Metasurface Luneburg Lenses and Base Station Antennas

Abstract

This invention discloses a metasurface Luneburg lens and a base station antenna, comprising a transmission array composed of multiple layers of parallel and equally spaced artificial electromagnetic metasurfaces; the artificial electromagnetic metasurfaces include a printed circuit board and multiple rows and columns of metal patterns arranged on the plane of the printed circuit board; the transmission array has an equivalent dielectric constant adjustment region, which is the planar region where the metal patterns in the two adjacent rows at the center of each layer of artificial electromagnetic metasurfaces are located, and the metal patterns in the equivalent dielectric constant adjustment region have different sizes and / or different arrangement densities than the other metal patterns on the artificial electromagnetic metasurfaces. This invention not only allows for flexible adjustment of the vertical half-power angle while maintaining a constant horizontal half-power angle, but also ensures consistent radiation patterns between different beams, thereby improving the adaptability of the Luneburg lens antenna.

Description

Technical Field

[0001] This invention relates to the field of communication device technology, and in particular to a metasurface Luneburg lens and a base station antenna. Background Technology

[0002] In the field of wireless communication, antennas, as devices for receiving and transmitting electromagnetic waves, typically require customized design based on specific application scenarios for their performance, especially gain and radiation pattern specifications. Existing Luneburg lens antenna technology, especially spherical Luneburg lens antennas, possesses unique directional characteristics. Through an artificial electromagnetic material, the refractive index distribution decreases gradually from the center to the edge, allowing electromagnetic waves to converge continuously as they pass through the lens, ultimately forming a highly symmetrical radiation pattern. This results in a narrower main lobe beam, significantly increased gain, and enhanced wireless signal strength, while sidelobe levels are controlled to extremely low levels, effectively eliminating interference to neighboring cells. However, the highly symmetrical radiation pattern of Luneburg lens antennas is ill-suited to asymmetrical wireless coverage scenarios, such as horizontally-vertically asymmetrical cells, making it difficult to adapt to various complex application scenarios. Summary of the Invention

[0003] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a metasurface Luneburg lens and base station antenna that can not only flexibly adjust the vertical half-power angle while keeping the horizontal half-power angle unchanged, but also keep the radiation pattern consistent between different beams, thereby improving the adaptability of the Luneburg lens antenna.

[0004] In a first aspect, embodiments of the present invention provide a metasurface Luneburg lens, comprising a transmission array composed of multiple layers of parallel and equally spaced artificial electromagnetic metasurfaces; the artificial electromagnetic metasurfaces include a printed circuit board and multiple rows and columns of metal patterns disposed on the plane of the printed circuit board; the transmission array has an equivalent dielectric constant adjustment region, which is a planar region where the metal patterns in the two adjacent rows at the center of each layer of artificial electromagnetic metasurfaces of the transmission array are located, and the metal patterns in the equivalent dielectric constant adjustment region have different sizes and / or different arrangement densities than the other metal patterns of the artificial electromagnetic metasurfaces.

[0005] A metasurface Luneburg lens provided according to an embodiment of the present invention has at least the following beneficial effects:

[0006] This invention provides an artificial electromagnetic metasurface (AEM) by fabricating multiple rows and columns of metal patterns on a metal-coated printed circuit board. These AEMs are then stacked in parallel, equally spaced rows to form a spherical transmission array. This array refracts and converges electromagnetic waves from each AEM layer into a single beam. Furthermore, the planar region containing the metal patterns in the two adjacent rows at the center of each AEM layer of the Luneburg lens is designated as an equivalent dielectric constant adjustment region and differentiated from other regions. By adjusting the size and density of the metal patterns in this adjustment region, the equivalent dielectric constant near the equatorial plane of the Luneburg lens is increased or decreased. This causes the vertical half-power angle to change with the equivalent dielectric constant, allowing for flexible adjustment of the vertical half-power angle while maintaining a constant horizontal half-power angle. Additionally, it ensures consistent radiation patterns across different beams, thereby improving the adaptability of the Luneburg lens antenna.

