High gain circularly polarized microstrip antenna based on cross-slot aperture coupling

Abstract

The application discloses a high-gain circularly polarized microstrip antenna based on a cross-shaped slot aperture coupling, and mainly solves the problems that the wide impedance bandwidth and simple structure of an existing Ku-band circularly polarized antenna are difficult to be considered and the gain is low. The antenna adopts a double-layer dielectric substrate structure, and is sequentially provided with a radiation patch (3), an upper dielectric substrate (1), a slot (6), a lower dielectric substrate (2) and a microstrip feed line (7) from top to bottom. The four edges of the radiation patch are provided with semicircular slots, and a corner is provided on one diagonal line of the radiation patch, so as to prolong the current path and change the geometric symmetry of the rectangular patch. The slot adopts a cross-shaped structure with a semicircular extension ring at the top end, so as to effectively expand the impedance bandwidth of the antenna. The microstrip feed line adopts an integrated structure with a symmetric U-shaped bend added at the end of the rectangular strip, and is located below the lower dielectric substrate and can move along the horizontal direction, so as to improve the impedance value of the matching and feed-in point. The application has the advantages of simple structure, high gain and effective expansion of the working bandwidth, and can be used for Ku-band satellite communication and phased array radar.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, and specifically relates to a high-gain circularly polarized microstrip antenna that can be used in Ku-band satellite communication and phased array radar. Background Technology

[0002] In recent years, as space and satellite communication technologies have continued to develop towards higher speeds, miniaturization, and lower profiles, microstrip antennas, with their advantages of light weight, low profile, small size, ease of fabrication, and easy integration with circuits and active devices, have found wide applications in satellite navigation, mobile communication, unmanned aerial vehicle (UAV) technology, phased array radar, and radio astronomy. Microstrip antennas, with their miniaturization and other characteristics, enable lightweight, efficient radiation, and integration within limited installation space, providing technical support for the next generation of aerospace information transmission systems.

[0003] Narrow bandwidth is an inherent limitation of microstrip antennas. Antenna designers have adopted various methods over the years to broaden their bandwidth.

[0004] Patent document CN202211461104.3 discloses a Ku-band single-feed circularly polarized phased array microstrip patch antenna element, which employs a radiating patch with rectangular openings on both sides. A feed probe penetrates from the bottom of a dielectric substrate to the top of the radiating patch, and diamond-shaped slots are formed inside the radiating patch, the dielectric substrate, and the conductive ground plane. However, the rectangular openings on the radiating patch occupy the area of ​​the top metal layer, limiting the layout space of components such as feed lines, matching networks, or decoupling structures in the array, thus limiting the antenna's impedance bandwidth.

[0005] Patent document CN202310688326.7 discloses a wideband beam-polarized microstrip antenna for the Ku-band. It employs a stacked structure, consisting of, from top to bottom, a rectangular radiating patch with U-shaped slots and stubs, a double-layer dielectric substrate, a rectangular excitation patch also with U-shaped slots, and a bottom metal ground plane. A substrate-integrated waveguide composed of L-shaped patches and metal vias is arranged around the radiating patch, and the excitation patch is fed through blind vias. However, the blind via fabrication of this antenna is complex, and because the U-shaped slots and stubs constitute a frequency-sensitive perturbation structure, when the frequency deviates from the center frequency, the antenna's axial ratio bandwidth and impedance bandwidth will experience a mismatch.

[0006] Patent document CN201710223752.8 discloses a broadband low-profile microstrip antenna based on dumbbell-shaped slot coupling excitation. It employs a four-layer high-frequency dielectric substrate laminated structure. The top layer has a rectangular radiating patch and a surrounding array of metallized vias. The upper surface of the second dielectric substrate is etched with dumbbell-shaped coupling slots and grounded via an inner ground plane. The third layer features an L-shaped stripline feed line, which forms a multi-resonant coupling with the dumbbell-shaped slots and is fed to the bottom microstrip feed line and SMP connector via quasi-coaxial vertical interconnects. However, this multi-resonant coupling network suffers from collective mismatch at high frequencies. Furthermore, the thicker dielectric layer exacerbates losses and excites higher-order modes, potentially leading to ineffective energy radiation. Additionally, the antenna's overall structure is complex, hindering miniaturization and integration, and failing to meet the requirement of a phased array system for a close arrangement with element spacing less than half a wavelength. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and propose a high-gain circularly polarized microstrip antenna based on cross-shaped slot aperture coupling, so as to simplify the antenna structure and realize single-port feeding, expand the impedance and axial ratio bandwidth, improve the directional radiation gain and circular polarization purity performance, and facilitate its integrated commercial application in the fields of satellite communication and phased array radar.

