Dual circular polarization 3D printing multi-beam luneberg lens antenna

Abstract

The invention discloses a dual circular polarization 3D printing multi-beam Luneberg lens antenna, which adopts a 3D printing metamaterial technology and comprises a Luneberg lens and a feed antenna, the luneberg lens comprises M spherical layers which are concentrically arranged; each spherical layer comprises a plurality of units with corresponding effective refractive indexes; each unit is composed of asymmetric dielectric rods which are mutually orthogonal in the x direction, the y direction and the z direction. The Luneberg lens with the asymmetric cross structure has different responses to incident horizontal polarization and vertical polarization, so that the Luneberg lens realizes conversion from dual-linear polarization to dual-circular polarization; the feed antenna is arranged at a polarization angle of 45 degrees relative to the x axis of the Luneberg lens; the feed antenna comprises a plurality of electromagnetic dipole antenna radiation structures, and each electromagnetic dipole antenna radiation structure introduces a first feed port and a second feed port which are orthogonally arranged. By switching the corresponding feed ports, the finally generated polarization mode of left-hand circular polarization or right-hand circular polarization can be easily changed.

Description

Technical Field

[0001] The present invention belongs to the technical field of lens antennas, and in particular relates to a dual circularly polarized 3D printed multi-beam Luneburg lens antenna. Background Art

[0002] In the field of modern communication technology, the performance of the antenna system is crucial. Antennas with multiple beams, wide-angle scanning, and high gain are highly sought after. In order to meet these requirements, various types of antennas have been studied and developed, including phased array antennas, reflector antennas, and lens antennas. Phased array antennas can achieve flexible beam numbers and fast beam scanning, but they are too expensive to be used for large-scale deployment. Reflector antennas have a simple structure, but the maintenance cost is high and the mechanical positioning characteristics are unreliable. Lens antennas have the advantages of easy manufacturing, small size, and low cost. Therefore, lens antennas have been widely used in satellite communications, radar systems, and millimeter waves. Among them, the Luneburg lens is a classic lens antenna.

[0003] The existing Luneburg lenses mainly have the following processes:

[0004] Traditional hierarchical structure

[0005] This technology divides the Luneburg lens into an onion structure through various layering methods and fills each layer with different media. This technology requires multiple dielectric materials at the same time, so the cost is undoubtedly high. In addition, due to process problems, there must be gaps between layers. These gaps will cause large electromagnetic losses, which is an unfavorable factor for radiation performance. Even if the gaps can be reduced by improving the process, this will also introduce higher costs.

[0006] Flat Luneburg Lens

[0007] The flat-plate Luneburg lens achieves the function of a Luneburg lens with a gradual refractive index change by drilling holes or adding columns on the plate and utilizing the periodicity of the structure and the size change of the holes or columns. Although this technology can achieve a wide bandwidth, the bandwidth performance may still be limited compared to the spherical Luneburg lens. Moreover, due to the flat plate structure, this technology is limited to a two-dimensional plane.

[0008] 3D printed metamaterial Luneburg lens

[0009] 3D printed metamaterial Luneburg lens is a lens manufactured using 3D printing technology. This lens uses metamaterials to achieve the functions of traditional Luneburg lenses. Metamaterials are a class of artificially designed materials whose structures have special electromagnetic properties and can achieve properties that do not exist in nature. 3D printed metamaterial Luneburg lenses have the desired refractive index distribution within a specific frequency band through the precisely designed metamaterial unit structure. 3D printing technology allows the precise manufacture of these complex structures, thereby achieving complex geometries and refractive index distributions that are difficult to achieve with traditional methods. Luneburg lenses designed with this technology are often spherical, and the units use a symmetrical structure. The polarization mode of Luneburg lenses with this structure can only rely on the feed antenna. Summary of the invention

[0010] In order to solve the above problems existing in the prior art, the present invention provides a dual circularly polarized 3D printed multi-beam Luneburg lens antenna. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0011] The present invention provides a dual circularly polarized 3D printed multi-beam Luneburg lens antenna, comprising:

[0012] Luneburg lens and feeding antenna; wherein,

[0013] The Luneburg lens comprises M concentrically arranged spherical layers; wherein M is a positive integer, each spherical layer has the same thickness, and each comprises a number of units with corresponding equivalent refractive indexes; the unit is composed of dielectric rods orthogonal to each other along three directions, namely, x, y and z; the dimensions of the dielectric rods in the x and z directions are the same, the dimension of the dielectric rod in the y direction is smaller than the dimension of the dielectric rod in the x direction, and the equivalent refractive index of the corresponding unit is controlled by adjusting the dimensions of the dielectric rods in the unit; for each unit in each spherical layer, the unit is structurally connected to the surrounding adjacent units;

[0014] The feed antenna is arranged at a polarization angle of 45° relative to the x-axis of the Luneburg lens;

[0015] The feeding antenna comprises: a plurality of electromagnetic dipole antenna radiation structures, each of which introduces a first feeding port and a second feeding port which are orthogonally arranged.

[0016] In one embodiment of the present invention, the metamaterial includes a photosensitive resin.

[0017] In one embodiment of the present invention, the refractive index of each spherical layer in the Luneburg lens gradually increases from 1 to 100 along the direction from the outside of the Luneburg lens to the center of the sphere.

[0018] In one embodiment of the present invention, M is 13.

[0019] In one embodiment of the present invention, in the cell, the size of the dielectric rod along the y direction is half the size of the dielectric rod along the x and z directions.

[0020] In one embodiment of the present invention, the geometric dimensions of the length, width and height of the unit are no greater than one fifth of the wavelength of the incident electromagnetic wave.

[0021] In one embodiment of the present invention, the number of layers M of the Luneburg lens is determined based on a first formula; the first formula is as follows:

[0022]

[0023] Where N represents the number of cells through which the incident electromagnetic wave passes. represents the equivalent refractive index of the i-th unit through which the x-polarized incident electromagnetic wave passes, represents the equivalent refractive index of the ith unit through which the y-polarized incident electromagnetic wave passes, l represents the height geometric dimension of the unit, and λ0 represents the free space wavelength at 15 GHz.

[0024] In one embodiment of the present invention, an electromagnetic dipole antenna radiation structure comprises:

[0025] A metal patch radiation layer, a first dielectric layer, four metal pillars, a metal floor, a coupling gap, a second dielectric layer, a first feeding port, a third dielectric layer and a second feeding port; wherein,

[0026] The metal patch radiation layer, the first dielectric layer, the metal floor, the second dielectric layer and the third dielectric layer are stacked in sequence from top to bottom;

[0027] The metal patch radiation layer and the metal floor are connected via four vertical metal through holes penetrating the first dielectric layer;

[0028] The four metal pillars are vertically arranged in the first dielectric layer, the first ends of the four metal pillars are connected to the metal patch radiation layer, and the second ends of the four metal pillars are connected to the metal floor;

[0029] The coupling gap is set on the metal floor by etching;

[0030] The first feeding port is arranged on the upper surface of the third dielectric layer;

[0031] The second feeding port is arranged on the lower surface of the third dielectric layer.

[0032] In one embodiment of the present invention, the metal patch radiation layer includes: four metal radiation patches; wherein each metal radiation patch adopts a symmetrical slot design.

[0033] In one embodiment of the present invention, the coupling gap includes two orthogonally arranged I-shaped coupling gaps.

[0034] Beneficial effects of the present invention:

[0035] In the solution provided by the present invention, the Luneburg lens with an asymmetric cross structure has different responses to the incident horizontal polarization and vertical polarization, so that the Luneburg lens has the function of polarization conversion, and realizes the conversion from dual linear polarization to dual circular polarization; the proposed asymmetric structure is easy to process and manufacture, and the final Luneburg lens structure is stable, and the formed spherical structure avoids the disadvantages of large loss, high cost and dimensional limitation brought by the traditional layered structure and flat structure. The feeding antenna used as the feed source adopts multiple electromagnetic dipole antenna radiation structures, and each electromagnetic dipole antenna radiation structure introduces an orthogonally arranged first feeding port and a second feeding port. The polarization mode of the final left-hand circular polarization or right-hand circular polarization can be easily changed by switching the corresponding feeding port; on the basis of retaining the original high gain, broadband and low cost excellent characteristics of the traditional Luneburg lens, the function of polarization conversion is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A physical schematic diagram of a dual circularly polarized 3D printed multi-beam Luneburg lens antenna provided by an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of discretizing a Luneburg lens into a plurality of units provided in an embodiment of the present invention;

