Patent Description:
With the deployment of LTE systems, network operators are adding new spectrum to networks, in order to increase their network capacity. To this end, antenna vendors are encouraged to develop new antennas with more antenna ports/arrays and supporting further frequency bands, without increasing the antenna size.

For instance, Multiple Input Multiple Output (MIMO) requirements in the current LTE standard require a duplication of the number of antenna ports/ arrays, at least in higher frequency bands. In particular, to exploit all capabilities of the current LTE standard, new antennas should necessarily support 4x4 MIMO in the higher frequency bands. Additionally, in order to be ready for future deployments, MIMO support is also desired in lower frequency bands.

At the same time, there is a growing demand for a deeper integration of antennas with Active Antenna Systems (AAS). One of the key technologies to enable new generations of mobile communications is mMIMO below <NUM>. Accordingly the integration with a mMIMO antenna array is highly desired. Integration with AAS or mMIMO antenna arrays, however, leads to highly complex systems, and thus strongly influences the antenna form factor, since it is fundamental for commercial field deployment. One of the dominant limiting factors in this context is the antenna height. Reducing the antenna height for new antennas would mean a significant simplification of the overall deployment process of an AAS or of a traditional passive antenna system.

Additionally, in order to facilitate site acquisition, and to fulfill local regulations regarding site upgrades, also the antenna width of new antennas should be at least comparable to legacy products. In particular, to maintain the mechanical support structures already existing in the sites, specifically the wind load of new antennas should be equivalent to the ones of legacy products.

All the above factors lead to very strict limitations in antenna height and width for the new antennas, despite of the requirement for more antenna ports/arrays and for further frequency bands. Furthermore, despite of these size limitations, radio frequency (RF) performance of new antennas should also be equivalent to legacy products, in order to maintain (or even improve) the coverage area and network performance.

Specifically, when considering the performance of a radiating element included in an antenna, a reduction of the antenna height naturally implies also a reduction of the radiating element, and would lead to a reduction in the relative bandwidth that can be covered with an acceptable RF performance. Thus, in order to at least cover the standard operating bands in base station antenna systems, and to at least maintain the same RF performance, with a reduced antenna height, requires new concepts for radiating elements different from the legacy technology.

In order to meet the above-mentioned requirements for 4x4 MIMO, especially the number of higher frequency band (HB) arrays in the same antenna aperture must practically be duplicated. In order to meet also the above-mentioned size limitations, particularly regarding antenna width, these HB arrays should be placed closer to each other than in legacy antenna architectures. To this end, new concepts for especially lower frequency band (LB) radiating elements are needed, specifically ones that can coexist with tightly spaced HB arrays.

Conventional LB radiating elements are not sufficient to meet the above-mentioned requirements. Conventional LB radiating elements are either not shaped such that they can be used in multiband antenna architectures with very tightly spaced HB arrays, or they are not optimized with respect to antenna height and operating bandwidth, respectively. Furthermore, conventional LB and HB radiating elements, respectively, are not shaped and optimized in terms of their height so that they cannot be well integrated with a mMIMO array.

<CIT> discloses a broadband dual-polarized antenna and a radiating unit thereof
The documents <CIT>, <CIT>, <NPL>, and <NPL> disclose further background art.

In view of the above-mentioned challenges and disadvantages, the present invention aims to improve conventional radiating elements and conventional multiband antennas. In particular, the present invention has the object to provide a radiating element that has broadband characteristics, but is at the same time low profile. In addition, the radiating element should have a shape that allows minimum spacing between two arrays in a multiband antenna or that allows integrating it with a mMIMO array. In particular, the radiating element should allow maximized utilization of the available space in the multiband antenna aperture. Further, the shadow of the radiating element on another array of radiating elements, for instance a mMIMO array, should be minimized.

Notably, broadband characteristics here means a relative bandwidth of larger than <NUM>%. Low profile means that the antenna height is smaller than <NUM>. 15λ, wherein λ is the wavelength at the lowest frequency of the frequency band of the operating radiating element.

