Lightweight paper-based planar lens for electromagnetic beam steering, and planar antenna comprising same

Abstract

The present invention belongs to the technical field of antennas. Disclosed are a lightweight paper-based planar lens for electromagnetic beam steering, and a planar antenna comprising same. The planar lens comprises a paper-based main body, wherein the paper-based main body is formed in such a way that a sheet-like paper substrate encloses cavity structures, which are periodically arranged at intervals, and the paper-based main body has two opposite planes, i.e., an upper plane and a lower plane, which are respectively an incident plane and an emergent plane for electromagnetic waves; the sheet-like paper substrate, on which thin-film symbol units made of a metal material are distributed and attached; and the symbol units, wherein the metal surface area of a symbol unit per unit volume in the paper-based main body is compared, and the metal surface area per unit volume in the center of the planar lens is greater than the metal surface area per unit volume on the periphery of the planar lens. The planar antenna comprises the planar lens and a feed source, wherein the feed source is mounted close to the incident plane; and electromagnetic waves propagate in the planar lens along a curved path and are converged to be emitted out of the planar lens. In the present invention, when the feed source moves, the wide-angle scanning of beams can be realized, and within a scanning range of ±50 degrees, the gain of the planar antenna decreases by less than 2 dB.

Description

A lightweight paper-based planar lens and its planar antenna for electromagnetic wave beam modulation Technical Field

[0001] This invention belongs to the field of antenna technology, specifically relating to a lightweight paper-based planar lens and its planar antenna for electromagnetic wave beam modulation. Background Technology

[0002] With the rapid development of next-generation mobile communication technologies (B5G / 6G), there is an urgent need for antennas with large bandwidth, high gain, and wide-angle scanning. As a form of high-gain antenna, the main advantages of large-aperture lens antennas are high gain, high efficiency, and no need for a feed network, which has attracted widespread attention from academia and industry in recent years. Currently, there are two main types of classic large-aperture lens antennas: spherical Luneburg lens antennas and transmission array antennas.

[0003] The working principle of a spherical Luneburg lens antenna is to refract electromagnetic waves multiple times through a spherical multifaceted refractive lens, ultimately forming scattered light, thereby amplifying the light. For example, Chinese patent CN105917525A discloses an antenna system and processing method, which mentions that focusing equipment can use Luneburg lenses. However, commercially available Luneburg lens antennas are generally made of ceramic, but ceramics have a high dielectric constant and narrow bandwidth, making it difficult to achieve multi-band operation. Furthermore, ceramics are hard, heavy, and expensive, hindering transportation and unsuitable for industrialization. Some Luneburg lens antennas can also be made of dielectric materials such as polytetrafluoroethylene (PTFE), but their complex structure and special material requirements increase the difficulty and cost of manufacturing and maintenance, resulting in disadvantages in efficiency, structure, and cost. Moreover, the feed of a Luneburg lens can only be installed on curved surfaces, which presents significant installation challenges.

[0004] Transmission array antennas, on the other hand, achieve phase modulation of electromagnetic waves arriving at the surface through a resonant structure on the aperture plane. For example, Chinese patent CN105071051A discloses an improved Fabry-Pérot resonant cavity antenna; it includes a feed and a partial reflector. The feed is a rectangular patch antenna, and the partial reflector is placed parallel above the feed. The height of the resonant cavity formed between the feed and the partial reflector is h. The partial reflector has a double-sided cladding structure, with a periodically arranged copper array on its upper surface and a periodically arranged perforated cross-shaped copper square array on its lower surface. The partial reflector's PRS structure gives it a larger reflection coefficient modulus, which improves the gain of the feed antenna. The phase of the reflection coefficient has a positive correlation with frequency, thus improving both the impedance bandwidth and gain bandwidth. However, due to the use of a resonant structure, the operating bandwidth of the transmission array antenna is narrower.

[0005] In addition, traditional antennas have only one central focus. In order for the electromagnetic waves radiated by the antenna to be emitted in parallel, the feed source must be placed at the central focus. Once the feed source deviates from the central focus, the antenna gain will drop sharply, and the antenna beam scanning angle will also become smaller.

