Antenna arrangement with lensing radome

Abstract

The present disclosure relates to an antenna arrangement with a radome. The antenna arrangement comprises a radiation layer (20), an antenna array element arranged in the radiation layer (20), the antenna array element comprising a plurality of antennas (24) distributed in a region having a region length and region width. The arrangement further comprises a radome (1) having a first main surface (1a) facing the radiation layer (20) and a second main surface (1b) arranged opposite of the first main surface (1a), wherein the second main surface (1b) is substantially flat, wherein the first main surface (1a) comprises at least one void space region (100), the at least one void space region (100) extending into the radome (1) towards the second main surface and comprises one or more void spaces and / or indentations acting as a lens, wherein the at least one void space region (100) has a maximum width (W1) that depends on an operational guided wavelength and a maximum length (L1 ) that depends on the length of the region of the antenna array element.

Description

[0001] ANTENNA ARRANGEMENT WITH LENSING RADOME

[0002] TECHNICAL FIELD OF THE INVENTION

[0003]

[0001] The present invention relates to a radome, an antenna arrangement comprising the radome and an antenna arrangement comprising the radome and an absorber.

[0004] BACKGROUND OF THE INVENTION

[0005]

[0002] As antennas are used in many applications and environments, it is common that antennas must be protected with a protective casing or similar. In some implementations, an antenna radome is used to protect the antenna from the environment. A radome is typically made of a dielectric material, such as a plastic material, and manufactured as a thin sheet which is fitted over the antenna to protect the antenna from the environment. The electromagnetic signals transmitted from, or being received by, the antenna can penetrate through the dielectric material constituting the radome allowing the antenna to function as intended while at the same time being protected from e.g. moisture, dust or insects of the environment by the radome.

[0006]

[0003] Despite the radome being made of dielectric material there is a risk that the radome distorts or otherwise degrades the antenna performance. For example, if the radome is made too thick there is a risk that the electromagnetic signals are partially absorbed by the radome, necessitating increased radiation power and / or higher gain antennas to compensate. On the other hand, if the radome is made too thin there is an increased risk that the radome breaks or does not offer sufficient protection from the environment.

[0007]

[0004] While some solutions have been presented wherein the radome is curved or provided with recesses and / or protrusions that decrease the radome impact on the antenna performance these radomes are often difficult to manufacture or difficult to use together with antennas used in space constrained applications, which often is the case for e.g. automotive implementations.

[0008]

[0005] Hereby, there is a need for a new and improved radome which overcomes at least some of the shortcomings mentioned above.

[0009] GENERAL DISCLOSURE OF THE INVENTION

[0010]

[0006] It is a purpose of the present invention to overcome at least some of the shortcomings of the prior solutions and provide an improved radome and antenna arrangement comprising a radome.

[0011]

[0007] According to a first aspect of the present invention there is provided an antenna arrangement comprising a radiation layer and an antenna array element arranged on the radiation layer. Wherein the antenna array element comprises a plurality of antennas distributed in a region having a region length and region width, each antenna being configured to transmit and / or receive electromagnetic radiation. The antenna arrangement further comprises a radome made of a dielectric material, the radome having a first main surface facing the radiation layer and a second main surface arranged opposite of the first main surface. The second main surface is substantially flat, and the first main surface comprises at least one void space region, the at least one void space region extending into the radome towards the second main surface and comprises a one or more void spaces and / or indentations forming a lens, wherein the at least one void space region has a maximum width and a maximum length. The maximum width, W 1 , is less than or equal 150% of the width of the antenna array element preferably less than 100% of the width of the antenna array element wherein the maximum length, LI, is at least 50% of the length of the region of the antenna array element.

[0012]

[0008] As described below, the void space region may comprise a lensing indentation (i.e. a recess in an otherwise solid material) or a partial infill region (i.e. a region with a partial material infill having a partial infill geometry). Both of these variants feature a locally reduced material density in radome.

[0013]

[0009] A lensing indentation may be manufactured using 3D printing, etching, milling or even injection molding. On the other hand, a partial infill region is preferably realized using a 3D printing process.

[0014]

[0010] For example, a single void space region may be used for an antenna array element comprising a plurality of antennas. This saves space and makes the radome easier to manufacture compared to a radome featuring one void space region for each antenna. Additionally, since the void space region can be made very compact, it does not impose restrictions on how densely a plurality of antenna array elements may be arranged, which makes the antenna arrangement easier to design and allows for antenna arrangements with improved sensing performance. By comparison, a lensing indentation acting as the void space region used with a single antenna may limit how densely the antennas can be arranged. However, with the lensing indentation of the present disclosure, a single lensing indentation is used for many antennas.

[0015] [OH] The width and length of the void space region and antenna array element region are defined along a width axis, W, and length axis, L, respectively, wherein the width and length axes are perpendicular.

[0016]

[0012] In some implementations, the void space region comprises a lensing indentation (11) arranged to face the antenna array element, the at least one lensing indentation (11) extending into the radome (1) towards the second main surface (lb), wherein a cross-sectional area of said lensing indentation (11) is monotonically decreasing towards the second main surface.

[0017]

[0013] The antennas extend through the radiation layer along a depth axis, D, and the lensing indentation extends into the radome towards the second main surface along the depth axis, wherein the depth axis is perpendicular to the length and width axes.

[0018]

[0014] The cross-sectional area of the lensing indentation is defined in a plane spanned by the width and length axis (i.e. a plane having the depth axis as a normal) and the cross-sectional area varies along the depth axis. The cross-sectional area decreases when moving from the first main surface towards the second main surface. That is, the lensing indentation may be generally convex, increasing in size towards the second main surface. The cross-sectional area of the lensing indentation has a maximum width at each location of the cross-section along the depth axis, and in some implementations the maximum width of the cross-section decreases towards the second main surface whereby the cross-sectional area decreases. The maximum length of the cross-section may also decrease but it is also envisaged that the maximum length is maintained along the depth axis.

[0019]

[0015] The operational guided wavelength is the wavelength which the antenna arrangement is designed for. In general the operational guided wavelength will influence the size dimension of all waveguiding features of an antenna, wherein a smaller operational guided wavelength results in smaller dimensions, and vice versa. For example, the operational guided wavelength is determined by the antennas of the radiation layer wherein slot type antennas are typically 0.5 operational guided wavelengths long and about 0.1 operational guide wavelengths wide.

[0020]

[0016] The radome and void space region according to the first aspect may be used with antenna array elements created in various technologies. A few examples are antenna elements created in PCB technology (e.g. patch antennas), dielectric antennas, horn antennas and waveguide antennas. Each antenna may hereby be a patch antenna arranged on a PCB, wherein the PCB acts as the radiating layer.

[0021]

[0017] For applications such as automotive radar, there is a benefit in using planar waveguide technology such as gap waveguide technology or multilayer waveguide technology because of the high efficiency and smaller formfactor which is desirable in automotive radar. Accordingly, each antenna may be realized as an aperture extending through a radiation layer. One or more distribution layers may be provided below the radiation layer, wherein the distribution layers form a waveguide configured to feed the antenna apertures (or lead electromagnetic radiation away from the apertures when the antenna apertures are operating in receiving mode).

[0022]

[0018] In some implementations, a first thickness, Tl, of the radome, defined as a distance from the first main surface to the second main surface, is between the operational guided wavelength divided by four and the operational guided wavelength.

[0023]

[0019] Accordingly, the radome is made very thin so as to avoid absorbing electromagnetic signals, to decrease the weight of the antenna arrangement and to decrease the amount of material required to manufacture the radome.

[0024]

[0020] In some implementations, the radome is arranged at a separation distance from the radiation layer, wherein the separation distance is between 25% and 100% of the operational guided wavelength.

[0025]

[0021] This separation distance is optimal for keeping the lensing indentation small and compact while still allowing the lensing indentation to have a simple, easy to manufacture, design. If the radome is placed too far away, the lensing indentation may have to be much larger. On the other hand if the lensing indentation is placed too close to the radiation layer the nearfield properties of antenna array element must be considered whereby the lensing indentation design may introduce loading effects on the antenna array element which decreases the transmitted electromagnetic energy.

[0026]

[0022] In some implementations, the lensing indentation is defined by a bottom surface and side walls extending from the periphery of the bottom surface away from the second main surface wherein the bottom surface is substantially flat.

[0027]

[0023] With a flat bottom surface, the lensing indentation is simplified to allow for simplified manufacturing and design. The distance between the flat bottom surface and the second main surface resembles an impedance transformer which may increase the efficiency of the transmission of electromagnetic waves from the antennas and through the radome, i.e. the antenna efficiency.

[0028]

[0024] In some implementations, a second thickness of the radome at the bottom surface is at least 30% smaller than a first thickness of the radome between the first and second main surface.

[0029]

[0025] In some implementations, the lensing indentation is asymmetrical and / or arranged off-center with respect to the antenna array element region.

[0030]

[0026] With a geometry of the lensing indentation which is not symmetrical, this may result in a redistribution of the radiated energy asymmetrically. This may be used to shape the radiation pattern. For example, a tapered radiation pattern may be achieved which is beneficial for certain applications, such as corner radars used for lane change assistance.

[0031]

[0027] Alternative or additionally, to the lensing indentation being asymmetrical, the lensing indentation may be placed with an offset from the center of the region of the antenna array element. The lensing indentation may be offset from the center of the region in the width and / or length direction.

[0032]

[0028] In some implementations, the lensing indentation is elongated along a length axis.

[0029] Optionally, the region of the antenna array element is also elongated. An elongated antenna array element and lensing indentation may contribute to concentrating the antenna directivity in the depth-length plane which is useful in many applications, such as in automotive radar applications.

[0033]

[0030] Optionally, the width of the lensing indentation varies along the length axis.

