SE1930410A1 - An antenna arrangement with a low-ripple radiation pattern - Google Patents

Abstract

An antenna arrangement (100) suitable for a vehicle radar transceiver. The antenna arrangement comprises a radiating layer (105) having a surface (110), the surface delimited by a surface boundary (115). One or more apertures (120) are arranged on the surface. The antenna arrangement further comprises one or more surface current suppressing members (130) arranged on the surface. The one or more surface current suppressing members are arranged to suppress a surface current from an aperture to the surface boundary.

Description

TITLE AN ANTENNA ARRANGEIVIENT WITH A LOW-RIPPLE RADIATIONPATTERN TECHNICAL FIELDThe present disclosure relates to antenna arrangements for vehicle radartransceivers. There are disclosed antenna arrangements with improved radiation patterns.

BACKGROUND Radar transceivers play an increasingly important role in modern vehicles. Theradar transceivers may be used for autonomous driving or for providing the driver with useful information.

A radar works by transmitting a signal in a direction of interest through anantenna arrangement. The transmitted signal is thereafter reflected by anobject in the direction of interest. Then, the reflected signal is received by theantenna arrangement and is processed. The processed reflected signal maygive information about, e.g., the range of the object relative to the radar andthe velocity of the object relative to the radar. ln some vehicular applications, the radiation pattern in the elevation dimensionof the antenna arrangement should preferably comprise a single narrow beam.This can be accomplished by, e.g., an array of antenna elements. This way,the field of view in the elevation dimension may be substantially parallel to theground. The radar may thereby avoid detecting uninteresting objects abovethe vehicle and it may also avoid unwanted ground reflections. The radiationpattern in the azimuth dimension of the antenna arrangement should, in theideal case, be uniform over the field of view. The field of view in the azimuthdimension preferably has an angle as wide as possible, e.g. 180 degrees. Realantenna arrangements, however, present a trade-off between the azimuth beam width and a ripple in the azimuth radiation pattern. A narrow azimuth beam width with low ripple reduces the field of view. A wider beam width withlarger ripple, on the other hand, transmits different amounts of power acrossthe beam, which potentially complicates the signal processing.

There is a need for antenna arrangements with an improved radiation pattern.

SUMMARY lt is an object of the present disclosure to provide an improved antennaarrangement. The antenna arrangement is suitable for a vehicle radartransceiver. The antenna arrangement comprises a radiating layer having asurface, the surface delimited by a surface boundary. One or more aperturesare arranged on the surface. The antenna arrangement further comprises oneor more surface current suppressing members arranged on the surface. Theone or more surface current suppressing members are arranged to suppress a surface current from an aperture to the surface boundary.

The surface currents scattered of the surface boundary and/or of neighboringslots give rise to unwanted radiation that disrupts the radiation pattern arisingfrom the one or more slots. The surface current suppressing memberssuppress the surface currents and therefore reduce the unwanted radiation.Consequently, the surface current suppressing members improve the radiationpattern of the antenna arrangement in terms of lowering the ripple while maintaining a desired lobe width.According to aspects, the one or more apertures are elongated slots.

This way, the radiating layer is cost-effective and high performing, in terms of,e.g., losses, and presents a desirable radiation pattern for, e.g., vehicle radars.

According to aspects, the one or more elongated slots extend in a first direction on the surface.

This way, the antenna arrangement can comprise an antenna array with, e.g. a narrow beam width in one dimension and a wide beam in another dimension.

According to aspects, at least one of the elongated slots extends in the firstdirection and at least one other of the elongated slots extends in a seconddirection on the surface. The second direction is different from, or evenorthogonal to, the first direction.

This way, the antenna arrangement may be used for a dual polarized antennaarrangement, wherein the radiation pattern is improved for both polarizations.

According to aspects, the one or more surface current suppressing memberscomprise at least one elongated element having an elongation direction in thefirst direction.