[0038] Figure 3 A schematic structural diagram of a unit in a Luneburg lens provided by an embodiment of the present invention;

[0039] Figure 4 A schematic diagram of the structure of a unit in a plane in a Luneburg lens provided by an embodiment of the present invention;

[0040] Figure 5 A schematic structural diagram of a Luneburg lens provided by an embodiment of the present invention;

[0041] Figure 6 A graph showing the relationship between the equivalent refractive index of a unit and the normalized unit size ratio in a Luneburg lens provided by an embodiment of the present invention;

[0042] Figure 7 A graph showing the relationship between the equivalent refractive index and frequency of a unit in a Luneburg lens provided by an embodiment of the present invention;

[0043] Figure 8 A simulation diagram of the axial ratios corresponding to the Luneburg lenses of different layer models provided in the embodiment of the present invention;

[0044] Fig. 9 A front view, a top view and a bottom view of a feeding antenna provided by an embodiment of the present invention;

[0045] Fig.10 A schematic diagram of an exploded structure of a feeding antenna provided by an embodiment of the present invention;

[0046] Fig.11 The simulation and test result diagrams of the reflection coefficient of a feeding antenna provided by an embodiment of the present invention with and without a lens respectively;

[0047] Fig.12 A schematic diagram of reflection coefficients of different ports and isolation between ports in a feeding antenna provided by an embodiment of the present invention;

[0048] Fig.13 A simulation diagram of a feed antenna provided by an embodiment of the present invention and a test result diagram of the axial ratio and gain in a microwave darkroom;

[0049] Fig.14 The invention provides a dual circularly polarized 3D printed multi-beam Luneburg lens antenna with left-hand circular polarization and right-hand circular polarization, and a test and simulation radiation pattern corresponding to the left-hand circular polarization and the right-hand circular polarization.

[0050] Reference numerals

[0051] 1-a first feeding port of the first electromagnetic dipole antenna radiation structure, 2-a second feeding port of the first electromagnetic dipole antenna radiation structure, 3-a first feeding port of the second electromagnetic dipole antenna radiation structure, 4-a second feeding port of the second electromagnetic dipole antenna radiation structure, 5-a first feeding port of the third electromagnetic dipole antenna radiation structure, 6-a second feeding port of the third electromagnetic dipole antenna radiation structure, 7-a first feeding port of the fourth electromagnetic dipole antenna radiation structure, 8-a second feeding port of the fourth electromagnetic dipole antenna radiation structure, 9-a first feeding port of the fifth electromagnetic dipole antenna radiation structure, 10-a second feeding port of the fifth electromagnetic dipole antenna radiation structure, 11-a metal patch radiation layer, 12-a first dielectric layer, 13-four metal pillars, 14-a metal floor, 15-a coupling gap, 16-a second dielectric layer, 17-a third dielectric layer, 18-a first feeding port, 19-a second feeding port. DETAILED DESCRIPTION

[0052] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0053] The embodiment of the present invention provides a dual circularly polarized 3D printed multi-beam Luneburg lens antenna, such as Figure 1As shown, 3D printing metamaterial technology is used, including:

[0054] Luneburg lens and feeding antenna; wherein,

[0055] The Luneburg lens comprises M concentrically arranged spherical layers; wherein M is a positive integer, each spherical layer has the same thickness and comprises a number of units with corresponding equivalent refractive indexes; the unit is composed of dielectric rods orthogonal to each other along three directions, namely, x, y and z; the sizes of the dielectric rods in the x and z directions are the same, the size of the dielectric rod in the y direction is smaller than the size of the dielectric rod in the x direction, and the equivalent refractive index of the corresponding unit is controlled by adjusting the size of the dielectric rod in the unit; for each unit in each spherical layer, the unit is structurally connected to the surrounding adjacent units;

[0056] The feed antenna is arranged at a polarization angle of 45° relative to the x-axis of the Luneburg lens;

[0057] The feed antenna may include: a plurality of electromagnetic dipole antenna radiating structures, each of which introduces a first feed port and a second feed port that are orthogonally arranged.

