Dual-polarization wide-angle scanning planar tight coupling array antenna

Abstract

The invention provides a dual-polarization wide-angle scanning planar tight coupling array antenna which comprises a plurality of antenna units which are periodically arranged and are composed of metasurface wide-angle impedance matching layers, metal radiators and metal floors. The wide-angle impedance matching layer is composed of two metasurfaces which are stacked up and down and respectively comprise a plurality of metal rings arranged periodically and square metal patches with gradually changing sizes. The wide-angle impedance matching layer of the metasurface can improve the influence of instability caused by rapid change of antenna impedance on a scanning angle, is beneficial for realizing impedance matching in a broadband, and has a relatively wide-angle-domain beam scanning capability; and the radiating body made of the metal material can eliminate bandwidth deterioration caused by common-mode resonance generated by the antenna in a frequency band range, so that the structure of the antenna is effectively simplified on the premise of ensuring the ultra-wideband characteristic.

Description

Technical Field

[0001] The present invention belongs to the technical field of antennas and relates to a large-angle scanning tightly coupled dipole array antenna with a metal structure. Background Art

[0002] Tightly coupled antennas are developed based on the principle of continuous current sheets. By loading slot capacitance coupling between adjacent dipoles, the inductance brought by the ground plane can be canceled, and the bandwidth of the array can be broadened. Common tightly coupled array antennas can be divided into tightly coupled arrays with integrated baluns, planar modular tightly coupled arrays, and tightly coupled arrays based on Vivaldi antennas. Both the tightly coupled arrays with integrated baluns and the tightly coupled arrays based on Vivaldi antennas have a relatively high profile height because they need to load baluns to achieve balanced feeding. Relatively speaking, the planar modular tightly coupled array antenna uses connectors for direct feeding and has a lower profile.

[0003] Common planar modular tightly coupled array antennas are usually realized by using multi-layer dielectric substrates, and the design is relatively complex. The dielectric substrate between the ground plane and the dipole will also cause common-mode resonance of the antenna, generating resonance at the low frequency of the antenna. In order to remove the low-frequency resonance from the required frequency band range, generally, the dielectric constant of the dielectric substrate is reduced, and using air as the dielectric is the optimal method. However, the connection between the metal posts and the dielectric substrate is unstable, and the processing and assembly are relatively troublesome. In order to achieve broadband matching and large-angle scanning of the tightly coupled array, scholars often load multi-layer dielectrics above the dipoles as wide-angle impedance matching layers. However, the pure dielectric matching layer requires a relatively thick thickness, which will increase the profile height of the antenna and increase the weight of the antenna.

[0004] In order to overcome the influence of the low-frequency resonance generated by the antenna on the bandwidth and achieve scanning in a relatively wide angular domain, for example, a patent application with the application publication number CN111262021A and the name "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. The invention connects a circular metal patch and an aluminum substrate by using two symmetric metallized shorting vias, which can move the common-mode resonance outside the effective bandwidth; the wide-angle matching layer composed of four materials with different dielectric constants can increase the impedance bandwidth and the scanning angle, but its scanning angles in the E-plane and H-plane are still relatively narrow, only ±60°, and the structure of the antenna is relatively complex. Summary of the Invention

[0005] The object of the present invention is to overcome the defects existing in the above-mentioned prior art and propose a planar tightly coupled array antenna with dual-polarization and large-angle scanning, aiming to broaden the scanning angle of the antenna and simplify the structure of the antenna on the premise of ensuring the ultra-wideband characteristics.

[0006] To achieve the above object, the technical solution adopted by the present invention includes a plurality of antenna units arranged periodically. The antenna unit includes a wide-angle impedance matching layer 1 of a metasurface, a radiator 2, a metal floor 3, and two radio frequency connectors 4 fixed to the bottom of the metal floor 3. The wide-angle impedance matching layer 1 of the metasurface includes a first metasurface 11 and a second metasurface 12 stacked up and down. The first metasurface 11 includes a first dielectric plate and a plurality of metal rings printed periodically on its upper surface. The second metasurface 12 includes a second dielectric plate and a plurality of square metal patches with gradually changing sizes printed periodically on its upper surface. The radiator 2 is made of metal material.

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

[0008] As an optimization, in the second metasurface 12, a rectangular notch is provided at the middle position of each edge of the second dielectric plate.

[0009] As an optimization, in the first metasurface 11, a rectangular groove corresponding to the position of each rectangular notch of the second metasurface 12 and having the same specification is provided on its lower surface.

