CN108306112B - Cassegrain antenna based on super surface - Google Patents
Cassegrain antenna based on super surface Download PDFInfo
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- CN108306112B CN108306112B CN201711345301.8A CN201711345301A CN108306112B CN 108306112 B CN108306112 B CN 108306112B CN 201711345301 A CN201711345301 A CN 201711345301A CN 108306112 B CN108306112 B CN 108306112B
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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
- H01Q15/14—Reflecting surfaces; Equivalent structures
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- 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
- H01Q19/10—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 reflecting surfaces
- H01Q19/18—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 reflecting surfaces having two or more spaced reflecting surfaces
- H01Q19/185—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 reflecting surfaces having two or more spaced reflecting surfaces wherein the surfaces are plane
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Abstract
The invention provides a cassegrain antenna based on a super surface, which aims to reduce phase compensation errors of the antenna and simplify an antenna structure at the same time, and comprises a slab waveguide, a main reflector, a secondary reflector and a feed source, wherein the main reflector, the secondary reflector and the feed source are clamped between two metal plates of the slab waveguide; the feed source is positioned at the midpoint of the main reflector opposite to the secondary reflector phase control layer, the virtual focus of the secondary reflector coincides with the focus of the main reflector, and the real focus coincides with the phase center of the feed source.
Description
Technical Field
The invention belongs to the technical field of antennas, relates to a Cassegrain antenna, and particularly relates to a Cassegrain antenna with a phase mutation super-surface planar structure based on the generalized Snell's theorem, which can be used in the microwave field.
Technical Field
The microwave reflector antenna is mainly a parabolic antenna, and a high-directivity radiation pattern is formed by utilizing the collimation effect of the parabolic reflector on electromagnetic waves. The Cassegrain antenna is characterized in that a hyperboloid auxiliary reflecting surface is added on the basis of a parabolic antenna, and electromagnetic waves form a high-directivity radiation pattern after being reflected by the auxiliary reflecting surface and the main reflecting surface. Compared with the common parabolic antenna, the double-mirror design can realize the radiation performance of the long-focus parabolic surface by using the short-focus parabolic surface, and has more advantages in practical application. On one hand, the added subreflector is more convenient for designing the orofacial field distribution, and the radiation performance of the antenna can be optimized; on the other hand, the feed source is arranged at the position close to the vertex of the main reflecting surface, so that the length of the feed line is greatly shortened, the loss is reduced, and the noise coefficient of the antenna system is reduced. The reflecting surface of a typical cassegrain antenna is formed by a metal surface processed into a curved surface contour, and although the design is simple, the processing requirement is high.
In order to solve the problem that a curved reflecting surface for regulating and controlling electromagnetic waves by profile design is inconvenient to process and assemble, the conventional research utilizes a metamaterial to regulate and control the electromagnetic waves, and realizes a planar structure Cassegrain antenna by printing a microstrip board. For example, the invention of Chinese patent, application publication No. CN 102800994A, entitled "Cassegrain-type metamaterial antenna", discloses a Cassegrain-type metamaterial antenna, which realizes a Cassegrain-type metamaterial antenna with a flat plate structure by arranging a planar snowflake-shaped cross-shaped metal microstructure in the middle of a grounded dielectric plate and covering a refractive index gradient change metamaterial on a metal reflecting surface to approximate the reflection characteristic of a curved reflector, but the phase compensation method is that electromagnetic waves pass through the metamaterial twice in sequence, wave front calibration is carried out by utilizing different wave length changes of different constitutive parameters of the metamaterial on a propagation path under the same physical distance, on one hand, the phase path design based on a metamaterial layer is based on the premise that the electromagnetic waves are vertically incident on the reflecting surface, the change of incident angles when the electromagnetic waves are obliquely incident is not considered, theoretically, the refracted waves can be perpendicular to the reflecting surface only when the refractive index is infinite, a large phase compensation error exists, and the phase error is increased along with the increase of the incident angle, so that the radiation characteristic and the application range of the metamaterial-based Cassegrain antenna are limited; on the other hand, because the phase compensation of the reflected wave front is based on that the electromagnetic wave passes through the metamaterial layer twice, and the matching degree of the metamaterial and the free space is different according to different electromagnetic parameters, the matching problem of the metamaterial layer and the free space will also affect the wave front calibration result of the antenna, and the phase compensation error is further increased. Finally, the needed metamaterial is realized by loading the metal microstructures in the multilayer dielectric slab, and the metamaterial is complex.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a super-surface Cassegrain antenna, aiming at reducing the phase compensation error of the antenna and simplifying the structure of the antenna.
