Patent Description:
An array of patch antennas can be used in beam-steering applications.

In multiple user MIMO (multiple input multiple output) applications, a narrow antenna beam, formed by a phased array of patch antennas at a transmitter/receiver can be steered towards a receiver/transmitter.

<CIT> discloses a power divider for transmitting signals of an input terminal to a plurality of output terminals including a rectangular microstrip line coupled to the input terminal, and a plurality of coupling units conducting the rectangular microstrip line and the plurality of output terminals by electromagnetic coupling.

<CIT> discloses a parallel line formed on the same plane as a patch element, close to the patch element, in a direction that is a magnetic field direction of a patch antenna and parallel to the polarization direction of the patch antenna.

<CIT> discloses an electronic device including a housing including a first plate, a second plate facing a direction opposite to the first plate, and a lateral member surrounding a space between the first and second plates and connected to or integrally formed with the second plate.

<CIT> discloses a dual-polarization broadband array antenna which comprises a baffle board, radiating elements, isolating devices, metal parasitic pieces and supporting parts.

<CIT> discloses a plurality of fed elements arranged in a first direction provided within the plane of a substrate.

<CIT> discloses an antenna array for simultaneous reception or for simultaneous transmission of electromagnetic waves having two linear, orthogonal polarizations having a decoupling device between adjacent radiating element modules.

According to embodiments there is provided an apparatus comprising:.

In some but not necessarily all examples, the coupling elements increase cross-polarization discrimination for the array of antennas, at boresight, being a direction orthogonal to a flat plane of the array of antennas.

In some but not necessarily all examples, the coupling elements are elongate having a length greater than a width, and wherein the aligned arrangement of coupling elements in the respective columns are aligned lengthwise.

In some but not necessarily all examples, the aligned arrangement of coupling elements in a respective column are arranged along a virtual line that bi-sects the antennas of the respective column.

In some but not necessarily all examples, the coupling elements are flat conductive elements.

In some but not necessarily all examples, the apparatus comprises a printed wiring board, wherein the printed wiring board comprises the coupling elements and comprises the antennas.

In some but not necessarily all examples, a respective column of the aligned arrangement of coupling elements comprises coupling elements of the same size and shape between the antennas of the respective column.

In some but not necessarily all examples, the coupling elements do not vary their characteristics in a column direction.

In some but not necessarily all examples, the coupling elements vary their characteristics in a row direction.

According to embodiments, the coupling elements are closer to adjacent antennas in a column of the array, in a column direction, for a column towards a center of the array of antennas than for a column towards a periphery of the array of antennas.

According to embodiments, each of the antennas in the array of antennas comprises a radiator and feeds for a first polarization and a second polarization orthogonal to the first polarization.

In some but not necessarily all examples, the apparatus comprises means for controlling at least phase between feeds.

In some but not necessarily all examples, the apparatus comprises means for providing a relative phase adjustment to groups of antennas in the array of antennas, wherein the same relative phase adjustment is applied to antennas within a group and different relative phase adjustment is applied to antennas in different groups to effect beam-steering.

In some but not necessarily all examples, the apparatus comprises grounded isolation towers positioned at corners of antennas in the array of antennas. According to various, but not necessarily all, embodiments there is provided a base station system or portable electronic device configured for multiple-input multiple-output operation and comprising the apparatus.

The apparatus of <FIG> does not have all the features of the independent claim. Nevertheless, it is an example useful for the understanding of the present invention.

The following disclosure describes different examples of an apparatus <NUM> comprising:
a ground plane <NUM> and an array <NUM> of antennas <NUM>.

The array <NUM> comprises antennas <NUM> that can be arranged in parallel rows <NUM> and parallel columns <NUM>. In some examples, the array <NUM> is a regular array and comprises antennas <NUM> arranged in parallel rows <NUM> and parallel columns <NUM>.

