A frequency-division multi-mode OAM metasurface with the same divergence angle

Abstract

The present invention discloses a frequency-division same divergence angle multi-mode OAM metasurface, comprising: an extremely narrowband spatial filtering module and a multi-mode OAM modulation module; the extremely narrowband spatial filtering module is composed of multiple layers of frequency selection structure surfaces with narrowband characteristics, each layer of the frequency selection structure surface is composed of narrowband response structure units, which are used to select electromagnetic waves of specific spatial frequencies, and realize the division and frequency division of electromagnetic wave excitation signals of the multi-mode OAM modulation module by the incident wave; the multi-mode OAM modulation module is arranged on the surface of the extremely narrowband spatial filtering module, and the multi-mode OAM modulation module is composed of phase structure surface units, which are used to receive the division and frequency division of electromagnetic wave excitation signals transmitted by the extremely narrowband spatial filtering module, and modulate the electromagnetic waves incident to different regions into different mode OAM beams, and then make the OAM beams of different frequencies and modes radiate in a specific spatial region. The present invention improves the overall performance of the metasurface, and the divergence angles of different mode OAM beams are the same.

Description

Technical Field

[0001] The present invention relates to the field of OAM modulation metasurface design, and in particular to a frequency division same divergence angle multi-mode OAM metasurface design. Background Art

[0002] OAM beam generation methods mainly include spiral phase plate method, rotating parabola method, computational holography method, uniform circular array method and surface wave modulation method based on metasurface. Among them, metasurface is a two-dimensional artificial electromagnetic structure that can realize the control of electromagnetic wave phase, amplitude, polarization and other characteristics, and is an effective electromagnetic control method. Due to its flexible control ability of electromagnetic waves, OAM beam generation methods based on metasurfaces have gradually become a research hotspot. Existing OAM metasurfaces are mainly divided into two types, passive OAM metasurfaces and active OAM metasurfaces.

[0003] The modulation characteristics of the metamaterial units in the passive OAM metasurface are adjusted by changing the physical length or rotation angle of the metal line. The electromagnetic waves radiated by the feed source are incident on the metamaterial units arranged on the OAM metasurface through free space. The metamaterial units with different amplitude and phase modulation characteristics are excited by the incident wave and radiate energy into space, thus generating OAM beams. The active OAM metasurface adjusts the amplitude and phase characteristics of the metasurface units by loading active devices, and is designed according to the phase modulation conditions of OAM to generate OAM beams.

[0004] Existing OAM metasurfaces have at least the following problems:

[0005] 1. The existing passive OAM metasurface composed of isotropic metasurface units can only modulate a single-mode OAM beam, which is not conducive to taking advantage of the infinite and orthogonal nature of the OAM beam mode;

[0006] 2. Existing active OAM metasurfaces can generate OAM beams of multiple modes, but OAM beams of different modes are generated at different times and the main lobe pointing of each mode OAM beam is different, which is not conducive to its application in the fields of communication and target detection.

[0007] 3. Existing active OAM metasurfaces require complicated control circuits, and each metamaterial unit has strong coupling, which easily causes the generated OAM beam to be distorted. Summary of the invention

[0008] To solve the above problems, the present invention provides a frequency-divided multi-mode OAM metasurface with the same divergence angle. The present invention realizes the radiation of OAM beams of multiple modes at multiple frequency points in a wide band, breaking the limitations of the current passive OAM metasurface and improving the overall performance of the metasurface; the invention can achieve the generation of at least six modes of OAM beams (i.e., ±1, ±2, ±3 modes), the frequency interval between each mode of OAM beam does not exceed 0.6 GHz, and the divergence angles of different mode OAM beams are the same.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A frequency-division, same-divergence-angle multi-mode OAM metasurface, comprising: an extremely narrow-band spatial filtering module and a multi-mode OAM modulation module;

[0011] The ultra-narrowband spatial filtering module is composed of multiple layers of frequency selective structural surfaces with narrowband characteristics, each layer of the frequency selective structural surface is composed of narrowband response structural units, which are used to select electromagnetic waves of specific spatial frequencies, and the incident wave excitation of the multi-mode OAM modulation module is realized by adjusting the spatial distribution of the narrowband response structural units of the frequency selective structural surface;

[0012] The multi-modal OAM modulation module is arranged on the surface of the extremely narrow-band spatial filtering module. The multi-modal OAM modulation module is composed of a phase structure surface unit, which is used to receive the zoned and frequency-divided electromagnetic wave excitation signal transmitted by the extremely narrow-band spatial filtering module, and modulate the electromagnetic waves incident on different areas into different mode OAM beams, and then make the OAM beams of different frequencies and modes radiate in a specific spatial area.