The technical scheme adopted for realizing the aim of the invention is as follows:
a cassegrain antenna based on super surface comprises a main reflector 1, a secondary reflector 2, a feed source 3 and a flat waveguide 4, wherein the main reflector 1, the secondary reflector 2 and the feed source 3 are clamped between two metal plates of the flat waveguide 4, and the cassegrain antenna comprises:
the main reflector 1 and the auxiliary reflector 2 adopt a phase mutation super-surface structure constructed based on the generalized Snell's theorem;
the main reflector 1 comprises a first dielectric layer 11, a first reflecting layer 12 printed on one side surface of the first dielectric layer 11 and a first phase regulating layer 13 on the other side surface; the first phase control layer 13 is composed of one or more rows of m first rectangular metal ring microstructures 131 which are uniformly distributed, wherein m is more than or equal to 4, the size of each first rectangular metal ring microstructure 131 is determined by the electromagnetic wave incident angle and the scattering parameter phase at the position of the first rectangular metal ring microstructure 131, and the phase compensation characteristic of a similar paraboloid to the electromagnetic wave is realized;
the secondary reflector 2 comprises a second dielectric layer 21, a second reflecting layer 22 printed on one side surface of the second dielectric layer 21 and a second phase control layer 23 on the other side surface; the second phase control layer 23 is composed of one or more rows of n second rectangular metal ring microstructures 231 which are uniformly distributed, n is greater than or equal to 4, the size of each second rectangular metal ring microstructure 231 is determined by the electromagnetic wave incident angle and the scattering parameter phase at the position of the second rectangular metal ring microstructure 231, and the hyperbolic-like phase compensation characteristic to the electromagnetic waves is realized;
the feed source 3 is positioned at the midpoint disconnection position of the main reflector 1, the second phase control layer 23 of the secondary reflector 2 is opposite to the first phase control layer 13 of the main reflector 1, the virtual focus of the secondary reflector 2 is coincided with the focus of the main reflector 1, and the real focus is coincided with the phase center of the feed source 3; the cylindrical wave emitted by the feed source 3 is reflected by the secondary reflector 2 to form a cylindrical wave taking a virtual focus of the secondary reflector 2 as a phase center, and the cylindrical wave is reflected by the primary reflector 1 to form a plane wave.
In the above cassegrain antenna based on a super surface, the phase compensation value of the position of the first rectangular metal ring microstructure 131 satisfies the following formula:
wherein phiM(xM) Representing the phase compensation value, d phi, on the main mirror 1M＝k(sinθi-sinθr)dxMRepresents phiM(xM) For xMDerivative of (a), xMRepresents the position coordinate, theta, of each first rectangular metal ring microstructure 131 in the x-axis directioni(xM)＝arctan(xM/f) is the angle of incidence of the incident electromagnetic wave with respect to the main mirror 1, θr(xM) 0 is a reflection angle of the reflected electromagnetic wave with respect to the main mirror 1, k is an electromagnetic wave propagation constant, f is a focal length of the main mirror 1, Φ0Is an arbitrary constant phase value.
In the above cassegrain antenna based on a super surface, the phase compensation value of the position of the second rectangular metal ring microstructure 231 satisfies the following formula:
wherein phiS(xS) Representing the phase compensation value, d phi, on the secondary mirror 2S＝k(sinθi-sinθr)dxSRepresents phiS(xS) For xSDerivative of (a), xSRepresents the position coordinates of each second rectangular metal ring microstructure 231 in the x-axis direction,θi(xS)＝arctan(xSl) is the angle of incidence of the incident electromagnetic wave with respect to the secondary mirror 2, θr(xS)＝arctan(xS/(f-l)) is a reflection angle of the reflected electromagnetic wave with respect to the sub-mirror 2, f is a focal length of the main mirror 1, and l is a distance between the first phase adjusting layer 13 of the main mirror 1 and the second phase adjusting layer 23 of the sub-mirror 2, and f is satisfied>l, k is the propagation constant of electromagnetic wave,. phi0Is an arbitrary constant phase value.
In the Cassegrain antenna based on the super surface, the feed source 3 adopts an H-face rectangular horn structure, the length A of the outside of the opening at the most front end along the x-axis direction and the length L of the trapezoidal opening angle part of the H-face rectangular horn along the z-axis directionhThe following formula is satisfied:
wherein d is the length of the secondary reflector 2 along the x-axis direction, and f is the focal length of the primary reflector 1.
Compared with the prior art, the invention has the following advantages:
1. according to the invention, the main reflector and the auxiliary reflector both adopt the phase mutation super-surface structure constructed based on the generalized Snell's law to realize the characterization of the electromagnetic wave phase compensation characteristic through scattering parameters, and meanwhile, the size of the rectangular metal ring microstructures on the phase control layers of the main reflector and the auxiliary reflector takes the change of the electromagnetic wave incident angle into consideration, so that the phase compensation is more accurate, compared with the existing gradient refractive index metamaterial Casseger antenna, the wavefront calibration can be more accurate, and the radiation characteristic of the antenna is optimized.
2. Compared with the metamaterial Cassegrain antenna, the main reflector and the secondary reflector which are composed of the reflecting layer, the multilayer dielectric plate and the phase control layer loaded in the middle of the multilayer dielectric plate have the characteristics of simple structure, easiness in processing and low cost.
Drawings
FIG. 1 is a schematic overall structure of a specific embodiment;
FIG. 2 is a schematic diagram of a primary mirror construction of an embodiment;
FIG. 3 is a schematic diagram of a secondary mirror configuration according to an embodiment;
FIG. 4 is a schematic diagram of an electromagnetic wave propagation path and feed source design principle of an embodiment;
FIG. 5 is a two-dimensional radiation pattern at a frequency of 15GHz for a particular embodiment, where 5(a) is an H-plane radiation pattern and 5(b) is an E-plane radiation pattern;
FIG. 6 is a graph of the xoz plane electric field strength distribution at a frequency of 15GHz in accordance with an exemplary embodiment;
Detailed Description
The invention is further described below with reference to the following figures and specific examples.