[0006] Therefore, how to achieve high-gain, narrow-beam, multi-beam, low-power, and lightweight lens antennas is a technical challenge that urgently needs to be studied and overcome in this field. Summary of the Invention

[0007] To address the problems in related technologies, this invention proposes a lightweight paper-based planar lens and its planar antenna for electromagnetic wave beam modulation, overcoming the aforementioned technical issues in existing technologies. The planar lens of this invention includes a paper-based body, which is formed by a sheet of paper surrounding periodically spaced hole structures. The sheet of paper has thin-film metallic symbol units attached to it. A feed source is mounted close to the surface of the paper-based body. In this invention, the feed source can be placed at any position on the incident plane. When the feed source moves, this invention can also achieve wide-angle beam scanning. Within a scanning range of ±50 degrees, the gain drop of the planar antenna is less than 2dB. Simultaneously, this invention also achieves beneficial effects such as high gain, narrow beam, multi-beam operation, low power consumption, and lightweight design.

[0008] The technical solution of the present invention is implemented as follows: a lightweight paper-based planar lens for electromagnetic wave beam modulation, comprising a paper-based body, wherein the paper-based body is formed by surrounding periodically spaced void structures with sheet-like paper, and has two opposing planes, an upper and a lower plane, which are the incident plane and the exit plane of the electromagnetic wave, respectively.

[0009] The sheet-like paper base has distributed symbol units made of thin film-like metallic material.

[0010] Furthermore, the attachment methods of the symbol units include, but are not limited to, printing and pasting.

[0011] It should be noted that: the symbol unit being attached to the surface of the sheet-like paper base, or the symbol unit being disposed inside the sheet-like paper base, also has the same technical effect.

[0012] The symbol unit is compared with the metal surface area of ​​the symbol unit per unit volume in the paper base body. The metal surface area per unit volume in the middle of the plane lens is greater than that at the periphery of the plane lens.

[0013] Furthermore, the incident plane and the exit plane are two opposing planes arranged in parallel;

[0014] The paper base body is cylindrical, polygonal, or frustum-shaped.

[0015] The cavity structure is a circular or polygonal three-dimensional columnar void structure.

[0016] Furthermore, at the location with the largest metal surface area per unit volume, the metal surface area gradually decreases in the radial direction towards the circumference; or, decreases in steps; or decreases periodically.

[0017] It should be noted that step reduction means that the reduction of the metal surface area is not a continuous and smooth decrease, but rather that there may be some obvious inflection points or plateaus during the decrease, causing the rate of decrease to slow down or stop near these points, thus forming a step-like shape.

[0018] Periodic decrease refers to the fact that during the process of decreasing the surface area of ​​the metal, its value exhibits a periodic downward trend. This periodic change usually means that within a certain fixed time interval, the value of the curve will undergo a complete rise and fall process, and this process will repeat, forming periodic fluctuations.

[0019] Furthermore, if we define the electromagnetic refractive index at the location with the largest unit volume of the metal surface area as n0, the height between the upper and lower opposing surfaces of the paper substrate as h, and the radial distance extending circumferentially around n0 as R, then the refractive index n(R) at position R follows the following distribution:

[0020] Where e is the natural constant.

[0021] It should be noted that the larger the surface area of ​​the metal, the larger the value of n0, and the larger the final refractive index n(R); however, in practical applications, the value of n0 is generally between 1 and 3. Higher values ​​of n0 can also be achieved, but it will be relatively difficult to implement.

[0022] Furthermore, the focal plane of the plane lens is located on the incident plane.

[0023] It should be noted that traditional antennas generally have only one central focal point, and the feed needs to be placed at the central focal point, extending along the central focal point and perpendicular to the optical axis to form a plane. If the feed is placed on this plane away from the central focal point, the focusing effect of the electromagnetic waves emitted by the feed will be worse. However, the entire incident plane of the planar lens described in this invention is the focal plane. The refraction effect of the electromagnetic waves emitted by the feed at any position on the focal plane is basically the same. This invention will not cause the problem of a sharp drop in antenna gain and a smaller antenna beam scanning angle.