[0013] As a further improvement of the present invention, the extremely narrowband spatial filtering module includes a plurality of passband regions with different frequency ranges;

[0014] The operating frequencies of the multiple frequency ranges include no less than two frequency centers, and the frequency selection structure surface unit corresponding to each frequency center is obtained by cascading a unit with a low-pass characteristic and a unit with a band-stop characteristic, or a unit with a high-pass characteristic and a unit with a band-stop characteristic;

[0015] The multiple passband regions are used to convert incident waves operating in a wide frequency band or at multiple frequency points into zoned and frequency-divided electromagnetic waves, and the zoned and frequency-divided electromagnetic waves are used to excite corresponding regions of the multi-mode OAM modulation module.

[0016] As a further improvement of the present invention, the frequency selective structure surface unit comprises a plurality of dielectric layers, a first dielectric plate is arranged between two dielectric layers, and a first metal layer is arranged on each dielectric layer;

[0017] The first metal layer of the low-pass characteristic unit and the high-pass characteristic unit is a regular combination pattern with a through hole in the center; the first metal layer on the intermediate dielectric layer in the band-stop characteristic unit is a cross-shaped metal strip.

[0018] As a further improvement of the present invention, the phase structure surface unit includes a second dielectric plate, and the upper and lower surfaces of the second dielectric plate are both provided with a second metal layer; the second metal layer is a cross-shaped metal strip, and the ends of the cross-shaped metal strip are bent and extended to one side in the same order, and the upper and lower second metal layers are coupled by a metal column.

[0019] As a further improvement of the present invention, the multi-mode OAM modulation module is used to realize a perceptual spatial cross structure of a specific transmission / reflection phase of a phase structure surface unit;

[0020] The capacitive-inductive spatial cross structure unit changes the capacitive-inductive reactance characteristics of the unit by increasing the current length of the structure surface unit, and expands the phase control range of the capacitive-inductive spatial cross structure unit by increasing the physical length of the metal line through the perforated bending line.

[0021] As a further improvement of the present invention, the multi-mode OAM modulation module and the ultra-narrowband spatial filtering module both include a plurality of quasi-annular regions with different radii;

[0022] In the multiple quasi-annular regions of the multi-mode OAM modulation module, corresponding phase structure surface units are arranged according to the phase distribution of different mode OAMs, so as to modulate the divided-frequency electromagnetic waves generated by the extremely narrow-band spatial filtering module into divided-frequency multi-mode OAM beams;

[0023] The multiple quasi-annular regions of the extremely narrow-band spatial filtering module correspond to the multiple quasi-annular regions of the multi-mode OAM modulation module in position.

[0024] As a further improvement of the present invention, the phase structure surface units of the OAM phase distribution in the multi-modal OAM modulation module are placed in quasi-annular areas of different radii to adjust the main lobe direction of the OAM beam, the quasi-annular area with a smaller radius is set as a low modal area, and the quasi-annular area with a larger radius is set as a high modal area; the main lobe direction of the OAM beam of each mode tends to be consistent.

[0025] As a further improvement of the present invention, the frequency-division multi-mode OAM metasurface with the same divergence angle is a spatially centrally symmetrical structure, and the corresponding frequency points correspond to OAM modal beams with opposite phase rotations, and the mode number becomes an opposite number.

[0026] As a further improvement of the present invention, there is a gap filled with air or medium between the ultra-narrowband spatial filtering module and the multi-modal OAM modulation module, and the gap is 0.5 mm±0.2 mm.

[0027] As a further improvement of the present invention, when the frequency-division multi-mode OAM metasurface with the same divergence angle adopts a horn antenna working in the Ku band as a feed source, the metasurface can convert the incident wave into ±1 mode, ±2 mode and ±3 mode OAM beams respectively, the operating frequencies of the three modal OAM beams of -1 mode, -2 mode and -3 mode are 13.6 GHz, 13.0 GHz and 12.5 GHz respectively, and the divergence angle of the six modal OAM beams is 15°.

