Patent Description:
Future mobile electronic devices need to support millimeter-wave bands, e.g. <NUM> and <NUM>, as well as sub-<NUM> bands in order to accommodate increased data rates. However, the volume reserved for all the antennas in a mobile electronic device is very limited and the added millimeter-wave antennas should ideally be accommodated to the same volume as the sub-<NUM> antennas. Increasing the volume reserved for antennas would make the electronic device larger, bulkier, and less attractive to users. Current millimeter-wave antennas either require such additional volume, or if placed in the same volume, significantly reduce the efficiency of sub-<NUM> antennas.

Furthermore, the movement towards very large displays, covering as much as possible of the electronic device, makes the space available for the antenna array very limited, forcing either the size of the antenna array to be significantly reduced, and its performance impaired, or a large part of the display to be inactive.

Additionally, mobile electronic devices, such as mobile phones and tablets, may be oriented in any arbitrary direction. Therefore, such electronic devices need to exhibit an as near full spherical beam coverage as possible. Such coverage is difficult to achieve, i. due to the radiation beam being blocked by a conductive housing, a large display, and/or by the hand of the user holding the device.

<CIT> discloses a slot fed volumetric antenna structure that activates antenna beams in three axes by selective connection of feedpoints.

<CIT> discloses a dual polarized array antenna comprising at least two dual polarized antenna elements being arranged for radiating electromagnetic energy having a first polarization, constituting a first antenna radiation pattern, via a connection to a first antenna port, and electromagnetic energy having a second polarization, constituting a second antenna radiation pattern, via a connection to a second antenna port, the second polarization being orthogonal to the first polarization, the first antenna radiation pattern and second antenna radiation pattern each having a main beam and a number of side-lobes with nulls. The array antenna comprises at least one further dual polarized antenna element arranged for radiating electromagnetic energy having two mutually orthogonal polarizations, constituting further antenna radiation patterns, via respective connections to the first antenna port and the second antenna port, where the polarization of said at least one further dual polarized antenna element that is associated with the first antenna port deviates from the first polarization such that said at least one null of the first antenna pattern is at least partly filled.

It is an object to provide an improved dual-polarization antenna array. The foregoing and other objects are achieved by the features of the independent claim. Further implementation forms are apparent from the dependent claims, the description, and the figures.

According to a first aspect, there is provided a dual-polarization antenna array comprising a conductive structure having an aperture pattern comprising at least two first apertures each having a first configuration and at least two second apertures having a second configuration, wherein each pair of two first apertures is directly interconnected by one second aperture, said first apertures and said second apertures being arranged in periodic sequence such that each first aperture is separated from an adjacent first aperture by a second aperture, and each second aperture is directly interconnected with two adjacent first apertures at least one first coupling element being connected to a first antenna feed line,.

Such a solution, comprising a periodic sequence of differently shaped apertures, facilitates a dual-polarized antenna array arranged within the same space of a conductive structure, which, in turn, reduces the volume needed for providing an efficient antenna array having omnicoverage, or near omnicoverage. Since both polarizations use parts of the same conductive structure, the total length of the dual-polarization antenna array can be reduced. Furthermore, such a solution is relatively easy to manufacture as well as aesthetically appealing, since it can be designed to resemble current microphone and speaker grill slots. The volumes of each first aperture and each second aperture are effectively increased by their corresponding direct interconnection, thus effectively increasing the efficiency and bandwidth of antenna elements having the first polarization and antenna elements having the second polarization.

In one embodiment of the dual-polarization antenna array, the first coupling element and the second coupling element are configured to perform polarization MIMO and/or diversity wireless communication.

In a possible implementation form of the first aspect, the first aperture has a larger area than the second aperture, the first coupling element being configured to excite an electrical field having horizontal polarization, the second coupling element being configured to excite an electrical field having vertical polarization, which allows electrical fields of dual polarization to radiate through an as small total aperture window as possible, making the conductive structure mechanically robust. At that, isolation between the first coupling element and the second coupling element is improved by the orthogonally configured electrical fields of horizontal and vertical polarization. Thus, the efficiency of the dual-polarized antenna array is further improved. This embodiment further enables beamforming and beamshaping of the horizontal polarization electromagnetic radiation independently and uncorrelated from beamforming of the vertical polarization radiation.

