Broadband circularly polarized antenna loaded with novel coupling structure

Abstract

The invention aims to provide a broadband circularly polarized antenna loaded with a novel coupling structure, and belongs to the technical field of circularly polarized antennas. The antenna comprises a radiation structure, a supporting structure, a coaxial feed structure and a reflecting plate, wherein the radiation structure comprises a parasitic radiation patch, a cross dipole antenna and a radiation dielectric substrate; by innovatively designing the parasitic radiation patch, the bandwidth of the circularly polarized antenna can reach 53.3% when the circularly polarized antenna is in the working frequency band of 1.046-1.846 GHz, and the maximum gain of the circularly polarized antenna can reach 7.3 dB.

Description

Technical Field

[0001] The invention belongs to the technical field of circularly polarized antennas, and in particular relates to a broadband circularly polarized antenna loaded with a novel coupling structure. Background Art

[0002] Since the end of the 20th century, wireless communication technology has experienced a leapfrog development from 1G to 5G. With the continuous advancement of technologies such as mobile communications, satellite communications, and the Internet of Things, the demand for antenna systems that can provide wider bandwidth, higher data transmission rates, and better signal quality has become more urgent. Circularly polarized antennas can provide 360-degree all-round signal coverage, effectively reducing multipath effects and signal attenuation, thereby improving communication quality. This feature gives circularly polarized antennas an irreplaceable advantage in satellite communications, broadcasting, radar detection, and other fields.

[0003] Although circularly polarized antennas have many advantages in theory, they still face problems such as bandwidth limitation, reduced gain, large size, and high manufacturing cost in practical applications. IEEE Antennas and Wireless Propagation Letters , vol. 13, pp. 67-70, 2014) proposed a wideband circularly polarized antenna with an impedance bandwidth of 50.2% (1.99-3.22 GHz) and a maximum gain of 6.8 dBic at the center frequency; Zongquan Liu, Zuping Qian et al. (Zong-Quan Liu, Zuping Qian. Design of a Wideband DualCircularly Polarized Microstrip Antenna[C].Microwave and Millimeter Wave Technology. 2012: 1-4.) improved the structure of the PIFA antenna and created a new antenna that was fed from two positions. Its circular polarization bandwidth could reach 49.2%, and its average gain was 3dB within its working bandwidth of 1.2~2.04GHz; Hua Pengcheng (Research on Broadband Circularly Polarized Antennas [D]. Xidian University, 2017.) proposed a new type of cross electric dipole antenna. Although its maximum gain is 7.01dB, its standing wave ratio bandwidth is only 41.5% (2.08~3.17GHz).

[0004] Therefore, how to design circularly polarized antennas to have wider bandwidth has become a research focus. Summary of the invention

[0005] Aiming at the problems existing in the background art, the purpose of the present invention is to provide a broadband circularly polarized antenna loaded with a novel coupling structure. The antenna includes a radiation structure, a support structure, a coaxial feeding structure, and a reflector. The radiation structure includes parasitic radiation patches, a crossed dipole antenna, and a radiation dielectric substrate. By innovatively designing the parasitic radiation patches, the bandwidth of the circularly polarized antenna can reach 53.3% in the operating frequency band of 1.046 - 1.846 GHz, and the maximum gain can reach 7.3 dB.

[0006] To achieve the above object, the technical solution of the present invention is as follows: A broadband circularly polarized antenna loaded with a novel coupling structure, including a radiation structure, support columns, a coaxial feeding structure, and a reflector; Among them, the radiation structure includes parasitic radiation patches, a crossed dipole antenna, and a radiation dielectric substrate; the radiation dielectric substrate is square; The crossed dipole antenna includes an upper dipole arm disposed on the upper surface of the radiation dielectric substrate and a lower dipole arm disposed on the lower surface of the radiation dielectric substrate; the upper dipole arm and the lower dipole arm have the same structure, and both include two non - contacting rectangular metal sheets and a metal open - ring. The open - ring is three - quarters of a circle. Among them, the two rectangular metal sheets are perpendicular to each other and are connected by the open - ring; the upper dipole arm and the lower dipole arm are orthogonally placed, and there is a 180° phase difference between the openings of the two rings to generate circularly polarized waves. The parasitic radiation patch includes four square metal patches with the same structure. Two of the square metal patches are disposed on the upper surface of the radiation dielectric substrate, and two square metal patches are disposed on the lower surface of the radiation dielectric substrate; and the four square metal patches are distributed in a "field" - shaped structure and are centrosymmetric about the center point of the radiation dielectric substrate. A sector - shaped slit with a central angle of 90° is provided at the position of each square metal patch close to the center of the radiation dielectric substrate. The center of the sector - shaped slit, the vertex of the square metal patch, and the center of the radiation dielectric substrate are on a straight line; an "L" - shaped slit is also provided on the square metal patch. The opening of the "L" - shaped slit faces the arc side of the sector - shaped slit, and the two arms of the "L" - shaped slit are symmetric about the connection line between the center of the sector - shaped slit and the center of the radiation dielectric substrate; chamfering is performed at the vertex of the square metal patch where the two arms of the "L" - shaped slit face. The reflector is a metal plate, and the size of the reflector is not less than the size of the radiation dielectric substrate; The support columns are disposed at the four corners of the reflector and are used to fixedly connect the reflector and the radiation dielectric substrate; The inner conductor of the coaxial feeding structure is connected to the upper dipole arm through the center of the radiation dielectric substrate, and the outer conductor is connected to the lower dipole arm.