[0008] The technical approach to achieving the objective of this invention is to solve the problems existing in the prior art by improving key structures such as radiating patches, coupling gaps, and microstrip feed lines.

[0009] Based on the above ideas, the technical solution of the present invention is as follows:

[0010] 1. A high-gain circularly polarized microstrip antenna based on cross-shaped slot aperture coupling, comprising: an upper dielectric substrate 1, a lower dielectric substrate 2, a radiating patch 3, a slot 6, and a microstrip feed line 7, characterized in that:

[0011] The radiating patch 3 has semi-circular slots 5 on its four sides to extend the current path and increase the electrical length, thereby reducing the frequency and optimizing the radiation and circular polarization performance.

[0012] The slit 6 adopts a cross-shaped structure with a semi-circular extension ring at the top, which is used to load the equivalent capacitance to the coupling channel, enhance electromagnetic coupling, and effectively expand the antenna impedance bandwidth.

[0013] The microstrip feed line 7 adopts an integrated structure with symmetrical U-shaped bends added to the end of the rectangular strip to extend the current path to improve matching, and the single-port feeding simplifies the overall antenna structure.

[0014] Preferably, the semi-circular slots 5 on the four sides of the radiation patch 3 are symmetrical concave arc-shaped bending structures, with the arc of the central angle corresponding to the straight line at the concave part being 27°~40°, and the overall semi-circular radius being 0.44mm~0.52mm.

[0015] Preferably, the radiating patch 3 is a rectangular patch with a side length of 4.77mm~4.81mm, and a set of isosceles triangles with a waist length of 1.53mm~1.61mm are cut at one of its diagonals to change the geometric symmetry of the rectangular patch and convert linear polarization into circular polarization radiation.

[0016] Preferably, the cross-shaped slit 6 with a semi-circular extension ring at the top has a slit width of 0.23mm to 0.29mm, the four arms of the cross are of equal length, the inner radius of the extended semi-circular ring is 0.93mm to 0.99mm, and the ring width is equal to the slit width.

[0017] Preferably, the rectangular strip has an integral microstrip feed line 7 with a symmetrical U-shaped bend at the end. The main body of the rectangular microstrip feed line has a length of 4.13mm to 4.19mm and a width of 0.36mm to 0.42mm. The height of the U-shaped bend structure is 0.88mm to 0.93mm and the width is 0.81mm to 0.89mm.

[0018] Compared with the prior art, the present invention has the following advantages

[0019] Firstly, by employing a diagonally chamfered rectangular radial patch 3, the geometric symmetry of the rectangular patch is altered, thus enabling the two orthogonal degenerate modes TM to be... 10 With TM 01 It generates a 90° phase difference and maintains similar amplitudes, and can convert linear polarization into circular polarization radiation. At the same time, due to the semi-circular slots 5 on the four sides of the radiating patch, its surface current path can be extended, which is equivalent to increasing the electrical length, thereby reducing the resonant frequency and improving the directional radiation gain and circular polarization purity performance. This rectangular radiating patch with diagonal chamfers and four-sided slots not only overcomes the problems of increased loss due to multi-layer complex structure and thick dielectric layer, excitation of high-order modes and unfavorable miniaturization integration, but also avoids complex multi-layer lamination process while ensuring high performance, which is more conducive to the compact arrangement and integration of phased array systems.

[0020] Secondly, this invention employs a cross-shaped structure slot 6 with a semi-circular extension ring at the top. The semi-circular extension structure loads the additional equivalent capacitance into the coupling channel, which can enhance the electromagnetic coupling between the feed network and the radiating patch, and simultaneously introduce multiple coupling paths to form a multi-mode resonance mechanism. This effectively overcomes the problem of difficulty in matching the axial ratio bandwidth and impedance bandwidth caused by the frequency-sensitive perturbation structure, and significantly expands the impedance bandwidth of the antenna.

