A millimeter-wave dual-band circularly polarized metasurface antenna based on substrate-integrated waveguide feeding

Abstract

The present invention discloses a millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding, comprising a metasurface with irregular units and a SIW dual-frequency T-shaped slot antenna. The partially irregular metasurface is composed of a first dielectric substrate and a metasurface layer, which is disposed on the front of the first dielectric substrate and includes 13 square units of equal size arranged in a periodic pattern. The SIW dual-frequency T-shaped slot antenna comprises a second dielectric substrate, on which are disposed first, second, and third metallized through-holes penetrating a second upper metal cladding layer, a second dielectric substrate, and a second lower metal cladding layer. The second upper metal cladding layer is etched with a T-shaped coupling slot. The present invention applies characteristic mode theory to design a metasurface with dual-frequency circularly polarized radiation characteristics, and determines the feed position under the guidance of characteristic mode theory. This simple and efficient design achieves the performance of millimeter-wave dual-frequency circularly polarized radiation, and can be applied to the 5G millimeter-wave frequency band.

Description

Technical Field

[0001] The present invention belongs to the technical field of antennas, and more specifically, relates to a millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding, which can be used in 5G millimeter-wave communication systems. Background Art

[0002] As frequency increases, antenna transmission loss becomes increasingly severe. While traditional microstrip structures offer simplicity and ease of integration with external circuits, they suffer from high transmission loss, making them unsuitable for millimeter-wave antenna design. Traditional metal waveguides, while offering low loss, are bulky and difficult to integrate with external circuits, making them unsuitable for millimeter-wave antenna design. Therefore, scholars have proposed a new structure, substrate-integrated waveguides, for use in millimeter-wave antenna design. SIWs utilize periodic metal vias to prevent electromagnetic signal leakage, thereby reducing transmission loss. They combine the advantages of the low profile and ease of integration of microstrip structures with the low loss and high radiation efficiency of metal waveguides, making them widely used in millimeter-wave antenna design.

[0003] At the same time, with the continuous upgrading and expansion of communication equipment, many wireless communication systems operate in two frequency bands. In dual-band communication systems, compared to using broadband antennas or multiple single-frequency antennas, dual-band antennas offer the advantages of independent operation between the two frequency bands, reduced interference, and easy miniaturization. The increase in wireless communication devices has led to an increasingly complex electromagnetic environment. The increasing interference faced by various communication devices poses greater challenges to their stability. Circularly polarized antennas offer advantages such as resistance to polarization mismatch, reduced multipath loss, suppression of rain and fog interference, and resistance to multipath reflections. Consequently, they are increasingly widely used in modern communication systems.

[0004] However, most of the circularly polarized millimeter-wave antennas published so far are single-frequency circularly polarized antennas, and the published dual-frequency circularly polarized antennas still have problems such as complex feeding structure, narrow impedance bandwidth, or lack of clear explanation of working principles. Summary of the Invention

[0005] Based on the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate integrated waveguide feeding. The characteristic mode theory is applied to design a metasurface with dual-frequency circularly polarized radiation characteristics, and the feeding position is determined under the guidance of the characteristic mode theory. It is simple and efficient, and realizes the performance of millimeter-wave dual-frequency circularly polarized radiation. It can be applied to the 5G millimeter-wave frequency band and utilizes slot coupling feeding to avoid the complexity of the antenna feeding structure, and has the advantage of a simple feeding structure.

[0006] In order to solve the above technical problems, the present invention is implemented through the following technical solutions: The present invention provides a millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate integrated waveguide feeding, comprising a metasurface with irregular units in some units and a SIW dual-frequency T-shaped slot antenna, wherein the irregular metasurface in some units is composed of a first dielectric substrate and a metasurface layer, wherein the metasurface layer is arranged on the front of the first dielectric substrate and comprises 13 square units of the same size, which are arranged periodically; four small rectangular slots are etched in the middle unit, wherein the rectangular slot on the upper left and the rectangular slot on the lower right are equal in size, the rectangular slot on the lower left and the rectangular slot on the upper right are equal in size, and the rectangular slot on the upper left and the rectangular slot on the lower left are unequal in size; two rectangular corners are cut off on the left and right sides of the second row of left units, forming a vertically placed bow tie structure, and the sizes of the left cut corner and the right cut corner are equal; two rectangular corners are cut off on the top and bottom of the second row of right units, forming a horizontally placed bow tie structure, and the sizes of the top cut corner and the bottom cut corner are equal; The SIW dual-band T-shaped slot antenna includes a second dielectric substrate, on which are provided a first metallized through-hole, a second metallized through-hole, and a third metallized through-hole penetrating a second upper metal cladding, a second dielectric substrate, and a second lower metal cladding; the first metallized through-hole, the second dielectric substrate, the second upper metal cladding, and the second lower metal cladding form a rectangular SIW resonant cavity; a T-shaped slot is etched on the right side of the second upper metal cladding; a composite conversion structure is etched at the edge of the left side of the second upper metal cladding, forming a grounded coplanar waveguide-SIW converter with the second dielectric substrate, the third metallized through-hole, and the second lower metal cladding; the second metallized through-hole, the second dielectric substrate, the second upper metal cladding, and the second lower metal cladding form a rectangular SIW transmission line; the SIW resonant cavity is connected to the SIW transmission line, and a port excitation signal is transmitted to the SIW transmission line via the composite conversion structure, thereby feeding the SIW resonant cavity, and the T-shaped slot is used to couple and feed the metasurface.