[0034]

[0031] The width may vary continuously, periodically or intermittently. A benefit with a periodically or intermittently varying width for an elongated lensing indentation is that this type of lensing indentation further facilitates concentration of the antenna directivity in the depthwidth plane.

[0035]

[0032] The elongated lensing indentation may e.g. be formed as a series of partially overlapping semi-spherical shaped indentations or truncated pyramid indentations, such as truncated hexagonal pyramid indentations.

[0036]

[0033] In some implementations, the width varies substantially periodically or intermittently along the length axis, and wherein the period is between the operational guided wavelength divided by four and the operational guided wavelength, and preferably between 40% of the operational guided wavelength and 60% of the operational guided wavelength.

[0037]

[0034] Although a smaller period offers a slight increase in the effectiveness of the lensing indentation, a larger period is beneficial for manufacturing considerations. Preferably, the period is about half the operational guided wavelength which is a trade-off between lensing properties and manufacturing considerations.

[0038]

[0035] In some implementations, the width of the bottom surface at its maximum width is at least two times the width of the bottom surface at its minimum width and / or wherein the width of the lensing indentation at its maximum width is at least two times the width of the lensing indentation at its minimum width.

[0039]

[0036] With this relation between the maximum and minimum width the antenna performance (e.g. in terms of directivity in the width-depth plane or half-power beamwidth) may be improved.

[0037] In some implementations the side walls of the lensing indentation are slanted.

[0040]

[0038] The side walls of the lensing indentation may hereby be slanted / angled, which is beneficial in manufacturing and may offer better performance for the distribution of the electromagnetic energy.

[0041]

[0039] Slanted side walls are non-perpendicular to the width-length plane. For example, the side walls have a surface normal which faces away from the second main surface of the radome, providing a concave indentation which increases in size towards the first main surface. In some implementations, the side walls are defined by a plurality of flat and slanted side wall segments, wherein each side wall segment is oriented differently from neighboring side wall segments. For example, when the lensing indentation is shaped like a sequence of partially overlapping truncated hexagonal pyramidical recesses the side walls may be flat and slanted side wall segments.

[0042]

[0040] In some implementations, the void space region comprises a partial infill region, the partial infill region comprising partial infill geometry.

[0043]

[0041] A partial infill geometry or structure is an alternative method of locally varying the dielectric constant of the radome to achieve the desired lensing effect that may affect the antenna pattern. A benefit with a partial infill geometry is that, provided the infill geometry unit cell is small, a continuous or smoothly varying dielectric constant may be achieved over the partial infill region which facilitates realization of radomes with more accurate lensing properties.

[0044]

[0042] Hereby, in some implementations, the partial infill geometry has a unit cell size of less than 50% of the operational guided wavelength or less than 10% of the operational guided wavelength. A small unit cell size enhances the performance of the radome (in terms of accurately shaping the radiation pattern).

[0045]

[0043] In some implementations, the partial infill geometry has a fill ratio which, at a predetermined depth of the radome, varies along the width and / or length direction.

[0046]

[0044] A varying fill ratio along the width direction may be used to control azimuth properties of the antenna pattern and a varying fill ratio along the height direction may be used to control the elevation properties of the antenna pattern. Of course, the variations may be provided in only one of or both of width and height. Additionally or alternatively, the fill ratio may vary in the depth direction as well. For example, the fill ratio may increase when going along the depth direction from the first main surface towards the second main surface.

[0047]

[0045] In some implementations, the fill ratio along the width direction at the specific depth of the radome follows a convex or concave infill profile.

[0046] A convex infill profile has the highest infill ratio at the center and lower infill ratio at the edges of the partial infill region, and this type of infill profile may be used to create a partial infill region which increases the directivity. A concave infill profile has the lowest infill fill ratio at the center and higher infill ratio at the edges of the partial infill region, and this type of infill profile may be used to create a partial infill region which increases the beamwidth of the antenna array element.

[0048]

[0047] The fill ratio may vary also along the length and / or depth direction. For example, in some implementations, the fill ratio of the void space region varies along the length direction. For example, the fill ratio varies along the length of the void space region according to a convex or concave infill profile.

[0049]

[0048] A convex infill profile (high infill ratio at the center and low infill ratio at the edges) along the length direction may be used to enhance the directivity of the antenna array element.

[0050]

[0049] A concave infill profile (low infill ratio at the center and high infill ratio at the edges) along the length direction may be used to enhance the beamwidth of the antenna array element in the length-dept plane. Alternatively, a concave infill profile may be used to reduce the directivity of the propagating modes inside the radome, resulting in less variation of the radiation pattern.

[0051]

[0050] In some implementations, the partial infill region is surrounded by a constant infill region having a same infill ratio such as 100% infill or the same infill as the edge of the partial infill region. The constant infill region may hereby form a frame around the one or more partial infill regions of the radome and provide structural stability.

[0052]

[0051] In some implementations the radome further comprises a first solid cover layer arranged between the first main surface and the radiation layer. The first solid cover layer may help protect the partial infill region, and prevent ingress of water, dirt or dust.

[0053]

[0052] In some implementations, the partial infill region is realized in a first partial infill layer and the radome further comprises a second partial infill layer comprising a partial infill region, the second partial infill region being arranged on the opposite side of the first radiation layer from the radiation layer. With two or more partial infill layers, each comprising one or more partial infill regions it is possible for multiple partial infill regions to cooperate in forming the lensing effect and generating the desired antenna pattern.

[0054]

[0053] In some implementations, the radome further comprises a solid core layer arranged between the partial first and second partial infill layer. The solid core layer may provide increased stability and structural resilience to the radome. Any layer of the radome may be made using a dielectric material such as a plastic material.

[0055]

[0054] In some implementations, the local material density of the radome is monotonically increasing towards the second main surface.

[0056]

[0055] The local material density may have a monotonically increasing local density both when the lensing effect is achieved with a partial infill region (e.g. a monotonically increasing infill ratio) and a lensing indentation.

[0057]

[0056] In some implementations, the antenna arrangement is realized using a linear unit cell having a having a width AW, a depth AD and a length AL wherein AL > AW and AL > AD, and wherein the linear unit cell comprises a configurable length central void portion of length CL.

[0057] This linear unit cell has shown to result in compact and efficient lensing indentations. Optionally, the linear unit cell is in the shape of a rectangular cuboid.

[0058]

[0058] In some implementations, the length AL of the linear unit cell is about 50% of the operational guided wavelength. Optionally, the width AW and depth AD are smaller than 25% of the operational guided wavelength, smaller than 10% of the operational guided wavelength or smaller than 5% of the operational guided wavelength.

[0059]

[0059] In some implementations, the maximum length is at least 80% of the length of the region of the antenna array element, at least 100% of the length of the region of the antenna array element or at least 100% of the length of the region of the antenna array element plus a predetermined distance, the predetermined distance being at least one operational guided wavelength.

[0060]

[0060] With a sufficient length of the lensing region with respect to the antenna array element, more of the electromagnetic signals to / from antenna array element will be refracted by the lensing region .

[0061]

[0061] In some implementations, the first main surface is substantially flat except for at least one raised section protruding from the flat first main surface, and wherein said at least one lensing region is arranged in the at least one raised section.

[0062]

[0062] This design has the advantage of enabling the radome to be made with minimum material and minimum weight. The radome is thicker in the area surrounding the lensing region, allowing e.g. a lensing indentation or partial infill region of sufficient depth to be realized, whereby the radome in regions surrounding the raised section may be made much thinner. For example, the thickness of the radome in the region surrounding the raised section is smaller than the depth of the lensing indentation. In this way, the necessary dielectric material is present precisely where it is needed to refract the electromagnetic signals. In other regions, the radome may be thinner which decreases the amount of material required, decreases the weight and / or leaves an increased amount of space between the radome and the radiation layer which may be beneficial for heat dissipation and / or for allowing an electromagnetically absorptive material to be arranged between the radome and the radiation layer.

[0063]

[0063] In some implementations, each raised section forms a frame surrounding the lensing region along the width axis and length axis.

[0064]

[0064] The frame region may have a width and / or height which is at least one operational wavelength larger than the maximum width and / or length of the lensing region. The raised section may abruptly transition to the first main surface, or it is envisaged that the raised section tapers towards the first main surface.

[0065]

[0065] In some implementations, each raised section is surrounded by a portion of the flat first main surface.

[0066]

[0066] That is, if a plurality of lensing regions are provided on the first main surface of the radome, each associated with and facing a corresponding antenna array element, each lensing region is arranged in its own raised section and the raised sections protrude outwards from the first main surface.

[0067]

[0067] In some implementations, the bottom surface is in the same plane as the flat first main surface or in a plane between the flat first main surface and the flat second main surface.

[0068]

[0068] Hereby, the lensing region is deeper than would have been possible if no raised sections where provided.

[0069]

[0069] In some implementations, a second thickness of the radome at the bottom surface is at least 30% smaller than a first thickness of the radome between the first and second main surface.

[0070]

[0070] This may apply for both embodiments with a raised section and embodiments without a raised section. For embodiments with a raised section the second thickness and the first thickness may be the same, or it is even envisaged that the second thickness is greater than the first thickness for the embodiments with a raised section.

[0071]

[0071] In some implementations, the antenna array element comprises at least four antennas arranged in at least two columns, with each column comprising at least two antennas.

[0072]

[0072] Of course, the antenna array element may comprise more or fewer antennas. For example, the antenna array element comprises only one antenna in each column. Or the antenna array element comprises two columns with three, four, five or more antennas in each column. It is also envisaged that the antenna array element may comprise more than two columns, such as three of four columns with at least two antenna elements in each column. The columns may be aligned with each other. It is also envisaged that the columns are offset from each other so as to form a zig-zag pattern of antennas.

