Broadband circularly polarized wide-angle beam scanning antenna device based on truncated luneberg lens

Abstract

The invention belongs to the technical field of wireless communication, and discloses a broadband circularly polarized wide-angle beam scanning antenna device based on a truncated Luneberg lens. Comprising a truncated Luneberg lens and an equiangular-Archimedes composite spiral feed source, the feed source adopts an equiangular spiral antenna at a high frequency and adopts an Archimedes spiral antenna at a low frequency, and 80% of relative bandwidth and good circular polarization characteristics are realized. The truncated luneberg lens is manufactured through a 3D printing process and is adaptive to a frequency band of 1.5-3.5 GHz, the truncated depth is 0.6 times of the radius to form a flat focal plane, and the refractive index gradient is 1.17-2.77. The flat focal plane is designed based on the Hamiltonian optical theory and supports feed source linear displacement to achieve + / -43-degree circular polarization wide-angle beam scanning. And the refractive index change is realized by the metamaterial structure units filled with the photosensitive resin by air in a layering manner. According to the invention, Hamiltonian optics, 3D printing and composite helical antenna technologies are integrated, and the antenna has broadband characteristics, high gain, low gain fluctuation and wide-angle scanning capability, and is suitable for various broadband wave beam scanning scenes.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, and more specifically, relates to a broadband circularly polarized wide-angle beam scanning antenna device based on a truncated Luneburg lens. Background Technology

[0002] Lens antennas are advanced radio frequency devices. Compared to many microwave lenses (such as Eaton lenses and Maxwell fisheye lenses), Luneburg lenses have the ability to convert spherical waves into plane waves. Furthermore, due to their high gain, low loss, and multi-beam scanning capabilities, they show great potential in communication and radar systems. In addition, compared to phased array antennas and reflector antennas, Luneburg lens antennas do not suffer from efficiency losses or increased costs due to complex feeding networks.

[0003] Circularly polarized antennas occupy a dominant or even irreplaceable position in fields such as satellite communications, spacecraft, weather radar, radio frequency identification, synthetic aperture radar, drones, mobile communications, biomedical applications, and wireless power transmission, while such designs have not yet been fully explored in Luneburg lenses.

[0004] Traditional Luneburg lenses have a spherical focal plane, making them inconvenient to integrate with planar feed systems. Therefore, existing technologies employ transformation optics (TO) and quasi-conformal transformation optics (QCTO) to improve the shape of Luneburg lenses. However, such improvements often come with performance degradation, especially a reduction in scanning angle and an increase in gain ripple.

[0005] Because the larger size of low-frequency devices complicates manufacturing, existing Luneburg lens antennas are mostly focused on the high-frequency band, and their relative bandwidth is generally narrow due to the limitation of feed bandwidth.

[0006] Based on existing technologies, this invention innovatively proposes a truncated Luneburg lens antenna system based on Hamiltonian optics theory, featuring low-frequency broadband, circularly polarized wide-angle scanning, and single-material large-size 3D printing technology, enabling high-gain communication support for different frequency bands and different objects. Summary of the Invention

[0007] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a broadband circularly polarized wide-angle beam scanning antenna device based on a truncated Luneburg lens. The purpose is to propose an antenna based on Hamiltonian optics theory, featuring low-frequency broadband, circularly polarized wide-angle scanning, and single-material large-size 3D printing technology, to achieve high-gain communication support for different frequency bands and different objects.

[0008] To achieve the above objectives, this invention provides a broadband circularly polarized wide-angle beam scanning antenna device based on a truncated Luneburg lens, employing 3D printing metamaterial technology. It includes a truncated Luneburg lens and an isoangular-Archimedean composite spiral feed. The isoangular-Archimedean composite spiral feed is positioned at the center of the lower surface of the truncated Luneburg lens, at a predetermined distance from the lower surface. The isoangular-Archimedean composite spiral feed uses an isoangular spiral antenna at high frequencies (1.5-3.5 GHz) and an Archimedean spiral antenna at low frequencies, combining the advantages of both spiral antennas to achieve… With a relative bandwidth of 80% and good circular polarization characteristics, the truncated Luneburg lens is manufactured using large-scale 3D printing technology to meet the size requirements of the 1.5-3.5GHz frequency band. The truncation depth is less than its own radius to form a flat focal plane with a gradient refractive index change from 1.17 to 2.77 from the edge to the center of the sphere. The flat focal plane is realized by Hamiltonian optics theory and supports ±43° circular polarization wide-angle beam scanning by linear displacement of the feed source. The flat focal plane is the concentric spherical surface of the lens, and the gradient refractive index change is achieved by a layered design of metamaterial structural units of air-filled photosensitive resin.

