Broadband multi-mode orbital angular momentum array antenna and design method thereof

Abstract

The application discloses a broadband multi-mode orbital angular momentum array antenna and a design method thereof, and comprises the following steps: S1, determining the number of orbital angular momentum modes and the central frequency of target modulated electromagnetic waves according to application scene requirements; S2, designing a tightly-coupled array antenna array unit; S3, determining the number of tightly-coupled array antenna units according to the number of orbital angular momentum modes, adopting a circular array form to obtain a tightly-coupled array antenna; S4, designing an array antenna feed balun according to the wavelength of the central frequency; S5, designing a feed network according to the number of tightly-coupled array antenna units; and S6, assembling the tightly-coupled array antenna, the array antenna feed balun and the feed network to obtain an orbital angular momentum array antenna. The application can realize electromagnetic radiation of multi-mode orbital angular momentum in a super wideband frequency band.

Description

Technical Field

[0001] This invention relates to the field of orbital angular momentum array antenna design technology, specifically to a broadband multi-mode orbital angular momentum array antenna and its design method. Background Technology

[0002] As wireless communication technology has evolved, the importance of electromagnetic wave channel capacity research has been continuously increasing. Traditional analog signal modulation, including amplitude modulation, phase modulation, and frequency modulation, has limited channel capacity. To improve the stability and clarity of wireless information transmission, new information loading methods are urgently needed to enhance channel capacity. As one of the characteristics of electromagnetic waves, orbital angular momentum theoretically possesses multiple pairs of orthogonal modes. Therefore, by loading information modulation onto the orbital angular momentum mode number of electromagnetic waves, the channel capacity in wireless communication can be greatly improved.

[0003] Existing research reports that orbital angular momentum (EOGM) antenna arrays can radiate EOGM electromagnetic waves or generate them by modulating incident plane waves. Specifically, this involves modulating EOGM carrying a specific number of modes by irradiating transmissive metasurfaces, reflective metasurfaces, and spiral phase plates with plane electromagnetic waves generated by a feed. These devices offer the advantage of wide bandwidth; however, the number of EOGM modes generated by a single device is fixed. To modulate multimode EOGM, additional RF switches such as PIN diodes are required. EOGM antenna arrays are primarily circular antenna arrays, generating different numbers of EOGM modes by changing the phase of the signals fed into the antenna elements. However, the number of EOGM modes generated by circular array antennas is closely related to the number of antenna elements. As the number of modes increases, the array size increases dramatically, and the operating bandwidth becomes narrower.

[0004] In summary, the narrow bandwidth and limited number of modes of traditional orbital angular momentum array antennas are problems that urgently need to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a broadband multi-mode orbital angular momentum array antenna and its design method, so as to solve the problems of narrow bandwidth and small number of modes of existing orbital angular momentum array antennas, so as to realize electromagnetic radiation of multi-mode orbital angular momentum in ultra-wideband frequency bands.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0007] This invention provides a broadband multi-mode orbital angular momentum array antenna, the broadband multi-mode orbital angular momentum array antenna comprising:

[0008] Multiple tightly coupled array antenna elements are arranged sequentially such that the broadband multi-mode orbital angular momentum array antenna is formed as a hollow columnar structure, and the spacing between each tightly coupled array antenna element is less than 0.1 wavelength.

[0009] Alternatively, each of the tightly coupled array antenna elements may be configured in a fan shape to form the broadband multi-mode orbital angular momentum array antenna as a hollow cylindrical structure.

[0010] Optionally, each of the tightly coupled array antenna elements is provided with a first dielectric layer, a dipole, a second dielectric layer, a coupling patch, a feed balun, and a ground plane in sequence from top to bottom. The coupling patch is located below the arm of the dipole. The dipole is symmetrically arranged about the central axis of the sector and a parasitic unit is provided on each side of the dipole. The two ends of the top of the feed balun are respectively attached to the coupling patch, one end of its bottom is connected to the input, and the other end is connected to the ground plane. A feed network is provided on the bottom surface of the ground plane.

[0011] Alternatively, the top surface of the first dielectric layer may also be provided with a grid-structured metasurface, which is constructed as a plurality of spaced trapezoidal metal patches.

[0012] Alternatively, each of the tightly coupled array antenna elements may also be provided with a grid structure metasurface on its outer side. The top of the grid structure metasurface is connected to the grid structure metasurface, and the bottom is fixed to the outer side of the ground plane. The grid structure metasurface is constructed as a rectangular metal patch arranged in an array.

