Cylindrical Conformal Active Metasurface Antenna Based on Amplitude Regulation

Abstract

The present invention proposes a cylindrical conformal active metasurface antenna based on amplitude regulation to solve the problem that existing active metasurface antennas can only perform beam scanning on a plane. It includes a feeding structure and a radiation structure. The feeding structure includes a dielectric substrate and metal patches printed on the upper and lower surfaces of the dielectric substrate. The metal patch on the upper surface is etched with a coupling slot and metallized vias are arranged on both sides. The radiation structure includes a dielectric substrate and radiation patches printed on the upper surface of the dielectric substrate. Two H-shaped slots are etched in the metal patches of the radiation patches, and PIN diodes are loaded on the strip-shaped metal patches. The two ends of the PIN diodes are respectively connected to the metal on the lower surface of the feeding structure and an external bias circuit through short-circuit metallized vias and DC bias metallized vias. A voltage is applied to the DC bias metallized vias to control the radiation intensity distribution of the radiation patch array, realizing the beam scanning of the cylindrical conformal active metasurface antenna, which can be used in the communication system of a cylindrical structure carrier platform.

Description

Technical Field

[0001] The present invention belongs to the field of microwave technology, and relates to a metasurface antenna, specifically to a cylindrical conformal active metasurface antenna based on amplitude modulation, which can be used in communication systems with a carrier platform having a cylindrical structure. Background Art

[0002] Metasurface antennas are widely used in receiving and transmitting antennas of communication systems due to their characteristics of simple structure, low cost, and strong electromagnetic wave manipulation ability. Metasurface antennas are divided into passive metasurface antennas and active metasurface antennas according to whether they are loaded with active devices. Among them, passive metasurface antennas can form a highly directive beam by etching specific unit structures and arranging them according to certain rules. However, once the passive metasurface antenna is processed, its beam direction is fixed, and beam scanning cannot be achieved. Active metasurface antennas can realize dynamic regulation of the electromagnetic performance of metasurface units by loading active devices, thereby realizing beam scanning of the antenna. Existing active metasurface antennas are mostly planar structures. When the antenna needs to be conformal to a cylindrical carrier platform, it is difficult to achieve beam scanning on the cylindrical carrier platform.

[0003] For example, the patent application with the publication number CN 112751183 A and the name "A Beam-Scanning Circularly Polarized Leaky-Wave Antenna Based on Digital Coding" discloses a circularly polarized active metasurface antenna with beam-scanning ability based on digital coding, which specifically includes: an upper microstrip structure, a dielectric substrate, and a bottom metal floor; branches and PIN diodes are connected to both sides of the microstrip line and are connected to the bottom metal floor through metallized vias; an open-loop slot is etched on the bottom metal floor as a circularly polarized radiator. By controlling the on-off state of the PIN diodes, the circularly polarized beam direction of the antenna is controlled. The present invention obtains the beam directions under different coding states by encoding and combining the units. However, when the number of units increases, the number of coding combinations increases exponentially, and it is difficult for the present invention to achieve beam scanning of a large-scale array. In addition, the present invention only realizes beam scanning of the active metasurface antenna under a planar structure, and when the antenna needs to be conformal to a cylindrical carrier, the present invention cannot achieve beam scanning of the active metasurface antenna under cylindrical conformal design. Summary of the Invention

[0004] The object of the present invention is to overcome the defects existing in the above-mentioned prior art, and propose a cylindrical conformal active metasurface antenna based on amplitude modulation, which is used to solve the technical problem that beam scanning of active metasurfaces cannot be achieved under cylindrical conformal design in the prior art.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A cylindrical conformal active metasurface antenna based on amplitude regulation, comprising a feeding structure 1 and a radiation structure 2 stacked on top of each other, where:

[0007] The feeding structure 1 includes a rectangular flexible first dielectric substrate 11, a first metal patch 12 printed on the lower surface of the first dielectric substrate 11, and a second metal patch 13 on the upper surface; two parallel-coupled slit arrays are etched on the second metal patch 13, and each coupled slit array consists of N periodically arranged coupled slits 131; a linear array of metallized vias 14 for connecting the first metal patch 12 and the second metal patch 13 is provided on the first dielectric substrate 11 along the length direction of the coupled slit array and outside each coupled slit array; where N≥2;