[0010] As an optimization, the radiator 2 includes two sets of dipoles that are perpendicular and non-contact. Each set of dipoles includes two diamond dipole arms 21 placed horizontally adjacent to each other and a balun-like structure 22 corresponding to and connected to each diamond dipole arm 21, and a metal ridge 23 connected to each diamond dipole arm 21 is provided below.

[0011] As an optimization, in each set of dipoles, an asymmetric rectangular sunk groove is provided on the upper surface at the connection position of two adjacent diamond dipole arms 21 and their respective corresponding balun-like structures 22.

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

[0013] As an optimization, the balun-like structure 22 includes two metal plates in the shape of a rectangle or with a gradually increasing width from top to bottom. One of the metal plates is connected to the metal floor 3 below, and the other metal plate is connected to the inner conductor of the radio frequency connector 4 corresponding to the position of the balun-like structure 22.

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

[0015] As an optimization, for the two radio frequency connectors 4, their outer conductors are both connected to the metal floor 3.

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

[0017] 1. In the impedance matching layer of the present invention, the multiple metal rings arranged periodically and the square metal patches with gradually changing sizes in the two super-surfaces stacked up and down can improve the influence of the instability caused by the rapid change of the antenna impedance on the scanning angle. Moreover, the rectangular notches provided around the second dielectric plate and the rectangular grooves provided on the lower surface of the first super-surface can reduce the equivalent dielectric constant of the dielectric plate, which is beneficial to achieving impedance matching within a wide bandwidth. The experimental results show that the scanning angles of the present invention in the E-plane and H-plane can reach ±70°, realizing beam scanning in a relatively wide angular range.

[0018] 2. The radiator of the present invention is a pure metal structure, which can eliminate the bandwidth deterioration caused by the common-mode resonance generated by the antenna within the frequency band. Moreover, the asymmetric rectangular sinks provided on the adjacent two diamond dipole arms in each group of dipoles can achieve good impedance matching between the quasi-balun and the diamond dipole arms. The metal ridge provided under the dipole arms, on the one hand, increases the coupling capacitance to better offset the influence of the inductance caused by the ground plane at low frequencies on the bandwidth broadening, and at the same time plays a supporting role for the diamond dipole arms. Compared with the prior art, the structure of the antenna is effectively simplified on the premise of ensuring the ultra-wideband characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0020] Figure 2 It is a schematic structural diagram of the first super-surface of the embodiment of the present invention.

[0021] Figure 3 It is a schematic structural diagram of the second super-surface of the embodiment of the present invention.

[0022] Figure 4 It is a schematic diagram of the mutual positions of a group of dipoles, the corresponding RF connector and the metal ground plane in Embodiment 1 of the present invention.

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

[0024] Figure 6 It is a schematic structural diagram of the dielectric support column of the present invention.

[0025] Figure 7 It is an active standing wave ratio diagram when scanning in the E-plane and H-plane in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

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

[0027] Embodiment 1. In this embodiment, the shape of the metal plate in the quasi-balun 22 is a structure with a gradually increasing width from top to bottom.

[0028] Referring to Figure 1 , the present invention includes 8×8 antenna elements arranged periodically with a size of 24 mm×24 mm×26 mm. The antenna element includes a wide-angle impedance matching layer 1 of a metasurface, a radiator 2, a metal floor 3, and two radio frequency connectors 4 fixed to the bottom of the metal floor 3; the wide-angle impedance matching layer 1 of the metasurface includes a first metasurface 11 and a second metasurface 12 stacked up and down.

[0029] Referring to Figure 2 , the first metasurface 11 includes a first dielectric plate and a plurality of metal rings printed periodically on its upper surface, and a plurality of uniformly distributed rectangular slots are etched on the metal rings. The thickness and dielectric constant of the dielectric plate, 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 its 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 opened at the middle positions around the periphery of the first metasurface 11, and the sizes of these rectangular grooves are the same but adjustable. In this embodiment, the size of the rectangular notch is: 4 mm×12 mm×2 mm. These four rectangular grooves can reduce the equivalent dielectric constant of the dielectric plate and can adjust the impedance matching effect to a certain extent. The loaded first metasurface 11 can stabilize the impedance change during the large-angle scanning of the ultra-wideband antenna and achieve impedance matching during wide-angle scanning.

