A low-profile base station antenna

Abstract

The present invention discloses a low-profile base station antenna, which relates to the technical field of mobile communication. The key points of its technical solution are as follows: It includes a first dielectric board, a second dielectric board, and a metal reflection cavity with an open top. A surface array is printed on the top of the first dielectric board; the surface array is composed of a plurality of circular metamaterial surfaces spaced apart on the top surface of the first dielectric board, and the plurality of metamaterial surfaces are arranged in rows and columns. The number of rows and columns of the plurality of circular metamaterial surfaces arranged in rows and columns is the same, and the radius of the metamaterial surfaces in each row and each column decreases sequentially from the middle to both ends; An antenna radiation patch with slots is printed on the bottom of the second dielectric board, and two microstrip feed lines are provided on the top. This base station antenna effectively realizes the miniaturization of the antenna and maintains the stability of the radiation pattern by adjusting the sizes of the circular metamaterial surfaces at different positions. At the same time, it can broaden the operating frequency band. This base station antenna can be used in 2G, 3G, and 4G frequency bands.

Description

Technical Field

[0001] The present invention relates to the field of mobile communication technologies, and more specifically, to a low-profile base station antenna. Background Art

[0002] With the upgrade of modern wireless communication systems, the requirements for base station antennas are getting higher and higher, and base station antennas are developing towards standards such as multi-band, wide-band, multi-polarization, and miniaturization. The overall height of a traditional dipole antenna is generally 0.25λ0 (λ0 is the wavelength of the center frequency), and such a height obviously makes it difficult to meet the requirements of modern wireless communication systems for antenna miniaturization.

[0003] There are many difficulties in reducing the height of base station antennas. After the height of the antenna is reduced, the impedance matching deteriorates, the gain is affected, and the radiation pattern deteriorates. In the existing technologies, most of them adopt loading a metamaterial surface under the antenna to solve the problem of unsatisfactory impedance matching caused by reducing the antenna height by changing the reflection characteristics of the antenna, so as to achieve the broadband and miniaturization of the antenna. However, after loading the metamaterial surface, it has an obvious impact on the radiation characteristics of the antenna, and there will also be coupling between individual metamaterial surfaces, enhancing the adverse impact on the radiation characteristics, making the stability of the antenna pattern worse.

[0004] Chinese Patent (CN105186108A) discloses a low-profile ultra-wideband dual-polarized high-frequency oscillator unit. In this invention patent, an oscillator with four petals is orthogonally inserted between a base plate and a cover plate, and four pairs of orthogonally arranged radiation arms are arranged on the cover plate. Although this high-frequency oscillator unit can effectively increase the antenna bandwidth and has the advantage of small external dimensions, its high-frequency oscillator unit operates in the frequency band range of 1695 - 2690 MHz and cannot meet the actual application requirements for covering the 2G, 3G, and 4G (1.4 - 2.7 GHz) frequency bands.

[0005] The literature "A Low-Profile Wideband and Dual-Polarized Antenna With AMCReflector" discloses a low-profile wideband dual-polarized dipole antenna loaded with AMC. Although the miniaturization of the antenna is achieved, its operating frequency band is only 1.62 - 2.84 GHz, and the high-frequency pattern is severely deformed and the cross polarization is too large, which cannot meet the requirements of modern communication systems.

[0006] The document "Low-Profile Broadband Dual-Polarization Double-Layer Metasurface Antenna for 2G / 3G / LTE Cellular Base Stations", authors: Srien Sithara Syed Nasser, Member, IEEE, and Zhi Ning Chen, Fellow, IEEE. This document discloses a low-profile broadband dual-polarization double-layer metasurface antenna for 2G / 3G / LTE cellular base stations, which has a metamaterial surface loaded below the antenna. Its operating frequency band is only 1.69 - 2.71 GHz. However, the radiation pattern of this antenna is distorted and unstable at high frequencies, and the cross polarization is greater than -20 dB, which will make the antenna may not achieve the ideal effect in actual applications.