[0073]

[0073] In some implementations, the antenna array element comprises at least four antennas arranged in at least two columns, with each column comprising at least two antennas.

[0074]

[0074] That is, the maximum width at least corresponds to the separation distance between the two columns. If more than two columns are used in the antenna array element, the maximum width of the lensing region may be at least the separation distance between the two outermost columns. This allows the effective size of the lensing region (i.e. the size of the lensing region as it appears when projected onto the radiation layer along the depth axis) to cover the antennas which is beneficial for the desired lensing effect.

[0075]

[0075] In some implementations, the maximum width of the lensing region along the width axis, is larger than a separation distance between the two columns.

[0076]

[0076] In some implementations, each antenna is elongated along the length axis.

[0077]

[0077] Additionally or alternatively, the elongated antennas are tilted with respect to the length axis to form an angle between 0 and 45° with the length axis. The shape of the antennas may in general be any shape, such as dumbbell shaped, stadium shaped or rectangular.

[0078]

[0078] In some implementations, the radiation layer further comprises at least two corrugations arranged on opposite sides of the antenna array element and wherein the lensing region is arranged between the two corrugations along the width axis.

[0079]

[0079] The corrugations help prevent surface currents from propagating along the surface of the radiation layer.

[0080]

[0080] In some implementations, the antenna arrangement further comprises an absorber layer arranged between the radome and the radiation layer, wherein the absorber layer comprises at least one opening configured to enable the antenna array element of the radiation layer to communicate with the lensing region.

[0081]

[0081] The absorber layer is made of a material which absorbs electromagnetic signals. For example, the absorber is made from a dielectric material which is infused with carbon particles.

[0082]

[0082] The absorber helps prevent surface currents from propagating along the surface of the radiation layer, which mitigates interference and may help improve the antenna properties such as the similarity of the radiation patterns in case multiple antennas are present. Since the radome leaves some space between the radiation layer and the first main surface arrangement of the absorber layer between these two layers is effective use of space. If more than one antenna array element is provided, a corresponding opening is provided in the absorber layer for each antenna array element.

[0083]

[0083] In some implementations, the absorber layer abuts at least one of the radiation layer, and the first main surface of the radome.

[0084]

[0084] Optionally, the absorption material is adhered to at least one of the radiation layer and the first main surface. Also, minimizing the distance between the absorption material and the first main surface of the radome increases the effectiveness of the absorption material.

[0085]

[0085] In some implementations, the at least one opening in the absorber layer has an opening dimension which varies along a depth axis, perpendicular to the width and length axes.

[0086] For example, the at least one opening has an opening diameter which increases towards the radiation layer.

[0086]

[0087] More specifically, the opening may be tapered which is beneficial for manufacturing.

[0087]

[0088] In other implementations, the thickness of the absorber might be increased which offers better performance of the absorber, increasing the similarity between elements and reducing the individual antenna properties.

[0088]

[0089] In other implementations, where the similarity of the radiation pattern is not crucial, the thickness of the absorber might be minimized to increase the efficiency of the antenna array.

[0089]

[0090] In some implementations, the void space region is realized using a linear unit cell. The linear unit cell may be oriented with so as to form an angle of 45 degrees (clockwise or counterclockwise)with respect to the direction of elongation of the antennas and / or antenna array element. That is, the linear unit cell is rotated around the depth axis with respect to the antennas and / or the antenna array element. The void space region may have a partial infill ratio of about 50% and be arranged with a depth extension between 100% and 200% of the operating wavelength.

[0090]

[0091] This rotation of the linear unit cell may be used to exploit the anisotropic nature of the linear unit cell, by increasing the lensing region in the dept axis, the anisotropy introduces a phase shift between two orthogonal radiation components, offering the possibility to transform a linear polarization into a circular polarization. BRIEF DESCRIPTION OF THE DRAWINGS

[0091]

[0092] Aspects of the present invention will be described in more detail with reference to the appended drawings, showing currently preferred embodiments.

[0092]

[0093] Figures la-d show cross-sectional views of a multilayer antenna and of an antenna arrangement comprising a radome and a radiation layer.

[0093]

[0094] Figures 2a-b show cross-sectional views of an antenna arrangement comprising a radome with a raised section and a radiation layer.

[0094]

[0095] Figures 3a-c show cross-sectional views of alternative radome designs, according to embodiments of the present disclosure.

[0095]

[0096] Figure 4a-b show a bottom-up view and perspective view of a radome according to some embodiments.

[0096]

[0097] Figure 5a-b show a bottom-up view and perspective view of an alternative radome according to some embodiments.

[0097]

[0098] Figures 6a-b show top-views of a radiation layer with an antenna array element and corrugations, according to some embodiments.

[0098]

[0099] Figure 7 shows a top-down view of a radiation layer with a lensing indentation overlayed.

[0099]

[0100] Figures 8a-b show an exemplary radiation layer with a plurality of antenna array element, and a corresponding radome with one lensing indentation for each antenna array element.

[0100]

[0101] Figures 9a-b show cross-sectional views of various multilayer antennas which may be used together with the radome of the present disclosure.

[0101]

[0102] Figure 10 shows a cross-sectional view of a multilayer antenna with corrugations for suppressing surface currents, according to some implementations.

[0102]

[0103] Figure 11 shows a cross-sectional view of a radome with a partial infill region instead of a lensing indention, according to some implementations.

[0103]

[0104] Figures 12a-b show cross-sectional views of multi-layer radomes with one or two partial infill layers, according to some implementations.

[0104]

[0105] Figure 13 illustrates example partial infill geometries which may be used to realize a partial infill region.

[0105]

[0106] Figure 14 illustrates an example unit cell for forming a radome with a lensing indentation. DETAILED DESCRIPTION OF CURRENTLY PREFERRED EMBODIMENTS

[0106]

[0107] In the following detailed description, preferred embodiments of the invention 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. It may also be noted, for the sake of clarity, that the dimensions of certain components illustrated in the drawings may differ from the corresponding dimensions in real-life implementations of the invention.

[0107]

[0108] It also noted that in the following exemplary embodiments, the antenna array is a multilayer waveguide antenna wherein the antennas are antenna apertures 24a, 24b in the radiation layer 2. However, it is envisaged that this exemplary radiation layer 2 may be replaced with PCB carrying patch antennas instead of antenna apertures. Other alternatives, such as horn antennas and slotted rectangular waveguide antennas are also envisaged.

[0108]

[0109] Fig. la illustrates a cross-sectional view of a multilayer antenna 2 with two layers 20, 21. The cross-section is taken in a depth-width plane spanned by the perpendicular depth, D, and width, W, axes. A multilayer antenna 2 comprises a plurality of physical layers 20, 21 configured to route electromagnetic signals at an operational frequency, corresponding to an operational guided wavelength X, between the layers 20, 21 using waveguiding structures arranged on one or more of the physical layers 20, 21.

[0109] [HO] In the illustrated example embodiment of fig. la, the multilayer antenna 2 comprises two physical layers, a radiation layer 20 and a distribution layer 21. The radiation layer 20 is substantially flat and arranged on top of the distribution layer 21. The distribution layer comprises a textured surface referred to as a metasurface. The metasurface comprises a plurality of protruding pins 41 that surround one or more waveguide paths 25a, 25b. The protruding pins 41 form an electromagnetic band-gap (EBG) structure together with the radiation layer 20 which prohibits electromagnetic signals at the operational guided wavelength X to propagate between the distribution layer 21 and the radiation layer 20 other than along the waveguide paths 25a, 25b which are free from pins 41. A great advantage with multilayer waveguides compared to e.g. traditional rectangular waveguides is that the layers need not be in physical contact with each other to electromagnetically seal-off the waveguide paths 25a, 25b. That is, the radiation layer 20 may contact the distribution layer 21 or there may be an airgap between at least a portion of the radiation layer 20 and the distribution layer 21.

[0110] [HI] The protruding pins 41 of the distribution layer 21 form thick sections surrounded by thin sections 42. In some implementations the difference in height between the thick sections and thin sections 42, i.e. the height of the pins 41, is about / 4 or less. It has been found that much smaller pins 41 may also be used while still forming an effective EBG structure which enables the distribution layer 21 to be made thinner which in turn allows the multilayer antenna 2 as a whole to be made thinner. In some implementations, the height of the pins 41 is / 5 or less, X / 7 or less, or even X / 10 or less.

[0111]

[0112] Optionally, a ridge 26 may be provided in each waveguide path 25a, 25b to facilitate guiding of the electromagnetic signals along each waveguide path 25a, 25b.

[0112]

[0113] Turning to fig. lb, another depth-width cross-section of a multilayer antenna 2 is shown. Here, the cross-section overlaps with antenna apertures 24a, 24b provided in the radiation layer 20. Each antenna aperture 24a, 24b communicates with a respective waveguide path 25a, 25b whereby electromagnetic signals may be received by the antenna apertures 24a, 24b and guided into the waveguide paths 25a, 25b and / or electromagnetic signals propagating the waveguide paths 25a, 25b may be transmitted via the antenna apertures 24a, 24b. That is, each antenna aperture 24a, 24b may act as a transmitting (TX) and / or receiving (RX) element.

[0113] As described below, multiple antenna apertures arranged close together may form a group, called an antenna array element, and multiple antenna array elements may be provided in the radiation layer 20.

[0114]

[0114] The multilayer waveguide antenna 2 of figs, la and lb is only one exemplary type of multilayer waveguide having two layers, and other types of multilayer waveguide antennas with more than two layers are also envisaged. Additional examples of such multilayer antennas are described below, in connection with figs. 9a-b.

[0115]

[0115] In any multilayer antenna 2, each layer 20, 21 may be made of a metal. For example, each layer is made of copper, brass or aluminum. Alternatively, each layer 20, 21 is made of a non-metal material, such as a plastic material, and coated with a metal (such as copper). It is also envisaged that the two types of layers, i.e. made of metal and made of non- metal and coated with a metal, may be combined in any way.

