Dual-frequency wide-angle scanning antenna based on novel dual-frequency phase shift metasurface

Abstract

The invention discloses a double-frequency wide-angle scanning antenna based on a novel double-frequency phase shift metasurface. The double-frequency wide-angle scanning antenna comprises a metasurface structure, a double-frequency antenna array and a reflecting surface. Symmetrical gradient arrangement is formed by the metasurface units with the dual-frequency independent phase shift function, and the metasurface units are loaded on the dual-frequency antenna array, so that the scanning performance of the dual-frequency antenna array can be improved on two frequency bands, and the application of the metasurface in a multi-frequency-band antenna array is expanded; according to the invention, the metasurface realizes independent phase shift on two frequency bands by multiplexing the double-ring structure, and finally the scanning range of two antenna arrays working in different frequency bands is expanded. According to the invention, the scanning range of the dual-frequency antenna array is expanded from + / -43 degrees to + / -60 degrees at 3.5 GHz, and the gain fluctuation is 2.2 dB; and the gain is expanded from + / -47 degrees to + / -60 degrees at 6 GHz, and the gain fluctuation is 2.24 dB.

Description

Technical Field

[0001] The present invention belongs to the technical field of mobile communication antennas, and in particular relates to a dual-frequency wide-angle scanning antenna based on a novel dual-frequency phase-shift metasurface. Background Art

[0002] Modern wireless communications have become a ubiquitous part of our daily lives. In wireless communications, antenna arrays are widely used in radar, communications and other fields with their unique beam control capabilities. The wide beam scanning of antenna arrays is referred to as wide angle scanning. In order to achieve high-speed and long-distance communications, increase coverage and improve multipath effects, antenna arrays need to have wide angle scanning performance. Expanding the scanning range of antenna arrays and maintaining high-quality wide angle scanning performance are the key challenges currently faced.

[0003] To solve this problem, scholars have used various metasurfaces to improve the performance of antenna arrays. In order to improve the scanning performance of antenna arrays, metasurfaces are designed as impedance matching layers or dielectrics. However, these metasurfaces must be specially designed in conjunction with the antenna to adapt to the antenna array, which limits the flexibility of the design. For fixed antenna arrays, phase gradient metasurfaces composed of phase-shifting metasurface units can be used to extend their scanning range. However, these metasurfaces can only achieve phase shifts within a single frequency band, which limits their application in multi-band antennas. Therefore, there is still a lot of room for the application of phase-shifting metasurfaces in multi-band antennas. Summary of the invention

[0004] The main purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a dual-frequency wide-angle scanning antenna based on a novel dual-frequency phase-shift metasurface.

[0005] The present invention forms a symmetrical gradient arrangement of metasurface units with dual-frequency independent phase shifting function, and loads the metasurface units on a dual-frequency antenna array, so that the scanning performance of the dual-frequency antenna array can be improved in two frequency bands, thereby expanding the application of metasurfaces in multi-band antenna arrays; the present invention multiplexes a dual-ring structure to enable the metasurface to achieve independent phase shifting in two frequency bands, ultimately achieving the improvement of the scanning range of two antenna arrays working in different frequency bands.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A dual-frequency wide-angle scanning antenna based on a dual-frequency phase-shift metasurface, comprising a metasurface structure, a dual-frequency antenna array and a reflecting surface, wherein the metasurface structure is arranged above the dual-frequency antenna array at [12mm, 13mm], preferably at 12.5mm, the metasurface structure has a size of [250, 260] mm×[60, 65] mm, preferably 252mm×63mm, the dual-frequency antenna array is arranged on the upper surface of a dielectric substrate, the reflecting surface is arranged on the lower surface, the dielectric substrate has a size of [240, 260] mm×[58, 65] mm, preferably 240mm×60mm, the reflecting surface is an XOY plane, the center of the reflecting surface is an origin, the metasurface structure, the dual-frequency antenna array and the reflecting surface are symmetrical about the XOZ plane, and the center is located on the Z axis.

[0007] Furthermore, the metasurface structure is composed of 12×3 metasurface units arranged in an array, and the metasurface structure is used to deflect the scanning beam of the dual-frequency antenna array to achieve the expansion of the scanning performance of the dual-frequency antenna array.

