TECHNICAL FIELD

Various example embodiments generally relate to the field of radio technologies. In particular, some example embodiments provide an antenna, an antenna arrangement and an antenna device.

BACKGROUND

Various different radio technologies may be supported by a mobile device. These technologies may include cellular technologies, such as 2G/3G/4G radio, as well as non-cellular technologies. In the 5G New Radio (NR) technology, as specified by the 3 ^rd Generation Partnership Project (3GPP), the used frequency range is expanded from the so-called sub-6 GHz to mmWave frequency, e.g., frequencies between 20 GHz and 70 GHz. In mmWave frequencies, an antenna array may be used to form a beam with higher gain, for example to overcome higher path loss in the propagation media. However, antenna radiation pattern and array beam pattern with higher gain may result in a narrower beam width. Beam steering techniques, such as for example phased antenna array, may be utilized to implement on-demand beam steering towards different directions. Moreover, additional functionalities may be added on the way towards 6G, such as for example joint communication and sensing, for example RADAR (radio detection and ranging) applications, such as for example room occupancy sensing, human activity detection, signs-of-life (vital sign) detection, or the like. Such applications may utilize the mmWave frequency range.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

Example embodiments of the present disclosure enable the control of the radiation patterns of antenna elements in an array. In particular, example embodiments improve the uniformity of the radiation patterns of antenna elements in an array. The foregoing and other benefits may be achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description, and the drawings. According to a first aspect, an antenna comprises: at least one dielectric substrate layer; an electrically conducting ground plane; at least one electrically conducting board layer mounted parallel to the ground plane, the at least one board layer being electrically connected to the ground plane, wherein a cavity is formed through the at least one dielectric substrate layer and the at least one board layer; and at least one radiating element, wherein the at least one radiating element comprises at least one electrically conducting radiating layer, wherein the at least one radiating layer and the at least one board layer form a pair of slots, the pair of slots extending over the cavity.

According to an example embodiment of the first aspect, two opposite edges of the at least one radiating layer are electrically connected to the at least one board layer.

According to an example embodiment of the first aspect, two opposite edges of the at least one radiating layer are contiguous with the at least one board layer.

According to an example embodiment of the first aspect, the at least one board layer comprises a surface layer, and wherein the at least one radiating layer extends in a plane of a surface layer.

According to an example embodiment of the first aspect, the at least one board layer comprises a surface layer, and wherein the at least one radiating layer extends below a plane of a surface layer.

According to an example embodiment of the first aspect, the at least one board layer comprises a surface layer, and wherein the at least one radiating layer extends above a plane of a surface layer.

According to an example embodiment of the first aspect, the at least one board layer is electrically connected to the ground plane by a plurality of electrically conducting vias extending through the at least one dielectric substrate layer and the at least one board layer.

According to an example embodiment of the first aspect, the antenna further comprises at least one feed line configured to apply a differential feed to the at least one radiating element.

According to an example embodiment of the first aspect, the at least one radiating layer comprises a single radiating layer or a least two stacked radiating layers.

According to an example embodiment of the first aspect, at least one open slot extends in the at least one radiating layer.

According to an example embodiment of the first aspect, at least one stub extends from the at least one radiating layer.

According to a second aspect, an antenna arrangement comprises at least one antenna, wherein the at least one antenna may be according to any example embodiment of the first aspect, wherein the antenna arrangement further comprises a first electromagnetic band gap structure comprising at least one first electromagnetic band gap structure arrangement, the first electromagnetic band gap structure arrangement comprising a periodic planar arrangement of electrically conducting rectangular elements mounted parallel to the ground plane.

According to an example embodiment of the second aspect, each of the electrically conducting rectangular elements is electrically connected to the ground plane by an electrically conducting vias extending through the at least one dielectric substrate layer and the at least one board layer.

According to an example embodiment of the second aspect, the first electromagnetic band gap structure comprises one of the at least one first electromagnetic band gap structure arrangement on either side of one of the at least one antenna along an electric field vector of the antenna.