[0007] Optionally, the side length of the square unit is 2.09 mm, and the unit spacing is 0.36 mm.

[0008] Furthermore, the length of the rectangular gap in the upper left and the rectangular gap in the lower right are 0.6 mm and the width is 0.35 mm; the length of the rectangular gap in the lower left and the rectangular gap in the upper right are 0.6 mm and the width is 0.4 mm; the position of each gap is the center position of the four sides of the middle unit.

[0009] Optionally, the length and width of the left cut corner of the second row left unit are both 0.88 mm; the length and width of the right cut corner of the second row left unit are both 0.6 mm; the length and width of the upper cut corner of the second row right unit are both 0.75 mm; and the length and width of the lower cut corner of the second row right unit are both 0.75 mm.

[0010] Furthermore, the diameter of the first metallized through hole is 0.4 mm, the distance between the centers of two adjacent first metallized through holes is 0.64 mm, and the length and width of the rectangular SIW resonant cavity are 6.42 mm and 8.4 mm respectively.

[0011] Optionally, the distance between the left end center point of the horizontal gap in the T-shaped gap and the center position of the upper through hole of the first metallized through hole is 1 mm, and the distance between the right end center point of the horizontal gap and the center position of the through hole on the right side of the first metallized through hole is 0.7 mm; the distance between the lower end center point of the longitudinal gap in the T-shaped gap and the center position of the lower through hole of the first metallized through hole is 0.75 mm, and the distance between the lower end center point of the longitudinal gap and the center position of the through hole on the right side of the first metallized through hole is 2.22 mm.

[0012] Optionally, the irregular metasurface of some units is located above the SIW dual-frequency slot antenna, the distance between the center of the middle unit and the center of the narrow side of the longitudinal slot in the T-shaped slot is 0.3 mm, and the distance between the centers of the two units in the second row and the center of the narrow side of the transverse slot in the T-shaped slot is 0.12 mm.

[0013] As described above, the millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate integrated waveguide feeding of the present invention applies characteristic mode theory to perform characteristic mode analysis on the initial metasurface. The characteristic mode clearly shows the inherent characteristic mode of the metasurface at the physical level, and determines the mode to be excited without a lot of engineering experience. The present invention applies characteristic mode theory and etches four small rectangular slots on the middle unit of the metasurface according to the characteristic current, model significance (MS), and characteristic angle (CA) of each mode. The two slots in opposite positions are equal in size, and there is a size difference between the two adjacent slots. The left and right sides of the second row of left units of the metasurface are cut off by two rectangular corners, forming a vertically placed bow tie structure. The upper and lower two rectangular corners of the second row of right units are cut off, forming a horizontally placed bow tie structure, which has the potential for dual-frequency circularly polarized radiation. The present invention determines the feeding position under the guidance of characteristic mode theory, which is simple and efficient. The present invention designs a SIW dual-frequency T-shaped slot antenna, and the SIW cavity is disturbed to the greatest extent by etching a T-shaped slot in the second upper metal cladding layer. Mode and The electric field distribution of the mode radiates energy outward through the slot to achieve dual-frequency operating bands; the present invention utilizes slot coupling feeding to avoid the complex antenna feeding structure and has the advantage of a simple feeding structure.

[0014] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description in combination with the preferred embodiments and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following briefly introduces the drawings of the embodiments.