[0021] Thirdly, this invention employs an integrated microstrip feed line 7 with a symmetrical U-shaped bend at the end of a rectangular strip. By utilizing the inductive effect generated by the U-shaped bend structure to form a complementary resonance with the slot capacitance, the input impedance of the feed point can be flexibly adjusted without additionally occupying the effective radiation area of ​​the radiating patch, significantly improving the feed matching performance. At the same time, this integrated design not only meets the single-port feed requirements and avoids the encroachment of complex external matching circuits on the antenna array layout space, but also further simplifies the overall antenna structure and improves the convenience of engineering implementation.

[0022] Fourth, this invention employs a design mechanism where the microstrip feed line 7 can be horizontally moved along the patch length. By utilizing the impedance adjustment effect of the feed point position change, the equivalent electrical size can be increased without changing the physical size of the antenna. The increased equivalent electrical size excites multiple resonant modes, effectively expanding the impedance bandwidth to enhance the antenna's operating frequency band adaptability. Simultaneously, this optimization method based on feed line position adjustment does not require additional complex circuitry or significant modifications to the antenna's main architecture, ensuring the simplicity of the single-port feed system while further meeting the miniaturized integration requirements of antennas in practical applications. Attached Figure Description

[0023] Figure 1 This is an exploded view of the high-gain circularly polarized microstrip antenna based on cross-shaped slot aperture coupling of the present invention.

[0024] Figure 2 This is a structural diagram of the radiation patch in this invention;

[0025] Figure 3 A top view of the cross-shaped gap structure on the metal grounding plate;

[0026] Figure 4 This is a graph showing the variation of the antenna's reflection coefficient and gain with the slot size.

[0027] Figure 5 This is a graph showing the variation of the reflection coefficient and axial ratio of the antenna of the present invention with the width of the coupling slot;

[0028] Figure 6 The figure shows the simulation results of the overall performance of the antenna of this invention. Detailed Implementation

[0029] 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0030] Reference Figure 1 This example provides the following three implementation methods:

[0031] Example 1: A high-gain circularly polarized microstrip antenna with high directional gain and excellent circular polarization purity operating in the Ku band, based on cross-shaped slot aperture coupling.

[0032] This example includes an upper dielectric substrate 1, a lower dielectric substrate 2, a radiating patch 3, a slot 6, and a microstrip feed line 7, wherein:

[0033] The upper dielectric substrate 1 is made of Rogers RT / duroid 5880 (tm) with a dielectric constant ε. r = 2.2, its thickness is 1.44mm and its width is 9mm.

[0034] The lower dielectric substrate 2 is made of Rogers RO4003 (tm) with a dielectric constant ε. r = 3.55, its thickness is 0.254mm, and its width is 9mm. Its upper surface is covered with a layer of metal as a metal ground plate, and copper is selected as the material for the metal ground plate.

[0035] The radiation patch 3, such as Figure 2 As shown, it is printed on the upper dielectric substrate 1, and the material is metallic copper. The shape is a rectangle with four sides of length 4.8mm. A set of isosceles triangles with a waist length of 1.55mm are cut at the diagonal. This asymmetric perturbation design breaks the original spatial geometric symmetry of the rectangular patch, thereby exciting two orthogonal and degenerate resonant modes, causing the linear polarization to convert to circular polarization. The rectangular radiating patch 3 has a semi-circular groove 5 at the center of its four sides. It is a symmetrical concave arc bending structure. The arc of the central angle corresponding to the straight line of the concave part is 35°. The overall semi-circular radius is 0.49mm. This causes the high-frequency current on the patch surface to bend and flow around the edge of the groove, thereby extending its surface current path, effectively increasing the electrical length, reducing the resonant frequency, and improving the directional radiation gain and circular polarization purity performance.

[0036] The gap 6, as Figure 3As shown, the slot is etched onto the metal ground plane on the upper surface of the lower dielectric substrate 2. The slot is a cross-shaped structure with a semi-circular extension ring at the top, with a width of 0.25 mm. The four arms of the cross are of equal length, and the inner radius of the extended semi-circular ring is 0.97 mm, with its width equal to the width of the main slot. This semi-circular extension ring introduces an additional equivalent capacitance loading effect into the original linear coupling channel. This not only effectively enhances the near-field electromagnetic coupling efficiency between the bottom-layer feed network and the upper-layer radiating patch, but also introduces multiple differentiated energy transmission paths by changing the boundary conditions at the slot edge. The resulting multi-mode resonance mechanism allows the antenna to achieve the superposition and fusion of multiple near-resonant points without significantly increasing its physical size, thereby expanding the antenna's impedance bandwidth and optimizing its high-frequency matching characteristics.