[0007] Furthermore, the material of the reflector is preferably copper; the material of the radiation medium substrate is preferably Rogers, F4B, Arlon AD255C, etc.

[0008] Furthermore, the farther the distance between the edge of the square metal patch close to the dipole arm and the dipole arm in the same layer is, the greater the coupling energy is, but the impedance matching of the antenna is poor; the farther the distance is, the smaller the coupling energy is.

[0009] Furthermore, the distance between the edge of the square metal patch close to the dipole arm and the dipole arm in the same layer is preferably 5-7 mm.

[0010] Furthermore, the ratio of the length of the cut corner of the square metal patch to the side length of the square metal patch is 1:7.

[0011] Furthermore, the length of the corner cut of the square metal patch is 5-9 mm.

[0012] Furthermore, the arc length of the fan-shaped slot should be one quarter of the wavelength corresponding to the high frequency in the working frequency band.

[0013] Furthermore, the total length of the two arms of the "L"-shaped slot should be one quarter of the wavelength corresponding to the low frequency in the working frequency band; the width of the slot is preferably 1.5-3.3 mm.

[0014] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: When the standing wave ratio of the circularly polarized antenna designed in the present invention is below 2, the operating frequency band is 1.046-1.846 GHz, the bandwidth is 57.1%, and the maximum gain can reach 7.3 dB; the frequency band with an axial ratio less than 3 dB is 1.219-1.793 GHz, and its axial ratio bandwidth is 40.7%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is an overall schematic diagram of the antenna structure of the present invention.

[0016] Figure 2 FIG. 4 is a top view of the radiation medium substrate.

[0017] Figure 3 Schematic diagram of the structure of the upper dipole arm and the lower dipole arm.

[0018] Figure 4 This is a standing wave ratio diagram of the circularly polarized antenna according to Example 1 of the present invention.

[0019] Figure 5 1 is an axial ratio diagram of the circularly polarized antenna according to embodiment 1 of the present invention.

[0020] Figure 6 This is a gain diagram of the circularly polarized antenna according to Example 1 of the present invention.

[0021] Reference numerals: 1 is a radiation structure, 2 is a support column, 3 is a coaxial feeding structure, 4 is a reflector, 1-1 is a parasitic radiation patch, 1-2 is a crossed dipole antenna, 1-3 is a radiation dielectric substrate, 1-1-1 is a rectangular metal patch, 1-1-2 is a sector-shaped slot, 1-1-3 is an "L"-shaped slot, 1-1-4 is a chamfer, 1-2-1 is an upper dipole arm, and 1-2-2 is a lower dipole arm. Detailed implementation mode

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the implementation modes and the accompanying drawings.