Referring to fig. 1, the present invention includes a main mirror 1, a sub-mirror 2, a feed 3, and a slab waveguide 4, and the main mirror 1, the sub-mirror 2, and the feed 3 are sandwiched between two metal plates of the slab waveguide 4. The main reflector 1 and the secondary reflector 2 are arranged in a positive feed mode, the main reflector 1 and the secondary reflector 2 are arranged in parallel, the feed source 3 is located at the midpoint disconnection position of the main reflector 1, the feed source 3 adopts an H-plane rectangular horn structure, the flat waveguide 4 is composed of two rectangular metal plates with the same size and used for limiting electromagnetic waves which do not finish phase compensation between the two metal plates of the flat waveguide, cylindrical waves emitted by the feed source 3 are reflected by the secondary reflector 2 to form cylindrical waves taking a virtual focus F2 of the secondary reflector 2 as a phase center, the virtual focus F2 of the secondary reflector 2 coincides with the focus of the main reflector 1, and the cylindrical waves are reflected by the main reflector 1 to form plane waves.
The main mirror 1 has a structure as shown in fig. 2, and includes a first dielectric layer 11, a first reflective layer 12 printed on one side of the first dielectric layer 11, and a first phase adjusting layer 13 printed on the other side. The structure of the main reflector 1 is designed under the use condition of frequency 15GHz, the first dielectric layer 11 is composed of two cuboid dielectrics with length of 139.2mm, width of 9.6mm, thickness of 1mm, dielectric constant of 4.4, magnetic permeability of 1, distance of 19.2mm in the length direction and alignment in the width direction and the thickness directionThe first dielectric layer 11 is made of materials, the length of the first dielectric layer 11 is set in a manner that a good wavefront calibration effect can be obtained only when the main reflector 1 has enough electrical size, the width of the first dielectric layer 11 is designed according to the height of a standard waveguide with the frequency of 15GHz, two-dimensional propagation of electromagnetic waves can be kept in the slab waveguide 4 only when the height of the standard waveguide and the height of the standard waveguide are close to each other, and the dielectric constant of the first dielectric layer 11 is set according to the phase compensation value change range on the main reflector 1 and the thickness of the main reflector 1 is reduced. A cartesian coordinate system is established with the center of a side surface formed by the length and the width on the first medium layer 11 as a coordinate origin, the x-axis is along the length direction of the first medium layer 11, the y-axis is along the width direction of the first medium layer 11, and the z-axis is along the thickness direction of the first medium layer 11. The variation interval of the two dielectric materials of the first dielectric layer 11 along the x axis is [ -148.8mm, -9.6mm]And [9.6mm, 148.8mm]The variation interval along the y-axis is [ -4.8mm, 4.8mm]The variation range along the z-axis is [ -1mm, 0mm]. The first reflecting layer 12 is composed of two rectangular metal plates, the length and the width of the first reflecting layer are the same as those of the first medium layer 11, the first reflecting layer is positioned on a plane with z being equal to-1 mm, and the change interval along the x axis is [ -148.8mm, -9.6mm]And [9.6mm, 148.8mm]The variation interval along the y-axis is [ -4.8mm, 4.8mm]. The first phase control layer 13 is composed of two rows of 116 first rectangular metal ring microstructures 131 uniformly distributed on the first medium layer 11, wherein the distance between the centers of the rectangular metal ring microstructures on the first phase control layer 13 in the y-axis direction is 4.8mm, the distance between the centers of the rectangular metal ring microstructures on the first phase control layer 13 in the x-axis direction is 2.4mm, the purpose of using the rectangular metal ring microstructures is to set enough rectangular metal ring microstructures in 15GHz frequency, namely 20mm of one wavelength, and a large phase compensation value change range can be realized along with the size change of the rectangular metal ring microstructures. The coordinates of the center of the rectangular metal ring microstructure along the y-axis are-2.4 mm and 2.4mm, and each x is along the x-axisMThe coordinate positions of [ -147.6mm, -145.2mm, … … -13.2mm, -10.8mm]And [10.8mm, 13.2mm … … 145.2.2 mm, 147.6mm]. The length H1, the width L1, and the line width W1 of the rectangular metal ring microstructure in the first phase adjustment layer 13 are determined by the electromagnetic wave incident angle and the scattering parameter phase at the position, and for simplicity, the length H1 of the rectangular metal ring microstructure is set to be 2 times of the width L1, which defines the perimeter of the rectangular metal ring microstructurec1 is 2 × (H1+ L1), and the four rectangular metal ring microstructures at the same position with the same absolute value of coordinate in the y-axis direction and the same absolute value of coordinate in the x-axis direction have the same electromagnetic wave incident angle and scattering parameter phase, and the four rectangular metal ring microstructures have the same size, so it is only necessary to determine that the coordinate in the y-axis direction is 2.4mm, and each x-axis direction is x-axis directionMHas a coordinate range of [10.8mm, 147.6mm ]]The perimeter c1 and the line width W1 of the inner rectangular metal ring microstructure.