For one or more columns <NUM> of the antennas <NUM> in the array <NUM>, there is an aligned arrangement of coupling elements <NUM> comprising coupling elements <NUM> between the antennas <NUM> in the respective column <NUM>. The coupling elements <NUM> are separate from the antennas <NUM> and are electrically floating.

A ground plane is a technical term that refers to a conductive element at local ground potential. It provides a common ground potential at multiple different locations within the apparatus <NUM>. However, it is not necessarily physically planar and can have any suitable physical topology. In some examples it can be physically planar. In some examples it can be physically planar and also flat.

In some but not necessarily all examples, in use, the columns <NUM> are aligned along virtual vertical lines and the rows <NUM> are aligned along virtual horizontal lines. In this orientation, the antennas <NUM> are separated vertically by coupling elements <NUM>.

The antennas <NUM> can be any suitable antennas. In the following examples patch antennas <NUM> are used.

Referring to <FIG>, the array <NUM> has patch antennas <NUM> aligned in columns <NUM> and aligned in rows <NUM>.

Each of the M rows has N patch antennas <NUM> and each of the N columns has M patch antennas <NUM>. The patch antennas <NUM> in at least some of the columns of the array <NUM> are separated by coupling elements <NUM>. The coupling elements <NUM> in a particular column form an aligned arrangement. The coupling elements are aligned along virtual lines <NUM> that run parallel to the columns.

In this example, but not necessarily all examples, patch antennas <NUM> of the array <NUM> are separated, vertically, by coupling elements <NUM>.

The coupling elements <NUM> are separate from the patch antennas <NUM> and are electrically floating. The conductive elements <NUM> are conductive and are not galvanically connected to an electric potential, for example the ground plane <NUM>, or another conductive part of the apparatus <NUM>. This allows the electrostatic potential of a coupling element <NUM> to 'float'.

The arrangement of coupling elements <NUM>, in the example of <FIG>, has a number of distinctive characteristics. For example, only one coupling element <NUM> is between neighboring patch antennas <NUM> in the column <NUM> direction. For example, for the rows <NUM> of patch antennas <NUM> in the array <NUM>, there is no coupling element between the patch antennas <NUM> in the same row. For example, the columns <NUM> that have coupling elements <NUM> have the same coupling element <NUM> between patch antennas <NUM> in that column, that is, the coupling elements <NUM> in a column have the same characteristics such as shape, size and position relative to the patch antennas <NUM>. Thus any respective column <NUM> of the aligned <NUM> arrangement of coupling elements <NUM> comprises coupling elements <NUM> of the same size and shape between the patch antennas <NUM> of the respective column.

The arrangement of coupling elements <NUM>, in the example illustrated, has reflection symmetry in a virtual mid-line (not illustrated) through boresight and parallel to the columns <NUM> of the array <NUM> and has reflection symmetry in a virtual mid- line (not illustrated) through boresight and parallel to the rows <NUM> of the array <NUM>. The example arrangement of coupling elements <NUM> has <NUM> degree rotational symmetry about the boresight but does not have <NUM> degree rotational symmetry about the boresight.

The coupling elements <NUM> increases cross-polarization discrimination for the array <NUM> of patch antennas <NUM>, at boresight (a direction orthogonal to a flat plane of the array <NUM> of patch antennas <NUM>). In at least some examples, the cross-polarization component of electric field is decreased at the boresight by the presence of the coupling elements <NUM>.

<FIG> illustrates cross-polarization discrimination (XPD) for the array <NUM> of patch antennas <NUM>, at boresight, without the coupling elements <NUM> (dotted line) and with the coupling elements <NUM> (solid line). It can be seen that the presence of the coupling elements <NUM> increase cross-polarization discrimination for the array <NUM> of patch antennas <NUM>, at boresight.