[0037] The microstrip feed line 7 is located below the lower dielectric substrate 2. It features a symmetrical U-shaped bend at the end of a rectangular strip. The main body of the rectangular microstrip feed line is 4.16 mm long and 0.39 mm wide; the height of the U-shaped bend is 0.9 mm and equal to the width of the feed line. The inductive effect generated by this U-shaped bend structure forms a complementary resonance with the slot capacitance, allowing for flexible adjustment of the input impedance at the feed point without additionally occupying the effective radiating area of ​​the radiating patch, significantly improving feed matching performance. The microstrip feed line 7 is symmetrically offset to the left by 0.01 mm relative to the geometric center of the antenna and can be moved horizontally along the patch length. This change in the feed point position allows for impedance adjustment, increasing the equivalent electrical size without altering the antenna's physical dimensions. This increase in equivalent electrical size stimulates multiple resonant modes, effectively expanding the impedance bandwidth to enhance the antenna's operating frequency band adaptability. Meanwhile, this optimization method based on feeder position adjustment does not require the addition of complex circuits or significant changes to the main antenna architecture, which not only ensures the simplicity of the single-port feed system, but also further meets the miniaturization and integration requirements of antennas in practical applications.

[0038] Example 2: A high-gain circularly polarized microstrip antenna based on cross-shaped slot aperture coupling, achieving impedance bandwidth and axial ratio bandwidth matching, operating in the Ku band with high directional gain and excellent circular polarization purity.

[0039] The overall structure of this example is the same as that of Example 1, with the following changes to the parameters of some key structures:

[0040] The side length of the radiation patch 3 is reduced to 4.78 mm, the side length of a set of diagonally opened isosceles triangles is increased to 1.59 mm, and the dimensional parameters of the semi-circular slots 5 at the center of the four sides remain unchanged.

[0041] The gap 6 has its width adjusted to 0.27 mm, and the inner radius of the extended semi-circular ring is reduced to 0.93 mm.

[0042] The microstrip feed line 7 has its main body length reduced to 4.14 mm, its width reduced to 0.36 mm, and the height of its U-shaped bend structure reduced to 0.89 mm, while the feed line width remains unchanged.

[0043] The materials, dielectric constants, board thicknesses, and side lengths of the upper dielectric substrate 1 and the lower dielectric substrate 2 remain unchanged.

[0044] By coordinating the above parameters, the electromagnetic coupling mechanism inside the antenna can be effectively optimized, thereby achieving precise matching between impedance bandwidth and axial ratio bandwidth. While ensuring the stability of the operating frequency band, the structure can still accurately excite orthogonal degenerate modes with equal amplitude and a 90-degree phase difference, and maintain good port return loss characteristics. Thus, it balances high-purity circular polarization performance and wide impedance bandwidth in the target frequency band, improving the overall electrical performance of the antenna.

[0045] Example 3: A high-gain circularly polarized microstrip antenna based on cross-shaped slot aperture coupling, achieving wide impedance bandwidth, high directional gain and excellent circular polarization purity in the Ku band.

[0046] The overall structure of this example is the same as that of Example 1, with the following changes to the parameters of some key structures:

[0047] The side length of the radiation patch 3 is increased to 4.81 mm, the length of the isosceles triangles formed diagonally is increased to 1.55 mm, the radius of the semi-circular slots 5 at the center of the four sides is increased to 0.52 mm, and the arc of the central angle corresponding to the straight line at the concave part is adjusted to 30°.

[0048] The slit 6 has its width reduced to 0.23 mm, and the inner radius of the extended semi-circular ring has increased to 0.98 mm.

[0049] The microstrip feed line 7 has its main body length increased to 4.17 mm, its width increased to 0.41 mm, the height of its U-shaped bend structure increased to 0.93 mm, its feed line width reduced to 0.38 mm, and its geometric center symmetry axis relative to the antenna adjusted to be offset to the left by 0.03 mm.

[0050] The materials, dielectric constants, board thicknesses, and side lengths of the upper dielectric substrate 1 and the lower dielectric substrate 2 remain unchanged.

