Low cross polarization microstrip patch antenna with defected grounding structure

Abstract

The invention discloses a low cross polarization microstrip patch antenna with a defected grounding structure. A metal radiation sheet is attached to the upper surface of a dielectric substrate. The metal grounding layer is attached to the lower surface of the dielectric substrate. An outer conductor of the feed interface is connected with the metal grounding layer, and an inner conductor of the feed interface penetrates through the metal grounding layer and the dielectric substrate and is connected to the metal radiation sheet. The metal grounding layer comprises a square metal ring, a plurality of metal sheet units and a polygonal metal sheet; a polygonal metal sheet is arranged in the square metal ring, a plurality of metal sheet units are arranged between the square metal ring and the polygonal metal sheet, and each metal sheet unit is composed of metal sheets arranged in a photonic crystal structure. According to the invention, the current distribution on the grounding plane of the antenna is improved, so that the field around the radiation patch generates strong symmetry, the cross polarization level of the traditional microstrip patch antenna is greatly improved, and the flexibility of the antenna design is increased.

Description

Technical Field

[0001] The present invention relates to a low cross-polarization microstrip patch antenna with a defected ground structure, belonging to the technical field of microstrip antennas. Background Art

[0002] Microstrip patch antennas are currently widely used antennas, which have the advantages of small size, low profile, and easy conformal. Traditional microstrip patch antennas are composed of a dielectric substrate, a ground plane covering its surface, and a radiation patch, and use a microstrip line or a coaxial probe as the feeding structure. However, such antennas have some inherent defects in performance, such as low gain, narrow bandwidth, and relatively high cross polarization.

[0003] Larger cross polarization not only reduces the radiation efficiency of the main polarization of the antenna, but also causes the antenna to receive additional noise signals, affecting the system noise figure. There are two sources of cross polarization in microstrip patch antennas, namely the edge field distributed along the non-radiating edge when the radiation patch operates in the fundamental mode TM10 and the higher-order mode of the antenna whose polarization direction is perpendicular to the main mode polarization direction. In practical applications, the feeding structure of microstrip patch antennas is usually asymmetric. For example, the coaxial probe will be biased towards one side of the radiation edge. Thus, the anti-symmetric magnetic current will not be completely cancelled, and then a relatively high cross-polarization component will be caused in the far field, especially in the H plane.

[0004] The defected ground structure is a classic structure for reducing the cross polarization of microstrip patch antennas. By introducing different defect structures in the ground structure, the edge field of the non-radiating edge and the higher-order modes are effectively suppressed. However, the vast majority of existing defect structures cannot simultaneously satisfy the symmetry and continuity in both the E plane and the H plane. In addition, the existing centrosymmetric defect structures have limited control ability over the surface current of the ground plane and cannot further reduce the cross polarization level.

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

[0006] Objective: In order to overcome the deficiencies in the prior art, the present invention provides a low cross-polarization microstrip patch antenna with a defected ground structure. The present invention introduces a photonic crystal structure into the metal ground 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 defected ground structure includes a metal radiation patch, a dielectric substrate, a metal ground layer, and a feeding interface.

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

[0010] The metal ground layer is attached to the lower surface of the dielectric substrate for carrying the antenna body and providing a ground signal.

[0011] The outer conductor of the feeding interface is connected to the metal ground layer, and the inner conductor of the feeding interface penetrates through the metal ground layer and the dielectric substrate to be connected to the metal radiation sheet for inputting radio frequency signals.

[0012] Preferably, the metal ground layer includes: a square metal ring, a plurality of metal sheet units, and a polygonal metal sheet; the polygonal metal sheet is arranged inside the square metal ring, and a plurality of metal sheet units are arranged between the square metal ring and the polygonal metal sheet, and 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, and four rectangular metal sheets are connected to the square metal sheet, and the four rectangular metal sheets are symmetrically arranged around the center of the square metal sheet.