[0008] The radiation structure 2 includes a rectangular flexible second dielectric substrate 21 and a patch array printed on its upper surface corresponding to the position of the coupled slit array, and each patch array consists of N periodically arranged radiation patches 22; the radiation patch 22 includes a rectangular metal patch 221 and a strip-shaped metal patch 222 located on one long side of the rectangular metal patch 221 close to the second dielectric substrate 21; two H-shaped slits 2211 are etched on the rectangular metal patch 221; an active device 2221 is loaded on the strip-shaped metal patch 222; both ends of the active device 2221 are connected to the first metal patch 12 and an external bias circuit through short-circuit metallized vias 3 and DC bias metallized vias 4 that penetrate the first dielectric substrate 11 and the second dielectric substrate 21;

[0009] The feeding structure 1 and the radiation structure 2 are bent into a shape conforming to the carrier to be conformal, forming a hollow cylindrical structure with the first dielectric substrate 11 on the inside and the second dielectric substrate 21 on the outside;

[0010] By applying voltages with different values to the DC bias metallized vias 4, the active device 2221 is controlled to present different working states, so as to realize the regulation of the radiation intensity I n of each radiation patch 22; by adjusting the radiation intensity of each radiation patch 22 in the radiation structure 2, the beam scanning of the cylindrical conformal active metasurface antenna is realized; the radiation intensity I n of the nth radiation patch 22 in the radiation structure 2 is calculated by the formula:

[0011]

[0012] where, λ0 is the working frequency wavelength of the cylindrical conformal active metasurface antenna, ε ris the relative permittivity of the first dielectric substrate 11, w is the spacing between two rows of linearly arranged metallized vias 14, c is the spacing between the centers of two adjacent metallized vias in the linearly arranged metallized vias 14, d is the diameter of the metallized vias in the linearly arranged metallized vias 14, x n is the distance of the nth radiating patch relative to the starting radiating patch in the radiating patch array, θ0 is the beam pointing of the cylindrical conformal active metasurface antenna, k0 is the propagation constant in free space, and ρ0 is the curvature radius of the cylindrical conformal active metasurface antenna.

[0013] For the above-mentioned cylindrical conformal active metasurface antenna based on amplitude modulation, on the second metal patch 13, the coupling slot 131 etched thereon adopts an H-shaped coupling slot structure, and the transverse branch of the H-shaped coupling slot is parallel to the linearly arranged metallized vias 14; and the coupling slots 131 in one coupling slot array etched on the second metal patch 13 are arranged in a staggered manner with the coupling slots 131 at the corresponding positions in another coupling slot array, and the midpoint of the transverse branch of the H-shaped structure of the coupling slot 131 in one coupling slot array is parallel to the short side of the first dielectric substrate 11 with the connection line between the midpoints of two adjacent coupling slots 131 in another coupling slot array.

[0014] For the above-mentioned cylindrical conformal active metasurface antenna based on amplitude modulation, on the rectangular metal patch 221, the transverse branch of the H-shaped slot 2211 etched thereon is parallel to the long side of the rectangular metal patch 221, and the two longitudinal branches adopt a composite structure composed of an arc and two straight lines, and the intersection point of the two straight lines is connected to the transverse branch of the H-shaped slot 2211.

[0015] For the above-mentioned cylindrical conformal active metasurface antenna based on amplitude modulation, on the second metal patch 13, two trapezoidal metal patches 132 are provided, which are respectively used for impedance matching with the feed input port and impedance matching with the load port.

[0016] For the above-mentioned cylindrical conformal active metasurface antenna based on amplitude modulation, the active device 2221 adopts a PIN diode or a varactor diode.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] In the present invention, by applying voltages with different values to the DC-biased metallized vias, the active device is controlled to present different working states, and thus the radiation intensity I of each radiating patch is realized. nRegulation; further, according to the required beam direction of the cylindrical conformal active metasurface antenna, the required radiation intensity of each radiation patch in the radiation structure is calculated, and by adjusting the radiation intensity distribution of each radiation patch in the radiation structure, the problem that the existing active metasurface antenna can only perform beam scanning in the planar state is solved, and beam scanning of the active metasurface antenna under the cylindrical conformal design is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the schematic diagram of the overall structure expansion of the present invention;

[0020] Figure 2 (a) is the schematic diagram of the second metal patch of the feeding structure of the present invention;

[0021] Figure 2 (b) is the schematic diagram of the radiation patch of the radiation structure of the present invention;

[0022] Figure 3 (a) is the simulation result of the transmission coefficient of two states of the radiation patch of the present invention;

