Broadband circularly polarized cross dipole antenna

Abstract

The invention relates to a broadband circularly polarized cross dipole antenna. The broadband circularly polarized cross dipole antenna comprises a first dielectric plate, a metal floor, an antenna radiator and a feed coaxial line, the antenna radiator comprises a first dipole arm, a second dipole arm, a third dipole arm and a fourth dipole arm, the first dipole arm and the second dipole arm are arranged on the upper surface of the first dielectric plate, and the feed coaxial line is arranged on the upper surface of the first dielectric plate. The third dipole arm and the fourth dipole arm are arranged on the lower surface of the first dielectric plate, and the first dipole arm, the second dipole arm, the third dipole arm and the fourth dipole arm take the center of the first dielectric plate as a fixed point and are respectively in rotational symmetry at a rotation angle of 90 degrees. The broadband circularly-polarized cross dipole antenna has a wide impedance matching frequency band, three circularly-polarized modes are combined to form broadband circularly-polarized radiation by optimally designing the dipole arms, and meanwhile, the impedance matching bandwidth is further expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communications, and in particular to a broadband circularly polarized cross-dipole antenna. Background Art

[0002] In modern communications, antennas with wide axial ratio bandwidth, impedance matching bandwidth, and high gain are favored in fields such as satellite communications, wireless local area networks, and Bluetooth technology. Because different communication systems require different operating frequency bands, wideband antennas that can simultaneously meet multiple frequency requirements have become a research focus. Wideband circular polarization has a strong ability to reduce polarization mismatch and improve immunity to multipath interference. Therefore, wideband circularly polarized cross-dipole antennas have a good overall performance and are attracting increasing attention.

[0003] In order to expand the working bandwidth, dipole antennas usually adopt methods such as cutting corners, adding parasitics and branches. Chinese patent document CN103474765B proposes a circularly polarized cross-dipole antenna and a preparation method. The invention uses a coaxial line to feed four square radiators, and two pairs of square radiators form a cross dipole. In order to produce a 90° phase shift between the two pairs of dipoles to form circularly polarized radiation, a circular phase-shifted microstrip line is used. The frequency range of the antenna reflection coefficient below -10dB is 2.02-3.19GHz, and the impedance matching bandwidth is 47.7%. The 3dB axial ratio frequency range of the antenna is 2.30-3.15GHz, and the corresponding axial ratio bandwidth is 34.7%. The maximum gain of the antenna is 7.05dBi, and the average gain in the range of 2.30-3.15GHz is 6.4dBi. Chinese patent document CN 117154395 A proposes a broadband circularly polarized cross-dipole antenna. The main radiators are two pairs of orthogonal, prismatic dipoles. A 90° phase-shift ring is used to generate circularly polarized radiation. To further expand the bandwidth, four short-circuit branches are added between the reflective floor and the radiator, creating two circularly polarized resonance points. This invention achieves a relative impedance matching bandwidth of 85% and a relative axial ratio bandwidth of 67%.

[0004] Most existing technologies use methods such as adding branches, parasitic patches, and reflective cavities to the radiator to expand the axial ratio bandwidth and gain performance of circular polarization. Usually, broadband circularly polarized cross-dipole antennas also introduce a feeding network to achieve circularly polarized radiation. However, the disadvantages of such devices are large gain fluctuations within the frequency range, narrow circularly polarized radiation bandwidth, complex feeding network structure, or severe high-frequency gain attenuation. Summary of the Invention

[0005] Based on this, an object of the present invention is to provide a broadband circularly polarized cross-dipole antenna.

[0006] A broadband circularly polarized cross-dipole antenna, characterized in that it includes a first dielectric plate, a metal floor, an antenna radiator and a feed coaxial line, wherein the metal floor is arranged below the first dielectric plate; the antenna radiator is mounted on the first dielectric plate and includes four dipole arms of identical structure, namely a first dipole arm, a second dipole arm, a third dipole arm and a fourth dipole arm, the first dipole arm and the second dipole arm are arranged on the upper surface of the first dielectric plate, the third dipole arm and the fourth dipole arm are arranged on the lower surface of the first dielectric plate, and the first dipole arm, the second dipole arm, the third dipole arm and the fourth dipole arm are rotationally symmetric with the center of the first dielectric plate as a fixed point and at a rotation angle of 90 degrees; the feed coaxial line passes through the center of the first dielectric plate and the metal floor and is electrically connected to the antenna radiator.

