An equidifferent layered inner focal Luneberg lens antenna

Abstract

The application belongs to the technical field of lens antennas, and particularly relates to an inner-focus dragon lens antenna based on an arithmetic progression layer, which comprises a horn-shaped feed source and an inner-focus dragon lens, the horn-shaped feed source is arranged at the bottom surface center position of the inner-focus dragon lens; the inner-focus dragon lens is divided into ten layers by using an arithmetic progression thickness method, wherein the spherical center layer is the first layer, and the outermost layer is the tenth layer; the thickness of the first layer of the inner-focus dragon lens is 0.4 times the radius of the entire inner-focus dragon lens, the thickness of the second layer is 1.6 mm, and the thickness of each layer is smaller than that of the previous layer by d=0.15 mm starting from the third layer; the inner-focus dragon lens is subjected to layering treatment by using the arithmetic progression thickness layering method, and the gain of the spherical lens antenna and the inner-focus lens antenna is improved.

Description

Technical Field

[0001] This invention belongs to the field of lens antenna technology, specifically relating to an inner focal Luneburg lens antenna based on equidistant layering. Background Technology

[0002] Terahertz waves refer to electromagnetic waves with frequencies between 100 GHz and 10000 GHz, falling between microwaves and light waves. Terahertz waves exhibit many characteristics distinct from other types of electromagnetic radiation, and offer high communication transmission capacity and speed, with higher resolution and more precise positioning capabilities than microwaves. They have broad application prospects in military identification, positioning, and radar communication. A Luneburg lens is a graded-dielectric spherical lens, characterized by the fact that any point on its surface is a focal point, converting spherical waves at the focal point into plane waves. Since materials with a gradually changing dielectric constant do not exist in nature, current techniques involve layering the sphere to achieve a gradient dielectric constant to approximate an ideal graded-dielectric medium. Among layering techniques, the most commonly used is the equal-thickness layering method, where each layer is of uniform thickness. The biggest advantage of this method is its simple structure and ease of fabrication. However, this results in a large difference in dielectric constant between the outer layers, increasing reflection loss between adjacent layers, reducing transmission efficiency, and consequently reducing gain and aperture efficiency. Since the size of circuits and electronic devices has decreased dramatically in the terahertz band, reducing the size of lenses is particularly important. However, most current Luneburg lens designs use global lenses with the focal point on the surface, which are 2R in length, width and height. This greatly increases the size of the overall device, which is not conducive to integration and also increases the cost. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention proposes an inner-focus Luneburg lens antenna based on arithmetic progression. The antenna includes a horn-shaped feed and an inner-focus Luneburg lens. The horn-shaped feed is positioned at the center of the bottom surface of the inner-focus Luneburg lens. The inner-focus Luneburg lens is divided into ten layers using an arithmetic progression method, with the spherical core layer being the first layer and the outermost layer being the tenth layer. The thickness of the first layer of the inner-focus Luneburg lens is 0.4 times the radius of the entire inner-focus Luneburg lens, the thickness of the second layer is 1.6 mm, and from the third layer onwards, the thickness of each layer is d = 0.15 mm less than the thickness of the previous layer.

[0004] Preferably, the horn-shaped feed is a rectangular pyramidal horn fed by a standard rectangular waveguide WR-4.3.

[0005] Furthermore, the horn-shaped feed operates at a frequency of 220 GHz.

[0006] Preferably, the dielectric constant of each lens layer in the inner focal point Luneburg lens is related to the thickness of each lens layer, and the formula for calculating the dielectric constant is:

[0007]

[0008] The beneficial effects of this invention are:

[0009] This invention employs an equal-thickness layering method to process the inner focal point Luneburg lens in layers, thereby improving the gain of both the spherical lens antenna and the inner focal point lens antenna. The beam scanning performance of this invention is significantly better than that of the traditional Luneburg lens antenna. Under the same lateral defocusing distance, the beam scanning angle of this invention is much larger than that of the spherical lens. When the lateral defocusing is 2mm, the beam scanning angle of this invention is 22°, while that of the spherical lens is only 7°. Attached Figure Description

[0010] Figure 1 This is a structural diagram of the inner focal Luneburg lens antenna of the present invention;

[0011] Figure 2 This is a cross-sectional view of the inner focal Luneburg lens antenna of the present invention;

[0012] Figure 3 This is a schematic diagram of the inner focal Luneburg lens of the present invention;

[0013] Figure 4 The results of the differential thickness method and the equal thickness method of the present invention are shown in the figure. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] An inner focal Luneburg lens antenna based on arithmetic progression, such as Figures 1-3 As shown, a horn-shaped feed and an inner focal point Luneburg lens are used. The horn-shaped feed is located at the center of the bottom surface of the inner focal point Luneburg lens. The inner focal point Luneburg lens is characterized by being divided into ten layers using an equal thickness method, with the spherical core layer being the first layer and the outermost layer being the tenth layer. The thickness of the first layer of the inner focal point Luneburg lens is 0.4 times the radius of the entire inner focal point Luneburg lens, the thickness of the second layer is 1.6 mm, and from the third layer onwards, the thickness of each layer is d = 0.15 mm less than the thickness of the previous layer.

[0016] Since materials with a gradually changing dielectric constant do not exist in nature, current techniques involve layering a sphere to achieve a gradient dielectric constant, approximating an ideal gradient medium. Among layering techniques, the most commonly used is the equal-thickness layering method, where each layer is the same thickness. The biggest advantage of this method is its simple structure and ease of fabrication. However, this results in significant differences in the dielectric constants of the outer layers, increasing reflection loss between adjacent layers, reducing transmission efficiency, and consequently lowering gain and aperture efficiency. Because the size of circuits and electronic devices decreases dramatically in the terahertz band, reducing lens size is particularly important. However, most Luneburg lens designs currently use spherical lenses with a length, width, and height of 2R, which greatly increases the overall device size, hindering integration and increasing cost.