[0014] Preferably, the metal ground layer has a centrosymmetric structure.

[0015] Preferably, the square metal ring and the polygonal metal sheet are not connected, the plurality of metal sheet units are not connected, and metal sheet units are arranged in the defect area between the inner side of the square metal ring and the outer side of the polygonal metal sheet. The defect area is used to make the current distribution on the metal ground layer have symmetry, and the metal sheets arranged in a photonic crystal structure further adjust the field distribution in the defect area to achieve low cross-polarization of the antenna.

[0016] Preferably, the metal sheets arranged in a photonic crystal structure are equidistantly arranged in the defect area, and the initial positions are set at the four diagonal areas of the inner edge of the square metal ring. This is used to ensure that the metal ground layer satisfies symmetry and has the same structure in both the vertical and horizontal directions, so that the antenna structure can simultaneously meet the symmetry and continuity in both the E-plane and the H-plane.

[0017] Preferably, the feeding interface adopts a coaxial feeding interface, and the inner conductor of the coaxial feeding interface passes above the center of the metal ground layer.

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

[0019] Beneficial effects: The low cross-polarization microstrip patch antenna with a defective ground structure provided by the present invention. Photonic crystals are a type of artificially designed periodic dielectric structure that can effectively control the propagation of electromagnetic waves. By adjusting the size, spacing, and position of multiple periodically arranged metal sheets in the photonic crystal structure, the present invention improves the current distribution on the antenna ground plane, making the antenna field distribution have strong central symmetry, effectively reducing the antenna cross-polarization, especially in the H-plane. In addition, the periodic characteristics of the photonic crystal structure can satisfy the symmetry and the same structure in both the vertical and horizontal directions on the antenna ground plane, thereby ensuring the symmetry and continuity of the antenna structure in the E-plane and H-plane. In addition, the present invention has a high degree of design freedom, does not require additional components, has a low processing difficulty, and is easy to implement.

[0020] In the low cross-polarization microstrip patch antenna of the present invention, the fields originally concentrated at the edge corners are weakened because they are 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, making the fields around the radiation patch have strong symmetry, greatly improving the cross-polarization level of the traditional microstrip patch antenna, and increasing the flexibility of antenna design. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of an embodiment of a low cross-polarization microstrip patch antenna with a defective ground structure of the present invention.

[0022] Figure 2 It is an exploded schematic diagram of a low cross-polarization microstrip patch antenna with a defective ground structure of the present invention.

[0023] Figure 3 It is a schematic structural diagram of the metal ground layer.

[0024] Figure 4 It is a schematic structural diagram of another embodiment of a low cross-polarization microstrip patch antenna with a defective ground structure of the present invention.

[0025] Figure 5 It is a schematic structural diagram of a traditional microstrip patch antenna.

[0026] Figure 6 It is a reflection coefficient diagram of the low cross-polarization microstrip patch antenna and the comparative microstrip patch antenna in the present invention.

[0027] Figure 7 It is the main polarization and cross-polarization pattern diagrams of the low cross-polarization microstrip patch antenna and the comparative microstrip patch antenna in the present invention.

[0028] Figure 8This is the main polarization and cross - polarization patterns in the H - plane of the antenna under different sizes of circular metal sheets in the present invention.

[0029] Figure 9 This is the ground - plane current distribution diagrams of the low - cross - polarization microstrip patch antenna and the traditional microstrip patch antenna in the present invention. Detailed implementation manners

[0030] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present invention.

[0031] Next, the present invention will be further described in combination with specific embodiments.

[0032] Embodiment 1

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

[0034] As Figure 1 shown, a low - cross - polarization microstrip patch antenna with a defected ground structure includes a metal radiation patch 1, a dielectric substrate 2, a metal ground layer 3, and a feed interface 4.

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

[0036] The metal ground layer 3 is attached to the lower surface of the dielectric substrate 2 for carrying the antenna body and providing a ground signal.