[0007] The broadband circularly polarized cross-dipole antenna of the present invention has a wide impedance matching frequency band and adopts coaxial line feeding in the feeding network instead of a complex equal power division phase shifting network, which greatly reduces the process requirements and production costs.

[0008] Furthermore, the first dipole arm includes a first long arm, the proximal end of the first long arm is arranged at the center of the upper surface of the first dielectric plate; the second dipole arm includes a second long arm, the angle between the second long arm and the first long arm is 90°, and the proximal end of the second long arm is connected to the proximal end of the first long arm; the third dipole arm includes a third long arm, the proximal end of the third long arm is arranged at the center of the lower surface of the first dielectric plate, and the angle between the third long arm and the first long arm is 180°; the fourth dipole arm includes a fourth long arm, the angle between the fourth long arm and the second long arm is 180°, and the proximal end of the fourth long arm is connected to the proximal end of the third long arm.

[0009] Furthermore, the proximal end of the second long arm is connected to the proximal end of the first long arm through a metal arc connecting line; the proximal end of the fourth long arm is connected to the proximal end of the third long arm through a metal arc connecting line.

[0010] Furthermore, the first dipole arm further includes a first strip-shaped branch, the proximal end of the first strip-shaped branch being connected to the distal end of the first long arm; the second dipole arm further includes a second strip-shaped branch, the proximal end of the second strip-shaped branch being connected to the distal end of the second long arm; the third dipole arm further includes a third strip-shaped branch, the proximal end of the third strip-shaped branch being connected to the distal end of the third long arm; and the fourth dipole arm further includes a fourth strip-shaped branch, the proximal end of the fourth strip-shaped branch being connected to the distal end of the fourth long arm.

[0011] Furthermore, the angle between the first strip branch and the first long arm, the angle between the second strip branch and the second long arm, the angle between the third strip branch and the third long arm, and the angle between the fourth strip branch and the fourth long arm are all 30°.

[0012] Furthermore, the first dipole arm also includes a first arc-shaped branch, the proximal end of the first arc-shaped branch is connected to the distal end of the first strip-shaped branch, and the distal end of the first arc-shaped branch is close to the first long arm; the second dipole arm also includes a second arc-shaped branch, the proximal end of the second arc-shaped branch is connected to the distal end of the second strip-shaped branch, and the distal end of the second arc-shaped branch is close to the second long arm; the third dipole arm also includes a third arc-shaped branch, the proximal end of the third arc-shaped branch is connected to the distal end of the third strip-shaped branch, and the distal end of the third arc-shaped branch is close to the third long arm; the fourth dipole arm also includes a fourth arc-shaped branch, the proximal end of the fourth arc-shaped branch is connected to the distal end of the fourth strip-shaped branch, and the distal end of the fourth arc-shaped branch is close to the fourth long arm.

[0013] Furthermore, the curvature of the first arc-shaped branch, the second arc-shaped branch, the third arc-shaped branch and the fourth arc-shaped branch is 270°.

[0014] Furthermore, it also includes a second dielectric plate, which is arranged between the first dielectric plate and the metal floor. The surface of the second dielectric plate facing the first dielectric plate is provided with a plurality of rectangular open metal patches arranged in an array, which are used to form a metasurface reflection array.

[0015] Furthermore, a circular groove is provided at the center of the rectangular open metal patch, and strip grooves connecting the circular groove and the outside are provided on two diagonal lines on one side of the circular groove.

[0016] Furthermore, it also includes support columns, which penetrate and connect the first dielectric plate, the second dielectric plate and the metal floor, and are used to support and fix the entire structure.

[0017] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the broadband circularly polarized cross-dipole antenna of the present invention;

[0019] Figure 2 is a schematic diagram of the antenna radiator of the present invention;

[0020] Figure 3 is a schematic diagram of a second dielectric plate of the present invention;

[0021] Figure 4 is the reflection coefficient of the excitation port of the present invention |S 11 |Schematic diagram;

[0022] Figure 5 Schematic diagram of the circularly polarized radiation axis ratio of the present invention;

[0023] Figure 6 Schematic diagram of the gain coefficient of the present invention;

[0024] Figure 7 Schematic diagram of the radiation direction of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be noted that the terms "upper" and "lower" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0027] It should also be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0028] See also Figure 1 A broadband circularly polarized cross-dipole antenna includes a first dielectric plate 100, a metal floor 200, an antenna radiator 300, and a feeding coaxial line 400. The antenna radiator 300 is arranged on the first dielectric plate 100 for receiving signals; the metal floor 200 is arranged below the first dielectric plate 100 for reflecting electromagnetic waves; the feeding coaxial line 400 passes through the first dielectric plate 100 and the metal floor 200, and is connected to the antenna radiator 300 for providing feeding to the antenna radiator 300.

