A metasurface-based rectangular-to-circular waveguide mode conversion device and method

Abstract

The application discloses a kind of based on super surface rectangular waveguide mode conversion device and method, for realizing TE 10 -TE 20 -TE 01 Metal waveguide mode conversion, rectangular waveguide mode conversion device includes first to fifth section waveguide, and first to second super surface structure, wherein: first, third, fifth section waveguide is used to transmit rectangular waveguide TE 10 Mode, rectangular waveguide TE 20 Mode and circular waveguide TE 01 Mode, second, fourth section waveguide is used to generate multimode interference;First super surface structure is used to realize TE 10 Mode to TE 20 Mode conversion, second super surface structure is used to realize TE 20 Mode to TE 01 Mode conversion;Second section waveguide, first super surface structure and third section waveguide constitute TE 10 -TE 20 Mode converter;Fourth section waveguide and second super surface structure constitute TE 20 -TE 01 Mode converter.The application utilizes the regulation and control ability of super surface to electromagnetic field, and rectangular waveguide TE 10 Mode can be converted into circular waveguide TE 01 Mode in smaller space.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metasurface technology and vacuum electron device technology, and particularly relates to a metasurface-based mode conversion device and method. BACKGROUND

[0002] Mode converters are indispensable components of high-power devices. They can realize the conversion from the fundamental mode to the high-order mode and from the rectangular waveguide to the circular waveguide, and are widely used in millimeter wave antennas, satellite communication transmitters, high-power satellite radars and other application fields. The circular waveguide TE 01 mode has a wide range of applications in vacuum electron devices, especially in gyrotrons, because of its azimuthally symmetric electric field and low energy loss near the inner wall. The rectangular waveguide high-order TE m0 mode (m = 2, 3, 4,...) has a high application prospect in microwave devices due to its large size, simple processing and high power capacity. The high-order mode is usually converted from the low-order mode, that is, the circular waveguide TE 11 mode and the rectangular waveguide TE 10 mode. Therefore, the conversion from the fundamental mode to the high-order mode is crucial. There are various methods for converting the rectangular waveguide fundamental mode to the circular waveguide high-order mode. The marie-type mode converter is a common conversion method. On this basis, the TE 10 -TE 01 mode conversion device with a long waveguide structure gradient also has many applications. It is worth mentioning that the TE 20 mode can be used as a classic transition mode for converting the rectangular waveguide TE 10 mode to the circular waveguide TE 01 mode. In addition, there is a method for converting the gyrotron TE 01 mode based on a 1-4-1 power divider. It is known that there is a high degree of correlation between the modes of the rectangular waveguide, and the conversion is one-dimensional. The TE 10 -TE 20 mode can be converted by a gradient waveguide designed by microwave theory.

[0003] In the current field of metal waveguide mode conversion, there are the following deficiencies: first, the waveguide design for mode conversion is too long and not compact enough, occupying a large space area. Second, the design of the waveguide structure is complex, requiring too many parameters to be determined, which is difficult to manufacture due to the large amount of calculation. Therefore, there is an urgent need for a simple and compact mode conversion device.

[0004] In recent years, metasurfaces have attracted more and more attention due to their ultra-small design structure and strong ability to manipulate the phase, amplitude and polarization of electromagnetic waves. They can adjust free-space light and gradually extend their effects to the field of integrated optics. In addition, in the field of optical fibers, metasurface mode converters can convert the transverse electric field mode TE01 or transverse magnetic field mode TM 01 mode conversion to the basic mode LP of the orthogonal polarization 01 Many related researches have been carried out in the field of vacuum electronics. For example, based on the phase control ability of the metasurface, the TE 01 mode can realize the conversion to the circularly polarized Gaussian beam. Therefore, the metasurface can be applied in the design of small microwave power modules. SUMMARY

[0005] The purpose of the present application is to provide a metasurface-based rectangular-to-circular waveguide mode conversion device and method.

[0006] The technical solution for achieving the purpose of the present application is: a metasurface-based rectangular-to-circular waveguide mode conversion device, which is used to realize TE 10 -TE 20 -TE 01 metal waveguide mode conversion, including first to fifth segment waveguides, and first to second metasurface structures, wherein:

[0007] The first, third and fifth segment waveguides are respectively used to transmit the rectangular waveguide TE 10 mode, the rectangular waveguide TE 20 mode and the circular waveguide TE 01 mode, and the second and fourth segment waveguides are used to generate multi-mode interference; the first metasurface structure is used to realize the conversion of the TE 10 mode to the TE 20 mode, and the second metasurface structure is used to realize the conversion of the TE 20 mode to the TE 01 mode; the second segment waveguide, the first metasurface structure and the third segment waveguide constitute a TE 10 -TE 20 mode converter; the fourth segment waveguide and the second metasurface structure constitute a TE 20 -TE 01 mode converter.