[0058] The dual circularly polarized 3D printed multi-beam Luneburg lens antenna proposed in the embodiment of the present invention may specifically include: a feeding antenna consisting of a novel spherical dual circularly polarized Luneburg lens with polarization conversion function and a dual linearly polarized electromagnetic dipole patch antenna.

[0059] Specifically, the metamaterial may include a photosensitive resin.

[0060] Advances in 3D printing technology have provided a cost-effective method for manufacturing complex three-dimensional structures. The technology has been widely used in the production of metamaterials, especially in the development of metamaterial Luneburg lenses. Luneburg lenses are manufactured by discretizing the Luneburg lenses into small units, filling these units with 3D printed metamaterial structures, and modifying the medium filling rate of these units to control the equivalent refractive index. This method can accurately control the refractive index at different positions of the lens, approximating a continuously changing refractive index.

[0061] For ease of understanding, the Luneburg lens and the feeding antenna in the dual circularly polarized 3D printed multi-beam Luneburg lens antenna provided in an embodiment of the present invention are specifically introduced below.

[0062] Luneburg lens

[0063] Luneburg lens, such as Figure 2As shown, it can include M concentrically arranged spherical layers; wherein M is a positive integer, each spherical layer has the same thickness, and includes a number of units with corresponding equivalent refractive indexes; the unit is composed of asymmetric dielectric rods that are orthogonal to each other along the three directions of x, y, and z; the equivalent refractive index of the corresponding unit is controlled by adjusting the size of the dielectric rods in the unit; for each unit in each spherical layer, the unit is structurally connected to the surrounding adjacent units.

[0064] In the Luneburg lens, its equivalent refractive index distribution satisfies the following formula:

[0065]

[0066] Where r is the normalized radius and n is the equivalent refractive index.

[0067] Specifically, the refractive index of each spherical layer in the Luneburg lens gradually increases from 1 to

[0068] To achieve gradient refractive index, the spherical Luneburg lens is discretized into concentric spherical layers of equal thickness. Each layer is then discretized into smaller units, such as Figure 2 As shown in . However, as the number of Luneburg lens layers increases, the improvement of its radiation characteristics becomes less significant. Therefore, taking various factors into consideration, the Luneburg lens in the embodiment of the present invention is constructed as a 13-layer structure, that is, M is 13, and each layer is filled with units with corresponding equivalent refractive index.

[0069] For a schematic diagram of the structure of a unit in a Luneburg lens, see Figure 3 As shown, the geometric dimensions of the length, width and height of the unit are no greater than one-fifth of the wavelength of the incident electromagnetic wave. The geometric dimensions of the length, width and height of the unit can be set to 4mm×4mm×4mm, which is one-fifth of the 15GHz vacuum wavelength, thereby ensuring that the equivalent medium theory is valid. Each unit can be composed of three mutually orthogonal dielectric rods, and the equivalent refractive index can be controlled by adjusting the size of the dielectric rods. In the unit, the size of the dielectric rod along the y direction is half the size of the dielectric rod along the x and z directions. Corresponding to Figure 3 In the figure, it can be seen that the size of the dielectric rod in the x and z directions of the unit is a, and the size of the dielectric rod in the y direction is a / 2. By changing the structure of the dielectric rod in the unit, the unit has different responses to horizontal and vertical polarization, thereby realizing the polarization conversion function of the entire Luneburg lens. For a schematic diagram of the structure of a Luneburg lens composed of several units, please refer to Figure 4 and Figure 5 Specifically, Figure 4 This is a schematic diagram of the structure of the unit in the plane formed by the x-direction and the y-direction in the Luneburg lens. Figure 5The schematic diagram of the structure of the Luneburg lens composed of all units. The Luneburg lens adopts a cross structure, and each unit inside is structurally connected to the six adjacent units around it. Therefore, the Luneburg lens proposed in the embodiment of the present invention is more stable in structure and does not require an additional support structure.