According to an example embodiment of the second aspect, the first electromagnetic band gap structure comprises a plurality of the at least one first electromagnetic band gap structure arrangement, wherein the first electromagnetic band gap structure arrangements are interleaved with the radiating elements along an electric field vector of the antenna, the first electromagnetic band gap structure arrangements enclosing the radiating elements.

According to an example embodiment of the second aspect, a dimension of the first electromagnetic band gap structure arrangement along a magnetic field vector of the antenna is larger than a dimension of the antenna along the magnetic field vector of the antenna.

According to an example embodiment of the second aspect, a dimension of the rectangular element along a magnetic field vector of the antenna is larger than a dimension of the rectangular element along an electric field vector of the antenna.

According to a third aspect, an antenna arrangement comprises at least one antenna, wherein the at least one antenna may be according to any example embodiment of the first aspect, wherein the antenna arrangement may be according to any example embodiment of the second aspect, wherein the antenna arrangement further comprises a second electromagnetic band gap structure comprising at least one second electromagnetic band gap arrangement, the second electromagnetic band gap arrangement comprising a planar arrangement of two electrically conducting stripes mounted parallel to the ground plane and parallel to each other, the second electromagnetic band gap arrangement extending between two antennas.

According to an example embodiment of the third aspect, the second electromagnetic band gap structure comprises a plurality of the at least one second electromagnetic band gap arrangement, wherein the second electromagnetic band gap arrangements are interleaved with the antennas, the second electromagnetic band gap arrangements enclosing the antennas.

According to an example embodiment of the third aspect, the antennas are aligned along a magnetic field vector of the antennas, and wherein a length of the two electrically conducting stripes is aligned along an electric field vector of the antennas.

According to a fourth aspect, antenna device comprises: at least one antenna according to any example embodiment of the first aspect, or at least one antenna arrangement according to any embodiment of the second or third aspect; and an antenna radome, the antenna radome comprising: a dielectric cover; a conductive pattern layer disposed on an internal face of the dielectric cover facing the at least one antenna, the conductive pattern layer comprising a periodic arrangement of electrically conducting pattern elements.

Any embodiment may be combined with one or more other embodiments. These and other aspects of the present disclosure will be apparent from the example embodiment(s) described below.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to aid further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and, together with the description, help to explain the example embodiments. In the drawings:

FIG. 1 illustrates a radiation pattern of an antenna according to the prior art;

FIG. 2 illustrates a radiation pattern of an antenna array of two antennas according to the prior art;

FIG. 3A is a three-dimensional view of an antenna according to an example embodiment;

FIG. 3B is a cross-sectional view of the antenna of FIG. 3 A;

FIG. 4A is a three-dimensional view of an antenna according to an example embodiment;

FIG. 4B is a cross-sectional view of the antenna of FIG. 4A;

FIG. 5A is a three-dimensional view of an antenna according to an example embodiment;

FIG. 5B is a cross-sectional view of the antenna of FIG. 5 A;

FIG. 6A is a three-dimensional view of an antenna according to an example embodiment; FIG. 6B is a cross-sectional view of the antenna of FIG. 6A;

FIG. 7A illustrates an electric field of a patch antenna according to the prior art;

FIG. 7B illustrates an electric field of an antenna according to an example embodiment;

FIG. 8A illustrates a magnitude pattern of a patch antenna according to the prior art;

FIG. 8B illustrates a magnitude pattern of an antenna according to an example embodiment;

FIG. 9A illustrates a phase pattern of a patch antenna according to the prior art;

FIG. 9B illustrates a phase pattern of an antenna according to an example embodiment;

FIG. 10A and 10B are three-dimensional view of an antenna according to an example embodiment;

FIG. IOC is a cross-sectional view of the antenna of FIG. 10A;

FIG. 11A is a top plan view of an antenna arrangement according to an example embodiment;