[0017] In this embodiment, the basic arithmetic layered inner focal Luneburg lens antenna consists of a horn feed with an operating frequency of 220 GHz and ten layers of inner focal Luneburg lenses, with the rear part of the lens focal point cut off. The feed is placed at the exact center of the bottom surface, which is also the focal point of the lens.

[0018] like Figure 3 As shown, considering the wavelength and application scenarios, the radius of this invention is set to R = 15mm. According to the definition of a generalized Luneburg lens, the focal point is designed inside the sphere, and here the focal point F = 0.6R is chosen. Since the electromagnetic wave behind the focal point F is almost negligible, the portion behind the focal point F is cut off to reduce the overall cross-sectional height and overall weight.

[0019] The internal structure is divided into ten layers using an arithmetic thickness method, with the core layer being the first layer and the outermost layer being the tenth layer. The radius and thickness of the first layer are d1 = r1 = 0.4R = 6 mm. The radius of the second layer is r2 = 7.6 mm, and the thickness is d2 = 7.6 - 6 = 1.6 mm. Starting from the second layer, the thickness of each layer decreases by d = 0.15 mm compared to the previous layer. Substituting these values ​​into the generalized Luneburg lens dielectric constant formula, the dielectric constant of each layer can be calculated. The generalized Luneburg lens dielectric constant formula is:

[0020]

[0021] In the formula, the value of r is taken as the midpoint between the radii of two adjacent layers. The dielectric constant of the core layer cannot be directly calculated using the above formula because the thickness of the core layer differs significantly from that of the second layer, resulting in a large difference in the dielectric constants of the two layers. This would increase the reflection of electromagnetic waves between layers, reducing gain and aperture efficiency. Therefore, the dielectric constant of the core layer should be slightly smaller than the calculated value. Here, ε = 3.415 is taken.

[0022] The lens structure parameters are shown in the table below:

[0023] Lens parameter table

[0024] Core layer 6 6 \ 3.42 Second floor 7.6 1.6 \ 3.21 Third layer 9.05 1.45 0.15 2.92 Fourth floor 10.35 1.3 0.15 2.62 Fifth floor 11.5 1.15 0.15 2.3 Sixth floor 12.5 1 0.15 2 Seventh floor 13.35 0.85 0.15 1.72 Eighth floor 14.05 0.7 0.15 1.46 Ninth floor 14.6 0.55 0.15 1.24 tenth floor 15 0.4 0.15 1.07

[0025] The horn is a rectangular pyramidal horn fed by a standard rectangular waveguide WR-4.3. To ensure that most of the horn's energy covers the lens, thereby improving gain and aperture efficiency, the 3dB beamwidth is designed to be between 65° and 70°. Based on the beamwidth and the pyramidal horn design formula, the horn feed parameter table is as follows:

[0026] Horn feed parameter table

[0027] Wg waveguide width 1.092 Hg waveguide height 0.546 Lg waveguide length 0.25 Lf Speaker height 0.153 Wa Diameter width 1.497 Ha Diameter Height 1.078

[0028] At a working frequency of 220 GHz, the simulation results are compared between a Luneburg lens based on equal-aperture layering (referred to as equal-aperture spherical) and an inner-focus Luneburg lens antenna (referred to as equal-aperture inner-focus) and a traditional equal-thickness layered spherical Luneburg lens (referred to as equal-thickness spherical) and an inner-focus Luneburg lens antenna (referred to as equal-thickness inner-focus). Figure 4 As shown.

[0029] The above-described embodiments further illustrate the purpose, technical solution, and advantages of the present invention. It should be understood that the above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An inner focal Luneburg lens antenna based on arithmetic progression, comprising: The horn-shaped feed and inner focal point Luneburg lens, according to the generalized definition of a Luneburg lens, shorten the focal length to the inside of the sphere and cut off the part behind the focal point. The horn-shaped feed is set at the center of the bottom surface of the inner focal point Luneburg lens. The feature is that the inner focal point Luneburg lens is divided into ten layers using an arithmetic progression method, where the sphere center layer is the first layer and the outermost layer is the tenth layer. The thickness of the first layer of the inner focal point Luneburg lens is 0.4 times the radius of the entire inner focal point Luneburg lens, and the thickness of the third to tenth layers follows an arithmetic progression, that is, it decreases from the inside to the outside. The radius and thickness of the first layer are: The radius of the second layer is taken as The thickness of the second layer Starting from the second layer, the thickness of each subsequent layer decreases compared to the previous one. Substituting these values ​​into the generalized Luneburg lens dielectric constant formula allows us to calculate the dielectric constant of each layer. The generalized Luneburg lens dielectric constant formula is as follows: ； Where n is the refractive index, Let the radius be the radius of the entire sphere. The distance from the focal point to the center of the circle. Let be the distance from any point to the center of the circle.

2. The inner focal Luneburg lens antenna based on arithmetic progression according to claim 1, characterized in that, The horn-shaped feed uses a rectangular pyramidal horn fed by a standard rectangular waveguide WR-4.

3.

3. The inner focal Luneburg lens antenna based on arithmetic progression according to claim 2, characterized in that, The horn-shaped feed operates at a frequency of 220 GHz.

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