A broadband axial-ratio circularly polarized antenna based on tight coupling principle

Abstract

This invention provides a wide bandwidth axial ratio circularly polarized antenna based on the tight coupling principle, belonging to the field of microstrip antenna structure design technology. It includes a first dielectric substrate with a feed network printed on its bottom surface, enabling a 1-to-4 power split and 90° phase shift. A second dielectric substrate is arranged parallel to the first substrate, with four arc-shaped metal patches on its bottom surface forming a radiating element. Adjacent patches are tightly coupled through interdigital capacitors. A long strip microstrip line is arranged on the top surface of the second dielectric substrate. Four coaxial feed lines vertically connect the output of the feed network to each metal patch, achieving efficient signal transmission. A ring-shaped metal cavity is provided on the upper surface of the first dielectric substrate, connected to a metal ground, to improve the axial ratio at low elevation angles. This invention achieves wide impedance bandwidth and wide axial ratio bandwidth, and possesses wide axial ratio beamwidth and high radiation efficiency.

Description

Technical Field

[0001] This invention relates to the field of antenna structure design technology, and more specifically, to a wide bandwidth axial ratio circularly polarized antenna based on the tight coupling principle. Background Technology

[0002] Circularly polarized (CP) antennas are widely used in satellite communications, radar detection, and the Internet of Things (IoT) due to their numerous advantages, such as eliminating the Faraday rotation effect of the ionosphere and suppressing multipath interference. However, traditional circularly polarized antenna designs (such as single-feed microstrip patch antennas and quad-arm helical antennas) generally suffer from excessively narrow operating bandwidths, which severely limits their application in communication systems requiring wideband, high-speed transmission.

[0003] Therefore, there is an urgent need for a wide bandwidth axial ratio circularly polarized antenna based on the tight coupling principle to solve the above-mentioned technical problems. Summary of the Invention

[0004] The purpose of this invention is to provide a wide-bandwidth, axial-ratio circularly polarized antenna based on the tight coupling principle to improve the aforementioned problems. To achieve this objective, the technical solution adopted by this invention is as follows: In a first aspect, this application provides a wide bandwidth axial ratio circularly polarized antenna based on the tight coupling principle, comprising: a first dielectric substrate, a feeding network, a second dielectric substrate, a microstrip line, a metal patch, a coaxial feed line, and a metal cavity. The feeding network is disposed on the lower bottom surface of the first dielectric substrate and is used to convert one input signal into four output signals with equal amplitude and sequentially different phases of 90 degrees. The second dielectric substrate is disposed directly above the first dielectric substrate. The microstrip line is disposed on the upper top surface of the second dielectric substrate and is elongated. The metal patch is disposed on the lower bottom surface of the second dielectric substrate, and at least four metal patches are disposed thereon and are arc-shaped. Four coaxial feed lines are disposed, and the two ends of each coaxial feed line are respectively connected to the feeding network and the metal patch. The metal cavity is annular and is disposed on the first dielectric substrate, with the lower bottom surface of the metal cavity connected to the upper top surface of the first dielectric substrate.

[0005] Optionally, the power supply network includes an input port, a first output port, a second output port, a third output port, a fourth output port, a first resistor, a second resistor, a Wilkinson power divider, and a phase shifter, used to achieve a 1-to-4 power division and a 90-degree phase difference.

[0006] Optionally, the output terminal of the input port is connected to the first resistor and the second resistor respectively, the second resistor is connected to the input terminals of the phase shifter and the Wilkinson power divider respectively, the output terminal of the phase shifter is connected to the first output port and the second output port respectively, and the output terminal of the Wilkinson power divider is connected to the third output port and the fourth output port respectively.

[0007] Optionally, the metal patch is provided with interdigital capacitors, coaxial through holes and metal pillars, and the coaxial through holes and metal pillars are respectively provided on the metal patch, and the coaxial through holes and metal pillars are symmetrically arranged along the interdigital capacitors.

[0008] Optionally, two adjacent metal patches are connected end-to-end via the interdigital capacitor.

[0009] Optionally, the top of the metal cavity is flush with the lower surface of the second dielectric plate, and a gap is provided between the outer wall of the metal cavity and the second dielectric plate.

[0010] Optionally, the diameter of the outer wall of the metal cavity is the same as the diameter of the first dielectric plate, and the thickness of the metal cavity is 1 mm.

[0011] Optionally, a metal layer is provided on the top surface of the first dielectric plate.