[0024] Furthermore, the symbol unit is disposed on the sidewall surrounding and facing the cavity structure, and the unit volume covers at least one cavity structure in the planar direction and contains at least one symbol unit in the vertical direction; in this invention, it means that at least one cavity structure is included in the transverse plane of the plane lens, and at least one symbol unit is included in the vertical plane perpendicular to the transverse plane.

[0025] At least some of the hole structures have different arrangement density, size, or shape of the symbol units compared to other hole structures; it should be noted that within the same paper substrate, the symbol units of different hole structures have different characteristics; in this invention, different equivalent dielectric constants can be obtained by adjusting the symbol units.

[0026] Furthermore, the shape of each symbol unit includes an I-shape, and the equivalent dielectric constant is changed by adjusting the length of each side of the I-shape; wherein, the length of the side is positively correlated with the magnitude of the equivalent dielectric constant, that is, the longer the side is, the higher the equivalent dielectric constant.

[0027] Furthermore, the equivalent dielectric constant ranges from 1 to 2.

[0028] It should be noted that the shape of the symbol unit also includes a cross structure and a ring structure.

[0029] Furthermore, the symbol unit is made of a metal material with high conductivity.

[0030] Furthermore, the paper base material includes aramid paper.

[0031] In this invention, the paper base includes, but is not limited to, aramid paper, and the symbol unit is fixed on the aramid paper by printing or pasting.

[0032] Furthermore, the paper base can also be made of a flexible PCB board, and the symbol unit is fixed to the flexible PCB board by printing or attaching.

[0033] A planar antenna for wide-angle, high-gain beam scanning includes the aforementioned planar lens; and,

[0034] The moving feed source moves back and forth along a straight line or a plane angle and is installed close to the incident plane, with the moving trajectory extending along the incident plane; so that the reciprocating feed source can achieve the technical effect of scanning.

[0035] Electromagnetic waves propagate in a curved path within the plane lens and are collimated out of the plane lens.

[0036] A multi-beam planar antenna for high bandwidth and high gain includes the aforementioned planar lens; and,

[0037] Multiple fixed feed sources are distributed along a straight line or plane and installed close to the incident plane.

[0038] Furthermore, the output surfaces of the electromagnetic waves from each of the fixed feed sources are located at the same height;

[0039] Electromagnetic waves from different feed sources propagate in the plane lens along curved paths and are collimated at different angles to exit the plane lens.

[0040] Furthermore, the electromagnetic waves propagating inside the plane lens are all emitted outside the plane lens in the form of plane waves.

[0041] This invention achieves a multi-beam effect by simultaneously setting multiple fixed feed sources, with one fixed feed source corresponding to one beam; under the condition of multiple beams, multiple electromagnetic waves emitted at different angles will be emitted in the form of plane waves in different directions.

[0042] Furthermore, the focal plane of the planar lens is set to coincide with the incident plane, and the feed source is mounted close to the surface of the paper-based body.

[0043] It should be noted that in the prior art, the feed source of the Luneburg lens can only be installed on a curved surface, which is difficult to install on a curved surface. However, the feed source of the planar lens described in this invention is installed directly along the plane. Planar installation is simpler and more convenient than curved surface installation. Therefore, compared with the existing Luneburg lens, the planar lens of this invention is easier to install the feed source.

[0044] The gain roll-off of electromagnetic waves emitted by a feed source located at any position on the focal plane after being radiated by the planar lens is less than 2dB.

[0045] Furthermore, the antenna aperture surface refers to the cross-section of the planar antenna.

[0046] The beneficial effects of this invention are:

[0047] The planar antenna of the present invention includes a lightweight paper-based planar lens for electromagnetic wave beam modulation and a feed source, wherein the planar lens is formed by surrounding periodically spaced hole structures with a sheet of paper. Unlike spherical Luneburg lens antennas, the planar antenna of the present invention has a planar cross-section, so multiple feed sources can be placed simultaneously on the incident plane of the planar lens, making the installation of the feed sources easier.

