CN109586037B - Lens antenna - Google Patents
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- CN109586037B CN109586037B CN201811402747.4A CN201811402747A CN109586037B CN 109586037 B CN109586037 B CN 109586037B CN 201811402747 A CN201811402747 A CN 201811402747A CN 109586037 B CN109586037 B CN 109586037B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
- H01Q19/06—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using refracting or diffracting devices, e.g. lens
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/0086—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices having materials with a synthesized negative refractive index, e.g. metamaterials or left-handed materials
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Abstract
The invention provides a lens antenna, aiming at ensuring the directivity of the lens antenna and realizing the illusion effect of an optical device, comprising a point light source, a sphere structure with the radius of R and a hemisphere structure with the radius of R, wherein the sphere structure and the hemisphere structure both adopt left-handed materials, a concave structure is arranged on the spherical surface of the hemisphere structure, the curvature radius of the curved surface of the concave structure is the same as that of the spherical surface of the sphere structure, the sphere structure is nested in the concave structure of the hemisphere structure and is tightly attached to the curved surface of the concave structure, the refractive index of the sphere structure is gradually increased in a spherical form in the same direction with the spherical bending direction of the sphere structure along the positive direction of an axis X passing through the sphere center O' of the sphere structure and the virtual sphere center O of the hemisphere structure, the refractive index of the sphere structure is gradually increased along the direction facing the virtual sphere center O from the spherical surface and the concave structure of the, the point light source is arranged in the sphere structure, and the light emitting point of the point light source is positioned at the virtual vertex A of the sphere structure.
Description
Technical Field
The invention belongs to the field of wireless communication, and particularly relates to a lens antenna.
Background
A lens antenna is an antenna that can pass electromagnetic waves and can convert spherical waves of a point source or cylindrical waves of a line source into plane waves to obtain a pencil-shaped, fan-shaped, or other shaped beam. In a microwave communication system, the index characterizing a lens antenna is mainly directional. In order to overcome the defect of weak directivity of the traditional lens antenna, research and development personnel propose a lens antenna based on a metamaterial, for example, a paper entitled "a high-gain lens antenna based on transformation optics" published by Aghanejad I et al in 2013 on "Antennas and performance conference" discloses a high-gain lens antenna based on transformation optics, which comprises a feed source and a hemisphere structure, wherein the feed source is positioned at the spherical vertex of the hemisphere structure, so that the lens antenna is realized by converting spherical waves into plane waves to enhance the directivity, and the structure can only realize the directivity enhancement and does not have the illusion effect of an optical device.
Disclosure of Invention
The present invention is directed to overcome the above-mentioned deficiencies in the prior art, and an object of the present invention is to provide a lens antenna, which can ensure the directivity of the lens antenna and achieve the illusion effect of the optical device.
In order to achieve the purpose, the technical scheme includes that a point light source 1, a spherical structure 2 with the radius of R and a hemispherical structure 3 with the radius of R are included, R is smaller than R, the spherical structure 2 and the hemispherical structure 3 are both made of left-handed materials, a concave structure is arranged on the spherical surface of the hemispherical structure 3, the curvature radius of the curved surface of the concave structure is the same as that of the spherical surface of the spherical structure 2, and the spherical structure 2 is nested in the concave structure of the hemispherical structure 3 and closely attached to the curved surface of the concave structure; the refractive index n of the sphere structure 2 is gradually increased along the positive direction of the axis X passing through the sphere center O' of the sphere structure 2 and the virtual sphere center O of the hemisphere structure 3 in a spherical form with the same spherical bending direction as the sphere structure 3, and the refractive index n of the hemisphere structure 3 is gradually increased1The distance from the virtual vertex A of the hemispherical structure 3 to the intersection point B of the curved surface of the concave structure and the axis x is d, and d is 0.4 r-0.6 r; the point light source 1 is arranged inside the sphere structure 2, the central axis of the spherical wave emitted by the point light source 1 coincides with the axis X, and the light emitting point of the point light source 1 is located at the virtual top point A of the hemisphere structure 3.
In the lens antenna, the bottom surface of the hemisphere structure 3 is obtained by cutting a truncated cone with the width l from the hemisphere along the negative direction of the axis X, and the diameter of the bottom surface is smaller than 2R.
In the lens antenna, the vertex of the curved surface of the concave structure is located on the axis X.
In the lens antenna, the refractive index n of the spherical structure is calculated by the following formula:
wherein a represents the X-axis coordinate of the point light source light emitting point, b represents the Y-axis coordinate of the point light source light emitting point, A1＝1-ax-by，B1X denotes X-ay coordinates within the sphere structure, and Y denotes Y-axis coordinates within the sphere structure.