[0013] Alternatively, the feeding balun includes a front side, a back side, and a dielectric plate located between the front side and the back side. The dielectric plate is constructed as a cuboid plate. The front side is provided with microstrip line patches of decreasing length, which extend along the height direction of the cuboid plate and are located on the center line of the width of the cuboid plate. The back side is provided with a triangular floor, the vertex of which is connected to the top of the microstrip line patches of decreasing length, and the length of the base of the triangle is equal to the width of the feeding balun.

[0014] Alternatively, the material of the dielectric substrate is RO4350B.

[0015] The present invention also provides a design method for a broadband multi-mode orbital angular momentum array antenna based on the above, the design method comprising:

[0016] S1: Determine the number of orbital angular momentum modes and the center frequency of the electromagnetic wave modulated by the target, based on the application scenario requirements.

[0017] S2: Design a tightly coupled array antenna array element;

[0018] S3: Determine the number of tightly coupled array antenna elements based on the orbital angular momentum mode number, and obtain a tightly coupled array antenna by adopting a circular array form;

[0019] S4: Design the array antenna feed balun based on the wavelength of the center frequency;

[0020] S5: Design the feeding network based on the number of tightly coupled array antenna elements;

[0021] S6: Assemble the tightly coupled array antenna, the array antenna feed balun, and the feed network to obtain the orbital angular momentum array antenna.

[0022] Alternatively, S3 includes:

[0023] S31: Based on the center frequency, use the equivalent impedance characteristic formula to calculate the grating structure metasurface located on the top layer of the antenna and the grid structure metasurface located on the outer layer of the antenna.

[0024] S32: Assemble the grating structure metasurface and the grid structure metasurface onto each of the tightly coupled array antenna elements to obtain multiple assembled tightly coupled array antenna elements;

[0025] S33: Determine the number of tightly coupled array antenna elements based on the orbital angular momentum mode number;

[0026] S34: Based on the number of array antenna elements, the assembled tightly coupled array antenna elements are assembled in a circular array form to obtain a tightly coupled array antenna.

[0027] Alternatively, in step S31, the grating structure metasurface X(f) located at the top layer of the antenna is calculated based on the center frequency using the equivalent impedance characteristic formula. top for:

[0028]

[0029] Where n1 and n2 represent the refractive indices of the capping layer and air, respectively, g represents the bandgap period width, which is the sum of the widths of the metal sheet and the bandgap, f is the center frequency, c is the speed of light in vacuum, ln() represents the logarithmic function, csc() represents the cosecant function, π represents pi, and a is the width of the metal sheet.

[0030] In step S31, the metasurface X(f) of the lattice structure located on the outer layer of the antenna is calculated based on the center frequency and using the equivalent impedance characteristic formula. side for:

[0031]

[0032] Where w'0 represents the substitution parameter and w0 represents the angular frequency of light, n1 and n2 represent the refractive indices of the cladding layer and air, respectively, ln() represents the logarithmic function, csc() represents the cosecant function, π represents pi, a is the width of the metal sheet, g represents the band gap period width, i.e., the sum of the widths of the metal sheet and the band gap, f is the center frequency, and c is the speed of light in vacuum.

[0033] Determining the number of tightly coupled array antenna elements based on the orbital angular momentum mode number includes:

[0034] φ n -φ n-1 =2πlN

[0035] Where N represents the number of tightly coupled array antenna elements, π represents pi, l represents the number of orbital angular momentum modes, and φ n This represents the phase of the input signal of the nth tightly coupled array antenna element and... Indicates the reference phase, φ n-1 This represents the phase of the input signal for the (n-1)th tightly coupled array antenna element.

[0036] The present invention has the following beneficial effects:

[0037] 1. Tightly coupled antenna arrays can radiate electromagnetic waves in the ultra-wideband frequency band due to their unique tight coupling effect. Therefore, this invention applies the tightly coupled array antenna to the orbital angular momentum array antenna, which can realize a broadband multi-mode orbital angular momentum array antenna.

[0038] 2. Tightly coupled antenna arrays can generate electromagnetic waves with different orbital angular momentum modes by inputting electrical signals of different modes and phases. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of the broadband multi-mode orbital angular momentum array antenna of the present invention;

[0040] Figure 2 This is a schematic diagram of the tightly coupled array antenna unit structure of the present invention;

[0041] Figure 3 This is a schematic diagram of the tightly coupled array antenna unit structure after assembly according to the present invention;

[0042] Figure 4 This is a schematic diagram of the structure of the feeding balun;

[0043] Figure 5 This is a flowchart illustrating the design method of the broadband multi-mode orbital angular momentum array antenna of the present invention;

[0044] Figure 6 Comparison of simulation results of the assembled tightly coupled array antenna unit;

[0045] Figure 7 This is a schematic diagram of the simulation results for a fed balun. Detailed Implementation

[0046] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0047] This invention provides a broadband multi-mode orbital angular momentum array antenna, reference Figure 1 As shown, the broadband multi-mode orbital angular momentum array antenna includes:

[0048] Multiple tightly coupled array antenna elements are arranged sequentially such that the broadband multi-mode orbital angular momentum array antenna is formed as a hollow columnar structure, and the spacing between each tightly coupled array antenna element is less than 0.1 wavelength.