FIG. 1 IB is a three-dimensional view of the antenna arrangement of FIG. 11 A;

FIG. 11C is a cross-sectional view of the antenna arrangement of FIG. 11 A;

FIG. 12A is a three-dimensional view of an antenna arrangement according to an example embodiment;

FIG. 12B is a three-dimensional view of antenna arrangement according to an example embodiment;

FIG. 12C is a three-dimensional view of antenna arrangement according to an example embodiment;

FIG. 13 A is a three-dimensional view of antenna arrangement according to an example embodiment;

FIG. 13B is a three-dimensional view of antenna arrangement according to an example embodiment;

FIG. 14 illustrates a magnitude pattern of an antenna arrangement according to an example embodiment;

FIG. 15A illustrates a phase pattern of an antenna arrangement according to the example embodiment of FIG. 13A;

FIG. 15B illustrates a magnitude pattern of an antenna arrangement according to an example embodiment of FIG. 13B;

FIG. 16A is a three-dimensional view of antenna device according to an example embodiment;

FIG. 16B is a cross-sectional view of the antenna device of FIG. 16A; FIG. 17A is a three-dimensional view of a radome according to an example embodiment;

FIG. 17B is a plan view of a pattern element of the radome of FIG. 17 A;

FIG. 18A is a three-dimensional view of a radome according to an example embodiment;

FIG. 18B is a plan view of a pattern element of the radome of FIG. 18A.

Like references are used to designate like parts in the accompanying drawings.

DETAILED DESCRIPTION

Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

A mmWave antenna may be implemented in an array where the main radiation beam direction is the broadside direction (e.g., the main radiation direction) is perpendicular to the plane of the antenna array. Alternatively, the main radiation beam direction can also be the endfire direction (e.g., the main radiation direction is parallel to the plane of the antenna array).

In sensing applications, antennas may be placed in an array topology. However, the beam may not be formed in the same manner as in the context of communication applications for transmission and reception of information. Rather the antenna elements may form a virtual array for sensing various parameters of the environment, including movement and directional information, etc. The sensing may be performed through data processing using the signal received from every antenna element of the total array. Multiple transmitting and receiving antenna elements can be used to form the so-called MIMO radar topology, which contributes to enhanced sensing resolution and accuracy, etc.

The beamforming and beam steering functionality of an antenna array may be mainly in the interest of communication applications. When it comes to sensing, it may be desired that all antenna elements which are forming a virtual MIMO array would have identical radiation patterns in terms of both magnitude and phase. The radiation pattern difference among all antenna elements should be minimized to achieve accurate estimation of the sensing system about the sensing environment. Such design may also be beneficial in the context of communication applications, where either higher gain of the beamforming or larger range of the beam steering can be attained when the radiation pattern difference among all antenna elements is well under control.

Example embodiments of the present disclosure make it possible to achieve the desired antenna radiation beam and to minimize the radiation pattern difference among antenna elements when placed in an array. Example embodiments may be applied for example in a mobile device, such as for example a UE (user equipment), smart home devices, access points, access nodes, or base stations, or CPE (customer premises equipment) devices for FWA (fixed wireless access).

The cause of the radiation pattern difference among antenna elements in an array can be quite complex. First, the antennas may be implemented using a printed circuit board (PCB). The dielectric substrate between conductive layers allows surface wave propagation around the mmWave frequency range. The surface wave may be mainly caused by electric field excited by the antenna which is perpendicular to the PCB surface and the waves propagate along the surface of the PCB. If the energy propagates within the PCB substrate, it may reduce the efficiency and the gain of the radiation and lead to distortion to the radiation patterns. The severity of the radiation pattern distortion may depend on the size of the PCB and the dielectric substrate used in the PCB. Second, when antennas are placed in an array with limited spacing between one another, e.g., half a wavelength, the antenna radiation may introduce mutual coupling among the antennas. Various techniques are known to increase port isolation to some extent. However, if the desired requirement for minimizing the radiation pattern difference is high, even conventionally accepted port isolation of 15~20dB may not be sufficient. Further, in practical implementations, antennas may be covered by a device cover, sometimes called as the antenna radome. The conventional target of the radome design for maximizing the radiation through the radome may be again insufficient when the target is also to minimize the radiation pattern difference among antennas in the array.