[0070] By using electromagnetic waves of different polarizations to be incident on the unit, the parameter S is obtained. It can be understood that the parameter S represents the scattering parameter, which is an important parameter in microwave transmission and is used to describe the frequency domain characteristics of the transmission channel. From the parameter S, the equivalent refractive index n at x-polarization and y-polarization incidence can be derived. x and n y For a plot of the relationship between the equivalent refractive index of a cell and the normalized cell size ratio, see Figure 6 . Where k represents the normalized unit size ratio, k is the ratio of the size a of the dielectric rod in the unit to the unit size l, k = a / l. Figure 6 As can be seen from the figure, by changing the unit size within the achievable range, the equivalent refractive index can be changed from 1 to For a diagram showing the relationship between the equivalent refractive index of a unit in a Luneburg lens provided by an embodiment of the present invention and the frequency, see Figure 7 .from Figure 7 It can be seen that the unit has frequency-independent characteristics.

[0071] It can be understood that two orthogonal linear polarization waves of the same size and a phase difference of 90° can be synthesized into a circularly polarized wave. Therefore, using a linear polarization antenna with a polarization angle of 45° to the x-axis as a feed source, the slanted 45° linear polarization can be decomposed into mutually perpendicular x-polarization and y-polarization. When two polarized electromagnetic waves pass through a unit, they will produce different phase shifts because the unit has different equivalent refractive indices for different polarizations. and Phase Shift and The phase difference between Determined by the following formula:

[0072]

[0073] Where λ0 represents the free space wavelength at 15 GHz, and l represents the size of the unit. When the total size of the unit is determined, it can be seen that the phase difference It is determined by the unit equivalent refractive index difference. Therefore, it is only necessary to control the two polarized electromagnetic waves to produce a 90° phase difference when passing through the entire Luneburg lens to achieve the conversion of linear polarization waves to circular polarization waves. The total phase difference is It can be calculated by the following formula:

[0074]

[0075] Where N represents the number of cells through which the incident electromagnetic wave passes. represents the equivalent refractive index of the i-th unit through which the x-polarized incident electromagnetic wave passes, represents the equivalent refractive index of the ith unit through which the y-polarized incident electromagnetic wave passes, l represents the height geometric dimension of the unit, and λ0 represents the free space wavelength at 15 GHz.

[0076] Therefore, the number of layers M of the Luneburg lens is determined based on the first formula; the first formula is as follows:

[0077]

[0078] Where N represents the number of cells through which the incident electromagnetic wave passes. represents the equivalent refractive index of the i-th unit through which the x-polarized incident electromagnetic wave passes, represents the equivalent refractive index of the ith unit through which the y-polarized incident electromagnetic wave passes, l represents the geometric size of the unit, and λ0 represents the free space wavelength at 15 GHz.

[0079] It can be understood that the unit equivalent refractive index is determined by the unit. After the geometric size l of the unit is determined, different equivalent refractive indices can be obtained by changing the size of the dielectric rod in the unit, thereby determining and In the first formula, l and λ0 are also fixed values. There is only one unknown quantity N in the first formula. By changing the number of layers M, different N can be obtained to make the first formula valid, that is, the value on the left side of the equation is 90°. At this time, the corresponding M value is the optimal number of layers. The total phase difference of different layers can be calculated, as shown in Table 1.

[0080] Table 1 Total phase difference of different layers

[0081] Number of layers 11 12 13 14 Total phase difference 83.5° 92.9° 100° 107.6°

[0082] In order to verify the calculation results, the embodiment of the present invention establishes Luneburg lenses of different layer models, and uses a dipole antenna rotated 45° relative to the Luneburg lens as a feed source. For the simulation diagram of the axial ratio corresponding to the Luneburg lenses of different layer models provided by the embodiment of the present invention, please refer to Figure 8 . Figure 8 The simulated axial ratio values ​​are shown in . It can be seen that the 13-layer Luneburg lens has a better 3 dB axial ratio bandwidth in the Ku band, so the embodiment of the present invention selects the 13-layer Luneburg lens for further research.

[0083] Feed antenna

[0084] In order to provide two linearly polarized waves, the embodiment of the present invention designs a dual-polarized electromagnetic dipole antenna as a feeding antenna.

