TECHNICAL FIELD

The present disclosure relates to an antenna array having inverted antenna elements and a method for manufacturing an antenna array having inverted antenna elements.

BACKGROUND

Antennas are known in the art and used to convert radio frequency fields into alternating current or converting alternating current in to radio frequency. Antenna arrays with a set of two or more antenna elements are commonly used in various applications to combine or process signals from the antenna array in order to achieve improved performance over that of a single antenna. For instance they are able to match a radiation pattern to a desired coverage area, changing radiation pattern, adapting to changing signal conditions and some configurations can cover a large bandwidth. Antenna arrays can be described by their radiation patterns and by the type of antenna elements in the system.

Thus, antenna elements can be manufactured in different forms and types. The antenna arrays currently on the market are usually manufactured in several steps usually comprising complex and costly processes since the antenna elements can have forms that are difficult and time-consuming to realize. Further, antenna arrays may also be heavy in weight which limits their appliances considerably. For instance, antennas used in small sized unmanned aerial vehicles are demanded to be of low-weight. However, in some applications the array antenna may require small mechanical dimensions which makes it increasingly challenging to manufacture. Other, requirements in today’s antenna arrays are for them to be cost- efficient without having a trade-off for the robustness and stability of the antenna array.

There is room for antenna arrays in the present art to explore the domain of providing an antenna array with high robustness combined with a simplicity in design and manufacturing. There is specifically room in the present art of how to improve the manufacturing of antenna arrays to be able to provide antenna arrays with reduced weight, being cost-efficient and having simplified manufacturing. Accordingly, there is a need for improvements in the art to provide means for such antenna arrays.

US2017331199 discloses an antenna which comprises a ground plane and at least a first and a second antenna element. Each antenna element comprises a feed point, a cavity, a main body, a tip and at least a first tapered portion and a second tapered portion. Each antenna element is arranged on the ground plane, where said first and second tapered portions extend along the antenna element from said tip towards the ground plane of the antenna element. Each antenna element has at least a first leg and a second leg, where said first leg extends from said main body to the first feed point, where said feed point is located between the first leg and the ground plane, and where said second leg extends from said main body to the ground plane, and where said second leg is electrically connected to the ground plane.

Thus, even though previous solutions work well in some situations it would be desirable to provide an antenna array that address requirements related to improving the cost-efficiency, weight and the manufacturing of antenna arrays, hence there is still a need for further improvements.

SUMMARY

It is therefore an object of the present invention to provide an antenna array and a method for manufacturing an antenna array to mitigate, alleviate or eliminate one or more of the above- identified deficiencies and disadvantages.

This object is achieved by means of providing an antenna array as defined in the appended claims.

The present disclosure is at least partly based on the insight that by providing an alternative antenna array the antenna will be more robust, cost-efficient and have a lower weight. In accordance with the invention there is provided a method for manufacturing an antenna array according to claim 1 and an antenna array according to claim 11.

The present disclosure provides a method for manufacturing an antenna array having inverted antenna elements, comprising the steps of: providing a three dimensional block of dielectric; forming a plurality of cavities on a first surface of the block of dielectric, wherein the cavities extend essentially perpendicular to the first surface into the block of dielectric; providing at least the plurality of cavities on the first surface with an electrically conductive coating having a thickness, forming inverted antenna elements; wherein said inverted antenna elements are adapted to be coupled to an antenna feed system.

The cavities may be formed by any suitable hole-making operation. The electrically conductive coating may be a metal. In other words, the first surface may be metallized. The three dimensional block of dielectric may be a flexible dielectric.

A benefit of the method is that it allows for a fast and cheap manufacturing of antenna elements. Further, since the antenna elements are formed by a conductive coating a formed cavity in the block of dielectric, it allows for manufacturing of antenna elements having small dimensions without resulting in any delays in the manufacturing process. The method as disclosed herein of forming antenna elements that are incorporated in a block of dielectric further allows for a higher durability of the antenna elements compared to other solutions. Another benefit is that inverted antenna elements may be easier adapted compared to other solutions to fit electronics in an antenna array such as the feeding line, making the overall front-end more compact. Further, the inverted antenna elements may have a better performance compared to other solutions since the front-end electronics of the antenna array might be placed close to the antenna elements.