In a further possible implementation form of the first aspect, a first end of the second coupling element is connected to the second antenna feed line at one side of the second aperture, a second end of the second coupling element being coupled to the conductive structure at an opposite side of the second aperture, allowing vertical polarization to be excited by creating a voltage across the second aperture. Thus, the second coupling element enables wide-band high efficiency antenna operation by suppressing parasitic electromagnetic modes and by providing impedance control.

In a further possible implementation form of the first aspect, the second end of the second coupling element is at least one of galvanically, inductively, and capacitively coupled to the conductive structure, allowing a choice between more secure coupling and more simplified manufacture of the conductive structure.

In a further possible implementation form of the first aspect, a first end of the first coupling element is connected to the first antenna feed line at one side of the second aperture, and a second end of the first coupling element is at least partially juxtaposed with the first aperture, the first aperture being adjacent the second aperture, further facilitating a robust conductive structure having as little aperture area as possible. This structure enables wide-band high efficiency antenna operation by suppressing parasitic electromagnetic modes and providing impedance control.

In a further possible implementation form of the first aspect, the second end of the first coupling element is offset from the first end of the first coupling element in a direction towards an adjacent, further second aperture, allowing horizontal polarization to be excited by a first probe juxtaposed with a wider aperture. This topology supports dual-resonant or multi-resonant frequency response, further improving bandwidth and efficiency of the antenna operation.

In a further possible implementation form of the first aspect, the first coupling element and the second coupling element are connected to one of a balanced antenna feed line and an unbalanced antenna feed line, allowing the coupling element to be disconnected from or connected to a conductive structure. The coupling element being disconnected from the conductive structure enables a low-cost, mechanically stable assembly process, while the coupling element being connected to the conductive structure enables a reduction of the antenna thickness and efficiency improvement.

According to the first aspect, the dual-polarization antenna array comprises at least two first apertures and at least two second apertures, the first apertures and the second apertures being arranged in periodic sequence such that each first aperture is separated from an adjacent first aperture by a second aperture, and each second aperture is directly interconnected with two adjacent first apertures, allowing the two polarizations to be formed across the same section of conductive structure. This configuration enables dual-polarization beamforming. Each dual-polarization antenna element is isolated from adjacent dual-polarization antenna elements by the conductive structure, thus further improving efficiency and beam-forming performance.

In a further possible implementation form of the first aspect, the first coupling elements and the second coupling elements are arranged such that every other second aperture is at least partially juxtaposed with a second coupling element and every other second aperture is at least partially juxtaposed with a first coupling element, and each first coupling element additionally being at least partially juxtaposed with one first aperture adjacent the second aperture, the first coupling element and the second coupling element being arranged offset from each other which allows use of unbalanced feeds. By interleaving the first coupling elements and the second coupling elements further reduction of the antenna thickness is enabled by utilization of microstrip or coplanar feed lines. Isolation between adjacent coupling elements is further improved by their spatial separation.

In a further possible implementation form of the first aspect, one first coupling element and one second coupling element are at least partially juxtaposed with one second aperture, the overlap of the first coupling element and the second coupling element facilitating a more compact solution. By collocating the first coupling element and the second coupling element, the length of the dual-polarization antenna array is reduced. Isolation between collocated coupling elements is configured by the orthogonal modes of the electromagnetic fields generated by the coupling elements.

In a further possible implementation form of the first aspect, the aperture pattern comprises at least one H-pattern, each H-pattern comprising two first apertures and one second aperture, the second aperture directly interconnecting the first apertures, facilitating a more robust conductive structure due to the possibility of having continuous sections of the conductive structure extending between each H-pattern. The dual-polarization antenna element configured by each H-pattern aperture enables dual-polarization beamforming. Each dual-polarization antenna element is isolated from adjacent dual-polarization antenna elements by the conductive structure, thus further improving efficiency and beam-forming performance.

According to a second aspect, there is provided an electronic device comprising a display, a device chassis, and a dual-polarization antenna array according to the above, the conductive structure of the dual-polarization antenna array comprising a metal frame, the device chassis being at least partially enclosed by the display and the metal frame, first coupling elements and second coupling elements of the dual-polarization antenna array being coupled to the metal frame. Such a solution facilitates a dual-polarized antenna array from which the electromagnetic fields radiate from edges of the electronic device, improving the beamforming and beamsteering coverage of the antenna array. The communication performance of the electronic device is further improved by beamforming directed along edges the electronic device, as those edges remain exposed to free-space in typical user scenarios.