The object of the present invention is achieved by the solutions provided in the enclosed independent claims.

The main idea of the present invention is combining, in the provided radiating element, a dipole feeding concept, in order to provide broadband characteristics, with a radiating element shape, which is optimized to work in a multiband antenna together with tightly spaced arrays of other radiating elements, for instance a mMIMO array.

A first aspect of the present invention provides a dual-polarized radiating element, comprising a feeding arrangement comprising four feedable slots, which extend from a periphery towards a center of the feeding arrangement and are arranged at regular angular intervals forming a first angular arrangement, and four dipole arms, which extend outwards from the feeding arrangement and are arranged at regular angular intervals forming a second angular arrangement, wherein the second angular arrangement of the four dipole arms is rotated with respect to the first angular arrangement of the four slots.

The feeding arrangement comprises four transmission lines, each transmission line crossing one of the four slots.

The four transmission lines are preferably short-ended microstrip lines, which feed the four slots.

The mentioned rotation is around an axis of rotation perpendicular to the extension directions of the slots and dipole arms. The axis extends through a middle of the dual polarized radiating element, from a bottom to the top of the dual polarized radiating element.

The feeding arrangement including the four slots provides the radiating element with the desired broadband characteristics. The shape of the radiating element, in particular the angular arrangements of the dipole arms and the slots, respectively, which are rotated with respect to another, provides the radiating element with the desired shape that is optimized to work in a multiband antennas together with very tightly spaced HB arrays. In particular, the shape of the radiating element minimizes its interference with higher frequency radiating elements arranged side-by-side on the same multiband antenna. This consequently allows minimizing a distance between different arrays of those higher frequency radiating elements. Particularly, the radiating element fulfils the above-mentioned conditions that it is firstly low profile, but is secondly provided with broadband characteristics.

In a first implementation form of the first aspect, the four slots and the four dipole arms, respectively, are arranged at <NUM>° intervals, and the second angular arrangement of the four dipole arms is rotated by <NUM>° with respect to the first angular arrangement of the four slots. The mentioned intervals can include a manufacturing tolerance interval e.g. ±<NUM> degrees or even only ±<NUM> degrees.

The radiating element can thus be arranged on an antenna such that its two emitted radiation polarizations are rotated by <NUM>° with respect to a longitudinal axis of the antenna. Nevertheless, the dipole arms of the radiating element are arranged such that two of the dipole arms extend in line with the longitudinal axis of the antenna, while two of the dipole arms extend laterally at a <NUM>° angle with respect to this axis. This orientation of the dipole arms allows arranging the radiating element between tightly spaced HB arrays, wherein the laterally extending dipole arms extend between other radiating elements in these HB arrays.

In a further implementation form of the first aspect, adjacently arranged slots extend perpendicular to another, non-adjacently arranged slots extend in line with another and the two in-line extending slot pairs define the two orthogonal polarizations of the dual-polarized radiating element.

In a further implementation form of the first aspect, each slot is terminated at its inner end by a symmetrically bent slot, preferably by a U-shaped slot.

The purpose of the symmetrically bent slots is extending the total length of each slot for impedance matching purposes. Since typically the slot length cannot be extended any more towards the center of the feeding arrangement, it is instead extended in a bent manner, for instance, by leading the symmetrically bent slots backwards in direction of the periphery of the feeding element.

In a further implementation form of the first aspect, at least a part of each dipole arm extends upwards and/or downwards with respect to the feeding arrangement plane. In the present disclosure, the feeding arrangement plane is a plane crossing all slots or having all slots lying in it and being perpendicular to the axis of rotation around which the second angular arrangement is rotated with respect to the first angular arrangement.

Thereby, the dipole arms can become electrically longer, without increasing their footprint. Additionally, due to an increased distance to ground, the capacitance to ground can be reduced, which allows increasing the working bandwidth.

In a further implementation form of the first aspect, each dipole arm is terminated at its outer end by a flap, particularly by a flap bent downwards or upwards with respect to the feeding arrangement plane and optionally bent back towards the feeding arrangement.