[0049] Optionally, refer to Figure 2 As shown, each of the tightly coupled array antenna elements is constructed in a fan shape, so that the broadband multi-mode orbital angular momentum array antenna is formed into a hollow cylindrical structure.

[0050] Optionally, refer to Figure 2 As shown, each of the tightly coupled array antenna elements is arranged from top to bottom as follows: a first dielectric layer, a dipole, a second dielectric layer, a coupling patch, a feed balun, and a ground plane. The coupling patch is located below the arm of the dipole. The dipole is symmetrically arranged about the central axis of the sector, and a parasitic unit is arranged on each side of the dipole. The feed balun is used to reduce impedance, and its top two ends are respectively attached to the coupling patch. One end of its bottom is connected to the input, and the other end is connected to the ground plane. A feed network is arranged on the bottom surface of the ground plane.

[0051] Optionally, refer to Figure 3 As shown, the top surface of the first dielectric layer is also provided with a grid-structured metasurface, which is constructed as a plurality of spaced trapezoidal metal patches.

[0052] Alternatively, each of the tightly coupled array antenna elements may also be provided with a grid structure metasurface on its outer side. The top of the grid structure metasurface is connected to the grid structure metasurface, and the bottom is fixed to the outer side of the ground plane. The grid structure metasurface is constructed as a rectangular metal patch arranged in an array.

[0053] Optionally, refer to Figure 4As shown, the feeding balun includes a front side, a back side, and a dielectric plate located between the front side and the back side. The dielectric plate is constructed as a cuboid plate. The front side is provided with microstrip line patches of decreasing length, which extend along the height direction of the cuboid plate and are located on the center line of the width of the cuboid plate. The back side is provided with a triangular floor, the vertex of which is connected to the top of the microstrip line patches of decreasing length, and the length of the base of the triangle is equal to the width of the feeding balun.

[0054] To increase bandwidth, the dielectric substrate may optionally be made of RO4350B material.

[0055] Based on the above technical solution, the present invention also provides a design method for a broadband multi-mode orbital angular momentum array antenna, referring to... Figure 5 As shown, the design method of the broadband multi-mode orbital angular momentum array antenna includes:

[0056] S1: Determine the number of orbital angular momentum modes and the center frequency of the electromagnetic wave modulated by the target, based on the application scenario requirements.

[0057] In one specific implementation, the present invention is designed with a tightly coupled antenna array with a center frequency of 5.6 GHz.

[0058] First, based on the application scenario requirements, the number of orbital angular momentum modes is determined to be 11, including mode 0, mode ±1, mode ±2, mode ±3, mode ±4, and mode ±5, and the center frequency of the target modulated electromagnetic wave is 5.6 GHz.

[0059] S2: Design a tightly coupled array antenna array element;

[0060] Specifically, this includes designing the dipole antenna arm length and width, height distance from the ground, coupling structure, and loading medium height based on the center frequency, and implementing this through periodic boundary simulation. Generally, the antenna length and height are less than half the wavelength of the operating frequency.

[0061] The array unit consists of a dipole, parasitic elements, coupling patches, a ground plane, and a dielectric. The antenna unit has an outer diameter of 50 mm, an inner diameter of 30 mm, and a bending angle of 30 degrees. The dipole arm is 10.5 mm long and 3.45 mm wide. The parasitic elements are located on both sides of the dipole, with a length of 10 mm, a width of 0.5 mm, and a distance of 4.1 mm from the dipole. The coupling patches are located below the dipole arm edges, with a length of 2.8 mm, a width of 3.45 mm, and are connected to the dipole via a dielectric substrate. They are located below the dipole antenna and have a height of 0.762 mm. The dipole is covered with a dielectric material of Ro4350B, with a dielectric constant of 3.66 and a height of 9.762 mm. The height between the dipole and the ground plane is 15 mm. To achieve a circular array, the antenna parameters were optimized through scanning simulation. The final unit is as follows. Figure 2 As shown.