The plurality of cavities may be BoR shaped-cavities extending in a tapered manner, forming BoR-shaped antenna elements. BoR antenna elements may cover a large bandwidth. Accordingly, the method provides for a rapid manufacturing of antenna elements covering a large bandwidth. A BoR antenna element adapted to cover a high frequency will have shrinking mechanical dimensions and may be challenging to manufacture. The physical size of a BoR antenna element is determined by the frequency band of operation. Accordingly, the physical size of a BoR antenna element scale inversely with frequency. Further, a BoR antenna element adapted to high frequencies will be challenging to manufacture due to it having small mechanical dimensions. However, the manufacturing method according to the disclosure allows for a fast and convenient manufacturing of BoR antenna elements also for high frequencies. Further, the inverted BoR may achieve an increased durability, in other words, by having the BoR antenna elements incorporated and manufactured in a block of dielectric, the BoR antenna elements allow for increased durability. The BoR antenna elements may be manufactured despite shrinking mechanical dimensions giving increasing manufacturing tolerances, this may open for new appliances of the BoR antenna elements allowing them to be applied to low-cost and huge-volume markets such as telecom. The weight of the inverted antenna elements may be low given that the inverted antenna elements mainly uses a dielectric, having electrically conductive coatings.

The method may further comprise the step of assembling a feeding system on the first surface of the block of dielectric. A benefit of this is that the feeding system and the antenna elements may be manufactured independently and be assembled in a last step. Further, the first surface of the block of dielectric is the surface that is modified in order to provide the block of dielectric with antenna elements. Hence, the manufacturing method as disclosed herein allows for coupling of the feeding system to the inverted antenna elements, wherein a first antenna array may adapt its first surface to a first feeding system, wherein a second antenna array may adapt its first surface to a second feeding system.

The electrically conductive coating may comprise a minimum thickness being at least within the range of 0.2pm-8pm on a frequency band within the range of 100MHz-50GHz. Hence, the electrically conductive coating may be held with a low thickness while not suffering any current loss, avoiding harming the functioning of the inverted antenna elements. In other words, the minimal thickness of the electrically conductive coating may be at least within the range of 0.2pm-8pm on a frequency band within the range of 100MHz-50GHz. A benefit of having a minimum thickness being within the range of 0.2pm-8pm is that the weight of the inverted antenna elements may be kept low by having a lower thickness of the electrically conductive coating. The skin depth of the antenna element may be at least within the range of 0.2pm-8pm on a frequency band within the range of 100MHz-50GHz.

The method may further comprise the step of forming a second surface on said block of dielectric so as to fit in a radome or any other type of enclosure, wherein the second surface of said block of dielectric is the opposing surface of the first surface. Antenna arrays are often enclosed in a radome that protects the antenna from the environments. The antenna array and the radome are typically designed separately, often by different suppliers which might result in a design that is hard to put the antenna array in. Accordingly, the present disclosure provides inverted antenna elements that are incorporated in the block of dielectric, wherein the second surface of the block of dielectric may be formed to be adapted to fit in a radome. The dielectric may act as a supporting structure for a radome. Further, the dielectric may function as a radome.

Inverted antenna elements provide a benefit of in a simple manner being able to be fit in a block of dielectric.

The plurality of cavities may be formed by at least one of drilling, casting, milling or additive manufacturing. The plurality of cavities may be formed by a drill, wherein the drill comprises a drill bit having the shape of an antenna element. The drill bit may be adapted to form the shape of a BoR antenna element.

The electrically conductive coating may be deposited fully on the first surface. However, the method may further comprise the step of removing at least a part of the electrically conductive coating in-between the plurality of cavities on the first surface of said block of dielectric. In other words, residual conductive coating deposits in between the antenna elements may be removed. According to some embodiments a part of the conductive coating deposits in-between the antenna elements may be removed. The removal of the electrically conductive coating may allow for a lower weight and for adaptation of the inverted antenna elements to the feeding system.