The flaps make the dipole arms of the radiating element electrically longer, without increasing their footprint.

In a further implementation form of the first aspect, the radiating element further comprises a parasitic director arranged above the feeding arrangement.

The parasitic director can be utilized to achieve the desired bandwidth, and thus to minimize the size of the radiating element.

In a further implementation form of the first aspect, the parasitic director extends outwards from the feeding arrangement less than each of the four dipole arms, and/or each dipole arm comprises an outer part extending upwards with respect to the feeding arrangement plane, and the parasitic director is arranged in a recess defined within the four outer parts.

Accordingly, the size of the radiating element, especially its width and height, are kept as small as possible.

In a further implementation form of the first aspect, two transmission lines crossing non-adjacent slots are combined into one transmission line.

Thus, a symmetrical feeding of non-adjacent slots by a common transmission line is enabled. Accordingly, the radiating element can be operated to emit radiation of two polarization directions.

In a further implementation form of the first aspect, the feeding arrangement comprises a printed circuit board (PCB), on which PCB the four transmission lines are combined into the two transmission lines, or the radiating element comprises a PCB arrangement extending from a bottom surface of the feeding arrangement, on which PCB arrangement the four transmission lines are combined into the two transmission lines.

In a further implementation form of the first aspect, the radiating element further comprises four flaps extending from the feeding arrangement, wherein each one of the four slots is extended on one of the four flaps.

Due to the four flaps, the size of the feeding arrangement, and thus of the whole radiating element, can be reduced without sacrificing performance. A size reduction of the feeding arrangement inevitably leads to less space available for the four slots, and thus leads to shorter slots. To compensate this, the four slots are electrically extended by the use of the four flaps. The extending slots may thereby divide each flap into two sub-flaps. Accordingly, the feeding arrangement plane can overall be made smaller, with the four flaps increasing its size only at the slot positions. The four flaps may even extend in an angle from the feeding arrangement, or may be bent upwards or downwards with respect to the feeding arrangement plane, in order to reduce the footprint of the radiating element even further. The size reduction of the radiating element is particularly advantageous when an antenna array including many such radiating elements is to be integrated with another array of other radiating elements, for instance, a mMIMO array. This is due to less shadowing on the other radiating elements.

In a further implementation form of the first aspect, the feeding arrangement comprises a PCB, on which the four slots are arranged into which the four dipole arms are connected.

In a further implementation form of the first aspect, the four flaps are connected to the PCB, wherein the four flaps are bent upwards with respect to the feeding arrangement plane and are arranged in between the four dipole arms, respectively.

Bending the four flaps allows extending the four slots electrically, while not significantly extending the feeding arrangement plane outwardly. Therefore, the size of the feeding arrangement can be further reduced. Bending the four flaps upwards allows to better integrate the radiating element into an array of other radiating elements of lower height, for instance in a mMIMO array. In particular, a shadowing of the other radiating elements by the dual-polarized radiating element is diminished. Consequently, the squint of the other radiating elements of e.g. the mMIMO array is significantly minimized.

In a further implementation form of the first aspect, the four flaps and the four dipole arms are formed by four separate integral elements, each integral element comprises one dipole arm and two sub-flaps and each flap is formed by two sub-flaps of adjacent integral elements.

Thereby the number of separate parts needed is reduced.

In further implementation form of the first aspect each integral element is soldered at its dipole arm with one soldering point to the PCB and at each of its two sub-flaps with one soldering point to the PCB.

Thereby, the mechanical stability of the radiating element is improved but also electrical continuity is provided.

In a further implementation form of the first aspect, the feeding arrangement further comprises a metal sheet, wherein the four slots are cutouts in the metal sheet and also the four dipole arms are formed by the metal sheet.

The advantage of this implementation form is that additional flaps can be provided at the feeding arrangement. A PCB may be placed underneath the feeding arrangement in this implementation form.