[0007] According to some embodiments of the present invention, the metal patterns in the equivalent dielectric constant adjustment region are of the same size and gradually decrease from the equivalent dielectric constant adjustment region toward the edge, or gradually decrease and remain unchanged.

[0008] According to some embodiments of the present invention, the size of the metal pattern in the equivalent dielectric constant adjustment region does not exceed 1 / 4 wavelength.

[0009] According to some embodiments of the present invention, the distance between the center points of each metal pattern in the equivalent dielectric constant adjustment region is equal.

[0010] According to some embodiments of the present invention, each layer of the artificial electromagnetic metasurface has central symmetry, left-right symmetry, and top-bottom symmetry.

[0011] According to some embodiments of the present invention, the number of metal patterns on the artificial electromagnetic metasurface of the intermediate layer of the transmission array is the largest, and the number of metal patterns on the artificial electromagnetic metasurfaces on both sides of the intermediate layer of the transmission array gradually decreases or remains unchanged.

[0012] According to some embodiments of the present invention, the shape of the metal pattern includes geometric shapes such as square, rhombus, circle or cross.

[0013] According to some embodiments of the present invention, the printed circuit board is manufactured from a dielectric substrate with metal cladding on one or both sides.

[0014] In a second aspect, embodiments of the present invention provide a base station antenna, including a feed source and a metasurface Luneburg lens as described in the first aspect embodiment. The feed source is arranged around the spherical periphery of the equivalent Luneburg sphere of the metasurface Luneburg lens. The electromagnetic waves radiated by the feed source are refracted by the metasurface Luneburg lens and converged into a beam pointing from the feed source to the center of the sphere of the metasurface Luneburg lens, and each feed source corresponds to one beam.

[0015] According to some embodiments of the present invention, a metal reflector is also included, the feed source is mounted on the metal reflector and focused by the metasurface Luneburg lens to generate a correspondingly oriented beam.

[0016] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0017] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0019] Figure 1 This is a schematic diagram of the overall structure of the metasurface Luneburg lens provided in an embodiment of the present invention;

[0020] Figure 2 This is a front view of the artificial electromagnetic metasurface provided in an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the overall structure of the base station antenna provided in an embodiment of the present invention;

[0022] Figure 4 This is the radiation pattern of the base station antenna provided in an embodiment of the present invention. Detailed Implementation

[0023] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0024] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," "exceeding," etc. are understood to exclude the number itself, while "above," "below," "within," etc. are understood to include the number itself. "Any one" refers to one or more, and "at least one of the following" and similar expressions refer to any combination of these items, including any combination of single or multiple items. If "first" or "second" is used in the description, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of the indicated technical features.

[0025] It should be noted that the terms "setting," "installing," and "connecting" in the embodiments of this invention should be interpreted broadly. Those skilled in the art can reasonably determine the specific meaning of the above terms in the embodiments of this invention in conjunction with the specific content of the technical solution. For example, the term "connection" can be a mechanical connection, an electrical connection, or a connection that allows for mutual communication; it can be a direct connection or an indirect connection through an intermediate medium.

[0026] It should be noted that the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] First, let's clarify some of the terms used in this invention:

[0028] A Luneberg lens is a dielectric sphere made of several layers of materials with different dielectric constants. It focuses electromagnetic waves incident on the inner surface of a metallic reflector, and after reflection, returns the reflected wave to the direction of the source. It is primarily used to create false targets to deceive radar. Luneberg lens reflectors have advantages such as small size, a larger radar cross-section than corner reflectors of the same size, and a wide reflection pattern in both horizontal and vertical directions. However, traditional Luneberg lenses are heavy, expensive, and complex to manufacture.

