CN113991316A

CN113991316A - Artificial dielectric material and focusing lens made of same

Info

Publication number: CN113991316A
Application number: CN202111240771.4A
Authority: CN
Inventors: 李梓萌
Original assignee: Guangzhou Sinan Technology Co ltd
Current assignee: Guangzhou Sinan Technology Co ltd
Priority date: 2021-10-25
Filing date: 2021-10-25
Publication date: 2022-01-28

Abstract

The invention discloses an artificial dielectric material, which comprises a plurality of sheets stacked together and having a density of less than 100kg/m³And a plurality of short conductive tubes disposed in holes formed in the plurality of pieces of foam dielectric material, wherein the plurality of pieces of foam dielectric material comprising the short conductive tubes disposed in the holes are separated by the plurality of pieces of foam dielectric material that are free of the short conductive tubes.

Description

Artificial dielectric material and focusing lens made of same

Technical Field

The invention relates to an artificial dielectric material and a focusing lens made of the artificial dielectric material and used for focusing electromagnetic waves in a radio frequency band.

Background

The modern mobile communication market requires multi-beam antennas that create narrow beams and operate in different frequency bands. The focusing dielectric lens is a major component of most high efficiency multi-beam antennas. The diameter of the focusing lens must be a few wavelengths of the operating frequency creating a narrow beam, and therefore, the diameter of some lenses of multi-beam antennas for mobile communications is greater than 1 m. Such lenses made of common dielectric materials are too heavy and therefore much research has been done to create lighter and low loss lenses.

Most known lightweight artificial dielectric materials consist of randomly oriented conductive portions with non-conductive portions made of lightweight dielectric materials. It is very difficult to produce a homogeneous material with the desired dielectric properties by randomly mixing conductive and non-conductive parts, and therefore the focusing lens is the most expensive component of a multibeam antenna. The development of focusing lenses of such materials for improved performance and reduced cost is continuing.

Us patent 8518537B2 describes a lightweight artificial dielectric material comprising a plurality of randomly oriented small particles of lightweight dielectric material, such as polyethylene foam containing conductive fibers disposed in each particle.

Patent application US 2018/0034160 a1 describes a lightweight artificial dielectric material comprising a plurality of randomly oriented small multi-layered particulate lightweight dielectric materials, which comprise inter-layer thin conductive sheets. As written herein, such multilayer particles provide a greater dielectric constant than particles comprising conductive fibers.

Patent application US 2018/0279202 a1 describes other classes of lightweight artificial dielectric materials comprising a plurality of randomly oriented small particles. One material described is a small multi-layer particle lightweight dielectric material comprising an interlayer thin conductive sheet.

All of the above lightweight artificial dielectric materials are made by randomly mixing small particles. There is a need to eliminate metal-to-metal contacts in the material that would result in passive intermodulation distortion, and therefore, the manufacture of such materials involves many stages and is costly.

Random mixing provides isotropy in the final material, which is composed of small particles, but some applications require dielectric materials with anisotropy. For example, a cylindrical lens made of an anisotropic dielectric material can reduce depolarization of electromagnetic waves passing through the cylindrical lens and improve the cross polarization ratio of a multibeam antenna (us patent 9819094B 2). A cylindrical lens made of isotropic artificial dielectric material creates a depolarization of the electromagnetic waves passing through the lens, so that an antenna comprising the lens is able to withstand higher cross-polarization levels. Thus, there is a need for lightweight dielectric materials that provide desirable properties including anisotropy.

Disclosure of Invention

It is a first object of the present invention to overcome the disadvantages of the known lightweight artificial dielectric materials and to provide a lightweight artificial dielectric material which is easier to manufacture than the known equivalent and which is suitable for producing focusing lenses and dielectric antennas for radio communication.

Accordingly, provided herein is an artificial dielectric material comprising a plurality of sheets stacked together and having a density of less than 100kg/m³And a plurality of placementsA short conductive tube in a hole formed in the plurality of pieces of foam dielectric material, wherein the plurality of pieces of foam dielectric material comprising the short conductive tube disposed in the hole are separated by the plurality of pieces of foam dielectric material that do not comprise the short conductive tube.

A cylindrical focusing lens made of the described artificial dielectric material is also provided.