In a possible implementation form of the second aspect, the conductive structure further comprises a printed circuit board, the printed circuit board extending at least partially in parallel with the metal frame, between the metal frame and the device chassis, the device chassis being at least partially enclosed by the display and the metal frame, the first coupling elements and the second coupling elements of the dual-polarization antenna array being arranged on the printed circuit board. The aperture pattern provided in the metal frame and in the printed circuit board (PCB) not only allows dual polarization, but also facilitates an as small total aperture window as possible which makes metal frame mechanically robust. Since both polarizations use parts of the same conductive structure, the total length of the dual-polarization antenna array can be reduced. Furthermore, coexistence with sub <NUM>-GHz antennas is enabled since the aperture pattern does not degrade low band antenna performance.

In a possible implementation form of the second aspect, the electronic device further comprises a reflecting structure extending in parallel with the at least one first aperture and the at least one second aperture of the conductive structure, increasing the coupling to the metal frame. Further, the beam shaping of the dual-polarization antenna array is improved by directing the electromagnetic radiation from the edges of the electronic device.

In a further possible implementation form of the second aspect, the dual-polarization antenna array is configured to generate millimeter-wave frequencies, facilitating the introduction of millimeter-wave antennas without affecting the visual appearance, robustness, or manufacturability of the electronic device. Millimeter-wave antennas enable wireless communication in <NUM> and beyond <NUM> electronic devices.

In a further possible implementation form of the second aspect, the dual-polarization antenna array comprises at least one end-fire antenna element, facilitating an end-fire array pattern essential to achieve omnicoverage. The communication performance of the electronic device is further improved by beamforming directed along edges the electronic device, as those edges remain exposed to free-space in typical user scenarios.

In a further possible implementation form of the second aspect, the electronic device comprises at least one further antenna array, the further antenna array being configured by the device chassis and the metal frame with feed lines extending partially adjacent the dual-polarization antenna array and partially across a gap between the device chassis and the metal frame, the further antenna array generating non-millimeter-wave frequencies, allowing two types of antennas to be arranged in the same space without the performance of either antenna being significantly degraded. Coexistence of a millimeter-wave dual-polarization antenna array and a further antenna array within the same volume of the gap between the device chassis and the metal frame further reduces the total antenna volume necessary within the electronic device and enables a further increase of the display surface. Coexistence of the dual-polarization antenna array with the further antenna array is enabled since the aperture pattern of the metal frame does not degrade the further antenna array performance.

<FIG> show an embodiment of an electronic device <NUM>, such as a mobile phone or a tablet, comprising a display <NUM>, a device chassis <NUM>, and a dual-polarization antenna array <NUM> which includes a conductive structure <NUM>, comprising a metal frame <NUM> and a PCB <NUM>, having an aperture pattern.

The aperture pattern, shown schematically in <FIG>, comprises at least one first aperture <NUM> (in embodiments of the present invention at least two apertures <NUM>) having a first configuration and at least one second aperture <NUM> (in embodiments of the present invention at least two apertures <NUM>) having a second configuration. Each first aperture <NUM> is directly interconnected with at least one second aperture <NUM>. The aperture pattern may comprise of essentially rectangular shapes, as shown in <FIG>, of essentially elliptical shapes, having rounded corners as shown in <FIG>, a combination of both, or any other suitable shape.

<FIG> shows a dual-polarization antenna array <NUM> comprising a larger number of first apertures <NUM>, each pair of two first apertures <NUM> being interconnected by one second aperture <NUM> such that a chain-like structure is formed.

In one embodiment, the dual-polarization antenna array <NUM> comprises at least two first apertures <NUM> and at least one second aperture <NUM>, the first apertures <NUM> and the second aperture <NUM> being arranged in periodic sequence such that each first aperture <NUM> is separated from an adjacent first aperture <NUM> by a second aperture <NUM>, and each second aperture <NUM> is directly interconnected with two adjacent first apertures <NUM>. <FIG> shows a dual-polarization antenna array <NUM> comprising two first apertures <NUM> and one second aperture <NUM> directly interconnecting the two first apertures <NUM>, i.e. the aperture pattern of <FIG> comprises two H-patterns. The dual-polarization antenna array <NUM> comprises several subsequent H-patterns as shown in <FIG>.