[0009] Furthermore, the composite helical antenna consists of three parts: an antenna radiating element, a feeding balun, and a reflective back cavity. The balanced output terminal at the top of the feeding balun is connected to the two feeding points of the antenna radiating element. The reflective back cavity is located below the antenna radiating element and is connected to the grounding part of the feeding balun. Together, they provide the antenna with backward electromagnetic wave reflection to achieve unidirectional radiation.

[0010] Furthermore, the antenna radiating element includes a PTFE dielectric substrate, an Archimedean spiral, an equiangular spiral, and a resistor. The Archimedean spiral is used at low frequencies, and the equiangular spiral is used at high frequencies, with the two effectively connected. The resistor helps reduce the reflected current at the ends of the spiral arms.

[0011] Furthermore, the feed balun is mainly used to convert unbalanced feeds to achieve balanced feeds. The radiating element of the composite spiral antenna is a symmetrical balanced structure, and in practical applications, it is usually fed by a coaxial line. However, the impedance of the coaxial line is inconsistent with the input impedance of the composite spiral antenna, so a feed balun is added for impedance matching.

[0012] Furthermore, the reflective back cavity is mainly used to address the loss of gain and efficiency and the large back lobe caused by the bidirectional radiation characteristics of the composite helical antenna.

[0013] Furthermore, the truncated Luneburg lens first uses Hamiltonian optics theory to move the focal surface from the outer surface to the interior, and obtains the dielectric constant distribution. The focal surface is a concentric spherical surface of the lens, and its radius is smaller than the radius of the lens itself.

[0014] Furthermore, since the dielectric constant distribution is continuous, and no material in nature satisfies this condition, the dielectric constant of the truncated Luneburg lens is discretized by layering the layers with equal thickness to obtain the dielectric constant of each layer.

[0015] Furthermore, the dielectric constant of each layer can be achieved by changing the duty cycle of the metamaterial structure. The truncated Luneburg lens comprises M concentrically arranged spherical layers; where M is a positive integer, each spherical layer has the same thickness, and each includes several metamaterial structural units with corresponding equivalent dielectric constants. Each metamaterial structural unit is connected to its surrounding adjacent metamaterial structural units. The structure of the metamaterial structural unit is preferably based on photosensitive resin, and is cubic in shape with an air column in the center. The air column has the same dimensions in the x and y directions, that is, it is a square with a side length smaller than the side length of the metamaterial in the xy section, and its dimension in the z direction is equal to the side length of the metamaterial. By changing the size of the air column (i.e., the duty cycle), the effective dielectric constant of the metamaterial structural unit can be changed.

[0016] Furthermore, the side length of the metamaterial is less than one-eighth of the wavelength corresponding to the center frequency.

[0017] Furthermore, the truncated Luneburg lens is modeled and simulated in CST software. The Luneburg lens is illuminated with a parallel wave, and the spatial energy flux density is observed to determine the distance between the feed source and the lower surface of the lens.

[0018] Furthermore, the truncated Luneburg lens is fabricated by 3D printing, and its fabrication process includes the following steps: First, a model is designed and the structure is optimized using CAD software (such as adding supports and adjusting details), and printing files are generated layer by layer using slicing software; then, a suitable resin is selected and the equipment is calibrated, the resin tank is injected and printing is started, and ultraviolet light cures the resin layer by layer according to the slicing data, and the platform is repeatedly raised and lowered to complete the stacking; after printing, the model needs to be cleaned to remove uncured resin, the supports are cut off and a second UV curing is performed to enhance performance, and finally the surface is optimized by grinding or spraying.

[0019] In summary, compared with the prior art, the broadband circularly polarized wide-angle beam scanning antenna device based on a truncated Luneburg lens provided by the present invention has the following advantages: 1. Wideband performance: This antenna device covers the 1.5-3.5 GHz frequency band and has an 80% relative bandwidth achieved through an equiangular-Archimedes composite spiral feed, which is significantly better than the narrow bandwidth limitation of traditional Luneburg lens antennas and is suitable for multi-band communication needs.

