Low cross-polarization microstrip patch antenna with a defective ground structure

Abstract

This invention discloses a low cross-polarization microstrip patch antenna with a defective grounding structure. A metal radiating patch is attached to the upper surface of a dielectric substrate. A metal grounding layer is attached to the lower surface of the dielectric substrate. The outer conductor of the feed interface is connected to the metal grounding layer, and the inner conductor of the feed interface penetrates the metal grounding layer and the dielectric substrate to connect to the metal radiating patch. The metal grounding layer includes: a square metal ring, multiple metal patch units, and polygonal metal patches; the polygonal metal patches are disposed within the square metal ring, and multiple metal patch units are disposed between the square metal ring and the polygonal metal patches. The metal patch units are composed of metal patches arranged in a photonic crystal structure. This invention improves the current distribution on the antenna ground plane, resulting in stronger field symmetry around the radiating patch, greatly improving the cross-polarization level of traditional microstrip patch antennas and increasing the flexibility of antenna design.

Description

Technical Field

[0001] This invention relates to a low cross-polarization microstrip patch antenna with a defective grounding structure, belonging to the field of microstrip antenna technology. Background Technology

[0002] Microstrip patch antennas are currently widely used antennas due to their advantages such as small size, low profile, and easy conformal design. Traditional microstrip patch antennas consist of a dielectric substrate, a ground plane covering its surface, and a radiating plate, using a microstrip line or coaxial probe as the feed structure. However, these antennas have some inherent performance drawbacks, such as low gain, narrow bandwidth, and high cross-polarization.

[0003] Larger cross-polarization not only reduces the radiation efficiency of the antenna's main polarization but also leads to additional noise signals received by the antenna, affecting the system noise figure. Cross-polarization in microstrip patch antennas originates from two sources: the edge field distributed along the non-radiating edge when the radiating patch operates in the fundamental mode TM10, and higher-order antenna modes whose polarization direction is perpendicular to the main mode's polarization direction. In practical applications, the feeding structure of microstrip patch antennas is often asymmetrical; for example, a coaxial probe may be biased towards one side of the radiating edge. Consequently, the antisymmetric magnetic currents are not completely canceled out, resulting in higher cross-polarization components in the far field, especially in the H-plane.

[0004] Defective grounding structures are a classic approach to reducing cross-polarization in microstrip patch antennas. By introducing different defect structures into the grounding structure, they effectively suppress edge fields and higher-order modes on the non-radiating side. However, most existing defective structures cannot simultaneously satisfy symmetry and continuity in both the E-plane and H-plane. Furthermore, existing centrosymmetric defective structures have limited control over the ground surface current, thus failing to further reduce the cross-polarization level.

[0005] Therefore, how to improve the shortcomings of existing defective grounding structures is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] Objective: In order to overcome the shortcomings of the prior art, the present invention provides a low cross-polarization microstrip patch antenna with a defective grounding structure. The present invention introduces a photonic crystal structure into the metal grounding of the microstrip patch antenna.

[0007] Technical solution: To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A low cross-polarization microstrip patch antenna with a defective grounding structure includes a metal radiating plate, a dielectric substrate, a metal grounding layer, and a feed interface.

[0009] The metal radiating sheet is attached to the upper surface of the dielectric substrate to radiate electromagnetic wave energy.

[0010] The metal grounding layer is attached to the lower surface of the dielectric substrate to support the antenna body and provide a grounding signal.

[0011] The outer conductor of the power supply interface is connected to the metal grounding layer, and the inner conductor of the power supply interface penetrates the metal grounding layer and the dielectric substrate to connect to the metal radiating plate for inputting radio frequency signals.

[0012] Preferably, the metal grounding layer includes: a square metal ring, multiple metal sheet units, and polygonal metal sheets; the polygonal metal sheets are disposed inside the square metal ring, and multiple metal sheet units are disposed between the square metal ring and the polygonal metal sheets, wherein the metal sheet units are composed of metal sheets arranged in a photonic crystal structure.

[0013] Preferably, the polygonal metal sheet includes: a square metal sheet, on which four rectangular metal sheets are connected, the four rectangular metal sheets being arranged symmetrically about the center of the square metal sheet.