The material provided must provide the desired dielectric properties as well as reliable insulation between the conductive particles.

The present invention provides a lightweight artificial dielectric material comprising a plurality of short conductive tubes having thin walls and disposed in a lightweight dielectric material. The cross-section of the tube may be circular or polygonal, such as square, hexagonal or octagonal. Short conductive tubes are placed in the layers. One layer comprises a sheet of lightweight dielectric material containing a plurality of pores. The lightweight dielectric material may be a foamed polymer. The tube is placed in a hole formed in a sheet of lightweight dielectric material and contains the air inside the tube. The layers containing the tubes are separated by layers made of a lightweight dielectric material that is free of tubes. The separation layer may also contain holes having a diameter smaller than the diameter of the holes for the tubes, in order to provide ventilation by the lightweight dielectric material. The tubes placed in adjacent layers may be stacked on the same axis or displaced from each other and have different axes.

The diameter of the conductive tube is about 20 times smaller than the operating frequency wavelength to provide an acceptable dependence of the artificial dielectric material with frequency. The length of the conductive tube may be 0.2-5.0 of its respective diameter, depending on the desired properties of the artificial dielectric material.

The density of the artificial dielectric material provided depends primarily on the weight of the tube and the density of the lightweight dielectric material. The density of the polyethylene foam is in the range of 40-100kg/m 3. The density of the aluminum pipe having a diameter of 6mm and a wall thickness of 0.1mm was 180kg/m 3. The artificial dielectric material comprising such a tube and polyethylene foam is provided with a density of about 140kg/m3 and a dielectric constant (Dk) of about 1.7 when the distance between the tube and the layer is about 1 mm. By reducing the wall thickness of the conductive tube, it is possible to reduce the density of the artificial dielectric material provided. Sputtering or chemical deposition of a conductive material onto the walls of holes formed in a dielectric material can provide conductive tubes with wall thicknesses of less than 0.01 mm.

The Dk of the provided artificial dielectric material depends on the shape of the tubes, the distance between the tubes and the distance between the layers. Its Dk also depends on the polarization and direction of the electromagnetic wave propagating through the material. Thus, the provided artificial dielectric material is mainly anisotropic material, but it may also provide isotropy. For example, Dk does not depend on polarization when the electromagnetic wave crosses the material along the axis of the stub, and when the distances between stubs disposed in one layer are equal.

Dk depends on polarization when the electromagnetic wave crosses the provided material in a direction perpendicular to the stub axis. A large Dk, which is polarization dependent, occurs when the distance between the short tubes arranged in one layer is significantly smaller or larger than the distance between the layers. When the distance between the stubs disposed at one level is significantly greater than the distance between the levels, Dk for the E-polarization oriented along the axis of the stub is greater than Dk for the E-polarization oriented through the axis of the stub. When the distance between the stubs disposed at one level is significantly less than the distance between the levels, Dk for E-polarization along the axis of the stub is less than Dk for E-polarization through the axis of the stub. This material is capable of transferring linearly polarized electromagnetic waves to circularly polarized electromagnetic waves.

When the distance between the stubs arranged in one layer is approximately equal to the distance between the layers, Dk for both polarizations may be equal or slightly different.

Thus, the materials provided may be used in a variety of applications.

The repeatability of the Dk of the material provided depends on how correctly the stub and the distance between the stubs are manufactured on the production line. Several samples of the provided material were assembled using a 6mm diameter and 6mm length punch. The holes in the pieces of polyethylene foam are formed by laser cutting. Dk measured 1.68 +/-0.006. Thus, the dielectric properties of the provided material are very repeatable. Other known techniques may also be used for the production of the tubes and associated lightweight dielectric materials.

It is a second object of the present invention to provide a focusing lens made of the provided artificial dielectric material. The short tubes placed in one layer may form a structure that provides the desired Dk distribution along the layer, and thus different kinds of focusing lenses may be made from the artificial dielectric material provided. For example, cylindrical lenses can be made from wafer lightweight dielectric materials stacked together and containing short conductive tubes. Several embodiments of cylindrical lenses described below show different Dk distributions of the light dielectric material along the wafer. The process of making such lenses does not include mixing of small parts. The structure of the artificial dielectric material provided eliminates migration and settling of the conductive tube under vibration and other environmental factors that provide long term physical stability and lens performance. This is a first advantage of the provided artificial dielectric material.