In a further implementation form of the first aspect, the metal sheet comprises the four flaps, which are bent upwards or downwards with respect to the feeding arrangement plane and are arranged in between the four dipole arms, respectively.

The additional flaps help optimizing the performance of the radiating element, by introducing a further degree of freedom for the feeding arrangement shape. In particular, the radiating element can be optimized to work together with higher frequency radiating elements, which are arranged close when deployed in a multiband antenna. Also, as described above the flaps may extend the four slots electrically, so that the size of the feeding arrangement can be reduced without loss of slot length. In this way, the radiating elements can be integrated better with an array of other radiating elements, like of a mMIMO array. The shadowing caused by the radiating element on the radiating elements of such a mMIMO array is significantly reduced.

A second aspect of the present invention provides an antenna, comprising at least one dual-polarized radiation element according to the first aspect as such or any implementation form of the first aspect, wherein two dipole arms of the at least one dual-polarized radiating element extend along a longitudinal axis of the antenna, and two dipole arms of the at least one dual-polarized radiating element extend along a lateral axis of the antenna.

Due to the shape of the radiating element, and the specific arrangement of the one or more radiating elements on the antenna, a distance of the radiating elements to HB arrays can be minimized. Therefore, either the total width of the antenna can be minimized, or the number of HB arrays can be increased within an unchanged antenna width.

In an implementation form of the second aspect, each slot of the at least one dual-polarized radiating element extends at an angle of <NUM>° with respect to the longitudinal axis of the antenna.

Thus, <NUM>° polarizations of the emitted radiation are obtained, as required in current antenna specifications.

In a further implementation form of the second aspect, the antenna comprises a plurality of dual-polarized radiating elements arranged along the longitudinal axis of the antenna in at least a first column, and a plurality of other radiating elements arranged along the longitudinal axis of the antenna in at least two second columns disposed side-by-side the at least first column, wherein the dipole arms of the dual-polarized radiating elements extend between the other radiating elements in the at least two second columns.

In this way, the arrangement of the at least three columns can be made as dense as possible, so that the overall antenna width can be minimized. For example, this allows overlaying an array of the dual-polarized radiating elements with a mMIMO array of the other radiating elements.

In a further implementation form of the second aspect, the antenna is configured for multiband operation, and the dual-polarized radiating elements are configured to radiate in a lower frequency band and the other radiating elements are configured to radiate in a higher frequency band.

That is, the radiating element is designed for working in an LB array. In this antenna, interference and shadowing on the higher frequency band radiating elements in HB arrays can be minimized.

In a further implementation form of the first aspect, a plurality of dual-polarized radiating elements are interleaved with a plurality of other radiating elements that form a mMIMO array.

Accordingly, a mMIMO array is integrated with a passive antenna array. It is also possible to integrate a mMIMO array with different kinds of passive antenna arrays.

The above-described aspects and implementation forms of the present invention will be explained in the following description of specific embodiments in relation to the enclosed drawings in which.

It is noted that the embodiments with respect to <FIG> are not part of the invention, but illustrative examples helpful for understanding the invention.

<FIG> shows a dual-polarized radiating element <NUM> according to an embodiment of the present invention. The radiating element <NUM> comprises a feeding arrangement <NUM>, and four dipole arms <NUM>. It further exhibits a specific angular arrangement of its components.

The feeding arrangement <NUM> comprises four slots <NUM>, which extend from a periphery towards a center of the feeding arrangement <NUM>, and are arranged at regular angular intervals <NUM>, which forms a first angular arrangement. In particular, two adjacent slots <NUM> in the first angular arrangement are arranged with an angle α in between. Further, each of the slots <NUM> extends from the periphery of the feeding arrangement <NUM> to a center portion of the feeding arrangement <NUM>, preferably in a radial manner.

The four dipole arms <NUM> extend outwards from the feeding arrangement <NUM>, and are arranged at regular angular intervals <NUM>, which forms a second angular arrangement. In particular, two adjacent dipole arms <NUM> in the second angular arrangement are arranged with an angle β in between. A dipole arm <NUM> is a structural element extending from the feeding arrangement <NUM>, with a length in extension direction that is larger than its width. Preferably, each of the dipole arms <NUM> has further a width that is smaller than the width of the feeding arrangement <NUM> side, from which it extends.