[0023] A broadband circularly polarized antenna loaded with a novel coupling structure, the overall structure diagram of which is as Figure 1 shown, including a radiation structure 1, a support column 2, a coaxial feeding structure 3, and a reflector 4; Among them, the radiation structure 1 includes a parasitic radiation patch 1-1, a crossed dipole antenna 1-2, and a radiation dielectric substrate 1-3; the top view of the radiation dielectric substrate is as Figure 2 shown; The crossed dipole antenna includes an upper dipole arm 1-2-1 arranged on the upper surface of the radiation dielectric substrate 1-3 and a lower dipole arm 1-2-2 arranged on the lower surface of the radiation dielectric substrate; the structural schematic diagrams of the upper dipole arm and the lower dipole arm are as Figure 3 shown, and their structures are the same, both including two non-touching rectangular metal sheets and a metal open ring, and the open ring is three-quarters of a circle; among them, the two rectangular metal sheets are perpendicular to each other and connected by the open ring; the upper dipole arm and the lower dipole arm are orthogonally placed, and there is a 180° phase difference between the openings of the two rings to generate a circularly polarized wave; The parasitic radiation patch includes four rectangular metal patches 1-1-1 with the same structure, two of which are arranged on the upper surface of the radiation dielectric substrate, and two are arranged on the lower surface of the radiation dielectric substrate; and the four rectangular metal patches are distributed in a "field" structure and are centrosymmetric about the center point of the radiation dielectric substrate; A sector-shaped slot 1-1-2 with a central angle of 90° is provided at the position of each rectangular metal patch close to the center of the radiation dielectric substrate, and the center of the sector-shaped slot is on the same straight line as the vertex of the rectangular metal patch and the center of the radiation dielectric substrate; an "L"-shaped slot 1-1-3 is also provided on the rectangular metal patch, the opening of the "L"-shaped slot faces the arc side of the sector-shaped slot, and the two arms of the "L"-shaped slot are symmetric about the connection line between the center of the sector-shaped slot and the center of the radiation dielectric substrate; chamfering is performed at the vertex of the rectangular metal patch where the two arms of the "L"-shaped slot face, forming a chamfer 1-1-4; The reflector plate 4 is a metal plate, and the size of the reflector plate is larger than the size of the radiation medium substrate; The support columns 2 are arranged at the four corners of the reflector plate and are used to fix and connect the reflector plate and the radiation medium substrate; The inner conductor of the coaxial feeding structure 3 is connected to the upper dipole arm through the center of the radiation medium substrate. When the inner conductor passes through the lower dipole arm, a circular gap is set on it to avoid short circuit with the lower dipole arm; the outer conductor is connected to the lower dipole arm.

[0024] An "L"-shaped gap is set on the rectangular metal patch, which can cut the current path on the rectangular metal patch, thereby extending the current path, and the slot is equivalent to introducing a new equivalent capacitor into the original equivalent circuit. The length and width of the slot affect the size of the equivalent capacitor, which can also reflect the change of the corresponding resonant frequency of the antenna; the fan-shaped gap is also designed to cut the current path on the rectangular metal patch, thereby extending the current path and achieving the effect of expanding the bandwidth.

[0025] An "L"-shaped slot is provided on a rectangular metal patch to obtain a notch frequency band, but the circular polarization wave obtained only through the "L"-shaped slot is poor. The present invention innovatively performs corner cutting at the vertices of the rectangular metal patch facing the two arms of the "L"-shaped slot, and the antenna achieves a better circular polarization effect through the "L"-shaped slot and the corner cutting. This is because the rectangular metal patch of the antenna will also radiate after coupling energy from the cross-dipole arms, and it will participate in the radiation of the entire antenna, but the rectangular metal patch without triangular corner cutting cannot achieve circular polarization radiation, which is reflected in the overall radiation performance of the antenna, thereby deteriorating the circular polarization performance of the antenna, and the axial ratio is higher than 3dB at the required frequency band. After corner cutting, it can separate the merged mode, and after sequential rotational symmetry placement (that is, the rectangular metal patches are rotated 90° in sequence and then placed), the circular polarization performance can be improved. In addition, the position of the corner cutting is also specific. If the corner cutting is performed at other positions, such as the lower right corner of the square metal sheet, the tip will be too narrow and the coupling will be affected, so that a single resonant mode cannot be obtained.

[0026] In addition, the spacing between the rectangular metal patch and the cross-dipole arm can directly affect the energy coupled from the dipole to the parasitic coupling patch of the antenna. The closer the distance is, the greater the coupled energy is, and the farther the distance is, the smaller the coupled energy is. The coupling gap between the two can be equivalent to capacitive reactance, which will directly affect the antenna parameters and the impedance matching of the antenna. In this scheme, the size parameters are designed so that the resonant frequency generated by the coupling is near the center frequency, thereby broadening the impedance bandwidth of the antenna. Example 1

[0027] The radiation medium substrate 8 is made of Arlon AD255C (tm), with a relative dielectric constant of 2.55, a dielectric loss of 0.0014, and a size of 120mm×120mm×1.6mm; the support columns are cylinders, with a total of 4 columns, a radius of 3mm, and a height of 60mm; the reflector is made of copper, with a size of 140mm×40mm×0.3mm; the spacing between the "L"-shaped gap and the edge of the square metal sheet is 4mm, and the spacing between the center of the fan-shaped gap and the nearest vertex of the square metal sheet is 1mm.