[0029] Electromagnetic metasurfaces, also known as metasurfaces, are artificial layered materials with a thickness less than the wavelength. Based on their in-plane structure, metasurfaces can be divided into two types: those with transverse subwavelength microstructures and those that are homogeneous films. Metasurfaces allow for flexible and effective control over the phase, polarization, and propagation mode of electromagnetic waves. Novel physical effects such as negative refraction, negative reflection, polarization rotation, converging imaging, complex beamforming, and the conversion of propagating waves into surface waves can be achieved through metasurfaces. The rich and unique physical properties of metasurfaces and their flexible control over electromagnetic waves make them promising candidates for applications in stealth technology, antenna technology, microwave and terahertz devices, and optoelectronic devices.

[0030] Artificial electromagnetic metasurfaces are composed of a series of artificially designed two-dimensional periodic structures and possess electromagnetic control characteristics such as planarity, wide frequency domain, wide angular domain, and programmability.

[0031] A transmission array is a discrete plane lens composed of subwavelength units. It uses discrete transmission units to convert incident waves into outgoing plane waves that propagate in a specified direction, thereby achieving the function of focusing the beam.

[0032] In the field of wireless communication, antennas, as devices for receiving and transmitting electromagnetic waves, typically require customized design based on specific application scenarios for their performance, especially gain and radiation pattern specifications. Existing Luneburg lens antenna technology, especially spherical Luneburg lens antennas, possesses unique directional characteristics. Through an artificial electromagnetic material, the refractive index distribution decreases gradually from the center to the edge, allowing electromagnetic waves to converge continuously as they pass through the lens, ultimately forming a highly symmetrical radiation pattern. This results in a narrower main lobe beam, significantly increased gain, and enhanced wireless signal strength, while sidelobe levels are controlled to extremely low levels, effectively eliminating interference to neighboring cells. However, the highly symmetrical radiation pattern of Luneburg lens antennas is ill-suited to asymmetrical wireless coverage scenarios, such as horizontally-vertically asymmetrical cells, making it difficult to adapt to various complex application scenarios.

[0033] Based on this, embodiments of the present invention provide a metasurface Luneburg lens and a base station antenna, which can not only flexibly adjust the vertical half-power angle while keeping the horizontal half-power angle constant, but also maintain consistent radiation patterns between different beams, thereby improving the adaptability of the Luneburg lens antenna.

[0034] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0035] Reference Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the overall structure of the metasurface Luneburg lens provided in an embodiment of the present invention. The metasurface Luneburg lens 10 provided in the first aspect embodiment of the present invention includes a transmission array composed of multiple layers of parallel and equally spaced artificial electromagnetic metasurfaces 100. The artificial electromagnetic metasurfaces 100 include a printed circuit board 110 and multiple rows and columns of metal patterns 120 disposed on the plane of the printed circuit board 110. The transmission array has an equivalent dielectric constant adjustment region 130, which is the planar region where the metal patterns 120 in the two adjacent rows at the center of each layer of artificial electromagnetic metasurfaces 100 of the transmission array are located. The metal patterns 120 in the equivalent dielectric constant adjustment region 130 have different sizes and / or different arrangement densities than the other metal patterns 120 of the artificial electromagnetic metasurfaces 100.

[0036] It should be noted that, as Figure 1As shown, the metasurface Luneburg lens 10 of this embodiment is composed of multiple layers of artificial electromagnetic metasurfaces 100. The artificial electromagnetic metasurfaces 100 are arranged in parallel layers along the same direction and at equal intervals to form a transmission array. The transmission array is used to refract and converge the electromagnetic waves radiated from the feed source into a high-gain narrow beam pointing from the feed source to the center of the sphere. The electromagnetic wave converging effect is achieved after the electromagnetic waves are refracted by each layer of artificial electromagnetic metasurfaces 100 in the transmission array.