Patch antennas may be used in mmW frequency range for both communication and sensing applications. As shown in Fig. 1, when implemented in PCB, the radiation pattern of the patch antenna can have severe distortion. The issue can be improved by simply having a cavity surrounding the patch antenna, e.g., where the cavity can be implemented by grounded conductive layers using fence of VIAs. However, as can be seen from Fig. 1, the radiation pattern can be improved only to some extent. The pattern is not totally smooth, and it is having ripples of up to 2dB difference. Furthermore, as shown in Fig. 2, when two or more patch antennas are placed in an array, due to their mutual effects, the radiation patterns can be distorted so that it exhibits large degree of radiation pattern difference. Decoupling techniques are known to be effective to improve the port-to-port isolation, but it is not always the case that the radiation pattern difference would be also reduced. Nonetheless, the decoupling effects can only be achieved over a quite narrow frequency bandwidth.

Example embodiments of the present disclosure minimize the difference among radiation patterns of antenna elements placed in an array. Example embodiments may compensate for pattern distortion caused by various effects, such as surface wave propagation, antenna mutual effects, as well as radome effects, etc.

FIG. 3 A is a three-dimensional view of an example antenna. FIG. 3B is a cross-sectional view of the example antenna of FIG. 3 A.

The antenna 300 comprises an electrically conducting ground plane 301, and one or more electrically conducting board layers 302. The one or more electrically conducting board layers 302 may comprise a surface layer 302-1. The one or more board layers 302 are mounted parallel to the ground plane 301. In the following, when a layer is “below” or “above” another layer, it should be understood that this is with reference to a direction from the ground plane to the board layer(s).

The antenna 300 may comprise a dielectric substrate 303. The ground plane 301 may be disposed on a first surface of the dielectric substrate and the board layer 302 on the second face of the dielectric substrate 303. The dielectric substrates 303 is made of dielectric material. The dielectric substrate 303 may comprise one or more dielectric substrate layers.

The board layers 302 are electrically connected to the ground plane 301. In particular, the board layers 302 may be electrically connected to the ground plane 301 by a plurality of electrically conducting vias extending through the dielectric substrate and the board layers 302.

A cavity 305 is formed through the dielectric substrate 303 and the one or more board layers 302 including the surface layer 302-1. The cavity 305 may be defined by a bottom wall formed by the ground plane 301, and four electrically conducting side walls (e.g., vertical walls).

The antenna 300 comprises a radiating element 310. The radiating element 310 extend over or inside the cavity 305. The radiating element 310 may be a patch antenna. The radiating element 310 comprises at least one electrically conducting radiating layer 311. The radiating element 310 may comprise a single electrically conducting radiating layer 311 or a at least two electrically conducting radiating layer 311-1, 311-2 stacked on top of each other. The radiating layer 311 may have any appropriate shape, such as a polygon shape, for example a rectangular shape. The radiating layer 311 and the board layer 302 are disposed such as forming a pair of slots 306-1, 306-2 which extend over the cavity 305. The pair of slots 306-1, 306-2 improves the uniformity of the tangential electric field distribution of the excited antenna. This contributes to suppressing the surface wave excitation. The cavity 305 surrounding the radiating element 310 further suppresses the surface wave propagation.

One or more of the radiating layers 311 may comprise open slots and/or extended stubs. Open slots and/or extended stubs can help tune the resonance of the antennas while miniaturizing its size.