[0012] The beneficial effects of this invention are as follows: The antenna designed in this invention mainly consists of a power divider phase shifter located on the bottom surface of a first dielectric substrate, a circular metal cavity surrounding the first dielectric substrate, a circular metal patch on the bottom surface of a second dielectric substrate, and a 50Ω coaxial cable for connecting the power divider phase shifter and the circular metal patch. The top surface of the first dielectric substrate is a metal layer. The metal patch and resistors on the bottom surface of the first dielectric substrate form a 1-to-4 broadband power divider phase shifter. The power divider phase shifter is fed by a back-feed coaxial cable. One signal is output as four equal-amplitude signals with a phase difference of 90° through the 1-to-4 power divider phase shifter. The four signals are then transmitted to the circular metal patch located on the bottom surface of the second dielectric substrate via four 50Ω coaxial cables. The annular metal patch consists of four arc-shaped dipoles with interdigital capacitors loaded between them, effectively compensating for the inductive component caused by the ground and achieving impedance matching over a wide bandwidth. The adjacent arc-shaped dipoles are approximately spatially orthogonal, and their feed phases differ by 90°, thus forming a circularly polarized radiation wave. The circular metal cavity surrounding the first dielectric substrate improves the axial ratio at low elevation angles. Therefore, this scheme can realize a circularly polarized antenna with wide bandwidth and axial ratio characteristics.

[0013] The antenna proposed in this invention has an impedance bandwidth of 83.60% (1.10-2.68 GHz), a 3dB axial ratio bandwidth of 106.82% (0.82-2.70 GHz), a bandwidth with a radiation efficiency greater than 70% of 78.45% (1.10-2.52 GHz), and an operating bandwidth (i.e., overlap bandwidth) of 78.45% (1.10-2.52 GHz). Furthermore, within the frequency range of 1.15-1.80 GHz, the antenna's 3dB axial ratio beamwidth is greater than 140° in both the phi = 0° and phi = 90° sections.

[0014] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the overall structure of the wide bandwidth axial ratio circularly polarized antenna based on the tight coupling principle described in this embodiment of the invention; Figure 2 for Figure 1 Schematic diagram of cross-section at point AA; Figure 3 This is a schematic diagram of the annular metal patch of the wide bandwidth axial ratio circularly polarized antenna based on the tight coupling principle described in this embodiment of the invention. Figure 4 This is a schematic diagram of the feed network for a wide bandwidth axial ratio circularly polarized antenna based on the tight coupling principle as described in an embodiment of the present invention. Figure 5 This is a schematic diagram of the reflection coefficient and 3dB axial ratio operating bandwidth of the wide bandwidth axial ratio circularly polarized antenna described in this embodiment of the invention; Figure 6 This is a schematic diagram showing the actual gain and radiation efficiency of the wide bandwidth axial ratio circularly polarized antenna described in this embodiment of the invention; Figure 7 This is a schematic diagram of the 3dB axial ratio beamwidth of the wide bandwidth axial ratio circularly polarized antenna in the two basic azimuth planes of 1.1-1.9GHz, as described in this embodiment of the invention.

[0017] The diagram shows the following labels: 1. Second dielectric substrate; 2. Microstrip line; 3. Metal patch; 4. Feed network; 5. Metal cavity; 6. Coaxial feed line; 7. Metal layer; 8. First dielectric substrate; 31. Interdigital capacitor; 32. Coaxial via; 33. Metal pillar; 41. Phase shifter; 42. First resistor; 43. Second resistor; 44. Wilkinson power divider; 45. Input port; 46. First output port; 47. Second output port; 48. Third output port; 49. Fourth output port. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0019] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0020] Example 1:

[0021] This embodiment provides a wide bandwidth axial ratio circularly polarized antenna based on the tight coupling principle.

[0022] See Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7The figure shows a wide bandwidth axial ratio circularly polarized antenna based on the tight coupling principle, comprising: a first dielectric substrate 8; a feed network 4, a second dielectric substrate 1, a microstrip line 2, a metal patch 3, a coaxial feed line 6, and a metal cavity 5. The feed network 4 is disposed on the bottom surface of the first dielectric substrate 8 and is used to convert one input signal into four output signals with equal amplitude and sequentially different phases of 90 degrees. The second dielectric substrate 1 is disposed directly above the first dielectric substrate 8. The microstrip line 2 is disposed on the top surface of the second dielectric substrate 1 and is elongated. The metal patch 3 is disposed on the bottom surface of the second dielectric substrate 1, and at least four metal patches 3 are disposed, and the metal patches are arc-shaped. There are four coaxial feed lines 6, and the two ends of each coaxial feed line 6 are connected to the feed network 4 and the metal patch 3, respectively. The metal cavity 5 is annular and is disposed on the first dielectric substrate 8, with its bottom surface connected to the top surface of the first dielectric substrate 8.