Reliable insulation of the conductive tube by the lightweight dielectric material eliminates the possibility of metal-to-metal contacts that would cause passive intermodulation distortion. The provided artificial dielectric material is therefore suitable for manufacturing lenses for base station antennas, which are subject to very strict specifications for passive intermodulation distortion. This is a second advantage of the provided artificial dielectric material.

The provided artificial dielectric material can provide a uniformly variable Dk along the layer Dk. This is a third advantage of the provided artificial dielectric material.

The artificial dielectric material provided can be made with ventilation channels, so that high power electromagnetic waves can be focused by a lens made of such artificial dielectric material. This is a fourth advantage of the provided artificial dielectric material.

Drawings

Fig. 1a-1f show top views of a layer containing differently shaped tubes and forming different structures according to several embodiments of the present invention.

Fig. 2a and 2b show the mutual arrangement of circular tubes placed in two layers displaced from each other.

Fig. 3a shows a top view of an even number of layers of cylindrical lenses comprising circular tubes placed in holes formed in a lightweight dielectric material.

Fig. 3b shows a top view of an odd number of layers of cylindrical lenses made of a lightweight dielectric material.

Fig. 3c shows a top view of an odd number of layers of cylindrical lenses made of a lightweight dielectric material with holes for ventilation.

Fig. 3d shows a cross-section of a cylindrical lens comprising 8 layers with a circular tube and 9 layers without a tube.

Fig. 3e shows a cross section of a cylindrical lens comprising 8 layers with circular tubes and 9 layers with holes for ventilation.

Fig. 3f shows a cross-section of a cylindrical lens comprising 9 layers without tube and 8 layers with a circular tube, wherein layers 4, 8, 12 and 16 are rotated 30 degrees around the axis of the cylinder from layers 2, 6, 10 and 14.

Fig. 3g shows the mutual position of the tubes placed in

layers

2 and 4.

Figures 4a and 4b show another embodiment of the invention in which two adjacent layers of lightweight dielectric material are made to contain the entire piece 5 of the tube 1.

Fig. 5 shows a layer of cylindrical lenses comprising equal tubes forming three regions providing different Dk.

Figure 6 shows a layer of cylindrical lenses containing equal tubes placed along the radius of the cylinder. The distance between the tubes increases towards the edge of the cylinder (providing a Dk that decreases towards the edge of the cylinder).

Fig. 7 shows a layer of cylindrical lenses comprising tubes with three different diameters and forming three regions providing different Dk.

Detailed Description

The present invention provides a lightweight artificial dielectric material comprising a plurality of short conductive tubes having thin walls and disposed in a lightweight dielectric material. Short conductive tubes are placed in the layers. One layer comprises a sheet of lightweight dielectric material containing a plurality of pores. Short conductive tubes are placed in holes formed in a sheet of lightweight dielectric material and contain air in the tubes. The layers comprising the tube are separated by a layer of lightweight dielectric material that is free of the tube.

This structure delays the passing electromagnetic waves and acts as a dielectric material when the dimensions of the conductive tube are much smaller than the wavelength.

Some embodiments of the invention that incorporate differently shaped tubes and form different structures are shown in fig. 1a-1 f.

Fig. 1a shows a top view of a layer comprising round tubes placed in rows, wherein the distance between the tubes arranged in adjacent rows is equal to the distance between adjacent tubes in a row.

Figure 1b shows a top view of a layer comprising round tubes placed in a row, which are displaced by half the distance between adjacent tubes placed in a row, and the distance between any adjacent tubes is equal. This configuration provides a larger Dk value than the configuration in fig. 1a if both structures have equal inter-tube gaps.

FIG. 1c shows a top view of a layer comprising square tubes placed in rows, wherein the distance between tubes arranged in adjacent rows is equal to the distance between adjacent tubes in a row. Square tubes can provide a greater Dk value than round tubes, but their weight is also greater.

FIG. 1d shows a top view of a layer comprising square tubes placed in rows, the square tubes being displaced by half the distance between adjacent tubes placed in a row, and the distance between any adjacent tubes being equal.