[0007] Based on the above problems, there is an urgent need for a better way to change the radiation characteristics of the antenna and generate new resonance modes to broaden the operating bandwidth and achieve broadband miniaturization. Summary of the Invention

[0008] The purpose of the present invention is to provide a low-profile base station antenna, which overcomes the problems of poor impedance matching caused by reducing the height of existing traditional base station antennas, and it is difficult to achieve a broadband, high isolation, and high gain miniaturized base station antenna covering 2G, 3G, and 4G frequency bands. By adjusting the sizes of circular metamaterial surfaces at different positions, the miniaturization of the antenna can be effectively achieved and the stability of the radiation pattern can be maintained, while the operating frequency band can be broadened. This base station antenna can be used for 2G, 3G, and 4G frequency bands.

[0009] The above technical purpose of the present invention is achieved through the following technical solutions: A low-profile base station antenna includes a first dielectric plate, a second dielectric plate, and a metal reflection cavity with an open top. A surface set is printed on the top of the first dielectric plate; the surface set is composed of a plurality of circular metamaterial surfaces spaced apart on the top surface of the first dielectric plate, and the plurality of metamaterial surfaces are arranged in rows and columns. The number of rows and columns of the plurality of circular metamaterial surfaces arranged in rows and columns is the same, and the radii of the metamaterial surfaces in each row and each column decrease sequentially from the middle to both ends;

[0010] Four antenna radiation patches are printed on the bottom of the second dielectric plate, and L-shaped slots are provided on all four antenna radiation patches; two microstrip feed lines are provided on the top surface of the second dielectric plate, and two metal shorting posts penetrate through the second dielectric plate;

[0011] Two coaxial lines are provided at the bottom of the metal reflection cavity. The coaxial line includes an inner core and an outer conductor. The inner core is wrapped by the outer conductor. The bottom of the outer conductor is fixedly connected to the bottom of the metal reflection cavity, and the top of the outer conductor is connected to the antenna radiation patch. The tops of the two inner cores pass through the second dielectric plate and are respectively connected to the ends of two microstrip feed lines, and one of the microstrip feed lines is also connected to two metal shorting posts at the same time.

[0012] Further, the middle position of the microstrip feed line connected to the metal shorting post is located on the bottom surface of the second dielectric plate.

[0013] Further, the angle at the bend of the L-shaped groove is 90°.

[0014] Further, the antenna radiation patch is leaf-shaped.

[0015] Further, the bottom surface of the metal reflection cavity is rectangular.

[0016] Further, the height of the low-profile base station antenna is less than 0.25 times the wavelength of its operating center frequency.

[0017] Further, the end of the microstrip feed line is a two-branch feed line.

[0018] In summary, the present invention has the following beneficial effects:

[0019] 1. By loading the periodic metamaterial surface directly above the antenna, the problem of deteriorated impedance matching is overcome, and at the same time, the operating frequency band is expanded, realizing the first step of miniaturization.

[0020] 2. The radii of the metamaterial surfaces in the direction around the surface concentration part are sequentially decreased, reducing the coupling part that has an adverse effect on the radiation pattern due to surface concentration, making the radiation pattern stable.

[0021] 3. By opening an L-shaped groove on the antenna radiation patch, the current path can be changed, the impedance matching can be improved, and the degree of deteriorated impedance matching caused by reducing the height can be reduced, further realizing miniaturization.