[0028] Compared with the prior art, the present invention has the following technical effects:

[0029] The present invention is a frequency-divided multi-mode OAM metasurface with the same divergence angle, including an extremely narrowband spatial filtering module and a multi-mode OAM modulation module. The extremely narrowband spatial filtering module includes three quasi-annular regions with different radii, which realize the electromagnetic wave radiation of discrete frequencies in local areas under broadband conditions, and transmit the electromagnetic waves with divided and divided frequencies to the multi-mode OAM modulation module. The multi-mode OAM modulation module also includes three quasi-annular regions with different radii, which are respectively arranged with phase structure surface units for modulating different mode OAM beams, so as to realize the generation of frequency-divided multi-mode OAM beams. In the multi-mode OAM modulation module, the quasi-annular regions with smaller radii are arranged with phase structure surface units for modulating low-mode OAM, and the quasi-annular regions with larger radii are arranged with phase structure surface units for modulating high-mode OAM, so as to realize that different mode OAM beams have the same main lobe pointing. The joint design of the extremely narrowband spatial filtering module and the multi-mode OAM modulation module realizes the simultaneous generation of OAM beams with different frequencies corresponding to different modes and having the same divergence angle. When a broadband electromagnetic wave is incident on the invention, multiple modes of OAM beams can be generated simultaneously, and the operating frequencies of each mode of OAM beam are discrete frequency points and the main lobe points in the same direction. By adjusting the relative placement of the multi-mode OAM modulation module and the ultra-narrowband spatial filtering module, the invention can convert electromagnetic waves at the same frequency points into OAM beams with the same divergence angle and opposite modal numbers. In summary, the present invention can generate multiple modes of OAM beams, and the divergence angles of each mode of OAM beam are the same. The device of the present invention can use a broadband horn antenna as a feed source under the condition that the antenna structure is fixed to achieve the generation of OAM beams with different frequencies, different modes and the same divergence angle, thereby simplifying the system complexity and reducing the design cost.

[0030] Furthermore, the present invention can realize the design of frequency-divided multi-mode OAM metasurface with the same divergence angle. When a horn antenna used in the Ku band is used as a feed source, the metasurface can convert the incident wave into ±1 mode, ±2 mode and ±3 mode OAM beams respectively, and the main lobe pointing directions of the six modes of OAM beams are approximately the same, about 15°. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure of an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the structure of a frequency selective structure surface unit in an embodiment of the present invention;

[0033] Figure 3 Schematic diagram of the structure of the OAM phase structure surface unit in an embodiment of the present invention;

[0034] Figure 4 are three annular-like areas with different radii in the embodiment of the present invention;

[0035] Figure 5 The amplitude and phase characteristics of the OAM phase structure surface unit in the embodiment of the present invention (the operating frequencies are 12.5 GHz, 13.0 GHz and 13.6 GHz respectively);

[0036] Figure 6 is the amplitude and phase characteristics of the frequency selective structure surface unit in the embodiment of the present invention;

[0037] Figure 7 The electric field distribution of the OAM beam generated by the embodiment of the present invention;

[0038] Figure 8 This is the far-field pattern of the OAM beam generated by the embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following is a clear and complete description of the technical solution of the present invention in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the protection scope of the present invention.

[0040] like Figure 1 As shown, the frequency-division same-divergence-angle multi-mode OAM metasurface provided by the present invention includes an extremely narrow-band spatial filtering module 10 and a multi-mode OAM beam modulation module 20;

[0041] The ultra-narrowband spatial filtering module 10 is composed of multiple layers of frequency selective structural surfaces with narrowband characteristics, each layer of the frequency selective structural surface is composed of narrowband response structural units, which are used to select electromagnetic waves of specific spatial frequencies, and the incident wave excitation of the multi-mode OAM modulation module 20 is realized by adjusting the spatial distribution of the frequency selective structural surface units;

[0042] The multi-mode OAM modulation module 20 is used to receive the zoned frequency-divided electromagnetic wave excitation signal transmitted by the extremely narrow-band spatial filtering module 10, and modulate the electromagnetic waves incident on different areas of the module into OAM beams of different modes, and then radiate OAM beams of different frequencies and modes in a specific spatial area;

[0043] Specifically, the ultra-narrowband spatial filtering module is composed of a variety of frequency selective structural surface units. Different frequency selective structural surface units are arranged in quasi-annular areas with different radii in the module to achieve the radiation of electromagnetic waves of specific frequencies in different areas. The ultra-narrowband spatial filtering module is used to perform spatial filtering on the electromagnetic waves radiated by the feed source, realize electromagnetic wave excitation corresponding to multiple frequencies in multiple areas under wide-band conditions, and transmit the energy of the electromagnetic waves to the multi-mode OAM modulation module.