[0037] The outer conductor of the feed interface 4 is connected to the metal ground layer 3, and the inner conductor of the feed interface penetrates through the metal ground layer 3 and the dielectric substrate 2 to be connected to the metal radiation patch 1 for inputting radio - frequency signals.

[0038] As Figure 2 shown, among them, the metal ground layer 3 includes: a square metal ring 5, a plurality of metal sheet units 6, and a polygonal metal sheet 7; the polygonal metal sheet 7 is arranged inside the square metal ring 5, and a plurality of metal sheet units 6 are arranged between the square metal ring 5 and the polygonal metal sheet 7, and the metal sheet units 6 are composed of metal sheets arranged in a photonic crystal structure.

[0039] Furthermore, in one embodiment, the polygonal metal sheet 7 includes: a square metal sheet, and four rectangular metal sheets are connected to the square metal sheet, and the four rectangular metal sheets are symmetrically arranged around the center of the square metal sheet.

[0040] Further, in one embodiment, the metal ground layer 3 has a centrosymmetric structure.

[0041] Further, in one embodiment, the square metal ring 5 and the polygonal metal sheet 7 are not connected, and the multiple metal sheet units 6 are not connected. Metal sheet units are arranged in the defect area between the inner side of the square metal ring 5 and the outer side of the polygonal metal sheet 7. The defect area is used to make the current distribution on the metal ground layer symmetric, and the metal sheets arranged in a photonic crystal structure further adjust the field distribution in the defect area to achieve low cross-polarization of the antenna.

[0042] Further, in one embodiment, the metal sheets arranged in a photonic crystal structure are equally spaced in the defect area, and the initial positions are set at the four diagonal areas of the inner edge of the square metal ring 5. This is used to ensure that the metal ground layer satisfies symmetry and has the same structure in both the vertical and horizontal directions, so that the antenna structure can satisfy symmetry and continuity in both the E-plane and the H-plane simultaneously.

[0043] Further, in one embodiment, the feeding interface 4 uses a coaxial feeding interface, and the inner conductor of the coaxial feeding interface passes through above the center of the metal ground layer.

[0044] Further, in one embodiment, the metal sheets arranged in a photonic crystal structure are set to have a centrosymmetric shape, such as circular or square.

[0045] Embodiment 2:

[0046] This embodiment introduces an embodiment of a low cross-polarization microstrip patch antenna with a defected ground structure, as Figure 3 shown. The dielectric substrate 2 is a square substrate made of RT5870 material (dielectric constant is 2.33, loss tangent is 0.001), with a size of 50 mm × 50 mm × 1.575 mm. The size of the metal radiation patch 1 is 14.22 mm × 14.22 mm, and the sizes of the dielectric substrate and the metal radiation patch can be changed according to the change of the operating frequency.

[0047] The metal radiation patch 1 and the metal ground layer 3 are respectively attached to the upper and lower surfaces of the dielectric substrate 2. The metal radiation patch 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 radiation patch 1 and the material parameters of the dielectric substrate 2.

[0048] The metal radiation patch 1 is used to radiate electromagnetic wave energy, and the metal ground layer 3 is used to provide a ground signal. The square metal ring 5 is located on the outermost layer; the polygonal metal sheet 7 is located on the innermost layer; the four metal sheet 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 sheet 7. The inner conductor of the feeding interface 4 passes through the dielectric substrate 2 and is connected to the metal radiation patch 1 for inputting radio frequency signals.

[0049] The center position of the feeding interface 4 is 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 sheet 7 is composed of four rectangular metal sheets and one square metal sheet. The four centrally symmetrically arranged rectangular metal sheets are connected to the center positions on the four sides of the square metal sheet. The size of the rectangular metal sheet is 4 mm × 8 mm, and the size of the square metal sheet is 26.22 mm × 26.22 mm. The defect area formed by the square metal ring 5 and the polygonal metal sheet 7 makes the current distribution on the antenna metal ground layer symmetric, reducing the antenna cross polarization.

