High-gain low-profile dual circularly polarized antenna based on metasurface

Abstract

The invention, which relates to the technical field of modern communication, discloses a metasurface-based high-gain low-profile dual-circularly polarized antenna comprising a first dielectric plate, a second dielectric plate arranged below the first dielectric plate, and a metasurface structure arranged above the first dielectric plate. Three rows and three columns of periodically arranged metasurface structures are arranged above the first dielectric plate, a multi-level cooperative working mechanism is constructed by combining 45-degree symmetrical composite gaps etched in a layer indirect floor and a microstrip feeder line which is orthogonally arranged on the lower layer, and the metasurface array realizes high-gain radiation by regulating and controlling the phase of electromagnetic waves. The composite slot structure efficiently converts microstrip line energy into an orthogonal degenerate mode through non-contact coupling, circular polarization purity is guaranteed, the axial ratio bandwidth is expanded to 24.2%, an orthogonal microstrip feeder line forms a 90-degree phase difference through accurately controlled size, high isolation and stable standing-wave ratio of double ports are guaranteed, and the antenna has a wide application prospect. And finally, dual-circular-polarization independent radiation is realized in a 5mm low-profile structure.

Description

Technical Field

[0001] This invention relates to the field of modern communication technology, and in particular to a high-gain, low-profile, dual-circularly polarized antenna based on a metasurface. Background Technology

[0002] Circularly polarized antennas have significant application value in satellite communication and radar telemetry and control due to their advantages such as effective resistance to rain and fog interference and multipath fading, the ability to accept linearly polarized waves of arbitrary polarization, and the ability for their transmitted waves to be received by antennas of arbitrary polarization. In recent years, the development of metasurfaces has provided new ideas for the design of high-performance circularly polarized antennas. There are two main methods for applying metasurfaces to the design of circularly polarized antennas: one is to use the metasurface as an auxiliary structure, that is, to place a whole metasurface behind the circularly polarized antenna to achieve the requirements of high gain and wide beam; the other is to use the metasurface as the radiating structure of the antenna to realize a circularly polarized antenna with high gain, low profile, and wide frequency band.

[0003] Traditional microstrip dual-circular polarized antennas are limited by the resonance mechanism, and their impedance bandwidth and axial ratio bandwidth are usually narrow, making it difficult to meet the needs of modern broadband communication systems. Due to surface wave loss and limited electrical size, their gain is generally low. Although the bandwidth can be extended by stacking parasitic patches or using sequential rotation feeding, the methods often come at the cost of increasing the profile height and structural complexity, which severely restricts the application of dual-circular polarized antennas in miniaturized satellite terminals and portable communication devices. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a high-gain, low-profile dual-circular polarized antenna based on metasurfaces. This addresses the limitations of traditional microstrip dual-circular polarized antennas, which are constrained by the resonance mechanism and typically have narrow impedance and axial ratio bandwidths, making it difficult to meet the needs of modern broadband communication systems. Due to surface wave loss and finite electrical dimensions, their gain is generally low. Although the bandwidth can be extended by stacking parasitic patches or using sequential rotation feeding techniques, these methods often come at the cost of increased profile height and structural complexity, severely restricting the application of dual-circular polarized antennas in miniaturized satellite terminals and portable communication devices.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a high-gain, low-profile, dual-circularly polarized antenna based on a metasurface, comprising: A first dielectric substrate, a second dielectric substrate disposed below the first dielectric substrate, and a metasurface structure disposed above the first dielectric substrate.

[0007] As a preferred embodiment of the high-gain, low-profile, dual-circularly polarized antenna based on metasurface as described in this invention, the metasurface structure consists of square metal patches arranged periodically in a three-row, three-column configuration to form a planar array.

[0008] As a preferred embodiment of the high-gain, low-profile dual-circularly polarized antenna based on metasurfaces according to the present invention, the antenna further includes a ground plane disposed between the first dielectric substrate and the second dielectric substrate, wherein a slot structure for coupling power is etched in the central region of the ground plane.