This way, one surface current suppressing member may suppress surface currents arising from several apertures extending in the first direction.

According to aspects, the one or more surface current suppressing members are arranged in connection to the surface boundary.

This way, the surface current suppressing members may suppress surface currents arising from several apertures on the radiating layer.

According to aspects, the one or more surface current suppressing membersare arranged in connection to the surface boundary and surround the one or more apertures.

This way, the surface current suppressing members may improve the radiationpattern in the azimuth dimension for any orientation of the apertures on the surface, which is an advantage.

According to aspects, the antenna arrangement comprises a plurality ofapertures, wherein at least one of the one or more surface current suppressingmembers is arranged between a first and second aperture in the plurality of QDGITUFGS.

This way, the surface current suppressing members may suppress surfacecurrents intermediate apertures on the radiating layer.

According to aspects, the antenna arrangement comprises a plurality ofapertures, wherein at least one of the apertures in the plurality of apertures is surrounded by the one or more surface current suppressing members.

This way, the surface current suppressing members may suppress surface currents in all directions from the surrounded aperture.

According to aspects, the one or more surface current suppressing members comprise one or more electromagnetic absorbers.

The electromagnetic absorbers suppress surface currents by attenuation. Oneadvantage of using electromagnetic absorbers is that they may be arrangedon the surface after the radiating layer has been manufactured.

According to aspects, at least one of the one or more electromagneticabsorbers is coated onto the surface.

This provides an easy to manufacture and low-cost antenna arrangement.

According to aspects, at least one of the one or more electromagnetic absorbers is arranged in a recess formed in the surface.

This way, it is possible to arrange the one or more electromagnetic absorbersflush with the surface. Such arrangement may save space, facilitate assemblyand may be used to avoid snagging of the electromagnetic absorbers during,e.g., antenna assembly.

According to aspects, the surface comprises a metalized coating on asupporting layer, and the one or more electromagnetic absorbers constitute part of the support layer.

This way, the antenna arrangement may comprise a support layer with slotcutouts, wherein every surface except predetermined areas are metalized. Thepredetermined areas then constitute the electromagnetic absorbers. Such antenna arrangement would be easy to manufacture and have a low-cost.According to aspects, the support layer comprises plastic.This way, the support layer would have a low cost and a low weight.

According to aspects, the support layer comprises a primer.

This way, it is easier to metallize the support layer.

According to aspects, the one or more surface current suppressing members COmpflSe One OI' ITIOFG QFOOVGS.

The grooves suppress surface currents by scattering the surface currents in acontrolled fashion. A surface current that interacts with the groove is scatteredas electromagnetic radiation, whereby its energy decreases and the current issuppressed. An advantage of a groove is that it may be manufactured in asimilar way as the aperture in the radiating layer. ln an embodiment of the antenna arrangement, the grooves and the aperturesare formed in a single layer, which is an advantage from a manufacturing point of view. ln an embodiment of the antenna arrangement, the grooves and the aperturesare formed in a single material, e.g. metal, which is an advantage from a manufacturing point of view.

According to aspects, the antenna arrangement comprises a frame, whereinthe radiating layer is arranged to be received in the frame, and wherein the one or more surface current suppressing members are arranged on the frame.

This way, different configurations of radiating layers may fit into the sameframe, thereby saving manufacturing costs. lt is possible that the radiatinglayer comprises a plurality of radiating layer modules that are arranged to bereceived in the frame. The frame is a structural support for the one or moreradiating layer modules, and the frame preferably comprises an electricallyconductive material. The one or more radiating layer modules may bereleasably attached to the frame for easy assembly, by, e.g., an interferencefit or a snap fit.

According to aspects, a vehicle comprises the antenna arrangement.

According to aspects, a radar transceiver for a vehicle comprises the antenna arrangement.