[0008] Further, the first segment waveguide is a rectangular waveguide with a size of 3.56mm×7.12mm×20mm, and the material of the first segment waveguide is metal copper with an electrical conductivity of 2e7 S / m.

[0009] Further, the second segment waveguide is a rectangular waveguide with a size of 3.56mm×14.23mm×5.5mm, and the material of the second segment waveguide is metal copper with an electrical conductivity of 2e7 S / m.

[0010] Further, the third segment waveguide is a rectangular waveguide with a size of 3.56mm×14.23mm×5mm, and the material of the third segment waveguide is metal copper with an electrical conductivity of 2e7 S / m.

[0011] Further, the fourth section waveguide is a circular waveguide, the length of the fourth section waveguide is 5.6mm, and the radius of the fourth section waveguide is 8mm.

[0012] Further, the fifth section waveguide is a circular waveguide, the length of the fifth section waveguide is 0.5mm, and the radius of the fifth section waveguide is 8mm.

[0013] Further, the first metasurface structure includes 8 perforated structure units and 8 non-perforated structure units, which are located on the left and right sides, respectively, the metasurface unit structure period is 1.77mm, the height is 3mm, the perforated radius of the perforated metasurface unit structure is 0.8mm, and the material of the first metasurface structure is aluminum oxide, and the dielectric constant ε thereof is 9.4.

[0014] Further, the second metasurface structure is a metal-dielectric-metal three-layer structure, the two metal layers are the same, each metal structure is composed of 9 metal rods rotating and overlapping, the length of the metal rod is 16mm, the width is 0.5mm, and the thickness is 5um; the distribution characteristics of the 9 metal rods are that the midpoints of the 9 metal rods coincide with the center of the dielectric layer structure, the included angle between each metal rod is 90°, the overall distribution of the metal structure is radial, and the length direction of the metal rod is distributed along the radial direction; the dielectric layer is aluminum oxide, the dielectric constant ε thereof is 9.4, the thickness is 1.6mm, and the radius is 17mm.

[0015] Further, the mode conversion process is as follows:

[0016] The TE 10 mode excited by the incident port is converted into the TE 20 mode through the first section waveguide, the second section waveguide and the first metasurface structure. 20 The TE 01 mode is modulated by the second metasurface structure and finally generates the circular waveguide TE 10 mode through the third section waveguide and the fourth section waveguide.

[0017] A kind of based on metasurface rectangular circular waveguide mode conversion method, by the based on metasurface rectangular circular waveguide mode conversion device, the mode conversion of TE 10 -TE 01 .

[0018] Compared with the prior art, the above technical scheme has the following technical effects: by using the regulation and control ability of metasurface on electromagnetic field, rectangular waveguide TE 10 mode is converted into circular waveguide TE 01A device and method for modulating guided electromagnetic waves by combining a transition waveguide with a metasurface structure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the modes appearing in this invention and their transformation process; according to the transformation process, they are as follows: TE 10 Patterns, TE 20 Mode, TE 20 Patterns, TE 21 Mode, TE 01 model.

[0020] Figure 2 TE in this invention 10 -TE 01 A schematic diagram of the mode converter.

[0021] Figure 3 The implementation class TE designed in this invention 20 Mode conversion to TE 20 The diagrams show the metasurface unit structure and topology of the metasurface structure; where (a) is the metasurface unit structure diagram and (b) is the topology of the first metasurface structure.

[0022] Figure 4 This is a graph showing the relationship between the ratio of the radius of the metasurface unit structure to the wavelength and the phase in this invention.

[0023] Figure 5 TE in this invention 10 -TE 20 S-parameters of the mode converter and energy distribution within the waveguide.

[0024] Figure 6 The different radius values ​​of the metasurface unit structure in this invention are related to TE. 10 -TE 20 A graph showing the relationship between the S-parameters of the mode converter.