The principle of action of the main mirror 1 is as shown in fig. 4, and a cylindrical wave with a certain point F1 as a phase center is converted into a plane wave to realize an electromagnetic wave phase compensation characteristic similar to a paraboloid, so that the phase compensation value of the position of the rectangular metal ring microstructure on the main mirror 1 satisfies the following formula:
wherein phiM(xM) Showing the main mirror 1 at each x-axis directionMD phi of the rectangular metal ring microstructure at the coordinate positionM＝k(sinθi-sinθr)dxMIs a generalized Snell's theorem formula, d phiMRepresents phiM(xM) To position xMDerivative of the coordinates, θi(xM)＝arctan(xM/f) is the incident angle of the incident electromagnetic wave relative to the main mirror 1, f is 150mm is the focal length of the main mirror 1, and the focal length of the main mirror 1 is along x according to the main mirror 1MLength in direction and better conversion efficiency, thetar(xM) To reflect the angle of reflection of the electromagnetic wave with respect to the main mirror 1, θ is taken because we generate a plane wave that propagates perpendicular to the main mirror 1r(xM) 0, 18 degree/mm, 15GHz electromagnetic wave propagation constant, phi0Is an arbitrary constant phase value. According to the calculated incident angle of the incident electromagnetic wave relative to the main reflector 1 and each x on the main reflector 1MPhase compensation values of rectangular metal ring microstructures at coordinate positions are established through simulation softwareThe super-surface structure comprises a dielectric substrate with the length of 4.8mm, the width of 2.4mm, the thickness of 1mm, the dielectric constant of 4.4 and the magnetic permeability of 1, a metal reflecting plate with the same length and width on one side of the dielectric substrate, and a rectangular metal ring microstructure established at the center of the other side of the dielectric substrate, wherein the boundary between the x-axis direction and the y-axis direction adopts a periodic boundary condition, the z-axis direction is an open boundary condition, a plane wave is arranged near the boundary on one side of the rectangular metal ring microstructure in the z-axis direction, the polarization mode is that an electric field is along the y-axis direction, the influence of the change of the incident angle of the electromagnetic wave on the phase compensation of the main reflector 1 is considered, therefore, the transmission direction is set according to the incident angle of the electromagnetic wave relative to the main reflector 1 at the position of the rectangular metal ring microstructure on the main reflector 1, the perimeter c1 and the line width W1 of, observing the wave port S11 parameter phase value, and representing the phase compensation value of the main mirror 1 through the S11 parameter phase, wherein the phase compensation value is independent of the specific propagation path and energy distribution of the electromagnetic wave in the main mirror 1 until the wave port S11 parameter phase value meets each x calculated by usMThe phase compensation value of the rectangular metal ring microstructure at the coordinate position can determine each x on the main reflector 1MThe circumference c1 and the line width W1 of the metal ring at the coordinate position have the following specific values;
the coordinate z of the main mirror 1 is 0mm, the coordinate y is 4.8mm, and the coordinate x is along the x-axis directionMHas a variation interval of xM∈[10.8mm，32.4mm]The number of the rectangular metal ring microstructures is 10, and the incident angle thetai4.1 °, 5.0 °, 5.9 °, 6.8 °, 7.7 °, 8.6 °, 9.5 °, 10.4 °, 11.3 °, 12.2 °, perimeter c1 is 13.2mm, 12.96mm, 12.72mm, 12.48mm, 12.24mm, 12mm, 11.88mm, 11.64mm, 11.52mm, 11.28mm, W1 is 0.3mm, 0.29mm, 0.29mm, 0.29mm, 0.29mm, 0.28mm, 0.33mm, 0.31mm, 0.34mm, 0.29mm, the scattering parameter phases achieved are-168 °, -164 °, -160 °, -155 °, -150 °, -143 °, -137 °, -129 °, -121 °, -112 °.
The coordinate z of the main mirror 1 is 0mm, the coordinate y is 4.8mm, and the coordinate x is along the x-axis directionMHas a variation interval of xM∈[34.8mm，56.2mm]Of a rectangular metal ring microstructure10, angle of incidence θi13.0 °, 13.9 °, 14.7 °, 15.6 °, 16.4 °, 17.3 °, 18.1 °, 18.9 °, 19.7 °, 20.6 °, circumference c1 is 11.16mm, 11.04mm, 10.92mm, 10.8mm, 10.68mm, 10.56mm, 10.44mm, 10.32mm, 10.2mm, 10.08mm, line width W1 is 0.29mm, 0.3mm, 0.3mm, 0.3mm, 0.29mm, 0.28mm, 0.26mm, 0.25mm, 0.25mm,0.24mm, the scattering parameter phases achieved are-103 °, 93 °, -82 °, -71 °, -58 °, -46 °, -33 °, -19 °,4 °, 9 °.
The coordinate z of the main mirror 1 is 0mm, the coordinate y is 4.8mm, and the coordinate x is along the x-axis directionMHas a variation interval of xM∈[58.8mm，80.2mm]The number of the rectangular metal ring microstructures is 10, and the incident angle thetai21.4 °, 22.2 °, 22.9 °, 23.7 °, 24.5 °, 25.2 °, 26.0 °, 26.7 °, 27.4 °, 28.1 °, circumference c1 being 9.96mm, 9.84mm, 9.6mm, 9.36mm, 9mm, 8.4mm, 6.96mm, 3.6mm, 3.6mm, 13.2mm, line width W1 being 0.27mm, 0.31mm, 0.24mm, 0.25mm, 0.3mm, 0.3mm, 0.2mm, 0.1mm, 0.1mm, 0.25mm, the phases of the scattering parameters achieved being 25 °, 41 °, 57 °, 74 °, 92 °, 110 °, 129 °, 140 °, 145 °, 171 °, respectively.