[0020] 2. Wide-angle beam scanning and stable circular polarization: Supports wide-angle beam scanning of ±43°, with gain fluctuation of less than 1.46 dBi and axial ratio always below 3 dB during scanning, ensuring stable circular polarization radiation performance across the entire frequency band, suitable for satellite communication and other scenarios.

[0021] 3. Single-material 3D printing technology: Using large-size 3D printing (498mm×498mm×398.4mm) and air-filled metamaterial structural units, a gradient dielectric constant (1.17-2.77) is achieved, eliminating the need for complex multi-layer stacking, simplifying the manufacturing process, and ensuring high precision and structural compactness. Attached Figure Description

[0022] Figure 1 The physical and simulation schematic diagrams of a broadband circularly polarized wide-angle beam scanning antenna device based on a truncated Luneburg lens provided in the embodiments of the present invention; Figure 2 This is a schematic diagram of the focal point distribution of a truncated Luneburg lens at different truncation depths, provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the metamaterial structural unit in a truncated Luneburg lens provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a truncated Luneburg lens composed of metamaterial structural units, provided in an embodiment of the present invention. Figure 5 The graph shows the relationship between the equivalent dielectric constant of a metamaterial structural unit in a truncated Luneburg lens and the size ratio of the air column within the unit, as provided in an embodiment of the present invention. Figure 6 A graph showing the relationship between the equivalent dielectric constant and frequency of a metamaterial structural unit in a truncated Luneburg lens provided in an embodiment of the present invention. Figure 7 These are front and top views of an isoangular-Archimedean composite spiral feed antenna provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of an isoangular-Archimedean composite spiral feed antenna provided in an embodiment of the present invention. Figure 9 Figures showing the axial ratio simulation and test results in a microwave anechoic chamber for an embodiment of the present invention; Figure 10 The simulation diagram and gain comparison diagram at different cut-off depths of the wideband circularly polarized wide-angle beam scanning antenna device provided in the embodiments of the present invention are shown. Figure 11The simulation results and test results in a microwave anechoic chamber for the axial ratio and gain of the broadband circularly polarized wide-angle beam scanning antenna device provided in the embodiments of the present invention are shown in the figure. Figure 12 This is a simulated radiation pattern of the broadband circularly polarized wide-angle beam scanning antenna device provided in an embodiment of the present invention; Figure 13 The radiation pattern of the broadband circularly polarized wide-angle beam scanning antenna device provided in the embodiment of the present invention is shown in the test radiation pattern.

[0023] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-Dielectric substrate, 2-Archimedean spiral, 3-Equiangular spiral, 4-Resistor, 5-Reflective back cavity, 6-Feed balun, 7-Feed port. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0025] This invention provides a broadband circularly polarized wide-angle beam scanning antenna device based on a truncated Luneburg lens, such as... Figure 1 As shown, 3D printing metamaterial technology is used, including: A truncated Luneburg lens and an isoangular-Archimedean composite spiral feed; among which... The truncated Luneburg lens comprises M concentrically arranged spherical layers, where M is a positive integer. Each spherical layer has the same thickness and includes several metamaterial structural units with corresponding equivalent dielectric constants. Each unit is composed of photosensitive resin filled with air columns. The photosensitive resin is cubic with a side length less than one-eighth of the fixed value corresponding to the wavelength of the center frequency. The air columns have the same dimensions in the x and y directions, i.e., they form squares with side lengths smaller than the side lengths of the photosensitive resin in the xy section, and their dimensions in the z direction are equal to the side lengths of the photosensitive resin. The equivalent dielectric constant of the corresponding unit is controlled by adjusting the side lengths of the air columns in the unit. For each unit in each spherical layer, the unit is structurally connected to the surrounding adjacent units. The equiangular-Archimedes composite spiral feed is placed at the center of the lower surface of the truncated Luneburg lens, at a distance of 3mm from the lower surface.

[0026] The equiangular-Archimedes composite spiral feed includes: an antenna radiating element, a feed balun, and a reflective back cavity.