[0029] A through-hole is defined in the center of the first dielectric plate 100 for the inner conductor of the feed coaxial line 400 to pass through. The metal floor 200 is disposed beneath the first dielectric plate 100. Its surface is made of metal, which reflects electromagnetic waves. In this embodiment, the metal floor 200 is made of a dielectric plate with a metal layer printed on the surface facing the first dielectric plate 100. A through-hole is defined in the center for the feed coaxial line 400 to pass through.

[0030] See also Figure 2 The antenna radiator 300 is disposed on the first dielectric plate 100 and is made of a metal material. It includes four dipole arms of identical structure, namely a first dipole arm 310, a second dipole arm 320, a third dipole arm 330, and a fourth dipole arm 340. The first dipole arm 310 and the second dipole arm 320 are disposed on the upper surface of the first dielectric plate 100, while the third dipole arm 330 and the fourth dipole arm 340 are disposed on the lower surface of the first dielectric plate 100. The first dipole arm 310, the second dipole arm 320, the third dipole arm 330, and the fourth dipole arm 340 are rotationally symmetric about the center of the first dielectric plate 100 at a rotation angle of 90 degrees.

[0031] The first dipole arm 310 includes a first long arm 311, the proximal end of which is located at the center of the upper surface of the first dielectric plate 100. The second dipole arm 320 includes a second long arm 321, the angle between the second long arm 321 and the first long arm 311 is 90°, and the proximal end of the second long arm 321 abuts the proximal end of the first long arm 311 and is connected to the proximal end of the first long arm 311 via a metal arc connecting wire 350. The third dipole arm 330 includes a third long arm 331, the proximal end of which is located at the center of the lower surface of the first dielectric plate 100 and a 180° angle between the third long arm 331 and the first long arm 311. The fourth dipole arm 340 includes a fourth long arm 341, the angle between the fourth long arm 341 and the second long arm 321 is 180°, and the proximal end of the fourth long arm 341 abuts the proximal end of the third long arm 331 and is connected to the proximal end of the third long arm 331 via a metal arc connecting wire 350. The first long arm 311, the second long arm 321, the third long arm 331 and the fourth long arm 341 together constitute a cross dipole pair, forming a 3dB axial ratio minimum point at the 4 GHz frequency, thereby forming a first circular polarization mode, and can generate impedance resonance points at the 3.5 GHz and 5.5 GHz frequencies.

[0032] Preferably, the first dipole arm 310 further includes a first strip branch 312, the proximal end of the first strip branch 312 being connected to the distal end of the first long arm 311; the second dipole arm 320 further includes a second strip branch 322, the proximal end of the second strip branch 322 being connected to the distal end of the second long arm 321. The third dipole arm 330 further includes a third strip branch 332, the proximal end of the third strip branch 332 being connected to the distal end of the third long arm 321; the fourth dipole arm 340 further includes a fourth strip branch 342, the proximal end of the fourth strip branch 342 being connected to the distal end of the fourth long arm 341. By adding strip branches, a second circularly polarized mode can be generated at a frequency of 3.1 GHz, and impedance matching can be achieved to generate a resonance point near a frequency of 2.5 GHz in the low frequency band. Furthermore, the angle between the strip branch and the long arm is set to 30°, that is, the angle between the first strip branch 312 and the first long arm 311 is 30°, the angle between the second strip branch 322 and the second long arm 321 is 30°, the angle between the third strip branch 332 and the third long arm 331 is 30°, and the angle between the fourth strip branch 342 and the fourth long arm 341 is 30°, thereby achieving the best effect.

[0033] More preferably, the first dipole arm 310 further includes a first arc-shaped branch 313, the proximal end of the first arc-shaped branch 313 is connected to the distal end of the first strip-shaped branch 312, and the distal end of the first arc-shaped branch 313 is close to the first long arm 311; the second dipole arm 320 further includes a second arc-shaped branch 323, the proximal end of the second arc-shaped branch 323 is connected to the distal end of the second strip-shaped branch 322, and the distal end of the second arc-shaped branch 323 is close to the second long arm 321. The third dipole arm 330 also includes a third arcuate branch 333, the proximal end of which is connected to the distal end of the third strip branch 332, and the distal end of the third arcuate branch 332 is close to the third long arm 331; the fourth dipole arm 340 also includes a fourth arcuate branch 343, the proximal end of which is connected to the distal end of the fourth strip branch 342, and the distal end of the fourth arcuate branch 343 is close to the fourth long arm 341. By adding arcuate branches, the impedance matching bandwidth and axial ratio bandwidth can be further expanded, and a third circular polarization mode can be generated at a frequency of 5 GHz. Furthermore, the curvature of the first arcuate branch 313, the second arcuate branch 323, the third arcuate branch 333, and the fourth arcuate branch 343 is 270°.