As illustrated in more detail in <FIG>, the coupling elements <NUM> are, in at least some examples, elongate coupling elements <NUM> having a length L greater than a width W. The coupling element <NUM> has a strip shape. In the illustrated example, the width W is greater than a depth D. In at least some examples, the length L of the elongate coupling elements <NUM> extends vertically, the width W of the coupling elements <NUM> extends horizontally and a depth (or height) of the coupling elements <NUM> extends outwardly. In the illustrated example, the coupling elements <NUM> are flat conductive elements (without slots or walls). The coupling elements <NUM> are galvanically isolated from each other and other conductors. The term 'galvanically isolated' means that there is no conductive direct current path.

Referring back to the example, of <FIG> the aligned arrangement of coupling elements <NUM> in the respective columns <NUM> are aligned lengthwise along the virtual lines <NUM>. In the particular example illustrated, a virtual line <NUM> travels lengthwise through the coupling elements <NUM> in a column <NUM> and bi-sects each of the coupling elements <NUM> widthwise.

In the illustrated examples and other examples, the coupling elements <NUM> have a fixed, constant width along their length. However, in some other examples, the coupling elements can have a variable width along their length. For example, the coupling elements <NUM> can be tapered.

In at least some examples, some or all of the patch antennas <NUM> of the array <NUM> has a patch radiator <NUM> and feeds <NUM> for a first polarization and a second polarization orthogonal to the first polarization. <FIG> illustrates in cross-sectional view an example of such a patch antenna <NUM>. In <FIG>, the radiator <NUM> of patch antenna <NUM> is separated from the feeds <NUM> by dielectric <NUM>. In this example, the boresight direction is vertical within the plane of the paper.

The patch radiators <NUM> also form an array corresponding to the array <NUM>. In at least some examples, some or all of the patch radiators <NUM> of the array have the same operational frequency range (or ranges). Consequently, in at least some examples, some or all of the patch radiators <NUM> of the array of patch radiators have the same size and shape which define electrical characteristics such as electrical length. In at least some examples, some or all of the patch radiators <NUM> of the array of patch radiators have the same feed arrangement of feeds <NUM>.

<FIG> illustrates, in plan view, an example of a feed arrangement that provides feeds <NUM> for a first polarization and a second polarization orthogonal to the first polarization. The dual polarized feed arrangement is a balanced feed with opposing conductive feed elements <NUM> configured to provide a feed <NUM> for the first polarization and opposing conductive feed elements <NUM> configured to provide a feed <NUM> for the second polarization.

The feed elements <NUM>, <NUM> lie in a flat plane that is parallel to the plane of the patch radiator <NUM>. The feed elements <NUM> are aligned in that flat plane in a direction offset by -<NUM> degrees from a direction in that flat plane in which the feed elements <NUM> are aligned. The center of the feed arrangement, where virtual lines through the feed elements <NUM> and the feed elements <NUM> meet, is aligned with virtual line <NUM> (not illustrated in this FIG). This provides symmetrical coupling between the different polarizations.

In this example, the feed element of the feed <NUM>, on the combiner PCB is circular and the patch radiators are rectangular.

<FIG> illustrate some bit not necessarily all of the arrangements possible for the ground plane <NUM>, a patch radiator <NUM> of the patch antenna <NUM> and associated coupling elements <NUM>. The ground plane <NUM> lies in a flat plane, patch radiator <NUM> lies in a flat plane, the coupling element <NUM> lies in a flat plane.

In each of <FIG> the ground plane <NUM> is physically separated from the patch radiator <NUM>. The ground plane <NUM> and the patch radiator <NUM> are not co-planar. In <FIG>, the patch radiator <NUM> and its adjacent coupling element(s) <NUM> are not co-planar. In <FIG>, the patch radiator <NUM> and its adjacent coupling element(s) <NUM> are co-planar.

In <FIG>, the patch radiator <NUM> and its adjacent coupling element(s) <NUM> are provided by a printed wiring board (PWB) <NUM>. The patch radiator <NUM> occupies one side (or layer) of the PWB <NUM> and the coupling element(s) <NUM> occupy a different side (or layer) of the PWB <NUM>.