The coordinate z of the main mirror 1 is 0mm, the coordinate y is 4.8mm, and the coordinate x is along the x-axis directionMHas a variation interval of xM∈[82.8mm，104.4mm]The number of the rectangular metal ring microstructures is 10, and the incident angle thetai28.8 °, 29.5 °, 30.2 °, 30.9 °, 31.6 °, 32.2 °, 32.9 °, 33.5 °, 34.2 °, 34.8 °, circumference c1 being 12.12mm, 11.64mm, 11.16mm, 10.92mm, 10.68mm, 10.56mm, 10.44mm, 10.2mm, 10.08mm, 9.84mm, line width W1 being 0.3mm, 0.3mm, 0.28mm, 0.29mm, 0.25mm, 0.3mm, 0.33mm, 0.26mm, 0.32mm, 0.3mm, the scattering parameter phases being-150 °, 130 °, -108 °, -85 °, -64 °, -40 °, -18 °, 6 °, 30 °, 54 °, respectively.
The coordinate z of the main mirror 1 is 0mm, the coordinate y is 4.8mm, and the coordinate x is along the x-axis directionMHas a variation interval of xM∈[106.8mm，128.4mm]The number of the rectangular metal ring microstructures is 10, and the incident angle thetaiAre respectively 35.4 degrees, 36.0 degrees, 36.6 degrees and 37.2 degrees37.8 °, 38.3 °, 38.9 °, 39.4 °, 40.0 °, 40.5 °, circumference c1 of 9.48mm, 9mm, 7.68mm, 3.6mm, 13.2mm, 12.12mm, 11.4mm, 11.04mm, 10.8mm, 10.56mm, line width W1 of 0.24mm, 0.3mm, 0.3mm, 0.1mm, 0.12mm, 0.3mm, 0.29mm, 0.3mm, 0.32mm, 0.3mm, achieving scattering parameter phases of 79 °, 104 °, 130 °, 145 °, -177 °, -150 °, -123 °, 96 °, -68 °, 40 °, respectively.
The coordinate z of the main mirror 1 is 0mm, the coordinate y is 4.8mm, and the coordinate x is along the x-axis directionMHas a variation interval of xM∈[130.8mm，147.6mm]The number of the rectangular metal ring microstructures is 8, and the incident angle thetai41.0 °, 41.6 °, 42.1 °, 42.6 °, 43.1 °, 43.5 °, 44.0 °, 44.5 °, and a circumference c1 of 10.32mm, 10.2mm, 10.08mm, 9.84mm, 9.36mm, 8.28mm, 3.6mm, 12.84mm, respectively, and a line width W1 of 0.25mm, 0.33mm, 0.3mm, 0.33mm, 0.26mm, 0.3mm, 0.1mm, 0.3mm, respectively, and achieve scattering parameter phases of-12 °, 15 °, 44 °, 73 °, 103 °, 132 °, 152 °, and-167 °, respectively.
The structure of the secondary reflector 2 is shown in fig. 3, and includes a second dielectric layer 21, a second reflective layer 22 printed on the second dielectric layer 21, a second phase control layer 23 on one side surface and a second phase control layer 23 on the other side surface; the distance between the secondary reflector 2 and the primary reflector 1 is 121mm, and the secondary reflector and the primary reflector are arranged in parallel and aligned at the middle points. The structure of the secondary reflector 2 is designed under the use condition of the frequency of 15GHz, the second medium layer 21 is a cuboid medium material with the length of 57.6mm along the x-axis direction, the length of 9.6mm along the y-axis direction, the thickness of 1mm along the z-axis direction, the dielectric constant of 4.4 and the magnetic permeability of 1, and the variation range along the x-axis is [ -28.8mm, 28.8mm]The variation interval along the y-axis is [ -4.8mm, 4.8mm]The variation interval along the z-axis is [121mm, 122mm ]]The length in the x-axis direction is designed in consideration of shielding of the secondary reflector 2 on electromagnetic waves and determination of a good phase compensation effect, the width in the y-axis direction is consistent with that of the first dielectric layer 11, so that the primary reflector 1 and the secondary reflector 2 are conveniently fixed between the slab waveguides, and the thickness in the z-axis direction is consistent with that of the first dielectric layer 11, so that the processing is convenient. A second reflecting layer 22 is arranged on the side of the second medium layer 21 far away from the main reflector 1, namely the side with the z being 122mm, and the second reflecting layer 22 is a block along the x axisA rectangular metal plate having a length of 57.6mm in the direction and a length of 9.6mm in the y-axis direction is provided with the second phase control layer 23 on the side of the second medium layer 21 closer to the main mirror 1, that is, on the side of 121mm z. The second phase control layer 23 is composed of two rows of 24 second rectangular metal ring microstructures 231 uniformly distributed on the second dielectric layer 21, the distance between the centers of the rectangular metal ring microstructures is 4.8mm in the y-axis direction, the distance between the centers of the rectangular metal ring microstructures is 2.4mm in the x-axis direction, the distances are the same as the distances between the centers of the rectangular metal ring microstructures on the main reflector 1, the coordinates of the centers of the rectangular metal ring microstructures along the y-axis direction are-2.4 mm and 2.4mm, and each x-axis direction is along the x-axis directionSThe coordinate positions are [ -27.6mm, -25.2mm, … … 25.2.2 mm, 27.6mm]. The length H2, the width L2 and the line width W2 of the rectangular metal ring microstructure in the secondary reflector 2 are determined by the electromagnetic wave incident angle and the scattering parameter phase at the position, for simplicity, the length H2 of the rectangular metal ring microstructure is set to be 2 times of the width L2, the perimeter c2 of the rectangular metal ring microstructure is defined to be 2 × (H2+ L2), the absolute values of the y-axis coordinates are the same, the electromagnetic wave incident angle and the scattering parameter phase of the four rectangular metal ring microstructures at the positions with the same absolute value of the x-axis coordinates are the same, and the sizes of the four rectangular metal ring microstructures are completely the same, so that the y-axis coordinate is only required to be determined to be 2.4mm, and each x-axis coordinate in the x-SCoordinate range [1.2mm, 27.6mm]The perimeter c2 and the line width W2 of the inner rectangular metal ring microstructure.