[0030] Referring to Figure 3, the second metasurface 12 includes a second dielectric plate and a plurality of square metal patches with gradually changing sizes periodically arranged on its upper surface. The second metasurface 12 and the first metasurface 11 are stacked vertically, and the second metasurface 12 is located below the first metasurface 11. Similar to the first metasurface 11, the thickness and dielectric constant of the second metasurface dielectric plate, as well as the number and size of the periodically arranged square metal patches, can also be selected and optimized according to the actual situation. In this embodiment, the second dielectric plate used is Teflon with a thickness of 2 mm and a dielectric constant of 2.1. The number of square metal patches is 6 * 6. The largest metal patch is a square patch with a side length of 3.6 mm, and the side length of the second largest metal patch is 0.9 times that of the largest metal patch. Subsequently, the side lengths become shorter in sequence. At the middle positions of the four peripheral edges below the second metasurface 12, a rectangular notch is provided respectively. These rectangular notches have the same size but are adjustable, and these notches correspond to the groove positions of the first metasurface 11 and have the same specifications. Their size is: 4 mm * 12 mm. These four rectangular notches can reduce the equivalent dielectric constant of the dielectric plate and can, to a certain extent, adjust the impedance matching effect. When the array antenna scans, the impedance of the antenna will change with the scanning angle. When the scanning angle is relatively large, impedance "mismatch" will occur, which will further lead to a rapid deterioration of the antenna's standing wave ratio. However, the periodically arranged square metal patches with gradually changing sizes printed on the upper surface of the second metasurface 12 can compensate for the impedance during scanning, improve the impedance "mismatch" of the antenna during large-angle scanning, reduce the active standing wave ratio, and expand the scanning angle of the antenna array.

[0031] Referring to Figure 4 and 5 , the radiator 2 is made of pure metal material and consists of two sets of dipoles that are vertical and non-contact, which is the main radiation structure of the antenna. As Figure 4 shown, each set of dipoles includes two diamond dipole arms 21 placed horizontally adjacent to each other and a balun-like structure 22 corresponding to and connected to each diamond dipole arm 21, and a metal ridge 23 connected to the lower part of each diamond dipole arm is provided. The radiator 2 made of pure metal material does not use a dielectric plate during the design process, which avoids the generation of common-mode resonance of the antenna at low frequencies, eliminates the means of removing common-mode resonance in the prior art, makes the design simpler, and at the same time avoids the energy loss caused by using a dielectric plate and improves the radiation efficiency of the antenna.

[0032] An asymmetric rectangular sunk groove is provided above the connection positions of two adjacent diamond dipole arms 21 and their respective corresponding balun-like structures 22. When viewed from the side of the diamond dipole arm 21, its height changes in a step-like manner. By adjusting the size of this sunk groove, the impedance matching effect of the antenna can be adjusted. In this embodiment, the length of the dipole arm is 11.25 mm, the thickness is 2 mm, and the height of the sunk groove is 1.2 mm. Since the shape of the balun-like structure 22 is similar to that of a microstrip exponential tapered balun, it is called a balun-like structure. The balun-like structure 22 is composed of two metal plates that are respectively connected to the two diamond dipole arms 21 at the top and connected to the metal floor 3 and the inner conductor of a radio frequency connector 4 at the bottom. The metal plates are both structured with a gradually increasing width from top to bottom, with a thickness of 2 mm, a width of 3 mm at the narrowest part at the top, a height of 19 mm for the metal plate connected to the metal floor, and a height of 16.8 mm for the metal plate connected to the inner conductor of the radio frequency connector 4. Here, the balun-like structure 22 can feed the high-frequency signal of the radio frequency connector 4 into the diamond dipole arm 21. A metal ridge 23 is provided below each diamond dipole arm 21. The shape of the metal ridge 23 can be square or semi-circular, and in this embodiment, it is in the shape of a parabola. This metal ridge 23 can not only increase the coupling capacitance to offset the inductance caused by the floor at low frequencies to broaden the low-frequency bandwidth of the antenna, but also play a supporting role for the diamond dipole arm 21, making the antenna structure more stable.

[0033] The metal floor 3 is located below the radiator 2 and is made of aluminum, serving as the ground plane of the antenna. Two radio frequency connectors 4 and dielectric support columns 5 pass through the metal floor 3. The outer conductors of the two radio frequency connectors 4 are connected to the metal floor 3 but do not pass through it. The intermediate dielectric and the metal inner conductor of the radio frequency connector 4 pass through the metal floor 3. The intermediate dielectric is flush with the upper surface of the metal floor 3 after passing through it, and the metal inner conductor is connected to one of the metal sheets in the shorter balun-like structure 22 above it. The radio frequency connector 4 can feed high-frequency current into the antenna to realize the radiation function of the antenna.