[0009] As a preferred embodiment of the high-gain, low-profile dual-circularly polarized antenna based on metasurface described in this invention, the slot structure consists of an annular slot and two rectangular slots. The two rectangular slots are centrally symmetrical about the center point of the annular slot, and the length direction of each rectangular slot is at a 45-degree angle to the horizontal direction.

[0010] As a preferred embodiment of the high-gain, low-profile dual-circularly polarized antenna based on metasurfaces described in this invention, the annular slot has an inner radius of 8 mm and an outer radius of 9.5 mm, and each rectangular slot has a length of 6.5 mm and a width of 0.5 mm.

[0011] As a preferred embodiment of the high-gain, low-profile dual-circularly polarized antenna based on metasurface described in this invention, the antenna further includes two microstrip feed lines printed on the lower surface of the second dielectric substrate, the two microstrip feed lines being arranged perpendicularly to each other in space.

[0012] As a preferred embodiment of the high-gain, low-profile dual-circularly polarized antenna based on metasurface described in this invention, the microstrip feed line has a length of 57.5 mm and a width of 6 mm.

[0013] As a preferred embodiment of the high-gain, low-profile, dual-circularly polarized antenna based on metasurface as described in this invention, the antenna has an overall shape of a cuboid with a length of 100mm, a width of 100mm, and a height of 5mm. The first dielectric substrate is made of AD35 and has a thickness of 3mm, and the second dielectric substrate is made of FR4 and has a thickness of 2mm.

[0014] As a preferred embodiment of the high-gain, low-profile dual-circularly polarized antenna based on metasurface as described in this invention, wherein: the microstrip feed line cooperates with the slot structure on the ground plane, the microstrip feed line and the slot structure on the ground plane jointly excite the metasurface structure through a phase difference, and the metasurface structure excites and radiates two types of circularly polarized electromagnetic waves.

[0015] As a preferred embodiment of the high-gain, low-profile dual-circular polarization antenna based on metasurface described in this invention, the microstrip feed lines are used to excite right-hand circularly polarized waves and left-hand circularly polarized waves respectively, so as to enable the antenna to have dual-circular polarization radiation function.

[0016] The beneficial effects of this invention are as follows: a three-row, three-column periodic metasurface array is arranged above the first dielectric substrate, a symmetrical composite slot is etched on the ground plane, and an orthogonal microstrip feeder is arranged on the lower layer, forming a multi-level cooperative structure. The metasurface array achieves beam focusing and high-gain radiation through spatial phase modulation. The composite slot is excited by non-contact coupling to generate dual orthogonal degenerate modes, generating circular polarization and widening the axial ratio bandwidth. The orthogonal microstrip feeder generates phase difference through size optimization, ensuring high isolation and good standing wave ratio at both ports. The whole system achieves independent radiation with dual circular polarization in an extremely low profile, solving the problems of low gain, narrow bandwidth, and complex structure of traditional antennas. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A three-dimensional view of a high-gain, low-profile, dual-circularly polarized antenna based on a metasurface. Figure 2 Antenna VSWR diagram; Figure 3 Antenna axial ratio diagram; Figure 4 Antenna gain diagram; Figure 5 This is a two-dimensional radiation pattern of a 2.5GHz antenna.

[0019] In the figure: 101, first dielectric substrate; 102, second dielectric substrate; 103, metasurface structure. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0023] Reference Figure 1 — Figure 5 This embodiment of the invention provides a high-gain, low-profile dual-circularly polarized antenna based on a metasurface, comprising: A first dielectric plate 101, a second dielectric plate 102 disposed below the first dielectric plate 101, and a metasurface structure 103 disposed above the first dielectric plate 101.

[0024] Specifically, the metasurface structure 103 consists of square metal patches arranged periodically in a three-row, three-column pattern to form a planar array.

[0025] Furthermore, the periodic spacing of the square metal patches is configured to be 0.15 to 0.25 times the wavelength corresponding to the center frequency of the operating band. The periodic arrangement enables electromagnetic coupling between the patch units, which not only enhances the metasurface's ability to locally modulate the phase of electromagnetic waves, enabling it to form a stable in-phase radiation field near a specific frequency point, but also effectively expands the impedance matching bandwidth of the antenna and improves the circular polarization axial ratio performance by optimizing the surface wave propagation characteristics.