The antenna 300 may further comprise a differential feed. The differential feed may comprise two feeding points or postings 320-1, 320-2 configured to apply the differential feed to the radiating element 310. The alignment of the two feeding points 320-1, 320-2 define a central axis A of the antenna. The central axis A of the antenna may correspond to a main direction of the electric field E of the antenna. Each feeding posting 320-1, 320-2 may be an electrically conducting stud or via hole extending towards the ground plane 301. The differential feed may comprise a feeding line and a power divider configured to divide the feeding line into two feeding connections having a 180-deg phase shift/delay, each feeding connection being connected to one of the feeding postings 320-1, 320-2. The feeding may be galvanic or coupled.

The H-plane of the antenna is a plane containing the magnetic field vector H and the direction of maximum radiation. The E-plane of the antenna is a plane containing the electric field vector E and the direction of maximum radiation.

In example embodiments, two opposite edges of one of the radiating layers 311 are electrically connected to one of the board layers 302, for example the surface layer 302-1. The two opposite edges of the radiating layer 311 extend on either side of the central axis A of the antenna defined by the alignment of the feeding points 320-1, 320-2. The two opposite edges of the radiating layer 311 form the edges of the H-plane. As such, the radiating layer 311 is grounded at the edges of the H-plane. Together with differential feeding, this transforms the radiating element into a pair-of-slot antenna aperture.

More specifically, the radiating layer 311 and the board layer 302 form the pair of slots 306-1, 306-2 which extend over the cavity 305. The two slots 306-1, 306-2 may have the same shape. In particular, the two slots 306-1, 306-2 may be rectangular. A length of the slots 306-1, 306-2 may extend in a main direction of the magnetic field Hof the antenna. FIG. 4A is a three-dimensional view of an example antenna. FIG. 4B is a cross-sectional view of the example antenna of FIG. 4 A.

As illustrated by FIG. 4A and 4B, in example embodiments, the radiating layer 311 extends in the plane of the surface layer 302-1. The two opposite edges of the radiating layer 311 (e.g., edges of the H-plane) are contiguous with the surface layer 302-1. When the radiating layer 311 is in the plane of the surface layer 302-1, an aperture of the pair of slots 306-1, 306- 2 is parallel to the surface layer 302-1.

FIG. 5 A is a three-dimensional view of an example antenna. FIG. 5B is a cross-sectional view of the example antenna of FIG. 5 A.

As illustrated by FIG. 5 A and 5B, in example embodiments, a first radiating layer 311- 1 extends above the plane of the surface layer 302-1. The first radiating layer 311-1 is electronically connected to the surface board layer 302-1. In particular, the first radiating layer 311-1 may be electrically connected to the surface board layer 302-1 via an electrically conducting ridge 501. A second radiating layer 311-2 may extend below the plane of the surface layer 302-1. The second radiating layer 311-2 is connected to the differential feed 320-1, 320- 2.

FIG. 6A is a three-dimensional view of an example antenna. FIG. 6B is a cross-sectional view of the example antenna of FIG. 6 A.

As illustrated by FIG. 6A and 6B, in example embodiments, a first radiating layer 311-

1 electrically connected to the surface board layer 302-1 extends below the plane of the surface layer 302-1. The first radiating layer 311-1 is electronically connected to the surface board layer 302-1. In particular, the first radiating layer 311-1 may be electrically connected to the surface board layer 302-1 via an electrically conducting wall of the cavity 305. A second radiating layer 311-2 may extend below the plane of the surface layer 302-1. The second radiating layer 311-

2 is connected to the differential feed 320-1, 320-2.

When the radiating layer 310 extends below or above the plane of the surface layer 302- 1, the aperture of the pair of slots 306-1, 306-2 is not parallel to the surface layer 302-1. This ensures that the electric field of the antenna when excited is more tangential to the surface layer 302-1, e.g., parallel to the surface layer 302-1. As such, the surface wave excitation is efficiently suppressed.

As shown in Fig. 7A and 7B, the electric field excited by an antenna according to an example embodiment exhibits a more tangential distribution compared to a conventional patch antenna. As a result, as shown in Fig. 8A and 8B and Fig. 9A and 9B, pattern distortion in both magnitude and phase is considerably reduced with an antenna according to an example embodiment thanks to its more tangential electric field distribution.