In <FIG>, the patch radiator <NUM> and its adjacent coupling element(s) <NUM> are provided by a printed wiring board (PWB) <NUM>. The patch radiator <NUM> occupies one side (or layer) of the PWB <NUM> and the coupling element(s) <NUM> occupy the same side (or layer) of the PWB <NUM>.

In <FIG>, the ground plane <NUM>, the patch radiator <NUM> and its adjacent coupling element(s) <NUM> are provided by a printed wiring board (PWB) <NUM>. In this example, ground plane <NUM> occupies one side (or layer) of the PWB <NUM>, the patch radiator <NUM> occupies a different side (or layer) of the PWB <NUM> and the coupling element(s) <NUM> occupies a side (or layer) of the PWB <NUM>. The side (or layer) of the PWB <NUM> occupied by the coupling element(s) <NUM> can be the same side (or layer) to that occupied by the patch radiator <NUM> or can be a different side (or layer) to that occupied by the patch radiator <NUM>.

In some examples, the coupling elements <NUM> of the apparatus <NUM> can occupy a common side (or layer) of the PWB <NUM>. In some examples, the coupling elements <NUM> of the apparatus <NUM> can occupy more than one side (or layer) of the PWB <NUM>.

The feeds <NUM> are not illustrated in <FIG> for clarity of illustration. The feeds will normally be provided in a single flat plane. They can be provided as part of a PWB <NUM> or separately to it. The feeds <NUM> are in some examples in a different plane to the patch radiators <NUM>. The feeds <NUM> in at least some of these examples, or in other examples, are in a different plane to the coupling elements <NUM>.

<FIG> illustrates an example of the apparatus <NUM> that comprises phase control circuitry <NUM>. Phase control circuitry <NUM> is used to control application of a phase difference between two signals.

In this example, the phase control circuitry <NUM> is configured to provide a relative phase adjustment to groups <NUM> of patch antennas <NUM> in the array <NUM> of patch antennas <NUM>. For example, the same relative phase adjustment ϕ<NUM> is applied to patch antennas <NUM> within a group <NUM><NUM> and different relative phase adjustment(s) ϕ<NUM>, ϕ<NUM>. ϕN is applied to patch antennas <NUM> in different groups <NUM><NUM>, <NUM><NUM>. <NUM>N to effect beam-steering.

For example, referring back to <FIG> to effect beam steering in an azimuthal direction (horizontal) then phase offset applied by phase control circuitry <NUM> varies across the columns. To effect beam steering in an elevation direction (vertical) then phase offset applied by phase control circuitry <NUM> varies across the rows. To effect beam steering in both an azimuthal (horizontal) and an elevation (vertical) direction then phase offset applied by phase control circuitry <NUM> varies across the columns and the across the rows.

For example, the M (M=<NUM>) row by N (N=<NUM>) column array illustrated in <FIG> could be logically divided into groups (sub-arrays) of size m (m=<NUM>) rows by n (n=<NUM>) columns. This makes a 4x8 array of groups. To effect beam steering in an azimuthal direction (horizontal) then phase offset applied by phase control circuitry <NUM> varies with each horizontal group e.g. by each column. To effect beam steering in an elevation direction (vertical) then phase offset applied by phase control circuitry <NUM> varies with each vertical group e.g. each group of m=<NUM> patch antennas <NUM> have the same phase offset and each of the four groups of m=<NUM> patch antennas <NUM> within the column of M=<NUM> patch antennas has a different phase offset. To effect beam steering in an azimuthal direction (horizontal) and elevation direction (vertical) then phase offset applied by phase control circuitry <NUM> varies with each horizontal group (e.g. each N/n groups of n=<NUM> patch antennas <NUM> have a different phase offset) and varies with each vertical group (e.g. each group of m=<NUM> patch antennas <NUM> have the same phase offset and each of the M/m (<NUM>) groups of m=<NUM> patch antennas <NUM> within the column of M=<NUM> patch antennas has a different phase offset).