[0044] Some frequency selective structure surface units constituting the extremely narrowband spatial filtering module are obtained by cascading a frequency selective structure surface unit with a low-pass characteristic and a frequency selective structure surface unit with a band-stop characteristic, or a frequency selective structure surface unit with a high-pass characteristic and a frequency selective structure surface unit with a band-stop characteristic, so as to achieve a narrower passband width.

[0045] The multi-mode OAM modulation module is used to receive the zoned frequency-divided electromagnetic waves transmitted by the extremely narrow-band spatial filtering module, and perform OAM modulation on the electromagnetic waves in the corresponding area according to the phase distribution law of OAM, to generate OAM beams of different modes and radiate them into space.

[0046] The ultra-narrowband spatial filtering module 10 includes a plurality of passband regions with different frequency ranges.

[0047] The extremely narrowband spatial filtering module 10 is composed of Figure 2 The frequency selective structure surface unit shown is composed of, Figure 2 The frequency structure surface unit shown in (b) is Figure 2 The frequency structure surface unit shown in (a) is composed of a cascade connection of a frequency structure surface unit with a band-stop characteristic to achieve narrowband characteristics.

[0048] The ultra-narrowband spatial filtering module 10 comprises Figure 4 The three quasi-annular regions (called l-mode regions) shown in the figure realize the regional and frequency-divided local filtering characteristics. Electromagnetic waves working under wide-band conditions are incident on the ultra-narrow-band spatial filtering module 10, and each region only allows electromagnetic waves working at a specified frequency to be transmitted.

[0049] The multi-mode OAM modulation module 20 and the ultra-narrowband spatial filtering module 10 both include a plurality of quasi-annular regions with different radii.

[0050] Preferably, the multi-mode OAM modulation module comprises a plurality of quasi-annular regions with different radii (respectively referred to as l-modal regions, l = ..., -1, 0, 1, 2, ...); the plurality of quasi-annular regions are respectively arranged with phase structure surface units for modulating different modal OAM beams to realize the multi-mode OAM modulation function of the multi-mode OAM modulation module.

[0051] The operating frequencies of the multiple frequency ranges include no less than 2 frequency centers, and the frequency selection structure surface unit corresponding to each frequency center is obtained by cascading a unit with low-pass characteristics and a unit with band-stop characteristics, or a unit with high-pass characteristics and a unit with band-stop characteristics.

[0052] The multiple passband regions are used to convert incident waves operating in a wide frequency band or at multiple frequency points into zoned and frequency-separated electromagnetic waves, and the zoned and frequency-separated electromagnetic waves are used to excite corresponding regions of the multi-mode OAM modulation module 20 .

[0053] The design of specific transmission / reflection phase of the phase structure surface unit in the multi-mode OAM modulation module 20 is realized based on the capacitive spatial cross structure.

[0054] The annular region with a smaller radius is set as a low-mode region, and the phase structure surface units for modulating the low-mode OAM beam are arranged; the annular region with a larger radius is set as a high-mode region, and the phase structure surface units for modulating the high-mode OAM beam are arranged. The above arrangement method is used to achieve the divergence angles of the generated OAM beams of different modes to be approximately consistent.

[0055] The ultra-narrowband spatial filtering module 10 is used to modulate the incident electromagnetic wave working under broadband conditions into a zoned frequency-divided electromagnetic wave, and transmit the zoned frequency-divided electromagnetic wave to the multi-modal OAM beam modulation module 20 to ensure that the electromagnetic wave of the specified frequency is incident on the specified area of ​​the multi-modal OAM beam modulation module 20 and generates an OAM beam of the specified frequency and specified mode.

[0056] The multi-mode OAM beam modulation module 20 is composed of Figure 3 The phase structure surface unit shown is composed of Figure 3 The phase structure surface unit shown in (a) cannot achieve the 360° phase shift required to generate OAM, so the physical length of the metal line is increased by bending the line to increase the characteristic control range of the phase structure surface unit, such as Figure 3 As shown in (b).

[0057] The multi-mode OAM beam modulation module 20 is the same as the ultra-narrowband spatial filtering module 10, including: Figure 1 In the three modal regions shown, phase structure surface units for modulating different modal OAM beams are placed in different modal regions to achieve multi-modal OAM modulation capability with the same divergence angle.