[0050] The four circular metal sheets 8 are the initial positions of the arrangement of the metal sheet units 6. The centers of the metal sheets at the initial positions are 5.4 mm away from the outer side of the square metal ring 5 both horizontally and vertically. A plurality of periodically arranged circular metal sheets are arranged at equal intervals along the inner edge of the square metal ring 5 and the outer edge of the polygonal metal sheet 7. The distance between adjacent circular metal sheets is 4 mm, and the diameter of the circular metal sheet is 3.6 mm. The plurality of periodically arranged circular metal sheets optimize the field distribution in the defect area formed by the square metal ring 5 and the polygonal metal sheet 7. The photonic crystal structure presented by the plurality of periodically arranged circular metal sheets can prevent some electromagnetic waves from propagating in the defect area, thereby reducing the antenna edge electric field distribution and achieving the purpose of reducing the antenna cross polarization. Adjusting the spacing, size and initial position of the metal sheets can change the surface current distribution of the ground layer and effectively adjust the cross polarization level of the antenna.

[0051] Embodiment 3:

[0052] This embodiment introduces an embodiment of a low cross-polarization microstrip patch antenna with a defected ground structure, as Figure 4 shown. The dielectric substrate 2 is a square substrate made of RT5870 material (dielectric constant is 2.33, loss tangent is 0.001), the size of the dielectric substrate is 50 mm × 50 mm × 1.575 mm, and the size of the metal radiation patch 1 is 14.22 mm × 14.22 mm. The sizes of the dielectric substrate and the metal radiation patch 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 are all changed compared with those in Embodiment 2, so that the number of periods of the metal sheet unit increases, and the number of periods is increased from 2 rows to 3 rows. The rest of the structure is the same as that in Embodiment 2. The increase in the number of periods of the circular metal sheets can further reduce the cross polarization in the H-plane of the antenna and increase the flexibility of the antenna design.

[0054] Embodiment 4:

[0055] This embodiment introduces the comparative experiment between the comparative example and Embodiment 2, specifically including: As Figure 5 shown, the microstrip patch antenna of the comparative example includes a metal radiation patch 1', a dielectric substrate 2', a metal ground plane 3' and a feed interface 4'. The metal radiation patch 1' and the metal ground plane 3' are respectively attached to the upper and lower surfaces of the dielectric substrate 2'. The metal radiation patch 1' is placed at the center of the dielectric substrate 2'. The inner conductor of the feed interface 4' passes through the dielectric substrate 2' and is connected to the metal radiation patch 1' to input a radio frequency signal. Among them, the metal ground plane 3' of the comparative example adopts a metal sheet structure, and the antenna of the comparative example has the same physical size as that of Embodiment 1.

[0056] As Figure 6 shown, the reflection coefficient S11 of the low cross-polarization microstrip patch antenna of Embodiment 2 and the microstrip patch antenna of the comparative example is less than -10 dB in the range of 6.2 GHz - 6.3 GHz. The introduction of the defected ground structure does not affect the operating frequency of the antenna at 6.25 GHz.

[0057] As Figure 7 shown, on the premise of not affecting the main polarization pattern, the cross-polarization levels in the E-plane and H-plane of the low cross-polarization microstrip patch antenna of Embodiment 2 have been greatly improved. In the E-plane, the isolation between the main polarization and cross-polarization of the antenna in Embodiment 2 can be maintained at more than 30 dB; in the H-plane, compared with the microstrip patch antenna of the comparative example, the peak isolation between the main polarization and cross-polarization of the antenna in Case 1 is increased by about 15 dB. The total gain of the antenna in Embodiment 2 is 7 dBi, and the total gain of the microstrip patch antenna of the comparative example is 7.5 dBi. The defected ground structure of the present invention does not have a great impact on the total gain of the antenna, while greatly reducing the cross-polarization of the antenna.

