A dual-polarized large-angle scanning planar tightly coupled array antenna

Abstract

This invention proposes a dual-polarization, large-angle scanning planar tightly coupled array antenna, comprising multiple antenna elements periodically arranged from a wide-angle impedance matching layer of a metasurface, a metallic radiator, and a metallic ground plane. The wide-angle impedance matching layer consists of two metasurfaces stacked one above the other, each containing a periodically arranged plurality of metallic rings and a square metallic patch of gradually varying size. The wide-angle impedance matching layer of this invention can mitigate the impact of instability caused by rapid changes in antenna impedance on the scanning angle, facilitating impedance matching over a wide bandwidth and providing beam scanning capability over a wide angle range. Furthermore, the metallic radiator can eliminate bandwidth degradation caused by common-mode resonance within the antenna's frequency band, effectively simplifying the antenna structure while maintaining ultra-wideband characteristics.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology and relates to a large-angle scanning tightly coupled dipole array antenna with a metal structure. Background Technology

[0002] Tightly coupled antennas are developed based on the principle of continuous current plates. By applying slot capacitive coupling between adjacent dipoles, the inductance from the ground plane can be offset, thus widening the array's bandwidth. Common tightly coupled array antennas can be categorized into tightly coupled arrays with integrated baluns, planar modular tightly coupled arrays, and tightly coupled arrays based on Vivaldi antennas. Tightly coupled arrays with integrated baluns and those based on Vivaldi antennas have higher profiles due to the need for balanced feeding via baluns. In contrast, planar modular tightly coupled array antennas use connectors for direct feeding and have lower profiles.

[0003] Common planar modular tightly coupled array antennas are typically implemented using multilayer dielectric substrates, resulting in complex designs. The dielectric substrate between the ground plane and the dipole can also induce common-mode resonance in the antenna, generating resonance at low frequencies. To remove low-frequency resonances from the desired frequency band, the dielectric constant of the dielectric substrate is generally reduced; using air as the dielectric is the optimal method. However, the connection between metal pillars and the dielectric substrate is unstable, and fabrication and assembly are cumbersome. To achieve broadband matching and wide-angle scanning in tightly coupled arrays, researchers often load multilayer dielectrics above the dipole as a wide-angle impedance matching layer. However, a pure dielectric matching layer requires a relatively thick layer, leading to a higher antenna profile and increased weight.

[0004] To overcome the impact of low-frequency resonance generated by the antenna on the bandwidth and achieve a wider scanning range, for example, the patent application with publication number CN111262021A entitled "A Tightly Coupled Low-Profile Ultra-Wideband Dual-Polarized Phased Array Antenna" discloses a tightly coupled low-profile ultra-wideband dual-polarized phased array antenna. This invention uses two symmetrical metallized short-circuit vias to connect the annular metal patch and the aluminum substrate, which can shift the common-mode resonance outside the effective bandwidth. The wide-angle matching layer composed of four layers of materials with different dielectric constants can increase the impedance bandwidth and scanning angle, but its scanning angle in the E-plane and H-plane is still relatively narrow, only ±60°, and the antenna structure is relatively complex. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and propose a dual-polarized large-angle scanning planar tightly coupled array antenna, which aims to widen the scanning angle of the antenna and simplify the antenna structure while ensuring ultra-wideband characteristics.

[0006] To achieve the above objectives, the technical solution adopted by the present invention includes a plurality of periodically arranged antenna elements. The antenna elements include a wide-angle impedance matching layer 1 of a metasurface, a radiator 2, and a metal ground plane 3, as well as two radio frequency connectors 4 fixed to the bottom of the metal ground plane 3. The wide-angle impedance matching layer 1 of the metasurface includes a first metasurface 11 and a second metasurface 12 stacked on top of each other. The first metasurface 11 includes a first dielectric substrate and a plurality of metal rings periodically arranged on its upper surface. The second metasurface 12 includes a second dielectric substrate and a plurality of square metal patches of varying sizes periodically arranged on its upper surface. The radiator 2 is made of metal.

[0007] As an optimization, the first metasurface 11 has a metal ring in which a circular metal patch structure is etched with a plurality of uniformly distributed rectangular slots.

[0008] As an optimization, the second metasurface 12 has a rectangular notch at the center of each of the four edges of the second dielectric plate.

[0009] As an optimization, the lower surface of the first metasurface 11 is provided with rectangular grooves of the same size as each rectangular notch position of the second metasurface 12.