Generally, all terms used in the claims are to be interpreted according to theirordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means,step, etc." are to be interpreted openly as referring to at least one instance ofthe element, apparatus, component, means, step, etc., unless explicitly statedotherwise. Further features of, and advantages with, the present invention willbecome apparent when studying the appended claims and the followingdescription. The skilled person realizes that different features of the presentinvention may be combined to create embodiments other than those describedin the following, without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure will now be described in more detail with reference tothe appended drawings, where: Figure 1A shows a top view of a vehicle with a radar transceiver;Figure 1 B shows a side view of a vehicle with a radar transceiver;Figure 2 schematically illustrates an example antenna arrangement;Figure 3 illustrates example radiation patterns; Figures 4A and 4B show side views of example antenna arrangements; Figures 5A, 5B, and 5C illustrate example antenna arrangements with different configurations of surface current suppressing members; Figures 6 schematically illustrates an example antenna arrangement with dual polarizations;Figure 7 schematically illustrates an example antenna arrangement; Figure 8 schematically illustrates an example antenna arrangement comprising a frame;Figure 9 schematically illustrates an example antenna arrangement; Figure 10A, 1OB, and 1OC illustrate example antenna arrangements with different configurations of surface current suppressing members; Figure 11 schematically illustrates an example antenna arrangement; Figure 12A, 12B and 12C illustrate example antenna arrangements with different configurations of surface current suppressing members.

DETAILED DESCRIPTION Aspects of the present disclosure will now be described more fully withreference to the accompanying drawings. The different devices and methodsdisclosed herein can, however, be realized in many different forms and shouldnot be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

The terminology used herein is for describing aspects of the disclosure onlyand is not intended to limit the invention. As used herein, the singular forms"a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

There are disclosed herein various types of antenna arrangements suitable forvehicle radar transceivers. Figures 1A and 1B schematically illustrate anexample vehicle 101 comprising a radar transceiver 102. l\/lore specifically,Figure 1A shows a top view of the vehicle, wherein the radar transceiver isarranged on the front of the vehicle. Figure 1A also shows a radiation pattern103 of the radar transceiver in the azimuth dimension 104. The radiationpattern, or antenna pattern, or far-field pattern, is the angular dependentstrength of the electromagnetic radiation from an antenna arrangement in theradar transceiver. lf an antenna arrangement radiates equally in a span ofangles (e.g. 180 degrees) in an angular dimension (e.g. azimuth), the radiationpattern is uniform in that span. lf, on the other hand, the antenna arrangementis directive, the highest radiated power is contained in a main lobe. A mainlobe has an angular width in degrees, which may be specified by the half powerbeam width, HPBW, which is the angular span between two angular pointswhere the radiated power is half of its maximum value. Figure 1 B shows a sideview of the vehicle and the radiation pattern 103 of the antenna arrangementin the elevation dimension 105. lt is appreciated that the radar transceiver canbe placed on other locations on the vehicle, such as on the sides or in a rearward facing position. Furthermore, it is appreciated that the disc|osedantenna arrangements may be used for other radar transceivers than vehicleradar transceivers, or for other radio frequency applications, such ascommunication systems, positioning systems etc.

The herein disc|osed antenna arrangements have the ability of presenting aradiation pattern with a main lobe that is narrow in the elevation dimension andthat is wide with a low ripple in the azimuth dimension. Such pattern allows forthe detection of objects in a direction substantially parallel to the ground, in awide angle from the vehicle, while simultaneously avoiding undesired groundreflections and undesired detection above the vehicle. For a vehicle radartransceiver, a narrow main lobe in the elevation dimension may, e.g., be apattern which covers an angular span of up to 40 degrees, and preferably 15degrees. The azimuth dimension main lobe width for a vehicle radartransceiver may be on the order of 180 degrees.

A ripple in the main lobe is a variation of the radiation power versus the angle(in e.g. the azimuth dimension) within the main lobe. lf the amplitude of theripple is larger than half of the maximum radiated power, the radiation patternwill no longer comprise a single main lobe. The ripple may be periodic oraperiodic versus the angle.