[0008] Furthermore, the metasurface unit is composed of three metal layers and two dielectric layers, each of the three metal layers is composed of a square ring and two circular rings embedded in the square ring, wherein the two circular rings are divided into an inner ring and an outer ring, and the centers of the three are on the same axis. At low frequencies, the square ring part can be regarded as inductive, achieving higher transmission performance at low frequencies, the outer ring can be regarded as capacitive, achieving a larger phase shift at low frequencies, and the inner ring can be regarded as an open circuit.

[0009] At high frequencies, the square ring can be regarded as an open circuit, the outer ring can be regarded as inductive at high frequencies, achieving higher projection performance at high frequencies, and the inner ring can be regarded as capacitive, achieving larger phase shift at high frequencies.

[0010] Furthermore, in the metasurface unit, the inner ring and the outer ring have different sizes. By adjusting the size of the outer ring of the metasurface unit, the phase shift of the metasurface unit at low frequency is controlled. By adjusting the size of the inner ring of the metasurface unit, the phase shift of the metasurface structure at high frequency is controlled. The two are independent of each other. The change of the outer ring size will not affect the high-frequency phase shift, and the change of the inner ring size will not affect the high-frequency phase shift. By changing the size of the inner ring and the outer ring, a transmission phase difference of -30° can be achieved between each metasurface unit in two frequency bands, and 6 phase gradients can be formed between 0° and -150°. With the metal layer in the middle layer of the metasurface unit as the XOY plane and the center of the metasurface unit as the origin, the metasurface units with 6 different phase gradients are arranged in a phase increasing manner along the y direction to form a one-dimensional phase gradient metasurface. The metasurface has the same phase distribution in both frequency bands. According to the generalized Snell's law, when the phase gradient metasurface is irradiated by a plane wave, the plane wave will deflect in the y direction in the two frequency bands, thereby realizing the deflection of the scanning beams of the two frequency bands.

[0011] Furthermore, with the reflection surface as the XOY plane and the center of the reflection surface as the origin, the metasurface structure arranges the metasurface units with 6 different phase gradients in a manner that the phase decreases from the XOZ plane to the ±y direction to form a one-dimensional symmetrical phase gradient distribution according to the generalized Snell's law. The metasurface structure has the same phase distribution in both frequency bands, and the phase distribution is symmetrical relative to the XOZ plane. When the metasurface structure in the y<0 part is irradiated by a plane wave, the plane wave will be deflected counterclockwise, and when the metasurface structure in the y>0 part is irradiated by a plane wave, the plane wave will be deflected clockwise.

[0012] Furthermore, after the metasurface structure is loaded above the dual-frequency antenna array, when the array beam scans in a clockwise direction, the metasurface structure in the y>0 part will be illuminated by the beam, and the beam will be deflected clockwise. When the array beam scans in a counterclockwise direction, the metasurface structure in the y<0 part will be illuminated by the beam, and the beam will be deflected counterclockwise, thereby improving the beam scanning range. Since the metasurface structure has the same phase distribution in two frequency bands, the metasurface structure can further improve the scanning performance of the dual-frequency antenna array.

[0013] Furthermore, the dual-frequency antenna array is specifically composed of 6 high-frequency microstrip antennas and 5 low-frequency microstrip antennas arranged in a linear array, using coaxial feeding. The microstrip antenna has a wider beam and can make the array structure more compact, which is conducive to the metasurface structure to better cover the wavefront radiated by the dual-frequency antenna array.