[0028] The circularly polarized antenna obtained in this embodiment is simulated, and the standing wave ratio diagram, axial ratio diagram and gain diagram of the antenna obtained are respectively as follows: Figure 4 , Figure 5 and Figure 6 The antenna generally works when S11 is less than -10dB. Figure 4 It can be seen that the working frequency band of the antenna is 1.046-1.846GHz, and its bandwidth is 57.1%; Figure 5 It can be seen that the frequency band with an axial ratio less than 3dB is 1.219-1.793GHz, and its axial ratio bandwidth is 40.7%; at the same time, Figure 6 It can be seen that within its operating frequency band, its maximum gain is 7.3 dB. The above shows that the antenna designed by the present invention has a large right-hand circular polarization gain within a wide frequency band.

[0029] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A broadband circularly polarized antenna loaded with a novel coupling structure, characterized in that: It includes a radiation structure, support columns, a coaxial feeding structure and a reflector; wherein, the radiation structure includes parasitic radiation patches, crossed dipole antennas and a radiation dielectric substrate; the radiation dielectric substrate is square; The crossed dipole antenna includes an upper dipole arm disposed on the upper surface of the radiation dielectric substrate and a lower dipole arm disposed on the lower surface of the radiation dielectric substrate; the upper dipole arm and the lower dipole arm have the same structure, and both include two non-touching rectangular metal sheets and a metal open ring, and the open ring is three-quarters of a circle; wherein, the two rectangular metal sheets are perpendicular to each other and connected by the open ring; the upper dipole arm and the lower dipole arm are orthogonally placed, and there is a 180° phase difference between the openings of the two rings to generate a circularly polarized wave; The parasitic radiation patch includes four square metal patches with the same structure, two of which are disposed on the upper surface of the radiation dielectric substrate and two are disposed on the lower surface of the radiation dielectric substrate; and the four square metal patches are distributed in a "field" structure and are centrosymmetric about the center point of the radiation dielectric substrate; A sector-shaped slit with a central angle of 90° is provided at a position of each square metal patch close to the center of the radiation dielectric substrate, and the center of the sector-shaped slit, the vertex of the square metal patch and the center of the radiation dielectric substrate are on a straight line; an "L"-shaped slit is also provided on the square metal patch, the opening of the "L"-shaped slit faces the arc side of the sector-shaped slit, and the two arms of the "L"-shaped slit are symmetric about the connection line between the center of the sector-shaped slit and the center of the radiation dielectric substrate; chamfering is performed at the vertex of the square metal patch where the two arms of the "L"-shaped slit face; The reflector is a metal plate, and the size of the reflector is not less than the size of the radiation dielectric substrate; The support columns are disposed at the four corners of the reflector and are used to fixedly connect the reflector and the radiation dielectric substrate; The inner conductor of the coaxial feeding structure is connected to the upper dipole arm through the center of the radiation dielectric substrate, and the outer conductor is connected to the lower dipole arm.

2. The broadband circularly polarized antenna loaded with a novel coupling structure as claimed in claim 1, characterized in that: The material of the reflector is copper; the material of the radiation dielectric substrate is Rogers, F4B, Arlon or AD255C.

3. The broadband circularly polarized antenna loaded with a novel coupling structure as claimed in claim 1, characterized in that: The farther the side of the square metal patch close to the dipole arm is from the dipole arm of the same layer, the greater the coupled energy, but the impedance matching of the antenna is poor; the closer the distance, the smaller the coupled energy.

4. The broadband circularly polarized antenna loaded with a novel coupling structure as claimed in claim 3, characterized in that: The distance between the side of the square metal patch close to the dipole arm and the dipole arm of the same layer is 5-7 mm.

5. The broadband circularly polarized antenna loaded with a novel coupling structure as claimed in claim 1, characterized in that: The ratio of the length of the chamfered part of the square metal patch to the side length of the square metal patch is 1:

7.

6. The broadband circularly polarized antenna loaded with a novel coupling structure as claimed in claim 5, characterized in that: The length of the chamfered part of the square metal patch is 5-9 mm.

7. The broadband circularly polarized antenna loaded with a novel coupling structure as claimed in claim 1, characterized in that: The arc length of the sector-shaped slit should be one-quarter of the wavelength corresponding to the high-frequency frequency in the working frequency band.

8. The broadband circularly polarized antenna loaded with a novel coupling structure as claimed in claim 1, characterized in that: The total length of the two arms of the "L"-shaped slit should be one-quarter of the wavelength corresponding to the low-frequency frequency in the working frequency band; the width of the slit is 1.5-3.3 mm.

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