[0048] Secondly, traditional Luneburg lens antennas are typically made by manufacturing dielectric spheres from dielectric materials such as polytetrafluoroethylene, then drilling holes in different sphere layers to obtain an equivalent artificial material Luneburg lens antenna composed of a mixture of dielectric and air. In contrast, the refractive index of the planar lens in this invention is controlled by a symbol unit attached to a sheet-like paper base, making the operation much easier.

[0049] Furthermore, the movable feed of this invention can be placed at any position on the incident plane, and multiple fixed feeds can also be placed at multiple different positions on the incident plane. Compared with a transmission array antenna, the biggest advantage of this invention is that when the feed is moved or multiple fixed feeds are set, this invention can achieve wide-angle beam scanning, and within a scanning range of ±50 degrees, the gain roll-off of the planar antenna is less than 2dB, achieving very high gain and aperture efficiency; at the same time, this invention can also achieve a multi-beam effect. Moreover, the bandwidth of the wide-angle scanning achieved by the planar antenna of this invention can reach 80%, which is much wider than the bandwidth of traditional planar transmission antennas. Attached Figure Description

[0050] Figure 1 is a schematic diagram of the basic structure of the planar lens of the present invention;

[0051] Figure 2 is a schematic diagram showing the radial decrease in refractive index on the aperture surface of the antenna of the present invention;

[0052] Figure 3 is a schematic diagram of the refractive index distribution on the aperture surface of the antenna of the present invention;

[0053] Figure 4 is a schematic diagram of the radiation trajectory of the electromagnetic wave in the plane lens according to the present invention;

[0054] Figure 5 is a schematic diagram of the symbol unit sprayed onto aramid paper according to the present invention;

[0055] Figure 6 is a top view of the planar antenna of the present invention;

[0056] Figure 7 is a side view of the planar antenna of the present invention;

[0057] Figure 8 is a schematic diagram showing the positions of the multiple fixed feed sources of the present invention on the incident plane;

[0058] Figure 9 is a schematic diagram of the gain of the planar antenna as a function of beam scanning angle under different feed excitations according to the present invention;

[0059] Figure 10 is a schematic diagram of the gain curves of the present invention with frequency for different beam scanning angles. Detailed Implementation

[0060] 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 a part of the embodiments of the present invention, and not all of them. 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.

[0061] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0062] Example 1

[0063] As shown in Figure 1, this embodiment provides a lightweight paper-based planar lens for electromagnetic wave beam modulation, including a paper-based body. The paper-based body is formed by surrounding periodically spaced hole structures with sheet-like paper and has two opposing planes, which are the incident plane and the exit plane of the electromagnetic wave, respectively.

[0064] As shown in Figures 5-7, the sheet-like paper base has distributed symbol units made of thin film-like metal material.

[0065] Specifically, the attachment methods of the symbol units include, but are not limited to, printing and pasting.

[0066] It should be noted that: the symbol unit being attached to the surface of the sheet-like paper base, or the symbol unit being disposed inside the sheet-like paper base, also has the same technical effect.

[0067] The symbol unit is compared with the metal surface area of ​​the symbol unit per unit volume in the paper base body. The metal surface area per unit volume in the middle of the plane lens is greater than that in the periphery of the plane lens. This makes the refractive index of the middle position of the plane lens greater than that in the periphery, as shown in Figure 3. The refractive index of the plane lens decreases from the middle position to both sides.

[0068] Specifically, the incident plane and the exit plane are two opposing planes arranged in parallel.

[0069] The paper base body is cylindrical, polygonal, or frustum-shaped.

[0070] It should be noted that this embodiment does not limit the shape of the paper base body. In addition to a cylindrical shape, it can also be any other three-dimensional structure. In this embodiment, a cylindrical shape is preferred. The advantage of using a cylindrical shape is that the power of the electromagnetic waves radiated from the plane lens is symmetrical in all directions.