[0026] It should be noted that this periodic arrangement effectively suppresses the generation of higher-order modes by adjusting the surface wave impedance, thereby improving the antenna's radiation efficiency.

[0027] Specifically, the antenna also includes a ground plane disposed between the first dielectric substrate 101 and the second dielectric substrate 102, and the central region of the ground plane is etched with a slot structure for coupling power supply.

[0028] Furthermore, as a key functional layer of the antenna, the ground plane, with its composite slot structure, simultaneously acts as a coupler and mode converter in the electromagnetic field. Through a non-contact electromagnetic coupling mechanism, it efficiently converts the quasi-transverse electromagnetic waves transmitted by the lower microstrip feed line into the specific field distribution required by the upper metasurface structure 103. This process not only reduces parasitic radiation and impedance mismatch introduced by direct feeding, but also lays the physical foundation for exciting degenerate modes with equal amplitude and orthogonal phase at the two orthogonal ports by precisely controlling the electric field vector direction in the coupling region. This fundamentally ensures the antenna's performance in achieving high-purity circularly polarized radiation.

[0029] It should be noted that this non-contact coupling design achieves efficient energy transfer while reducing the shielding effect of the power supply network on the radiation aperture.

[0030] Specifically, the gap structure consists of an annular gap and two rectangular gaps. The two rectangular gaps are centrally symmetrical about the center point of the annular gap, and the length direction of each rectangular gap is at a 45-degree angle to the horizontal direction.

[0031] Furthermore, the annular gap in the composite gap structure is mainly responsible for controlling the low-frequency resonance characteristics of the coupled energy, while the two rectangular gaps, which are centrally symmetrically distributed at a 45° angle, decompose two electric field components with equal amplitude and orthogonal phase on the ground plane through their specific spatial orientation. This geometry essentially constitutes a natural waveguide mode converter, which can automatically convert linearly polarized waves transmitted through microstrip lines into the two degenerate modes required for circularly polarized waves, thereby providing a circularly polarized excitation source for the upper metasurface without the need for additional phase-shifting circuitry.

[0032] It should be noted that this 45° symmetrical slot configuration naturally satisfies the phase condition for circular polarization excitation in terms of structure, thus avoiding the use of complex external phase networks.

[0033] Specifically, the inner radius of the annular slit is 8mm, the outer radius is 9.5mm, and the length of each rectangular slit is 6.5mm and the width is 0.5mm.

[0034] Furthermore, through the coordinated optimization design of the inner and outer radius dimensions of the annular gap and the length and width dimensions of the rectangular gap, the distribution path and resonance characteristics of the ground plane surface current were precisely controlled. The radial dimensions of the annular slot determine the location of the main resonant frequency and the coupling strength, while the rectangular slot with a specific aspect ratio finely controls the current phase and amplitude distribution in the high-frequency band through its high impedance characteristics. This combination of dimensions enables the composite slot structure to simultaneously excite two degenerate modes with highly balanced amplitudes and strictly orthogonal phases in a wide frequency band of 2.0-2.7 GHz, thus providing key feeding conditions for achieving stable broadband dual-circular polarization radiation.

[0035] It should be noted that these optimized key dimensional parameters were obtained through repeated iterations using full-wave electromagnetic simulation software, ensuring a high degree of consistency between theoretical design and measured performance.

[0036] Specifically, the antenna also includes two microstrip feed lines printed on the lower surface of the second dielectric substrate 102, which are arranged perpendicular to each other in space.

[0037] Furthermore, these two spatially orthogonal microstrip feed lines constitute the antenna's dual-port feed network. Their orthogonal layout enables two spatially perpendicular fundamental mode electric field distributions to be excited at the ground plane gap when the signal is input from the two ports respectively. This geometric orthogonality, combined with a proper feed phase relationship, is the necessary physical condition for generating two circularly polarized waves with opposite directions of rotation. At the same time, the symmetrical structure effectively ensures high isolation and amplitude consistency between the two polarization ports, providing a structural basis for the antenna to achieve good dual circular polarization performance.