FIG. 10A and 10B are three-dimensional views of an example antenna. FIG. IOC is a cross-sectional view of the example antenna of FIG. 10A and 10B.

As illustrated by FIG 10A to IOC, the antenna may be implemented on a multilayer PCB. The multilayer PCB comprises the ground plane 301, a plurality of board layers 302-1, ..., 302-n, and a plurality of dielectric substrate layers (not shown on FIG 10A to 10C). The board layers 302-1, . . ., 302-n are electrically connected to the ground plane 301 by a plurality of electrically conducting vias (e.g., via holes) 1001 extending through the dielectric substrate and the board layers 302-1, . . ., 302-n.

The cavity 305 is formed through the dielectric substrate layers and the board layers 302-1, . . ., 302-n. The side walls may be formed by a via fence. A via fence may be a row of vias (e.g., via holes). In particular, the vias may go through the board layers 302-1, ..., 302-n and the dielectric substrate layers and connect the board layers to the ground plane 301. The board layers 302-1, ..., 302-n and dielectric substrate layers form the side walls together with the via fence.

The two opposite edges of the radiating element 310 may be contiguous with one of the board layers 302-1, . . . , 302-n. In particular, the two opposite edges of the radiating element 310 may be contiguous with one of the board layers 302-2, . . ., 302-n that is not the surface layer 302-1.

FIG. 11 A is a top plan view of an example antenna arrangement. FIG. 1 IB is a three- dimensional view of the example antenna arrangement of FIG. 11 A. FIG. 11C is a cross- sectional view of the example antenna arrangement of FIG. 11 A.

The antenna arrangement 1100 comprises at least one antenna 1110-1, 1110-2 and a first electromagnetic band gap (EBG) structure 1120. The antenna arrangement 1100 may be an antenna array. The antennas 1110-1, 1110-2 may be arranged in rows and/or columns. The antennas 1110-1, 1110-2 may be according to any of the embodiments described in relations to FIG. 3 to FIG. 10. The antennas may also be any other suitable antennas such as patch antennas.

The antenna arrangement may further comprise a ground plane, a dielectric substrate, and one or more electrically conducting layers extending parallel to the ground plane.

The EBG structure 1120 comprises one or more EBG arrangements 1120-1, 1120-2. An EBG arrangement 1120-1, 1120-2 may be a periodic planar arrangement of electrically conducting EBG elements 1121 (also called patches or mushrooms) mounted parallel to the ground plane. The EBG arrangement 1120-1, 1120-2 may be an EBG array. The EBG elements may be arranged in rows and/or columns.

The surface wave suppression is mainly along the E-plane of the antenna. As such, a square shaped EBG element can introduce a coupling path to the antennas when placed in the array along the H-plane. In practical applications, both E-plane and H-plane array topologies may be needed and sometimes used as combined together. For such antennas, the EBG structures needs to effectively suppress surface wave suppression along the E-plane of the antenna, while limiting undesired properties along the H-plane of the antenna.

The EBG structure 1120 may be a polarization selective. To that end, the EBG elements 1121 may have a rectangular shape (e.g., instead of a square shape). In particular, a dimension of the rectangular element 1121 along a magnetic field vector H of the antenna may be larger than a dimension of the rectangular element along an electric field vector E of the antenna. In other words, a length L of the rectangular element 1121 is aligned with the magnetic field vector H of the antenna, while a width w of the rectangular element 1121 is aligned with the electric field vector E of the antenna. With such EBG elements 1121, the surface wave is suppressed along the E-plane of the antenna without harming the performance of the antenna array along the H-plane.

Each electrically conducting rectangular element 1121 may be electrically connected to the ground plane 1101, e.g., by an electrically conducting via 1122. The via 1122 may extend through the dielectric substrate, and the electrically conducting layers.