[0116]

[0116] Starting with fig. 1c various details of the envisaged radome 1 will be described. In figs. 1 , 2, 3b-c and figs. 4 to fig. 8a the illustrated example radomes comprise a lensing indentation constituting the void space region. However, as will be appreciated by the person skilled in the art any lensing indentation may be replaced with a partial infill region and vice versa, to achieve the same or a similar lensing effect. Example radomes 1 with a partial infill region instead of a lensing indentation are shown in figs. 11 - 13.

[0117]

[0117] In fig. 1c the distribution layer 21 of figs, la and lb has been removed for illustration purposes. The radiation layer 21 comprises at least two antenna apertures 24a, 24b forming an antenna array element for transmitting and / or receiving electromagnetic signals. To protect the radiation layer 20 and the antenna arrangement as a whole, a radome 1 has been arranged on top of the radiation layer 20. The radome 1 is made of a dielectric material (e.g. a plastic material) and allows electromagnetic signals to pass therethrough. It has been realized that the radome 1 may not only serve to protect the radiation layer 20 but may also contribute to modifying the antenna properties of the antenna array element. For example, the antenna gain, directivity pattern in azimuth and / or elevation, and half-power beamwidth may be adjusted by providing an indentation in the radome 1 which effectively forms a dielectric lens. The radome 1 together with the radiation layer forms an antenna arrangement 10.

[0118] [US] The radome 1 of fig. 1c comprises a substantially flat first main surface la facing the radiation layer 20 and a substantially flat second main surface lb facing the opposite direction. An advantage with a substantially flat second main surface lb is that it is esthetically pleasing and easy to clean, since this surface may be the only part of the antenna system which is visible or accessible. Another advantage with a substantially, flat second main surface is that it is less prone to accumulate contaminations which could interfere with the radiation and / or may increase the need for more frequent cleaning.

[0119]

[0119] A lensing indentation 11 is provided in the first main surface 1 a. The lensing indentation 11 forms one type of void space region 100 outlined with the dashed box in fig. 1c. The lensing indentation 11 has a bottom surface 12 located between the first main surface la and the second main surface lb, when viewed along the depth axis. In the embodiment of fig. 1c the bottom surface 12 is substantially flat and parallel to the substantially flat first and second main surface la, lb. A benefit with flat bottom surface 12 is that it easy to realize in manufacturing. However, a curved bottom surface, dome shaped bottom surface or a bottom surface being flat but slanted with respect to the first or second main surface la, lb is also envisaged.

[0120]

[0120] The bottom surface 12 is connected to the first main surface la with side walls 13. The side walls 13 of fig. 1c are straight but slanted relative the depth axis D so as to form a lensing indentation which is convex and opens up towards the first main surface 1 a and towards the radiation layer 20. Hereby, the intersection between the bottom surface 12 and the slanted side walls may be above 90°.

[0121]

[0121] Other side walls are also envisaged, such as curved side walls or side walls which are not slanted relative to the depth axis (for example forming a 90° intersection with the bottom surface).

[0122]

[0122] The radome 1 is arranged close to the radiation layer 20. For example, the closest distance between the radome 1 and the radiation layer 20 is between 25% and 100% of the operational guided wavelength and preferably between 35% and 80% of the operational guided wavelength X, and most preferably around 50% of the operational guided wavelength X.

[0123]

[0123] Here it is noted that the radiation layer 20 may be the top layer of any multilayer antenna described herein (see e.g. figs la-b and figs. 9a-b) or other types of gap waveguide antennas. However, it is also envisaged that the radiation layer 20 is the top layer of a rectangular waveguide wherein the antenna apertures 24a, 24b are slots formed in the rectangular waveguide.

[0124]

[0124] Additionally, many of the examples provided herein relate to antenna technology with radiation layers 20 with apertures 24a, 24b forming the antennas PCB antenna technology may also be used. For example, it is well known that patch antennas realized on a PCB may be used to form an antenna array element, and such a PCB antenna may be used with the radome and lensing indentation described herein.

[0125]

[0125] The radiation layer 20 and the radome 1 form an antenna arrangement 10, which may further comprise other layers than the radiation layer, such as the distribution layer of figs, la-b or the layers of figs. 9a-b.

[0126]

[0126] As described below, multiple antenna array elements (each comprising a plurality of antenna apertures) may be provided in the same radiation layer 20. To prevent undesired direct coupling between the antenna array elements (for example to prevent electromagnetic signals transmitted from a transmitting antenna array element from interfering with a receiving antenna array element) an absorber layer 3 may be arranged between the radome 1 and radiation layer 20 as shown in fig. Id.

[0127]

[0127] The absorber layer 3 may be in contact with one or both of the radome 1 and the radiation layer 20. It is in general not necessary for the absorber layer to contact both the radome 1 and the radiation layer 20. That is, if the absorber layer 3 is attached to the radome 1 there may be space between the absorber layer 3 and the radiation layer 20. Preferably, the absorber layer 3 is attached to the radiation layer and there may be space between the absorber layer 3 and the radome 1 . Since the distance between the radiation layer 20 and radome 1 is preferably below the operational guided wavelength X, the thickness of the absorber layer 3 is also preferably less than the operational guided wavelength X to fit between the radiation layer 20 and radome 1 .

[0128]

[0128] The absorber layer 3 comprises an opening 31 sized and adapted to allow the antenna apertures 24a, 24b to communicate with the lensing indentation 11. The opening 31 in the absorber 3 is sufficiently large to overlap with all antenna apertures in the antenna array element. If more than one antenna array element (each comprising a plurality of antenna apertures) is provided in the radiation layer 20 the absorber comprises a plurality of openings 31 , one opening for each antenna array element. Each opening 31 may preferably be a slightly larger than the antenna array element region to provide some margin and prevent the absorber layer 3 from absorbing electromagnetic signals that are to be emitted.

[0129]

[0129] Fig. Id also illustrates two planes Cl and C2 in which the cross-sectional of lensing indentation 1 may be evaluated. The two planes Cl and C2 are both normal to the depth axis D and are spanned by the width and height axes at different locations along the depth axis D. Plane Cl is located closer to the second main surface and the bottom surface compared to plane C2. Since the width of the lensing indentation decreases towards the second main surface 1 b the cross-sectional area calculated in plane C 1 may be smaller than the cross-sectional area calculated in plane C2. Hereby, the lensing indentation 1 has a monotonically decreasing cross- sectional area going towards the second main surface from the first main surface (or raised section if present). The decrease in cross sectional area is brought by at least one of a width and a length of the lensing indentation which decreases going towards the second main surface from the first main surface (or raised section if present).

[0130]

[0130] Fig. 2a shows an alternative embodiment of the radome 1 used to form an antenna arrangement 10. Similar to the radome 1 of the antenna arrangement shown in figs. Ic-d the radome 1 of fig. 2a comprises a first main surface la, an opposite second main surface lb and a lensing indentation 11 defined by a bottom surface 12 and side walls 13 extending away from the second main surface lb. A difference between the radome 1 of figs. Ic-d and the radome of fig. 2a is that the radome 1 of fig. 2a comprises a raised section 14 protruding from the first main surface la wherein the lensing indentation 11 is formed in the raised section.

[0131]

[0131] The width of the raised section 14 may hereby be large enough to encompass the lensing indentation 11. For example, the raised section 14 has a width which is at least 150%, at least 200% or at least 300% of the maximum width of the lensing indentation. Similarly, the length of the raised section 14 may be large enough to encompass the lensing indentation 11. For example, the raised section 14 has a length which is at least one operational guided wavelength longer than the lensing indentation 11 or at least two operational guided wavelengths longer than the lensing indentation 11.

[0132]

[0132] A benefit with a raised section 14 surrounding the lensing indentation 11 is that the remaining part of the radome 1 (i.e. the parts other than the raised section 14) may be made thinner, whereby the radome 1 uses less material and becomes lighter. For example, the raised section 14 may allow the lensing indentation 11 to have a depth which is greater than the first thickness of the radome 1 measured offset from the raised section 14. However, with the raised section 14 it is possible to ensure that sufficient material is present in the vicinity of the antenna array element such that the desired lensing effect is achieved (e.g. such that a desired half-power beam width is achieved).

[0133]

[0133] A radome 1 with a raised section 14 may be used together with an absorber layer 3 as shown in fig. 2b. The opening of the absorber layer 31 may be tapered such that a dimension of the opening 31 of the absorber increases towards the radome 1. A tapered opening 31 may facilitate manufacturing.

[0134]

[0134] Fig. 3a shows a cross-sectional view of a radome 1 with a void space region 100. The void space region 100 has a depth d and extends from the first main surface la towards the second main surface lb. The void space region 100 may comprise a partial infill region 105 (see e.g. fig. 11) or a lensing indentation (see e.g. figs. 3b-c) as described below.

[0135]

[0135] Fig. 3b shows a cross-sectional view of a radome 1 with a lensing indentation 11 according to some implementations. The depth d of the lensing indentation 11 (here measured as the distance from the first main surface la to the bottom surface 12 along the depth axis D) is between 10% of the operational guided wavelength and 75% of the operational guided wavelength, such as about 25% of the operational guided wavelength. The first thickness T 1 of the radome 1 is defined as the distance between the first main surface la and the second main surface lb is preferably between 30% and 100% of the operational guided wavelength or more preferably around 50% of the operational guided wavelength. Hereby, the second thickness T2 is defined as the distance between the bottom surface 12 and the second main surface lb is between 10% of the operational guided wavelength and 40 % of the operational guided wavelength, such as about 25% of the operational guided wavelength.