[0038] It should be noted that this orthogonal layout not only achieves polarization diversity, but also effectively compensates for the impact of manufacturing tolerances on port balance through structural symmetry.

[0039] Specifically, the microstrip feeder is 57.5 mm long and 6 mm wide.

[0040] Furthermore, the 57.5mm length of the microstrip feed line is designed to be one-quarter of the waveguide wavelength corresponding to the center frequency of the operating band. This specific length makes the end of the feed line present a high impedance state that is close to an open circuit, thus forming the best impedance transformation with the slot coupling point. Meanwhile, the 6mm linewidth is precisely calculated to ensure that the characteristic impedance of the microstrip line is conjugate matched with the system standard impedance. The synergistic design of these two key dimensions not only minimizes port reflection loss, but also provides the necessary electrical length conditions for generating a precise 90-degree phase difference at the two orthogonal ports by controlling the signal propagation phase.

[0041] It should be noted that this precise dimensional design enabled the antenna to achieve a voltage standing wave ratio (VSWR) better than 1.5 in the 2.0-2.7 GHz band.

[0042] Specifically, the antenna has an overall shape of a cuboid with a length of 100mm, a width of 100mm, and a height of 5mm; the first dielectric substrate 101 is made of AD35 and has a thickness of 3mm, and the second dielectric substrate 102 is made of FR4 and has a thickness of 2mm.

[0043] Furthermore, this precisely calculated overall size and material combination constitutes an electrically large resonant cavity structure, in which the low-loss AD35 dielectric substrate serves as a carrier for the metasurface, effectively improving radiation efficiency, while the cost-optimized FR4 dielectric substrate maintains sufficient mechanical strength and forms an appropriate impedance gradient with the upper dielectric substrate through its specific dielectric constant. This hybrid dielectric design reduces the overall manufacturing cost while ensuring antenna radiation performance.

[0044] It should be noted that this compact stacked structure, while ensuring radiation performance, keeps the profile height within 5mm, meeting the miniaturization requirements of modern communication systems.

[0045] Specifically, the microstrip feed line and the slot structure on the ground plane work together to excite the metasurface structure 103 through a phase difference, and the metasurface structure 103 excites and radiates two kinds of circularly polarized electromagnetic waves.

[0046] Furthermore, the microstrip feeder generates a precise path length difference through the specific relative position of its end and the slot structure. This path difference is converted into a fixed phase difference of approximately 90 degrees within the operating frequency band. This phase difference, together with the 45-degree symmetrical structure of the ground plane slot, establishes a sequentially rotating surface current distribution at each radiating unit of the upper metasurface. This converts the degenerate mode excited by the feed structure into a circularly polarized phase distribution on the radiation aperture. Finally, through the orderly arrangement of the metasurface units, this phase distribution is reconstructed into two highly directional circularly polarized beams with opposite rotation directions.

[0047] It should be noted that the physical field cooperative working mechanism enables the antenna to achieve a peak gain of over 6.68 dBi despite its compact structure.

[0048] Specifically, the microstrip feed lines are used to excite right-hand circularly polarized waves and left-hand circularly polarized waves, enabling the antenna to have dual circularly polarized radiation capabilities.

[0049] Furthermore, these two microstrip feed lines constitute an independently controllable dual-port feed network. When a signal is fed from either port alone, through the synergistic effect of the specific spatial orientation and phase relationship with the ground plane slot structure, circularly polarized radiation fields with opposite rotational characteristics can be excited in the upper metasurface structure 103. This design enables the antenna to independently generate electromagnetic waves with orthogonal radiation rotations within the same frequency band, achieving true polarization diversity while ensuring high port isolation and consistent radiation characteristics between the two circularly polarized operating modes.

[0050] It should be noted that the dual-port independent excitation mechanism enables the antenna to operate in transmit / receive full-duplex mode simultaneously, thereby improving the spectrum utilization of the communication system.