[0071] Specifically, at the location with the largest metal surface area per unit volume, the metal surface area gradually decreases in the radial direction towards the circumference; or, decreases in steps; or decreases periodically.

[0072] It should be noted that step reduction means that the reduction of the metal surface area is not a continuous and smooth decrease, but rather that there may be some obvious inflection points or plateaus during the decrease, causing the rate of decrease to slow down or stop near these points, thus forming a step-like shape.

[0073] Periodic decrease refers to the fact that during the process of decreasing the surface area of ​​the metal, its value exhibits a periodic downward trend. This periodic change usually means that within a certain fixed time interval, the value of the curve will undergo a complete rise and fall process, and this process will repeat, forming periodic fluctuations.

[0074] Specifically, the antenna aperture surface refers to the cross-section of the planar antenna. In order to enable the planar antenna to achieve a large beam scanning angle when the subsequent feed moves on the incident plane, while ensuring that the gain does not drop significantly, a gradient refractive index is constructed on the antenna aperture surface, as shown in Figure 2-3.

[0075] More specifically, let n0 be the electromagnetic refractive index at the location with the largest unit volume of the metal surface area, h be the height between the upper and lower opposing surfaces of the paper substrate, and R be the radial distance extending circumferentially with n0 as the center. Then, the refractive index n(R) at position R follows the following distribution:

[0076] Where e is the natural constant.

[0077] It should be noted that, as shown in Figure 2, the larger the surface area of ​​the metal, the larger the value of n0, and the larger the final refractive index n(R); however, in practical applications, the value of n0 is generally between 1 and 3. Higher values ​​of n0 can also be achieved, but it will be relatively difficult to implement.

[0078] According to the above formula, the refractive index corresponding to each point on the antenna aperture surface can be calculated. The specific refractive index distribution on the antenna aperture surface is shown in Figure 3. The refractive index is the highest at the center of the antenna aperture surface, and the refractive index gradually decreases from the center along the surrounding edges.

[0079] Specifically, the focal plane of the plane lens is located on the incident plane.

[0080] It should be noted that traditional antennas generally have only one central focal point, and the feed needs to be placed at the central focal point, extending along the central focal point and perpendicular to the optical axis to form a plane. If the feed is placed on this plane away from the central focal point, the focusing effect of the electromagnetic waves emitted by the feed will be worse. However, in this embodiment, the entire incident plane of the planar lens is the focal plane. The refraction effect of the electromagnetic waves emitted by the feed at any position on the focal plane is basically the same. This embodiment will not have the problem of a sharp drop in antenna gain and a smaller antenna beam scanning angle.

[0081] Specifically, the symbol unit is disposed on the sidewall surrounding and facing the cavity structure, and the unit volume covers at least one cavity structure in the planar direction and contains at least one symbol unit in the vertical direction; in this embodiment, this means that at least one cavity structure is included in the transverse plane of the plane lens, and at least one symbol unit is included in the vertical plane perpendicular to the transverse plane.

[0082] At least some of the hole structures have different arrangement density, size, or shape of the symbol units compared to other hole structures. It should be noted that within the same paper substrate, the symbol units of different hole structures have different characteristics. In this embodiment, different equivalent dielectric constants are obtained by adjusting the symbol units.

[0083] Specifically, the symbol unit is made of a metal material with high conductivity, such as silver paste or copper, with silver paste being preferred in this embodiment.

[0084] Specifically, the paper base material includes aramid paper.

[0085] In this embodiment, the paper base includes, but is not limited to, aramid paper, and the symbol unit is fixed on the aramid paper by printing or pasting.

[0086] It should be noted that in a plane lens, the paper base mainly serves as a support, while the paper base made of aramid paper used in this embodiment has a unique spatial structure and mechanical properties; moreover, aramid paper has excellent chemical inertness, can self-extinguish immediately after leaving the fire source, and has good heat insulation, temperature resistance, electrical insulation and electromagnetic wave transmission properties.

[0087] The cavity structure is a circular or polygonal three-dimensional columnar void structure.

