Decoupling structure between circularly polarized microstrip antennas

Abstract

The invention belongs to the technical field of microwave antennas, particularly provides a decoupling structure suitable for circularly polarized microstrip antennas, and aims to solve a relatively strong mutual coupling effect between circularly polarized microstrip antennas with relatively small spacing. The microstrip antenna comprises a microstrip radiation structure, namely a decoupling structure, a dielectric substrate, a floor and a coaxial line, wherein the decoupling structure is formed by combining two square metal radiation patches, an n-shaped patch, two strip-shaped patches and five short-circuit probes. The mode counteracting method is used as guidance, coupling counteracting between the two radiation units is achieved by introducing the decoupling structure for the circularly polarized microstrip antenna, the strong mutual coupling effect between the circularly polarized microstrip antennas close to each other is weakened, and the antenna has the advantages of being remarkable in radiation effect improvement, simple in structure, low in profile and the like and is suitable for satellite communication systems and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave antennas, and in particular to a low mutual coupling structure suitable for circularly polarized microstrip antennas, which realizes efficient decoupling in a compact layout through innovative design. Background Art

[0002] Circularly polarized antennas, due to their unique electromagnetic wave properties, offer significant advantages in long-distance transmission and interference resistance. Circularly polarized waves can effectively penetrate the ionosphere and are unaffected by the Faraday effect of the Earth's magnetic field. Consequently, they are widely used in satellite communications, radar monitoring, and wireless base stations. In particular, in the Beidou satellite navigation system, circularly polarized antennas, as core signal reception components, directly determine the system's ability to capture weak signals and its interference resistance.

[0003] With the trend toward miniaturization and integration of electronic devices, the spacing between antenna elements in the Beidou system continues to shrink, significantly increasing the mutual coupling effect between elements. Mutual coupling disrupts the independence of antenna port signals, reduces the output signal-to-noise ratio, and thus weakens the system's anti-interference performance. Research has shown that the primary reason for the Beidou system's reduced anti-interference capability is that the inter-antenna coupling energy disrupts the phase balance of the circularly polarized orthogonal modes, resulting in received signal distortion. Therefore, achieving efficient decoupling within a limited space has become a key technical challenge in improving the performance of Beidou antenna front-ends.

[0004] Currently, there are significant gaps in research on the decoupling of circularly polarized antennas. Unlike linearly polarized antennas, circular polarization consists of two orthogonal linear polarization components with a 90° phase difference. Traditional decoupling methods struggle to simultaneously suppress the coupling of these two polarization components. For example, increasing the element spacing can alleviate mutual coupling, but this conflicts with the need for compact arrays. While electromagnetic bandgap (EBG) structures can suppress surface waves, their complex three-dimensional design increases profile height and processing costs.

[0005] To address the above issues, the present invention conducts an in-depth analysis of the amplitude and phase characteristics of the circular polarization coupling path and proposes an improved solution based on the mode cancellation method. By extending the linear polarization decoupling theory to the field of circular polarization and combining the collaborative design of the "J"-shaped patch, strip patch, and short-circuit probe, the synchronous cancellation of the dual-polarization components is achieved in a limited space. This method not only adapts to the high-density layout requirements of the Beidou array, but also maintains a low axial ratio and high isolation within a wide bandwidth, providing an innovative solution for improving the anti-interference performance of the Beidou system. Summary of the Invention

[0006] The purpose of the present invention is to provide a low-profile, high-isolation circularly polarized microstrip antenna decoupling structure, which significantly reduces the mutual coupling effect between units and improves the radiation performance of the antenna by optimizing the coupling path and impedance matching.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The decoupling structure between the circularly polarized microstrip antennas consists of a microstrip radiation structure and a decoupling structure. The microstrip radiation structure includes two symmetrically distributed square metal radiation patches (1), a dielectric substrate (2), a floor (3) and a coaxial line (4). The decoupling structure is composed of a "J"-shaped patch (5), two strip patches (6) and five short-circuit probes (7). The two square radiation patches (1) are connected by the "J"-shaped patch (5), the strip patch (6) extends to the edge of the patch, and the short-circuit probe (7) penetrates the dielectric substrate (2), and directional cancellation of coupling energy is achieved by adjusting the surface current distribution.

[0009] The innovation of the present invention is:

[0010] The pattern cancellation method realizes the decoupling of circularly polarized antennas: through the joint action of the "J"-shaped patch (5), the strip patch (6) and the five short-circuit probes (7), the synchronous cancellation of the co-polarization and cross-polarization components is achieved, and the isolation between the compact circularly polarized microstrip antenna arrays is improved by about 10dB, and the influence of the mutual coupling effect on the radiation pattern is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a top view of the overall structure, marking the sizes and positions of two square metal radiation patches (1), dielectric substrate (2), floor (3), coaxial line (4), "J" shaped patch (5), strip patch (6) and short-circuit probe (7).

[0012] Figure 2 This is a top view of the decoupling structure, marking the size and position of the "J"-shaped patch (5), the strip patch (6) and the short-circuit probe (7).

[0013] Figure 3 It is a cross-sectional view showing the layered structure of a square metal radiation patch (1) and a dielectric substrate (2) and the details of the short-circuit probe (7) passing through.

[0014] Figure 4 is the measured S parameter. DETAILED DESCRIPTION

[0015] In order to make the objectives, technical solutions and innovations of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.