[0023] It is understood that the antenna designed in this invention mainly consists of a feed network 4 located on the first dielectric substrate 8, a circular metal cavity 5 surrounding the first dielectric substrate 8, a circular metal patch 3 printed on the bottom surface of the second dielectric substrate 1, and a 50Ω coaxial feed line 6 for connecting the feed network 4 and the circular metal patch 3. The top surface of the first dielectric substrate 8 is a metal layer. The metal patch 3 printed on the bottom surface of the first dielectric substrate 8 and the resistor form a one-to-four broadband feed network 4. The feed network 4 is fed by a back-feed coaxial line. One signal is output as four equal-amplitude signals with a phase difference of 90° through the one-to-four feed network 4. The four signals are then transmitted to the circular metal patch 3 located on the bottom surface of the second dielectric substrate 1 through four 50Ω coaxial feed lines 6. The annular metal patch 3 consists of four arc-shaped dipoles, with interdigital capacitors 31 loaded between them. This effectively compensates for the inductive component caused by the ground, achieving impedance matching over a wide bandwidth. The adjacent arc-shaped dipoles are approximately spatially orthogonal, and their feed phases differ by 90°, thus forming a circularly polarized radiation wave. The circular metal cavity 5 surrounding the first dielectric substrate 8 is used to improve the axial ratio at low elevation angles. Therefore, this scheme can realize a circularly polarized antenna with wide bandwidth axial ratio characteristics.

[0024] The power supply network 4 includes an input port 45, a first output port 46, a second output port 47, a third output port 48, a fourth output port 49, a first resistor 42, a second resistor 43, a Wilkinson power divider 44, and a phase shifter 41, which are used to achieve a 1-to-4 power division and a 90-degree phase difference.

[0025] It is understood that the top surface of the first dielectric substrate 8 of the present invention is a metal layer 7, and the bottom surface is printed with a one-to-four feed network 4, which can generate four excitation signals with equal amplitude and phase difference of 90° in a wide frequency band; the bottom surface of the second dielectric substrate 1 is provided with a ring-shaped metal patch 3 composed of four arc-shaped dipoles as radiation units, and the interdigital capacitors 31 loaded between the dipoles effectively compensate for the inductive component caused by the ground, realizing impedance matching in a wide frequency range.

[0026] The output terminal of the input port 45 is connected to the first resistor 42 and the second resistor 43 respectively. The second resistor 43 is connected to the input terminals of the phase shifter 41 and the Wilkinson power divider 44 respectively. The output terminal of the phase shifter 41 is connected to the first output port 46 and the second output port 47 respectively. The output terminal of the Wilkinson power divider 44 is connected to the third output port 48 and the fourth output port 49 respectively.

[0027] It is understandable that the specific connection structure of this feeding network is as follows: the input signal first passes through the matching network formed by the first resistor 42 and the second resistor 43 via the input port 45, and then is fed in parallel into the phase shifter branch 41 and the Wilkinson power divider branch 44, finally generating four excitation signals with equal amplitude and phase difference of 90 degrees respectively connected to the four output ports. This achieves precise phase control and high port isolation over a wide range, providing a stable and reliable excitation source for the radiating element to generate high-purity circularly polarized waves. At the same time, its integrated microstrip line design ensures the compactness and ease of manufacturing of the antenna structure.

[0028] The metal patch 3 is provided with an interdigital capacitor 31, a coaxial through hole 32 and a metal pillar 33. The coaxial through hole 32 and the metal pillar 33 are respectively provided on the metal patch 3, and the coaxial through hole 32 and the metal pillar 33 are symmetrically arranged along the interdigital capacitor 31.

[0029] Understandably, when the antenna element is close to metal layer 7, a significant inductive component is introduced, leading to impedance mismatch and narrowing bandwidth. The capacitive effect generated by the interdigital capacitor can precisely compensate for this inductive component, keeping the antenna's input impedance stable over a very wide frequency range.

[0030] Two adjacent metal patches 3 are connected end to end by the interdigital capacitor 31.

[0031] It is understandable that the connection between two adjacent metal patches 3 via the interdigital capacitor 31 provides a continuous, low-resistance path for surface current, allowing the four arc-shaped dipoles to work collaboratively and radiate as a whole, rather than as four independent oscillators. This is the basis for generating a stable, symmetrical radiation pattern. This connection enhances the rigidity of the entire radiating patch, reducing the risk of structural deformation or breakage due to vibration or thermal expansion and contraction during processing or use.

[0032] The top of the metal cavity 5 is flush with the lower surface of the second dielectric plate 1, and a gap is provided between the outer wall of the metal cavity 5 and the second dielectric plate 1.

[0033] It is understandable that the height setting of the top of the metal cavity 5 and the lower surface of the second dielectric substrate 1 is a key parameter affecting its impedance, radiation pattern, and frequency characteristics. This flush design ensures the manufacturing consistency and long-term stability of this height parameter, which is crucial for maintaining antenna performance.