The second angular arrangement of the four dipole arms <NUM> is rotated <NUM> with respect to the first angular arrangement of the four slots <NUM>, particularly by an angle Φ <NUM>.

<FIG> shows another radiating element <NUM> according to an embodiment of the present invention, which builds on the radiating element <NUM> shown in <FIG>. Identical elements in these two <FIG> and <FIG> are provided with the same reference signs.

In particular, the radiating element <NUM> of <FIG> has the four slots <NUM> and four dipole arms <NUM>, which are here respectively arranged at <NUM>° intervals each. Further, the angular arrangements of the dipole arms <NUM> and the slots <NUM> are here rotated with respect to each other by <NUM>°. Accordingly, the radiating element <NUM> extends with its dipole arms <NUM> mainly in two perpendicular directions (referred to as vertical and horizontal directions, respectively), but the polarizations of the radiating element <NUM> will lie at ±<NUM>° to these horizontal and vertical directions. <FIG> specifically shows that adjacently arranged slots <NUM> extend perpendicular to another, and that non-adjacently arranged slots <NUM> extend in line with another in this radiating element <NUM>. Thus, two in line extending slot pairs are defined.

The two in line extending slot pairs define the two ±<NUM>° orthogonal polarizations of the dual-polarized radiating element <NUM>, when it is operated. To this end, the radiating element <NUM> is fed in operation preferably like a conventional square dipole, whereby the four slots <NUM> of the feeding arrangement <NUM> are particularly fed symmetrically <NUM>-by-<NUM>.

<FIG> also shows that each of the four slots <NUM> ends in a symmetrically bent, more or less U-shaped slot <NUM>. The purpose of the four slots <NUM> is to extend the total length of each of the four slots <NUM>, particularly for impedance matching purposes. Since the length of the four slots <NUM> cannot be extended further to a center portion of the feeding arrangement <NUM> (due to a lack of space in the middle), they can only be extended to the sides and backwards. In order to thereby maintain the symmetry, the bent slot <NUM> preferably have the same pattern at both sides of a slot <NUM>. This leads to the symmetrically bent slots <NUM>, preferably the shown U-shaped ones.

The feeding arrangement <NUM> shown in <FIG> comprises a PCB <NUM>, and the four dipole arms <NUM> are soldered to the PCB <NUM> through soldering pins <NUM>. The soldering pins <NUM> cross the PCB <NUM> from bottom to top. Capacitive coupling between the four dipole arms <NUM>, and to the PCB <NUM>, is possible. However, in this case the coupling area should be dimensioned accordingly, in order to achieve enough coupling. It should also be ensured that the distance between the dipole arms <NUM> and the PCB <NUM> is small and stable.

Preferably, the dipole arms <NUM> do not extend only horizontally and vertically, but - as shown in <FIG> - also in the third perpendicular dimension, i.e. along a z-axis. In other words, at least a part <NUM> of each dipole arm <NUM> preferably extends upwards and/or downwards with respect to the feeding arrangement plane in which the feeding arrangement is arranged <NUM>. In <FIG>, each dipole arm <NUM> extends upwards in a part <NUM>. By extending in the z-axis, the dipole arms <NUM> can be made longer electrically, without increasing their footprint. Furthermore, also a distance to ground can be increased, which reduces the capacitance to ground, and therefore increases the working bandwidth. Most importantly, all these advantages come for free, because the total height of the radiating element <NUM> does not need to be increased. This is explained below with respect to <FIG>.

As further shown in <FIG>, the dipole arms <NUM> are preferably terminated with flaps <NUM>, which make the dipole arms <NUM> again electrically longer, without increasing their footprint. Preferably, as shown in <FIG>, the flaps <NUM> are bent downwards. However, it is also possible to have upwards or downwards bent flaps <NUM>, and even a bending of flaps <NUM> back towards the feeding arrangement <NUM> is possible. Examples of alternative flaps <NUM> will be provided with respect to other figures further below. Also described further below is an optional support <NUM> for the radiating element <NUM>.