[0051] In use, two orthogonal microstrip feed lines are connected to two independent ports of the RF system. When a signal is input from either port, surface current is excited on the metasurface structure through the coupling effect between the microstrip line and the ground plane gap. The antenna radiates right-hand or left-hand circularly polarized waves respectively. The two ports can work simultaneously, maintaining an axial ratio of less than 3dB and a port isolation of greater than 20dB in the 2.0-2.7GHz frequency band, realizing polarization diversity communication. The entire system meets the miniaturization requirements of modern communication equipment while ensuring a gain of greater than 6.68dBi through a 5mm low-profile structure.

[0052] In summary, this invention achieves a multi-level collaborative structure by: a three-row, three-column periodic metasurface array above the first dielectric substrate 101; symmetrical composite slots etched on the ground plane; and orthogonal microstrip feeders on the lower layer. The metasurface array achieves beam focusing and high-gain radiation through spatial phase modulation. The composite slots are excited by non-contact coupling to generate dual orthogonal degenerate modes, resulting in circular polarization and widening the axial ratio bandwidth. The orthogonal microstrip feeders generate a phase difference through size optimization, ensuring high isolation and good standing wave ratio at both ports. The entire system achieves independent radiation with dual circular polarization within an extremely low profile, solving the problems of low gain, narrow bandwidth, and complex structure of traditional antennas.

[0053] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-gain low-profile dual-circularly polarized antenna based on metasurface, characterized in that: The antenna comprises a first dielectric plate (101), a second dielectric plate (102) arranged below the first dielectric plate (101), and a metasurface structure (103) arranged above the first dielectric plate (101). The metasurface structure (103) is periodically arranged by square metal patches in a three-row and three-column manner to form a planar array.

2. The metasurface-based high-gain low-profile dual-circularly-polarized antenna of claim 1, wherein: The antenna further comprises a ground plate arranged between the first dielectric plate (101) and the second dielectric plate (102), and a slot structure is etched in the center area of the ground plate for coupling feeding.

3. The high-gain low-profile dual-circularly-polarized antenna based on metasurface of claim 2, wherein: The slot structure is composed of a ring-shaped slot and two rectangular slots, the two rectangular slots are arranged in a central symmetry with respect to the center point of the ring-shaped slot, and the length direction of each rectangular slot is at an angle of 45 degrees with the horizontal direction.

4. The high-gain low-profile dual-circularly-polarized antenna based on metasurface of claim 3, wherein: The inner radius of the ring-shaped slot is 8 mm, the outer radius is 9.5 mm, the length of each rectangular slot is 6.5 mm, and the width is 0.5 mm.

5. The metasurface-based high-gain low-profile dual-circularly-polarized antenna of claim 4, wherein: The antenna further comprises two microstrip feed lines printed on the lower surface of the second dielectric plate (102), and the two microstrip feed lines are arranged in a spatial perpendicular manner.

6. The metasurface-based high-gain low-profile dual-circularly-polarized antenna of claim 5, wherein: The length of the microstrip feed line is 57.5 mm, and the width is 6 mm.

7. The high-gain low-profile dual-circularly-polarized antenna based on metasurface of claim 6, wherein, The overall shape of the antenna is a cuboid with a length of 100 mm, a width of 100 mm, and a height of 5 mm, the material of the first dielectric plate (101) is AD35 and the thickness is 3 mm, and the material of the second dielectric plate (102) is FR4 and the thickness is 2 mm.

8. The high-gain low-profile dual-circularly-polarized antenna based on metasurface of claim 7, wherein, The microstrip feed line cooperates with the slot structure on the ground plate, and the microstrip feed line and the slot structure on the ground plate jointly excite the metasurface structure (103) through phase difference, and two circularly polarized electromagnetic waves are excited and radiated on the metasurface structure (103).

9. The high-gain low-profile dual-circularly-polarized antenna based on metasurface of claim 8, wherein, The microstrip feed line is used for exciting right-handed circularly polarized wave and left-handed circularly polarized wave respectively, so as to make the antenna have a dual circularly polarized radiation function.

10. The high-gain low-profile dual-circularly-polarized antenna based on metasurface of claim 9, wherein, ​

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