[0088] In this embodiment, the hole structure may specifically be a three-dimensional columnar void structure in the shape of a hexagon; the three-dimensional columnar void structure in the shape of a hexagon enables the paper-based body to have better axial compression and impact resistance, excellent sound insulation performance and fatigue resistance, and also enables the planar lens to have a lower density, so the overall mass is lighter than that of other materials; moreover, the hole structure is arranged in the shape of a hexagon, enabling subsequent electromagnetic waves to radiate in the form of plane waves, which can not only achieve large-angle radiation but also ensure that the gain does not decrease significantly.

[0089] In this embodiment, in order to achieve an equivalent gradient refractive index, the symbol units are first arranged on the sheet-like paper substrate, and then different equivalent refractive indices are achieved by adjusting the size of the symbol units.

[0090] It should be noted that: the medium in the hole structure is air, and the dielectric constant of air is 1.0, while the dielectric constant of the paper-based body is different from that of air. When it is necessary to increase the equivalent dielectric constant of the planar lens, the size of the equivalent dielectric constant can be specifically changed by adjusting the length of each side of the symbol unit.

[0091] Specifically, the shape of each of the symbol units includes an I-shaped structure, and the size of the equivalent dielectric constant is changed by adjusting the length of each side of the I-shaped structure; among them, the length of the side is positively correlated with the size of the equivalent dielectric constant, that is, the larger the length of the side, the higher the equivalent dielectric constant.

[0092] More specifically, the value range of the equivalent dielectric constant is 1 - 2.

[0093] As shown in Figure 5, in this embodiment, the equivalent dielectric constant is changed by printing an I-shaped structure on the aramid paper, and specifically, the equivalent dielectric constant is changed mainly by adjusting the length of each side of the I-shaped structure.

[0094] Specifically, the shape of the symbol unit described in this embodiment includes but is not limited to an I-shaped structure, and the shape of the symbol unit also includes a cross-shaped structure and a ring-shaped structure.

[0095] It should be noted that: in this embodiment, electromagnetic simulation software is used for simulation; according to the theory and simulation results, when the area ratio of the symbol unit to a single side wall of the hole structure is the same, no matter how the shape, density, etc. of the symbol unit change, the finally achieved equivalent dielectric constant is similar.

[0096] More specifically, the paper substrate can also be made of a flexible PCB board, and the symbol units are fixed on the flexible PCB board by printing or attaching.

[0097] Embodiment 2

[0098] This embodiment provides another lightweight paper-based planar lens for electromagnetic wave beam modulation. Features not explained in this embodiment can be explained using the methods described in Embodiment 1, and will not be repeated here. The difference between this embodiment and Embodiment 1 is as follows:

[0099] The paper base was replaced with a plastic material.

[0100] Example 3

[0101] This embodiment provides a planar antenna for wide-angle, high-gain beam scanning. Features not explained in this embodiment can be explained using the methods described in Embodiment 1, and will not be repeated here. The difference between this embodiment and Embodiment 1 is:

[0102] Including the aforementioned plane lens; and,

[0103] The moving feed source moves back and forth along a straight line or a plane angle and is installed close to the incident plane, with the moving trajectory extending along the incident plane; so that the reciprocating feed source can achieve the technical effect of scanning.

[0104] Electromagnetic waves propagate in a curved path within the plane lens and are collimated out of the plane lens.

[0105] As shown in Figure 7, the focal plane of the planar lens is set to coincide with the incident plane, and the feed source is installed close to the surface of the paper-based body to ensure that the planar antenna can achieve large-angle radiation of electromagnetic waves and high antenna gain.

[0106] As shown in Figures 8-9, regardless of where the movable feed is installed on the incident plane, the gain of the planar antenna will change as the beam scanning angle changes. Taking feed 3 in Figure 9 as an example, as the beam scanning angle of the planar lens changes from 0 degrees to ±50 degrees, the gain will periodically decrease from 20 dBi.

[0107] More specifically, the electromagnetic wave emitted by a feed source located at any position on the focal plane has a gain roll-off of less than 2dB after being radiated by the planar lens; where gain roll-off refers to the gain of different beams relative to the maximum gain of all beams.

