A broadband circularly polarized metasurface antenna

Abstract

This invention provides a broadband circularly polarized metasurface antenna, comprising a first dielectric substrate and a second dielectric substrate, a metasurface radiator, a sequential feed network, a metal reflector, a coaxial cable, a feed probe, and a metal short-circuit pin. The first dielectric substrate is disposed parallel to and above the second dielectric substrate. The metal reflector is printed on the lower surface of the second dielectric substrate. The metasurface radiator includes a square patch printed on the center of the lower surface of the first dielectric substrate, and an inner-ring metasurface array, an outer-ring metasurface array, and a quarter-wavelength branch printed on the upper surface of the first dielectric substrate. This broadband circularly polarized metasurface antenna provides a 37.74% operating bandwidth, a gain of 6.36–9.28 dBi, and good directional radiation performance, while also possessing the advantages of wide bandwidth, high gain, and small size.

Description

Technical Field

[0001] This invention relates to the field of communication antennas, and more specifically to a broadband circularly polarized metasurface antenna. Background Technology

[0002] With the development of wireless communication technology, circularly polarized antennas have been widely used in communication systems due to their advantages such as their operating direction being independent of the transmission and reception directions, resistance to multipath interference, and polarization mismatch loss. These include global satellite navigation systems, radio frequency identification systems, and indoor wireless local area network systems.

[0003] However, traditional circularly polarized antennas suffer from several significant drawbacks: narrow bandwidth, high orientation, and low gain. This limits their practical application in modern communication systems. Although many existing broadband circularly polarized antennas have been improved to achieve good operating bandwidth, most of them increase antenna size or reduce antenna gain while increasing bandwidth. Therefore, designing a circularly polarized antenna that can balance broadband, high gain, and small size has become an important research topic.

[0004] Metasurfaces, as two-dimensional materials with unique electromagnetic properties, are widely used for antenna performance optimization. By incorporating metasurfaces, antennas can achieve functions such as broadband optimization, polarization conversion, frequency reconfiguration, miniaturization, and reduced RCS. Currently, various circularly polarized antennas based on metasurfaces have been proposed, especially since using metasurfaces as radiators can achieve advantages such as broadband performance, small size, and high gain.

[0005] For example, Chinese invention patent CN119275589A discloses a metasurface circularly polarized antenna based on characteristic mode theory. This antenna achieves a low profile through the metasurface, but its operating bandwidth is relatively narrow. Chinese invention patent CN112038761A proposes a high-gain circularly polarized antenna. This antenna places a patch antenna directly above the radiating antenna, which improves the operating bandwidth and increases the antenna's radiation gain, but its operating bandwidth is still relatively narrow. Chinese invention patent CN114614265A proposes a broadband circularly polarized metasurface antenna. This antenna achieves broadband and high gain through a metasurface and array approach, but its size is relatively large.

[0006] It is evident that while existing circularly polarized antennas have appropriately improved the shortcomings of narrow bandwidth, high orientation, and low gain by introducing metasurface structures, they still cannot simultaneously achieve the characteristics of wide bandwidth, high gain, and small size, and there is still considerable room for improvement. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a broadband circularly polarized metasurface antenna that simultaneously possesses the characteristics of wide bandwidth, high gain, and small size.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A broadband circularly polarized metasurface antenna includes a first dielectric substrate and a second dielectric substrate, a metasurface radiator, a sequential feed network, a metal reflector, a coaxial cable, a feed probe, and a metal short-circuit pin.

[0010] The first dielectric plate is disposed parallel to and above the second dielectric plate; the metal reflector is printed on the lower surface of the second dielectric plate;

[0011] The metasurface radiator includes a square patch printed on the lower surface of a first dielectric substrate, and an inner metasurface array, an outer metasurface array, and a quarter-wavelength branch printed on the upper surface of the first dielectric substrate. The inner metasurface array surrounds the outer perimeter of the square patch, the outer metasurface array surrounds the outer perimeter of the inner metasurface array, and the quarter-wavelength branch surrounds the outer perimeter of the outer metasurface array and is connected to it. The overall shape of the square patch, the inner metasurface array, the outer metasurface array, and the quarter-wavelength branch is a rotationally symmetric figure with a rotational period of 90° centered on the center of the first dielectric substrate, making the overall shape of the metasurface radiator rotationally symmetric.

