A compact ultra-wideband circularly polarized array antenna

Abstract

The present invention provides a compact ultra-wideband circularly polarized array antenna, comprising a first substrate, a support structure, a second substrate, a feed network, a coaxial feed unit and a plurality of cross-dipole units, wherein the first substrate and the second substrate are arranged at intervals and fixed by the support structure, the feed network is arranged on the first substrate, a grounding layer is arranged on one side of the first substrate, the cross-dipole units are connected to the feed network and the grounding layer through the coaxial feed unit, each cross-dipole unit is arranged at equal angles around an axis, the cross-dipole unit comprises a first dipole and a second dipole respectively arranged on both sides of the second substrate, the first dipole is located on the side of the second dipole close to the axis, the area of ​​the first dipole is different from the area of ​​the second dipole, and the first dipoles of adjacent cross-dipole units are located on different sides of the second substrate and at least partially overlap. The array antenna of this solution has a simple structure, occupies a small space and has a high working bandwidth, and can better meet the needs of practical applications.

Description

Technical Field

[0001] The invention belongs to the technical field of antennas, and in particular relates to a compact ultra-wideband circularly polarized array antenna. Background Art

[0002] In recent years, more and more ultra-wideband antennas have been widely used in wireless communication systems such as indoor and outdoor positioning, radar imaging, and wireless data acquisition. With the increasing popularity of multifunctional systems and miniaturized systems, the demand for compact circularly polarized ultra-wideband antennas is also increasing.

[0003] In the related art, there are compact circularly polarized ultra-wideband antennas with various structures. However, the antennas in the related art usually have problems such as complex structure, large size or narrow bandwidth, and cannot meet actual needs well. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a compact ultra-wideband circularly polarized array antenna with a simple structure, small footprint and high working bandwidth, which can better meet the needs of practical applications.

[0005] To solve the above technical problems, the present invention is implemented as follows: a compact ultra-wideband circularly polarized array antenna is provided, comprising a first substrate, a support structure, a second substrate, a feeding network, a coaxial feeding unit and a plurality of cross-dipole units, wherein the supporting structure is fixed to one side of the first substrate, the second substrate is fixed to the supporting structure and is spaced apart from the first substrate, the feeding network is arranged on the first substrate, a grounding layer is arranged on one side of the first substrate, the cross-dipole units are connected to the feeding network and the grounding layer through the coaxial feeding unit, each of the cross-dipole units is arranged at equal angles around an axis perpendicular to the second substrate, the cross-dipole units include a first dipole and a second dipole respectively arranged on both sides of the second substrate, the first dipole is located on the side of the second dipole close to the axis, the area of ​​the first dipole is different from the area of ​​the second dipole, and the first dipoles of adjacent cross-dipole units are located on different sides of the second substrate and at least partially overlap.

[0006] Furthermore, four cross-dipole units are provided, and each of the first dipole and the second dipole comprises two radiating arms connected to each other and having a phase difference of 90°, and each of the radiating arms has the same shape.

[0007] Furthermore, the radiation arm is elliptical, and the ratio of the major axis to the minor axis of the radiation arm is within 1.2-2.

[0008] Furthermore, a ratio of the major axes of the radiation arm of the first dipole and the radiation arm of the second dipole is within a range of 1.1-1.6.

[0009] Furthermore, the overlapping direction of the first dipoles of adjacent cross-dipole units is the long axis direction of the corresponding radiation arm, and the ratio of the width of the overlapping part along the long axis direction to the total length of the long axis of the corresponding radiation arm is within 0.3-0.8.

[0010] Furthermore, two radiating arms of the same dipole are connected via a three-quarter circular ring structure, and one of the radiating arms has a feeding end extending to the center of the circular ring structure.

[0011] Furthermore, the ratio of the outer diameter of the circular ring structure to the total length of the long axes of the connected radiation arms is between 0.25-0.35, and the width of the circular ring structure is 0.1-0.2 of its outer diameter.

[0012] Furthermore, the feeding network includes a 180° out-of-phase balun and two 90° baluns respectively connected to two ends of the 180° out-of-phase balun, the 90° balun includes two ports, and each of the cross-dipole units is connected to the corresponding port.