[0022] 4. A low-profile base station antenna proposed by the present invention realizes a lower height, a wider operating bandwidth, higher isolation and gain, and maintains a stable radiation pattern, which is conducive to the realization of a broadband base station antenna array. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a three-dimensional structure diagram of a low-profile base station antenna in an embodiment of the present invention;

[0024] Figure 2 is an exploded structure diagram of a low-profile base station antenna in an embodiment of the present invention;

[0025] Figure 3 It is a top view of a low-profile base station antenna in an embodiment of the present invention after removing the metamaterial surface;

[0026] Figure 4 It is a simulated curve of return loss of a low-profile base station antenna in an embodiment of the present invention operating in the frequency band of 1.4 GHz - 2.85 GHz;

[0027] Figure 5 It is a simulated curve of isolation of a low-profile base station antenna in an embodiment of the present invention operating in the frequency band of 1.4 GHz - 2.85 GHz;

[0028] Figure 6 It is a simulated curve of gain of a low-profile base station antenna in an embodiment of the present invention operating in the frequency band of 1.4 GHz - 2.85 GHz;

[0029] Figure 7 It is a radiation pattern of a low-profile base station antenna in an embodiment of the present invention;

[0030] Figure 8 It is a comparison diagram of electric fields of structures with the same size and gradually changing structures on the metamaterial surface in an embodiment of the present invention (taking the size of the metamaterial surface at the center of the surface set at 2.7 GHz as the standard).

[0031] In the figure: 1. Dielectric plate 1; 2. Metal shorting post; 3. Dielectric plate 2; 4. Microstrip feeder; 5. Outer conductor; 6. Inner core; 7. Metal reflection cavity; 8. L-shaped groove; 9. Antenna radiation patch; 10. Metamaterial surface. Detailed implementation manners

[0032] The following further describes the present invention in detail with reference to the attached Figure 1-8 drawings.

[0033] Embodiment: A low-profile base station antenna includes a dielectric plate 1, a dielectric plate 3, and a metal reflection cavity 7 with an open top. A surface set is printed on the top of the dielectric plate 1. In this embodiment, as Figures 1-3As shown, the surface set consists of 49 circular metamaterial surfaces 10 spaced apart on the top surface of dielectric plate 1. The circular radius of the middle metamaterial surface 10 and the circular radius of the metamaterial surfaces 10 in the outermost circle are the largest. Because the coupling degree between the middle metamaterial surface 10 and the antenna radiation patch 9 is the strongest and it helps the most with the impedance matching of the antenna, it is set to the largest radius. The circular radii of the metamaterial surfaces 10 in the two outer circles are the second largest, and the circular radius of the metamaterial surfaces 10 in the outermost circle is the smallest, that is, a gradient structure. The purpose of this design is that the larger the area of the metamaterial surfaces 10 in the outermost two circles, the greater the impact on the radiation pattern. When the area is too large, the radiation pattern will deteriorate and the gain will drop significantly. Therefore, the area of the metamaterial surfaces 10 is set to gradually decrease from the inside to the outside, which can ensure good impedance matching. The electric field radiation generated by the metamaterial surfaces 10 of the same size plays a role in attenuating the electric field radiation of the entire low-profile base station antenna. If the size of the metamaterial surfaces 10 is reduced as a whole, the impedance matching will be weakened to the greatest extent. Therefore, a gradient structure of the metamaterial surface is adopted. The innovation of this gradient structure is that it can avoid the deterioration of impedance matching, further achieve miniaturization, and maintain the stability of the radiation pattern. The result is as Figure 8 shown.

[0034] Four antenna radiation patches 9 are printed on the bottom of dielectric plate 2. L-shaped slots 8 are opened on all four antenna radiation patches 9. In this embodiment, the angle at the bend of the L-shaped slot 8 is 90°. The current distribution at the edge of the antenna radiation patch is the most intensive, while the current density at the middle position of the antenna radiation patch is the smallest. Setting an L-shaped slot at the middle position can change the current distribution at the middle position and improve the impedance matching at different frequency points. Two microstrip feed lines 4 are printed on the top of dielectric plate 2 and two metal shorting posts 2 are fixedly installed. Preferably, the antenna radiation patch is leaf-shaped, and the end of the microstrip feed line is a bifurcated feed line.