[0034] Refer to 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 4 mm. As Figure 5 shown, the cross-shaped structure above the dielectric support column 5 can be inserted into the gap between adjacent diamond dipole arms 21 to support and fix the diamond dipole arms 21.

[0035] The working principle of the present invention is as follows: The radio frequency connector feeds high-frequency current through a balun-like dipole, and then radiates through the dipole and the wide-angle impedance matching layer of the metasurface; the perpendicular placement of the two groups of dipoles realizes the radiation requirements of dual polarization. The radiator uses a pure metal structure, which simplifies the design and processing of the antenna, and realizes wide-angle scanning in the wide-angle domain under broadband matching of the antenna by loading the wide-angle impedance matching layer of the metasurface.

[0036] Example 2, the other structures of this example are the same as those of Example 1, only the structure of the balun-like 22 is adjusted, and a rectangular structure with a constant width is adopted in this example.

[0037] The technical effects of the present invention will be further described below in conjunction with the simulation results:

[0038] 1. Experimental conditions and content:

[0039] Under periodic boundary conditions, the active voltage standing wave ratio during E-plane and H-plane scanning of Example 1 is simulated, and the results are as Figure 7 shown

[0040] 2. Analysis of experimental results:

[0041] Referring to Figure 7 , the horizontal axis of the coordinate is the frequency from 0.5 - 6.5 GHz, and the vertical axis is the active voltage standing wave ratio. It can be seen from Figure 7 (a) that the active voltage standing wave ratios during E-plane scanning at 0°, 30°, 60° and 70° are all lower than 3.5; it can be seen from Figure 7 (b) that the active voltage standing wave ratios during H-plane scanning at 0°, 30°, 60° and 70° are also all lower than 3.5. It can be seen from Figure 7 that this example can achieve ±70° wide-angle scanning in the E-plane and H-plane within 1 - 6 GHz.

Claims

1. A dual-polarization large-angle scanning planar tightly coupled array antenna, comprising a plurality of periodically arranged antenna units, wherein the antenna units comprise a wide-angle impedance matching layer (1) of a metasurface, a radiator (2) and a metal floor (3), and two radio frequency connectors (4) fixed at the bottom of the metal floor (3); characterized in that: The wide-angle impedance matching layer (1) of the metasurface comprises a first metasurface (11) and a second metasurface (12) stacked up and down; the first metasurface (11) comprises a first dielectric plate and a plurality of metal rings printed on its upper surface and arranged periodically; the second metasurface (12) comprises a second dielectric plate and a plurality of square metal patches with gradually varying sizes printed on its upper surface and arranged periodically; and the radiator (2) is made of metal.

2. The antenna according to claim 1, characterized in that The metal ring in the first super surface (11) is a circular metal patch structure, on which a plurality of evenly distributed rectangular gaps are etched.

3. The antenna according to claim 1, characterized in that The second super surface (12) has a rectangular notch disposed at the middle position of the edges of the second dielectric plate on each side.

4. The antenna according to claim 3, characterized in that: The first super surface (11) is provided with a rectangular groove on its lower surface, which corresponds to the position of each rectangular notch of the second super surface (12) and has the same specifications.

5. The antenna according to claim 1, characterized in that: The radiator (2) comprises two groups of dipoles which are vertical and non-contacting, each group of dipoles comprises two rhombus-shaped dipole arms (21) which are placed adjacent to each other horizontally and a quasi-balun (22) which is connected to each rhombus-shaped dipole arm (21), and a metal ridge (23) which is connected to each rhombus-shaped dipole arm (21) is arranged below each rhombus-shaped dipole arm (21).

6. The antenna according to claim 5, characterized in that In each group of dipoles, an asymmetric rectangular sink groove is provided on the upper surface of the connection position between the two adjacent rhombus-shaped dipole arms (21) contained therein and the corresponding quasi-balun (22) thereof.

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

8. The antenna according to claim 7, characterized in that: The quasi-balun (22) comprises two metal plates which are rectangular in shape or gradually widen from top to bottom, wherein the bottom of one of the metal plates 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 quasi-balun (22).

9. The antenna according to claim 8, characterized in that The dipole arm (21) is supported on the metal floor (3) via a dielectric support column (5).

10. The antenna according to claim 1, characterized in that: The outer conductors of the two radio frequency connectors (4) are both connected to the metal floor (3).

Images