[0058] The capacitive-inductive spatial cross structure unit changes the capacitive-inductive reactance characteristics of the unit by increasing the current length of the structure surface unit, and expands the phase control range of the capacitive-inductive spatial cross structure unit by increasing the physical length of the metal line through the perforated bending line.

[0059] In the multiple quasi-annular regions of the multi-mode OAM modulation module 20, corresponding phase structure surface units are arranged according to the phase distribution of different mode OAMs, and the partitioned frequency-divided electromagnetic waves generated by the ultra-narrowband spatial filtering module 10 are modulated into frequency-divided multi-mode OAM beams. The main lobe directions of the OAM beams of each mode obtained by modulation by the multi-mode OAM modulation module 20 tend to be consistent.

[0060] The multiple quasi-annular regions of the extremely narrowband spatial filtering module correspond to the multiple quasi-annular regions of the multi-modal OAM modulation module, and the positions corresponding to the low-modal regions in the extremely narrowband spatial filtering module are arranged with frequency selective structural surface units with higher central frequencies, while the positions corresponding to the high-modal regions are arranged with frequency selective structural surface units with lower central frequencies, so as to achieve fine-tuning of the main lobe pointing of different modes by reasonably setting the working frequencies of the OAM beams of different modes, thereby ensuring that the divergence angles of the OAM beams of different modes are the same.

[0061] The main lobe direction of the OAM beam is adjusted by placing the phase structure surface units that meet the OAM phase distribution in quasi-annular areas of different radii. The quasi-annular area with a smaller radius is set as the low-mode area, and the quasi-annular area with a larger radius is set as the high-mode area, so as to achieve the same divergence angle effect of different mode OAM beams.

[0062] The frequency-division multi-mode OAM metasurface with the same divergence angle can simultaneously generate multi-mode OAM beams (where the operating frequencies of the multi-mode OAM beams are respectively concentrated at corresponding frequency points). By adjusting the placement state of the multi-mode OAM modulation module, the divergence angles of the multi-mode OAM beams generated by the metasurface are the same.

[0063] The frequency-division multi-mode OAM metasurface with the same divergence angle is a spatially centrosymmetric structure. Through spatial mirror-symmetric rotation, an OAM modal beam with a corresponding reverse phase rotation can be obtained at the corresponding frequency point, that is, the mode number becomes the opposite number.

[0064] In the design, there is a gap filled with air or dielectric between the ultra-narrowband spatial filtering module 10 and the multi-mode OAM modulation module 20. When the gap changes within 0.5 mm±0.2 mm, the operating characteristics of the entire device remain substantially unchanged.

[0065] The present invention can realize a multi-mode OAM metasurface with frequency division and the same divergence angle, and can convert electromagnetic waves working in a wide band into OAM beams of multiple modes with different working frequencies, and the divergence angles of each mode are consistent. By arranging the phase structure surface units in different regions, the design of modulating multiple modes of OAM at multiple frequency points under broadband conditions is realized, the design of the multi-mode OAM metasurface is simplified, the overall performance of the metasurface is improved, and the design cost is reduced; the invention is used in a target detection system and can provide multiple independent detection modes, which is conducive to improving detection accuracy and detection efficiency.

[0066] The present invention is described in detail below with reference to the accompanying drawings and embodiments:

[0067] Example

[0068] A frequency-division same-divergence-angle multi-mode OAM metasurface, comprising: an extremely narrow-band spatial filtering module 10 and a multi-mode OAM beam modulation module 20;

[0069] The ultra-narrowband spatial filtering module 10 is used to pre-process the broadband electromagnetic waves radiated by the feed source. Figure 2 The frequency selective structure surface units shown are arranged in partitions to convert the incident electromagnetic waves into partitioned frequency-frequency electromagnetic waves and transmit them to the multi-mode OAM beam modulation module 20 .

[0070] Specifically, structurally, the frequency selective structure surface unit includes a plurality of dielectric layers, a first dielectric plate is disposed between two dielectric layers, and a first metal layer is disposed on each dielectric layer;

[0071] The first metal layer of the low-pass characteristic unit and the high-pass characteristic unit is a regular combination pattern with a through hole in the center; the first metal layer on the intermediate dielectric layer in the band-stop characteristic unit is a cross-shaped metal strip.