[0034] The diameter of the outer wall of the metal cavity 5 is the same as the diameter of the first dielectric plate 8, and the thickness of the metal cavity 5 is 1 mm.

[0035] It is understandable that the outer wall diameter of the metal cavity 5 is the same as the diameter of the first dielectric substrate 8, meaning that the metal cavity perfectly encloses the bottom dielectric substrate and aligns with the edge of the first dielectric substrate 8, forming a regular and uniform cylindrical appearance and structural whole. This avoids protrusions or depressions caused by component size mismatch, not only making the structure more aesthetically pleasing, but more importantly, eliminating potential stress concentration points and enhancing overall rigidity. The metal cavity and the first dielectric substrate 8 together constitute a complete reference ground potential and electromagnetic shielding cavity. Its diameter is the same as the diameter of the dielectric substrate, meaning that the electric field and current distribution generated by the annular metal patch 3 can be well defined by this cavity, providing a stable and predictable radiation environment for the antenna. This is the basis for obtaining a stable radiation pattern.

[0036] The first dielectric plate 8 has a metal layer 7 on its top surface.

[0037] It is understood that the present invention provides a metal ground 7 on the top surface of the first dielectric substrate 8 as a reference for antenna radiation, forming a complete signal loop.

[0038] It should be noted that the specific manner in which each module performs its operation in the apparatus described in the above embodiments has been described in detail in the embodiments of the method, and will not be elaborated here.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0040] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A wide bandwidth axial ratio circularly polarized antenna based on the principle of tight coupling, characterized in that, include: First dielectric plate (8); The power supply network (4) is disposed on the bottom surface of the first dielectric plate (8). The power supply network (4) is used to convert one input signal into four output signals with equal amplitude and phase difference of 90 degrees. The second medium plate (1) is disposed directly above the first medium plate (8); Microstrip line (2), the microstrip line (2) is disposed on the top surface of the second dielectric plate (1), and the microstrip line (2) is configured as a strip; Metal patch (3), the metal patch (3) is disposed on the bottom surface of the second medium plate (1), the metal patch (3) is provided in at least four pieces, and the metal patch is configured as an arc shape; The coaxial feeder (6) has four wires, and the two ends of each coaxial feeder (6) are connected to the power supply network (4) and the metal patch (3) respectively. Metal cavity (5), the metal cavity (5) is annular, the metal cavity (5) is disposed on the first dielectric plate (8), and the bottom surface of the metal cavity (5) is connected to the top surface of the first dielectric plate (8); The power supply network (4) includes an input port (45), a first output port (46), a second output port (47), a third output port (48), a fourth output port (49), a first resistor (42), a second resistor (43), a Wilkinson power divider (44), and a phase shifter (41), used to achieve a 1-to-4 power division and a 90-degree phase difference; The output terminal of the input port (45) is connected to the first resistor (42) and the second resistor (43) respectively. The second resistor (43) is connected to the input terminals of the phase shifter (41) and the Wilkinson power divider (44) respectively. The output terminal of the phase shifter (41) is connected to the first output port (46) and the second output port (47) respectively. The output terminal of the Wilkinson power divider (44) is connected to the third output port (48) and the fourth output port (49) respectively.

2. The wide bandwidth axial ratio circular polarized antenna based on the close-coupling principle according to claim 1, characterized in that, include: The metal patch (3) is provided with an interdigital capacitor (31), a coaxial through hole (32) and a metal pillar (33). The metal patch (3) is provided with a coaxial through hole (32) and a metal pillar (33) respectively. The coaxial through hole (32) and the metal pillar (33) are symmetrically arranged along the interdigital capacitor (31).

3. The wide bandwidth axial ratio circular polarized antenna based on the principle of tight coupling according to claim 2, characterized in that, include: Two adjacent metal patches (3) are connected end to end through the interdigital capacitor (31).

4. The wide bandwidth axial ratio circular polarized antenna based on the close-coupling principle according to claim 1, characterized in that, include: The top of the metal cavity (5) is flush with the lower surface of the second medium plate (1), and a gap is provided between the outer wall of the metal cavity (5) and the second medium plate (1).

5. The wide bandwidth axial ratio circular polarized antenna based on tight coupling principle according to claim 1, characterized in that, include: The diameter of the outer wall of the metal cavity (5) is the same as the diameter of the first dielectric plate (8), and the thickness of the metal cavity (5) is 1 mm.

6. The wide bandwidth axial ratio circular polarized antenna based on the principle of tight coupling according to claim 1, characterized in that, include: A metal layer (7) is provided on the top surface of the first dielectric plate (8).

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