[0012] Several metal short-circuit pins penetrate the first dielectric plate and the second dielectric plate in a vertical direction. The upper end of the metal short-circuit pin is located in the gap between the outer metasurface array and the quarter-wavelength branch, and the lower end of the metal short-circuit pin is connected to the metal reflector.

[0013] The sequential feed network is printed in the middle of the upper surface of the first dielectric plate and is positioned directly above the square patch; the coaxial cable passes through the metal reflector and the second dielectric plate from bottom to top, the outer conductor of the coaxial cable is connected to the square patch, and the inner conductor of the coaxial cable passes through the first dielectric plate and is connected to the input end of the sequential feed network.

[0014] The power supply probe penetrates the first dielectric substrate and the second dielectric substrate vertically. The upper end of the power supply probe is connected to the output end of the sequential power supply network, and the lower end of the power supply probe is connected to the metal reflector. The square patch has a circular groove, and the power supply probe passes through the circular groove to couple and excite the power supply signal output by the sequential power supply network to the square patch.

[0015] Furthermore, the dimensions of the broadband circularly polarized metasurface antenna are 0.848λ0×0.848λ0×0.088λ0, where λ0 is the wavelength corresponding to the center frequency of the antenna.

[0016] Furthermore, the inner ring metasurface array includes a plurality of first inner ring metasurface units and four second inner ring metasurface units, which form a square ring around the outside of the square patch;

[0017] The plurality of first inner ring metasurface units are divided into four groups, and the four groups of first inner ring metasurface units are linearly arranged on the outside of the four sides of the square patch. The shape of the first inner ring metasurface unit is rectangular. The four second inner ring metasurface units are respectively disposed on the outside of the four corners of the square patch. The shape of the second inner ring metasurface unit is a square with a square notch, and its square notch matches the corner of the square patch.

[0018] Furthermore, the outer ring metasurface array includes a plurality of first outer ring metasurface units and four second outer ring metasurface units, which form a square ring outside the inner ring metasurface array;

[0019] The plurality of first outer ring metasurface units are divided into four groups, and the four groups of first outer ring metasurface units are linearly arranged on the outside of the four sides of the inner ring metasurface array. The shape of the first outer ring metasurface unit is a square with four square notches. The four second outer ring metasurface units are respectively disposed on the outside of the four corners of the inner ring metasurface array. The shape of the second outer ring metasurface unit is a square.

[0020] Each first outer ring metasurface unit and each second outer ring metasurface unit has a partition slot in the middle, so that each first outer ring metasurface unit and each second outer ring metasurface unit are divided into two metal patches that are symmetrical to each other and do not contact each other; wherein, the extension direction of the partition slot on the first outer ring metasurface unit is perpendicular to the side where the first outer ring metasurface unit is located, and the partition slots on the four second outer ring metasurface units are all arranged along the diagonal of the outer ring metasurface array.

[0021] Furthermore, the quarter-wavelength branch includes eight strip metal lines, the length of which is one-quarter of the wavelength of the antenna center frequency; each of the second outer ring metasurface unit in the outer ring metasurface array is connected to two strip metal lines, wherein each of the two metal patches constituting the second outer ring metasurface unit is connected to one strip metal line; one end of the strip metal line is connected to the outer end of the metal patch of the second outer ring metasurface unit, and the other end of the strip metal line extends towards the middle of the side of the outer ring metasurface array in a direction parallel to the side of the outer ring metasurface array.

[0022] Furthermore, the plurality of metal short-circuit pins are divided into four groups, and the four groups of metal short-circuit pins are respectively disposed on the outer side of the four sides of the outer ring metasurface array; the four groups of metal short-circuit pins are distributed in a rotationally symmetrical manner.

[0023] Furthermore, the square patch is provided with four circular grooves, which are respectively located inside the midpoints of the four sides of the square patch;

[0024] The sequential power supply network has one input terminal and four output terminals. The input terminal of the sequential power supply network is located above the center of the square patch, and the four output terminals are respectively located above the four circular slots of the square patch. The sequential power supply network includes several metal transmission lines of different widths connected in series. The several metal transmission lines start from the input terminal of the sequential power supply network and connect to the four output terminals of the sequential power supply network in a clockwise or counterclockwise direction. There are four power supply probes, each corresponding to one output terminal of the sequential power supply network and one circular slot on the square patch.