[0034] The feeding coaxial line 400 passes through the central through holes of the metal floor 200 and the first dielectric plate 100 and is connected to the first long arm 311 and the third long arm 331 to supply power to the antenna radiator 300 .

[0035] See also Figure 3 To improve the antenna's gain in high-frequency bands, some embodiments further include a second dielectric plate 500 with a metasurface reflective array. This metasurface reflective array improves gain in different frequency bands. The second dielectric plate 500 is disposed between the first dielectric plate 100 and the metal floor 200, and a metasurface reflective array is disposed on the surface facing the first dielectric plate 100. The metasurface reflective array comprises a plurality of rectangular open metal patches 510 arranged in an array. Each of these rectangular open metal patches 510 is made of metal and has a central circular groove 511. Two diagonal grooves 512 are disposed along one half of each patch. These grooves 512 connect the central circular groove 511 with the outside world, forming an opening. The metasurface reflective array ensures that the phase of the electromagnetic wave reflected from the metal floor 200 upon reaching the antenna radiator 300 is the same as that of the forward wave. This allows the reflected electromagnetic wave to overlap with the forward radiated electromagnetic wave, thereby improving the antenna's gain in high-frequency bands. Furthermore, the gain effect for different frequency bands can be adjusted by adjusting the opening size of the rectangular opening metal patch 510 and the distance between the rectangular opening metal patch 510 and the metal floor 200 .

[0036] In some embodiments, in order to improve the overall stability of the device, four support columns 600 are provided, which penetrate and connect the first dielectric plate 100, the second dielectric plate 500 and the metal floor 200 and are arranged at equal intervals around the feeding coaxial line 400.

[0037] The working frequency band of the present invention is 2.35GHz-5.09GHz, and the 3dB axial ratio bandwidth of its circularly polarized radiation is 73.66%, which has a wide axial ratio bandwidth. It covers multiple frequency bands including 2.4GHz for the Internet of Things, 3.3-3.8GHz for 5G communication, and 4.5-4.8GHz for satellite mobile communications. In the working frequency band of 2.35-5.09GHz, the gain of the broadband circularly polarized dipole antenna is 4.01-8.0dBi, with relatively stable gain and good radiation direction. To further illustrate the performance of the present invention, please refer to Figure 4-7 . Figure 4 The reflection coefficient of the excitation port of the present invention is shown in |S 11 |, Figure 5 The circular polarization radiation axial ratio of the present invention is demonstrated. Figure 6 The gain of the present invention is shown. Figure 7 The radiation directions of the present invention at 2.4 GHz, 3.4 GHz, and 4.4 GHz are demonstrated.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) It has a wide impedance matching frequency band and adopts coaxial line feeding instead of complex equal power division phase shifting network, which greatly reduces the process requirements and production costs.

[0040] (2) Metal arc connecting lines are used to provide 90° phase delay and equal amplitude field strength for the two pairs of dipole arms, forming broadband circularly polarized radiation; at the same time, the metal arc connecting lines on the upper and lower surfaces of the dielectric plate are coupled to effectively expand the impedance matching bandwidth.

[0041] (3) By optimizing the design of the dipole arm, a long metal arm is set to generate circularly polarized radiation near 4 GHz. Adding a 30° inclined metal branch can generate circularly polarized radiation near 3.1 GHz. Adding a 270° arc branch can generate circularly polarized radiation near 5 GHz. The combination of the three circularly polarized modes forms broadband circularly polarized radiation, while further expanding the impedance matching bandwidth.

[0042] (4) A metasurface reflective array is set up to increase the gain near 5.1 GHz to 4.5 dB, improving the gain effect. The metasurface reflective array can also improve the gain of different frequency bands by adjusting the size of the metal rectangular opening and the distance between the metasurface reflective array and the metal floor.

[0043] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that, unless otherwise specified, "multiple" refers to two or more; the terms "first", "second", "third", etc. are only used to distinguish, and are not used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. The term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items. When the above description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of the present invention, for those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0044] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, and the present invention is intended to encompass such modifications and variations.