[0085] The feed antenna is arranged at a polarization angle of 45° relative to the x-axis of the Luneburg lens;

[0086] The feeding antenna comprises: a plurality of electromagnetic dipole antenna radiation structures, each of which introduces a first feeding port and a second feeding port which are orthogonally arranged.

[0087] The front view, top view and bottom view of a feeding antenna provided by an embodiment of the present invention are shown in FIG. Fig. 9 , the exploded diagram of the feed antenna structure, see Fig.10 The following will combine Fig. 9 and Fig.10 The structure of the feed antenna is introduced.

[0088] Fig. 9 The upper part of the figure shows the front view of the feed antenna, the middle part shows the top view of the feed antenna, and the lower part shows the bottom view of the feed antenna. The feed antenna provided in the embodiment of the present invention adopts an electromagnetic dipole antenna radiation structure with a patch loaded symmetrically etched gap.

[0089] Specifically, the electromagnetic dipole antenna radiation structure, such as Fig.10 As shown, it may include:

[0090] Metal patch radiation layer 11, first dielectric layer 12, four metal pillars 13, metal floor 14, coupling gap 15, second dielectric layer 16, first feeding port 18, third dielectric layer 17 and second feeding port 19; wherein,

[0091] The metal patch radiation layer 11, the first dielectric layer 12, the metal floor 14, the second dielectric layer 16 and the third dielectric layer 17 are stacked in sequence from top to bottom;

[0092] The metal patch radiation layer 11 and the metal floor 14 are connected through four vertical metal through holes penetrating the first dielectric layer 12;

[0093] Four metal pillars 13 are vertically arranged in the first dielectric layer 12, the first ends of the four metal pillars 13 are connected to the metal patch radiation layer 11, and the second ends are connected to the metal floor 14;

[0094] The coupling gap 15 is set on the metal floor 14 by etching;

[0095] The first feeding port 18 is disposed on the upper surface of the third dielectric layer 17;

[0096] The second feeding port 19 is disposed on the lower surface of the third dielectric layer 17 .

[0097] Understandably, from Fig. 9 The top view and Fig.10 It can be seen that the metal patch radiation layer 11 may include: four metal radiation patches; wherein each metal radiation patch adopts a symmetrical slot design. The four metal radiation patches realize an electric dipole, and a symmetrical slot design as shown in the figure is adopted on the four metal radiation patches to generate a radiation gap between the patches, and a magnetic dipole is realized by utilizing the radiation gap, thereby realizing an electromagnetic dipole. Each metal radiation patch has the same width and is a quarter wavelength, thereby forming two pairs of half-wave dipoles. Since the magnetic dipole is not composed of a traditional vertical short-circuited metal column with a quarter wavelength height, the height of the electromagnetic dipole antenna radiation structure is not limited to 0.25λ c , can be as low as 0.16λ c ,λ c The electromagnetic dipole in the embodiment of the present invention has four symmetrical gaps etched on the inner edges of four metal radiation patches to expand the relative impedance bandwidth of the antenna.

[0098] The coupling slot 15 may include two orthogonally arranged I-shaped coupling slots.

[0099] The embodiment of the present invention adopts a microstrip slot coupling feeding method to excite the radiation part of the upper electromagnetic dipole. The metal floor 14 provided by the embodiment of the present invention is etched with mutually orthogonal "I"-shaped coupling gaps, which can achieve greater energy coupling in a relatively small size compared to rectangular gaps.

[0100] A physical schematic diagram of a multi-beam Luneburg lens antenna provided in an embodiment of the present invention is shown in FIG. Figure 1 As shown, it can be seen that five feeding antennas are supported by a bracket, covering the Luneburg lens by ±60°. The feeding antenna is rotated 45° relative to the Luneburg lens to generate two ±45° linearly polarized waves. The multi-beam Luneburg lens antenna has ten feeding ports, and each electromagnetic dipole antenna radiation structure includes two feeding ports, from the first feeding port 3 of the second electromagnetic dipole antenna radiation structure to the second feeding port 6 of the third electromagnetic dipole antenna radiation structure and from the first feeding port 7 of the fourth electromagnetic dipole antenna radiation structure to the second feeding port 10 of the fifth electromagnetic dipole antenna radiation structure, having a symmetrical structure. For ease of analysis, the first feeding port 1 of the first electromagnetic dipole antenna radiation structure to the second feeding port 6 of the third electromagnetic dipole antenna radiation structure will be analyzed below.