The inverted antenna elements may be hollow. However, the method may further comprise the step of at least partially filling the plurality of cavities with a filling material after the conductive coating has been provided. This may provide for increased rigidity and a better reliability in different environments of the inverted antenna elements. Thus, the inverted antenna elements may avoid problems arising due to environmental factors. The inverted antenna elements may avoid deformation of the antenna elements or other implications that may arise in different environments such as change in ambient temperature and/or pressure.

The method may further comprise a block of dielectric having a relative permittivity within the range of 1-5. The block of dielectric may have a high relative permittivity in order to reduce the physical size of the antenna elements. The higher relative permittivity of the block of dielectric, the smaller antenna elements. However, a high relative permittivity might result in reduced operational bandwidth of the antenna.

The block of dielectric may have a relative permittivity and/or permeability which varies across the body of the block of dielectric. This may allow for antenna pattern optimization.

There is further provided an antenna array having inverted antenna elements comprising; a three dimensional block of dielectric forming a plurality of cavities on a first surface of the block of dielectric, wherein the cavities extend essentially perpendicular to the first surface into the block of dielectric, wherein at least said plurality of cavities on the first surface comprises an electrically conductive coating having a thickness t forming inverted antenna elements, wherein said inverted antenna elements are adapted to be coupled to an antenna feed system.

The plurality of cavities may be BoR shaped, forming BoR shaped antenna elements. The antenna array may further comprises a feeding system on said first surface of said block of dielectric.

The electrically conductive coating may comprise a thickness t being at least within the range of 0.2 pm-8 pm on a frequency band within the range of 100 MHz-50 GHz. The second surface of said block of dielectric may be formed to be adapted to fit in a radome or any other type of protective enclosure.

The block of dielectric has a permittivity and/or permeability which varies across the body of the block of dielectric.

The antenna array may comprises frequency band ranges within the range of 100 MHz-50 GHz, or within the range of 2-18 GHz, or within the range of 2-6 GHz.

The plurality of cavities may at least partially filled with a filling material.

A vehicle may comprise the antenna array.

A base station may comprise the antenna array.

BRIEF DESCRIPTION OF DRAWINGS In the following, the disclosure will be described in a non-limiting way and in more detail with reference to exemplary embodiments illustrated in the enclosed drawings, in which:

Figure 1 Depicts an isometric view of inverted antenna elements

Figure 2 Depicts an isometric view of an antenna array having inverted BoR antenna elements Figure 3 Depicts a cross-sectional side view of inverted antenna elements

Figure 4 Depicts a cross-sectional side view of inverted antenna elements

Figure 5 Depicts a side view of inverted antenna elements

Figure 6 Depicts a method for manufacturing an antenna array DETAILED DESCRIPTION

In the following detailed description, some embodiments of the present disclosure will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the provided inverted antenna elements and method for manufacturing, it will be apparent to one skilled in the art that the device and method may be realized without these details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present disclosure.

In the following description of example embodiments, the same reference numerals denote the same or similar components.

The term “BoR” refers to Body-of-Revolution, a body that is rotational symmetric, a BoR antenna element refers to an antenna element that has a round shape extending into an oblong object. A BoR antenna may for instance have the shape of a cylinder or a cone. A benefit of having a BoR antenna is that it is mechanically robust and can be designed to cover a large bandwidth. Moreover, a BoR-element may be understood as a Vivaldi-like three-dimensional antenna element.

The term “antenna array” or “array of antenna elements” or “antenna element array” refers to a set of multiple connected antennas which work together as a single antenna. In this disclosure the term "antenna array” refers to at least two antenna elements. The term “RF” refers to radio frequency which is an eiectromagnetic wave having a frequency. An antenna array may be coupled to a feeding system. The term “inverted” as used herein refers to that the antenna elements are created by a manufacturing process comprising providing a plurality of cavities in a block of dielectric, where the form of the cavity in the block of dielectric defines the form of the antenna element.