[0037] Furthermore, such as Figure 2 As shown, Figure 2 This is a front view of the artificial electromagnetic metasurface 100 provided in an embodiment of the present invention. The artificial electromagnetic metasurface 100 is composed of a printed circuit board 110 and a plurality of metal patterns 120 arranged in rows and columns on the board. The printed circuit board 110 serves as the substrate of the metasurface, providing mechanical support, and its material can be a metal-clad laminate, such as a copper-clad laminate. Furthermore, the metal patterns 120 can be processed on the printed circuit board 110 by photolithography or etching processes to obtain the artificial electromagnetic metasurface 100. The metal patterns 120 can be processed on one side of the printed circuit board 110 or on both sides of the printed circuit board 110.

[0038] It is understandable that, such as Figure 1 and Figure 2 As shown, the planar regions where the metal patterns 120 in two adjacent rows at the center of each layer of artificial electromagnetic metasurface 100 jointly constitute an equivalent dielectric constant adjustment region 130 of the transmission array. The metal patterns 120 in this adjustment region are different in size and arrangement density from the other metal patterns 120 of the artificial electromagnetic metasurface 100, and one of the size or arrangement density can be adjusted differently.

[0039] According to an embodiment of the present invention, a metasurface Luneburg lens 10 is provided. Multiple rows and columns of metal patterns 120 are processed on a printed circuit board 110 with a metal coating to obtain an artificial electromagnetic metasurface 100. Then, multiple layers of artificial electromagnetic metasurfaces 100 are stacked in parallel and at equal intervals to form a spherical transmission array. The electromagnetic waves passing through each layer of artificial electromagnetic metasurfaces 100 in the transmission array are refracted and focused into a beam. Furthermore, the planar region containing the two adjacent rows of metal patterns 120 at the center of each layer of artificial electromagnetic metasurface 100 of the metasurface Luneburg lens 10 is designated as the equivalent dielectric constant adjustment region 130 and designed differently from other regions. By adjusting the size and arrangement density of the metal patterns 120 in the equivalent dielectric constant adjustment region 130, the equivalent dielectric constant near the equatorial plane of the metasurface Luneburg lens 10 can be increased or decreased, so that the vertical half-power angle changes with the change of the equivalent dielectric constant. This not only allows for flexible adjustment of the vertical half-power angle while keeping the horizontal half-power angle constant, but also maintains consistency in the radiation patterns between different beams, thereby improving the adaptability of the Luneburg lens antenna.

[0040] Reference Figure 2 In some embodiments of the present invention, the metal pattern 120 of the equivalent dielectric constant adjustment region 130 has the same size and gradually decreases from the equivalent dielectric constant adjustment region 130 to the edge, or gradually decreases and remains unchanged.

[0041] It is understandable that the metal patterns 120 in the equivalent dielectric constant adjustment region 130 are of the same size. As the equivalent dielectric constant adjustment region 130 moves further away from the center of the artificial electromagnetic metasurface 100, the size of the metal patterns 120 closer to the edge of the artificial electromagnetic metasurface 100 gradually decreases, or gradually decreases and then remains constant. Specifically, in each layer of the artificial electromagnetic metasurface 100, the metal patterns 120 closer to the equivalent dielectric constant adjustment region 130 are larger, resulting in a higher relative refractive index in the surrounding space; conversely, the metal patterns 120 farther from the equivalent dielectric constant adjustment region 130 gradually decrease in size or remain constant, corresponding to a gradient decrease in relative refractive index. Figure 2 As shown, one column of the artificial electromagnetic metasurface has four different sizes of metal patterns, all of which are square metal patterns. Let a represent the side length of the metal pattern in the equivalent dielectric constant adjustment region 130, and b, c, and d represent the side lengths of the other three metal patterns in the equivalent dielectric constant adjustment region 130, respectively. It can be seen that the size of the four metal patterns decreases in a gradient, and their size relationship expressed by the side length is a > b > c > d.

[0042] In some embodiments of the present invention, the size of the metal pattern 120 in the equivalent dielectric constant adjustment region 130 does not exceed 1 / 4 wavelength. It should be noted that the size of the metal pattern 120 located in the equivalent dielectric constant adjustment region 130 does not exceed 1 / 4 wavelength; for example, the specific size can be represented by the side length 'a' of the metal pattern within the equivalent dielectric constant adjustment region 130. Specifically, the side length 'a' of the metal pattern 120 in the equivalent dielectric constant adjustment region 130 can be set below 1 / 4 wavelength, i.e., a ≤ 0.25λ0, where λ0 is the operating wavelength.