Figure 2 shows an antenna arrangement comprising slot antennas arrangedin an antenna array. The antenna arrangement comprises a radiating layer 105having a surface 110. The surface is delimited by a surface boundary 115. Theradiating layer has two faces and is associated with a thickness. The thicknessis much smaller than the dimension of the faces. A slot antenna normallycomprises an electrically conductive surface with a cut out portion, i.e. a slot.The conductive surface acts as a ground plane. The conductive surfacecomprises a good electrical conductor, e.g. copper. The slot is normallysubstantially rectangular, where the first sides have a length corresponding ahalf of the wavelength of the intended radio frequency signal and the secondsides have a length substantially shorter than the first sides, e.g. a tenth of the length of the first sides. The corners may be rounded for an improved bandwidth of the slot antenna. The bandwidth is the frequency span which theantenna can transmit and/or receive radio frequency signals. For furtherbandwidth improvements, the slot aperture can have a dumbbell shape, i.e.the two short sides have oval shapes. Other slot aperture shapes that are substantially rectangular are also possible. lt should be noted that the disclosed antenna arrangement may comprise anyaperture. Thus, the one or more apertures 120 are optionally elongated slotsin the disclosed antenna arrangement 100. For readability, however, the non-limiting example of the one or more apertures being elongated slots is usedthroughout the Detailed Description.

A plurality of slot antennas can form an array. For example, a plurality ofvertically elongated slots may be stacked vertically. ln such vertical stack, theslots may be arranged in a glide symmetry fashion for a small vertical distancebetween the slots. The glide symmetry in Figure 2 comprises arranging everysecond slot in the vertical stack in a horizontal translation (along direction B),thereby having a vertical symmetry line (along direction A). The plurality ofvertically elongated slot antennas may also be arranged horizontally for ahorizontal array. A combination of horizontal and vertical arrangements of the slots is also possible.

Figure 3 shows radiation patterns in the azimuth dimension for different slotantenna arrangements, wherein the slots are oriented such that they areelongated vertically (in direction A of Figure 2). An ideal slot antenna with aninfinite ground plane presents a perfectly uniform radiation pattern 301 overspan of 180 degrees in the azimuth dimension. However, due to a finite groundplane, a real conventional slot antenna presents a ripple 304 in the radiationpattern 303 in the azimuth dimension. This ripple may be reduced at the costof making the beam narrower, as in 302. The finite ground plane results insurface currents being scattered at ground plane edges and/or at anyneighboring slots. Here, the surface currents arise from the slot apertures. lnother words, discontinuities in the ground plane give rise to the scattering. lfthe ground-plane were infinitely large, there would be no scattered surface currents arising from the ground plane edges. The scattered surface currentscause unwanted radiation from the antenna arrangement, which disrupts the radiation pattern arising from the slot aperture.

Figure 2 i||ustrates an example antenna arrangement of the present disclosure.I\/|ore detailed views and various embodiments of the disclosed antennaarrangement are shown in Figures 4A-12D. The disclosed antennaarrangement 100 comprises a radiating layer 105 having a surface 110, thesurface 110 delimited by a surface boundary 115. One or more apertures 120are arranged on the surface. The antenna arrangement further comprises oneor more surface current suppressing members 130 arranged on the surface110, wherein the one or more surface current suppressing members arearranged to suppress a surface current from an aperture 120 to the surfaceboundary 115. The surface currents scattered at the surface boundary 115and/or at any neighboring slots give rise to unwanted radiation that disruptsthe radiation pattern arising from the one or more slots. The surface currentsuppressing members suppress the surface currents and therefore reduce theunwanted radiation. Consequently, the surface current suppressing membersimprove the radiation pattern of the antenna arrangement in terms of loweringthe ripple while maintaining a wide main lobe. The radiation pattern of thedisclosed antenna arrangement is therefore more uniform and resembles the flat radiation pattern 301 in Figure 3.