[0014] Preferably, the metal grounding layer has a centrally symmetrical structure.

[0015] Preferably, the square metal ring and the polygonal metal sheet are not connected, and the multiple metal sheet units are not connected to each other. A metal sheet unit is provided in the defect region between the inner side of the square metal ring and the outer side of the polygonal metal sheet. The metal sheets, arranged in a photonic crystal structure, further adjust the field distribution in the defect region to achieve low cross-polarization of the antenna, ensuring symmetry in the current distribution on the metal ground layer.

[0016] Preferably, the metal sheets arranged in a photonic crystal structure are evenly spaced within the defect region, and their initial positions are set as the four diagonal regions of the inner edge of a square metal ring. This ensures that the metal grounding layer satisfies symmetry and has the same structure in both the vertical and horizontal directions, achieving symmetry and continuity in both the E-plane and H-plane of the antenna structure.

[0017] Preferably, the power supply interface is a coaxial power supply interface, and the inner conductor of the coaxial power supply interface passes above the center of the metal grounding layer.

[0018] Preferably, the metal sheets arranged in a photonic crystal structure are set in a centrally symmetrical shape, such as the metal sheets being circular or square.

[0019] Beneficial Effects: This invention provides a low-cross-polarization microstrip patch antenna with a defective grounding structure. Photonic crystals are artificially designed structures with periodic dielectric structures, which can effectively control electromagnetic wave propagation. This invention improves the current distribution on the antenna ground plane by adjusting the size, spacing, and position of multiple periodically arranged metal sheets in the photonic crystal structure, resulting in a strong central symmetry in the antenna field distribution and effectively reducing antenna cross-polarization, especially in the H-plane. Furthermore, the periodicity of the photonic crystal structure ensures symmetry and structural uniformity in both the vertical and horizontal directions on the antenna ground plane, thereby guaranteeing symmetry and continuity of the antenna structure in the E-plane and H-plane. In addition, this invention offers high design freedom, requires no additional components, has low fabrication difficulty, and is easy to implement.

[0020] In the low cross-polarization microstrip patch antenna of this invention, the field originally concentrated at the edge corner is weakened by being partially coupled to the resonant defects in the photonic crystal structure, thereby suppressing the generation of high cross-polarization. By adjusting the size, spacing, and initial position of the metal sheets, the current distribution on the antenna ground plane is improved, resulting in stronger symmetry in the field around the radiating patch. This greatly improves the cross-polarization level of traditional microstrip patch antennas and increases the flexibility of antenna design. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of an embodiment of a low cross-polarization microstrip patch antenna with a defective grounding structure according to the present invention.

[0022] Figure 2 This is an exploded view of a low cross-polarization microstrip patch antenna with a defective grounding structure according to the present invention.

[0023] Figure 3 This is a schematic diagram of the structure of the metal grounding layer.

[0024] Figure 4 This is a schematic diagram of another embodiment of a low cross-polarization microstrip patch antenna with a defective grounding structure according to the present invention.

[0025] Figure 5 This is a schematic diagram of the structure of a traditional microstrip patch antenna.

[0026] Figure 6 The diagram shows the reflection coefficients of the low cross-polarization microstrip patch antenna and the comparative microstrip patch antenna in this invention.

[0027] Figure 7 The diagrams show the main polarization and cross-polarization patterns of the low cross-polarization microstrip patch antenna and the comparative microstrip patch antenna in this invention.

[0028] Figure 8This is a diagram showing the main polarization and cross-polarization patterns on the H-plane of the antenna under different circular metal sheet sizes in this invention.

[0029] Figure 9 This is a ground plane current distribution diagram of the low cross-polarization microstrip patch antenna in this invention and a traditional microstrip patch antenna. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0031] The present invention will be further described below with reference to specific embodiments.

[0032] Example 1

[0033] The microstrip patch antenna structure in this embodiment is as follows:

[0034] like Figure 1 As shown, a low cross-polarization microstrip patch antenna with a defective grounding structure includes a metal radiating sheet 1, a dielectric substrate 2, a metal grounding layer 3, and a feed interface 4.

[0035] The metal radiating sheet 1 is attached to the upper surface of the dielectric substrate 2 to radiate electromagnetic wave energy.