The EBG structure 1120 may not extend over all the PCB. The EBG structure 1120 suppresses the surface wave propagation which is caused by the vertical electric field vector of the antenna. Therefore, it is sufficient that the EBG structure 1120 extends along the E-plane of the antenna. The EBG structure 1120 are disposed along the electric field vector of the antenna to suppress the surface wave propagation. The antenna array can be formed along either the E- plane of the antenna as shown on FIG. 12 A, or along the H-plane of the antenna as shown on FIG. 12B.

A dimension d _BBG of the EBG arrangement along a magnetic field vector H of the antenna may be larger than a dimension d^ _ntenna of the antenna along the magnetic field vector H of the antenna.

The EBG structure 1120 may comprise a plurality of EBG arrangements 1120-1, 1120- 2. The antenna 1110 may be surrounded by EBG arrangements 1120-1, 1120-2. In particular, EBG arrangements 1120-1, 1120-2 may be disposed on either side of the antenna along an electric field vector of the antenna.

As illustrated by FIG. 12C, the antenna arrangement 1110 may comprises a plurality of antennas 1110-1, 1110-2, e.g., forming an array along the E-plane. The EBG structure 1120 may comprises a plurality of EBG arrangements 1120-1, 1120-2, 1120-3 interleaved with the antennas 1110-1, 1110-2, e.g., along the electric field vector of the antenna. The EBG arrangements 1120-1, 1120-2 may enclose the antennas 1110-1, 1110-2. Such an EBG structure 120 can further improve the isolation among the array antennas.

FIG. 13 is a top plan view of an example antenna arrangement.

The antenna arrangement 1100 comprises at least one antenna 1110-1, 1110-2 and a second electromagnetic band gap (EBG) structure 1320. The antenna arrangement 1100 may be an antenna array. The antennas 1110-1, 1110-2 may be arranged in rows and/or columns. The antennas 1110-1, 1110-2 may be according to any of the embodiments described in relations to FIG. 3 to FIG. 10. The antennas may also be any other suitable antennas such as patch antennas.

The antenna arrangement may further comprise a ground plane, a dielectric substrate, and one or more electrically conducting layers extending parallel to the ground plane.

A cause of the radiation pattern distortion and difference among array antennas is the mutual effects of the antenna elements in the array. The second EBG structure 1320 improves the isolation between the neighbouring antennas, and hence reduce the radiation pattern difference caused by the mutual effects between the neighbouring antennas.

The second EBG structure 1320 comprises one or more second EBG arrangements 1320. A second EBG arrangement 1320 extends between two antennas 1110-1, 1110-2. The second EBG arrangement 1320 comprises a planar arrangement of two electrically conducting stripes 1321-1, 1321-2 mounted parallel to the ground plane and parallel to each other.

A length of the two electrically conducting stripes 1321-1, 1321-2 may be perpendicular to the alignment of the antennas 1110-1, 1110-2. The antennas 1110-1, 1110-2 may be aligned along the magnetic field vector H of the antenna. A length of the two electrically conducting stripes 1321-1, 1321-2 may be aligned along an electric field vector E of the antenna.

As is illustrated by FIG. 14, the mutual coupling of the antennas (e.g., antenna ports Sl,2) of the arrangement of FIG. 13 A is greatly reduced. As is illustrated by FIG. 15 A, the radiation patterns of the different antennas (e.g., phase) of the arrangement of FIG. 13A are smooth with negligible ripples and are similar with one another. As illustrated by FIG. 13B, a plurality of second EBG arrangements 1320-1, 1320-2, 1320-2 may be interleaved with a plurality of antennas 1110-1, 1110-2. The second EBG arrangements 1320-1, 1320-2, 1320-2 may enclose the antennas. This further reduces the radiation pattern difference.

As is illustrated by FIG. 15B, the uniformity of the radiation patterns of the different antennas (e.g., phase) of the antenna arrangement of FIG. 13B is further improved.