[0010] As an optimization, the radiator 2 includes two sets of dipoles that are perpendicular and do not contact each other. Each set of dipoles includes two horizontally adjacent rhomboid dipole arms 21 and a balun-like structure 22 connected to each rhomboid dipole arm 21. A metal ridge 23 connected to each rhomboid dipole arm 21 is provided below it.

[0011] As an optimization, each set of dipoles has an asymmetrical rectangular groove on the upper surface of the connection position between the two adjacent rhombic dipole arms 21 and their respective corresponding baluns 22.

[0012] As an optimization, the two radio frequency connectors 4 are respectively fixed at the bottom of the metal floor 3 and at the positions corresponding to the balun-like 22 in the two sets of dipoles.

[0013] As an optimization, the balun 22 includes two metal plates that are rectangular in shape or whose width gradually increases from top to bottom. The lower part of one metal plate is connected to the metal floor 3, and the other metal plate is connected to the inner conductor of the radio frequency connector 4 corresponding to the position of the balun 22.

[0014] As an optimization, the dipole arm 21 is supported on the metal floor 3 by the medium support column 5.

[0015] As an optimization, the outer conductors of both radio frequency connectors 4 are connected to the metal ground plane 3.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The impedance matching layer of this invention features multiple metal rings and square metal patches of gradually varying sizes arranged periodically in the two supersurfaces stacked on top of each other. This can improve the impact of instability caused by rapid changes in antenna impedance on the scanning angle. Furthermore, the rectangular notches around the second dielectric substrate and the rectangular grooves on the lower surface of the first supersurface can reduce the equivalent dielectric constant of the dielectric substrate, which is beneficial for achieving impedance matching over a wide bandwidth. Experimental results show that the scanning angle of this invention can reach ±70° in the E-plane and H-plane, achieving beam scanning over a wider angular range.

[0018] 2. The radiator of this invention is a pure metal structure, which can eliminate the bandwidth degradation caused by common-mode resonance generated by the antenna in the frequency band. Moreover, the asymmetrical rectangular slots set on the two adjacent rhombic dipole arms in each set of dipoles can achieve good impedance matching between the balun-like and rhombic dipole arms. The metal ridge set below the dipole arm increases the coupling capacitance to better offset the influence of the inductance caused by the ground plane on the bandwidth widening at low frequencies, and at the same time provides support for the rhombic dipole arm. Compared with the prior art, the antenna structure is effectively simplified while ensuring ultra-wideband characteristics. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the antenna unit of the present invention.

[0020] Figure 2 This is a schematic diagram of the structure of the first metasurface in an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the structure of the second metasurface according to an embodiment of the present invention.

[0022] Figure 4 This is a schematic diagram showing the relative positions of a set of dipoles, their corresponding radio frequency connectors, and the metal ground plane in Embodiment 1 of the present invention.

[0023] Figure 5 This is a top view of the radiator of the present invention.

[0024] Figure 6 This is a schematic diagram of the structure of the medium support column of the present invention.

[0025] Figure 7 This is the active standing wave ratio diagram during E-plane and H-plane scanning in Embodiment 1 of the present invention. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0027] Example 1: In this example, the shape of the metal plate in the balun 22 is a structure in which the width gradually increases from top to bottom.

[0028] Reference Figure 1 The present invention includes 8*8 antenna elements with a size of 24mm*24mm*26mm arranged periodically. The antenna element includes a wide-angle impedance matching layer 1 of a metasurface, a radiator 2 and a metal ground plane 3, as well as two radio frequency connectors 4 fixed to the bottom of the metal ground plane 3. The wide-angle impedance matching layer 1 of the metasurface includes a first metasurface 11 and a second metasurface 12 stacked on top of each other.

[0029] Reference Figure 2 The first metasurface 11 includes a first dielectric substrate and multiple metal rings periodically arranged on its upper surface, with multiple uniformly distributed rectangular slots etched on the metal rings. The thickness and dielectric constant of the dielectric substrate, as well as the number and size of the periodically arranged metal rings, can be selected and optimized according to the actual frequency band. In this embodiment, polytetrafluoroethylene with a thickness of 3 mm and a dielectric constant of 2.13 is used; the number of metal rings is 4*4, and their outer diameter is 5.8 mm. Four rectangular slots are etched on each metal ring, and these four rectangular slots are distributed at 90° on the metal ring. Rectangular grooves are formed at the center of the four sides below the first metasurface 11. These rectangular grooves are the same size but adjustable. In this embodiment, the size of the rectangular grooves is 4 mm * 12 mm * 2 mm. These four rectangular grooves can reduce the equivalent dielectric constant of the dielectric substrate and can adjust the impedance matching effect to a certain extent. The loaded first metasurface 11 can stabilize the changing impedance of the ultra-wideband antenna during large-angle scanning and achieve impedance matching during wide-angle scanning.