[0025] The inner conductor of the coaxial cable excites the sequential feed network through the input end of the sequential feed network to generate a 90° phase difference at the four output ends of the sequential feed network in sequence; the four output ends of the sequential feed network pass through four circular slots on the square patch through four feed probes to couple and excite the feed signal with phase difference to the square patch.

[0026] Furthermore, the metal reflector is provided with four annular grooves, which are respectively arranged around the connection points of the four feed probes and the metal reflector.

[0027] Furthermore, the coaxial cable is a 50Ω coaxial cable.

[0028] This invention provides a broadband circularly polarized metasurface antenna that inverts the traditional circularly polarized patch antenna model to interchange the roles and dimensions of the metal reflector and radiating patch. Impedance matching is improved by etching four annular slots in the metal reflector and designing the patch radiator as a rotationally symmetric metasurface array structure. The axial ratio is effectively improved by introducing a quarter-wavelength branch and a metal short-circuit pin. High-frequency gain is effectively improved by splitting the first and second outer ring metasurface elements through a slotted partition. This invention uses a coaxial cable and a series sequential feed network for feeding, resulting in a simple and compact feeding structure that achieves excellent circularly polarized directional radiation performance.

[0029] In summary, this invention achieves excellent circularly polarized directional radiation performance, reducing return loss to below -10dB in the 1.59-2.65GHz band and achieving an axial ratio of less than 3dB in the 1.72-2.52GHz range. Test results show that the broadband circularly polarized metasurface antenna provided by this invention has a 37.74% operating bandwidth, a gain of 6.36-9.28dBi, and excellent directional radiation performance, while also possessing the advantages of wide bandwidth, high gain, and small size. Attached Figure Description

[0030] Figure 1 This is an exploded view of a broadband circularly polarized metasurface antenna provided in an embodiment of the present invention.

[0031] Figure 2 This is a top view of a broadband circularly polarized metasurface antenna provided in an embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of the structure of the metal short-circuit pin in an embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram of the sequential power supply network and power supply probe in an embodiment of the present invention.

[0034] Figure 5 This is a schematic diagram of the structure of the metal floor in an embodiment of the present invention.

[0035] Figure 6 This is the S-parameter diagram obtained from simulation in an embodiment of the present invention.

[0036] Figure 7 This is the radiation pattern obtained when the device is fed at the center frequency according to an embodiment of the present invention.

[0037] Figure 8 This is a gain curve obtained from simulation of an embodiment of the present invention.

[0038] Figure 9 This is a axial ratio curve obtained from simulation in an embodiment of the present invention.

[0039] Figure 10 This is a comparison diagram of the S-parameters of an embodiment of the present invention and a traditional circularly polarized patch antenna.

[0040] Figure 11 This is a comparison diagram of the axial ratio of the embodiment of the present invention and a traditional circularly polarized patch antenna.

[0041] Figure 12 This is a comparison chart of gain curves before and after adding the partition gap groove in an embodiment of the present invention. Detailed Implementation

[0042] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0043] like Figure 1 As shown in the figure, an embodiment of the present invention provides a broadband circularly polarized metasurface antenna, including a first dielectric substrate 11 and a second dielectric substrate 12, a metasurface radiator, a sequential feed network 3, a metal reflector 4, a coaxial cable 5, a feed probe 6, and a metal shorting pin 7. The dimensions of the broadband circularly polarized metasurface antenna are 0.848λ0 × 0.848λ0 × 0.088λ0, where λ0 is the wavelength corresponding to the antenna's center frequency.

[0044] The first dielectric plate 11 is disposed parallel to the upper part of the second dielectric plate 12; the metal reflector 4 is printed on the lower surface of the second dielectric plate 12.