[0108] As shown in Figure 10, the gain varies with frequency at different beam scanning angles, but within a wide frequency range of 1.8 GHz to 3.8 GHz, the gain drop at different beam scanning angles is within 2 dB. Taking a beam scanning angle of 0 degrees in Figure 10 as an example, when the frequency changes from 2.0 GHz to 2.1 GHz, the gain drop is significantly less than 2 dB. As shown in Figure 4, this embodiment illustrates the propagation path of electromagnetic waves inside the planar lens. Due to the presence of the symbol unit, after the feed source emits electromagnetic waves from different positions, they are all transmitted in a curved form to the exit plane within the planar lens. After refraction by the exit plane, they propagate outside the planar lens as plane waves. Therefore, in this embodiment, a movable feed source can be placed at any position on the incident plane, and the electromagnetic waves can ultimately be radiated out in the form of plane waves, thereby achieving large-angle radiation while ensuring that the gain does not decrease significantly.

[0109] The required refractive index on the antenna aperture surface can be calculated using the formula in Example 1. Then, by setting the corresponding refractive index symbol unit at the corresponding position, the planar antenna described in this example can be obtained.

[0110] Furthermore, in this embodiment, whether using aramid paper or flexible PCB board, both are significantly lighter than ceramics for the same volume, which helps reduce the transportation cost of the planar antenna. Moreover, for manufacturers, the larger the antenna volume, the higher the processing cost of ceramics, but the processing cost of aramid paper is lower than that of ceramics. Therefore, the planar antenna described in this embodiment is also conducive to large-scale production.

[0111] Example 4

[0112] This embodiment also provides a multi-beam planar antenna with high bandwidth and high gain. Features not explained in this embodiment can be explained using the methods in Embodiment 1, and will not be repeated here. The difference between this embodiment and Embodiments 1 and 3 is as follows:

[0113] Including the aforementioned plane lens; and,

[0114] Multiple fixed feed sources are distributed along a straight line or a plane and installed close to the incident plane;

[0115] Electromagnetic waves from different feed sources propagate in the plane lens along curved paths and are collimated at different angles to exit the plane lens.

[0116] Specifically, electromagnetic waves propagating inside the plane lens are emitted outside the plane lens in the form of plane waves.

[0117] This embodiment achieves the effect of multiple beams by setting multiple fixed feed sources simultaneously, with one fixed feed source corresponding to one beam; under the condition of multiple beams, multiple electromagnetic waves emitted at different angles will be emitted in the form of plane waves in different directions.

[0118] Specifically, the focal plane of the planar lens is set to coincide with the incident plane, and the feed source is mounted close to the surface of the paper-based main body to ensure that the multi-beam planar antenna can achieve large-angle electromagnetic wave radiation and high antenna gain.

[0119] It should be noted that in the prior art, the feed source of the Luneburg lens can only be installed on a curved surface, which is difficult to install on a curved surface. However, the feed source of the planar lens described in this embodiment is installed directly along the plane. Planar installation is simpler and more convenient than curved surface installation. Therefore, compared with the existing Luneburg lens, the planar lens of this embodiment is easier to install the feed source.

[0120] As shown in Figures 8-9, multiple fixed feed sources are installed at arbitrary positions on the incident plane. When the beam scanning angle of the planar antenna changes, the gain will also change accordingly. Taking feed source 3 in Figure 9 as an example, as the beam scanning angle changes from 0 degrees to ±50 degrees, the gain will also decrease periodically from 20dBi.

[0121] More specifically, the gain roll-off of electromagnetic waves emitted by a feed source located at any position on the focal plane after being radiated by the planar lens is less than 2dB.

[0122] As shown in Figure 10, the gain of different beam scanning angles varies with frequency, but in the wide frequency range of 1.8 GHz to 3.8 GHz, the gain drop of different beam scanning angles is within 2 dB. Taking the beam scanning angle of 0 degrees in Figure 10 as an example, when the frequency changes from 2.0 GHz to 2.1 GHz, the gain drop is significantly less than 2 dB.