[0025] Figure 7 The implementation class TE designed in this invention 21 Mode conversion to TE 01 The topological diagrams of the metasurface structure and the electric field intensity distribution when placed inside the waveguide are shown; where (a) is the topological diagram of the second metasurface structure and (b) is the electric field intensity distribution inside the waveguide.

[0026] Figure 8 TE in this invention 20 -TE 01 S-parameters of the mode converter and energy distribution within the waveguide.

[0027] Figure 9 In this invention, TE 10 -TE 20 Mode converter and TE 20 -TE 01 S-parameters after mode converter and energy distribution within waveguide. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] This invention discloses a rectangular-circular waveguide mode conversion device based on a metasurface. Utilizing the electromagnetic field manipulation capability of a metasurface, it realizes rectangular waveguide mode conversion (TE) within a relatively small space. 10 Mode changed to circular waveguide TE 01 The mode modulates guided electromagnetic waves by combining transition waveguides with metasurface structures.

[0030] A metasurface-based rectangular-circular waveguide mode conversion device employing TE 10 -TE 20 -TE 01 The metallic waveguide mode conversion system consists of five waveguide segments and two metasurface structures. The first, third, and fifth waveguide segments are used to transmit rectangular waveguide TE signals. 10 Mode, rectangular waveguide TE 20 Modes and Circular Waveguide TE 01 The second and fourth waveguides are used to generate multimode interference. The first metasurface is used to realize TE. 10 Mode to TE 20 Mode transformation. A second metasurface is used to realize TE. 20 Mode to TE 01 Pattern transformation.

[0031] The second waveguide, the first metasurface structure, and the third waveguide constitute TE. 10 -TE 20 Mode converter. The second and third waveguide segments are rectangular waveguides. The dimensions of the second waveguide segment are 3.56mm × 14.23mm × 5.5mm. The dimensions of the third waveguide segment are 3.56mm × 14.23mm × 5mm. The three waveguide segments are made of metallic copper with a conductivity of 2e7 S / m. The first metasurface structure consists of 8 perforated structural units and 8 non-perforated structural units, located on the left and right sides respectively. Its material is alumina with a dielectric constant ε of 9.4. The metasurface unit structure has a period of 1.77mm and a height of 3mm. The perforation radius of the perforated metasurface unit structure is 0.8mm.

[0032] The fourth waveguide and the second metasurface structure constitute TE.20 -TE 01 Mode converter. The fourth waveguide is a circular waveguide with a length of 5.6 mm and a radius of 8 mm. The second metasurface unit structure consists of a three-layer structure of metal-dielectric-metal. The two metal layers have the same structure. It is composed of 9 metal rods, each 16 mm long, 0.5 mm wide, and 5 μm thick. The nine metal rods are distributed as follows: the midpoints of the nine metal rods coincide with the center of the dielectric layer structure, and the angle between each metal rod is 90°, meaning that the overall distribution is radial, with the length of the metal rods distributed radially.

[0033] The first waveguide segment is a rectangular waveguide with dimensions of 3.56mm × 7.12mm × 20mm, and it is used to transmit TE signals. 10 Mode. The fifth waveguide segment is a circular waveguide with a length of 0.5 mm and a radius of 8 mm, which is used for transmission TE. 01 The dielectric layer is made of aluminum oxide with a dielectric constant ε = 9.4, a thickness of 1.6 mm, and a radius of 17 mm.

[0034] The five segmented waveguides and two metasurface structures constitute the TE 10 -TE 20 -TE 01 The mode conversion process of the metallic waveguide mode conversion system is as follows:

[0035] rectangular waveguide TE excited at the incident port 10 The mode is transmitted from the first waveguide to the second waveguide, where the electromagnetic field generates multimode interference, thus producing a TE-like signal. 20 The mode, after passing through the first metasurface structure, is converted into a rectangular waveguide TE. 20 Pattern, generating TE 20 The mode is transmitted through the third and fourth waveguides to the second metasurface, where it is modulated by the second metasurface structure to ultimately generate the circular waveguide TE. 01 Mode; TE 10 The mode is transmitted through the fifth waveguide and finally output from the output port.