[0045] The metasurface radiator includes a square patch 21 printed on the middle of the lower surface of the first dielectric substrate 11, and an inner metasurface array 22, an outer metasurface array 23, and a quarter-wavelength branch 24 printed on the upper surface of the first dielectric substrate 11. The inner metasurface array 22 surrounds the outer periphery of the square patch 21, the outer metasurface array 23 surrounds the outer periphery of the inner metasurface array 22, and the quarter-wavelength branch 24 surrounds the outer periphery of the outer metasurface array 23 and is connected to the outer metasurface array 23. The overall shape of the square patch 21, the inner metasurface array 22, the outer metasurface array 23, and the quarter-wavelength branch 24 is a rotationally symmetric figure with the center of the first dielectric substrate 11 as the center and a rotation period of 90°, so that the overall shape of the metasurface radiator is rotationally symmetric.

[0046] Specifically, in combination Figure 2 As shown, the inner ring metasurface array 22 includes a plurality of first inner ring metasurface units 221 and four second inner ring metasurface units 222. The plurality of first inner ring metasurface units 221 and the four second inner ring metasurface units 222 form a square ring outside the square patch 21. The plurality of first inner ring metasurface units 221 are divided into four groups, and the four groups of first inner ring metasurface units 221 are linearly arranged on the outside of the four sides of the square patch 21. The shape of the first inner ring metasurface units 221 is rectangular. The four second inner ring metasurface units 222 are respectively disposed on the outside of the four corners of the square patch 21. The shape of the second inner ring metasurface units 222 is a square with a square notch, and the square notch matches the corner of the square patch 21.

[0047] The outer metasurface array 23 includes a plurality of first outer metasurface units 231 and four second outer metasurface units 232, which form a square ring outside the inner metasurface array 22. The plurality of first outer metasurface units 231 are divided into four groups, which are linearly arranged on the outer sides of the four sides of the inner metasurface array 22. The shape of each first outer metasurface unit 231 is a square with four square notches. The four second outer metasurface units 232 are respectively disposed on the outer sides of the four corners of the inner metasurface array 22, and the shape of each second outer metasurface unit 232 is a square.

[0048] Furthermore, each of the first outer ring metasurface unit 231 and each of the second outer ring metasurface unit 232 has a partition slot in its middle, such that each of the first outer ring metasurface unit 231 and each of the second outer ring metasurface unit 232 is divided into two symmetrical and non-contacting metal patches. The partition slot on the first outer ring metasurface unit 231 extends perpendicularly to the side where the first outer ring metasurface unit 231 is located, and the partition slots on the four second outer ring metasurface units 232 are all arranged along the diagonal of the outer ring metasurface array 23.

[0049] The quarter-wavelength branch 24 includes eight strip metal lines 240, the length of which is one-quarter of the wavelength of the antenna center frequency. Each second outer ring metasurface unit 232 in the outer ring metasurface array 23 is connected to two strip metal lines 240, wherein each of the two metal patches constituting the second outer ring metasurface unit 232 is connected to one strip metal line 240. One end of the strip metal line 240 is connected to the outer end of the metal patch of the second outer ring metasurface unit 232, and the other end of the strip metal line 240 extends towards the middle of the side of the outer ring metasurface array 23 in a direction parallel to the side of the outer ring metasurface array 23.

[0050] Combination Figure 1 and Figure 3 As shown, a plurality of metal short-circuit pins 7 penetrate vertically through the first dielectric substrate 11 and the second dielectric substrate 12. The upper ends of the metal short-circuit pins 7 are disposed in the gap between the outer metasurface array 23 and the quarter-wavelength branch 24, and the lower ends of the metal short-circuit pins 7 are connected to the metal reflector 4. In this embodiment, the plurality of metal short-circuit pins 7 are divided into four groups, each group containing four metal short-circuit pins 7. The four groups of metal short-circuit pins 7 are respectively disposed on the outer sides of the four sides of the outer metasurface array 23; the four groups of metal short-circuit pins 7 are distributed in a rotationally symmetrical manner.

[0051] The sequential power supply network 3 is printed in the middle of the upper surface of the first dielectric substrate 11 and is positioned directly above the square patch 21. The coaxial cable 5 is a 50Ω coaxial cable, which passes through the metal reflector 4 and the second dielectric substrate 12 from bottom to top. The outer conductor of the coaxial cable 5 is connected to the square patch 21, and the inner conductor of the coaxial cable 5 passes through the first dielectric substrate 11 and is connected to the input terminal of the sequential power supply network 3.