[0123] The multi-beam planar antenna in this embodiment includes a lightweight paper-based planar lens for electromagnetic wave beam tuning and multiple fixed feed sources. These fixed feed sources can be arbitrarily placed at different positions on the incident plane. Compared to a transmission array antenna, the biggest advantage of this embodiment is that, when multiple fixed feed sources are set, the multi-beam planar antenna can achieve wide-angle scanning of multiple beams. Within a scanning range of ±50 degrees, the gain roll-off of the multi-beam planar antenna is less than 2dB, while also achieving very high gain and aperture efficiency. The wide-angle scanning bandwidth achieved by the multi-beam planar antenna in this embodiment can reach 80%, far exceeding the bandwidth of traditional planar transmission antennas.

[0124] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A lightweight paper-based planar lens for electromagnetic wave beam modulation, comprising a paper-based body, characterized in that, The paper-based body is formed by surrounding periodically spaced void structures with sheet-like paper bases. It has two opposing planes, an upper plane and an lower plane, which are the incident plane and the exit plane of electromagnetic waves, respectively. The sheet-like paper base has distributed symbol units made of thin film-like metallic material attached to it; The symbol unit is compared with the metal surface area of ​​the symbol unit per unit volume in the paper base body. The metal surface area per unit volume in the middle of the plane lens is greater than that at the periphery of the plane lens.

2. The lightweight paper-based plane lens for electromagnetic wave beam modulation according to claim 1, characterized in that, The incident plane and the exit plane are two opposing planes arranged in parallel. The paper base body is cylindrical, polygonal, or frustum-shaped. The cavity structure is a circular or polygonal three-dimensional columnar void structure.

3. The lightweight paper-based plane lens for electromagnetic wave beam modulation according to claim 1, characterized in that, At the location with the largest metal surface area per unit volume, the metal surface area gradually decreases radially towards the circumference; or, decreases in steps; or decreases periodically.

4. The lightweight paper-based plane lens for electromagnetic wave beam modulation according to claim 1 or 3, characterized in that, Let n0 be the electromagnetic refractive index at the location with the largest unit volume of the metal surface area, h be the height between the upper and lower opposing surfaces of the paper substrate, and R be the radial distance extending circumferentially from n0. Then the refractive index n(R) at position R follows the following distribution: Where e is the natural constant.

5. The lightweight paper-based plane lens for electromagnetic wave beam modulation according to claim 1, characterized in that, The focal plane of the plane lens is located at the incident plane.

6. The lightweight paper-based plane lens for electromagnetic wave beam modulation according to claim 1 or 2, characterized in that, The symbol unit is disposed on the sidewall surrounding and facing the cavity structure, and the unit volume covers at least one cavity structure in the planar direction and contains at least one symbol unit in the vertical direction; The arrangement density, size, or shape of the symbol units within at least part of the cavity structure differs from that of another part of the cavity structure.

7. The lightweight paper-based plane lens for electromagnetic wave beam modulation according to claim 1, characterized in that, The paper base material includes aramid paper.

8. A planar antenna for wide-angle, high-gain beam scanning, characterized in that, Including the plane lens as described in any one of claims 1-7; and, The mobile feed source moves back and forth along a straight line or a plane angle, is installed close to the incident plane, and its movement trajectory extends along the incident plane. Electromagnetic waves propagate in a curved path within the plane lens and are collimated out of the plane lens.

9. A multi-beam planar antenna for high bandwidth and high gain, characterized in that, Including the plane lens as described in any one of claims 1-7; and, Multiple fixed feed sources are distributed along a straight line or a plane and installed close to the incident plane; Electromagnetic waves from different feed sources propagate in the plane lens along curved paths and are collimated at different angles to exit the plane lens.

10. The planar antenna according to claim 8 or 9, characterized in that, The focal plane of the planar lens is set to coincide with the incident plane, and the feed source is mounted close to the surface of the paper-based body; The gain roll-off of electromagnetic waves emitted by a feed source located at any position on the focal plane after being radiated by the planar lens is less than 2dB.

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