Figure 1e shows a top view of one layer containing tubes having a hexagonal cross-section and placed at a position providing equal distance between any edges of any adjacent tubes.

Fig. 1f shows a top view of a layer comprising tubes having an octagonal cross-section placed in rows, wherein the distance between the tubes arranged in adjacent rows is equal to the distance between adjacent tubes in a row.

Tubes having any other cross-sectional shape may also be used to make the artificial dielectric material. Artificial dielectric materials comprising tubes of only one size are easiest to produce, but for some applications the material may comprise tubes of different sizes to provide the desired dielectric properties.

Figure 2a shows a circular tube comprising two layers of circular tubes placed as shown in figure 1a, wherein the top layer is displaced along and perpendicular to the rows by half the distance between adjacent tubes placed in a row.

Figure 2b shows a top view of two layers comprising round tubes placed as shown in figure 1b, wherein the top layer is displaced along the rows by half the distance between adjacent tubes placed in a row and perpendicular to the rows by a distance such that the distance between the axis of a tube placed in the top layer and the axis of three adjacent tubes placed in the bottom layer is equal. The displacement of adjacent layers reduces the dependence of Dk on the direction of electromagnetic waves propagating perpendicular to the tube axis.

Figures 3a-3g illustrate some embodiments of cylindrical lenses made from the provided lightweight artificial dielectric materials.

Figure 3a shows a top view of an even number of layers comprising round tubes 1 placed in holes formed in a circular piece of lightweight dielectric material 2. The tube 1 contains air 3 therein.

Fig. 3b shows a top view of an odd number of layers made of light dielectric material without a tube.

Figure 3c shows a top view of an odd number of layers made of a lightweight dielectric material with holes 4 (having a smaller diameter than the holes for the tubes).

Fig. 3d shows a cross-section of a cylindrical lens comprising 8 layers with round tubes placed as shown in fig. 3a and 9 layers without the tubes shown in fig. 3 b.

Fig. 3e shows a cross-section of a cylindrical lens comprising 8 layers with the circular tube shown in fig. 3a and 9 layers with the hole 4 shown in fig. 3 c. The holes 4 and the tubes 1 form a vertical passage for ventilation, so that high power electromagnetic waves can be focused by such a lens made of the provided lightweight dielectric material.

Figure 3f shows a cross-section of a cylinder comprising 8 layers with the round tube of figure 3a and 9 layers without the tube of figure 3 b. Layers 4, 8, 12 and 16 are rotated about the axis of the cylinder by 30 degrees with respect to layers 2, 6, 10 and 14.

Fig. 3g shows the mutual position of the tubes placed in

layers

2 and 4.

Adjacent layers containing the tube are rotated 30 degrees with respect to each other, thereby reducing the dependence of Dk on the azimuthal angle of the electromagnetic wave across the lens in a direction perpendicular to the cylindrical axis.

Figures 4a and 4b show another embodiment of the invention in which two adjacent layers of a lightweight dielectric material are made to contain the entire piece 5 of the tube 1. This shape of the mating lightweight dielectric material reduces the number of dielectric parts and simplifies assembly of the focusing lens.

Other embodiments of the invention showing different configurations of the short tubes forming one layer of cylindrical lenses are shown in fig. 5-7.

Fig. 5 shows one layer with equal tubes forming three regions providing different Dk.

The first area is the circle in the middle. The second area is the first ring which is placed nearly round. The third zone is a second ring positioned proximate to the first ring. The distance between the tubes of the circles is smaller than the distance between the tubes of the first ring, and the distance between the tubes of the first ring is smaller than the distance between the tubes of the second ring. Therefore, Dk of the first region is larger than Dk of the second region, and Dk of the second region is larger than Dk of the third region.

Figure 6 shows one layer with equal tubes placed radially. The distance between the tubes increases towards the edge of the cylinder (providing a Dk that decreases towards the edge of the cylinder).