The dual-polarization antenna array <NUM> further comprises at least one first coupling element, i.e. conductor, <NUM> which is connected to a first antenna feed line <NUM>, and at least one second coupling element, i.e. conductor, <NUM> which is connected to a second antenna feed line <NUM>, as shown in <FIG> and <FIG>.

In one embodiment, shown in <FIG>, the first coupling elements <NUM> and the second coupling elements <NUM> are arranged such that every other second aperture <NUM> is at least partially juxtaposed with a second coupling element <NUM> and every other second aperture <NUM> is at least partially juxtaposed with a first coupling element <NUM>. Each first coupling element <NUM> is additionally at least partially juxtaposed with one first aperture <NUM> adjacent the second aperture <NUM>.

The first coupling element <NUM> is configured to excite an electrical field having a first polarization, and the second coupling element <NUM> is configured to excite an electrical field having a second polarization. Each first coupling element <NUM> is at least partially juxtaposed with one first aperture <NUM>, which allows the electrical field having a first polarization to be transmitted and/or received through the first aperture <NUM>. Correspondingly, each second coupling element <NUM> is at least partially juxtaposed with one second aperture <NUM>, which allows the electrical field having a second polarization to be transmitted and/or received through the second aperture <NUM>.

In one embodiment, the first aperture <NUM> has a larger area than the second aperture <NUM>, and the first coupling element <NUM> is configured to excite an electrical field having horizontal polarization, while the second coupling element <NUM> is configured to excite an electrical field having vertical polarization, as shown in <FIG>.

The first end 7a of the second coupling element <NUM> may be connected to the second antenna feed line <NUM> at one side of the second aperture <NUM>, while the second end 7b of the second coupling element <NUM> is coupled to the conductive structure <NUM> at an opposite side of the second aperture <NUM>, as shown clearly in <FIG>. The second end 7b of the second coupling element <NUM> is at least one of galvanically, inductively, and capacitively coupled to the conductive structure <NUM>.

Correspondingly, the first end 5a of the first coupling element <NUM> may be connected to the first antenna feed line <NUM> at one side of the second aperture <NUM>, while the second end 5b of the first coupling element <NUM> is at least partially juxtaposed with one of the first apertures <NUM>, which first aperture <NUM> is located adjacent the second aperture <NUM>. The second end 5b of the first coupling element <NUM> is offset from the first end 5a of the first coupling element <NUM> in a direction towards a further, adjacent second aperture <NUM>, as shown in <FIG>.

<FIG> shows a first coupling element <NUM> where the second end 5b extends only in one direction.

An unbalanced feed line 6a, 8a is connected to different types of conductors, i.e. coupling elements <NUM>, <NUM>, for differently polarized currents. For instance, the return current may flow through a common ground or other conductive parts. An unbalanced feed line 6a, 8a inherently couples to the common ground, which typically results into a significant mutual coupling between closely-located unbalanced feeds. To lower the mutual coupling between the feed lines 6a, 8a, they are typically physically offset, as shown in <FIG>). For instance, if λ/<NUM> element separation is desired in a dual-polarized array, the distance between differently polarized feed lines 6a, 8a can be λ/<NUM>. Hereinafter λ is the wavelength at center frequency of the dual-polarization antenna array <NUM>.

<FIG> shows preferable dimensions of the dual-polarization antenna array <NUM>. L1, λ/<NUM>~λ/<NUM>, defines the inter-element spacing which will affect the directivity of the array and define the maximum grating-lobe free steering range. L2, λ/<NUM>~λ/<NUM>, defines the lowest operational frequency for the horizontal polarization. L3, approximately λ/<NUM>, defines the probe length which defines the resonant frequency for the horizontal polarization. L4, λ/<NUM>~λ/<NUM>, defines the conductor length which defines the resonant frequency for the vertical polarization, i.e. the length of the second coupling element <NUM> which extends across the second aperture <NUM>. L5, λ/<NUM>~λ/<NUM>, defines the gap between two opposite "teeth" of the dual-polarization antenna array <NUM>, which is modified to, in turn, modify the resonant frequency.

In a further embodiment, shown in <FIG>, the first coupling elements <NUM> and the second coupling elements <NUM> are arranged such that both one first coupling element <NUM> and one second coupling element <NUM> are at least partially juxtaposed with one second aperture <NUM>, the first coupling element <NUM> and the second coupling element <NUM> being co-located.