The surface 110 of the radiating layer 105 is electrically conductive. However,it is appreciated that a plastic film, or such, may cover the radiating layer. Thus,an outer surface of the antenna arrangement 100 is not necessarily electricallyconductive. Thus, in an example embodiment, the radiating layer comprises ametalized plastic. Then, either or both faces of the plastic layer can bemetalized, i.e. a metallization can constitute the surface 110.

The surface 110 is not necessarily a planar surface. lt is appreciated that othersurface shapes are possible, such as surfaces having an arcuate form in oneor two dimensions, as in, e.g., conformal antennas. Figure 9 i||ustrates an example antenna arrangement wherein the surface has an arcuate form. The 11 surface boundary may, for example, be rectangular, circular, or any otherclosed formed shape.

The antenna arrangement 100 may comprise one or more elongated slots 120extending in a first direction A on the surface 110. The one or more elongatedslots extending in the direction A may, for example, form an array in thedirection A and/or in a direction perpendicular to the direction A.

Figure 2 shows an example antenna arrangement 100 wherein a plurality ofelongated slots 120 extend in the direction A. Two surface current suppressingmembers, also extending in the direction A, are arranged at respective sidesof the surface 110, the sides extending in the direction A. ln this exampleantenna arrangement, the two surface current suppressing members improvethe radiation pattern in the azimuth dimension for all slot antennas, since thesurface current suppressing members suppress surface currents from the slotsto the surface boundaries extending in the direction A, and thereby reducesunwanted scattering of the surface currents. Thus, according to some aspects,the one or more surface current suppressing members 130 comprise at leastone elongated element having an elongation direction in the first direction A.Figure 7 shows a similar antenna arrangement with an array in the firstdirection A.

Figure 6 shows an example antenna arrangement 100 wherein at least one ofthe elongated slots 120 extends in the first direction A and at least one otherof the elongated slots extends in a second direction B on the surface 110. Thesecond direction B is different from, or even orthogonal to, the first direction A.Such slot arrangements may be used for a dual polarized antennaarrangement, wherein the radiation pattern is improved for both polarizations,since surface current suppressing members suppress unwanted radiation from scattered surfaces currents on all sides of the surface 110. ln the example antenna arrangements 100 in Figures 2,5A,5B,5C,6,7, and 8,the one or more surface current suppressing members 130 are arranged inconnection to the surface boundary 115. Figures 4A and 4B show details ofexample surface boundaries 115. ln Figure 4A, the surface boundary 12 comprises a 90-degree corner. As such, the surface current suppressingmembers is arranged in connection to the corner. ln Figure 4B, the surfaceboundary comprises a rounded corner. As such, the surface currentsuppressing members is arranged in the vicinity 410 of the corner. lt isappreciated that other shapes of the surface boundary are possible. lt is alsoappreciated that the surface current suppressing member may extend over thesurface boundary, thereby the surface current suppressing member may partlybe arranged on the surface 110 and partly on an adjacent surface 420. Theadjacent surface may be arranged, for example, 90 degrees relative to thesurface 110, although other angles are also possible. ln the example embodiment of the antenna arrangement in Figure 6, the oneor more surface current suppressing members 130 are arranged in connectionto the surface boundary 115 and surround the one or more apertures 120.Here, to surround means to form a perimeter around the surrounded object,as shown in Figure 6. lt is, however, appreciated that small gaps can be formedin the perimeter without loss of function. ln this type of configuration, thesurface current suppressing members may improve the radiation pattern in theazimuth dimension for any orientation of the slots on the surface 110, which isan advantage. ln the example embodiment of the antenna arrangements in Figures10A,10B,10C, and 12A, where each antenna arrangement comprises aplurality of apertures 120, at least one of the one or more surface currentsuppressing members 130 is arranged between a first and second aperture inthe plurality of apertures. Arranged between here means to be located on astraight line drawn between two adjacent slots, see, e.g., line D in Figure 10B or line E in Figure 10C. ln the example embodiment of the antenna arrangement in Figure 11, whichcomprises a plurality of apertures 120, at least one of the apertures in theplurality of apertures is surrounded by the one or more surface current suppressing members. 13 ln the disclosed antenna arrangement 100, the one or more surface currentsuppressing members 130 may comprise one or more electromagneticabsorbers. The electromagnetic absorbers suppress surface currents byattenuation. An electromagnetic absorber generally comprises lossy materialsthat attenuate transmission or reflection of electromagnetic radiation. As such,an electromagnetic absorber should be neither a good electrical isolator (as in,e.g., rubber) nor a good electrical conductor (as in, e.g., copper). An exampleof an electromagnetic absorber is a foam material loaded with iron and/orcarbon. Electromagnetic absorbers can be resonant, i.e. a particular frequencyis attenuated (e.g. 30 GHz), or broadband, i.e. a span of frequencies isattenuated (e.g. 1 GHz to 40 GHz). The attenuation of electromagneticradiation in a direction is dependent on the thickness of the electromagneticabsorber in the same direction. One example of attenuation per length is 10dB/cm at 2 GHz. Another example is 150 dB/cm at 30 GHz. These twoexamples of attenuation per length could be applicable to the disclosed antenna arrangement 100.