Claims

1. A broadband circularly polarized cross-dipole antenna, characterized by: The antenna comprises a first dielectric plate, a metal floor, an antenna radiator and a feeding coaxial line, wherein the metal floor is arranged below the first dielectric plate; the antenna radiator is mounted on the first dielectric plate and comprises four dipole arms of identical structure, namely a first dipole arm, a second dipole arm, a third dipole arm and a fourth dipole arm, wherein the first dipole arm and the second dipole arm are arranged on the upper surface of the first dielectric plate, and the third dipole arm and the fourth dipole arm are arranged on the lower surface of the first dielectric plate, and the first dipole arm, the second dipole arm, the third dipole arm and the fourth dipole arm are rotationally symmetrical with respect to the center of the first dielectric plate at a rotation angle of 90 degrees; the feeding coaxial line passes through the center of the first dielectric plate and the metal floor and is electrically connected to the antenna radiator.

2. The broadband circularly polarized cross-dipole antenna according to claim 1, wherein: The first dipole arm includes a first long arm, the proximal end of which is arranged at the center of the upper surface of the first dielectric plate; the second dipole arm includes a second long arm, the angle between the second long arm and the first long arm is 90°, and the proximal end of the second long arm is connected to the proximal end of the first long arm; the third dipole arm includes a third long arm, the proximal end of the third long arm is arranged at the center of the lower surface of the first dielectric plate, and the angle between the third long arm and the first long arm is 180°; the fourth dipole arm includes a fourth long arm, the angle between the fourth long arm and the second long arm is 180°, and the proximal end of the fourth long arm is connected to the proximal end of the third long arm.

3. The broadband circularly polarized cross-dipole antenna according to claim 2, wherein: The proximal end of the second long arm is connected to the proximal end of the first long arm through a metal arc connecting line; the proximal end of the fourth long arm is connected to the proximal end of the third long arm through a metal arc connecting line.

4. The broadband circularly polarized cross-dipole antenna according to claim 3, wherein: The first dipole arm further includes a first strip-shaped branch, the proximal end of which is connected to the distal end of the first long arm; the second dipole arm further includes a second strip-shaped branch, the proximal end of which is connected to the distal end of the second long arm. The third dipole arm further includes a third strip-shaped branch, the proximal end of which is connected to the distal end of the third long arm; and the fourth dipole arm further includes a fourth strip-shaped branch, the proximal end of which is connected to the distal end of the fourth long arm.

5. The broadband circularly polarized cross-dipole antenna according to claim 4, wherein: The angle between the first strip branch and the first long arm, the angle between the second strip branch and the second long arm, the angle between the third strip branch and the third long arm, and the angle between the fourth strip branch and the fourth long arm are all 30°.

6. The broadband circularly polarized cross-dipole antenna according to claim 5, wherein: The first dipole arm also includes a first arc-shaped branch, the proximal end of the first arc-shaped branch is connected to the distal end of the first strip-shaped branch, and the distal end of the first arc-shaped branch is close to the first long arm; the second dipole arm also includes a second arc-shaped branch, the proximal end of the second arc-shaped branch is connected to the distal end of the second strip-shaped branch, and the distal end of the second arc-shaped branch is close to the second long arm; the third dipole arm also includes a third arc-shaped branch, the proximal end of the third arc-shaped branch is connected to the distal end of the third strip-shaped branch, and the distal end of the third arc-shaped branch is close to the third long arm; the fourth dipole arm also includes a fourth arc-shaped branch, the proximal end of the fourth arc-shaped branch is connected to the distal end of the fourth strip-shaped branch, and the distal end of the fourth arc-shaped branch is close to the fourth long arm.

7. The broadband circularly polarized cross-dipole antenna according to claim 6, wherein: The curvature of the first arc-shaped branch node, the second arc-shaped branch node, the third arc-shaped branch node and the fourth arc-shaped branch node is 270°.

8. The broadband circularly polarized cross-dipole antenna according to claim 7, wherein: It also includes a second dielectric plate, which is arranged between the first dielectric plate and the metal floor. The surface of the second dielectric plate facing the first dielectric plate is provided with a plurality of rectangular open metal patches arranged in an array, which are used to form a metasurface reflection array.

9. The broadband circularly polarized cross-dipole antenna according to claim 8, wherein: A circular groove is provided at the center of the rectangular opening metal patch, and strip grooves connecting the circular groove and the outside are provided on two diagonal lines on one side of the circular groove.

10. The broadband circularly polarized cross-dipole antenna according to claim 9, wherein: It also includes support columns, which penetrate and connect the first dielectric plate, the second dielectric plate and the metal floor, and are used to support and fix the entire structure.

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