The arrangement of patch antennas <NUM> and coupling elements <NUM> is not symmetric in the horizontal and vertical. For example, the size and shape of the patch radiators <NUM> are not symmetric, the spacing between patch radiators <NUM> is not symmetric, the distribution of coupling elements <NUM> is not symmetric and the shape of coupling elements <NUM> is not symmetric. For example, there may be different beam-steering requirements in the azimuthal (horizontal) and the elevation (vertical) directions. Typically, an azimuth (horizontal) beam steering angle is much wider (for example +/-50deg) than elevation (for example +/-5deg). To avoid grating lobes at large azimuth steering angles the spacing between patch radiators <NUM> can be close to half wavelength in the horizontal direction (between columns, within rows).

In the particular arrangement of coupling elements <NUM> illustrated in <FIG>, but not necessarily all examples, the coupling elements <NUM> are the same in all columns, that is, the coupling elements <NUM> in different columns have the same characteristics such as shape, size and position relative the patch antennas <NUM>. The coupling elements <NUM> do not vary their characteristics in the column direction.

However, according to the embodiments, the coupling elements <NUM> are not all the same or are not the same across all different columns.

In the example illustrated in <FIG>, which is the same as <FIG> except for the arrangement of coupling elements <NUM>, the coupling elements <NUM>, if present in a particular column, are the same that is, the coupling elements <NUM> have the same characteristics such as shape, size and position relative the patch antennas <NUM>. However, the coupling elements <NUM> in different columns are not necessarily the same and have different characteristics such as different shape, different size and/or different position relative the patch antennas <NUM>.

In <FIG>, the coupling elements <NUM> vary their characteristics in the row <NUM> direction (less coupling as one moves to the outer peripheral columns). The coupling elements <NUM> are closer to adjacent patch antennas <NUM> in a column, in a column <NUM> direction, at the center of the regular array <NUM> of patch antennas <NUM>, than in a column towards a periphery or edge of the regular array <NUM> of patch antennas <NUM>. Thus a length of a coupling elements <NUM> decreases with distance in a first direction from a center of the array <NUM> and a size of a gap (in a second direction orthogonal to the first direction) increases with distance in the first direction from the center of the array <NUM>. In the example illustrated, but not necessarily all examples, the first direction is an azimuthal (horizontal) direction and the second direction is an elevation (vertical) direction.

In some but not necessarily all examples, the apparatus <NUM> additionally comprises grounded isolation towers <NUM> as illustrated in <FIG>. The example of <FIG> is based on the previous example of <FIG> but grounded isolation towers <NUM> can be used with the example of <FIG> or other examples.

The grounded isolation towers <NUM> are conductive elements that extend outwardly from the plane of the page and have a depth (height) in that direction that is significant compared to in-plane dimensions such as, for example, the azimuthal (horizontal) dimension (width) or elevation (vertical) dimension (length). The grounded isolation towers <NUM> therefore have a relative height/depth, compared to width and length dimensions, that is much greater than that of a coupling element <NUM>. The grounded isolation towers <NUM> are galvanically interconnected to the ground plane <NUM>.

If a PWB <NUM> is used, then the grounded isolation towers <NUM> can be formed as vias within the PWB <NUM>, for example, extending from the ground pane <NUM>.

A grounded isolation tower <NUM> is positioned at corners of patch antennas <NUM>. For example, where four corners of four different patch antennas <NUM> face each other there is a grounded isolation tower <NUM>. The grounded isolation towers <NUM> form a regular array and are positioned where an (interstitial) space between columns <NUM> of patch antennas <NUM> and an (interstitial) space between rows <NUM> of patch antennas <NUM> meet. In the example illustrated the array <NUM> of patch antennas <NUM> is an N row by M column array. In this example, but not necessarily all examples, that array of grounded isolation towers <NUM> comprises an (N-<NUM>) row by (M-<NUM>) column array that is 'within' the array <NUM>.