Figure 1 discloses an isometric view of an antenna array 1 having inverted antenna elements 2 comprising; a three dimensional block of dielectric 3 forming a plurality of cavities 4 on a first surface 5 of the block of dielectric 3, wherein the cavities 4 extend essentially perpendicular to the first surface 5 into the block of dielectric 3, wherein at least said plurality of cavities 4 on the first surface 5 comprises an electrically conductive coating 6 having a thickness t forming inverted antenna elements 2, wherein said inverted antenna elements 2 are adapted to be coupled to an antenna feeding system 7. The inverted antenna elements 2 may be coupled to a feeding system 7 by mounting the first surface 5 of the block of dielectric 3 to the feeding system 7.

The antenna array 1 may have a first axis x1 and a second axis y1, said first axis x1 and said second axis y1 being perpendicular in relation to each other, wherein the inverted antenna elements 2 may be positioned along the direction of the first axis x1 and/or along the direction of the second axis y1. The antenna array 1 disclosed in figure 1 is a 4x4 antenna array 1 where there are 4 rows of inverted antenna elements 2 in the direction of the first axis x1 and wherein each row comprises 4 inverted antenna elements 2 in the direction of the second axis y1. As disclosed in Figure 1, the antenna array 1 may be an NxN antenna array 1, wherein there is an equal number of inverted antenna elements 2 distributed in the direction first axis x1 and the direction of the second axis y1. The antenna array 1 may further be an NxM antenna array. The antenna array 1 may form a circular shape or an elliptic shape or any other suitable shape, thus the antenna array 1 is not limited to a NxN or an NxM antenna array. Further, the block of dielectric 3 may have a circular, oval or any other suitable shape. There may be equal distance between each antenna element 2 in the antenna array 1. Further, there may be a varying distance between each antenna element 2 in the antenna array. The antenna array 1 in the method may be a sparse antenna array 1.

As disclosed in Figures 1-4, the plurality of cavities 4 may be BoR shaped, forming BoR shaped antenna inverted elements 2. The BoR shaped inverted antenna elements 2 may extend perpendicular to the first surface 5 into the block of dielectric 3, wherein the tapering form extends into the block of dielectric 3 as disclosed in figures 1-4.

The inverted antenna elements 2 may have a height H 1 , and the block of dielectric may have a height H2, wherein the height H1/H2 is within the interval of 0.6-0.95. This may allow the inverted antenna elements 2 to be fully incorporated within the block of dielectric 3, wherein the block of dielectric 3 doesn’t significantly make the antenna array 1 larger in height.

As disclosed in Figure 2, the antenna array 1 may further comprise a feeding system 7 on said first surface 5 of said block of dielectric 3.

As disclosed in Figures 1-4, and in more detail in Figures 3-5, the electrically conductive coating 6 may comprise a thickness t being at least within the range of 0.2pm-8pm on a frequency band within the range of 100MHz-50GHz. Further, the electrically conductive coating 6 may comprise a skin depth being at least within the range of 0.2pm-8pm on a frequency band within the range of 100MHz-50GHz.

The block of dielectric 3 may have a relative permittivity within the range of 1-5. Accordingly this allows the antenna elements 2 to be adapted to cover a large operational bandwidth. Further, the block of dielectric 3 may have a permittivity and/or permeability which varies across the body of the block of dielectric 3. A permeability which varies across the body of the block of dielectric 3 allows for static shaping of the element 2 gain patterns i.e. antenna beam shaping.

As disclosed in Figure 4, the second surface 8 of the block of dielectric 3 may be formed to be adapted to fit in a radome or any other type of protective enclosure. The antenna array 1 may have a volume, wherein at least 80% of the volume of the antenna array 1 comprises of dielectric material. A benefit of this is that the weight and material costs of the antenna array 1 can be kept low. Further, 52-99% of the material of the antenna array 1 may have a density within the range of 0.7-2g/cm3, preferably 70-99% of the material of the antenna array 1 may have a density within the range of 1-1.4g/cm3, more preferably 85- 99% of the material of the antenna array 1 may have a density being less than 1.4g/cm3. Having an antenna array 1 where a majority of the material used in the antenna array 1 comprise a low density allows for an antenna array 1 with a lower weight.

It is disclosed in Figure 3 and Figure 4 that the electrically conductive coating 6 covers the surface of the plurality of cavities 4 and further also covers the surface in-between the plurality of cavities 4. In other words, the electrically conductive coating 6 may fully cover the first surface 5. However, as disclosed in Figure 5, the electrically conductive coating 6 may only cover the surface of the plurality of cavities 4 of the first surface 5.