[0058] As Figure 8 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 patch on the ground plane. When the diameter of the circular metal patch is 3.2 mm, 3.4 mm and 3.6 mm, for every 0.2 mm increase in the diameter of the circular metal patch, the peak isolation between the main polarization and cross-polarization of the antenna in Case 1 is increased by about 5 dB. Preferably, the larger the diameter of the circular metal patch on the ground plane, the lower the cross-polarization of the antenna and 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 patch on the ground plane, increasing the flexibility of the design.

[0059] As Figure 9 shown, the metal ground plane of the low cross-polarization microstrip patch antenna of the present invention effectively improves the current distribution of the metal ground plane of the microstrip patch antenna of the comparative example, making the antenna field distribution have strong symmetry and realizing the improvement of the cross-polarization level in the H-plane.

[0060] Compared with the microstrip patch antenna designs of the embodiments and the prior art, the present invention improves the metal ground structure, which satisfies symmetry in both the vertical and horizontal directions and has the same structure, enabling the antenna structure to simultaneously satisfy symmetry and continuity in both the E-plane and H-plane, and greatly suppressing the cross polarization on the H-plane of the antenna, being applicable to dual-polarized wireless communication system applications. Additionally, the circular metal sheets of the photonic crystal structure in the metal ground layer can more flexibly adjust the radiation characteristics of the antenna. Due to more electric fields being concentrated in the defect center region of the photonic crystal structure in the microstrip patch antenna of the present invention, the edge field strength is reduced, and the entire electric field distribution exhibits stronger symmetry. Therefore, the cross polarization level on the H-plane is increased by more than 10 dB.

[0061] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A low cross - polarization microstrip patch antenna with a defected ground structure, characterized in that: It includes a metal ground layer, and the metal ground layer includes: a square metal ring, a plurality of metal sheet units, and a polygonal metal sheet; a polygonal metal sheet is arranged inside the square metal ring, and a plurality of metal sheet units are arranged between the square metal ring and the polygonal metal sheet, and the metal sheet units are composed of metal sheets arranged in a photonic crystal structure.

2. A low cross-polarization microstrip patch antenna with a defective ground structure according to claim 1, characterized in that: It further includes: the metal radiation sheet, the dielectric substrate, and the feeding interface; the metal radiation sheet is attached to the upper surface of the dielectric substrate for radiating electromagnetic wave energy; the metal ground layer is attached to the lower surface of the dielectric substrate; the outer conductor of the feeding interface is connected to the metal ground layer, and the inner conductor of the feeding interface penetrates through the metal ground layer and the dielectric substrate and is connected to the metal radiation sheet for inputting radio frequency signals.

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

4. A low cross-polarization microstrip patch antenna with a defective ground structure according to claim 1, characterized in that: The polygonal metal sheet includes: a square metal sheet, and four rectangular metal sheets are connected to the square metal sheet, and the four rectangular metal sheets are symmetrically arranged around the center of the square metal sheet.

5. A low cross-polarization microstrip patch antenna with a defective ground structure according to claim 1, characterized in that: The square metal ring and the polygonal metal sheet are not connected, the plurality of metal sheet units are not connected, and metal sheet units are arranged in the defect area between the inner side of the square metal ring and the outer side of the polygonal metal sheet.

6. The low cross-polarization 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 arranged at equal intervals in the defect area, and the initial positions are set at the four diagonal areas of the inner edge of the square metal ring.

7. A low cross-polarization microstrip patch antenna with a defective ground structure according to claim 2, characterized in that: The feeding interface adopts a coaxial feeding interface, and the inner conductor of the coaxial feeding interface passes above the center of the metal ground layer.

8. A low cross-polarization 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.

9. A low cross-polarization microstrip patch antenna with a defective ground structure according to claim 8, characterized in that: The metal sheets are set as circular.

10. A low cross-polarization microstrip patch antenna with a defective ground structure according to claim 8, characterized in that: The metal sheets are set as square.

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