[0036] Example

[0037] Rectangular waveguide TE 10 Modes and Circular Waveguide TE 01 The modes are very different, therefore a rectangular waveguide TE is required. 20 The mode serves as a transitional mode to achieve the conversion between two modes, such as... Figure 1As shown, L1, a, and b represent the length, width, and height of waveguide 1, respectively; L2, w1, and h1 represent the length, width, and height of waveguide 2, respectively; L3, w2, and h2 represent the length, width, and height of metasurface 1, respectively; L4 represents the length of waveguide 3, whose width and height are the same as those of waveguide 2; L5 represents the length of waveguide 4, and R represents the radius of waveguide 4; L6 represents the length of metasurface 2; and L7 represents the length of waveguide 5, whose radius is the same as that of waveguide 4. TE 20 Mode generation can be achieved through a dual-image generated by waveguide multimode interference and metasurface phase modulation.

[0038] The designed new TE 10 -TE 20 -TE 01 Metal waveguide mode conversion system such as Figure 2 As shown. Waveguide 1, waveguide 3, and waveguide 5 are used to transmit TE signals. 10 TE 20 and TE 01 Waveguides 2 and 4 are used to generate multimode interference.

[0039] The designed TE 10 -TE 01 The mode converter consists of two parts. The first part is transmitted via TE... 10 -TE 20 Mode converter from rectangular waveguide TE 10 Mode conversion to rectangular waveguide TE 20 The mode converter consists of waveguide 1, waveguide 2, metasurface 1, and waveguide 3. The TE signal is excited by port 1. 10 The mode is converted to TE via waveguide 1, waveguide 2, and metasurface 1. 20 The pattern. The second part is through TE. 20 -TE 01 Mode converter from TE 20 Mode conversion to TE 01 The mode converter consists of waveguide 4, metasurface 2, and waveguide 5. TE 20 The mode is converted into the desired circular waveguide TE via waveguide 4 and metasurface 2. 01 The mode is finally output by waveguide 5.

[0040] In TE 10 -TE 20 During the mode conversion process, a metasurface 1 composed of perforated alumina unit structures and solid alumina structures is used to achieve the transition from TE. 10 Mode to TE 20Mode switching. The internal dimensions of waveguide 1 and waveguide 2 are 3.56mm × 7.12mm × 20mm and 3.56mm × 14.23mm × 5.5mm, respectively. TE 10 and TE 20 The electric field of the mode can be characterized by the following formulas: In the formula, ω is the frequency of the electromagnetic wave, and A 10 and A 20 Let be the electromagnetic field strength, kc be the cutoff wave number, and β be the propagation constant. Waveguide 1 and waveguide 2 were simulated using CST electromagnetic simulation software. The simulated electric field distribution approximates the standard TE. 20 The mode. However, the polarization directions on both sides are the same, which can be represented as: It is important to note that the absolute value in the formula indicates that the polarization directions of the electric field on both sides of the central axis of waveguide section 2 are the same. Therefore, this formula can be transformed into a standard TE... 20 The model can leverage the ability of metamaterials to flexibly control the phase.

[0041] Figure 3 (b) The designed alumina metasurface 1 structure consists of 16 unit structures and an outer dielectric layer, with 8 perforated structures on the left and 8 non-perforated structures on the right. The dielectric constant ε of the alumina is 9.4. The metasurface unit structure has a period of 1.77 mm and a height of 3 mm, as shown below. Figure 3 As shown in (a), the unit structure was simulated using CST electromagnetic simulation software. The relationship between r / λ and phase is shown in the figure. Figure 4 As shown, the curves corresponding to different frequencies are basically parallel, indicating that the designed metasurface has stable performance. To achieve an approximate π phase shift in the 29-34 GHz frequency range and obtain better simulation results, the perforated portion of the designed metasurface 1 has a radius of 0.8 mm. At a center frequency of 32 GHz, a 0.8 mm radius aperture cannot achieve a complete π phase transition. However, it can still achieve mode switching. This is because there is a certain phase deviation in the multimode interference before metasurface 1, preventing the achievement of a complete TE-like phase transition. 20 model.

[0042] The modulation process of the electromagnetic field in a waveguide can be summarized as follows: When an electromagnetic wave passes through the transition sections at both ends of the waveguide, the electromagnetic field is split into two directions due to the abrupt change in the waveguide structure. It can be clearly seen that when it passes through the precisely designed metasurface 1 structure, the electromagnetic wave on the left is modulated by metasurface 1, and the phase of the wave passing through the left side is π more than that of the wave passing through the right side. Finally, when the guided electromagnetic wave has completely passed through the metasurface structure, a perfect TE signal can be achieved. 20 Pattern. TE 10 -TE 20 The simulation results of the S-parameters of the mode transformation are as follows: Figure 5 As shown. Optimized reflection S11 It exhibits good performance in the 31.5–32.9 GHz frequency range, with a conversion efficiency S0. 21 It exhibits good conversion performance in the frequency range of 31.6–33.4 GHz.