[0016] Figure 1 Schematic diagram of the three-dimensional structure of the millimeter-wave dual-band circularly polarized metasurface antenna based on substrate-integrated waveguide feeding provided by the present invention, wherein (a) is a schematic diagram of the three-dimensional structure of the metasurface with irregular units; (b) is a schematic diagram of the three-dimensional structure of the SIW dual-band T-shaped slot antenna;

[0017] Figure 2 A top view of the irregular metasurface of some units;

[0018] Figure 3 This is a top view of the SIW dual-band T-shaped slot antenna;

[0019] Figure 4 A top view of the overall structure of the millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding provided by the present invention;

[0020] Figure 5 A graph showing the return loss parameters of the millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding provided by the present invention changing with frequency;

[0021] Figure 6 A graph showing the variation of axial ratio parameters with frequency for the simulated millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding provided by the present invention;

[0022] Figure 7 The xoz-plane radiation pattern simulated at 26 GHz for the millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding provided by the present invention;

[0023] Figure 8 The YOZ-surface pattern simulated at 26 GHz for the millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding provided by the present invention;

[0024] Figure 9 The xoz-plane radiation pattern simulated at 32.8 GHz for the millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding provided by the present invention;

[0025] Figure 10The YOZ surface radiation pattern of the millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate integrated waveguide feeding provided by the present invention is simulated at 32.8 GHz.

[0026] In the figure: 1-irregular metasurface of some units, 2-SIW dual-band T-shaped slot antenna, 11-metasurface layer, 12-first dielectric substrate, 111-middle unit, 1114-rectangular slot on the upper left, 1112-rectangular slot on the lower right, 1111-rectangular slot on the upper right, 1113-rectangular slot on the lower left, 112-second row of left units, 1121-left cut corner, 1122-right cut corner, 113-second row of right units, 1131-upper cut corner, 1132-lower cut corner, 21-second dielectric substrate, 22-second upper metal coating, 23-second lower metal coating, 24-T-shaped slot, 25-first metallized through hole, 26-second metallized through hole, 27-third metallized through hole, 241-horizontal slot, 242-vertical slot. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings, which serve as a part of this specification to make the principles, features and advantages of the present invention more clear.

[0028] like Figures 1 to 10 As shown, the millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate integrated waveguide feeding of the present invention includes a metasurface 1 with irregular units, a SIW dual-frequency T-shaped slot antenna 2, a first dielectric substrate 12, and a second dielectric substrate 21. The metasurface layer 11 is arranged on the front surface of the dielectric substrate 12, and the second upper metal coating 22 and the second lower metal coating 23 are respectively arranged on the front and back surfaces of the dielectric substrate 21.

[0029] The present invention adopts an analytical method to guide the design. Based on the characteristic mode theory and combined with the circular polarization radiation mechanism, the design of a dual-band circularly polarized antenna is realized. The main steps include:

[0030] Step 1: Perform eigenmode analysis on the initial metasurface. The metasurface layer 11 is periodically arranged with 13 square units, each with a side length of 2.09 mm and a unit spacing of 0.36 mm. Obtain the radiation characteristics of the first eight eigenmodes of the metasurface.

[0031] Step 2: Based on the characteristic current, MS value, and CA value of the desired mode, four small rectangular slots were etched into the middle unit 111. The rectangular slot 1114 on the upper left and the rectangular slot 1112 on the lower right of the middle unit are equal in size, 0.6 mm long and 0.35 mm wide. The rectangular slot 1111 on the upper right and the rectangular slot 1113 on the lower left of the middle unit are equal in size, 0.6 mm long and 0.4 mm wide. The slots are located at the center of the four sides of the middle unit. This achieves a metasurface design with the potential for low-frequency circularly polarized radiation.

[0032] Then, rectangular corners of different sizes are cut off on the left and right sides of the second row of left units 112, forming a vertically placed bow tie structure. Rectangular corners of different sizes are cut off on the top and bottom of the second row of right units 113, forming a horizontally placed bow tie structure. The left cut corner 1121 of the second row of left units has a length and width of 0.88 mm; the right cut corner 1122 has a length and width of 0.6 mm, the upper cut corner 1131 has a length and width of 0.6 mm, and the lower cut corner 1132 has a length and width of 0.75 mm, realizing a metasurface design with dual-frequency circularly polarized radiation characteristics.

[0033] Step 3: Determine the location of the excitation source based on the selection results from Step 2, and design a SIW dual-band T-shaped slot antenna 2 as the excitation source. Characteristic mode analysis shows that the strongest characteristic currents of the desired mode are located in the middle unit and the second row of units. The present invention uses the SIW dual-band T-shaped slot antenna 2 to couple and feed the irregular metasurface 1 with some units. The strongest electric fields of the SIW dual-band T-shaped slot antenna 2 should be located in the middle unit and the corner units.