[0014] Furthermore, the height of the metasurface structure from the reflective surface is 0.15 λ L , λ L is the free space wavelength at the lowest frequency point.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The metasurface unit involved in the present invention has independent phase shifts (50°~-200°) at 3.5 GHz and 6 GHz, while maintaining a high transmission amplitude (the average transmission amplitude exceeds 80%). Compared with traditional phase-shifting metasurfaces, it can be used to improve the performance of dual-band antennas, has higher flexibility, and has obvious advantages; (2) In the present invention, the metasurface unit includes a square ring and two circular rings embedded in the square ring. The two circular rings embedded in the square ring are divided into an inner ring and an outer ring. The inner ring and the outer ring have different sizes. By adjusting the size of the outer ring of the metasurface unit, the phase shift of the metasurface unit at low frequency can be controlled. By adjusting the size of the inner ring of the metasurface unit, the phase shift of the metasurface structure at high frequency can be controlled. The two are independent of each other. The change of the outer ring size will not affect the high-frequency phase shift. The change of the inner ring size will not affect the high-frequency phase shift, which improves the degree of freedom of metasurface design. (3) The metasurface structure of the present invention adopts a one-dimensional symmetrical gradient distribution. Specifically, the reflection surface is the XOY surface, the center of the reflection surface is the origin, and the sizes of the inner and outer rings of the metasurface unit increase from the XOZ surface to the ±y direction, thereby realizing the phase gradient distribution in two frequency bands and improving the high-frequency and low-frequency scanning performance in one-dimensional direction at the same time. (4) The present invention uses microstrip antennas to realize dual-frequency antenna arrays. The high-frequency band and low-frequency band have wide half-power beamwidths, which are approximately 87° and 105° at 3.5 GHz and 6 GHz, respectively. The array is relatively compact, so that the metasurface can completely cover the wavefront radiated by the array, ultimately achieving an improvement in the scanning performance of the two frequency bands of the antenna. The scanning range of the antenna array is expanded from ±43° to ±60° at 3.5 GHz, with a gain fluctuation of 2.2 dB; and from ±47° to ±60° at 6 GHz, with a gain fluctuation of 2.24 dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 yes Figure 1 A top view of the metasurface structure after the dual-band antenna radiating unit is hidden; Figure 3 Schematic diagram of the three-dimensional structure of the super surface unit of the present invention; Figure 4 is a schematic diagram of the upper surface of the super surface unit in the present invention; Figure 5 is a transmission coefficient and a transmission phase diagram of a metasurface unit in Embodiment 1 of the present invention; Figure 6a is a graph showing the phase shift and transmission coefficient of the metasurface unit in Example 1 of the present invention as a function of the size of the outer ring, Figure 6b is a graph showing the phase shift and transmission coefficient of the metasurface unit in Example 1 of the present invention as a function of the size of the inner ring; Figure 7 This is a schematic diagram of a phase gradient metasurface composed of six phase gradient metasurface units in the present invention; Figure 8 is Figure 7 The field distribution diagram of the phase gradient metasurface when a plane wave is incident; Fig. 9 is a schematic diagram of the structure of a dual-frequency antenna array radiation unit in Embodiment 1 of the present invention; Fig.10a It is a schematic diagram of impedance matching of a dual-frequency antenna array radiating unit in Embodiment 1 of the present invention; Fig.10b is the radiation pattern of the dual-frequency antenna array radiation unit in Embodiment 1 of the present invention; Fig.11a and Fig.11b is the directional pattern of the dual-frequency antenna array in Example 1 of the present invention when operating at 3.5 GHz and 6 GHz; Fig.12a and Figure 12b It is the directional pattern of the dual-frequency antenna array loaded with the metasurface structure in Example 1 of the present invention when operating at 3.5 GHz and 6 GHz; The reference numerals are explained as follows: 1-metasurface structure, 2-dual-frequency antenna array, 3-reflecting surface, 4-outer ring, 5-inner ring, 6-first dielectric layer, 7-second dielectric layer. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0019] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0020] Example 1 like Figure 1-Figure 2 As shown, a dual-frequency wide-angle scanning antenna based on a dual-frequency phase-shift metasurface is disclosed, including a metasurface structure 1, a dual-frequency antenna array 2 and a reflecting surface 3.

[0021] In this embodiment, a metasurface structure 1, a dual-frequency antenna array 2, and a reflective surface 3 are included. The metasurface structure 1 is placed above the dual-frequency antenna array 2, and the distance from the dual-frequency antenna array 2 is 12.5 mm. The dual-frequency antenna array 2 is arranged on the upper surface of the dielectric substrate, and the reflective surface 3 is arranged on the lower surface of the dielectric substrate. The dielectric substrate of the metasurface structure 1 has a relative dielectric constant of 3.5 and a thickness of 4 mm. The dual-frequency antenna array 2 and the reflective surface 3 are simultaneously arranged on another dielectric substrate, respectively located on the upper and lower surfaces of the dielectric substrate, and the dielectric substrate has a relative dielectric constant of 3.5 and a thickness of 0.9 mm.