[0072] The extremely narrowband spatial filtering module 10 has the following features: Figure 4 The three annular regions with different radii shown in the figure only allow electromagnetic waves of 13.6 GHz, 13.0 GHz and 12.5 GHz to be transmitted from the inner to the outer regions, respectively, so as to realize the transformation of broadband electromagnetic waves into zoned frequency-divided electromagnetic waves. The zoned frequency-divided electromagnetic waves are used to excite the multi-mode OAM beam modulation module 20.

[0073] The multi-mode OAM beam modulation module 20 is composed of Figure 3 The phase structure surface unit shown is used to modulate the divided and frequency-divided electromagnetic waves converted by the extremely narrow-band spatial filtering module 10 into divided and frequency-divided multi-mode OAM beams with the same divergence angle and radiate them into space.

[0074] Specifically, the phase structure surface unit includes a second dielectric plate, and the upper and lower surfaces of the second dielectric plate are both provided with a second metal layer; the second metal layer is a cross-shaped metal strip, and the ends of the cross-shaped metal strip are bent and extended to one side in the same order, and the upper and lower second metal layers are coupled by a metal column.

[0075] The multi-mode OAM beam modulation module 20 includes three quasi-annular regions with different radii, and the layout and design of the quasi-annular regions are consistent with the ultra-narrowband spatial filtering module 10. From the inside to the outside, the phase structure surface units for generating 1-mode, 2-mode and 3-mode OAM beams are arranged in each quasi-annular region respectively; the upper and lower bottom surfaces of the multi-mode OAM beam modulation module 20 are adjusted, and the phase arrangement of each type of annular region satisfies the phase distribution of -1 mode, -2 mode and -3 mode respectively. At this time, the multi-mode OAM beam modulation module 20 can modulate the partitioned frequency-divided electromagnetic waves into -1 mode, -2 mode and -3 mode OAM beams (the operating frequencies of the three mode OAM beams are 13.6GHz, 13.0GHz and 12.5GHz respectively).

[0076] like Figure 7 , Figure 8 As shown, the embodiment of the present invention can convert electromagnetic waves operating at 13.6 GHz, 13.0 GHz and 12.5 GHz into OAM beams of ±1 mode, ±2 mode and ±3 mode respectively, and the divergence angles of the OAM beams of the six modes tend to be consistent, which is about 15°.

[0077] In summary, the frequency-divided multi-modal OAM metasurface with the same divergence angle of the present invention includes an extremely narrowband spatial filtering module 10 and a multi-modal OAM beam modulation module 20. The extremely narrowband spatial filtering module 10 includes three quasi-annular areas with different radii and three different frequency-selective structural surface units are arranged respectively, so as to realize the conversion of broadband electromagnetic waves into partitioned frequency-frequency electromagnetic waves. The multi-modal OAM beam modulation module is the same as the extremely narrowband spatial filtering module, including three quasi-annular areas with different radii, and phase structure surface units satisfying different modal OAM phase distributions are arranged in each area, which is used to convert the frequency-divided and partitioned electromagnetic waves into three modes of OAM beams with main lobes pointing to the same working frequency but different modes, and three other modes of OAM beams can be obtained by adjusting the upper and lower bottom surfaces of the multi-modal OAM beam modulation module.

[0078] The present invention can realize the design of a frequency-division multi-mode OAM metasurface with the same divergence angle. When a horn antenna working in the Ku band is used as a feed source, the metasurface can convert the incident wave into ±1 mode, ±2 mode and ±3 mode OAM beams respectively, and the divergence angles of the six modes of OAM beams are approximately the same, about 15°.