[0062] S3: Determine the number of tightly coupled array antenna elements based on the orbital angular momentum mode number, and obtain a tightly coupled array antenna by adopting a circular array form;

[0063] S3 includes:

[0064] S31: Based on the center frequency, use the equivalent impedance characteristic formula to calculate the grating structure metasurface located on the top layer of the antenna and the grid structure metasurface located on the outer layer of the antenna.

[0065] In step S31, the metasurface X(f) of the grating structure located at the top layer of the antenna is calculated based on the center frequency and using the equivalent impedance characteristic formula. top for:

[0066]

[0067] Where n1 and n2 represent the refractive indices of the cladding layer and air, respectively, g represents the bandgap period width, which is the sum of the widths of the metal sheet and the bandgap, f is the center frequency, c is the speed of light in vacuum, ln() represents the logarithmic function, csc() represents the cosecant function, π represents pi, and a is the width of the metal sheet.

[0068] By adding the impedance of the metasurface with a gate structure to the equivalent circuit analysis to calculate a suitable width, the height of the cladding layer can be effectively reduced, the profile height of the overall antenna array can be lowered, and the bandwidth can be broadened and the angle scanning performance optimized.

[0069] Based on the center frequency, the equivalent impedance characteristic formula is used to calculate the lattice structure metasurface X(f) located on the outer layer of the antenna. side for:

[0070]

[0071] Where w'0 represents the substitution parameter and w0 represents the angular frequency of light, n1 and n2 represent the refractive indices of the cladding layer and air, respectively, ln() represents the logarithmic function, csc() represents the cosecant function, π represents pi, a is the width of the metal sheet, g represents the band gap period width, i.e., the sum of the widths of the metal sheet and the band gap, f is the center frequency, and c is the speed of light in vacuum.

[0072] The lattice-structured metasurface has the properties of a spatial filter with capacitance, inductance, and ground in parallel. By observing the S-parameter performance in HFSS simulation and optimizing the size of the metal plate, the array antenna can achieve bandwidth optimization.

[0073] S32: Assemble the grating structure metasurface and the grid structure metasurface onto each of the tightly coupled array antenna elements to obtain multiple assembled tightly coupled array antenna elements;

[0074] A schematic diagram of the assembled tightly coupled antenna unit is shown below. Figure 3 As shown, this includes a metasurface with a grid structure and a metasurface with a lattice structure. The metasurface with a grid structure is a trapezoidal metal structure with a bandgap width of 2.4 degrees, while the metasurface with a lattice structure is a matrix of metal patches with bandgap widths of 0.18 mm and 0.4 mm, respectively. Figure 6 As can be seen, the lattice structure metasurface increases the bandwidth of the antenna array from 95% to 107%, while the lattice structure metasurface reduces the return loss of the antenna within the bandwidth. When both are loaded onto the antenna element, the operating bandwidth of the antenna is effectively improved.

[0075] S33: Determine the number of tightly coupled array antenna elements based on the orbital angular momentum mode number;

[0076] Alternatively, determining the number of tightly coupled array antenna elements based on the orbital angular momentum mode number includes:

[0077] φ n -φ n-1 =2πlN

[0078] Where N represents the number of tightly coupled array antenna elements, π represents pi, l represents the number of orbital angular momentum modes, and φ n This represents the phase of the input signal of the nth tightly coupled array antenna element and... Indicates the reference phase, φ n-1 This represents the phase of the input signal for the (n-1)th tightly coupled array antenna element.

[0079] When the phase difference between the input signals of adjacent antenna elements exceeds 180°, they will transform into opposite complementary phase differences, and the radiated electromagnetic waves will not conform to the target mode. In the embodiment provided by this invention, the maximum number of target modes for the array's radiated orbital angular momentum is 5. At this time, the phase change of the overall circular array is 1800°. Under the condition of ensuring that the phase difference between adjacent elements is less than 180°, the phase difference between adjacent elements is taken as 150°. The final array consists of 12 antenna elements, with an array radius of 50mm and a height of 23.5mm.

[0080] S34: Based on the number of array antenna elements, the assembled tightly coupled array antenna elements are assembled in a circular array form to obtain a tightly coupled array antenna.

[0081] S4: Design the array antenna feed balun based on the wavelength of the center frequency;

[0082] Specifically, the length of the balun's feeder can be designed based on the center frequency wavelength, and the width of the feeder can be designed based on the target impedance conversion performance. The width is varied in a stepped manner to achieve impedance matching.