[0030] Reference Figure 3The second metasurface 12 includes a second dielectric substrate and a plurality of square metal patches of varying sizes printed on its upper surface in a periodic arrangement. The second metasurface 12 is stacked on top of the first metasurface 11, with the second metasurface 12 located below the first metasurface 11. Similar to the first metasurface 11, the thickness and dielectric constant of the dielectric substrate of the second metasurface, as well as the number and size of the periodically arranged square metal patches, can be selected and optimized according to actual conditions. In this embodiment, the second dielectric substrate is Teflon with a thickness of 2mm and a dielectric constant of 2.1. The number of square metal patches is 6*6, with the largest metal patch being a square patch with a side length of 3.6mm. The second largest metal patch has a side length 0.9 times that of the largest metal patch, and the side lengths of the subsequent patches decrease sequentially. A rectangular notch is provided at the center of each of the four edges below the second metasurface 12. These rectangular notches are of the same size but are adjustable, and these notches correspond to the groove positions of the first metasurface 11 and have the same specifications, with a size of 4mm*12mm. These four rectangular notches reduce the equivalent dielectric constant of the dielectric substrate, which can adjust the impedance matching effect to some extent. During array antenna scanning, the antenna impedance changes with the scanning angle. When the scanning angle is large, impedance mismatch occurs, leading to a rapid deterioration of the antenna's VSWR. However, the periodically arranged square metal patches of varying sizes printed on the upper surface of the second metasurface 12 can compensate for impedance during scanning, improve the impedance mismatch of the antenna during large-angle scanning, reduce the active VSWR, and extend the scanning angle of the antenna array.

[0031] Reference Figure 4 and 5 Radiator 2 is made of pure metal and consists of two sets of perpendicular, non-contacting dipoles, forming the main radiating structure of the antenna. For example... Figure 4 As shown, each set of dipoles includes two horizontally adjacent rhombic dipole arms 21 and a balun-like structure 22 connected to each rhombic dipole arm 21. A metal ridge 23 is provided below each rhombic dipole arm and connected thereto. The pure metal radiator 2 avoids the use of a dielectric substrate during the design process, preventing common-mode resonance at low frequencies. This eliminates the need for methods to remove common-mode resonance in existing technologies, simplifying the design and avoiding energy loss caused by the use of a dielectric substrate, thus improving the antenna's radiation efficiency.

[0032] Above the connection points of two adjacent rhombic dipole arms 21 and their corresponding balun-like 22, an asymmetrical rectangular slot is provided. Viewed from the side, the height of the rhombic dipole arm 21 changes in a step-like manner. Adjusting the size of this slot allows for adjustment of the antenna's impedance matching effect. In this embodiment, the dipole arm is 11.25 mm long and 2 mm thick, and the slot height is 1.2 mm. The balun-like 22 is called a balun because its shape resembles a microstrip exponentially graded balun. The balun-like 22 consists of two metal plates, one connected to the two rhombic dipole arms 21 at the top and the other connected to the metal ground plane 3 and the inner conductor of an RF connector 4 at the bottom. Both metal plates have a gradually widening structure from top to bottom, with a thickness of 2 mm and a minimum width of 3 mm at the top. The metal plate connected to the metal ground plane is 19 mm high, and the metal plate connected to the inner conductor of the RF connector 4 is 16.8 mm high. Here, the balun-like 22 can feed the high-frequency signal from the RF connector 4 into the rhombic dipole arms 21. Each rhomboid dipole arm 21 is provided with a metal ridge 23 below it. The shape of the metal ridge 23 can be square, semi-circular, or parabolic in this embodiment. The metal ridge 23 can not only increase the coupling capacitance to offset the inductance caused by the ground at low frequencies and broaden the low-frequency bandwidth of the antenna, but also support the rhomboid dipole arm 21, making the antenna structure more stable.

[0033] The metal ground plane 3, located below the radiator 2, is made of aluminum and serves as the antenna's ground plane. Two RF connectors 4 and a dielectric support post 5 pass through the metal ground plane 3. The outer conductors of the two RF connectors 4 are connected to the metal ground plane 3 but do not pass through it. The intermediate dielectric and inner metal conductor of the RF connectors 4 pass through the metal ground plane 3, with the intermediate dielectric flush with the upper surface of the metal ground plane 3 after passing through it, and the inner metal conductor connected to a metal plate in a shorter balun-like structure 22 located above it. The RF connectors 4 can feed high-frequency current into the antenna, enabling the antenna to radiate.

