. s 320mm, width W s 178mm, height H s It is 113mm.

[0041] Furthermore, the dielectric lens 1 is placed above the horn antenna 2 and kept at a distance, with its center located at the horizontal plane where the larger opening of the horn antenna 2 is located; further, the focus of the dielectric lens 1 coincides with the center position of the smaller opening of the horn antenna 2.

[0042] As an example, Figure 4 As shown, the dielectric lens 1 is semi-cylindrical, with a length consistent with the width of the metal floor 31, and is suspended directly above the radiation aperture of the horn antenna 2. In this embodiment, the dielectric lens 1 is semi-cylindrical, with a rectangular surface connected to the upper plane inside the shielding cover 4 and an arc surface facing the horn antenna 2 below, forming a focusing effect on the electromagnetic wave. The diameter L m 72mm, length W m The dielectric lens 1 and the shielding cover 4 are integrally formed and can be formed by 3D printing, which is convenient for processing and installation.

[0043] like Figure 2 As shown, the horn antenna 2 comprises 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 touch each other. Each horn antenna surface 21 is an integrally formed structure, comprising 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. By way of example, the horn antenna 2 is made of copper / aluminum with a thickness of 1 mm. The spacing at the narrow end (i.e., the smaller opening) is 1.7 mm, and the spacing at the wide end (i.e., the larger opening) is 182 mm.

[0044] Furthermore, if Figure 5-Figure 6 As shown, each antenna metal panel 211 faces another antenna metal panel 211 and is composed of multiple metal surfaces 2111 with different tilt angles ɑ. The tilt angle gradually decreases along the sides of the horn-shaped notch 22, while the width gradually increases, forming an exponential curve. The projections of the antenna metal panels 211 in the forward and lateral directions form different exponential curves. Specifically, the angle ɑ between each metal surface 2111 and the horizontal plane gradually decreases from the narrow end to the wide end of the horn antenna 2.

[0045] As an example, the antenna metal panel 211 of this embodiment uses three sections of bent metal surface 2111 to fit the exponential function curve, which is convenient for processing. The effect of the present invention can be achieved by using the exponential function curve arc surface or the combined bent metal plane. The first, second and third sections of the metal surface are all isosceles trapezoidal, with an overall height H ant 93mm, length L antThe first section of the metal surface is located at the narrow end of the horn antenna 3. A vertical extension surface with a width of 10mm W3 is set at its front end and connected to the metal matching branch. The total height of the first section of the metal surface is 20mm. As the height increases, the width gradually changes from 10mm W3 to 44mm W2; the second section of the metal surface has a height H2 of 28mm, a length L2 of 10mm, and a width gradually changes from 44mm W2 to 92mm W1; the third section of the metal surface has a height H1 of 45mm, a length L1 of 76mm, and similarly, the width gradually changes from 92mm W1 to W gnd 168mm.

[0046] The horizontal metal extension panel 212 is rectangular and parallel to the metal floor. gnd Consistent, length L arm It is 38mm.

[0047] Furthermore, the vertically bent metal arm 213 is an extension of the wide end of the antenna metal panel 211, is 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.

[0048] As an example, the metal matching branch 214 is an L-shaped structure, located between the narrow end of the horn antenna surface 21 and the metal floor 31, and is used to adjust the impedance matching of the antenna; it includes a horizontal branch and a vertical branch. The horizontal branch is connected to the antenna metal panel 211, and the vertical branch is in contact with the metal back cavity 3. By adjusting the length of the horizontal branch, the impedance matching of the antenna can be adjusted. In this embodiment, the width of the vertical branch is W3 and the height is H m 6mm; the horizontal branch width is also W3, the length is L m is 50mm.

[0049] Furthermore, the width of the metal matching branch 214 is the same as the width of the smaller opening of the horn antenna surface 21 .

[0050] As an example, the metal back cavity 3 includes a metal floor 31 and two metal side walls 32 located at both ends of the metal floor 31. The metal side walls 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 side walls 32 and the horn antenna 2. In this embodiment, the metal floor 31 is located below the entire antenna, and its length L gnd 310mm, width W gnd The metal side wall 32 maintains a certain distance from the vertically bent metal arm 213, the width is consistent with the width of the metal floor 31, the height H gnd It is 99mm.

[0051] Furthermore, when the antenna operates at a low frequency, a resonant cavity is formed between the vertically bent metal arm 213 and the metal side wall 32 .

[0052] Furthermore, if Figure 1 、 3 As shown, the coaxial feed line 5 is placed above one of the metal matching branches 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 thereto.