[0101] The impedance characteristic test was performed using a vector grid analyzer. The simulation and test results of the reflection coefficient of the feed antenna with and without a lens are shown in the figure. Fig.11 .from Fig.11It can be seen that the presence of the lens has no significant effect on the impedance matching of the feed antenna. In the range of less than -10dB, the relative bandwidth exceeds 33.7%, almost covering the entire Ku-band.

[0102] Schematic diagram of reflection coefficients of different ports in the feed antenna and isolation between ports, such as Fig.12 As shown, from Fig.12 It can be seen that in the Ku-band, the coupling between different ports of the feed antenna is less than -18.5dB.

[0103] The simulation of the feed antenna and the test results of the axial ratio and gain in the microwave darkroom are shown in the figure. Fig.13 As shown in the figure, the axial ratio and gain are measured in a microwave darkroom. Within the operating frequency range, the axial ratio is less than 3dB. The gain of the feed antenna is about 7dBi. After adding the Luneburg lens, the gain reaches about 21dBi. It can be seen that the Luneburg lens increases the gain of the feed antenna by 14dB, showing good radiation performance.

[0104] The test and simulation radiation patterns corresponding to left-hand circular polarization and right-hand circular polarization of a dual circularly polarized 3D printed multi-beam Luneburg lens antenna provided in an embodiment of the present invention are shown in Fig.14 ; It can be seen Fig.14 In the figure, the images corresponding to (a), (b) and (c) are the test and simulation radiation patterns corresponding to left-hand circular polarization, and the images corresponding to (d), (e) and (f) are the test and simulation radiation patterns corresponding to right-hand circular polarization. There are 5 beams in the figure covering a spatial range of ±60°. It can be understood that the wave obtained from the first feeding port of all electromagnetic dipole antenna radiation structures is a left-hand circular polarization wave (LHCP), and the wave obtained from the second feeding port of all electromagnetic dipole antenna radiation structures is a right-hand circular polarization wave (RHCP). The change of left-hand circular polarization and right-hand circular polarization mode only requires switching the feeding port corresponding to the feeding antenna, without the need for mechanical operation. From Fig.14 It can be seen that the simulation results are consistent with the measurement results. It can be seen that the Luneburg lens provided in the embodiment of the present invention improves the gain of the feed antenna by 14 dB, has an excellent gain improvement effect, and the gain consistency of each beam is good, and the gain from different angles is almost the same.

[0105] The feeding antenna provided in the embodiment of the present invention uses a dual-polarized electromagnetic dipole patch antenna as a feed source, and the resulting polarization mode of left-hand circular polarization or right-hand circular polarization can be easily changed by simply cutting off the feeding port of the feeding antenna instead of mechanically rotating it.

[0106] From the results of simulation and testing, the multi-beam Luneburg lens antenna provided by the embodiment of the present invention adopts an asymmetric cross-structured Luneburg lens, which has different responses to the incident horizontal polarization and vertical polarization, so that the Luneburg lens has the function of polarization conversion, and realizes the conversion from dual linear polarization to dual circular polarization; the proposed asymmetric structure is easy to process and manufacture, and the final Luneburg lens structure is stable, and the formed spherical structure avoids the disadvantages of large loss, high cost and dimensional limitation brought by the traditional layered structure and flat structure. The feed antenna as the feed source adopts multiple electromagnetic dipole antenna radiation structures, each of which introduces an orthogonally arranged first feed port and second feed port. By simply switching the corresponding feed port, the polarization mode of the final left-hand circular polarization or right-hand circular polarization can be easily changed; on the basis of retaining the original high gain, broadband and low cost excellent characteristics of the traditional Luneburg lens, the function of polarization conversion is realized.