[0034] The SIW dual-band T-shaped slot antenna 2 includes a second dielectric substrate 21, a first metallized through-hole 25, a second metallized through-hole 26, a third metallized through-hole 27, a composite conversion structure, a second upper metal cladding layer 22, and a second lower metal cladding layer 23. The first metallized through-hole 25, the second upper metal cladding layer 22, and the second lower metal cladding layer 23 form a rectangular SIW resonant cavity. The diameter of the first metallized through-hole is 0.4 mm, and the distance between the centers of two adjacent first metallized through-holes is 0.64 mm. The length of the rectangular SIW resonant cavity is 6.42 mm and the width is 8.4 mm. A T-shaped slot 24 is etched on the right side of the second upper metal cladding layer 22. By adjusting the position and size of the T-shaped slot 24, the SIW cavity is disturbed to the greatest extent. Mode and The electric field distribution of the mode is optimized, thereby obtaining good dual-frequency radiation characteristics. The T-shaped slot 24 includes a horizontal slot 241 and a vertical slot 242. The distance between the left center point of the horizontal slot 241 and the center of the upper hole of the first metallized through-hole 25 is 1 mm, and the distance between the right center point of the horizontal slot 241 and the center of the right hole of the first metallized through-hole 25 is 0.7 mm. The distance between the lower center point of the vertical slot 242 and the center of the lower hole of the first metallized through-hole 25 is 0.75 mm, and the distance between the lower center point of the vertical slot 242 and the center of the right hole of the first metallized through-hole 25 is 2.22 mm.

[0035] The composite conversion structure is etched at the left edge of the second upper metal cladding 22, and forms a grounded coplanar waveguide-SIW converter with the third metallized through-hole 27 and the second lower metal cladding 23; the second metallized through-hole 26 forms a rectangular SIW transmission line with the second upper metal cladding 22 and the second lower metal cladding 23; the SIW resonant cavity is connected to the SIW transmission line, and the port excitation signal is transmitted to the SIW transmission line through the composite conversion structure, thereby feeding the SIW resonant cavity, and using the T-shaped gap to feed the metasurface coupling.

[0036] Step 4: Fine-tune the structure obtained in step 3 to achieve a good dual-band circularly polarized antenna design.

[0037] A partially irregular metasurface 1 is positioned above a SIW dual-band T-slot antenna 2. The center of the middle unit 111 is 0.3 mm from the center of the narrow side of the longitudinal slot 242 in the T-slot. The center of the two units in the second row is 0.12 mm from the center of the narrow side of the transverse slot 241 in the T-slot. The SIW dual-band T-slot antenna is used to couple and feed the metasurface, achieving a dual-band circularly polarized antenna design.

[0038] Reference Figure 5 、 6 , respectively show the return loss parameters and axial ratio parameters of the antenna simulation of the present invention as a function of frequency. It can be seen from the figure that the antenna of the present invention operates at 25.48 GHz~26.70 GHz and 31.90 GHz~33.71 GHz and is circularly polarized radiation.

[0039] The above simulations show that the antenna of the present invention applies the characteristic mode theory without the need for a lot of engineering experience to realize the design of a metasurface with dual-frequency circularly polarized radiation characteristics. Under the guidance of the characteristic mode theory, the feeding position is determined, which is simple and efficient. A simple SIW dual-frequency T-shaped slot antenna is designed to couple the feeding of the metasurface to realize the design of a dual-frequency circularly polarized radiation antenna, which can be applied to the 5G millimeter wave frequency band.

[0040] The millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate integrated waveguide (SIW) feeding disclosed in the present invention is characterized by designing a metasurface with dual-frequency circularly polarized radiation potential based on the characteristic mode theory, and designing a SIW dual-frequency T-shaped slot antenna to couple and feed the improved metasurface to realize the antenna's dual-frequency circularly polarized radiation. The irregular metasurface layer of some units of the present invention is arranged on the upper surface of the first dielectric substrate 12. There are a total of 13 square units arranged periodically in five rows, and four small rectangular slots are etched on the middle unit 111. The two units in the second row are bow tie structures and are orthogonal in position, realizing dual-frequency circularly polarized radiation; the SIW dual-frequency T-shaped slot antenna 2 includes a second dielectric substrate 21, a first metallized through hole 25, a second metallized through hole 26, a third metallized through hole 27, a composite conversion structure, a second upper metal cladding 22, and a second lower metal cladding 23. The second dielectric substrate 21 is provided with a first metallized through hole 25 for forming a rectangular SIW resonant cavity, and the second upper metal cladding 22 is etched with a T-shaped coupling slot for coupling and feeding the metasurface; the present invention achieves the performance of millimeter wave dual-frequency circularly polarized radiation and can be applied to the 5G millimeter wave frequency band.