Figure 7 shows a layer comprising a circular tube having three different sizes and forming three regions providing different Dk's. The first zone is the circle in the middle and contains the large size tubes. The second zone is the first ring placed close to the circle and contains the middle size tube. The third zone is a second ring placed close to the first ring and containing small sized tubes. The distance between the tubes of the circles is smaller than the distance between the tubes of the first ring, and the distance between the tubes of the first ring is smaller than the distance between the tubes of the second ring. Therefore, Dk of the first region is larger than Dk of the second region, and Dk of the second region is larger than Dk of the third region.

A focusing lens that focuses a planar electromagnetic wave at one focal point may also be made of multiple layers having different diameters. In this type of lens, the electromagnetic wave propagates along the axis of the tube placed in layers.

Claims

1. An artificial dielectric material comprising a plurality of sheets stacked together and having a density of less than 100kg/m³And a plurality of short conductive tubes disposed in holes formed in the plurality of pieces of foam dielectric material, wherein the plurality of short conductive tubes including the plurality of short conductive tubes disposed in the holesThe pieces of foamed dielectric material are separated by pieces of foamed dielectric material that are free of the short conductive tubes.

2. The artificial dielectric material of claim 1, wherein the short conductive tube is circular or polygonal in cross-section.

3. The artificial dielectric material of claim 1, wherein the short conductive tube is made of aluminum.

4. The artificial dielectric material of claim 1, wherein the short conductive tube is made by sputtering conductive material on the walls of the hole formed in the foamed dielectric material.

5. The artificial dielectric material of claim 1, wherein the short conductive tube is made by chemical deposition of a conductive material on the walls of the pores formed in the foamed dielectric material.

6. The artificial dielectric material of claim 1, wherein the lengths of the short conductive pipes are 0.2-5.0 of their respective diameters.

7. The artificial dielectric material of claim 1, wherein the foamed dielectric material is a foamed polymer.

8. The artificial dielectric material of claim 7, wherein the foamed polymer is made of a material selected from the group consisting of: polyethylene, polystyrene, polypropylene, polyurethane, silicon, and polytetrafluoroethylene.

9. The artificial dielectric material of claim 8, wherein the pieces of foamed polymer not comprising the short conductive tubes comprise holes that provide ventilation through the material.

10. The artificial dielectric material of claim 1, wherein the pieces of foamed dielectric material that comprise the short conductive pipes and the pieces of foamed dielectric material that do not comprise the short conductive pipes are made as thin sheets containing gaps of short conductive pipes, the gaps being disposed on one surface of the thin sheets.

11. The artificial dielectric material of claim 1, wherein the short conductive tubes placed in a layer form a square structure that provides equal distance between adjacent tubes disposed in the same row or column.

12. The artificial dielectric material of claim 1, wherein the short conductive tubes placed in a layer form a honeycomb structure that provides equal distance between any adjacent tubes.

13. The artificial dielectric material of claim 1, wherein the short conductive pipes placed in even layers are disposed on the same longitudinal axis as the short conductive pipes placed in odd layers.

14. The artificial dielectric material of claim 1, wherein the short conductive pipes placed at even layers are displaced along the layers relative to the short conductive pipes placed at odd layers.

15. A cylindrical focusing lens made of the artificial dielectric material according to any one of claims 1-14.

16. A cylindrical focusing lens made of the artificial dielectric material of claim 15, wherein the short conductive tubes placed in a layer and having the same dimensions form a circular middle region and at least one annular region surrounding the middle region, the distance between the short conductive tubes in the annular region being greater than the distance between the short conductive tubes in the middle region.

17. A cylindrical focusing lens made of the artificial dielectric material of claim 15, wherein the short conductive pipes of even and odd layers are displaced from each other by 30 degrees around the axis of the cylindrical focusing lens, the short conductive pipes placed in one layer and having the same size form a circular middle region and at least one annular region surrounding the middle region, the distance between the short conductive pipes in the annular region being greater than the distance between the short conductive pipes in the middle region.

18. A cylindrical focusing lens made of the artificial dielectric material of claim 15, wherein the short conductive tubes placed in a layer form a circular middle region and at least one annular region surrounding the middle region, the diameter of the short conductive tubes in the annular region being smaller than the diameter of the short conductive tubes in the middle region.

19. A cylindrical focusing lens made of the artificial dielectric material of claim 15, wherein the short conductive tubes placed in one layer are radially arranged and the distance between the short conductive tubes increases towards the outer contour of the lens.