[0022] The metasurface structure 1 adopts a coplanar layout of 12×3 metasurface units.

[0023] The three-dimensional structure of the super surface unit is as follows Figure 3 As shown, the metasurface unit is composed of three metal layers and two dielectric layers (respectively, a first dielectric layer 6 and a second dielectric layer 7). The three metal layers are composed of a square ring 3 and two circular rings embedded in the square ring 3, wherein the two circular rings are divided into an outer ring 4 and an inner ring 5. Figure 4 The centers of the square ring 3 and the two circular rings embedded in the square ring 3 are on the same axis, and the side length P of each super surface unit is 21 mm.

[0024] In this embodiment, the transmission coefficient and transmission phase of the metasurface unit are as follows: Figure 5 As shown in the figure, the transmission coefficient and phase shift of the plane wave from the metasurface unit are mainly tested. It is generally believed that the closer the transmission coefficient is to 0, the less the plane wave can propagate through it, and the farther it is from 0, the more the plane wave can propagate through it. When the reflection coefficient reaches above 0.9, it means that 90% of the energy of the plane wave is transmitted. Figure 4 It can be seen that in this embodiment, in both frequency bands, the transmission coefficient of the metasurface unit reaches 90%, achieving high transmission performance.

[0025] In addition, if Figure 3 As shown, the present invention adjusts the size of the inner ring r i With outer ring size r o To change the phase shift of the metasurface, the transmission performance of the metasurface structure can be controlled. In this embodiment, the transmission coefficient and transmission phase of the metasurface unit are relative to the inner ring size. r i With outer ring size r o Changes such as Figure 6a and Figure 6b As shown, the main test is the effect of the size change of the ring structure on the transmission coefficient and transmission phase of the metasurface unit, such as Figure 6a As shown, with the outer ring r oAs the size increases, the transmission phase of the metasurface at 3.5 GHz gradually decreases, while the transmission coefficient remains at a high level, and the transmission phase and transmission coefficient are almost unaffected by the change in the size of the inner ring. Figure 6b As shown, with the inner ring size r i As the transmission phase of the metasurface at 6 GHz gradually decreases, the transmission coefficient is maintained at a high level, and the transmission phase and transmission coefficient are almost unaffected by the change in the size of the outer ring. The metasurface unit designed by the present invention can achieve an independent phase shift of 50°~-200° at 3.5 GHz and 6 GHz while maintaining an average transmission coefficient greater than 0.9. As shown in FIG8 , the metasurface units with 6 different phase gradients are arranged in a phase increasing manner along the +y direction to form a one-dimensional phase gradient metasurface, which has the same phase distribution in both frequency bands. According to the generalized Snell's law, when the phase gradient metasurface is irradiated by a plane wave, the plane wave will deflect in the y direction in the two frequency bands, thereby realizing the deflection of the scanning beams of the two frequency bands.

[0026] like Figure 2 As shown in the figure, with the reflection surface as the XOY plane and the center of the reflection surface as the origin, the final metasurface structure is composed of 12×3 metasurface units and is symmetrical about the XOZ plane. The sizes of the inner and outer rings increase in the ±y direction, that is, the metasurface phase decreases from the XOZ plane to the ±y direction. The metasurface has the same phase distribution in both frequency bands, and the phase distribution is symmetrical relative to the XOZ plane.

[0027] The high-frequency and ground-frequency antenna units used in the dual-frequency antenna array of the present invention are both short microstrip antennas fed by SMA connectors, and the structure is as follows: Fig. 9 As shown in FIG10 , the S parameters and radiation patterns of the low-frequency antenna and the high-frequency antenna are shown. The high-frequency antenna operates at 6 GHz and the low-frequency antenna operates at 3.5 GHz. Both have a wider half-power beamwidth, about 105° for the high frequency and about 87° for the low frequency. The dual-frequency antenna array consists of 6 high-frequency antennas and 5 low-frequency antennas.

[0028] Example 2 This embodiment is based on a dual-frequency wide-angle scanning antenna based on a dual-frequency phase-shift metasurface disclosed in Embodiment 1, and further studies the antenna performance.