[0027] The continuous innovation of 3D printing technology has opened up a cost-effective solution for the preparation of complex three-dimensional components. This breakthrough technology has shown significant advantages in the field of metamaterial manufacturing, especially in the innovative research and development of Luneburg lenses. Its core principle is to divide the lens structure into a micro-unit array, construct the metamaterial microstructure through additive manufacturing technology to fill each unit, and precisely control the material distribution density within the unit to achieve the design of the dielectric constant distribution. This hierarchical construction strategy not only realizes the control of the gradient distribution of the dielectric constant within the lens space, but can also highly restore the continuous dielectric constant distribution characteristics through the parameter optimization of discrete units.

[0028] For the convenience of understanding, the following will specifically introduce the low-frequency broadband circularly polarized wide-angle beam scanning 3D printed truncated Luneburg lens and the equiangular - Archimedean composite spiral feed source provided by the embodiments of the present invention, respectively.

[0029] In a traditional Luneburg lens, its equivalent dielectric constant distribution satisfies the following formula:

[0030] where, r represents the distance from any point in the lens to the center of the lens sphere, R represents the radius of the lens.

[0031] According to Hamilton's optical theory, the focus of the Luneburg lens can be transferred from the lens surface to the inside of the lens, that is, a generalized Luneburg lens (or called Gutman lens) is obtained, and the dielectric constant distribution formula is:

[0032] where, f is the distance from the focus of the generalized Luneburg lens to the center of the lens sphere.

[0033] Generally, f = m R (0 < m < 1), that is, through Hamilton's optics, the focus of the lens is transferred from the surface of the lens to the spherical surface inside the lens at a distance of m R from the center of the lens, and then passes through the focal spherical surface inside the lens and is truncated at a distance of t = n R (n < m) from the center of the lens to obtain the proposed truncated Luneburg lens.

[0034] There are countless combinations of m and n. Considering factors such as the appropriate arrangement of the feed source on the truncation plane, the overall gain within the scanning range and its fluctuations, etc., m = 0.75 and n = 0.6 are selected as the design parameters in the present invention.

[0035] The ray tracing method in COMSOL was used to study the focus positions of two lenses with different truncation depths near the truncation plane. Figure 2The focal positions of two Luneburg lenses with different truncation depths are given. When the reference lens is truncated at the focal circle, i.e., t = 0.75... R The focal point is located 0.75 meters from the center of the lens. R On the circle, as shown by the red dashed line in (a). At this time, the feed sources P1-P5, arranged in a straight line, are all located on the same side of the focal plane, with the middle feed source P3 located exactly at the focal point of the lens. The antenna device has the maximum directivity when fed at this location. However, looking from the middle feed source towards both ends, the distance between the feed source and the focal plane gradually increases, which causes the directivity of the main beam of the antenna device to decrease with the increase of the beam scanning angle. In contrast, when t = 0.6 R At this time, the large refractive index difference on both sides of the truncated plane causes parallel rays to focus earlier, resulting in the focal point on the outer side of the truncated plane shifting upwards to varying degrees, as shown by the black dashed line in (b). Therefore, compared to a lens truncated at the focal circle, a Luneburg lens truncated through the inside of the focal circle has a focal surface with a larger radius of curvature. In this case, the feed sources P1-P5, arranged in a straight line, are located on both sides of the focal surface, and the range of distances from the feed sources to the focal surface is smaller, which is also very advantageous for achieving wide-angle beam scanning with low gain ripple.

[0036] Since materials with graded refractive indices do not exist in nature, to achieve a graded refractive index, the spherical Luneburg lens is discretized into concentric spherical layers of equal thickness, and then each layer is discretized into smaller units. However, as the number of Luneburg lens layers increases, the improvement in its radiation characteristics becomes less significant. Therefore, considering various factors, the Luneburg lens in this embodiment of the invention is constructed as a 10-layer structure, i.e., M is 10, and each layer is filled with units having a corresponding equivalent refractive index. Table 1 shows the dielectric constant and radius of each layer of the 10-layer Luneburg lens.