[0043] It is worth noting that the simulation results also show that the waveguide length (L4) does not affect the s-parameters, which indicates that the system can be more compact when a shorter L4 is used.

[0044] TE20-TE01 mode conversion and phase modulation-based TE 10 -TE 20 Different mode conversions, TE 20 -TE 01 The mode conversion employs a metal-dielectric-metal metasurface structure. The metal structure is made of copper with a conductivity of 2e7 S / m.

[0045] TE 01 The electric field distribution can be expressed as: E ρ =0, E z =0. In the formula, A represents the electric field intensity, and J′0 represents the zeroth-order Bessel function of the first kind. It can be seen that the polarization direction of the electric field at each point in the waveguide is perpendicular to the radial direction. Therefore, the principle of metal layer design is a radially oriented metal structure. For example... Figure 7 As shown in (a), in the designed metal-dielectric-metal metasurface structure, the metal layer consists of nine identical metal rods, each 16 mm long and 0.5 mm wide. All metal blocks have the same center point, located at the center of the second layer in the XY plane, and the spacing between adjacent metal sheets is 20°. The bottom and top layers are designed identically. The dielectric layer is aluminum oxide with a dielectric constant ε = 9.4, a thickness of 1.6 mm, and a radius of 17 mm.

[0046] As is well known, electromagnetic waves are transmitted when their polarization direction is the same as the distribution direction of the metal sheet. Conversely, they are reflected when their polarization direction is opposite to the distribution direction of the metal sheet. Therefore, the metal layer of metasurface 2 is radially oriented, similar to TE. 01 The electric field polarization directions of the modes are completely opposite. For example... Figure 7 (a) is shown. TE 20 -TE 01 Simulation results of the mode converter are as follows Figure 8 As shown. Optimized S 11 It exhibits good performance in the 31.6–32.6 GHz frequency range. 21 It exhibits good performance in the frequency range of 31.4–33 GHz.

[0047] The parameters of the two metasurface structures are adjusted to ensure that their optimal operating frequencies are the same. This way, when these two converters are integrated into a single system, it is possible to achieve the same operating frequency from a rectangular waveguide TE converter. 10 Mode to Circular Waveguide TE 01 The highest conversion rate of the pattern.

[0048] Five segmented waveguides and two metasurface structures are connected to a single system. The entire mode transformation process is as follows: When the TE signal excited at the incident port... 10 After passing through waveguide 2 and metasurface 1, the mode is converted to TE. 20 Pattern. Generated TE 20 After passing through metasurface 2, waveguide 3, and waveguide 4, the mode is modulated by metasurface 2 to finally generate the circular waveguide TE. 01 The latter, via waveguide 5, is ultimately output from port 2. TE 10 -TE 01 The mode converter has a total length of 20.7 mm.

[0049] Figure 9 This is the result of a simulation of the entire structure. The optimized S... 11 At 31.8 ～ It has a small reflection coefficient in the 32.9 GHz frequency range, S 21 At 31.4 ～ It exhibits a high conversion factor within the 33 GHz frequency range. Compared to existing research, it achieves a high transmission factor within a relatively narrow but acceptable bandwidth. Its conversion efficiency reaches a high level compared to other similar works, and its overall structure is very compact.

[0050] The structure in this embodiment is composed of alumina TE 10 -TE 20 Metasurface mode converter, copper-alumina-copper TE 20 -TE 01 It consists of a mode converter and several waveguide segments. TE 10 -TE 20 The metasurface mode converter consists of eight perforated alumina metasurface unit structures and eight solid alumina material structures. TE 20 -TE 01 The mode converter consists of an aluminum oxide dielectric layer and copper films plated on both sides. Input port 1 excites TE. 10 The mode is transmitted from waveguide 1 to waveguide 2, and self-imaging is generated due to multimode interference to form a TE-like pattern. 20 Pattern. TE 10 -TE 20 The mode converter achieves phase transformation of π by modulating the phase, ultimately realizing TE. 10 -TE20 Transformation. The resulting TE. 20 The mode is transmitted from waveguide 3 to waveguide 4 to generate a TE-like pattern. 21 Pattern, TE 21 Model via TE 20 -TE 01 The mode converter generates a phase redistribution to achieve TE. 20 -TE 01 Transformation. The cascading of two metasurface structures with a transition waveguide structure ultimately achieves TE. 10 -TE 01 Mode transformation.