The example embodiments of FIG. 13 A or FIG. 13B may be combined with any of the example embodiments disclosed with reference to and/or in conjunction with FIG. 11 to 12.

In particular, the antenna arrangement may comprise a first EBG structure 1120 and a second EBG structure 1320. EBG arrangements 1120-1, 1120-2 of the first EBG structure 1120 may be disposed on either side of the antennas 1110-1, 1110-2 in the direction of the electric field vector to suppress the surface wave propagation. EBG arrangements 1320-1, 1320-2, 1320-3 of the second EBG structure 1320 may be interleaved with the antennas 1110-1, 1110- 2 along the H-plane of the antennas to suppress the mutual effects between the antennas.

FIG. 16A is a three-dimensional view of the example antenna device. FIG. 16B is a cross-sectional view of the example antenna device of FIG. 16 A.

The antenna device comprises at least one antenna or antenna arrangement 1610. The antenna 1610 may be implemented on a PCB 1611. The antenna or antenna arrangement 1610 may be according to any of the embodiments described herein, in particular any example embodiments described in relations to FIG. 3 to FIG. 15. The antenna 1610 may also be any other suitable antenna such as a patch antenna.

The antenna device 1600 further comprises a device cover also called radome 1620.

In order to maximize the gain of the radiation through the radome 1620, the thickness of the radome may be about 1/2-wavelength in the dielectric material. The distance between the antenna 1610 and the radome 1620 may be about 1/2-wavelength in the free space.

The radome 1620 comprises a dielectric cover, such as a plastic cover. The radome 1620 can be also realized by a sandwich structure with multiple layers of either very thin dielectric layers or thicker layers with very low dielectric constant.

The radome 1620 comprises a conductive pattern layer 1621 disposed on an internal face of the dielectric cover facing the antenna 1610. The conductive pattern layer 1621 comprising a periodic arrangement of electrically conducting pattern elements. Such a conductive pattern layer 1621 may be called meta-surface or meta-material.

As illustrated by FIG. 17A and 17B, the pattern element can be a line cross. As illustrated by FIG. 18A and 18B, the pattern element can be a Jerusalem cross. The conductive pattern layer 1621 provides the radome 1602 with electromagnetic properties. In particular, such radome 1602 further reduces the radiation pattern distortion and difference among antenna elements in the array.

The conductive pattern layer 1621 comprises a periodic arrangement of conductive patterns. The conductive pattern layer 1621 may be either a separate flexible printed circuit board (FPCB) attached to the dielectric cover or deposited directly on the dielectric cover, e.g., by printing. Multiple layers of the pattern layers and the cover dielectric can be stacked in order to achieve certain rigidity and robustness of the device cover.

A conventional dielectric 1/2-wave-radome provides poor wave-matching for tangential electric field at very large incident angle, and a matching for normal electric field that is too strong for the surface wave suppression.

The periodic structure of the conductive pattern layer 1621 provides wave-matching at the desired frequency for the tangential electric field (e.g., radiation through) at both normal direction and very large angle and provides mismatch/reflection for the perpendicular electric field (e.g., surface wave) at large angle.

The periodic structure of the conductive pattern layer 1621 can further improve isolation and reduce the mutual effects among the antennas. The periodic structure of the conductive pattern layer 1621 together with a proper radome-distance can control the antenna coupling, thereby achieving a trade-off in design for better radiation pattern with minimized radiation pattern difference.

Any range or device value given herein may be extended or altered without losing the effect sought. Also, any embodiment may be combined with another embodiment unless explicitly disallowed.

Although the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items. The steps or operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the example embodiments described above may be combined with aspects of any of the other example embodiments described to form further example embodiments without losing the effect sought.

The term 'comprising' is used herein to mean including the method, blocks, or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements. Although subjects may be referred to as ‘first’ or ‘second’ subjects, this does not necessarily indicate any order or importance of the subjects. Instead, such attributes may be used solely for the purpose of making a difference between subjects.

It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from scope of this specification.