Figure 5A illustrates a side view of an example antenna arrangement 100wherein the one or more electromagnetic absorbers are arranged on top of thesurface 110. Note that the height (extending in direction C in Figure 5A) of theradiating layer 105 is not necessarily to scale compared to the rest of the figure.At least one of the one or more electromagnetic absorbers 130 may be coated51 1 onto the surface 1 10 for a quick and cost-effective manufacturing process.The coating may comprise spraying an electromagnetic absorbing materialonto the surface 110. Furthermore, the one or more electromagnetic absorbers130 may be attached to the surface 110 by an adhesive.

Figure 5B illustrates a side view of an example antenna arrangement 100wherein at least one of the one or more electromagnetic absorbers 130 isarranged in a recess 512 formed in the surface 110. Note that the height(extending in direction C in Figure 5B) of the radiating layer 105 is notnecessarily to scale compared to the rest of the figure. Thereby, it is possibleto arrange the one or more electromagnetic absorbers flush with the surface110. Such arrangement may save space, facilitate assembly and may be used 14 to avoid snagging of the electromagnetic absorbers during, e.g., antennaassembly.

Figure 5C illustrates a side view of an example antenna arrangement 100wherein the surface 110 comprises a metalized coating on a support layer 510,and the one or more electromagnetic absorbers 130 constitute part of thesupport layer. The radiating layer thus comprises the support layer and themetallization. Note that the height (extending in direction C in Figure 5C) of theradiating layer 105 is not necessarily to scale compared to the rest of the figure.On the support layer, the side opposite of the surface 100 may also bemetalized. Preferably, the insides of the slots are also metalized. ln otherwords, the antenna arrangement may comprise a support layer with slotcutouts, wherein every surface except predetermined areas are metalized. Thepredetermined areas then constitute the electromagnetic absorbers 130. Thepredetermined areas could for example be covered with a removable film when the support layer is metalized. ln an example embodiment of the disclosed antenna arrangement, the supportlayer comprises a plastic, wherein the plastic has electromagnetic absorbingproperties at the frequency band of operation of the antenna arrangement. l\/letallization of plastics can be done in two steps, wherein a primer is firstapplied onto a plastic surface before the plastic surface is coated with adesirable metal. ln the present disclosure, desirable metals for themetallization of plastics have low loss and high electrical conductivity, e.g.copper, silver, and gold. l\/lany other metals and alloys are also possible.Examples of suitable primers are nickel, chromium, palladium and titanium,although many other materials are also possible. Therefore, in anotherexample embodiment of the disclosed antenna arrangement, areas coatedonly with the primer comprise the electromagnetic absorbers 130, i.e. thesupport layer comprises a primer. ln other words, the antenna arrangementmay comprise a plastic layer with slot cutouts, wherein every surface is coated with a primer. Thereafter, every area except predetermined areas are metalized. The predetermined areas constitute the electromagnetic absorbers130.