[0036] The metal grounding layer 3 is attached to the lower surface of the dielectric substrate 2 and is used to support the antenna body and provide a grounding signal.

[0037] The outer conductor of the power supply interface 4 is connected to the metal grounding layer 3, and the inner conductor of the power supply interface penetrates the metal grounding layer 3 and the dielectric substrate 2 to connect to the metal radiating plate 1 for inputting radio frequency signals.

[0038] like Figure 2 As shown, the metal grounding layer 3 includes: a square metal ring 5, multiple metal sheet units 6, and polygonal metal sheets 7; the polygonal metal sheets 7 are disposed inside the square metal ring 5, and multiple metal sheet units 6 are disposed between the square metal ring 5 and the polygonal metal sheets 7, wherein the metal sheet units 6 are composed of metal sheets arranged in a photonic crystal structure.

[0039] In a further embodiment, the polygonal metal sheet 7 includes: a square metal sheet, on which four rectangular metal sheets are connected, the four rectangular metal sheets being arranged symmetrically about the center of the square metal sheet.

[0040] Furthermore, in one embodiment, the metal grounding layer 3 has a centrally symmetrical structure.

[0041] Furthermore, in one embodiment, the square metal ring 5 and the polygonal metal sheet 7 are not connected, and the plurality of metal sheet units 6 are not connected to each other. A metal sheet unit is provided in the defect region between the inner side of the square metal ring 5 and the outer side of the polygonal metal sheet 7. The metal sheets, arranged in a photonic crystal structure, further adjust the field distribution in the defect region to achieve low cross-polarization of the antenna, ensuring symmetry in the current distribution on the metal ground layer.

[0042] Furthermore, in one embodiment, metal sheets arranged in a photonic crystal structure are equally spaced within the defect region, and their initial positions are set at the four diagonal regions of the inner edge of the square metal ring 5. This ensures that the metal grounding layer satisfies symmetry and has the same structure in both the vertical and horizontal directions, thereby achieving symmetry and continuity of the antenna structure in both the E-plane and H-plane.

[0043] In another embodiment, the power supply interface 4 is a coaxial power supply interface, with the inner conductor of the coaxial power supply interface passing above the center of the metal grounding layer.

[0044] In another embodiment, the metal sheets arranged in a photonic crystal structure are configured in a centrally symmetrical shape, such as the metal sheets being circular or square.

[0045] Example 2:

[0046] This embodiment describes one example of a low-cross-polarization microstrip patch antenna with a defective grounding structure, such as... Figure 3 As shown, the dielectric substrate 2 is a square substrate made of RT5870 material (dielectric constant of 2.33 and loss angle of 0.001). The size of the dielectric substrate is 50mm×50mm×1.575mm, and the size of the metal radiating plate 1 is 14.22mm×14.22mm. The size of the dielectric substrate and the metal radiating plate can be changed according to the change of the operating frequency.

[0047] The metal radiating plate 1 and the metal grounding layer 3 are respectively attached to the upper and lower surfaces of the dielectric substrate 2. The metal radiating plate 1 is placed at the center of the dielectric substrate 2. The operating frequency of the microstrip patch antenna is mainly determined by the side length of the metal radiating plate 1 and the material parameters of the dielectric substrate 2.

[0048] The metal radiating plate 1 is used to radiate electromagnetic wave energy, and the metal grounding layer 3 is used to provide a grounding signal. The square metal ring 5 is located on the outermost layer; the polygonal metal plate 7 is located on the innermost layer; and four metal plate units 6 are located in the defect area between the inner side of the square metal ring 5 and the outer side of the polygonal metal plate 7. The inner conductor of the feed interface 4 passes through the dielectric substrate 2 and connects to the metal radiating plate 1 for inputting radio frequency signals.

[0049] The center of the feed interface 4 is located 2.45 mm above the horizontal plane from the center of the antenna, and the inner conductor diameter is 1.3 mm. The circumferential spacing of the square metal ring 5 is 2.89 mm. The polygonal metal plate 7 consists of four rectangular metal plates and one square metal plate. The four centrally symmetrically arranged rectangular metal plates are connected to the center of the four sides of the square metal plate. The rectangular metal plates are 4 mm × 8 mm in size, and the square metal plate is 26.22 mm × 26.22 mm in size. The defect area formed by the square metal ring 5 and the polygonal metal plate 7 makes the current distribution on the antenna metal ground layer symmetrical, reducing antenna cross-polarization.