[0023] Figure 3 (b) is the simulation result of the transmission phase of two states of the radiation patch of the present invention;

[0024] Figure 3 (c) is the simulation result of the radiation gain of two states of the radiation patch of the present invention;

[0025] Figure 4 (a) is the simulation result of the negative scan of the cylindrical conformal active metasurface antenna of the present invention;

[0026] Figure 4 (b) is the simulation result of the positive scan of the cylindrical conformal active metasurface antenna of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Referring to Figure 1 , the present invention has a feeding structure 1 and a radiation structure 2 that are stacked on top of each other. The feeding structure 1 includes a rectangular flexible first dielectric substrate 11, a first metal patch 12 printed on the lower surface of the first dielectric substrate 11, and a second metal patch 13 on the upper surface; two parallel arranged coupling slot arrays are etched on the second metal patch 13, and each coupling slot array is composed of 27 periodically arranged coupling slots 131; referring to Figure 2(a) For the structural parameters of the H-shaped coupling slot 131, l4 = 8 mm, l5 = 5 mm, w4 = 1 mm, w5 = 4 mm; on the first dielectric substrate 11, there are two metallized via linear arrays 14 located on both sides of the slot array in the length direction for connecting the first metal patch 12 and the second metal patch 13. The distance w between the two rows of metallized via linear arrays 14 is 50 mm, the distance c between the centers of two adjacent metallized vias is 2 mm, and the diameter d of the metallized via is 1.6 mm; the thickness of the first dielectric substrate 11 is 2 mm, and the relative permittivity is = 4.4;

[0029] The radiation structure 2 includes a rectangular flexible second dielectric substrate 21 and a patch array printed on its upper surface corresponding to the position of the coupling slot array. Each patch array consists of 27 radiation patches 22 arranged periodically; the radiation patch 22 includes a rectangular metal patch 221 and a strip-shaped metal patch 222 located on one long side of the rectangular metal patch 221 close to the second dielectric substrate 21; two H-shaped slots 2211 are etched on the rectangular metal patch 221; an active device 2221 is loaded on the strip-shaped metal patch 222. The active device 2221 selects a PIN diode, and the equivalent parameters of the PIN diode in the cut-off state are 0.2 pf, and the equivalent parameters in the conduction state are 2 Ω; both ends of the active device 2221 are connected to the first metal patch 12 and an external bias circuit through short-circuit metallized vias 3 and DC bias metallized vias 4 that penetrate the first dielectric substrate 11 and the second dielectric substrate 21; the thickness of the second dielectric substrate 21 is 2 mm, and the relative permittivity is = 4.4;

[0030] Bend the feeding structure 1 and the radiation structure 2 into the shape of the carrier to be conformal, forming a hollow cylindrical structure with the first dielectric substrate 11 on the inside and the second dielectric substrate 21 on the outside;

[0031] Refer to Figure 2(b) The rectangular metal patch 221, the transverse branches of the H-shaped slot 2211 etched thereon are parallel to the long side of the rectangular metal patch 221, and the two longitudinal branches adopt a composite structure composed of an arc and two straight lines, where the two ends of the arc are respectively connected to the two ends of the two straight lines, and the intersection of the other ends of the two straight lines is connected to the transverse branch of the H-shaped slot 2211. Its structural parameters are that the adjacent interval p of the radiation patch 22 is 11 mm, the structural dimensions of the rectangular patch 221 are a = 25 mm, l1 = 12 mm, the structural dimensions of the strip patch 222 are w1 = 1.2 mm, b = 0.6 mm, and the structural parameters of the H-shaped slot 2211 are l2 = 6 mm, l3 = 10 mm, w2 = 0.6 mm, w3 = 0.8 mm. The two longitudinal branches of the H-shaped slot 2211 can excite currents in the same arrangement direction as the radiation patch 22, thus ensuring that the staggered arrangement state of the coupling slots 131 will not introduce an anti-phase phase difference while reducing the spacing, and realizing the beam scanning of the cylindrical conformal active metasurface antenna at large angles.