The first coupling element <NUM> and the second coupling element <NUM> may also be connected to balanced feed lines 6b, 8b. As shown in <FIG>, the first coupling element <NUM> may comprise two conductors, i.e. two second ends 5b extending in two opposite directions, providing balanced excitation of two adjacent first apertures <NUM>. Geometrically, a balanced feed line 6b, 8b is symmetrical and therefore the conductors for positive and negative currents are identical, as is clear from <FIG>. Furthermore, both conductors couple equally to the conductive structure <NUM> and to other parts. Ideally, the differential mode of a balanced feed line does not couple to the conductive structure <NUM>, or other nearby metal objects at all. Therefore, two orthogonally-polarized balanced feed lines 6b, 8b can be co-located, both feed lines being mutually uncoupled as shown in <FIG>). This implementation improves the isolation and cross-polarization levels of each feed line. A balanced solution may rely on capacitive coupling from the second end 7b of the second coupling element <NUM> to the conductive structure <NUM>.

One of first coupling element <NUM> and the second coupling element <NUM> may be connected to a balanced feed line 6a, 8a while the other coupling element is connected to an unbalanced feed line 6a, 8a, regardless of the first coupling element <NUM> and the second coupling element <NUM> being co-located or not.

Regardless whether the feed line <NUM>, <NUM>, and hence the coupling element <NUM>, <NUM> is balanced or unbalanced, the coupling element <NUM>, <NUM> can couple to the conductive structure <NUM> galvanically, capacitively or inductively. In galvanic coupling, either both ends of a balanced feed line 6a, 8a, or signal and ground conductors in case of an unbalanced feed line 6b, 8b, are galvanically connected to the conductive structure <NUM>. This option is most feasible with an unbalanced vertically polarized feed line, but can be used in other cases too. An unbalanced vertically polarized feed line 8b could also be realized with a capacitive coupling. In this case the signal would be coupled to certain area of the conductive structure <NUM> through a large parallel-plate capacitor at the second end 7b, as well as the ground coupling pad. This would facilitate the fabrication process since no galvanic connection is needed.

In a further embodiment, the coupling could also be done by utilizing magnetic fields such that currents in the feed line <NUM>, <NUM> induce currents on the conductive structure <NUM>.

As mentioned above, and shown in <FIG>, the electronic device <NUM> comprises a display <NUM>, a device chassis <NUM>, and a dual-polarization antenna array <NUM>. The conductive structure <NUM> of the dual-polarization antenna array <NUM> comprises at least a metal frame <NUM>, and the device chassis <NUM> is at least partially enclosed by the display <NUM> and the metal frame <NUM>. The first coupling elements <NUM> and second coupling elements <NUM> of the dual-polarization antenna array <NUM> are coupled to the metal frame <NUM>.

The conductive structure <NUM> may furthermore comprise a PCB <NUM>. The first coupling elements <NUM> and second coupling elements <NUM> of the dual-polarization antenna array <NUM> are arranged on the PCB <NUM> which extends at least partially in parallel with the metal frame <NUM>, between the metal frame <NUM> and the device chassis <NUM>. The coupling elements <NUM>, <NUM>, when realized on the PCB <NUM>, are relatively easy and inexpensive to manufacture.

In one embodiment, the first coupling elements <NUM>, the second coupling elements <NUM>, and the conductive structure <NUM> are configured using at least one of molded interconnect device technology, laser direct structuring technology, flexible printed circuits, metal-spraying techniques and related technologies.

The aperture pattern in the metal frame <NUM> can be filled with dielectric material such as plastic for robustness and sealing purposes.

In one embodiment, the electronic device <NUM> comprises a reflecting structure <NUM> extending in parallel with the at least one first aperture <NUM> and the at least one second aperture <NUM> of the conductive structure <NUM>, as shown in <FIG> and <FIG>. The reflecting structure <NUM> may be an existing component of the electronic device <NUM>, such as the device chassis <NUM>, a battery, a shielding structure, or another conductive component. The reflecting structure <NUM> may be located at approximately λ/<NUM> from the aperture pattern at the conductive structure <NUM> in order to direct radiation outwards from the electronic device.

The dual-polarization antenna array <NUM> may be configured to generate millimeter-wave frequencies. Furthermore, the dual-polarization antenna array <NUM> may comprises at least one end-fire antenna element.