Figures 12A, 12B, 12C and 12D show example antenna arrangements 100.Here the one or more surface current suppressing members 130 comprise oneor more grooves. The grooves suppress surface currents by scattering thesurface currents in a controlled fashion. A surface current that interacts withthe groove is scattered as electromagnetic radiation, whereby its energydecreases and the current is suppressed. Surface currents, arising from theone or more slots, that are scattered at the surface boundary 115 and/or at anyneighboring slots degrade the radiation pattern of the antenna arrangement100. By scattering the surface current in a controlled fashion, the desiredradiation pattern can be maintained. The insides of the grooves are preferably electrically conductive.

Figures 12B, 12C, and 12D show different embodiments of the antennaarrangement, viewed along cross section F in Figure 12A. Note that the height(extending in direction C in the figures) is not necessarily to scale compared tothe rest of the figures. ln Figure 12B and 12C, the slots 120 are cutoutspenetrating through the surface 110 and provides passages, whereas thegrooves are recesses that do not provide passages. Figure 12B illustrates thatthe grooves may be shallower than the slots; Figures 12C and 12D illustratethat the slots may be more or equally shallow compared to the grooves. lnother words, the thickness (in direction C in the figures) radiating layersurrounding the groove can be larger compared to the thickness surroundingthe slots. Figure 12D shows an embodiment wherein the one or more groovescomprise two layers. l\/lore specifically, the grooves penetrate through theradiating layer 105 and extends into a support layer 1205. The continuation ofthe groove in the support layer 1205 does not necessarily size match the partof the groove opening in the radiating layer. For example, the continuation maybe wider. The purpose of the support layer is to seal the grooves shut. Thesupport layer is preferably electrically conductive. The support layer may ormay not be an integral part of an optional distribution layer. Commonly inantenna arrangements, there is a distribution layer facing the surface of the 16 radiating layer not intended to radiate. The distribution layer distributes radiofrequency signals to and from the slots in the radiating layer.

Optionally, the one or more grooves 130 are elongated grooves with a secondwidth W2 matching a first width W1 of one of the elongated slots 120. Theelongated slot has a length in the elongation direction (A in Figure 12A) andwidth W1, wherein the width is transverse to the elongation direction (W1extends in direction B in Figure 12A and 12B). The groove has a length in theelongation direction and a width W2, wherein the width W2 is measured orthogonally to the elongation direction.

The antenna arrangement 100 may optionally comprise a distribution layerwith transmission lines based on gap waveguide technology. The transmissionline is used for conveying radio frequency signals. A transmission line basedon gap waveguide technology is generally built up of two parts; a metamaterialstructure surface and a flat metal surface being placed in close proximity toone another, but not necessarily in direct contact. The metamaterial structuresurface may for example comprise repetitive conductive pins or repetitiveconductive cavities. A metamaterial structure surface sometimes referred toas an artificial magnetic conductor. The metamaterial structure creates abarrier preventing the electromagnetic waves from propagating in undesireddirections. ln this way, the metamaterial structure replaces all but one wall inrectangular waveguides. This is done without requiring a perfectly sealedmetallic enclosure, which is an advantage.