[0013] Furthermore, the dielectric constant of the first substrate is within 2.0-11, and the dielectric constant of the second substrate is within 1.5-6.0.

[0014] Furthermore, the ratios of the thickness of the first substrate and the second substrate to the wavelength of the working wave are both within a range of 0.001-0.2, and the distance between the first substrate and the second substrate is 10-100 times the thickness of the first substrate.

[0015] Compared with the prior art, the compact ultra-wideband circularly polarized array antenna of the present invention has the following beneficial effects:

[0016] The cross-dipole unit can be connected to the feeding network through a coaxial feeding unit. The feeding network has an ultra-wideband power divider and a stable phase difference performance, so that adjacent cross-dipole units have an adaptive phase difference, which can improve the axial ratio (AR) bandwidth. Since the areas of the first dipole and the second dipole are different, the axial ratio (AR) bandwidth can be further improved. The first dipoles of adjacent cross-dipole units are located on different sides of the second substrate and at least partially overlapped, so that the array antenna can obtain a stable and symmetrical radiation pattern, and the distance between the cross-dipole units in the array antenna can be shortened, thereby reducing the overall size of the array antenna. Therefore, the array antenna of this scheme has a simple structure, small space occupation and high working bandwidth, which can better meet the needs of practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is a schematic diagram of the overall structure of a compact ultra-wideband circularly polarized array antenna in an embodiment of the present invention;

[0018] Figure 2 It is a schematic diagram of the position layout of the cross-dipole unit and the second substrate of the compact ultra-wideband circularly polarized array antenna in an embodiment of the present invention;

[0019] Figure 3 is a schematic front view of a compact ultra-wideband circularly polarized array antenna in an embodiment of the present invention;

[0020] Figure 4 is a schematic diagram of the layout of a feeding network of a compact ultra-wideband circularly polarized array antenna on a first substrate in an embodiment of the present invention;

[0021] Figure 5 is a schematic diagram of simulation performance of a feeding network of a compact ultra-wideband circularly polarized array antenna in an embodiment of the present invention;

[0022] Figure 6 is a parameter table of a compact ultra-wideband circularly polarized array antenna in an embodiment of the present invention;

[0023] Figure 7 is a schematic diagram for comparing the structures of a reference antenna (a) and a cross-dipole unit (b) in an embodiment of the present invention;

[0024] Figure 8 Schematic diagram of S11 performance of a reference antenna (dashed line) and a cross-dipole unit (solid line) in an embodiment of the present invention;

[0025] Fig. 9 Schematic diagram of AR performance of a reference antenna (dashed line) and a cross-dipole unit (solid line) in an embodiment of the present invention;

[0026] Fig.10 is a physical schematic diagram of a compact ultra-wideband circularly polarized array antenna for testing in an embodiment of the present invention;

[0027] Fig.11 1 is a schematic diagram of the simulated (solid line) and measured (dashed line) performance of S11 of the compact ultra-wideband circularly polarized array antenna in an embodiment of the present invention;

[0028] Fig.12 1 is a schematic diagram of simulated (solid line) and measured (dashed line) performance of AR and gain of a compact ultra-wideband circularly polarized array antenna in an embodiment of the present invention;

[0029] Fig.13 It is a schematic diagram of simulation (solid line) and actual measurement (dashed line) of the radiation pattern of the compact ultra-wideband circularly polarized array antenna in an embodiment of the present invention; c: 2.5 GHz, d: 3.5 GHz, e: 4.5 GHz, f: 5.5 GHz.

[0030] In the accompanying drawings, the various reference numerals represent: 1. first substrate; 11. ground layer; 2. support structure; 3. second substrate; 4. feeding network; 41. 180° out-of-phase balun; 42. 90° balun; 5. coaxial feeding unit; 6. cross dipole unit; 61. first dipole; 62. second dipole; 60. ring structure. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] Example:

[0033] In this embodiment, combined with Figure 1-6 The compact ultra-wideband circularly polarized array antenna includes a first substrate 1, a support structure 2, a second substrate 3, a feeding network 4, a coaxial feeding unit 5 and a plurality of cross-dipole units 6, wherein the supporting structure 2 is fixed to one side of the first substrate 1, the second substrate 3 is fixed to the supporting structure 2 and is spaced apart from the first substrate 1, the feeding network 4 is arranged on the first substrate 1, a grounding layer 11 is arranged on one side of the first substrate 1, the cross-dipole units 6 are connected to the feeding network 4 and the grounding layer 11 through the coaxial feeding unit 5, each cross-dipole unit 6 is arranged at equal angles around an axis perpendicular to the second substrate 3, the cross-dipole unit 6 includes a first dipole 61 and a second dipole 62 respectively arranged on both sides of the second substrate 3, the first dipole 61 is located on the side of the second dipole 62 close to the axis, the area of ​​the first dipole 61 is different from the area of ​​the second dipole 62, and the first dipoles 61 of adjacent cross-dipole units 6 are located on different sides of the second substrate 3 and at least partially overlap.

[0034] The cross-dipole unit 6 can be connected to the feed network 4 through the coaxial feed unit 5. The feed network 4 has an ultra-wideband power divider and a stable phase difference performance, so that the adjacent cross-dipole units 6 have an adaptive phase difference, which can improve the axial ratio (AR) bandwidth. Since the areas of the first dipole 61 and the second dipole 62 are different, the axial ratio (AR) bandwidth can be further improved. The first dipoles 61 of the adjacent cross-dipole units 6 are located on different sides of the second substrate 3 and at least partially overlapped, so that the array antenna can obtain a stable and symmetrical radiation pattern, and the distance between the cross-dipole units 6 in the array antenna can be shortened, thereby reducing the overall size of the array antenna. Therefore, the array antenna of this scheme has a simple structure, small space occupation and high working bandwidth, which can better meet the needs of practical applications.

[0035] There are four cross-dipole units 6, and the first dipole 61 and the second dipole 62 each include two radiating arms connected to each other and having a phase difference of 90°, and the shapes of the radiating arms are the same. Specifically, the adjacent radiating arms of the same cross-dipole each have a phase difference of 90°, the shapes and sizes of the radiating arms of each first dipole 61 are the same, and the shapes and sizes of the radiating arms of each second dipole 62 are the same, so that the positional relationship of the four cross-dipoles is centrally symmetrical, and the first dipole 61 and the second dipole 62 of adjacent cross-dipoles are located on different sides of the second substrate 3, so that they can partially overlap in the thickness direction of the second substrate 3. It should be understood that the radiating arms of the cross-dipole can be elliptical, rectangular, rhombus, pentagonal, hexagonal, etc., and the specific shape can be set according to actual needs, as long as the area of ​​the first dipole 61 is different from the area of ​​the second dipole 62, and the first dipoles 61 of adjacent cross-dipoles partially overlap.

[0036] In this embodiment, the radiating arm is elliptical, the ratio of the major axis to the minor axis of the radiating arm is within 1.2-2, and the ratio of the major axis of the radiating arm of the first dipole 61 to the radiating arm of the second dipole 62 is within 1.1-1.6. Specifically, the major axis radius r3 of the radiating arm of the first dipole 61 is 13 mm, and the minor axis radius r4 is 10 mm, and the major axis radius r5 of the radiating arm of the second dipole 62 is 11 mm, and the minor axis radius r6 is 8.5 mm. In some embodiments, the ratio of the major axis to the minor axis of the radiating arm may be 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, etc., the ratio of the major axes of the radiating arm of the first dipole 61 to the radiating arm of the second dipole 62 may be 1.2, 1.3, 1.4, 1.5, etc., the major axis radius of the radiating arm of the first dipole 61 may be 11 mm, 12 mm, 14 mm, 15 mm, 16 mm, etc., and the minor axis radius of the radiating arm of the first dipole 61, the major axis radius and the minor axis radius of the radiating arm of the second dipole 62 may be adjusted accordingly with reference to the above parameter ratios.

[0037] The overlapping direction of the first dipoles 61 of the adjacent cross-dipole units 6 is the long axis direction of the corresponding radiation arm, and the ratio of the width of the overlapping portion along the long axis direction to the total long axis length of the corresponding radiation arm (i.e., twice the long axis radius) is within 0.3-0.8. Specifically, in the present embodiment, the width d of the overlapping portion is 13.4 mm. In some embodiments, the ratio of the width of the overlapping portion along the long axis direction to the total long axis length of the corresponding radiation arm can be 0.4, 0.5, 0.6, 0.7, etc., and the specific overlapping width can be adaptively adjusted according to the ratio range and the size of the radiation arm of the first dipole 61. When the radiation arm is of other shapes, the ratio of the area of ​​the overlapping portion to the area of ​​the corresponding radiation arm can be set with reference to the corresponding ratio in the aforementioned elliptical shape.