The electronic device <NUM> may also comprise at least one further antenna array <NUM> configured to generate non-millimeter-wave frequencies, e.g. a sub-<NUM> antenna being part of the metal frame <NUM>. The further antenna array <NUM> is configured by the device chassis <NUM> and the metal frame <NUM> with feed lines <NUM> extending partially adjacent the dual-polarization antenna array <NUM> and partially across a gap <NUM> formed between the device chassis <NUM> and the metal frame <NUM>.

The communication performance of the electronic device <NUM> is further improved by beamforming directed along the edges the electronic device in the directions indicated by the arrows in <FIG>. The edges of the metal frame <NUM> are exposed to free-space in typical user scenarios. Steering the dual-polarization beams in these directions enables omnicoverage.

The present disclosure allows the size of the apertures in the metal frame <NUM>, and the antenna thickness Lt, shown in <FIG> to be reduced, from as common in prior art λ/<NUM> (<NUM>-<NUM>) and λ/<NUM> (<NUM>) to λ/<NUM> (<NUM>), i.e. a reduction by about <NUM>% and <NUM>%, respectively. In one embodiment, the necessary aperture height is <NUM>. In a further embodiment, the antenna thickness, in the direction of the gap <NUM>, is Lt = <NUM>.

As mentioned above, the conductive structure <NUM> of the dual-polarization antenna array <NUM> may be configured by the metal frame <NUM> and the PCB <NUM>, as shown in <FIG>, where dielectric structures are hidden for the sake of clarity. The aperture patterns of the conductive structure <NUM> are configured as follows: the second apertures <NUM> are defined by metallization layers of the PCB <NUM>, and the first apertures <NUM> are defined by metallization layers of the PCB <NUM> and an aperture in the metal frame <NUM>. This solution enables the coexistence of sub-<NUM> antennas with <NUM> mm-wave antennas: both sub <NUM>-GHz antennas <NUM> and the millimeter-wave dual-polarization antenna array <NUM> share the same volume of the metal frame <NUM> and the same volume of the gap <NUM> between the metal frame <NUM> and the chassis <NUM>. The aperture pattern of the metal frame <NUM> does not degrade performance of the sub <NUM>-GHz antennas <NUM>.

The radiation of the electromagnetic field generated by the electronic device <NUM> is shown in <FIG>. Lines of equal electric potential are illustrated for the horizontal polarization radiation, which is generated by first coupling elements <NUM>. A reactive electric field is generated within the gap <NUM>, between the device chassis <NUM> and the metal frame <NUM>, illustrating efficient usage of the gap <NUM> volume for bandwidth and antenna efficiency improvement. At the same time, the dual-polarization array <NUM> does not require any conductive structures present within the gap <NUM>, thus enabling coexistence with the above-mentioned further antenna array <NUM> which generates non-millimeter-wave frequencies, as shown in <FIG>.

The various aspects and implementations has been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject-matter, from a study of the drawings, the disclosure, and the appended claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Claim 1:
A dual-polarization antenna array (<NUM>) comprising
a conductive structure (<NUM>) having an aperture pattern comprising at least two first apertures (<NUM>) each having a first configuration and at least two second apertures (<NUM>) having a second configuration, wherein each pair of two first apertures (<NUM>) is directly interconnected by one second aperture, said first apertures (<NUM>) and said second apertures (<NUM>) being arranged in periodic sequence such that each first aperture (<NUM>) is separated from an adjacent first aperture (<NUM>) by a second aperture (<NUM>), and each second aperture (<NUM>) is directly interconnected with two adjacent first apertures (<NUM>),
at least one first coupling element (<NUM>) being connected to a first antenna feed line (<NUM>),
at least one second coupling element (<NUM>) being connected to a second antenna feed line (<NUM>), said first coupling element (<NUM>) being configured to excite an electrical field having a first polarization,
said second coupling element (<NUM>) being configured to excite an electrical field having a second polarization,
each first coupling element (<NUM>) being at least partially juxtaposed with one first aperture (<NUM>), allowing said electrical field having a first polarization to be transmitted and/or received through said first aperture (<NUM>),each second coupling element (<NUM>) being at least partially juxtaposed with one second aperture (<NUM>), allowing said electrical field having a second polarization to be transmitted and/or received through said second aperture (<NUM>).