Figure 8 shows an example antenna arrangement 100 comprising a frame710, wherein the radiating layer 105 is received in the frame, and wherein theone or more surface current suppressing members130 are arranged on theframe. This way, different configurations of radiating layers may fit into thesame frame, thereby saving manufacturing costs. lt is possible that theradiating layer comprises a plurality of radiating layer modules that arearranged to be received in the frame. The frame is a structural support for theone or more radiating layer modules, and the frame preferably comprises anelectrically conductive material. The one or more radiating layer modules may 17 be releasabiy attached to the frame for easy assembly, by, e.g., an interference fit or a snap fit.

According to some aspects, a vehicle 101 comprises the antenna arrangement100.

According to some aspects, a radar transceiver 102, for a vehicle, comprises the antenna arrangement 100.

Claims (19)

CLAIIVIS

1. An antenna arrangement (100) for a vehicle radar transceiver, the antenna arrangement comprising: a radiating layer (105) having a surface (110), the surface (110) delimited by a surface boundary (115);one or more apertures (120) arranged on the surface (110); and one or more surface current suppressing members (130) arranged on thesurface (110), wherein the one or more surface current suppressing membersare arranged to suppress a surface current from an aperture (120) to thesurface boundary (115).

2. The antenna arrangement (100) according to any previous c|aim, whereinthe one or more apertures (120) are elongated slots.

3. The antenna arrangement (100) according to c|aim 2, wherein the one ormore elongated slots extend in a first direction (A) on the surface (110).

4. The antenna arrangement (100) according to c|aim 2, wherein at least oneof the elongated slots extends in the first direction (A) and at least one other ofthe elongated slots extends in a second direction (B) on the surface (110),where the second direction (B) is different from, or even orthogonal to, the firstdirection (A).

5. The antenna arrangement (100) according to any previous c|aim, whereinthe one or more surface current suppressing members (130) comprise at leastone elongated element having an elongation direction in the first direction (A).

6. The antenna arrangement (100) according to any previous c|aim, whereinthe one or more surface current suppressing members (130) are arranged in connection to the surface boundary (115).

7. The antenna arrangement (100) according any of claims 1-4, wherein theone or more surface current suppressing members (130) are arranged inconnection to the surface boundary (115) and surround the one or more apertures (120).

8. The antenna arrangement (100) according to any of c|aims 1-5 comprisinga plurality of apertures (120), wherein at least one of the one or more surfacecurrent suppressing members (130) is arranged between a first and secondaperture in the plurality of apertures.

9. The antenna arrangement (100) according to any of c|aims 1-4 comprisinga plurality of apertures (120), wherein at least one of the apertures in theplurality of apertures is surrounded by the one or more surface current suppressing members.

10. The antenna arrangement (100) according to any previous claim, whereinthe one or more surface current suppressing members (130) comprise one or more electromagnetic absorbers.

11. The antenna arrangement (100) according to claim 10, wherein at leastone of the one or more electromagnetic absorbers (130) is coated (511) ontothe surface (110).

12. The antenna arrangement (100) according to any of claim 10 or claim 11,wherein at least one of the one or more electromagnetic absorbers (130) is arranged in a recess (512) formed in the surface (110).

13. The antenna arrangement (100) according to any of c|aims 10-12, whereinthe surface (110) comprises a metalized coating on a supporting layer (510),and the one or more electromagnetic absorbers (130) constitute part of the support layer.

14. The antenna arrangement (100) according to claim 13 wherein the supportlayer (510) comprises plastic.

15. The antenna arrangement (100) according claim 13 wherein the supportlayer (510) comprises a primer.

16. The antenna arrangement (100) according to claim 1-9, wherein the oneor more surface current suppressing members (130) comprise one or more grooves.

17. The antenna arrangement (100) according any previous claim, comprisinga frame (710), wherein the radiating layer (105) is arranged to be received in the frame (710), and wherein the one or more surface current suppressingmembers (130) are arranged on the frame (710).

18. A vehicle (101) comprising the antenna arrangement (100) according anyof c|aims 1-17.

19. A radar transceiver (102) for a vehicle, the radar transceiver comprisingthe antenna arrangement (100) according any of c|aims 1-17.