[0136]

[0136] Fig. 3c shows a cross-sectional view of a radome 1 with raised section 14 and a lensing indentation 11 provided in the raised section 14 according to some implementations. The depth d of the lensing indentation (here measured as the distance from the first main surface 1 a to the bottom surface 12 along the depth axis D) is between 10% of the operational guided wavelength and 200% of the operational guided wavelength, preferably between 10% of the operational guided wavelength and 100% of the operational guided wavelength, such as about 25% of the operational guided wavelength. A deeper lensing indentation may be preferred since it may offer improved lensing performance making it easier to reach a desired radiation pattern.

[0137]

[0137] The third thickness T3 of the radome 1 defined here as the distance between the second main surface lb and topmost “plateau” surface of the raised section 14 is preferably between 30% and 70% of the operational guided wavelength or more preferably around 50% of the operational guided wavelength. Hereby, the local second thickness T2 defined as the distance between the bottom surface 12 and the second main surface lb is between 10% of the operational guided wavelength and 40 % of the operational guided wavelength, such as about 25% of the operational guided wavelength. The first thickness T1 defined as the distance between the first and second main surface la, lb at a location offset from any raised section 14 can be made very thin, such as less than 25% of the operational guided wavelength, or less than 15 % of the operational guided wavelength X.

[0138]

[0138] Figs. 4a and 4b shows a side view and perspective view respectively of a radome 1 with a lensing indentation 11 according to some implementations. The lensing indentation 11 is elongated along the length axis L and has a maximum length LI that corresponds to at least a majority of, i.e. more than 50% of, a length of the region occupied by the corresponding antenna array element. Preferably, the maximum length LI is at least 80% of the length of the region, at least 100% of the length of the region or at least 100% the length of the region plus a predetermined length, the predetermined length being at least one operational guided wavelength X or at least two operational guided wavelengths X.

[0139]

[0139] The elongated lensing indentation 11 may have a width in the width axis W which varies along the length axis L, as shown in figs. 4a and 4b. The width variation may be intermittent or periodic. For example, it has been found that to improve the antenna properties in terms of concentrating the antenna directivity in the azimuth plane (depth-width plane) and to broaden the half-power beamwidth, the width variation is periodic with a period P of between the operational guided wavelength X divided by four and the operational guided wavelength X, and preferably between 40% of the operational guided wavelength X and 60% of the operational guided wavelength X.

[0140]

[0140] Accordingly, the width of the lensing indentation 11 varies (optionally periodically) at its open end between a first width W 1 and a section width W2, wherein W1 > W2. Depending on whether the side walls 13 are slanted / curved or normal to the depth axis the width of the bottom surface 12 defining the closed end of the indentation 11 will also vary between a third width W3 at its largest and a fourth width W4 at its smallest, whereby W3 > W4. If the side walls 13 are normal to the depth axis W1 = W3 > W2 = W4. On the other hand, if the side walls 13 slanted (as shown in figs. 4a-b) or curved to form a convex lensing indentation 11 opening towards the radiation layer it may be that W1 > W2 > W3 > W4. In some implementations, the width W1 is at least 50% larger than the width W2 or W1 is at least twice as large as W2. Similarly, the width W3 at the bottom surface 12 may be at least 50% larger than the width W4, or the width W3 at the bottom surface 12 may be twice as large as the width W4.

[0141]

[0141] A similar variation (e.g. periodic) in width along the length axis may be present in each cross-section of the lensing indentation at each position along the depth axis.

[0142] The maximum width W 1 of the lensing indentation 11 (e.g. at the open end of the lensing indentation) may be below two times the operational guided wavelength . Preferably, however, the maximum width W1 of the lensing indentation is at or below 150% of the operational guided wavelength (i.e. 1.5 ) or at or below the operational wavelength (i.e. I X). Accordingly, the lensing indentation 11 may be made very narrow. This in combination with the fact that a single lensing indentation structure is used to cover multiple antenna apertures forming an antenna array element makes the design very space efficient. Additionally, this allows multiple antenna array elements to be placed in proximity, with each antenna array element having a corresponding lensing indentation 11.

[0142]

[0143] Figs. 5a and 5b shows a side view and perspective view respectively of a radome 1 with a lensing indentation 11 provided in a raised section 14 according to some implementations. As seen, the lensing indentation 11 may have the same dimension and properties as described in connection with figs. 4a and 4b above. The lensing indentation is provided in a raised section 14 having a maximum width W5 and maximum length L2 exceeding the maximum width W1 and maximum length LI of the lensing indentation 11. In some implementations, each raised section 14 is surrounded by a portion of the first main surface la. Since a single radome 1 may comprise a plurality lensing indentations 11 (each associated with, and arranged to overlap with, a corresponding antenna array element) multiple raised sections 14 may be provided as separate “islands” protruding from first main surface la, wherein each raised section 14 comprises a lensing indentation 11.

[0143]

[0144] Fig. 6a shows a top-down view of a radiation layer 20 according to some implementations. The radiation layer 20 comprises a plurality (in this case eight) antenna apertures 24a-j. Each antenna aperture 24a-j is a throughgoing opening in the radiation layer 20 and may have various shapes. In fig. 6a and 6b the antenna apertures 24a-j are dumbbell shaped but this only exemplary, and it is envisaged that the antenna apertures 24a-j could have different shapes, such as a rectangular shape, a stadium shape, or an S-shape.

[0144]

[0145] The antenna apertures 24a-j form an antenna array element 200. The antenna apertures 24a-j of the antenna array may be arranged in columns, separated along the width axis and rows separated along the length axis to form a matrix array. The exemplary antenna array element 200 of figs. 6a and 6b has two columns and four rows. The rows of each column may be aligned, or it is envisaged that the columns are offset from each other along the length axis to form a zigzag pattern of antenna apertures 24a-j.

[0145]

[0146] In some implementations, the antenna apertures 24a-j are elongated along the length axis L. Additionally or alternatively, the antenna array element 200 comprises more rows than columns whereby the antenna array element 200 as such becomes elongated along the length axis L.

[0146]

[0147] As illustrated in fig. 6b the antenna array element is associated with a region R of the radiation layer 20, i.e. the region which the antenna array element 200 occupies. The region may be defined as the smallest rectangle which covers all antenna apertures of the antenna array element 200 when viewed along the depth axis D, perpendicular to the length axis L and width axis W. Hereby each antenna array element 200 is associated with a width an array element length LR and array element width WR corresponding to the length and width of the region R.

[0147]

[0148] In some implementations, each antenna aperture 24a-j are elongated, such as about 0.5 operational guided wavelengths long and 0.1 operational guided wavelengths wide. Additionally, the antenna apertures are arranged with a center-to-center spacing between 0.4 and 0.7 operational wavelengths in the length direction and arranged with spacing about 0.5 operational wavelengths in the width direction. The center-to-center spacing may hereby be greater than the aperture length. This means that an exemplary antenna array element with four antennas in a 2x2 (two rows, two columns) configuration is at least 1.0 or more operational guided wavelengths long and 1.0 or less operational guided wavelengths wide or 1.5 or less operational guided wavelengths wide. As another example, an exemplary antenna array element with six antennas in a 3x2 (three rows, two columns) configuration is at least 1.5 or more operational guided wavelengths long and 1.0 or less operational guided wavelengths wide.

[0148]

[0149] In some implementations, the aspect ratio of the region of the antenna array elements is at least 1.5 to 1.0, at least 2.0 to 1.0 or at least 3.0 to 1.0 meaning that the antenna array elements are at least 1.5 times, at least 2.0 times or at least 3.0 times longer than they are wide. The antenna array elements fulfilling this aspect ratio may have at least two antennas and optionally four or more antennas, six or more antennas, or even eight or more antennas arranged in two or more columns. In some implementations, each column comprises between one and eight antennas although it is envisaged that each column may comprise more than four antennas. Each antenna array element may be associated with a single corresponding void space region for providing the lensing properties.

[0149]

[0150] Preferably, the elongated lensing indentation has a length which is approximately equal to or slightly longer (e.g. one or two A, longer) than the region length LR. The elongated lensing indentation may have a maximum width (see W 1 in figs. 4a-b, 5a-b) which is approximately equal to the region width WR. Preferably, the lensing indentation maximum width is smaller than the region width WR.

[0151] In some implementations, each antenna array element 200 is at least partially surrounded by one or more corrugations 27. The corrugations 27 are throughgoing openings in the radiation layer, but unlike the antenna apertures 24a-j the corrugations 27 do not open into a waveguide but opens into an electromagnetically shielded space for forming a quarter wavelength termination. This means that the corrugations 27 functions to suppress surface currents which otherwise may propagate along the radiation layer 20. That is, the absorber layer (see e.g. figs. Id and 2b) and the corrugation 27 may be used to improve isolation between multiple antenna array elements.

[0150]

[0152] Fig. 7 shows a top-down view of a radiation layer 20 with an antenna array element 200 occupying region R and two corrugations 27 on either side of the antenna array element 200. An exemplary lensing indentation 11 has been overlayed to show how the lensing indentation 11 overlaps with the antenna array element 200 when viewed along the depth axis D. As seen, the lensing indentation 11 is longer than the length of the region R occupied by the antenna array element. For example, the lensing indentation is at least one or at least two operational guided wavelengths longer than the region R. On the other hand the, the lensing indentation 11 is slightly narrower in width compared to the region R occupied by the antenna array element 200.

[0151]

[0153] The lensing indentation 11 is also adapted to fit between the corrugations 27.

[0152]

[0154] The lensing indentation 11 may be centered relative to the antenna array element 200 (i.e. relative the region R). Additionally, as described above, the lensing indentation 11 may have a width which varies periodically between a maximum width and a minimum width. The antenna apertures forming the antenna array element 200 may be arranged with the same periodicity, such that each maximum width portion of the lensing indentation 11 is centered relative an antenna aperture and each minimum width portion of the lensing indentation 11 is centered in a space between two lensing indentations, or vice versa.