The refractive index n of the hemispherical structure of the lens antenna1Calculated by the following formula:
wherein n is0Denotes the refractive index at the virtual center of the hemisphere, R denotes the radius of the hemisphere, R1Representing the distance of a point inside the hemisphere to the virtual sphere center O,
a represents the X-axis coordinate of the point light source, b represents the Y-axis coordinate of the point light source, X represents the X-axis coordinate within the spherical structure, and Y represents the Y-axis coordinate within the spherical structure.
Compared with the prior art, the invention has the following advantages:
firstly, the invention adopts a hemispheroid structure with a defective structure, and the structure utilizes the characteristic that the curvature radius of the wavefront of the spherical wave reaching the curved surface of the defective structure is exactly the same as that of the curved surface of the defective structure of the hemispheroid structure, so that the spherical wave can be converted into a plane wave; meanwhile, the spherical structure is filled with the refractive index which is gradually increased along the positive direction of the axis X in the spherical form in the same direction as the spherical bending direction of the hemispherical structure, so that the point light source can generate an illusion image point which is positioned at the spherical center of the spherical structure, the actual feed source filled with the refractive index and the illusion feed source in the air medium generate the same spherical wave, but the positions of the feed sources are different, and the illusion effect of the optical device is realized.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic diagram of the refractive index distribution of the sphere structure and the hemisphere structure of the present invention;
FIG. 3 is a graph of the results of electric field simulations for three embodiments of the present invention;
fig. 4 is a directivity diagram of three embodiments of the present invention.
Detailed Description
The invention is described in further detail below with reference to the following figures and specific examples:
in example 1, the distance d from the imaginary vertex a of the hemispherical structure 3 to the intersection B of the curved surface of the concave structure and the axis X is 0.5 r.
Referring to fig. 1, a lens antenna comprises a point light source 1, a spherical structure 2 with a radius R and a hemispherical structure 3 with a radius R, wherein R is less than R, the spherical structure 2 and the hemispherical structure 3 both adopt left-handed materials, a concave structure is arranged on the spherical surface of the hemispherical structure 3, the curvature radius of the curved surface of the concave structure is the same as that of the spherical surface of the spherical structure 2, and the spherical structure 2 is nested in the concave structure of the hemispherical structure 3 and closely attached to the curved surface of the concave structure; the refractive index n of the sphere structure 2 is gradually increased along the positive direction of the axis X passing through the sphere center O' of the sphere structure 2 and the virtual sphere center O of the hemisphere structure 3 in a spherical form with the same spherical bending direction as the sphere structure 3, and the refractive index n of the hemisphere structure 3 is gradually increased1The distance from the virtual vertex A of the hemispherical structure 3 to the intersection point B of the curved surface of the concave structure and the axis x is d, and d is 0.4 r-0.6 r; the point light source 1 is arranged inside the sphere structure 2, the central axis of the spherical wave emitted by the point light source 1 coincides with the axis X, and the light emitting point of the point light source 1 is located at the virtual top point A of the hemisphere structure 3.
setting a point in a virtual space as w, setting a point in a physical space as z ═ X + iy, wherein X represents an X-axis coordinate in the spherical structure, and Y represents a Y-axis coordinate in the spherical structure; the virtual apex A of the hemisphere structure is positioned in the sphere structure, A is a + ib, a represents the X-axis coordinate of the point light source, a is 0.5cm, b represents the Y-axis coordinate of the point light source, and b is 0. Then the mapping relationship from the physical space to the virtual space is:
wherein A is the conjugate complex number of A, and the left and right ends of formula (1) are derived from z to obtain
Wherein dw denotes the differential of w, dz denotes the differential of z, A11-ax-by and B1＝bx-ay。
The refractive index n within the spherical structure is therefore:
wherein
To represent
The modulus value of (a).
The refractive index n of the sphere structure 2 gradually increases in a spherical form in the same direction as the spherical bending direction of the hemisphere structure 3 along the positive direction of the axis X passing through the sphere center O' of the sphere structure 2 and the virtual sphere center O of the hemisphere structure 3, as shown in fig. 2, the refractive index is related to the color of the drawing, the darker the color represents the smaller the refractive index, the lighter the color represents the larger the refractive index, and the sphere structure in the drawing gradually increases from left to right from the color from the depth to the lightness.
In the formula (3), the spherical structure 2 can be enlarged or reduced by modifying the variables as follows, wherein the volume is enlarged when N is less than 1, and the volume is reduced when N is more than 1.