In the illustrated example, the grounded isolation towers <NUM> are positioned at corners of patch antennas <NUM> in the regular array of patch antennas. In the example illustrated the array <NUM> of patch antennas <NUM> is an N row by M column array. In this example, but not necessarily all examples, that array of grounded isolation towers <NUM> is an (N+<NUM>) row by (M+<NUM>) column array. A grounded isolation tower <NUM> is positioned at each corner of each patch antenna <NUM>.

<FIG> illustrates an example of a portion of an apparatus <NUM> as previously described. It has similarities to the apparatus <NUM> illustrated in <FIG>. It comprises grounded isolation towers <NUM> and also comprises coupling elements <NUM> of variable area and/or length. <FIG> illustrates an example of a whole apparatus <NUM> of which the portion illustrated in <FIG> is a part. <FIG> illustrates an example of a part of the feed arrangement for the apparatus <NUM> of <FIG>. The feed arrangement comprises feeds <NUM> and is similar to that previously described with reference to <FIG>.

In this example the array has a length (vertical) of <NUM> and a width (horizontal) of <NUM>. The horizontal spacing between patch radiators <NUM> is <NUM>. The vertical spacing between patch radiators is <NUM>. The patch radiators are separated from the ground plane <NUM> by a distance of <NUM>.

<FIG> illustrates circuitry for providing feeds <NUM> for a first polarization and a second polarization orthogonal to the first polarization. The dual polarized feed arrangement is a balanced feed with opposing conductive feed elements <NUM> configured to provide a feed <NUM> for the first polarization and opposing conductive feed elements <NUM> configured to provide a feed <NUM> for the second polarization.

A feed S1 for a first signal connects via a <NUM> degree balun. A feed S2 for a second signal connects via a <NUM> degree balun.

<FIG> illustrate simulated characteristics of the apparatus <NUM> as previously described. <FIG> illustrate simulated characteristics of the apparatus <NUM>, if adapted to remove the coupling elements <NUM>. A comparison of the respective figures <FIG> against <FIG> illustrates effects of the coupling elements <NUM>.

<FIG> illustrate variation of reflection coefficients S11 and S12 (range -40dB to <NUM> in <FIG>; -35dB to <NUM> in <FIG>;) with frequency (range <NUM> to <NUM> in both FIGs).

<FIG> illustrate variation of XPD Cross Polar Discrimination ("Co-polar gain" - "X-polar gain") with azimuthal angle for a beam steered at boresight. The different traces are for <NUM>, <NUM> and <NUM>.

<FIG> illustrate variation of Cross Polar Discrimination (XPD) and co-polar gain (CO) with azimuthal angle at <NUM> , for beam steering angles of <NUM>° (<FIG>), <NUM>° (<FIG>) and <NUM>° (<FIG>) where the apparatus <NUM> is without coupling elements <NUM> and <FIG> illustrate variation of Cross Polar Discrimination (XPD) and co-polar gain (CO) with azimuthal angle at <NUM> , for beam steering angles of <NUM>° (<FIG>), <NUM>° (<FIG>) and <NUM>° (<FIG>) where the apparatus <NUM> has coupling elements <NUM>. Cross Polar Discrimination XPD is the difference between the co-polar gain and cross-polar gain(log scale).

At beam steering in the boresight direction <NUM>° (<FIG>), XPD is greater over a 3dB beamwidth BW compared to <FIG>. The presence of coupling elements <NUM> significantly improves XPD at boresight.

At beam steering towards a sector edge direction <NUM>° (<FIG>), XPD is not compromised by the presence of coupling elements <NUM>.

At beam steering within the sector <NUM>° (FIG 17C), XPD is not compromised by the presence of coupling elements <NUM>.

There are similar results for other frequencies and other beam steering angles.