[0032] The working principle of the present invention is as follows:

[0033] The cylindrical conformal active metasurface antenna in the present invention can be regarded as a cylindrical conformal traveling wave antenna. For a planar traveling wave antenna, there is an inherent phase difference k g *p between the radiation patches, where p is the spacing between adjacent radiation patches. Therefore, when designing the antenna, by controlling the radiation intensity of each radiation patch of the planar traveling wave antenna, the antenna beam pointing can be made consistent with the desired direction. For a planar traveling wave antenna, when its beam pointing is θ0, the calculation formula for the radiation intensity of the nth radiation patch is:

[0034] I n = cos(k g *x n - k0 * sin(θ0))

[0035] When it is cylindrically conformal, the wave vector of the radiation wave is: And the field point on the curved surface can be analyzed as: Therefore, the wavefront phase information of the radiation wave on the curved surface is: Referring to Figure 1 , with the positive z-axis as the 0-degree radiation direction of the cylindrical conformal active metasurface antenna, is the angle between a point on the cylindrical conformal active metasurface antenna and the positive z-axis, then the coordinates can be expressed as:

[0036]

[0037] So Therefore, when the beam pointing of the cylindrical conformal active metasurface antenna is θ0, the calculation formula for the radiation intensity of the nth radiation patch is corrected to:

[0038]

[0039] The radiation intensities of the respective radiation patches obtained by calculation in the above formula are continuous values. In the present invention, the active device 2221 is a PIN diode, and the equivalent parameters of the PIN diode in the cut-off state are 0.2 pF, and the equivalent parameters in the conduction state are 2 Ω. The two operating states corresponding to the PIN diode can only simulate two radiation intensities. Therefore, it is necessary to discretize the continuous radiation intensity values of the radiation patches. Therefore, the operating state of the PIN diode on the nth radiation patch is as follows:

[0040]

[0041] Among them, 1 represents that the PIN diode is in the conduction state, and 0 represents that the PIN diode is in the cut-off state. That is, when the radiation intensity is non-negative, the diode is in the cut-off state, and the radiation intensity of the radiation patch is the largest. When the radiation intensity is negative, the diode is in the conduction state, and the radiation intensity of the radiation patch is the smallest. By applying different voltages to the DC bias metallized vias 4, the conduction and cut-off of the PIN diode are controlled. Therefore, by applying voltages to each diode according to the distribution of the diode operating states, the beam scanning of the cylindrical conformal active metasurface antenna can be realized.

[0042] The following is a further description of the technical effects of the present invention through simulation experiments.

[0043] 1. Simulation conditions and content.

[0044] The following simulation experiments carried out based on the embodiments of the present invention are all completed using the CST MICROWAVE STUDIO simulation software.

[0045] Simulation 1: Simulate the electrical performance parameters of the radiation patches in the embodiments of the present invention. The simulation results are shown in Figure 3 (a), 3(b), and 3(c);

[0046] Simulation 2: Simulate the beam scanning of the cylindrical conformal active metasurface antenna in the embodiments of the present invention. The simulation results are shown in Figure 4 (a) and 4(b);

[0047] 2. Analysis of simulation results

[0048] Referring to Figure 3 (a), in the embodiments of the present invention, by simulating the propagation coefficients in the radiation patches in the two operating states of the PIN diode, at the operating frequency point, the difference between the transmission coefficients of the two states is greater than -0.6 dB, which proves that part of the energy is radiated through the radiation patches in the radiation state.

[0049] Reference Figure 3 (b), in the embodiment of the present invention, by simulating the phase of the propagation coefficient in the radiation patch under two working states of the PIN diode, at the working frequency point, the phase difference between the two states is less than 2 degrees, ensuring that the different states of the radiation patch introduce less error, thereby controlling the accuracy of beam scanning.

[0050] Reference Figure 3 (c), in the embodiment of the present invention, by simulating the radiation intensity of the radiation patch under two working states of the PIN diode, the difference in radiation gain of the radiation patch between the two states is 11 dB, meeting the requirement that the radiation patch has two working states with different radiation intensities.

[0051] Reference Figure 4 (a), in the embodiment of the present invention, by simulating the negative scanning angle of the cylindrical conformal active metasurface antenna at a scanning interval of 10 degrees, it can be seen that the cylindrical conformal active metasurface antenna can scan from 0 degrees to -60 degrees at intervals of 10 degrees, meeting the requirements of precise beam scanning and large-angle beam pointing.

[0052] Reference Figure 4 (b), in the embodiment of the present invention, by simulating the positive scanning angle of the cylindrical conformal active metasurface antenna at a scanning interval of 10 degrees, it can be seen that the cylindrical conformal active metasurface antenna can scan from 0 degrees to 60 degrees at intervals of 10 degrees, meeting the requirements of precise beam scanning and large-angle beam pointing.