The point B that sphere of sphere structure 2 and axis X positive direction intersect inlays in hemisphere structure 3's inside, a sunk structure has been formed, the summit of this sunk structure curved surface and the virtual summit A of hemisphere structure 3 all are located axis X, the point B that sphere of sphere structure 2 and axis X positive direction intersect and the summit perfect coincidence of sunk structure curved surface, and in order to obtain better directionality, the bottom surface of hemisphere structure 3 is obtained by hemisphere structure along axis X negative direction cutting off the round platform that the width is l, its bottom surface diameter is less than 2R, R1.5 cm, l 0.135R 0.2025cm, the refracting index n of hemisphere structure 3 equals 0.2025cm1Calculated by the following formula:
wherein n is0Denotes the refractive index at the virtual center of the hemisphere, n0R denotes the radius of the hemisphere, R1.331Representing the distance of a point inside the hemisphere to the virtual sphere center O,
refractive index n of hemispherical structure 31The refractive index gradually increases from the spherical surface and the concave structure surface of the hemispherical structure 3 to the virtual spherical center O, as shown in fig. 2, the deeper the color, the smaller the refractive index, and the lighter the color, the larger the refractive index, and the color in the figure changes from the deep to the light from the spherical surface and the concave structure surface of the hemispherical structure 3 to the virtual spherical center O, which represents the refractive index.
The left-handed material is a material with a negative dielectric constant and a negative magnetic permeability, and the refractive index is calculated through the dielectric constant and the magnetic permeability.
In the invention, the refractive indexes in the spherical structure and the hemispherical structure can be realized by two methods, wherein in the first method, the refractive indexes can be obtained by adopting a formula (3) and a formula (5); in the second method, the refractive index can be obtained by discretizing the graded refractive indexes of the formula (3) and the formula (5), and since the refractive index of the spherical structure is the same on the same spherical surface as the spherical bending direction of the hemispherical structure 3, the graded refractive index can be discretized in the form of increasing m by such a spherical surface; the curved surface formed by points with the same refractive index of the hemispherical structure is a spherical surface, and discretization is carried out in a mode of increasing m through concentric spheres with an imaginary sphere center O. The two methods have similar effects if the number of discrete layers is large, but the overall result obtained by discretizing the refractive index is slightly inferior to that obtained by the graded refractive index, because the discrete refractive index cannot completely contain all the graded refractive index values, so the invention is realized by simulating the graded refractive index.
In embodiment 2, the structure of this embodiment is the same as that of embodiment 1, and only the distance from the virtual vertex a of the semispherical structure 3 to the intersection point B of the curved surface of the concave structure and the axis X is adjusted: d is 0.4 r.
The technical effects of the present invention will be described in detail below with reference to simulation experiments.
1. Simulation conditions and contents:
the following simulation experiments were carried out based on 3 embodiments of the present invention, all using COMSOL Multiphysics 5.2 Multiphysics simulation software.
2. And (3) simulation result analysis:
referring to fig. 3, the spherical waves emitted by the point light source are still distributed spherically in the space only when passing through the spherical structure, as shown in fig. 3(a), 3(b) and 3(c), the spherical waves distributed in the space are emitted from the feed source located at the spherical center of the spherical structure, but are generated by the feed source located at the virtual vertex a of the hemispherical structure, so that the illusion effect of the optical device is realized; the spherical wave passing through the sphere structure and then passing through the hemisphere structure is converted into a plane wave, because the optical paths of the wave front emitted by the point light source when the wave front propagates to the bottom surface of the hemisphere structure are the same, the spherical wave is converted into the plane wave. The plane wave in fig. 3(a) is slightly better than that in fig. 3(B) and 3(c) because when the distance d from the virtual vertex a of the hemispherical structure 3 to the intersection point B of the curved surface of the concave structure and the axis X deviates from 0.5r, the radius of curvature of the wavefront forming curved surface, which is formed by the spherical wave emitted by the point light source 1 and reaches the curved surface of the concave structure after passing through the refractive index inside the spherical structure 2, is different from that of the curved surface of the concave structure.
Referring to fig. 4, the far-field mode exhibits good directivity between an angle of-30 ° to +30 °, and fig. 4(a) the main beam is located in a range of-7 ° to +7 °, which may be up to 20dB or more, and the beam is narrow; whereas the main beam of fig. 4(b) ranges from-12 ° to +12, the beam is wider than that of fig. 4(a), and the result is slightly worse; the main beam of fig. 4(c) is in the range of-15 ° - +15, the beam is wider than that of fig. 4(a), and the side lobe is larger, which is not as good as fig. 4(a) and 4(b), but the directivity can be achieved as well.