[0052] The power supply probe 6 penetrates the first dielectric substrate 11 and the second dielectric substrate 12 in a vertical direction. The upper end of the power supply probe 6 is connected to the output end of the sequential power supply network 3, and the lower end of the power supply probe 6 is connected to the metal reflector 4. The square patch 21 is provided with a circular groove, and the power supply probe 6 passes through the circular groove to couple and excite the power supply signal output by the sequential power supply network 3 to the square patch 21.

[0053] Specifically, in combination Figure 4 As shown. In this embodiment, the square patch 21 is provided with four circular grooves, namely the first circular groove 211, the second circular groove 212, the third circular groove 213 and the fourth circular groove 214, which are respectively located inside the midpoint of the four sides of the square patch 21.

[0054] The sequential power supply network 3 has one input terminal 30 and four output terminals; the four output terminals are respectively the first output terminal 31, the second output terminal 32, the third output terminal 33, and the fourth output terminal 34. The input terminal 30 of the sequential power supply network 3 is located above the center of the square patch 21, and the four output terminals of the sequential power supply network 3 are respectively located above the four circular slots of the square patch 21. Specifically, the first output terminal 31 is located above the first circular slot 211, the second output terminal 32 is located above the second circular slot 212, the third output terminal 33 is located above the third circular slot 213, and the fourth output terminal 34 is located above the fourth circular slot 214. The sequential power supply network 3 includes several metal transmission lines of different widths connected in series. The several metal transmission lines start from the input terminal 30 of the sequential power supply network 3 and are connected to the first output terminal 31, the second output terminal 32, the third output terminal 33, and the fourth output terminal 34 in a clockwise direction. There are four power supply probes 6: a first power supply probe 61, a second power supply probe 62, a third power supply probe 63, and a fourth power supply probe 64. Each power supply probe 6 corresponds to an output terminal of the sequential power supply network 3 and a circular slot on the square patch 21. Specifically, the first power supply probe 61 passes through the first circular slot 211, and its upper end is connected to the first output terminal 31; the second power supply probe 62 passes through the second circular slot 212, and its upper end is connected to the second output terminal 32; the third power supply probe 63 passes through the third circular slot 213, and its upper end is connected to the third output terminal 33; the fourth power supply probe 64 passes through the fourth circular slot 214, and its upper end is connected to the fourth output terminal 34.

[0055] The inner conductor of the coaxial cable 5 excites the sequential feed network 3 through the input terminal 30 of the sequential feed network 3, so as to generate a 90° phase difference at the four output terminals of the sequential feed network 3 in sequence; the four output terminals of the sequential feed network 3 pass through the four circular slots on the square patch 21 through the four feed probes 6 respectively, so as to couple and excite the feed signal with phase difference to the square patch 21.

[0056] Furthermore, such as Figure 5 As shown, the metal reflector 4 is provided with four annular grooves 60, namely a first annular groove 601, a second annular groove 602, a third annular groove 603, and a fourth annular groove 604. The first annular groove 601 is arranged around the connection between the first feed probe 61 and the metal reflector 4; the second annular groove 602 is arranged around the connection between the second feed probe 62 and the metal reflector 4; the third annular groove 603 is arranged around the connection between the third feed probe 63 and the metal reflector 4; and the fourth annular groove 604 is arranged around the connection between the fourth feed probe 64 and the metal reflector 4.

[0057] Figure 6 This is a simulation diagram of the S-parameters obtained from an embodiment of the present invention. As can be seen from the diagram, the frequency band where the antenna reflection coefficient of the embodiment of the present invention is less than -10dB can cover 1.59-2.65GHz.

[0058] Figure 7 This is the radiation pattern obtained when the antenna is fed at the center frequency according to an embodiment of the present invention. The results show that the antenna of the embodiment of the present invention has good directional characteristics.

[0059] Figure 8 This is a gain curve obtained from simulation of an embodiment of the present invention. As can be seen from the figure, the embodiment of the present invention has a gain of 6.36-9.28 dBi across almost the entire operating frequency band.