[0037] Table 1

[0038] Please refer to the structural diagram of the unit cell in the Luneburg lens. Figure 3 As shown, the geometric dimensions of the element (length, width, and height) are all no greater than one-eighth of the incident electromagnetic wave wavelength. The geometric dimensions of the element can be set to 10mm × 10mm × 10mm, which is one-twelfth of the 2.5GHz vacuum wavelength, thus ensuring the validity of the equivalent medium theory. Each element can consist of three mutually orthogonal dielectric rods, and the equivalent refractive index is controlled by adjusting the size of the dielectric rods. Within the element, the air column filling it has the same dimensions in the x and y directions, which also helps to achieve circularly polarized beam scanning. (Corresponding to...) Figure 3As can be seen in the diagram, the side length of the air column in the x and y directions of the unit is b, and the height of the air column in the z direction is 10 mm. The gradient refractive index is achieved by changing the side length b of the air column in the unit. For a schematic diagram of a Luneburg lens composed of several units, please refer to [link to schematic diagram]. Figure 4 .

[0039] By modeling and analyzing in HFSS simulation software, electromagnetic waves of different polarizations were incident on the element to obtain parameter S. As can be understood, parameter S represents the scattering parameter, an important parameter in microwave transmission used to describe the frequency domain characteristics of the transmission channel. From parameter S, the equivalent refractive index for x-polarized and y-polarized incident waves can be derived, as shown in the following formula:

[0040] Where 'a' is the side length of the element, which is 10 mm in this invention, and 'λ' is the wavelength of the incident electromagnetic wave in free space. For a diagram showing the relationship between the equivalent refractive index of the element and the side length 'b' of the air column, please refer to [link / reference needed]. Figure 5 .from Figure 5 As can be seen, by changing the unit within the achievable size range, the equivalent refractive index can be varied from 1 to 2.8. For a graph showing the relationship between the equivalent refractive index and frequency of a unit in a truncated Luneburg lens provided in this embodiment of the invention, please refer to [link to relevant documentation]. Figure 6 .from Figure 6 As can be seen, the unit has characteristics that are independent of frequency.

[0041] To provide circularly polarized electromagnetic waves, this invention employs an equiangular-Archimedean composite spiral feed as the feeding antenna.

[0042] An equiangular-Archimedes composite spiral feed consists of an antenna radiating element, a feed balun, and a reflective cavity. The antenna radiating element is mainly responsible for the radiation and reception of electromagnetic waves. The feed balun can realize the conversion from unbalanced to balanced feed and impedance matching. The reflective cavity can reflect the electromagnetic waves radiated backward by the antenna device, thereby improving the antenna's normal gain.

[0043] Please refer to the front and top views of an isoangular-Archimedes composite helical feed source provided in this embodiment of the invention. Figure 7 For a physical machining drawing of the equiangular-Archimedes composite spiral feed, please refer to [link / reference needed]. Figure 8 The following will combine Figure 7 and Figure 8 The structure of the equiangular-Archimedes composite spiral feed is introduced.

[0044] Specifically, the radiation structure of an equiangular-Archimedes coincident spiral antenna may include: a dielectric substrate 1, an Archimedean spiral 2, an equiangular spiral 3, a resistor 4, a reflective back cavity 5, a feed balun 6, and a feed port 7.

[0045] To verify the analysis regarding the cutoff depth, simulations were performed in CST software for lenses with two cutoff depths, t = 0.75R and t = 0.6R. Figure 10 As shown in (a) above, the gain variation of the Luneburg lens at two different cutoff depths is obtained by moving the feed source, as shown in (a). Figure 10 As shown in (b), the results show that when the feed offset is 100mm, the gain fluctuation of the lens with t=0.6R is less than 1.46dB (better than 2.5dB with t=0.75R), which means that it has a larger scanning angle. Therefore, the lens with t=0.6R was selected for subsequent analysis and testing.

[0046] The test was conducted using a vector mesh analyzer. Figure 11 Simulation and test results of the gain of the broadband circularly polarized wide-angle beam scanning antenna device with and without a lens are presented, as well as simulation and test results of the axial ratio of the truncated Luneburg lens. The figures show that the measured gain of the isoangular-Archimedean composite spiral feed itself and after adding the lens are in good agreement with the simulation results. Furthermore, at the center frequency of 2.5 GHz, the proposed antenna device achieves a gain of 18.05 dBi, an improvement of approximately 11.02 dBi compared to the isoangular-Archimedean composite spiral feed. In addition, the figures show that the proposed broadband circularly polarized wide-angle beam scanning antenna device has an axial ratio of less than 3 dB in the operating frequency band of 1.5–3.5 GHz, exhibiting excellent circular polarization performance.