[0050] Four circular metal plates 8 form the initial arrangement of the metal plate unit 6. The centers of these initial metal plates are located 5.4 mm horizontally and vertically from the outer edge of the square metal ring 5. Multiple periodically arranged circular metal plates are evenly spaced along the inner edge of the square metal ring 5 and the outer edge of the polygonal metal plate 7, with a spacing of 4 mm between adjacent circular metal plates and a diameter of 3.6 mm. These periodically arranged circular metal plates optimize the field distribution in the defect region formed by the square metal ring 5 and the polygonal metal plate 7. The photonic crystal structure exhibited by these periodically arranged circular metal plates prevents some electromagnetic waves from propagating within the defect region, thereby reducing the electric field distribution at the antenna edge and achieving the goal of reducing antenna cross-polarization. Adjusting the spacing, size, and initial position of the metal plates can change the surface current distribution of the grounding layer, effectively adjusting the antenna's cross-polarization level.

[0051] Example 3:

[0052] This embodiment describes one example of a low-cross-polarization microstrip patch antenna with a defective grounding structure, such as... Figure 4 As shown, the dielectric substrate 2 is a square substrate made of RT5870 material (dielectric constant of 2.33 and loss angle of 0.001). The size of the dielectric substrate is 50mm×50mm×1.575mm, and the size of the metal radiating plate 1 is 14.22mm×14.22mm. The size of the dielectric substrate and the metal radiating plate can be changed according to the change of the operating frequency.

[0053] In the second metal ground layer 9, the size, spacing, and position of the second circular metal sheet 10 have changed compared to that in Embodiment 2, resulting in an increase in the number of cycles of the metal sheet unit, from 2 rows to 3 rows. The remaining structure is the same as in Embodiment 2. The increase in the number of cycles of the circular metal sheet can also further reduce the cross polarization on the H-plane of the antenna, increasing the flexibility of antenna design.

[0054] Example 4:

[0055] This embodiment describes a comparative experiment between the comparative example and Example 2, specifically including: Figure 5 As shown, the comparative microstrip patch antenna includes a metal radiating plate 1', a dielectric substrate 2', a metal ground layer 3', and a feed interface 4'. The metal radiating plate 1' and the metal ground layer 3' are respectively attached to the upper and lower surfaces of the dielectric substrate 2', with the metal radiating plate 1' positioned at the center of the dielectric substrate 2'. The inner conductor of the feed interface 4' passes through the dielectric substrate 2' and connects to the metal radiating plate 1' to input radio frequency signals. The metal ground layer 3' in the comparative example uses a metal sheet structure, and the antenna in the comparative example has the same physical dimensions as that in Example 1.

[0056] like Figure 6 As shown, the reflection coefficient S11 of the low cross-polarization microstrip patch antenna in Example 2 and the microstrip patch antenna in the comparative example are both less than -10dB in the range of 6.2GHz-6.3GHz. The introduction of the defective grounding structure did not affect the antenna's operating frequency of 6.25GHz.

[0057] like Figure 7 As shown, the low cross-polarization microstrip patch antenna of Example 2 significantly improves the cross-polarization levels in both the E-plane and H-plane without affecting the main polarization pattern. In the E-plane, the isolation between the main polarization and cross-polarization of the antenna in Example 2 remains above 30 dB; in the H-plane, compared to the comparative microstrip patch antenna, the peak isolation between the main polarization and cross-polarization of the antenna in Example 1 is improved by approximately 15 dB. The total gain of the antenna in Example 2 is 7 dBi, while the total gain of the comparative microstrip patch antenna is 7.5 dBi. The defective grounding structure of this invention does not significantly affect the total antenna gain, while greatly reducing the cross-polarization of the antenna.