[0107] It should be noted that in the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A dual circularly polarized 3D printed multi-beam Luneburg lens antenna, using 3D printing metamaterial technology, It is characterized in that include: Luneburg lens and feeding antenna; wherein, The Luneburg lens comprises M concentrically arranged spherical layers; wherein M is a positive integer, each spherical layer has the same thickness, and each comprises a number of units with corresponding equivalent refractive indexes; the unit is composed of dielectric rods orthogonal to each other along three directions, namely, x, y and z; the dimensions of the dielectric rods in the x and z directions are the same, the dimension of the dielectric rod in the y direction is smaller than the dimension of the dielectric rod in the x direction, and the equivalent refractive index of the corresponding unit is controlled by adjusting the dimensions of the dielectric rods in the unit; for each unit in each spherical layer, the unit is structurally connected to the surrounding adjacent units; The feed antenna is arranged at a polarization angle of 45° relative to the x-axis of the Luneburg lens; The feeding antenna comprises: a plurality of electromagnetic dipole antenna radiation structures, each of which introduces a first feeding port and a second feeding port which are orthogonally arranged.

2. A dual circularly polarized 3D printed multi-beam Luneburg lens antenna according to claim 1, It is characterized in that The metamaterial includes a photosensitive resin.

3. A dual circularly polarized 3D printed multi-beam Luneburg lens antenna according to claim 1, It is characterized in that The refractive index of each spherical layer in the Luneburg lens gradually increases from 1 to 1 along the direction from the outside of the Luneburg lens to the center of the sphere.

4. A dual circularly polarized 3D printed multi-beam Luneburg lens antenna according to claim 1, It is characterized in that M is 13.

5. The dual circularly polarized 3D printed multi-beam Luneburg lens antenna according to claim 1, It is characterized in that In the unit, the size of the dielectric rod along the y direction is half of the size of the dielectric rod along the x and z directions.

6. A dual circularly polarized 3D printed multi-beam Luneburg lens antenna according to claim 1, It is characterized in that The geometric dimensions of the length, width and height of the unit are no greater than one fifth of the wavelength of the incident electromagnetic wave.

7. The dual circularly polarized 3D printed multi-beam Luneburg lens antenna according to claim 1, It is characterized in that The number of layers M of the Luneburg lens is determined based on a first formula; the first formula is as follows: Where N represents the number of cells through which the incident electromagnetic wave passes. represents the equivalent refractive index of the i-th unit through which the x-polarized incident electromagnetic wave passes, represents the equivalent refractive index of the ith unit through which the y-polarized incident electromagnetic wave passes, l represents the height geometric dimension of the unit, λ 0 represents the free space wavelength at 15 GHz.

8. The dual circularly polarized 3D printed multi-beam Luneburg lens antenna according to claim 1, It is characterized in that The electromagnetic dipole antenna radiation structure comprises: A metal patch radiation layer (11), a first dielectric layer (12), four metal pillars (13), a metal floor (14), a coupling gap (15), a second dielectric layer (16), a first feeding port (18), a third dielectric layer (17) and a second feeding port (19); wherein, The metal patch radiation layer (11), the first dielectric layer (12), the metal floor (14), the second dielectric layer (16) and the third dielectric layer (17) are stacked in sequence from top to bottom; The metal patch radiation layer (11) and the metal floor (14) are connected via four vertical metal through holes penetrating the first dielectric layer (12); The four metal pillars (13) are vertically arranged in the first dielectric layer (12), the first ends of the four metal pillars (13) are connected to the metal patch radiation layer (11), and the second ends are connected to the metal floor (14); The coupling gap (15) is arranged on the metal floor (14) by etching; The first feeding port (18) is arranged on the upper surface of the third dielectric layer (17); The second feeding port (19) is arranged on the lower surface of the third dielectric layer (17).

9. The dual circularly polarized 3D printed multi-beam Luneburg lens antenna according to claim 8, It is characterized in that The metal patch radiation layer (11) comprises: four metal radiation patches; wherein each metal radiation patch adopts a symmetrical slot design.

10. The dual circularly polarized 3D printed multi-beam Luneburg lens antenna according to claim 8, It is characterized in that The coupling gap (15) comprises two orthogonally arranged I-shaped coupling gaps.

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