[0043] In some embodiments, since the size of the metal pattern within the equivalent dielectric constant adjustment region 130 does not exceed 1 / 4 wavelength (i.e., side length a < 0.25λ0), the width d of the equivalent dielectric constant adjustment region 130, which comprises the planar regions of the two adjacent rows of metal patterns 120 at the center of each artificial electromagnetic metasurface 100, on the plane of each artificial electromagnetic metasurface 100 does not exceed 1 / 2 wavelength. Specifically, the width d of the equivalent dielectric constant adjustment region 130 on the plane of each artificial electromagnetic metasurface 100 can be set below 1 / 2 wavelength, i.e., d ≤ 0.5λ0, where λ0 is the operating wavelength.

[0044] Reference Figure 2 In some embodiments of the present invention, the distance between the center points of each metal pattern 120 in the equivalent dielectric constant adjustment region 130 is equal.

[0045] It should be noted that in the equivalent dielectric constant adjustment region 130, the distance between the center points of two adjacent metal patterns 120 in the same row is equal, and the distance between the center points of two adjacent metal patterns 120 in the same column is also equal. For example... Figure 2 As shown, the distance w between the center points of two adjacent metal patterns 120 in the equivalent dielectric constant adjustment region 130 is equal.

[0046] In some embodiments of the present invention, each layer of artificial electromagnetic metasurface 100 has central symmetry, left-right symmetry and top-bottom symmetry.

[0047] It should be noted that, in the embodiments provided by the present invention, since the artificial electromagnetic metasurface 100 is centrally symmetrical, left-right symmetrical, and top-bottom symmetrical, the dielectric plate and metal pattern 120 in the artificial electromagnetic metasurface 100 both have central symmetry, left-right symmetry, and top-bottom symmetry.

[0048] In some embodiments of the present invention, the number of metal patterns 120 on the artificial electromagnetic metasurface 100 in the middle layer of the transmission array is the largest, and the number of metal patterns 120 on both sides of the artificial electromagnetic metasurface 100 in the middle layer of the transmission array gradually decreases or remains unchanged.

[0049] In some embodiments of the present invention, the shape of the metal pattern 120 includes geometric shapes such as square, rhombus, circle, or cross. It should be noted that the shape of the metal pattern 120 is not limited in the embodiments of the present invention.

[0050] In some embodiments of the present invention, the printed circuit board 110 is fabricated from a dielectric substrate with metal on one or both sides.

[0051] It is understood that the metal layers in the printed circuit board 110 can be processed on one side or both sides of the dielectric substrate. Specifically, each layer of artificial electromagnetic metasurface 100 is a printed circuit board 110 made of a dielectric substrate with single-sided or double-sided copper cladding. The upper surface of the printed circuit board 110 is processed with a metal pattern 120. The thickness and relative permittivity of the dielectric substrate of the printed circuit board 110 can be selected according to actual needs, and this embodiment of the invention does not limit them.

[0052] Reference Figure 3 , Figure 3 This is a schematic diagram of the overall structure of a base station antenna provided in an embodiment of the present invention. A second aspect of the present invention provides a base station antenna, which includes a feed 20 and a metasurface Luneburg lens 10 as described in any of the above embodiments. The feed 20 is disposed along the periphery of the equivalent Luneburg sphere of the metasurface Luneburg lens 10, which approximates the circumscribed sphere of the metasurface Luneburg lens 10. Electromagnetic waves radiated from the feed 20 are refracted by the metasurface Luneburg lens 10 and converged into a beam pointing from the feed 20 to the center of the metasurface Luneburg lens 10. Each feed 20 corresponds to one beam. Placing multiple feed 20s will generate multiple beams corresponding to the number of feed 20s. Figure 3 As shown, this can be specifically achieved through... Figure 1 A single-beam Luneburg antenna can be obtained by mounting a feed source 20 directly below the metasurface Luneburg lens 10.