[0058] like Figure 8 As shown, the cross-polarization level of the low cross-polarization microstrip patch antenna of the present invention is affected by the size of the circular metal plate on the ground plane. When the diameter of the circular metal plate is 3.2 mm, 3.4 mm, and 3.6 mm, for every 0.2 mm increase in the diameter of the circular metal plate, the peak isolation of the main polarization and cross-polarization of the antenna in Example 1 increases by approximately 5 dB. Preferably, the larger the diameter of the circular metal plate, the lower the cross-polarization of the antenna while the main polarization level remains unchanged. The cross-polarization level of the antenna of the present invention can be adjusted by adjusting the size of the circular metal plate on the ground plane, increasing the design flexibility.

[0059] like Figure 9 As shown, the metal grounding layer of the low cross-polarization microstrip patch antenna of the present invention effectively improves the current distribution of the metal grounding plane of the comparative microstrip patch antenna, giving the antenna field distribution extremely strong symmetry and achieving an improvement in the cross-polarization level on the H-plane.

[0060] Compared to existing microstrip patch antenna designs and embodiments, this invention improves the metal grounding structure. This structure satisfies symmetry and is structurally identical in both the vertical and horizontal directions, enabling the antenna structure to simultaneously satisfy symmetry and continuity in both the E-plane and H-plane. Furthermore, it significantly suppresses cross-polarization on the H-plane, making it suitable for dual-polarization wireless communication systems. Additionally, the circular metal sheet of the photonic crystal structure within the metal grounding layer allows for more flexible adjustment of the antenna's radiation characteristics. Because the electric field in this invention is concentrated in the defect center region of the photonic crystal structure, the edge field strength is reduced, and the overall electric field distribution exhibits stronger symmetry, resulting in an improvement of over 10 dB in cross-polarization level on the H-plane.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low cross-polar microstrip patch antenna with a defective ground structure, characterized by: The device includes a metal grounding layer, which comprises: a square metal ring, multiple metal sheet units, and polygonal metal sheets; the polygonal metal sheets are disposed within the square metal ring, and multiple metal sheet units are disposed between the square metal ring and the polygonal metal sheets, wherein the metal sheet units are composed of metal sheets arranged in a photonic crystal structure; The polygonal metal sheet includes: a square metal sheet, on which four rectangular metal sheets are connected, and the four rectangular metal sheets are arranged symmetrically about the center of the square metal sheet; The square metal ring and the polygonal metal sheet are not connected, and the multiple metal sheet units are not connected to each other. A metal sheet unit is provided in the defect area between the inner side of the square metal ring and the outer side of the polygonal metal sheet.

2. The low cross-polarization microstrip patch antenna with a defective grounding structure according to claim 1, characterized in that: Also includes: Metal radiating sheet, dielectric substrate, and power supply interface; The metal radiating sheet is attached to the upper surface of the dielectric substrate for radiating electromagnetic wave energy; The metal grounding layer is attached to the lower surface of the dielectric substrate; The outer conductor of the power supply interface is connected to the metal grounding layer, and the inner conductor of the power supply interface penetrates the metal grounding layer and the dielectric substrate to connect to the metal radiating plate for inputting radio frequency signals.

3. The low cross-polarization microstrip patch antenna with a defective grounding structure according to claim 1, characterized in that: The metal grounding layer has a centrally symmetrical structure.

4. The low cross-polar microstrip patch antenna with a defective ground structure according to claim 1, characterized in that: Metal sheets arranged in a photonic crystal structure are evenly spaced within the defect region, and their initial positions are set as the four diagonal regions of the inner edge of a square metal ring.

5. A low-cross-polarization microstrip patch antenna with a defective grounding structure according to claim 2, characterized in that: The power supply interface adopts a coaxial cable power supply interface, and the inner conductor of the coaxial cable power supply interface passes through the center of the metal grounding layer.

6. The low cross-polar microstrip patch antenna with a defective ground structure according to claim 1, characterized in that: The metal sheets arranged in a photonic crystal structure are set in a centrosymmetric shape.

7. The low cross-polar microstrip patch antenna with a defective ground structure according to claim 6, characterized in that: The metal sheet is designed to be circular.

8. The low cross-polar microstrip patch antenna with a defective ground structure according to claim 6, characterized in that: The metal sheet is set as a square.

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