[0153]

[0155] Fig. 8a shows a radiation layer 20 with a plurality (in this case eight) antenna array elements 200a-h. Each antenna array element 200a-h is acting as either a receiving element (RX) or a transmitting element (TX). For example, antenna array elements 200a-200d are transmitting elements and antenna elements 200e-h are receiving elements. In this embodiment, each antenna element comprises ten dumbbell shaped antenna apertures, arranged in a grid pattern of two columns and five rows, and corrugations. It is however envisaged that other shapes of the antenna apertures could be used or that a different number of antenna apertures could be used in each antenna array element 200a-h.

[0154]

[0156] Fig. 8b shows the first main surface la of a radome 1 for use with the radiation layer 20 of fig. 8a. The first main surface la of the radome 1 has a plurality oflensing indentations 1 la-h, one lensing indentation 1 la-h for each of the antenna array element 200a-h of the radiation layer in fig. 8a. A benefit with the comparatively small lensing indentations 11 a- h is that each antenna array element 200a-h may be provided with a lensing indentation to improve or modify the antenna properties even when the antenna array elements 200a-h are arranged close together.

[0155]

[0157] In some implementations, at least two antenna array elements 200a-h are provided in the radiation layer 20 and the at least two antenna array elements 200a-h are arranged at a distance of at least 90% of operational guided wavelength, such as at least 100% of the operational guided wavelength or two times the operational guided wavelength. Each antenna array element 200a-h may still be provided with a corresponding lensing indentation 1 la-h in the radome 1 since the lensing indentations 11 described herein may be made narrow and compact. Accordingly, it is possible to design antennas having antenna array elements 11 a-h arranged as desired and still enhance the performance of each antenna at ray element 11 a-h with a lensing indentation.

[0156]

[0158] Fig. 10a shows a cross-sectional view of a three layer multilayer antenna 2. The radiation layer 20 comprises antenna apertures 24a, 24b forming an antenna array element. As indicated above, the multilayer antenna 2 may be formed from more than two layers (see e.g. figs, la-b) and in the embodiment shown in fig. 9a the multilayer antenna comprises three layers, the radiation layer 20, an intermediate layer 21a and a bottom layer 21b. The intermediate layer 21a has a channel 211 for defining each waveguide path 25a, 25b and the radiation layer 20 and bottom layer 21b each comprises a metasurface to surround the channel(s) 211. Hereby, when the layers 20, 21a, 21b, are held together they form waveguide channels 25a, 25b for guiding electromagnetic signals to the antenna apertures 24a, 24b (when transmitting) or away from the antenna apertures 24a, 24b (when receiving).

[0157]

[0159] Compared to the embodiment of figs, la-b, the radiation layer 20 of fig. 9a comprises a metasurface 4. It is hereby envisaged that the radiation layer 20 may be a substantially flat layer (without metasurface, as in figs 1 a-b) or provided with a metasurface 4 on the surface facing the opposite direction from the radome. In general, many types of multilayer antennas (with two or more layers) may be used together with the radome of the present disclosure, wherein the radiation layer 20 is the top layer.

[0158]

[0160] In some implementations, there is at least one metasurface 4 arranged between any two adjacent layers in the multilayer antenna. In the example of fig. 9a, there is a metasurface 4 between the radiation layer 20 and the intermediate layer 21a in the form of the metasurface 4 on the radiation layer 20. There is also a metasurface 4 between the intermediate layer 21a and the bottom layer 21 b in the form of the metasurface 4 on the bottom layer 20 facing the intermediate layer. Other options are envisaged, for example the intermediate layer 21a may be provided with a metasurface on one or both sides, enabling the radiation layer 20 and / or the bottom layer 21b to have a flat surface facing the intermediate layer 21a.

[0159]

[0161] Optionally, a central conductor 212 is arranged inside each opening 211 of the intermediate layer 21a whereby coaxial waveguide channels 25a, 25b are realized. The central conductor 211 may be suspended by support stubs extending from the periphery of the channel 211 provided through the intermediate layer 21a.

[0160]

[0162] To further illustrate that the multilayer antenna 2 may be realized using any number of layers another exemplary multilayer antenna 2 is shown in fig. 9b. The multilayer antenna 2 comprises the radiation layer 20 with antenna apertures 24a, 24b, the intermediate layer 21a, the bottom layer 21c, an additional bottom layer 21c arranged between the bottom layer 21b and intermediate layer 21 as well as an additional top layer 21 d arranged between the radiation layer 20 and the intermediate layer 21a. By providing corresponding channels 211 in each of the intermediate layer 21a and the additional top and bottom layers 21c, 2 Id these layers cooperate to form comparatively large waveguide paths 25a, 25b (compared to the embodiment of fig. 9a). Optionally, a central conductor 212 is also provided in the intermediate layer 21a to realize a coaxial waveguide paths 25a, 25b. In the five-layer multilayer antenna 2 of fig. 9b is noted that the general design requirement of one metasurface 4 arranged between each adjacent pair of layers is observed. However, the person skilled in the art will appreciate that much like the number of layers it is also possible to vary which layer(s) are provided with the metasurface 4. For example, while each layer in figs. 9a and 9b comprises either one or zero metasurfaces 4 it is understood that one or more layers may comprise two metasurfaces 4.

[0161]

[0163] This type of multilayer antenna may be realized with very thin layers. For example, at least one of the layers has a total thickness below / . divided by four, below X divided by five or below X divided by six. Preferably, each layer has a total thickness below / . divided by four, below X divided by five or below X divided by six.

[0162]

[0164] The thickness of each individual layer is preferably less than 1 mm, although larger thicknesses are possible. In some implementations, the thickness of each layer is between 500 pm and 300 pm. All layers could have the same thickness, but it is also envisaged that the layers may have different thicknesses. For example, the bottom layer 21b (and / or layers 21c, 2 Id) or distribution layer 20 of figs, la-b may have a same thickness between 500 pm and 300 pm and the radiation layer 20 and / or intermediate layer 21a is thinner, having a thickness between 50 pm and 200 pm, e.g. about 100 pm. The above exemplary thicknesses are suitable for simple and cost effective manufacturing but are merely exemplary and can vary outside of these ranges, e.g. depending on the operational frequency. The above exemplary thicknesses are suitable for an operational frequency around 77 GHz.

[0163]

[0165] Fig. 10 illustrates how a corrugation 27 may be realized through the radiation layer 20 of a three layer multilayer antenna2. An opening is formed through the radiation layer 20 at a location offset from the antenna opening(s) 24 of an antenna array element. A corresponding opening 213 is provided in the intermediate layer 21a whereby a corrugation 27 is formed stretching from the surface of the radiation layer 20 facing the radome, through the radiation layer 20, through the intermediate layer 21 a whereby the corrugation 27 is terminated by the bottom layer 21b. Depending on the number of layers used to form the multilayer antenna 2, and the thickness of the layers, the number of layers the corrugation 27 penetrates through may be adjusted. Preferably, the depth of the corrugation 27 is about one eighth of the operational guided wavelength, whereby the round trip electrical length of the corrugation becomes one quarter of the operational guided wavelength.

[0164]

[0166] Fig. 11 shows a cross-sectional view of a radome 1 having a void space region 100 realized with a partial infill region 105. The partial infill region 105 comprises an infill geometry configured to leave void space or “pores” in the material to locally control the material density so as to form a lens. Partial infill regions 105 as such are typically used in 3D printing to reduce the weight of a printed part and / or reduce the amount of material needed to print a part.

[0165]

[0167] Various infill geometries may be used, as will be described below, and each infill geometry is associated with an infill geometry unit cell of a predetermined unit cell size. As an example, consider a cube infill geometry wherein a partial infill region comprises one or more layers of hollow stacked cubes. Each cube has an outer dimension of the unit cell size and by varying the wall thickness of infill of each cube it is possible to vary the infill ratio, herein referred to as R. A very thin wall thickness of each cube leads to a very low infill ratio R and as the wall thickness increases the fill ratio increases (in practice all the way to 100% infill ratio). The infill ratio R is a percentage indicating how much of a space is filled with material, 100% fill ratio is essentially a completely filled space and 0% is an empty space. To still allow the infill geometry unit cells to be created, a minimum infill ratio is typically 10% or 5% and may go to 0% if there is no need for mechanical support locally. This is furthermore depending on the 3D printing technique used, the unit cell size and the type (shape) of infill geometry.

[0166]

[0168] In some implementations, the infill geometry unit cell size is small compared to the operational guided wavelength. For example, the infill geometry unit cell size is smaller than 0.5 or smaller than 0.1 / .. Hereby, the unit cell geometry has been found to not distort the emitted electromagnetic waves while the more macroscopic local variations in material density (and thereby the effective local dielectric constant) over multiple unit cells may be utilized to create a lensing effect in manner similar to the lensing indentation described above.

[0167]

[0169] In fig. 11, partial infill unit cells are provided in the partial infill region 105 and multiple, such as at least twenty, at least thirty or at least fifty unit cells are provided spanning the width W and length L dimension of the partial infill region 105. By varying the infill ratio across the width W and / or length L dimension it is possible to achieve a lensing effect.

[0168]

[0170] The depth of the partial infill region may be smaller than the operational guided wavelength X, smaller than 0.5X or smaller than 0.3k. In some implementations, the depth of the partial infill region 105 is between 0.35k and 0.15k such as around 0.25k. One or more layers of unit cells may hereby be provided along the depth axis.

[0169]

[0171] Fig. 11 also illustrates exemplary infill ratio profiles along the x-axis (parallel to the width W direction).