The antenna array 1 may comprise frequency band ranges within the range of 100 MHz-50 GHz, or within the range of 2-18 GHz, or within the range of 2-6 GHz. The antenna array 1 may cover a large bandwidth which allows it to have a broad level of appliance. It may for instance be applied in telecom or within electronic warfare systems. The plurality of cavities 4 may at least partially be filled with a filling material. The filling material may be any suitable substrate.

As disclosed in Figures 3-5, the inverted antenna elements 2 may comprise an inner surface 10, and an outer surface 11 , wherein the form of the inner surface 10 of the inverted antenna elements 2 corresponds to the form of the plurality of cavities 4 formed in the block of dielectric 3.

Further, there may be provided a vehicle comprising the antenna array 1. The vehicle may be a vessel, an aircraft or a ground vehicle. Furthermore, there may be provided a base station comprising the antenna array 1. The antenna array may be used in different applications such as a radar transmitter and/or receiver or for telecom communication purposes.

As disclosed in Figure 6, there is further provided a method (100) for manufacturing an antenna array 1 having inverted antenna elements 2, comprising the steps of: providing (101) a three dimensional block of dielectric 3; forming (102) a plurality of cavities 4 on a first surface 5 of the block of dielectric 3, wherein the cavities 4 extend essentially perpendicular to the first surface 5 into the block of dielectric 3; providing (103) at least the plurality of cavities 4 on the first surface 5 with an electrically conductive coating 6 having a thickness t, forming inverted antenna elements 2; wherein said inverted antenna elements 2 are adapted to be coupled to a feeding system 7.

The method (100) allows for a cheaper and faster manufacturing of antenna arrays 1. By forming the shape of the inverted antenna elements 2 prior to coating the antenna element shape with an electrically conductive coating 6 there is allowed for a convenient way of manufacturing antenna arrays 1 that have complex geometry and dimensions, such as antenna arrays 1 comprising BoR antenna elements 2. Accordingly, the manufacturing of the inverted antenna elements 2 may be performed by mainly treating the first surface 5 of the block of dielectric 3, which allows for the first surface 5 to be adapted to be coupled to a feeding system that is manufactured separately.

The electrically conductive coating 6 may be applied to the first surface by flame spraying, thermal spraying, electroplating, physical vapour deposition, chemical vapour deposition or any other suitable method. The electrically conductive coating 6 may be a metal.

The plurality of cavities 4 may be BoR shaped-cavities 4 extending in a tapered manner, forming BoR-shaped antenna elements 2.

The method 100 may further comprise the step of assembling a feeding system 7 on said first surface 5 of said block of dielectric 3. The electrically conductive coating 6 may comprise a minimum thickness t being at least within the range of 0.2pm-8pm on a frequency band within the range of 100MHz-50GHz. The minimum thickness refers to the thinnest thickness t of the conductive coating 6 while still functioning optimally. As disclosed in Figure 3, the method 100 may further comprise the step of forming a second surface 8 on said block of dielectric 3 so as to fit in a radome or any other type of protective enclosure, wherein the second surface 8 of said block of dielectric 3 is the opposing surface of the first surface 5. The plurality of cavities 4 may be formed by at least one of drilling, casting, milling or additive manufacturing. The plurality of cavities 4 may be formed by drilling, wherein the drill comprises a drill bit, wherein the drill bit penetrates the first surface 5 of the block of dielectric to form each of the plurality of cavities 4.

The electrically conductive coating 6 may be deposited fully on the first surface 5. However, the method 100 may further comprise the step of removing at least a part of the electrically conductive coating 6 in-between the plurality of cavities 4 on the first surface 5 of said block of dielectric 3.

Further, the method 100 may comprise the step of at least partially filling said plurality of cavities 4 with a filling material after the conductive coating 6 has been provided. The filling material may increase the rigidity of the inverted antenna elements 2. The filling material may be a substrate. The block of dielectric 3 may have a relative permittivity within the range of 1- 5. Further, the block of dielectric 3 may have a relative permittivity which varies across the body of the block of dielectric 3.