[0016] The present invention relates to a decoupling structure between circularly polarized microstrip antennas, primarily consisting of a microstrip radiating structure and a decoupling structure. The microstrip radiating structure includes two square metal radiating patches, a dielectric substrate, a ground plane, and a coaxial line; the decoupling structure is composed of a "J"-shaped patch, two strip-shaped patches, and five short-circuit probes.

[0017] In the microstrip radiator structure, two square metal radiating patches are symmetrically arranged on the top layer of a dielectric substrate. The patches have a side length of 56 mm and a 4 mm edge-to-edge spacing of 0.017λ (λ is the center frequency wavelength). A floor covering the bottom layer of the dielectric substrate is grounded via the outer conductor of a coaxial cable, with the inner conductor passing through the floor to connect to the radiating patches. The dielectric substrate is a rectangular parallelepiped with lateral dimensions of 56 mm x 56 mm. It has a relative permittivity of 4.4, a relative permeability of 1, a loss tangent of 0.02, and a height of 2 mm.

[0018] In the decoupling structure, a "J"-shaped patch is positioned between and connected to the two radiating patches. The "J"-shaped patch is symmetrical, with the horizontal patch on top measuring 1mm long and 0.5mm wide, and a 0.5mm diameter shorting probe connected to the center. The vertical patches on either side of the "J" are 23mm long and 0.5mm wide, and the ends of the "J" are connected to the metal radiating patches. Two strip-shaped patches are symmetrical, each measuring 20mm long and 1mm wide. Shorting probes with a diameter of 0.8mm are connected to the first and second ends of each strip. Five shorting probes, each 0.8mm in diameter, extend through the dielectric substrate, located at the center of the "J"-shaped patch and at the ends of the two strips. They are used to regulate the surface current of the decoupling structure.

[0019] This invention, guided by the pattern cancellation method, targets circularly polarized microstrip antennas and introduces a decoupling structure to achieve coupling cancellation between two radiating elements. Specifically, a "J"-shaped patch, a strip patch, and five short-circuit probes work together to guide and adjust the propagation path of electromagnetic waves, causing the coupled energy between the two radiating elements to cancel each other out at specific locations and directions. This pattern cancellation method can effectively reduce the strong mutual coupling between closely spaced circularly polarized microstrip antennas, thereby improving the antenna's radiation performance and enhancing its isolation and directivity.

[0020] Based on the aforementioned decoupling structure design, the present invention achieves efficient decoupling in a compact layout. Specifically, it maintains a low axial ratio and high isolation across a wide bandwidth, achieving an approximately 10dB improvement in isolation between compact circularly polarized microstrip antenna arrays while minimizing the impact of mutual coupling on the radiation pattern. This makes the present invention highly applicable in systems such as satellite communications, effectively improving the system's anti-interference performance and signal reception capabilities.

Claims

1. A decoupling structure between circularly polarized microstrip antennas, comprising a microstrip radiation structure and a decoupling structure, characterized in that: The microstrip radiation structure comprises two square metal radiation patches (1), a dielectric substrate (2), a floor (3), and a coaxial line (4); the decoupling structure is composed of a "J"-shaped patch (5), two strip-shaped patches (6), and five short-circuit probes (7).

2. The radiation structure of the circularly polarized microstrip antenna according to claim 1, characterized in that: The two square metal radiation patches (1) are symmetrically distributed on the top layer of the dielectric substrate (2), the patch side length is 56 mm, and the distance between the two patch edges is 4 mm, that is, 0.017λ (λ is the center frequency wavelength); the floor (3) covers the bottom layer of the dielectric substrate (2), is grounded through the outer conductor of the coaxial line (4), and the inner conductor passes through the floor (3) and is connected to the radiation patch (1).

3. The decoupling structure between circularly polarized microstrip antennas according to claim 1, wherein: The "J"-shaped patch (5) is located between the two radiating patches and is connected to the two radiating patches; the strip patch width (6) is 1 mm and the length is 20 mm; the five short-circuit probes (7) penetrate the dielectric substrate (2) and are respectively located at the center of the "J"-shaped patch (5) and the ends of the two strip patches (6); the probes have a diameter of 0.8 mm and are used to adjust the surface current of the decoupling structure.

4. The decoupling structure between circularly polarized microstrip antennas according to claim 1, wherein: The antenna unit has a lateral dimension of 90 mm×150 mm and a cross-sectional height of 3 mm.

5. The radiation structure between circularly polarized microstrip antennas according to claim 1 or claim 2, characterized in that: The two square metal radiation patches (1) are designed in a rectangular shape with a horizontal dimension of 56 mm×56 mm. The dielectric substrate (2) is designed in a rectangular shape with a horizontal dimension of 90 mm×150 mm, a relative dielectric constant of 4.4, a relative magnetic permeability of 1, a loss tangent of 0.02, and a height of 2 mm.

6. The decoupling structure between circularly polarized microstrip antennas according to claim 1 or claim 2, characterized in that: The "Ji"-shaped patch (5) is a bilaterally symmetrical structure. The horizontal patch on the top of the "Ji" is 1mm long and 0.5mm wide, and is connected to a short-circuit probe (7) in the center, with a probe diameter of 0.5mm. The vertical patches on both sides of the "Ji" are 23mm long and 0.5mm wide. The two ends of the "Ji" are connected to the metal radiation patch (1). The two strip-shaped patches (6) are a vertically symmetrical structure. Each strip-shaped patch is 20mm long and 1mm wide. The ends of each strip-shaped patch are connected to a short-circuit probe (7), with a probe diameter of 0.8mm.

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