[0051] By coordinating the above parameters, the electromagnetic coupling mechanism and resonance characteristics inside the antenna can be effectively controlled. Adjusting the size of the radiating patch and the slot radius introduces an additional capacitive loading effect, reducing the antenna's quality factor. The reduction of the slot width, combined with the increase of the inner radius of the extended semicircular ring, further improves the aperture coupling strength and the impedance transformation characteristics of the feed network. This series of geometric parameter adjustments smooths the impedance matching slope near the resonant frequency. At the same time, this structure can accurately excite orthogonal degenerate modes with equal amplitude and a 90° phase difference. While ensuring excellent port return loss characteristics, it effectively reduces reflection loss and improves radiation efficiency, successfully achieving a stable coexistence of a wide impedance bandwidth and high gain characteristics.

[0052] The effects of this invention can be further illustrated by the following simulation results:

[0053] I. Simulation Conditions

[0054] The simulation software is HFSS 2021 R1;

[0055] Assume the air box at the radiation boundary has a length of 15mm, a width of 15mm, and a height of 15mm;

[0056] The central solution frequency is set to 15 GHz;

[0057] Set the starting azimuth of the radiation boundary to 0°, the ending azimuth to 360°, and the step size to 10°.

[0058] Set the initial pitch angle of the radiation boundary to 0°, the final pitch angle to 180°, and the step size to 10°.

[0059] II. Simulation Content

[0060] Simulation 1: Under the above simulation conditions, a scanning simulation with a parameter range of 30°~40° was performed on the central angle b corresponding to the straight line at the concave part of the four sides of the radiating patch in Embodiment 1 of the present invention. The results are as follows: Figure 4 As shown, where:

[0061] Figure 4 (a) is a curve showing the change of the antenna reflection coefficient with respect to the central angle angle corresponding to the straight line at the concave side.

[0062] Figure 4 (b) is the curve showing the change of antenna gain with the central angle.

[0063] from Figure 4As can be seen, with the increase of the central angle 'b' corresponding to the straight lines at the concave sides, the current path on the patch surface lengthens, and the equivalent electrical length of the antenna increases accordingly. This structural change causes the high-frequency resonant mode of the antenna to shift significantly towards the low-frequency direction. Simultaneously, since the frequency of the low-frequency main resonant mode is primarily determined by the overall physical dimensions of the patch, its resonant position remains essentially stable. From the perspective of electromagnetic radiation mechanism analysis, the high-frequency resonant mode of this antenna essentially originates from the degenerate mode TM. 10 With TM 01 The interaction and coupling between the high and low frequency resonant modes cause the gain curve to evolve synchronously in the high-frequency band, reaching its peak at a central angle b=35° corresponding to the straight line at the concave sides, while the radiation characteristics in the low-frequency band remain stable. This structure achieves independent decoupling control of the high and low frequency resonant modes, enabling flexible adjustment of the high-frequency resonant point position and optimization of the gain peak while maintaining stable low-frequency radiation characteristics, thereby effectively widening the overall impedance bandwidth of the antenna.

[0064] Simulation 2: Under the above simulation conditions, a scanning simulation with a parameter range of 0.20mm~0.30mm was performed on the coupling gap width W of the metal ground plane in Embodiment 1 of the present invention. The results are as follows: Figure 5 As shown, where:

[0065] Figure 5 (a) shows the curve of antenna reflection coefficient as a function of coupling slot width.

[0066] Figure 5 (b) is the curve showing the change of antenna axial ratio with the width of the coupling slot.

[0067] from Figure 5 As can be seen, with the increase of coupling slot width W, the feed coupling strength is enhanced, the low-frequency resonant mode remains basically unchanged, and the high-frequency resonant mode shifts to the low frequency. At the same time, the increase in coupling strength effectively improves the amplitude balance relationship between the two orthogonal modes. When the coupling slot width W = 0.25 mm, the axial ratio of the antenna in the 14.86–15.20 GHz band drops to below 3 dB, effectively improving the amplitude balance of the orthogonal modes and optimizing the axial ratio performance, thereby achieving excellent circular polarization radiation characteristics.

[0068] Simulation 3: Under the above simulation conditions, the antenna performance in Embodiment 1 of the present invention was simulated, and the results are as follows. Figure 6 As shown, where:

[0069] Figure 6 (a) is the antenna reflection coefficient curve.