[0053] The folded horn antenna is connected to a 50Ω coaxial feed line 5. TEM waves are excited at the narrow end of the horn antenna 2 and propagate along the horn antenna plane 2-1. When the TEM wave reaches the narrow opening of the horn antenna 2, as the conductor spacing gradually increases, the electric field begins to expand outward from the narrow end, and the magnetic field gradually expands from a closed loop. Some energy escapes from the conductors, 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 the metal floor. The vertically bent metal arm 213 connecting the horn antenna plane 21 and the metal floor 31 adjusts the antenna's reactance, thereby improving the antenna's impedance matching and achieving broadband characteristics. Because the folded horn antenna has low low-frequency gain, metal sidewalls 32 are added on either side of the vertically bent metal arm 213. When the antenna operates at low frequencies, more current is distributed along the vertically bent metal arm 213 and the metal sidewalls 32, forming a resonant cavity and enhancing low-frequency gain. At higher frequencies, a folded horn antenna may excite higher-order modes, leading to a mainlobe split in the radiation pattern and reduced forward gain. Therefore, a dielectric lens 1 is added to the larger opening of the horn notch 22 of the horn antenna 2. This adjusts the propagation path of electromagnetic waves in the dielectric. Refraction by the lens converts diverging spherical waves into parallel plane waves, compensating for phase differences and concentrating energy within a narrow beam, significantly improving antenna gain. Reducing the electric field phase difference across the horn aperture prevents mainlobe splitting at high frequencies, thereby improving forward gain at these frequencies. To minimize the impact of the lens 1 on impedance matching, its size is minimized, and it is added only directly above the horn aperture.

[0054] Figure 7 This is a voltage standing wave ratio simulation result diagram of the low-profile ultra-wideband folded horn antenna used in the 5G communication indoor distribution system of the present invention. The voltage standing wave ratio is less than 2 in the range of 0.68-5GHz, and the relative bandwidth is 152.1%. The antenna has the characteristics of wide-band coverage and good impedance matching.

[0055] Figure 8This is a gain simulation result diagram of the low-profile ultra-wideband folded horn antenna applied to the 5G communication indoor distribution system of the present invention. The gain in the working frequency band is 6-13.6dBi, the low-frequency gain is relatively stable, and it has the characteristics of high gain.

[0056] Figure 9 Middle (a) - Figure 9 Middle (b), Figure 10 Middle (a) - Figure 10 Middle (b), Figure 11 Middle (a) - Figure 11 Middle (b), Figure 12 Middle (a) - Figure 12 Middle (b), Figure 13 Middle (a) - Figure 13 Middle (b), Figure 14 Middle (a) - Figure 14 Figure (b) compares the normalized E-plane and H-plane main and cross-polarization simulation results for the present invention at 0.7 GHz, 1.5 GHz, 2 GHz, 3.3 GHz, 4.2 GHz, and 5 GHz, respectively. The horn antenna designed in this invention exhibits a symmetrical radiation pattern with no notch in the main radiation direction, demonstrating excellent directivity. The cross-polarization curves in the figure clearly demonstrate low cross-polarization levels, all less than -34 dB. This antenna exhibits stable radiation performance, making it an excellent directional antenna.

[0057] The above description is merely a preferred embodiment of the present invention and does not limit the embodiments of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall be included within the scope of protection of the claims of the present invention.

Claims

1. A low-profile ultra-wideband folded horn antenna, characterized in that: The invention comprises a dielectric lens (1), a horn antenna (2), and a metal back cavity (3) which are arranged in sequence from top to bottom, wherein the horn antenna (2) is placed in the metal back cavity (3), and the metal back cavity (3) wraps the bottom and at least two symmetrically arranged side walls of the horn antenna (2); The center of the dielectric lens (1) is located at the horizontal plane where the larger opening of the horn antenna (2) is located, and does not contact the horn antenna (2); The horn antenna (2) comprises 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, comprising 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); and the bottom end of the vertically bent metal arm (213) is in contact with the metal back cavity (3).

2. The antenna according to claim 1, characterized in that The antenna further comprises a shielding cover (4), wherein the dielectric lens (1) is embedded above the interior of the shielding cover (4), and the shielding cover (4) as a whole covers the surroundings and above the horn antenna (2) and the metal back cavity (3).

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

4. The antenna according to claim 1, wherein: The focal point of the dielectric lens (1) coincides with the center position of the smaller opening of the horn antenna (2).

5. The antenna according to claim 1, wherein: The antenna metal panel (211) is composed of a plurality of metal surfaces (2111) with different inclination angles.

6. The antenna according to claim 4, characterized in that: The metal matching branch (214) is an L-shaped structure, comprising a horizontal metal branch and a vertical metal branch, wherein the horizontal metal branch is connected to the antenna metal panel (211), and the vertical metal branch is in contact with the metal back cavity (3); by adjusting the length of the horizontal metal branch, the impedance matching of the antenna is adjusted.

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

8. The antenna according to claim 1, wherein: The metal back cavity (3) comprises a metal floor (31) and two metal side walls (32) located at both ends of the metal floor (31); the metal side walls (32) are arranged perpendicular to the metal floor (31); and there is a distance between the metal side walls (32) and the horn antenna (2).

9. The antenna according to claim 1, wherein: When the antenna operates at a low frequency, a resonant cavity is formed between the vertically bent metal arm (213) and the metal side wall (32).

10. The antenna according to claim 1, wherein: The coaxial feed line (5) is placed above one of the metal matching branches (214), the outer conductor is connected to the horn antenna surface (21) on the same side of the narrow end of the horn antenna (2), and the inner conductor extends through and to the narrow end of the horn antenna surface (21) on the opposite side of the narrow end of the horn antenna (2) and is connected thereto.

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