[0038] The two radiating arms of the same dipole are connected by a three-quarter circular ring structure 60, and one of the radiating arms has a feeding end extending to the center of the circular ring structure 60; the ratio of the outer diameter of the circular ring structure 60 to the total length of the long axis of the connected radiating arms is between 0.25-0.35, and the width of the circular ring structure 60 is 0.1-0.2 of its outer diameter. Specifically, in this embodiment, the outer diameter r1 of the circular ring structure 60 connecting the two radiating arms of the first dipole 61 is 4.2 mm, the width w1 is 1.5 mm, the width w3 of the feeding end of the first dipole 61 is 3.5 mm, the outer diameter r2 of the circular ring structure 60 connecting the two radiating arms of the second dipole 62 is 3.5 mm, the width w2 is 1 mm, and the width w4 of the feeding end of the second dipole 62 is 2.5 mm. In some embodiments, the ratio of the outer diameter of the ring structure 60 to the total length of the major axes of the connected radiating arms may be 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, and so on.

[0039] In this embodiment, the feeding network 4 includes a 180° out-of-phase balun 41 and two 90° baluns 42 respectively connected to the two ends of the 180° out-of-phase balun 41, the 90° balun 42 includes two ports, and each cross-dipole unit 6 is connected to the corresponding port. Specifically, the feeding network 4 includes four ports located at the corner positions of a square, and the phase difference of the ports at adjacent corner positions is maintained at about 90° within a bandwidth of 1.82 GHz to 6.21 GHz. The unbalanced amount of the insertion loss of the feeding network 4 is less than 1.5 db, and the four cross-dipole units 6 are respectively connected to the four ports through the coaxial feeding unit 5.

[0040] The dielectric constant of the first substrate 1 is within 2.0-11, and the dielectric constant of the second substrate 3 is within 1.5-6.0; the ratio of the thickness of the first substrate 1 and the second substrate 3 to the wavelength of the working wave is within 0.001-0.2, and the distance between the first substrate 1 and the second substrate 3 is 10-100 times the thickness of the first substrate 1, preferably 20-60 times. Specifically, in this embodiment, the support structure 2 is four plastic support columns, and the two ends of the plastic support columns are respectively fixed to the first substrate 1 and the second substrate 3, the first substrate 1 and the second substrate 3 are parallel to each other, the first substrate 1 is a square plate with a width of wg=140mm and a thickness of h2=0.508mm, the dielectric constant of the first substrate 1 is ε2=3.55, the second substrate 3 is a square plate with a width of ws=100mm and a thickness of h1=0.508mm, and the distance between the first substrate 1 and the second substrate 3 is h=22mm.

[0041] The compact ultra-wideband circularly polarized array antenna of this scheme has a high axial ratio (AR) bandwidth. The measured impedance bandwidths at S11 <-10dB and 3dB AR bandwidth are 106.5% (3.28:1, 1.9-6.23GHz) and 114.5% (3.68:1, 1.71-6.29GHz), respectively. At 4.5GHz, the peak gain is 13.5dBic, and the overall size of the array antenna is only 0.88λ*0.88λ*0.14λ (λ refers to the wavelength of the lowest operating frequency in free space).

[0042] Combination Figure 7-13 , the design and analysis of the array antenna of this scheme are as follows:

[0043] like Figure 7-9 As shown, compared with the cross-dipole unit 6 of the symmetric elliptical arm (reference antenna), half of the size of the cross-dipole unit 6 of the asymmetric elliptical arm of the present application is slightly larger than the corresponding part of the reference antenna, and the other half of the size of the cross-dipole unit 6 of the asymmetric elliptical arm of the present application is slightly smaller than the corresponding part of the reference antenna. In this way, the impedance bandwidth of the reference antenna and the antenna of the present application can be almost the same, while the 3db AR bandwidth of the antenna unit of the present application is much wider. Therefore, a suitable working bandwidth can be obtained by appropriately selecting the size ratio of the asymmetric elliptical arm.