[0170]

[0172] If the infill ratio R along x first increases from a minimum infill ratio at the edge of the partial infill region 105 to a maximum infill ratio (e.g. at the center of the partial infill region 105) and subsequently decreases again to the minimum fill ratio at the opposite edge of the partial infill region 105 this forms a concave partial infill profile. This partial infill profile may be used to mimic the effect of a convex lens. Two examples of concave partial infill functions are shown in the top graph of fig. 11. The partial infill ratio R may increase and decrease linearly along the x axis (solid line) or more smoothly (dashed line) as illustrated. This type of partial infill region 105 may be used to decrease the azimuth beamwidth of the antenna arrangement and increase the directivity of the antenna pattern.

[0171]

[0173] Alternatively, the infill ratio R may start from a comparatively higher infill ratio at the edge of the partial infill region 105 whereby the partial infill ration decreases to a comparatively lower infill ratio (e.g. at the center of the partial infill region 105) and then increases again to the comparatively higher fill ratio at the opposite edge of the partial infill region 105 along the x axis. This forms a convex partial infill profile which may be used to form a partial infill region that mimics the effect of a concave lens. Two examples of convex partial infill profiles are shown in the bottom graph of fig. 11. The partial infill ratio R may decrease and increase linearly along the x axis (solid line) or more smoothly (dashed line) as illustrated. This type of partial infill region 105 may be used to increase the azimuth beamwidth of the antenna arrangement.

[0172]

[0174] The partial infill profiles of fig. 11 are only examples and the person skilled in the art will appreciate that any arbitrary partial infill profile may be realized by locally varying the infill ratio of unit cells in the partial infill region 105. For example, it is envisaged that asymmetrical infill profiles (i.e. infill profiles which are not symmetrical about the center point of the partial infill region 105 which is aligned with the center point of the antenna array element) may be used. In some implementations, an asymmetrical partial infill profile is used to obtain an increased directivity in a direction that is not pcrpcndicul ar to the radome 1 , such as in a 45 degree angle from the broadside direction of the antenna array element.

[0173]

[0175] The constant infill region 106 surrounding the partial infill region 105 may have a constant infill ratio which does not vary along the surface of the radome 1. The constant infill region 106 may be a solid slab material or a 100 % infill material. Optionally, the constant infill region has an infill ratio matching the infill ratio at the edges of the partial infill region 105. It is noted that the infill ratio of the constant infill region 106 may be chosen arbitrarily based on desired material stability and e.g. weight constraints since the constant infill region 106 is not expected to participate in providing the desired lensing effects. That is, the infill ratio of the constant infill region 106 may be selected anywhere between 0% and 100%.

[0174]

[0176] In fig. 12a a cross-section of an example radome 1 with two partial infill regions 105. Each partial infill region 105 is associated with a respective antenna array element 200a, 200b and in fig. 12a the antenna apertures 24a, 24b of a first antenna array element 200a and the antenna apertures 24c, 24d of a second antenna array element 200b is shown.

[0175]

[0177] Analogously to the example lensing indentations discussed above, a single partial infill region 105 may be provided for an antenna array element 200a, 200b having multiple antenna apertures.

[0176]

[0178] In some implementations, to protect the partial infill region(s) 105 which may be fragile and / or prone to accumulate dirt, dust or water due to their open geometries, a first solid cover layer 103a may be provided between the partial infill region(s) 105 and the radiation layer 20 as shown in fig. 12a.

[0177]

[0179] Hereby, it is envisaged that the radome 1 according to some implementations comprises multiple layers 101, 102a, 102b, 103a, 103b as shown in fig. 12b. The layers 101, 102a, 102b, 103a, 103b may be of the same or different material, and it is even envisaged that the layers 101, 102a, 102b, 103a, 103b are manufactured using the same 3D printing process. Each layer may be made of a dielectric material, such as a plastic material.

[0178]

[0180] The one or more partial infill region 105 is realized in a first partial infill layer 102a of the radome 1. Below the partial infill layer 102a (i.e. between the partial infill layer 102a and the radiation layer 20) a first solid cover layer 103 a may be provided. The first solid cover layer 103a may be made of a solid slab material (i.e. 100% material infill) to provide structural stability and prevent ingress of dust, dirt or water.

[0179]

[0181] The radome 1 may comprise a solid core layer 101 arranged on top of the first partial infill layer 102a (i.e. the opposite side of the first partial infill layer 102a). The solid core layer 101 may provide structural rigidity to the radome 1 and may be realized as a solid slab (i.e. with 100% material infill). In case no other additional layers are provided on top of the solid core layer 101 the solid core layer 101 may define the second main surface of the radome 1. As described above, the second main surface is preferably flat to make the radome 1 easy to clean and prevent buildup of dust, dirt or water.

[0180]

[0182] In some implementations, to further enhance the beamforming properties of the radome 1 a second partial infill layer 102b is provided as shown in fig. 12b. The second partial infill layer 102b comprises one or more partial infill regions 105 to complement the beamforming properties of the one or more partial infill regions 105 of the first partial infill layer 102a. Hereby, the one or more partial infill regions 105 of the second partial infill layer 102b may be aligned with corresponding partial infill regions 105 of the first partial infill layer 102a. The partial infill regions 105 of the second partial infill layer 102b may have a partial infill ratio R that varies across the partial infill region 105 to provide the desired lensing effect.

[0181]

[0183] In some implementations, to protect the second partial infill layer 102b a second solid cover layer 103b may be arranged on top of the second partial infill layer 102b. The second solid cover layer 103b may be realized as a solid material slab (i.e. with 100% material infill) as opposed to the partial infill layer 102b which comprises regions with less than 100% material infill. Hereby, in some implementations the second solid cover layer 103b forms the second main surface of the radome 1 which preferably is flat to make the radome 1 easy to clean and prevent buildup of dirt / dust or accumulation of water.

[0182]

[0184] Figs. 13a-c show cross-sections, in a width-height plane, of example partial infill geometries. In fig. 13a a square or cube partial infill geometry is illustrated. In fig. 13b a triangle partial infill geometry is illustrated and in fig. 13c a hexagon (or honeycomb) partial infill pattern is shown. These partial infill patterns are merely examples, and other infill geometries may be used as will be appreciated by the person skilled in the art. The unit cell dimension may be a largest dimension of a square in fig. 13a, the largest dimension of a triangle in figure 13b and the largest dimension of a hexagon in fig. 13c. The cross-sectional patterns are extruded to form three-dimensional cubes or triangular cylinders or hexagonal cylinders which may be filled with a desired degree of material to reach the infill ratio R.

[0185] The size of the unit cells of fig. 13 are approximately the same in both width W and length direction L. The size of the unit cells in the depth direction may also be the same or different, for example the size of the unit cells in the depth direction are smaller than 0.5 . In some implementations, the unit cells have different sizes in the width and height direction. For example, while the unit cell size in the width direction is preferably kept small when the antenna pattern in the width-depth plane is to be manipulated by the radome, the unit cell size in the height direction may be larger such as at least twice as large, at least five times as large or even at least ten times as large. This may facilitate more efficient manufacturing (e.g. more rapid 3D printing).

[0183]

[0186] Fig. 14 illustrates an example linear unit cell 300 which may be used to realize the lensing indentation of e.g. figs. 3b-c or the partial infill region 105 of figs. 11 - 12 . The linear unit cell 300 is elongated, having a small extension AW in width and a small extension AD in depth. The linear unit cell 300 has a predetermined length AL which is one or more orders of magnitude larger than extension AD or AW. In some implementations, AL is smaller than 50% of the operational guided wavelength, such as between 50% and 25% of the operational guided wavelength. The unit cell comprises two slabs 301, 302 of completely, 100%, infilled dielectric material and centrally located empty space volume 303 between the two dielectric material slabs 301, 302. The total length extension of the two slabs is AL - CL wherein CL is the length extension of the empty space volume 303. It has been found that by varying the CL the effective dielectric constant of the linear unit cell 300 may be varied, a smaller value of CL brings a larger effective dielectric constant and a larger value of CL brings a smaller dielectric constant. Hereby, using e.g. computer simulations and optimization algorithms wherein an electromagnetic wave is propagated through a radome and the resulting antenna pattern downstream of the radome is analyzed it is possible to vary CL of a large number of linear unit cells 300 in the void space region of the radome to achieve a target antenna pattern. For example, this approach has been used to arrive at a lensing indentation shown in figs. 3b-c.

[0184]

[0187] It is noted that the linear unit cell 300 being very small in AW and AD the unit cell is larger along AL. Hereby, as described above, this unit cell 300 is well suited for manipulation of the antenna pattern in the width-depth plane (azimuth).

[0185]

[0188] A similar approach may be used for the radome of figs. 11 and 12a-b wherein the partial infill ratio of the partial infill geometry (e.g. as described in connection with figs. 13a-c) may be modified by an optimization algorithm to arrive at a radome achieving a target antenna pattern.

[0189] However, it is understood that computer simulations and optimizations are not mandatory and e.g. desirable beam width properties (wider or narrower beam) may be obtained by manually defining the partial infill ratio variation over the partial infill region, see e.g. the simple example partial infill ratio functions of fig. 11.

[0186]

[0190] In some implementations, when the linear unit cell 300 is used to realize the void space region the linear unit cell 300 is used with the constraint that the infill ratio (i.e. as controlled by the gap defined by CL) is constant or increasing in direction from the radiation layer through the radome (i.e. from the first main surface towards the second main surface). Resulting in a lensing indentation arranged to face the antenna array element.

[0187]

[0191] The linear unit cells 300 may also be oriented with a clockwise or counterclockwise rotation with respect to the antennas and / or antenna array element, such as oriented at ± 45 degrees. This rotation of the linear unit cells 300 may facilitate creating circularly polarized radiation. The rotated linear unit cells 300 may be used standalone as the void space region or in combination with a void space region realized using a partial infill or lensing indentation. When the rotated linear unit cells 300 are used standalone circular polarization is generated. When the rotated linear unit cells are used together with a void space region forming a partial infill region or a lensing indentation circularly polarized radiation is generated in addition to achieving the desired lensing effects.