[0053] The above description is only the preferred embodiment of the present invention and does not limit the present invention. For those of ordinary skill in the art, several deformations and improvements can be made without departing from the innovative concept of the present invention, but these changes all fall within the protection scope of the present invention.

Claims

1. A cylindrical conformal active metasurface antenna based on amplitude regulation, comprising a feeding structure (1) and a radiation structure (2) stacked on top of each other; characterized in that: The feeding structure (1) includes a rectangular flexible first dielectric substrate (11), a first metal patch (12) printed on the lower surface of the first dielectric substrate (11), and a second metal patch (13) printed on the upper surface; two parallel-arranged coupling slot arrays are etched on the second metal patch (13), and each coupling slot array is composed of N periodically arranged coupling slots (131); a linear array of metallized vias (14) for connecting the first metal patch (12) and the second metal patch (13) is arranged on the first dielectric substrate (11) along the length direction of the coupling slot array and outside each coupling slot array; where N≥2; The radiation structure (2) includes a rectangular flexible second dielectric substrate (21) and a patch array printed on its upper surface corresponding to the position of the coupling slot array, and each patch array is composed of N periodically arranged radiation patches (22); the radiation patch (22) includes a rectangular metal patch (221) and a strip-shaped metal patch (222) located on one side of the rectangular metal patch (221) close to the long side of the second dielectric substrate (21); two H-shaped slots (2211) are etched on the rectangular metal patch (221); an active device (2221) is loaded on the strip-shaped metal patch (222); both ends of the active device (2221) are connected to the first metal patch (12) and an external bias circuit through a short-circuit metallized via (3) and a DC bias metallized via (4) passing through the first dielectric substrate (11) and the second dielectric substrate (21); The feeding structure (1) and the radiation structure (2) are bent into the shape of the carrier to be conformal, forming a hollow cylindrical structure with the first dielectric substrate (11) on the inside and the second dielectric substrate (21) on the outside; By applying voltages with different values to the DC-biased metallized vias (4), different operating states of the active device (2221) are controlled to achieve the regulation of the radiation intensity I of each radiation patch (22). n The beam scanning of the cylindrical conformal active metasurface antenna is realized by adjusting the radiation intensity of each radiation patch (22) in the radiation structure (2). The calculation formula for the radiation intensity I of the nth radiation patch (22) in the radiation structure (2) is as follows: n The calculation formula is: Among them, λ0 is the working frequency wavelength of the cylindrical conformal active metasurface antenna, ε r is the relative dielectric constant of the first dielectric substrate (11), w is the spacing between two rows of linearly arranged metallized vias (14), c is the spacing between the centers of two adjacent metallized vias in the linearly arranged metallized vias (14), d is the diameter of the metallized vias in the linearly arranged metallized vias (14), x n is the distance of the nth radiation patch relative to the starting radiation patch in the radiation patch array, θ0 is the beam pointing of the cylindrical conformal active metasurface antenna, k0 is the propagation constant in free space, and ρ0 is the curvature radius of the cylindrical conformal active metasurface antenna.

2. The cylindrical conformal active metasurface antenna based on amplitude regulation according to claim 1, wherein For the second metal patch (13), the coupling slots (131) etched thereon adopt an H-shaped coupling slot structure, and the transverse branch of the H-shaped coupling slot is parallel to the linear array of metallized vias (14); and the coupling slots (131) in one coupling slot array etched on the second metal patch (13) are arranged in a staggered manner with the coupling slots (131) at the corresponding positions in the other coupling slot array, and the midpoint of the transverse branch of the H-shaped structure of the coupling slots (131) in one coupling slot array and the midpoint connection of two adjacent coupling slots (131) in the other coupling slot array are parallel to the short side of the first dielectric substrate (11).

3. The cylindrical conformal active metasurface antenna based on amplitude regulation according to claim 1, wherein For the rectangular metal patch (221), the transverse branch of the H-shaped slot (2211) etched thereon is parallel to the long side of the rectangular metal patch (221), and the two longitudinal branches adopt a composite structure composed of an arc and two straight lines, and the intersection of the two straight lines is connected to the transverse branch of the H-shaped slot (2211).

4. The cylindrical conformal active metasurface antenna based on amplitude regulation according to claim 1, wherein The second metal patch (13) is provided with two trapezoidal metal patches (132) thereon, which are respectively used for impedance matching with a feed input port and impedance matching with a load port.

5. The cylindrical conformal active metasurface antenna based on amplitude regulation according to claim 1, wherein The active device (2221) is a PIN diode or a varactor diode.

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