[0060] Figure 9 This is a simulation curve of the axial ratio obtained from an embodiment of the present invention. As can be seen from the figure, the axial ratio of the embodiment of the present invention is less than 3dB in the range of 1.72-2.52GHz, achieving a wide axial ratio bandwidth.

[0061] Figure 10 This is a comparison diagram of the S-parameters of an embodiment of the present invention and a traditional circularly polarized patch antenna. Figure 11 This is a comparison diagram of the axial ratio of the embodiment of the present invention and a traditional circularly polarized patch antenna. The comparison shows that the operating bandwidth of the embodiment of the present invention is significantly widened.

[0062] Figure 12 This is a comparison of gain curves before and after adding the partition slot in this embodiment of the invention. The dashed line represents the antenna gain curve without the partition slot, under the same structure; the solid line represents the antenna gain curve after adding the partition slot, thus splitting each first outer ring metasurface element 231 and each second outer ring metasurface element 232 into two symmetrical and non-contact metal patches. The comparison shows that this embodiment of the invention improves the antenna gain at high frequencies by using the partition slot to split the first outer ring metasurface element 231 and the second outer ring metasurface element 232.

[0063] This invention provides a broadband circularly polarized metasurface antenna that inverts the traditional circularly polarized patch antenna model to interchange the roles and dimensions of the metal reflector and radiating patch. Impedance matching is improved by etching four annular slots in the metal reflector and designing the patch radiator as a rotationally symmetric metasurface array structure. The axial ratio is effectively improved by introducing a quarter-wavelength branch and a metal short-circuit pin. High-frequency gain is effectively improved by splitting the first and second outer ring metasurface elements through a slotted partition. This invention uses a coaxial cable and a series sequential feed network for feeding, resulting in a simple and compact feeding structure that achieves excellent circularly polarized directional radiation performance.

[0064] In summary, this invention achieves excellent circularly polarized directional radiation performance, reducing return loss to below -10dB in the 1.59-2.65GHz band and achieving an axial ratio of less than 3dB in the 1.72-2.52GHz range. Test results show that the broadband circularly polarized metasurface antenna provided by this invention has a 37.74% operating bandwidth, a gain of 6.36-9.28dBi, and excellent directional radiation performance, while also possessing the advantages of wide bandwidth, high gain, and small size.

[0065] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A broadband circularly polarized metasurface antenna, characterized in that, It includes a first dielectric substrate and a second dielectric substrate, a metasurface radiator, a sequential feed network, a metal reflector, a coaxial cable, a feed probe, and a metal short-circuit pin; The first dielectric plate is disposed parallel to and above the second dielectric plate; the metal reflector is printed on the lower surface of the second dielectric plate; The metasurface radiator includes a square patch printed on the lower surface of a first dielectric substrate, and an inner metasurface array, an outer metasurface array, and a quarter-wavelength branch printed on the upper surface of the first dielectric substrate. The inner metasurface array surrounds the outer perimeter of the square patch, the outer metasurface array surrounds the outer perimeter of the inner metasurface array, and the quarter-wavelength branch surrounds the outer perimeter of the outer metasurface array and is connected to it. The overall shape of the square patch, the inner metasurface array, the outer metasurface array, and the quarter-wavelength branch is a rotationally symmetric figure with a rotational period of 90° centered on the center of the first dielectric substrate, making the overall shape of the metasurface radiator rotationally symmetric. Several metal short-circuit pins penetrate the first dielectric plate and the second dielectric plate in a vertical direction. The upper end of the metal short-circuit pin is located in the gap between the outer metasurface array and the quarter-wavelength branch, and the lower end of the metal short-circuit pin is connected to the metal reflector. The sequential feed network is printed in the middle of the upper surface of the first dielectric plate and is positioned directly above the square patch; the coaxial cable passes through the metal reflector and the second dielectric plate from bottom to top, the outer conductor of the coaxial cable is connected to the square patch, and the inner conductor of the coaxial cable passes through the first dielectric plate and is connected to the input end of the sequential feed network. The feed probe penetrates the first and second dielectric substrates vertically. The upper end of the feed probe is connected to the output end of the sequential feed network, and the lower end of the feed probe is connected to the metal reflector. The square patch has a circular groove, and the feed probe passes through the circular groove to couple and excite the feed signal output by the sequential feed network to the square patch. The outer ring metasurface array includes a plurality of first outer ring metasurface units and four second outer ring metasurface units, which form a square ring outside the inner ring metasurface array. The plurality of first outer ring metasurface units are divided into four groups, and the four groups of first outer ring metasurface units are linearly arranged on the outside of the four sides of the inner ring metasurface array. The shape of the first outer ring metasurface unit is a square with four square notches. The four second outer ring metasurface units are respectively disposed on the outside of the four corners of the inner ring metasurface array. The shape of the second outer ring metasurface unit is a square. Each first outer ring metasurface unit and each second outer ring metasurface unit has a partition slot in the middle, so that each first outer ring metasurface unit and each second outer ring metasurface unit are divided into two metal patches that are symmetrical to each other and do not contact each other; wherein, the extension direction of the partition slot on the first outer ring metasurface unit is perpendicular to the side where the first outer ring metasurface unit is located, and the partition slots on the four second outer ring metasurface units are all arranged along the diagonal of the outer ring metasurface array; The metal reflector is provided with four annular grooves, which are respectively arranged around the connection between the four feed probes and the metal reflector.