[0035] In this embodiment, the ground of the metal reflection cavity 7 is a rectangular metal sheet, surrounded by four rectangular metal sheets of the same size on all sides. The metal sheets are used to reflect electromagnetic waves, and the enclosed height improves the gain of the antenna. Two holes are opened in the middle of the rectangular metal sheet for welding two coaxial cables, so that the antenna radiation patch 9 is grounded; the coaxial cable includes an inner core 6 and an outer conductor 5; the outer conductor 5 is sleeved on the surface of the inner core 6; the bottom of the outer conductor 5 is welded to the bottom surface of the metal reflection cavity 7, and the top of the outer conductor 5 is fixedly connected to the antenna radiation patch 9; the tops of the two inner cores 6 pass through the second dielectric plate 3 and are respectively connected to the ends of the two microstrip feed lines 4; the middle position of one of the microstrip feed lines 4 is located on the bottom surface of the second dielectric plate 3 and is also connected to the two metal shorting posts 2 at the same time, so as to ensure that the two microstrip feed lines 4 do not contact each other, and the microstrip feed lines 4 do not contact the antenna radiation patch 9 either. When the current is transmitted to the end of the microstrip feed line 4, it is fed to the antenna radiation patch 9 in a coupled feeding manner. The advantage of this is that the working bandwidth can be broadened.

[0036] Preferably, the height of the low-profile base station antenna is less than 0.25 times the wavelength of its operating center frequency.

[0037] As can be seen from Figure 4 , the return loss within the operating frequencies of the two ports is less than -10 dB; as can be seen from Figure 5 , the in-band isolation is greater than 30 dB, achieving a relatively high in-band isolation; Figure 6 As can be seen from Figure 7 , the in-band gain of the antenna can reach 11.4 dBi, achieving a high gain of the base station antenna;

[0038] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A low-profile base station antenna, comprising a first dielectric board (1), a second dielectric board (3), and a metal reflection cavity (7) with an opening at the top, characterized in that: A surface collection is printed on the top of the dielectric plate 1 (1); the surface collection is composed of a plurality of circular metamaterial surfaces (10) spaced apart on the top surface of the dielectric plate 1 (1), and the plurality of metamaterial surfaces (10) are arranged in rows and columns. The number of rows and columns of the plurality of circular metamaterial surfaces (10) arranged in rows and columns is the same, and the radius of the metamaterial surfaces (10) in each row and each column decreases sequentially from the middle to both ends; Four antenna radiation patches (9) are printed on the bottom of the dielectric plate 2 (3), and L-shaped slots (8) are provided on all four antenna radiation patches (9); two microstrip feed lines (4) are provided on the top surface of the dielectric plate 2 (3), and two metal shorting posts (2) are penetrated through the dielectric plate 2 (3); Two coaxial lines are provided at the bottom of the metal reflection cavity (7), and the coaxial line includes an inner core (6) and an outer conductor (5); the inner core (6) is wrapped by the outer conductor (5); the bottom of the outer conductor (5) is fixedly connected to the bottom of the metal reflection cavity (7), and the top of the outer conductor (5) is connected to the antenna radiation patch (9); the tops of the two inner cores (6) pass through the dielectric plate 2 (3) and are respectively connected to the ends of the two microstrip feed lines (4), and one of the microstrip feed lines (4) is also connected to the two metal shorting posts (2) at the same time.

2. The low-profile base station antenna according to claim 1, characterized in that: The middle position of the microstrip feed line (4) connected to the metal shorting post (2) is located on the bottom surface of the dielectric plate 2 (3).

3. The low-profile base station antenna according to claim 1, characterized in that: The angle at the bend of the L-shaped slot (8) is 90°.

4. The low-profile base station antenna according to claim 1, characterized in that: The antenna radiation patch is leaf-shaped.

5. The low-profile base station antenna according to claim 1, characterized in that: The bottom surface of the metal reflection cavity (7) is rectangular.

6. The low-profile base station antenna according to claim 1, characterized in that: The height of the low-profile base station antenna is less than 0.25 times the wavelength of its operating center frequency.

7. The low-profile base station antenna according to claim 1, characterized in that: The end of the microstrip feed line is a two-branch feed line.

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