[0029] After the metasurface structure is loaded on the antenna array, when the array beam scans in the clockwise direction, the metasurface structure in the y>0 part will be illuminated by the beam, and the beam will be deflected clockwise. When the array beam scans in the counterclockwise direction, the metasurface structure in the y<0 part will be illuminated by the beam, and the beam will be deflected counterclockwise, thereby improving the beam scanning range. Since the metasurface structure has the same phase distribution in both frequency bands, the scanning performance of the dual-frequency antenna array is ultimately improved. Note that the scanning beam of the dual-frequency antenna array is relatively close to that of the metasurface structure wide-angle scanning antenna array. θ = 0° is symmetrical. The beam scanning performance of the dual-frequency antenna array without metasurface working at 3.5 GHz and 6 GHz is as follows: Fig.11a and Fig.11b As shown in the figure, the dual-frequency antenna array loaded with the metasurface structure works at 3.5 GHz and 6 GHz. The beam scanning performance is as follows: Fig.12a and Figure 12b As shown by Fig.11a , Fig.12a By comparison, the scanning range of the antenna array expands from ±43° to ±60° at 3.5 GHz; Fig.11b , Figure 12b By comparison, the scanning range of the antenna array extends from ±47° to ±60° at 6 GHz.

[0030] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0031] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A dual-frequency wide-angle scanning antenna based on a novel dual-frequency phase-shift metasurface, characterized in that: The dual-frequency wide-angle scanning antenna includes a metasurface structure, a dual-frequency antenna array and a reflecting surface. The metasurface structure is arranged above the dual-frequency antenna array, the dual-frequency antenna array is arranged on the upper surface of the dielectric substrate, and the reflecting surface is arranged on the lower surface of the dielectric substrate. The reflecting surface is the XOY plane, the center of the reflecting surface is the origin, and the metasurface structure, the dual-frequency antenna array and the reflecting surface are symmetrical about the XOZ plane, and the center is located on the Z axis.

2. The dual-bandwidth angular scanning antenna according to claim 1, characterized in that: The super surface structure is composed of 12×3 super surface units arranged in an array according to a certain rule.

3. The dual-bandwidth angular scanning antenna according to claim 2, characterized in that: Each metasurface unit consists of three metal layers and two dielectric layers. The three metal layers are composed of a square ring and two circular rings embedded in the square ring. The two circular rings are divided into an inner ring and an outer ring. The centers of the square ring, inner ring and outer ring are on the same axis.

4. The dual-bandwidth angular scanning antenna according to claim 3, characterized in that: The inner ring and outer ring of each supersurface unit of the supersurface structure have different sizes. By adjusting the outer ring size of the supersurface unit, the phase shift of the supersurface unit at low frequency is controlled, and by adjusting the inner ring size of the supersurface unit, the phase shift of the supersurface structure at high frequency is controlled.

5. The dual-bandwidth angular scanning antenna according to claim 3, characterized in that: The reflection surface is taken as the XOY plane and the center of the reflection surface is taken as the origin. According to the generalized Snell's law, the metasurface structure arranges the metasurface units with 6 different phase gradients in a manner in which the phase decreases from the XOZ plane to the ±y direction to form a one-dimensional symmetrical phase gradient distribution, and the phase distribution is symmetrical relative to the XOZ plane. When the metasurface structure in the y<0 part is irradiated by a plane wave, the plane wave will be deflected counterclockwise, and when the metasurface structure in the y>0 part is irradiated by a plane wave, the plane wave will be deflected clockwise, and the metasurface structure has the same phase distribution in two frequency bands, thereby realizing the deflection of the scanning beams of the two frequency bands.

6. The dual-bandwidth angular scanning antenna according to claim 1, characterized in that: The high-frequency and ground-frequency antenna units used in the dual-frequency antenna array are both short microstrip antennas fed by SMA connectors.

7. The dual-bandwidth angular scanning antenna according to claim 6, characterized in that: The dual-frequency antenna array consists of 6 high-frequency antennas and 5 low-frequency antennas.

8. The dual-bandwidth angular scanning antenna according to claim 1, characterized in that: The height of the metasurface structure from the reflective surface is 0.15 λ L , λ L It is the free space wavelength of the lowest frequency point of the dual-band wide-angle scanning antenna.

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