The action principle of the secondary reflector 2 is as shown in fig. 4, and the cylindrical wave radiated from the feed source 3 is converted into the cylindrical wave with the secondary reflector 2 and a certain point F1 outside the primary reflector 1 as the phase center, so as to realize the electromagnetic wave phase compensation characteristic similar to a hyperboloid, and therefore, the phase compensation value of the position of the rectangular metal ring microstructure on the secondary reflector 2 satisfies the following formula:
wherein phiS(xS) Representing each x of the sub-mirrors 2 in the x-axis directionSD phi of the rectangular metal ring microstructure at the coordinate positionS＝k(sinθi-sinθr)dxSIs generalized SnellTheorem of formula d phiSRepresents phiS(xS) For xSDerivative of, thetai(xS)＝arctan(xS/l) is the angle of incidence of the incident electromagnetic wave with respect to the secondary mirror 2, where l 121mm is the distance between the first phase-modulating layer 13 of the primary mirror 1 and the second phase-modulating layer 23 of the secondary mirror 2, θr(xS)＝arctan(xS/(F-l)) is the reflection angle of the reflected electromagnetic wave with respect to the secondary mirror 2, F150 mm is the focal length of the primary mirror 1, which is equal to the distance from the virtual secondary mirror focus F2 to the first phase control layer 13 of the primary mirror 1, since the focal length of the primary mirror 1 coincides with the virtual secondary mirror 2, k 18 °/mm is the propagation constant of the electromagnetic wave at 15GHz, Φ0Is an arbitrary constant phase value. Based on the calculated incident angle of the incident electromagnetic wave with respect to the sub-mirror 2 and each x-axis direction on the sub-mirror 2SA phase compensation value of a rectangular metal ring microstructure at a coordinate position is obtained by establishing a super-surface structure through simulation software, wherein the center of the rectangular metal ring microstructure is positioned, the super-surface structure respectively extends up and down for 2.4mm along a y-axis direction and extends left and right for 1.2mm along an x-axis direction, the super-surface structure comprises a dielectric substrate, a metal reflecting plate and a rectangular metal ring microstructure, the dielectric substrate is 4.8mm in length, 2.4mm in width and 1mm in thickness, the dielectric constant is 4.4, the magnetic permeability is 1, the metal reflecting plate is equal to one side of the dielectric substrate in length and width, the rectangular metal ring microstructure is established at the center of the other side of the dielectric substrate, a periodic boundary condition is adopted by the boundaries between the x-axis direction and the y-axis direction, the z-axis direction is an open boundary condition, a plane wave is arranged near the boundary of one side of the rectangular metal ring microstructure in the z-axis direction, the polarization mode is that an electric field is along the y-axis Setting an incidence angle, adjusting the perimeter c2 and the line width W2 of the metal ring, observing the parameter phase value of the wave port S11, representing the phase compensation value of the secondary reflector 2 through the S11 parameter phase, and not relating to the specific propagation path and the energy distribution of the electromagnetic wave in the secondary reflector 2 until the parameter phase value of the wave port S11 meets the requirement of calculating each x-axis directionSPhase compensation value of the rectangular metal ring microstructure at the coordinate positionDetermining each x on the secondary mirror 2SThe circumference c2 and the line width W2 of the rectangular metal ring microstructure at the coordinate are as follows;
the coordinate z of the secondary reflector 2 is 121mm, the coordinate y of the secondary reflector is 2.4mm, and the coordinate x of the secondary reflector in the x-axis directionSHas a variation interval of xS∈[1.2mm，27.6mm]The number of the rectangular metal ring microstructures is 12, and the incident angle thetai0.5 °, 1.7 °, 2.8 °, 3.9 °, 5.1 °, 6.2 °, 7.3 °, 8.4 °, 9.5 °, 10.6 °, 11.7 °, 12.8 °, circumference c2 of 9.96mm, 9.96mm, 10.08mm, 10.08mm, 10.2mm, 10.32mm, 10.44mm, 10.56mm, 10.68mm, 10.92mm, 11.04mm, 11.4mm, line width W2 of 0.31mm, 0.28mm, 0.34mm, 0.27mm, 0.31mm, 0.32mm, 0.32mm, 0.31mm, 0.28mm, 0.33mm, 0.27mm, 0.31mm, implemented scattering parameters of 24 °, 22 °, 16 °,8 °, -13 °, 27 °, 43 °, -60 °, 97 °, -117 °, 117 ° -117 °.