[0034] Reference Figure 5 and 6 The dielectric support column 6 is made of Teflon and has a cross-shaped cylindrical structure at the top with a diameter of 4mm. For example... Figure 5 As shown, the cross structure above the medium support column 5 can be inserted into the gap between adjacent rhombic dipole arms 21, providing support and fixation for the rhombic dipole arms 21.

[0035] The working principle of this invention is as follows: a radio frequency connector feeds high-frequency current through a balun-like dipole, which then radiates through the dipole and a wide-angle impedance matching layer on the metasurface; the two sets of dipoles are placed vertically to achieve the dual-polarization radiation requirement. The use of a pure metal structure for the radiator simplifies the design and fabrication of the antenna, and the wide-angle impedance matching layer on the metasurface enables wide-angle scanning under broadband matching.

[0036] Example 2: The other structures in this example are the same as in Example 1, except that the structure of the balun 22 is adjusted. This example adopts a rectangular structure with a fixed width.

[0037] The technical effects of the present invention will be further explained below with reference to simulation results:

[0038] 1. Experimental conditions and contents:

[0039] Under periodic boundary conditions, the active VSWR of E-plane and H-plane scanning in Example 1 was simulated, and the results are as follows: Figure 7 As shown

[0040] 2. Analysis of experimental results:

[0041] Reference Figure 7 The horizontal axis of the coordinate system represents the frequency range of 0.5-6.5 GHz, and the vertical axis represents the active VSWR. From... Figure 7 As can be seen in (a), the active VSWR is below 3.5 when scanning at 0°, 30°, 60° and 70° on the E plane; Figure 7 As shown in (b), the active VSWR during H-plane scans at 0°, 30°, 60°, and 70° is also below 3.5. Figure 7 As can be seen from this embodiment, it is possible to achieve a wide-angle scanning range of ±70° in the E-plane and H-plane within 1-6GHz.

Claims

1. A planar tightly coupled array antenna with dual polarization and large-angle scanning, comprising a plurality of periodically arranged antenna elements, wherein each antenna element comprises a wide-angle impedance matching layer (1) of a metasurface, a radiator (2), and a metal ground plane (3), and two radio frequency connectors (4) fixed to the bottom of the metal ground plane (3); characterized in that, The wide-angle impedance matching layer (1) of the metasurface includes a first metasurface (11) and a second metasurface (12) stacked on top of each other; the first metasurface (11) includes a first dielectric plate and a plurality of metal rings with uniformly distributed rectangular slots etched periodically on its upper surface; the second metasurface (12) includes a second dielectric plate and a plurality of square metal patches with varying sizes periodically printed on its upper surface; the radiator (2) is made of metal and includes two sets of dipoles that are perpendicular and do not contact each other. Each set of dipoles includes two horizontally adjacent rhombic dipole arms (21) and a balun-like structure (22) connected to each rhombic dipole arm (21). A metal ridge (23) connected to each rhombic dipole arm (21) is provided below it.

2. The antenna according to claim 1, characterized in that, The second metasurface (12) has a rectangular notch at the center of each of the four edges of the second dielectric plate.

3. The antenna according to claim 2, characterized in that, The first metasurface (11) has a rectangular groove on its lower surface that corresponds to the position of each rectangular notch on the second metasurface (12) and has the same size.

4. The antenna according to claim 1, characterized in that, Each set of dipoles has an asymmetrical rectangular groove on the upper surface of the connection position between the two adjacent rhombic dipole arms (21) and their respective corresponding baluns (22).

5. The antenna according to claim 1, characterized in that, The two radio frequency connectors (4) are fixed at the bottom of the metal floor (3) at the positions corresponding to the balun-like (22) in the two sets of dipoles.

6. The antenna according to claim 5, characterized in that, The balun (22) includes two metal plates that are rectangular or gradually widen from top to bottom. The bottom of one metal plate is connected to a metal floor (3), and the other metal plate is connected to the inner conductor of the radio frequency connector (4) corresponding to the position of the balun (22).

7. The antenna according to claim 6, characterized in that, The dipole arm (21) is supported on the metal floor (3) by a medium support column (5).

8. The antenna according to claim 1, characterized in that, The outer conductors of both radio frequency connectors (4) are connected to the metal ground plane (3).

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