[0083] This invention employs a gradient microstrip balun design. The front side features three microstrip patch segments of decreasing length: the first segment is 3mm long and 0.2mm wide; the second is 8.4mm long and 0.15mm wide; and the third is 7.3mm long and 0.1mm wide. The back side of the balun has a curved, gradient ground plane. The dielectric thickness of the balun is 0.6mm, the width is 6mm, and the height is 15.762mm. Its model diagram is shown below. Figure 4 As shown, the simulation results are as follows: Figure 7 As shown.

[0084] S5: Design the feeding network based on the number of tightly coupled array antenna elements;

[0085] The power supply network is implemented by cascading a power divider network and a phase shifter network. The power division ratio of the power divider network is determined by the number of antenna elements, and the shift of the phase shifter network is determined by the number of modes of the orbital angular momentum.

[0086] S6: Assemble the tightly coupled array antenna, the array antenna feed balun, and the feed network to obtain the orbital angular momentum array antenna.

[0087] Table 1 shows the bandwidth of the orbital angular momentum array antenna of the present invention under different orbital angular momentum mode numbers.

[0088] Table 1

[0089]

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A broadband multi-mode orbital angular momentum array antenna, characterized in that, The broadband multi-mode orbital angular momentum array antenna includes: Multiple tightly coupled array antenna elements are arranged sequentially between each other so that the broadband multi-mode orbital angular momentum array antenna is formed into a hollow columnar structure, and the spacing between each tightly coupled array antenna element is less than 0.1 wavelength. Each of the tightly coupled array antenna elements is constructed in a fan shape, so that the broadband multi-mode orbital angular momentum array antenna is formed into a hollow cylindrical structure. Each of the tightly coupled array antenna elements is provided with a first dielectric layer, a dipole, a second dielectric layer, a coupling patch, a feed balun, and a ground plane in sequence from top to bottom. The coupling patch is located below the arm of the dipole. The dipole is symmetrically arranged about the central axis of the sector and a parasitic unit is provided on each side of the dipole. The two ends of the top of the feed balun are respectively attached to the coupling patch, one end of the bottom is connected to the input, and the other end is connected to the ground plane. A feed network is provided on the bottom surface of the ground plane. The top surface of the first dielectric layer is also provided with a grid-structured metasurface, which is constructed as a plurality of spaced trapezoidal metal patches; Each of the tightly coupled array antenna elements is further provided with a grid structure metasurface on its outer side. The top of the grid structure metasurface is connected to the grid structure metasurface, and the bottom is fixed to the outer side of the ground. The grid structure metasurface is constructed as a rectangular metal patch arranged in an array.

2. The broadband multi-mode orbital angular momentum array antenna according to claim 1, characterized in that, The feed balun includes a front side, a back side, and a dielectric plate located between the front side and the back side. The dielectric plate is constructed as a cuboid plate. The front side is provided with microstrip line patches of decreasing length, which extend along the height direction of the cuboid plate and are located on the center line of the width of the cuboid plate. The back side is provided with a triangular floor, the vertex of which is connected to the top of the microstrip line patches of decreasing length, and the length of the base of the triangle is equal to the width of the feed balun.

3. The broadband multi-mode orbital angular momentum array antenna according to claim 2, characterized in that, The material of the dielectric substrate is RO4350B.

4. A design method for a broadband multi-mode orbital angular momentum array antenna based on any one of claims 1-3, characterized in that, The design method includes: S1: Determine the number of orbital angular momentum modes and the center frequency of the electromagnetic wave modulated by the target, based on the application scenario requirements. S2: Design a tightly coupled array antenna array element; S3: Determine the number of tightly coupled array antenna elements based on the orbital angular momentum mode number, and obtain a tightly coupled array antenna by adopting a circular array form; S4: Design the array antenna feed balun based on the wavelength of the center frequency; S5: Design the feeding network based on the number of tightly coupled array antenna elements; S6: Assemble the tightly coupled array antenna, the array antenna feed balun, and the feed network to obtain the orbital angular momentum array antenna.

5. The design method for a broadband multi-mode orbital angular momentum array antenna according to claim 4, characterized in that, S3 includes: S31: Based on the center frequency, use the equivalent impedance characteristic formula to calculate the grating structure metasurface located on the top layer of the antenna and the grid structure metasurface located on the outer layer of the antenna. S32: Assemble the grating structure metasurface and the grid structure metasurface onto each of the tightly coupled array antenna elements to obtain multiple assembled tightly coupled array antenna elements; S33: Determine the number of tightly coupled array antenna elements based on the orbital angular momentum mode number; S34: Based on the number of array antenna elements, the assembled tightly coupled array antenna elements are assembled in a circular array form to obtain a tightly coupled array antenna.

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