The principle of the main reflector 1 and the secondary reflector 2 is as shown in fig. 4, the phase center F1 of the feed source 3 is located at the midpoint disconnection position of the main reflector 1, the coordinate x is 0, the coordinate z is 0, the second phase control layer 23 of the secondary reflector 2 is opposite to the first phase control layer 13 of the main reflector 1, the virtual focus of the secondary reflector 2 is coincident with the focus of the main reflector 1, the coordinate x is 0, the coordinate z is 150mm, and the real focus is coincident with the phase center of the feed source 3; the cylindrical wave emitted by the feed source 3 is reflected by the secondary reflector 2 to form a cylindrical wave with a virtual focus F2 of the secondary reflector 2 as a phase center, and the cylindrical wave is reflected by the primary reflector 1 to form a plane wave.
The H-plane rectangular horn structure adopted by the feed source 3 comprises a rectangular waveguide and a trapezoidal flare angle part, the rectangular waveguide is a standard WR62 waveguide with the internal width of 15.8mm, the height of 7.9mm and the length of 10mm, the single-mode transmission frequency range of 11.9 GHz-18.0 GHz, the rectangular waveguide has the wall thickness of 0.85mm, the length of the rectangular waveguide outside along the x-axis direction is 17.5mm, the length of the rectangular waveguide outside along the y-axis direction is 9.6mm, and the rectangular waveguide outside along the z-axis coordinate range of [ -10mm,0mm]Coordinate range on the x-axis [ -8.75mm,8.75mm]The coordinate range on the y-axis is [ -4.8,4.8 [)](ii) a The trapezoid flaring part of the H-shaped horn comprises an isosceles trapezoid metal surface which is parallel up and down and a rectangle which is flared at a certain angle left and rightThe distance of the narrow-side metal surface and the isosceles trapezoid metal surface with the trapezoid opening angle part parallel to each other up and down is 7.9mm in the y-axis direction, the thickness of the narrow-side metal surface is 0.85mm as same as that of the waveguide, and the rectangular narrow-side metal surface connects the upper isosceles trapezoid metal surface and the lower isosceles trapezoid metal surface from the waist of the isosceles trapezoid. The principle of the design of the in-plane size of the H-plane rectangular horn trapezoidal flare angle portion xoz is shown in fig. 4, and the in-plane size of the H-plane rectangular horn trapezoidal flare angle portion xoz is determined by considering the shielding of the portion on electromagnetic waves, whether the electromagnetic waves can be effectively converged on the secondary reflector 2 and the standing wave characteristics of the antenna. The electromagnetic wave is effectively converged on the secondary reflector 2, the H-face rectangular horn is required to have larger gain and smaller beam width, the trapezoidal opening angle part of the H-face rectangular horn has larger size in a xoz plane, and meanwhile, the shielding size of the secondary reflector 2 and the H-face rectangular horn trapezoidal opening angle part to the electromagnetic wave is minimized, so that the outermost edge vertex of the H-face rectangular horn trapezoidal opening angle part in a xoz plane is positioned on a virtual line, the outermost opening of the H-face rectangular horn trapezoidal opening angle part is externally positioned along the length A in the x-axis direction and the length L in the z-axis direction of the H-face rectangular horn trapezoidal opening angle part in the x-axis directionhThe following formula is satisfied:
wherein, d is 57.6mm length of the secondary reflector 2 along the x-axis direction, which is equal to the size of the shield caused by the secondary reflector on the primary reflector along the x-axis direction, and f is 150mm focal length of the primary reflector 1. Through optimization, the length of the long bottom edge of the H-surface rectangular horn trapezoid opening angle part is 48mm, the length of the short bottom edge of the X-axis direction is 17.5mm, the length of the H-surface rectangular horn opening angle part is the same as the length of the rectangular waveguide outside the X-axis direction, the length of the H-surface rectangular horn opening angle part is 25mm, and the side surfaces of the H-surface rectangular horn opening angle part are connected with the upper isosceles trapezoid metal surface and the lower isosceles trapezoid metal surface through the rectangular metal surfaces and the waists of the upper isosceles trapezoid and the lower isosceles trapezoid.
The flat waveguide 4 is composed of an upper rectangular metal plate and a lower rectangular metal plate which are the same in size, the length of each rectangular metal plate in the x-axis direction is 317.6mm, the length of each rectangular metal plate in the z-axis direction is 151mm, the left edge and the right edge cover the main reflecting surface, the x-axis coordinate range x belongs to the range of-158.8 mm and 158.8mm, the back of the auxiliary reflecting surface is extended forwards and covered by the auxiliary reflecting surface, the feed source is extended backwards and covered, the z-axis coordinate range z belongs to the range of-20 mm and 131mm, and the y-axis coordinates of the upper metal plate and the lower metal plate of the flat waveguide 4 are respectively 4.8mm and 4.8 mm.
The technical effects of the present invention will be further described in detail with reference to the results of simulation experiments.
1. Simulation conditions and contents:
electromagnetic simulation software CST 2017;
2. and (3) simulation result analysis:
referring to fig. 5, fig. 5(a) shows the variation of the gain of the H-plane with the azimuth angle of the specific embodiment at the operating frequency of 15.0GHz, and it can be seen that the maximum radiation direction is 0 °, the gain is 14.4dBi, and the half-power beam width is 3 °, which indicates that accurate phase compensation is realized in the H-plane, a large gain is realized, and a small beam width is realized in the H-plane, thereby realizing a good radiation pattern characteristic;
fig. 5(b) shows the variation of the gain of the E-plane with the azimuth angle in the specific embodiment at the operating frequency of 15.0GHz, and it can be seen that the maximum radiation direction is 0 °, the gain is 14.4dBi, the half-power beam width is 99 °, and since no phase compensation is performed on the E-plane, the E-plane beam is wider, but still achieves a larger gain, which indicates that accurate phase compensation is achieved on the H-plane, and the gain is higher;
referring to fig. 6, showing the electric field intensity distribution on the xoy plane in the specific embodiment, it can be seen that the incident wave emitted from the feed source passes through the secondary reflector 2 and the primary reflector 1 to obtain a flat plane wavefront in the propagation direction, which shows that the primary reflector 1 and the secondary reflector 2 realize accurate phase compensation and accurate wavefront calibration, and generate a flat plane wavefront;
the super-surface Cassegrain antenna provided by the invention has the advantages that the phase compensation error of the antenna is reduced, the antenna structure is simplified, the application range of the Cassegrain antenna is expanded, and the super-surface Cassegrain antenna is suitable for the fields of wireless communication, obstacle detection, air anti-collision systems and the like.