[0044] like Figure 10-13 As shown, the proposed compact ultra-wideband circularly polarized array antenna was fabricated and tested in this application. The measured impedance bandwidth of S11<-10dB is about 104.4% (3.88:1, 1.96-6.24GHz), which is in good agreement with the simulation results. The measured 3db AR bandwidth can cover the frequency range of 1.75 to 6.19ghz, reaching 111.8% (3.53:1), which is slightly different from the simulation results. In addition, the measured gain is positive over the operating bandwidth, with slight fluctuations compared to the simulated gain, and the peak gain is 13.2dbic at 4.25ghz; a stable left-hand circularly polarized radiation pattern can be generated in both the xoz plane and the yoz plane. The results show that the array antenna of this application has a high operating bandwidth and a small overall size, with an impedance bandwidth of 104.4%, an AR bandwidth of 111.8%, and good comprehensive performance. Its good performance makes it have potential application prospects in many UWB applications.

[0045] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A compact ultra-wideband circularly polarized array antenna, characterized in that: The invention comprises a first substrate (1), a support structure (2), a second substrate (3), a feed network (4), a coaxial feed unit (5) and a plurality of cross-dipole units (6), wherein the support structure (2) is fixed to one side of the first substrate (1), the second substrate (3) is fixed to the support structure (2) and is spaced apart from the first substrate (1), the feed network (4) is arranged on the first substrate (1), a grounding layer (11) is arranged on one side of the first substrate (1), and the cross-dipole units (6) are connected to the feed network (4) and the grounding layer (11) through the coaxial feed unit (5). 11), each of the cross-dipole units (6) is arranged at equal angles around an axis perpendicular to the second substrate (3), the cross-dipole unit (6) comprises a first dipole (61) and a second dipole (62) respectively arranged on two sides of the second substrate (3), the first dipole (61) is located on the side of the second dipole (62) close to the axis, the area of ​​the first dipole (61) is different from the area of ​​the second dipole (62), and the first dipoles (61) of adjacent cross-dipole units (6) are located on different sides of the second substrate (3) and at least partially overlap; Four cross-dipole units (6) are provided, and each of the first dipole (61) and the second dipole (62) comprises two mutually connected radiation arms with a phase difference of 90°, and each of the radiation arms has the same shape; The radiation arm is elliptical, and the ratio of the major axis to the minor axis of the radiation arm is within 1.2-2; The ratio of the major axes of the radiation arm of the first dipole (61) and the radiation arm of the second dipole (62) is within a range of 1.1-1.

6.

2. The compact ultra-wideband circularly polarized array antenna according to claim 1, characterized in that: The overlapping direction of the first dipoles (61) of adjacent cross-dipole units (6) is the long axis direction of the corresponding radiation arm, and the ratio of the width of the overlapping part along the long axis direction to the total length of the long axis of the corresponding radiation arm is within 0.3-0.

8.

3. The compact ultra-wideband circularly polarized array antenna according to claim 1, characterized in that: Two radiating arms of the same dipole are connected via a three-quarter circular ring structure (60), and one of the radiating arms has a feeding end extending to the center of the circular ring structure (60).

4. The compact ultra-wideband circularly polarized array antenna according to any one of claims 1 to 3, characterized in that: The feeding network (4) comprises a 180° out-of-phase balun (41) and two 90° baluns (42) respectively connected to two ends of the 180° out-of-phase balun (41), the 90° balun (42) comprising two ports, and each of the cross-dipole units (6) is connected to the corresponding port.

5. The compact ultra-wideband circularly polarized array antenna according to claim 4, characterized in that: The dielectric constant of the first substrate (1) is within the range of 2.0-11, and the dielectric constant of the second substrate (3) is within the range of 1.5-6.

0.

6. The compact ultra-wideband circularly polarized array antenna according to claim 5, characterized in that: The ratios of the thickness of the first substrate (1) and the second substrate (3) to the wavelength of the working wave are both within a range of 0.001-0.2, and the distance between the first substrate (1) and the second substrate (3) is 10-100 times the thickness of the first substrate (1).

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