[0047] The simulation and test radiation patterns of the antenna device proposed in this invention are as follows: Figure 12 and Figure 13 As shown. From Figure 12 and Figure 13 As can be seen, the proposed wideband circularly polarized wide-angle beam scanning antenna exhibits a gain fluctuation of less than 1.46 dBi within a beam scanning range of ±43°, and the simulated and measured radiation patterns show similar characteristics. Increasing the lens size could further expand the scanning angle and improve the gain, but this might increase weight and manufacturing costs.

[0048] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that the terms "in one embodiment," "for example," and "again" in this invention are intended to illustrate the invention and are not intended to limit the invention.

[0049] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A wideband circularly polarized wide-angle beam scanning antenna device based on truncated Leaky Lens, characterized in that, The application relates to a truncated Luneberg lens and an equiangular-Archimedes composite spiral feed source, the equiangular-Archimedes composite spiral feed source is arranged at the center of the lower surface of the truncated Luneberg lens and is away from the lower surface by a preset distance; the equiangular-Archimedes composite spiral feed source adopts an equiangular spiral antenna at a high frequency and an Archimedes spiral antenna at a low frequency; the truncated depth of the truncated Luneberg lens is smaller than the radius of the lens to form a flat focal plane, the flat focal plane is a concentric spherical surface of the lens and supports the equiangular-Archimedes composite spiral feed source to realize circular polarization wide-angle beam scanning through linear displacement.

2. The broadband circularly polarized wide-angle beam scanning antenna apparatus of claim 1, wherein, The equiangular-Archimedes composite spiral feed source comprises an antenna radiation unit, a feed balun and a reflective back cavity, the antenna radiation unit is connected with the feed balun, the reflective back cavity is arranged below the antenna radiation unit and is connected with the grounding part of the feed balun to jointly provide the antenna device with backward electromagnetic wave reflection to realize unidirectional radiation; the antenna radiation unit is used for electromagnetic wave radiation and reception, the feed balun is used for converting unbalanced feeding to realize balanced feeding, and the reflective back cavity is used for reflecting the electromagnetic waves backwardly radiated by the antenna device, improving the normal gain of the antenna, realizing unbalanced conversion and impedance matching.

3. The broadband circularly polarized wide-angle beam scanning antenna apparatus of claim 1, wherein, The truncated Luneberg lens comprises M concentrically arranged spherical layers; wherein M is a positive integer, each spherical layer has the same thickness and comprises a plurality of metamaterial structure units with corresponding equivalent dielectric constants, and each metamaterial structure unit is connected with surrounding adjacent metamaterial structure units; the metamaterial structure unit is an air column filled metamaterial; the air column filled metamaterial is in a cubic shape, wherein the size of the air column in the x and y directions is the same, that is, the air column is in a square shape with a side length smaller than that of the metamaterial in the xy cross section, and the size of the air column in the z direction is equal to the side length of the metamaterial, and the equivalent dielectric constant of the corresponding metamaterial structure unit is controlled by adjusting the side length of the air column.

4. The broadband circularly polarized wide-angle beam scanning antenna apparatus of claim 1, wherein, The truncated Luneberg lens has a gradient refractive index change from small to large from the edge to the center of the sphere, and the gradient refractive index change is realized by the equal-thickness layered design of the metamaterial structure units of the air-filled metamaterial, and the dielectric constant of each layer is realized by changing the size of the air column, that is, the duty cycle of the metamaterial structure unit.

5. The broadband circularly polarized wide-angle beam scanning antenna apparatus of claim 1, wherein, The metamaterial comprises a photosensitive resin.

6. The broadband circularly polarized wide-angle beam scanning antenna apparatus of claim 1, wherein, The side length of the metamaterial is less than one-eighth of the corresponding wavelength of the center frequency.

7. The wide-band circularly polarized wide-angle beam scanning antenna apparatus of claim 2, wherein, The antenna radiation unit comprises a dielectric substrate, an Archimedes spiral line, an equiangular spiral line and a resistor, the equiangular spiral line is located in the inner circle, the Archimedes spiral line is located in the outer circle, and the two are arranged on the upper surface of the dielectric substrate; the feed balun is located at the bottom center of the dielectric substrate; the reflective back cavity is located directly below the dielectric substrate, and the cavity bottom is connected with the grounding plate of the balun.

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