Claims (4)
1. A multisurface-based Cassegrain antenna comprising a primary mirror (1), a secondary mirror (2), a feed (3) and a slab waveguide (4), the primary mirror (1), the secondary mirror (2) and the feed (3) being clamped between two metal plates of the slab waveguide (4), wherein:
the main reflector (1) and the auxiliary reflector (2) adopt a phase mutation super-surface structure constructed based on the generalized Snell's theorem;
the main reflecting mirror (1) comprises a first dielectric layer (11), a first reflecting layer (12) printed on one side surface of the first dielectric layer (11) and a first phase regulating layer (13) on the other side surface; the first phase control layer (13) is composed of one or more rows of m first rectangular metal ring microstructures (131) which are uniformly distributed, wherein m is more than or equal to 4, the size of each first rectangular metal ring microstructure (131) is determined by the electromagnetic wave incident angle and the scattering parameter phase at the position of the first rectangular metal ring microstructure, and the electromagnetic wave phase compensation characteristic similar to a paraboloid is realized;
the secondary reflector (2) comprises a second dielectric layer (21), a second reflecting layer (22) printed on one side surface of the second dielectric layer (21) and a second phase control layer (23) on the other side surface; the second phase control layer (23) is composed of one or more rows of n second rectangular metal ring microstructures (231) which are uniformly distributed, n is more than or equal to 4, the size of each second rectangular metal ring microstructure (231) is determined by the electromagnetic wave incident angle and the scattering parameter phase at the position of the second rectangular metal ring microstructure, and the electromagnetic wave phase compensation characteristic similar to a hyperboloid is realized;
the feed source (3) is positioned at the midpoint disconnection position of the main reflector (1), the second phase control layer (23) of the secondary reflector (2) is opposite to the first phase control layer (13) of the main reflector (1), the virtual focus of the secondary reflector (2) is coincided with the focus of the main reflector (1), and the real focus is coincided with the phase center of the feed source (3); cylindrical waves emitted by the feed source (3) are reflected by the auxiliary reflector (2) to form cylindrical waves with the virtual focus of the auxiliary reflector (2) as a phase center, and the cylindrical waves are reflected by the main reflector (1) to form plane waves.
2. A hyper-surface based cassegrain antenna according to claim 1, characterized in that: the phase compensation value of the position of the first rectangular metal ring microstructure (131) satisfies the following formula:
wherein phiM(xM) Representing the phase compensation value, d phi, on the main mirror (1)M＝k(sinθi-sinθr)dxMRepresents phiM(xM) For xMDerivative of (a), xMRepresents the position coordinate theta of each first rectangular metal ring microstructure (131) in the direction of the x axisi(xM)＝arctan(xM/f) is the angle of incidence of the incident electromagnetic wave with respect to the main mirror (1), θr(xM) 0 is the reflection angle of the reflected electromagnetic wave relative to the main reflector (1), k is the propagation constant of the electromagnetic wave, f is the focal length of the main reflector (1), phi0Is an arbitrary constant phase value.
3. A hyper-surface based cassegrain antenna according to claim 1, characterized in that: the phase compensation value of the position of the second rectangular metal ring microstructure (231) satisfies the following formula:
wherein phiS(xS) Represents the phase compensation value, d phi, on the secondary mirror (2)S＝k(sinθi-sinθr)dxSRepresents phiS(xS) For xSDerivative of (a), xSRepresents the position coordinate theta of each second rectangular metal ring microstructure (231) in the x-axis directioni(xS)＝arctan(xSL) incident electromagnetic wave with respect to the secondary mirror (2)Angle thetar(xS)＝arctan(xS/(f-l)) is a reflection angle of the reflected electromagnetic wave relative to the secondary reflector (2), f is a focal length of the primary reflector (1), l is a distance between the first phase control layer (13) of the primary reflector (1) and the second phase control layer (23) of the secondary reflector (2), and f is satisfied>l, k is the propagation constant of electromagnetic wave,. phi0Is an arbitrary constant phase value.
4. A hyper-surface based cassegrain antenna according to claim 1, characterized in that: the feed source (3) adopts an H-face rectangular horn structure, the length A of the outside of the opening at the most front end of the feed source along the x-axis direction and the length L of the trapezoidal opening angle part of the H-face rectangular horn along the z-axis directionhThe following formula is satisfied:
wherein d is the length of the secondary reflector (2) along the x-axis direction, and f is the focal length of the primary reflector (1).
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| CN103956568A (en) * | 2014-05-22 | 2014-07-30 | 西安空间无线电技术研究所 | Box-shaped fan-beam antenna |
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