[0051] In summary, this invention, by replacing complex waveguide structures with metasurface structures, paves the way for the miniaturization and integration of mode converters. This design approach can also be extended to various applications, including the design of vacuum electronics and satellite-specific mode transmitters.

[0052] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A rectangular-circular waveguide mode conversion device based on a metasurface, characterized in that, Used to implement TE 10 -TE 20 -TE 01 The mode conversion of the metallic waveguide includes the first to fifth waveguide segments and the first to second metasurface structures, wherein: The first, third, and fifth waveguide segments are used to transmit rectangular waveguide TE signals. 10 Mode, rectangular waveguide TE 20 Modes and Circular Waveguide TE 01 The second and fourth waveguides are used to generate multimode interference; the first metasurface structure is used to realize TE. 10 Model to TE 20 Mode transformation, the second metasurface structure is used to realize TE 20 Model to TE 01 Mode transformation; the second waveguide, the first metasurface structure, and the third waveguide constitute the TE. 10 -TE 20 Mode converter; the fourth waveguide and the second metasurface structure constitute the TE 20 -TE 01 Mode converter; The first metasurface structure includes 8 perforated structural units and 8 non-perforated structural units, located on the left and right sides respectively; the second metasurface structure is a three-layer structure of metal-dielectric-metal, with the two metal layers having the same structure. Each metal layer is composed of 9 metal rods that are rotated and overlapped. The midpoints of the 9 metal rods coincide with the center of the dielectric layer structure. The included angle between each metal rod is 20°. The overall distribution of the metal structure is radial, with the length of the metal rods distributed radially.

2. The metasurface-based rectangular waveguide mode conversion device according to claim 1, characterized in that, The first waveguide is a rectangular waveguide with dimensions of 3.56mm × 7.12mm × 20mm. The material of the first waveguide is metallic copper with a conductivity of 2e7S / m.

3. The rectangular-circular waveguide mode conversion device based on a metasurface according to claim 1, characterized in that, The second waveguide is a rectangular waveguide with dimensions of 3.56 mm × 14.23 mm × 5.5 mm. The material of the second waveguide is metallic copper with a conductivity of 2e7 S / m.

4. The rectangular-circular waveguide mode conversion device based on a metasurface according to claim 1, characterized in that, The third waveguide is a rectangular waveguide with dimensions of 3.56 mm × 14.23 mm × 5 mm. The material of the third waveguide is metallic copper with a conductivity of 2e7 S / m.

5. The rectangular-circular waveguide mode conversion device based on a metasurface according to claim 1, characterized in that, The fourth waveguide is a circular waveguide with a length of 5.6 mm and a radius of 8 mm.

6. The metasurface-based rectangular waveguide mode conversion device according to claim 1, characterized in that, The fifth waveguide is a circular waveguide with a length of 0.5 mm and a radius of 8 mm.

7. The rectangular-circular waveguide mode conversion device based on a metasurface according to claim 1, characterized in that, In the first metasurface structure, the metasurface unit structure has a period of 1.77 mm and a height of 3 mm. The perforation radius of the perforated metasurface unit structure is 0.8 mm. The material of the first metasurface structure is alumina, and its dielectric constant ε is 9.

4.

8. The rectangular-circular waveguide mode conversion device based on a metasurface according to claim 1, characterized in that, In the second metasurface, the metal rod has a length of 16 mm, a width of 0.5 mm, and a thickness of 5 μm; the dielectric layer is aluminum oxide with a dielectric constant ε=9.4, a thickness of 1.6 mm, and a radius of 17 mm.

9. The metasurface-based rectangular waveguide mode conversion device according to claim 1, characterized in that, The mode conversion process is as follows: TE excited by the incident port 10 After passing through the first waveguide, the second waveguide, and the first metasurface structure, the mode is converted to TE. 20 Pattern, generating TE 20 After passing through the second metasurface structure, and then through the third and fourth waveguides, the mode is modulated by the second metasurface structure to finally generate the circular waveguide TE. 01 Mode; TE 10 The mode is transmitted through the fifth waveguide and finally output from the output port.

10. A method for mode transformation of a rectangular circular waveguide based on a metasurface, characterized in that, The mode conversion device based on metasurfaces according to any one of claims 1-9 is used to realize TE. 10 -TE 01 Mode transformation.

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