[0188]

[0192] The rotated linear unit cells 300 may have a constant infill of about 50%. That is, CL / L = 0.5. The region populated with rotated linear unit cells 300 may have a depth of between 1 operational guided wavelength and 2 operational guided wavelength.

[0189]

[0193] The region populated with rotated linear unit cells 300 may be arranged above or below a second void space region configured to provide the lensing properties, as described above.

[0190]

[0194] In some implementations, the region populated with rotated linear unit cells 300 may be arranged to cover the entire radome, or at least a majority of the radome, whereas any optional further void space region used to create the desired antenna pattern are arranged only to overlay the one or more antenna array elements. It is also envisaged that the region populated with rotated linear unit cells 300 consists of a plurality of subregions, wherein the rotation direction (clockwise 45 degrees or counterclockwise 45 degrees) changes between the subregions. This configuration may facilitate enhanced polarization diversity which is beneficial in some antenna applications.

[0191]

[0195] It is envisaged that a same void space region may be used to provide both the desired lensing properties and circular polarization by utilizing the linear unit cell 300 to create a void space region that provides the desired antenna properties wherein the linear unit cells 300 are rotated about 45 degrees with respect to the elongation direction of the antennas or antenna array element. For example, the linear unit cells 300 may be rotated 45 degrees in any direction around the depth axis and CL optimized using an optimization algorithm to form a single void space region that promotes both the desired lensing properties and facilitates circular polarization. Such a void space region is preferably between 1 and 3 operational guided wavelengths thick.

[0192]

[0196] The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the radiation layer may be the radiation layer of various types of multilayer waveguides with two or more layers. Additionally, the depending on the type of antenna array elements used various shapes and sizes of the lensing indentation or partial infill region may be provided on the same radome, each lensing indentation or partial infill region being configured to cooperate with a respective antenna array element to obtain a desired antenna pattern and / or enhance the antenna pattern. Furthermore while some features have been described in connection with a lensing indentation (such as the absorber layer) it is understood that any such features may be combined with a partial infill region, and vice versa.

[0193]

[0197] Such and other obvious modifications must be considered to be within the scope of the present invention, as it is defined by the appended claims. Tt should be noted that the above- mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting to the claim. The word "comprising" does not exclude the presence of other elements or steps than those listed in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

Claims

CLAIMS1. An antenna arrangement (10) comprising: a radiation layer (20), an antenna array element arranged on the radiation layer (20), the antenna array element comprising a plurality of antennas distributed in a region having a region length and region width, each antenna being configured to transmit and / or receive electromagnetic radiation, and a radome (1) made of a dielectric material, the radome (1) having a first main surface (la) facing the radiation layer (20) and a second main surface (lb) arranged opposite of the first main surface (la), wherein the second main surface (lb) is substantially flat, wherein the first main surface (la) comprises at least one void space region (100), the at least one void space region (100) extending into the radome (1) towards the second main surface and comprises one or more void spaces and / or indentations acting as a lens, wherein the at least one void space region (100) has a maximum width (Wl) and a maximum length (LI), wherein the maximum width (Wl) is less than or equal to 200% of an operational guided wavelength, preferably less than 150% and more preferably less than 100% of an operational guided wavelength and wherein the maximum length (LI) is at least 50% of the length of the region of the antenna array element.

2. The antenna arrangement (10) according to claim 1 , wherein a first thickness (T1 ) of the radome (1), defined as a distance from the first main surface (la) to the second main surface (lb), is between the operational guided wavelength divided by four and the operational guided wavelength.

3. The antenna arrangement (10) according to any of the preceding claims, wherein the radome (1) is arranged at a separation distance from the radiation layer, wherein the separation distance is between 25% and 100% of the operational guided wavelength.

4. The antenna arrangement (10) according to any of claims 1 - 3, wherein the void space region (100) comprises a partial infill region, the partial infill region comprising partial infill geometry.

5. The antenna arrangement (10) according to claim 4, wherein the partial infill geometry has a unit cell size of less than 50% of the operational guided wavelength, or preferably less than 10% of the operational guided wavelength.

6. The antenna arrangement (10) according to any of claims 4 or 5, wherein the partial infill geometry has a partial infill ratio which, across a predetermined depth (D) of the radome (1), varies along the width (W) and / or length (L) direction.

7. The antenna arrangement (10) according to claim 6, wherein the partial infill ratio varies in accordance with a convex or concave function, along the width direction at the predetermined depth of the radome (1).

8. The antenna arrangement (10) according to any of claims 4 - 7, wherein the partial infill region is surrounded by a constant infill region featuring a same partial infill ratio.

9. The antenna arrangement (10) according to any of claims 4 - 8, wherein the radome (1) further comprises a first solid cover layer (103 a) arranged between the first main surface (la) and the radiation layer (20).

10. The antenna arrangement (10) according to any of claims 4 - 9, wherein the partial infill region is realized in a first partial infill layer and wherein the radome (1) further comprises a second partial infill layer (102b) comprising a partial infill region, the second partial infill region being arranged on the opposite side of the first radiation layer (102a) from the radiation layer (20).

11. The antenna arrangement according to claim 10, wherein the radome (1) further comprises a solid core layer (101) arranged between the partial first and second partial infill layer (102a, 102b).

12. The antenna arrangement (10) according to any of the preceding claims, wherein a local material density of the radome (1) is monotonically increasing towards the second main surface.

13. The antenna arrangement (10) according to any of the preceding claims, wherein the void space region is realized using a linear unit cell (300) having a width AW, a depth AD and a length AL wherein AL > AW and AL > AD, and wherein the linear unit cell (300) comprises a configurable central void portion of length CL.

14. The antenna arrangement (10) according to claim 13, wherein the length AL of the linear unit cell (300) is about 50% of the operational guided wavelength.

15. The antenna arrangement (10) according to any of claims 1 - 3 or claims 12 - 14, wherein the void space region (100) comprises a lensing indentation (11).

16. The antenna arrangement (10) according to claim 15, wherein the lensing indentation(11 ) is defined by a bottom surface (12) and side walls (13) extending from the periphery of the bottom surface (12) away from the second main surface (lb) wherein the bottom surface (12) is substantially flat.

17. The antenna arrangement (10) according to claim 16, wherein a second thickness (T2) of the radome (1) at the bottom surface (12) is at least 30% smaller than a first thickness (Tl) of the radome (1) between the first and second main surface (la, lb).

18. The antenna arrangement (10) according to any of claims 15 - 17, wherein the lensing indentation (11) is asymmetrical and / or arranged off-center with respect to the antenna array element region.

19. The antenna arrangement (10) according to any of claims 15 - 18, wherein the lensing indentation (11) is elongated along a length axis (L).

20. The antenna arrangement (10) according to claim 19, wherein the width (Wl) of the lensing indentation (11) varies along the length axis (L).

21. The antenna arrangement (10) according to claim 16 or claim 17, wherein the width of the bottom surface (12) at its maximum width (W3) is at least two times the width of the bottom surface (12) at its minimum width (W4) and / or wherein the width of the lensingindentation (11) at its maximum width (W 1) is at least two times the width of the lensing indentation (11) at its minimum width (W2).

22. The antenna arrangement (10) according to any of the preceding claims, wherein the maximum length (LI) is at least 80% of the length of the region of the antenna array element, at least 100% of the length of the region of the antenna array element or at least 100% of the length of the region of the antenna array element plus a predetermined distance, the predetermined distance being at least one operational guided wavelength.

23. The antenna arrangement (10) according to any of the preceding claims, wherein the first main surface (la) is substantially flat except for at least one raised section (14) protruding from the flat first main surface (la), and wherein said at least one void space region is arranged in the at least one raised section (14).

24. The antenna arrangement (10) according to claim 23, wherein each raised section (14) forms a frame surrounding the voids space region along a width axis (W) and a length axis (L).

25. The antenna arrangement (10) according to claim 23 or claim 24, wherein each raised section (14) is surrounded by a portion of the flat first main surface (la).

26. The antenna arrangement (10) according to claim 25, wherein the bottom surface (12) is in the same plane as the flat first main surface (la) or in a plane between the flat first main surface (la) and the flat second main surface (lb).

27. The antenna arrangement (10) according to any of the preceding claims, wherein the antenna array element comprises at least four antennas arranged in at least two columns, with each column comprising at least two antennas.

28. The antenna arrangement (10) according to claim 27, wherein the maximum width of the void space region along a width axis (W), is larger than a separation distance between the two columns.

29. The antenna arrangement (10) according to any of the preceding claims, wherein each antenna is elongated along a length axis (L).

30. The antenna arrangement (10) according to any of the preceding claims, further comprising: an absorber layer (3) arranged between the radome (1) and the radiation layer (20), wherein the absorber layer (3) comprises at least one opening (31) configured to enable the antenna array element of the radiation layer (20) to communicate with the void space region.

31. The antenna arrangement (10) according to claim 30, wherein the absorber layer (3) abuts at least one of: the radiation layer (20), and the first main surface (la) of the radome (1).

32. The antenna arrangement (10) according to claim 30 or claim 31, wherein the at least one opening (31) in the absorber layer (3) has an opening dimension which varies along a depth axis, perpendicular to a width axis and length axis.

33. The antenna arrangement (10) according to any of the preceding claims, wherein each antenna is an antenna aperture (24) extending through the radiation layer (2).

34. The antenna arrangement (10) according to claim 33, further comprising at least one distribution layer, the at least one distribution layer forming a waveguide for feeding the at least one antenna aperture (24).

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