[0079] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A frequency-division, same-divergence-angle multi-mode OAM metasurface, characterized in that: include: An extremely narrowband spatial filtering module (10) and a multi-mode OAM modulation module (20); The extremely narrowband spatial filtering module (10) is composed of multiple layers of frequency selective structural surfaces with narrowband characteristics, each layer of the frequency selective structural surface is composed of narrowband response structural units, and is used to select electromagnetic waves of a specific spatial frequency. By adjusting the spatial distribution of the narrowband response structural units of the frequency selective structural surface, the incident wave excites the multi-mode OAM modulation module (20) in a zoned and frequency-determined manner; The multi-mode OAM modulation module (20) is arranged above the surface of the extremely narrow-band spatial filtering module (10), and is composed of a phase structure surface unit, and is used to receive the zoned and frequency-divided electromagnetic wave excitation signal transmitted by the extremely narrow-band spatial filtering module (10), and modulate the electromagnetic waves incident on different areas into OAM beams of different modes, and then radiate the OAM beams of different frequencies and modes in a specific spatial area; A perceptual spatial cross structure unit in the multi-mode OAM modulation module (20) for realizing a specific transmission / reflection phase of a phase structure surface unit; The extremely narrowband spatial filtering module (10) comprises a plurality of passband regions with different frequency ranges; The operating frequencies of the multiple frequency ranges include no less than two frequency centers, and the frequency selection structure surface unit corresponding to each frequency center is obtained by cascading a unit with a low-pass characteristic and a unit with a band-stop characteristic, or a unit with a high-pass characteristic and a unit with a band-stop characteristic; The frequency selection structure surface unit comprises a plurality of dielectric layers, a first dielectric plate is arranged between two dielectric layers, and a first metal layer is arranged on each dielectric layer; The first metal layer of the low-pass characteristic unit and the high-pass characteristic unit is a regular combination pattern with a through hole in the center; the first metal layer on the intermediate dielectric layer in the band-stop characteristic unit is a cross-shaped metal strip; The phase structure surface unit includes a second dielectric plate, and the upper and lower surfaces of the second dielectric plate are both provided with a second metal layer; the second metal layer is a cross-shaped metal strip, and the ends of the cross-shaped metal strip are bent and extended to one side in the same order, and the upper and lower second metal layers are coupled by a metal column.

2. The frequency-division same-divergence-angle multi-mode OAM metasurface according to claim 1, characterized in that: The multiple passband regions are used to convert incident waves operating in a wide frequency band or at multiple frequency points into zoned frequency-separated electromagnetic waves, and the zoned frequency-separated electromagnetic waves are used to excite corresponding regions of the multi-mode OAM modulation module (20).

3. The frequency-division same-divergence-angle multi-mode OAM metasurface according to claim 1, characterized in that: The capacitive-inductive spatial cross structure unit changes the capacitive-inductive reactance characteristics of the unit by increasing the current length of the structure surface unit, and expands the phase control range of the capacitive-inductive spatial cross structure unit by increasing the physical length of the metal line through the perforated bending line.

4. The frequency-division same-divergence-angle multi-mode OAM metasurface according to claim 1, characterized in that: The multi-mode OAM modulation module (20) and the ultra-narrowband spatial filtering module (10) both include a plurality of quasi-annular regions with different radii; In a plurality of quasi-annular regions of the multi-mode OAM modulation module (20), corresponding phase structure surface units are arranged according to the phase distribution of different mode OAMs, so as to modulate the divided-frequency electromagnetic waves generated by the extremely narrow-band spatial filtering module (10) into divided-frequency multi-mode OAM beams; The multiple quasi-annular regions of the extremely narrow-band spatial filtering module (10) correspond in position to the multiple quasi-annular regions of the multi-mode OAM modulation module (20).

5. The frequency-division same-divergence-angle multi-mode OAM metasurface according to claim 4, characterized in that: The phase structure surface units of the OAM phase distribution in the multi-mode OAM modulation module (20) are placed in quasi-annular areas of different radii to adjust the main lobe direction of the OAM beam, the quasi-annular area with a smaller radius is set as a low-mode area, and the quasi-annular area with a larger radius is set as a high-mode area; the main lobe directions of the OAM beams of each mode tend to be consistent.

6. The frequency-division same-divergence-angle multi-mode OAM metasurface according to claim 1, characterized in that: The frequency-division same-divergence-angle multi-mode OAM metasurface is a spatially centrally symmetrical structure, and corresponding frequency points correspond to OAM modal beams with opposite phase rotations, and the modal numbers become opposite numbers.

7. The frequency-division same-divergence-angle multi-mode OAM metasurface according to claim 1, characterized in that: There is a gap filled with air or a medium between the extremely narrowband spatial filtering module (10) and the multi-mode OAM modulation module (20), and the gap is .

8. The frequency-division same-divergence-angle multi-mode OAM metasurface according to claim 1, characterized in that: When the frequency-division multi-mode OAM metasurface uses a horn antenna working in the Ku band as a feed source, the metasurface can convert the incident wave into modal, Modal and The operating frequencies of the three modal OAM beams, -1 mode, -2 mode and -3 mode, are 13.6 GHz, 13.0 GHz and 12.5 GHz respectively, and the divergence angles of the six modal OAM beams are all 15°.

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