2. The broadband circularly polarized metasurface antenna according to claim 1, characterized in that, The dimensions of the broadband circularly polarized metasurface antenna are 0.848λ0 × 0.848λ0 × 0.088λ0, where λ0 is the wavelength corresponding to the center frequency of the antenna.

3. The broadband circularly polarized metasurface antenna according to claim 1, characterized in that, The inner ring metasurface array includes several first inner ring metasurface units and four second inner ring metasurface units, which form a square ring around the outside of the square patch. The plurality of first inner ring metasurface units are divided into four groups, and the four groups of first inner ring metasurface units are linearly arranged on the outside of the four sides of the square patch. The shape of the first inner ring metasurface unit is rectangular. The four second inner ring metasurface units are respectively disposed on the outside of the four corners of the square patch. The shape of the second inner ring metasurface unit is a square with a square notch, and its square notch matches the corner of the square patch.

4. The broadband circularly polarized metasurface antenna according to claim 3, characterized in that, The quarter-wavelength branch includes eight strip metal lines, each strip metal line having a length that is one-quarter of the wavelength of the antenna's center frequency. Each second outer ring metasurface unit in the outer ring metasurface array is connected to two strip metal lines, wherein each of the two metal patches constituting the second outer ring metasurface unit is connected to one strip metal line. One end of the strip metal line is connected to the outer end of the metal patch of the second outer ring metasurface unit, and the other end of the strip metal line extends towards the center of the side of the outer ring metasurface array in a direction parallel to the side of the outer ring metasurface array.

5. The broadband circularly polarized metasurface antenna according to claim 4, characterized in that, The plurality of metal short-circuit pins are divided into four groups, and the four groups of metal short-circuit pins are respectively disposed on the outer side of the four sides of the outer ring metasurface array; the four groups of metal short-circuit pins are distributed in a rotationally symmetrical manner.

6. The broadband circularly polarized metasurface antenna according to claim 1, characterized in that, The square patch has four circular grooves, which are respectively located inside the midpoints of the four sides of the square patch. The sequential power supply network has one input terminal and four output terminals. The input terminal of the sequential power supply network is located above the center of the square patch, and the four output terminals are respectively located above the four circular slots of the square patch. The sequential power supply network includes several metal transmission lines of different widths connected in series. The several metal transmission lines start from the input terminal of the sequential power supply network and connect to the four output terminals of the sequential power supply network in a clockwise or counterclockwise direction. There are four power supply probes, each corresponding to one output terminal of the sequential power supply network and one circular slot on the square patch. The inner conductor of the coaxial cable excites the sequential feed network through the input end of the sequential feed network to generate a 90° phase difference at the four output ends of the sequential feed network in sequence; the four output ends of the sequential feed network pass through four circular slots on the square patch through four feed probes to couple and excite the feed signal with phase difference to the square patch.

7. The broadband circularly polarized metasurface antenna according to claim 1, characterized in that, The coaxial cable is a 50Ω coaxial cable.

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