The simulation results show that the invention can realize the illusion effect of the antenna while realizing the conversion from spherical waves to plane waves to enhance the directivity of the lens antenna.
Claims (3)
1. A lens antenna is characterized by comprising a point light source (1), a sphere structure (2) with the radius of R and a hemisphere structure (3) with the radius of R, wherein R is less than R, the sphere structure (2) and the hemisphere structure (3) both adopt left-handed materials, a concave structure is arranged on the spherical surface of the hemisphere structure (3), the curvature radius of the curved surface of the concave structure is the same as that of the spherical surface of the sphere structure (2), and the sphere structure (2) is nested in the concave structure of the hemisphere structure (3) and closely attached to the curved surface of the concave structure; the refractive index n of the spherical structure (2) is positive along an axis X passing through the center O' of the spherical structure (2) and the virtual center O of the hemispherical structure (3)The direction is gradually increased by taking the intersection point of the negative direction of the axis X and the spherical structure (2) as a starting point and the intersection point of the positive direction of the axis X and the spherical structure (2) as an end point, and the formula of the refractive index n is as follows:
wherein a represents the X-axis coordinate of the light emitting point of the point light source (1), b represents the Y-axis coordinate of the light emitting point of the point light source (1), A1＝1-ax-by，B1Bx-ay, X denotes X-axis coordinates within the sphere structure (2), and Y denotes Y-axis coordinates within the sphere structure (2); the refractive index n of the hemispherical structure (3)1Along the positive direction of an axis X passing through the sphere center O' of the sphere structure (2) and the virtual sphere center O of the hemisphere structure (3), the intersection of the hemisphere structure (3) and the sphere structure (2) is taken as a starting point, the intersection of the positive direction of the axis X and the hemisphere structure (3) is taken as an end point, the refractive index n of the optical fiber gradually increases, and the optical fiber has the same refractive index as the optical fiber1The formula is as follows:
wherein n is0Denotes the refractive index at the virtual center O of the hemisphere (3), R denotes the radius of the hemisphere (3), R1Represents the distance from a point inside the hemisphere (3) to the virtual sphere center O,
a represents the X-axis coordinate of the light emitting point of the point light source (1), b represents the Y-axis coordinate of the light emitting point of the point light source (1), X represents the X-axis coordinate in the sphere structure (2), and Y represents the Y-axis coordinate in the sphere structure (2); the distance from the virtual vertex A of the hemispherical structure (3) to the intersection point B of the curved surface of the concave structure and the axis X is d, and d is 0.4 r-0.6 r; the point light source (1) is arranged in the sphere structure (2), the central axis of spherical waves emitted by the point light source (1) coincides with the axis X, and the light emitting point of the point light source (1) is located at the virtual top point A of the hemisphere structure (3).
2. A lens antenna according to claim 1, characterized in that the base of said hemispherical structure (3) is obtained by truncating a segment of width l of the hemisphere in a direction negative to the axis X, the diameter of the base of said hemispherical structure (3) being less than 2R.
3. A lens antenna according to claim 1, wherein the apex of the curved surface of the concave structure is located on the axis X.
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| CN201811402747.4A CN109586037B (en) | 2018-11-23 | 2018-11-23 | Lens antenna |
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| CN201811402747.4A CN109586037B (en) | 2018-11-23 | 2018-11-23 | Lens antenna |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1557039A (en) * | 2001-09-28 | 2004-12-22 | ס�ѵ�����ҵ��ʽ���� | Radio wave lens antenna apparatus |
| CN102769208A (en) * | 2011-05-03 | 2012-11-07 | 中国科学院上海微系统与信息技术研究所 | Gradient refractive index medium lens and gradient refractive index medium lens antenna |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7301504B2 (en) * | 2004-07-14 | 2007-11-27 | Ems Technologies, Inc. | Mechanical scanning feed assembly for a spherical lens antenna |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1557039A (en) * | 2001-09-28 | 2004-12-22 | ס�ѵ�����ҵ��ʽ���� | Radio wave lens antenna apparatus |
| CN102769208A (en) * | 2011-05-03 | 2012-11-07 | 中国科学院上海微系统与信息技术研究所 | Gradient refractive index medium lens and gradient refractive index medium lens antenna |
Non-Patent Citations (2)
| Title |
|---|
| Quarter-sphere Luneburg lens scanning antenna;Nasiha Nikolic et al.;《2012 15 International Symposium on Antenna Technology and Applied Electromagnetics》;20120628;1-4 * |
| 透镜式卫星天线;刘进军;《卫星电视与宽带多媒体》;20061020;46-49 * |
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