Cross-polar discrimination (XPD) over <NUM>-<NUM> is >20dB @ boresight and >10dB over whole steering range. Isolation towers <NUM> can be used to increase XPD at edges. Coupling elements <NUM> (and increased coupling) can be used to increase XPD at boresight.

When the coupling between patches and the coupling elements <NUM> is increased (longer coupling element) the XPD increases (X-pol component decreases) at azimuth angles close to boresight but gets worse at larger azimuth angles close to sector edges. Because the co and cross-polarization beam of the whole array <NUM> is the sum of the array <NUM> one can then use this effect to improve (or control) the overall XPD of the array <NUM> beam by using tight coupling at the middle columns <NUM> of the array <NUM> and loose coupling at the edges.

The apparatus <NUM> uses floating coupling strips <NUM> added between patch radiators <NUM> to adjust the cross polar component level of each column <NUM> of the array. Columns <NUM> are used to form a sum beam of the whole array <NUM>. To achieve good XPD over a wide horizontal sector, different coupling (from the coupling elements <NUM>) is applied at each array <NUM> column <NUM> depending on the column <NUM> position in the array <NUM>. Tight couplings (narrow gaps) are used at the middle columns <NUM> of the array <NUM> and loose couplings (wide gaps) or no coupling elements <NUM> are used at the array <NUM> edges. The coupling is between a specific coupling element <NUM> and a patch radiator <NUM> on either side of it in a particular column.

The apparatus has particular application as a beam steering array <NUM> for higher frequency products (><NUM>) products.

A product can be a base station system or a portable electronic device.

The apparatus can have particular application as a beam steering array <NUM> for sub-<NUM> products especially on the highest sub-<NUM> frequency variants at <NUM>-<NUM>. Element cross-polar discrimination (XPD) over <NUM>-<NUM> band needs to be >20dB @ boresight and >10dB over whole steering range to minimize leakage between MIMO channels and also to minimize channel noise.

The apparatus <NUM> provides a digital beam steering array <NUM> below <NUM> that supports multi-user-MIMO (multi-input multi-output) and provides sufficient horizontal and vertical beam steering range over a wide frequency bandwidth with stable peak gain. The manufacturing cost of the apparatus <NUM> is low and it is light weight (low mass).

Although the above example focuses on the frequency range <NUM>-<NUM>, the same approach can be used at other frequencies.

<FIG> illustrates an example of product <NUM>, for example a portable electronic device or a base station system (or part of a base station system).

Thea base station system <NUM> (or part of a base station system) can be configured for beamforming, for example, multiple-input multiple-output (MIMO) operation and can comprise the apparatus <NUM> as previously described for beam-steering.

An operational resonant mode (operational bandwidth) is a frequency range over which an antenna can efficiently operate. An operational resonant mode (operational bandwidth) may be defined as where the return loss S11 of the antenna is greater than an operational threshold T.

The above described examples find application as enabling components of:.

The term 'a' or 'the' is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a/the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use 'a' or 'the' with an exclusive meaning then it will be made clear in the context. In some circumstances the use of 'at least one' or 'one or more' may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

Claim 1:
An apparatus (<NUM>) comprising:
a ground plane (<NUM>);
an array (<NUM>) of antennas (<NUM>), wherein the array comprises antennas arranged in parallel rows (<NUM>) and at least three parallel columns (<NUM>);
for one or more columns of the antennas in the array, there is an aligned arrangement of coupling elements (<NUM>) comprising coupling elements between the antennas in the respective column,
wherein the coupling elements are separate from the antennas and are electrically floating;
wherein the coupling elements are closer to adjacent antennas in a column of the array, in a column direction, for a column towards a center of the array of antennas than for a column towards a periphery of the array of antennas; and
wherein each of the antennas in the array of antennas comprises a radiator (<NUM>) and feeds (<NUM>) for a first polarization and a second polarization orthogonal to the first polarization.