[0070] Figure 6 (b) shows the antenna gain curve.

[0071] Figure 6(c) is the antenna axial ratio curve.

[0072] from Figure 6 As can be seen, the antenna has a bandwidth of 13.79–19.50 GHz (70.17%) with a reflection coefficient less than 10 dB, a 5 dBi gain bandwidth of 13.36–24.28 GHz (47.33%), a maximum gain of 7.42 dBi at 21.50 GHz, and an axial ratio satisfying a bandwidth of 14.86–15.20 GHz (2.262%) below 3 dB. This indicates that the antenna of the present invention achieves a wide impedance bandwidth of 70.17% and a wide bandwidth of 47.33% with high gain, while maintaining excellent circularly polarized radiation characteristics in a specific high-frequency band.

Claims

1. A high-gain circularly polarized microstrip antenna based on cross-shaped slot aperture coupling, comprising: The upper dielectric substrate (1), the lower dielectric substrate (2), the radiating patch (3), the slot (6), and the microstrip feed line (7) are characterized by: The radiation patch (3) has semi-circular slots (5) on its four sides to extend the current path and increase the electrical length, thereby reducing the frequency and optimizing the radiation and circular polarization performance. The slit (6) adopts a cross-shaped structure with a semi-circular extension ring at the top, which is used to load the equivalent capacitance to the coupling channel, enhance electromagnetic coupling, and effectively expand the antenna impedance bandwidth. The microstrip feed (7) adopts an integrated structure with symmetrical U-shaped bends added to the end of the rectangular strip to extend the current path to improve matching, and the single-port feeding simplifies the overall antenna structure.

2. The antenna according to claim 1, characterized in that, The semi-circular slots (5) on the four sides of the radiation patch (3) are symmetrical concave arc-shaped bending structures. The arc of the central angle corresponding to the straight line at the concave part is 27°~40°, and the overall semi-circular radius is 0.44mm~0.52mm.

3. The antenna according to claim 1, characterized in that, The radiation patch (3) is a rectangular patch with a side length of 4.77mm~4.81mm. A set of isosceles triangles (4) with a waist length of 1.53mm~1.61mm are cut at the diagonal to change the geometric symmetry of the rectangular patch and convert linear polarization into circular polarization radiation.

4. The antenna according to claim 1, characterized in that, The cross-shaped structure gap (6) with a semi-circular extension ring at the top has a gap width of 0.23mm~0.29mm, the four arms of the cross are of equal length, the inner radius of the extended semi-circular ring is 0.93mm~0.99mm, and the ring width is equal to the gap width.

5. The antenna according to claim 1, characterized in that, The rectangular strip has an integral microstrip feed line (7) with a symmetrical U-shaped bend at the end. The main body of the rectangular microstrip feed line has a length of 4.13mm~4.19mm and a width of 0.36mm~0.42mm. The height of the U-shaped bend structure is 0.88mm~0.93mm, which is the same as the width of the feed line.

6. The antenna according to claim 5, characterized in that, The microstrip feed line (7) is located below the lower dielectric substrate (2) and can move horizontally to change the impedance value of the feed point, thereby increasing the equivalent electrical size without changing the physical size, exciting multiple resonant modes, and improving the impedance bandwidth.

7. The antenna according to claim 1, characterized in that, The upper layer dielectric substrate (1) is made of Rogers RT / duroid 5880 (tm) with dielectric constant ε r = 2.2, thickness of 1.41mm~1.47mm, width of 8.5mm~9.3mm.

8. The antenna according to claim 1, characterized in that, The lower layer dielectric substrate (2) is made of Rogers RO4003 (tm) with dielectric constant ε r = 3.55, thickness of 0.249mm~0.260mm, width of 8.5mm~9.3mm; and its upper surface is coated with a layer of metal as a metal ground plate.

9. The antenna according to claim 1, characterized in that: The radial patch (3) with a semi-circular slot (5) and isosceles triangular chamfers (4) at the diagonal is printed on the upper dielectric substrate (1). The cross-shaped slit (6) with a semi-circular extension ring at the top is etched on the metal ground plane on the lower dielectric substrate (2). The rectangular strip has a symmetrical U-shaped integral microstrip feed line (7) added to its end, which is located at the bottom layer, forming a three-layer stacked structure from top to bottom.

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