[0053] It should be noted that in the embodiments provided by the present invention, the specific structure of the metasurface Luneburg lens 10 refers to the above embodiments. Since the base station antenna of the present invention adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0054] Reference Figure 3 In some embodiments of the present invention, a metal reflector 30 is further included, and the feed source 20 is mounted on the metal reflector 30 and focused by the metasurface Luneburg lens 10 to generate a correspondingly oriented beam. It should be noted that, in the embodiments of the present invention, the feed source 20 is mounted on the metal reflector 30 to reduce back radiation and improve the front-to-back ratio of the antenna.

[0055] Reference Figure 4 , Figure 4 This is an embodiment of the present invention. Figure 3 The diagram illustrates an example of the effect of half-power angle adjustment on a base station antenna. It is understood that the horizontal and vertical half-power angles of the base station antenna using this embodiment of the invention exhibit a significant difference: the horizontal half-power angle is 14°, and the vertical half-power angle is 32°, meaning the vertical half-power angle is more than twice the horizontal half-power angle.

[0056] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A metasurface Luneburg lens, characterized in that, The transmission array comprises a transmission array consisting of multiple parallel and equally spaced artificial electromagnetic metasurfaces; each artificial electromagnetic metasurface includes a printed circuit board and multiple rows and columns of metal patterns disposed on the plane of the printed circuit board; the transmission array has an equivalent dielectric constant adjustment region, which is the planar region where the metal patterns in the two adjacent rows at the center of each layer of the artificial electromagnetic metasurface are located; the metal patterns in the equivalent dielectric constant adjustment region have different sizes and / or different arrangement densities than the other metal patterns on the artificial electromagnetic metasurface; the metal patterns in the equivalent dielectric constant adjustment region have the same size; and the size of the other metal patterns on the artificial electromagnetic metasurface gradually decreases from the equivalent dielectric constant adjustment region toward the edge of the artificial electromagnetic metasurface, or gradually decreases and then remains unchanged.

2. The metasurface Luneburg lens according to claim 1, characterized in that, The size of the metal pattern in the equivalent dielectric constant adjustment region does not exceed 1 / 4 wavelength.

3. The metasurface Luneburg lens according to claim 2, characterized in that, The distance between the center points of each metal pattern in the equivalent dielectric constant adjustment region is equal.

4. The metasurface Luneburg lens according to claim 1, characterized in that, Each layer of the artificial electromagnetic metasurface has central symmetry, left-right symmetry, and top-bottom symmetry.

5. The metasurface Luneburg lens according to claim 1, characterized in that, The number of metal patterns on the artificial electromagnetic metasurface in the middle layer of the transmission array is the largest, while the number of metal patterns on the artificial electromagnetic metasurfaces on both sides of the middle layer of the transmission array gradually decreases or remains unchanged.

6. The metasurface Luneburg lens according to claim 1, characterized in that, The shape of the metal pattern includes square, rhombus, circle or cross.

7. The metasurface Luneburg lens according to claim 1, characterized in that, The printed circuit board is manufactured from a dielectric substrate with metal cladding on one or both sides.

8. A base station antenna, characterized in that, The device includes a feed source and a metasurface Luneburg lens as described in any one of claims 1 to 7. The feed source is arranged around the spherical periphery of the equivalent Luneburg sphere of the metasurface Luneburg lens. The electromagnetic waves radiated by the feed source are refracted by the metasurface Luneburg lens and converged into a beam pointing from the feed source to the center of the sphere of the metasurface Luneburg lens. Each feed source corresponds to one beam.

9. The base station antenna according to claim 8, characterized in that, It also includes a metal reflector, on which the feed source is mounted and focused by the metasurface Luneburg lens to generate a beam pointing in a corresponding direction.

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