[0041] The above description is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principles of the present invention. These improvements and changes are also considered to be within the scope of protection of the present invention.

[0042] Although the present invention has been described with reference to preferred embodiments, various modifications may be made thereto and equivalent components may be substituted without departing from the scope of the present invention. In particular, the various technical features described in the various embodiments may be combined in any manner as long as no structural conflicts exist. The present invention is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A millimeter-wave dual-band circularly polarized metasurface antenna based on substrate-integrated waveguide feeding, comprising a metasurface with irregular elements and a SIW dual-band T-shaped slot antenna, characterized by: The partially irregular metasurface is composed of a first dielectric substrate and a metasurface layer, wherein the metasurface layer is provided on the front surface of the first dielectric substrate and includes 13 square units of the same size, which are arranged periodically; four small rectangular slits are etched in the middle unit, wherein the rectangular slit on the upper left is equal to the rectangular slit on the lower right, the rectangular slit on the lower left is equal to the rectangular slit on the upper right, and the rectangular slit on the upper left is unequal to the rectangular slit on the lower left; The left and right sides of the second row of left units have two rectangular corners cut off, forming a vertically placed bow tie structure, with the left and right cut corners being equal in size; The upper and lower rectangular corners of the right unit in the second row are cut off, forming a horizontal bow tie structure, with the upper and lower cut corners being equal in size. The SIW dual-band T-shaped slot antenna includes a second dielectric substrate, on which are arranged a first metallized through hole, a second metallized through hole, and a third metallized through hole penetrating the second upper metal cladding, the second dielectric substrate, and the second lower metal cladding; The first metallized through hole, the second dielectric substrate, the second upper metal cladding layer, and the second lower metal cladding layer form a rectangular SIW resonant cavity; a T-shaped gap is etched on the right side of the second upper metal cladding layer; A composite conversion structure is etched at the left edge of the second upper metal cladding layer, forming a grounded coplanar waveguide-SIW converter with the second dielectric substrate, the third metallized through-hole, and the second lower metal cladding layer. The second metallized through-hole, the second dielectric substrate, the second upper metal cladding layer, and the second lower metal cladding layer form a rectangular SIW transmission line. The SIW resonant cavity is connected to the SIW transmission line, and the port excitation signal is transmitted to the SIW transmission line through the composite conversion structure, thereby feeding the SIW resonant cavity, and the T-shaped slot is used to couple the feed to the metasurface. The length of the rectangular gap in the upper left and the rectangular gap in the lower right are 0.6 mm and the width is 0.35 mm; the length of the rectangular gap in the lower left and the rectangular gap in the upper right are 0.6 mm and the width is 0.4 mm; the position of each gap is the center position of the four sides of the middle unit; The irregular metasurface of some units is located above the SIW dual-frequency slot antenna, the distance between the center of the middle unit and the center of the narrow side of the longitudinal slot in the T-shaped slot is 0.3 mm, and the distance between the centers of the two units in the second row and the centers of the narrow sides of the transverse slot in the T-shaped slot is 0.12 mm.

2. The millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding according to claim 1, characterized in that: The side length of the square unit is 2.09 mm, and the unit spacing is 0.36 mm.

3. The millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding according to claim 1, characterized in that: The length and width of the left cut corner of the second row left unit are both 0.88 mm; the length and width of the right cut corner of the second row left unit are both 0.6 mm; The length and width of the upper cut corner of the second row right unit are both 0.75 mm; the length and width of the lower cut corner of the second row right unit are both 0.75 mm.

4. The millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding according to claim 1, characterized in that: The diameter of the first metallized through hole is 0.4 mm, the distance between the centers of two adjacent first metallized through holes is 0.64 mm, and the length and width of the rectangular SIW resonant cavity are 6.42 mm and 8.4 mm respectively.

5. The millimeter-wave dual-frequency circularly polarized metasurface antenna based on substrate-integrated waveguide feeding according to claim 1, characterized in that: The distance between the left end center point of the transverse slot in the T-shaped slot and the center position of the upper through hole of the first metallized through hole is 1 mm, and the distance between the right end center point of the transverse slot and the center position of the right through hole of the first metallized through hole is 0.7 mm; The distance between the lower center point of the longitudinal slot in the T-shaped slot and the center of the lower through hole of the first metallized through hole is 0.75 mm, and the distance between the lower center point of the longitudinal slot and the center of the right through hole of the first metallized through hole is 2.22 mm.

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