<FIG> shows a comparison of simulations of a current-density plot in a radiating element <NUM> (left side) according to <FIG>, and in a conventional square-shaped radiating element <NUM> (right side). In the conventional radiating element <NUM>, most of the current is concentrated in slots <NUM> of a feeding arrangement <NUM>, whereas in the radiating element <NUM> the dipole is reshaped in such a way, that the current flows horizontally and vertically instead. The horizontal and vertical components of the current are equal, and the combination generates the ±<NUM>° polarizations. This advantageously allows to maximize the surface efficiency of the radiating element <NUM>, which means that practically the whole surface of the radiating element <NUM>, i.e. both of the feeding arrangement <NUM> and the dipole arms <NUM>, contributes to the radiation. The amount of metallic surface is thus optimized. In the conventional square-shaped radiating element <NUM>, there is a big surface amount that practically does not contribute to the radiation. Nevertheless, its presence inside, for instance, a multiband antenna, will create shadows on and interference with other radiating elements working in different, especially in higher frequency bands.

For the radiating element <NUM>, the feeding of the slots <NUM> is, as for a conventional square dipole, but the current distribution corresponds more to a cross dipole. Therefore, advantages of both dipole kinds are combined, and the radiating element <NUM> has broadband characteristics, but at the same time a very small footprint.

<FIG> shows another radiating element <NUM> according to an embodiment of the present invention. The radiating element <NUM> of <FIG> builds on the radiating element <NUM> shown in <FIG>. Identical elements in these two <FIG> and <FIG> are provided with the same reference signs. <FIG> shows a radiating element <NUM> that further comprises a parasitic director <NUM>, which is preferably arranged above the feeding arrangement <NUM>. The parasitic director <NUM> further helps to achieve the required bandwidth, and at the same time to minimize the dimensions of the radiating element <NUM>.

<FIG> shows a side view of the radiating element <NUM> that is shown in <FIG>. In <FIG>, it shows that preferably the parasitic director <NUM> extends outwards from the feeding arrangement <NUM> less than each one of the four dipole arms <NUM>. Thus, the parasitic director <NUM> does not increase the width and length of the radiating element <NUM> in the horizontal and vertical directions, respectively. Further, additionally or optionally, each dipole arm <NUM> may comprise, as shown in <FIG>, an outer part <NUM> that extends upwards with respect to the feeding arrangement plane. Then, the parasitic director <NUM> is preferably arranged in a recess <NUM>, which is defined within the four outer parts <NUM>. Thus, the parasitic director <NUM> does also not increase the height of the radiating element <NUM>. Further, as mentioned above, the dipole arms <NUM> are extended electrically in length due to the parts <NUM>, however, preferably not above the above plane of the parasitic director <NUM>. The height of the radiating element <NUM> of <FIG> is, for example assuming an operating frequency band of <NUM> - <NUM>, about <NUM>. That means, the height of the radiating element <NUM> is about <NUM>. 15λ at <NUM>, wherein λ is the wavelength corresponding to the respective frequencies. That is, it is a low profile radiating element <NUM>.

<FIG> shows another radiating element <NUM> according to an embodiment of the present invention in a bottom view. Elements shown in <FIG> and identical elements in the previous figures, are provided with the same reference signs. The PCB <NUM> carrying the feeding arrangement <NUM> and the slots <NUM>, <NUM> is visualized transparent in <FIG>, so that the crossings between the (feeding) transmission lines <NUM> and the slots <NUM> can be easily seen.

<FIG> shows that the feeding arrangement <NUM> further comprises four transmission lines <NUM>, wherein each transmission line <NUM> crosses one of the four slots <NUM>. The transmission lines <NUM> are preferably short-ended microstrip lines. The transmission lines <NUM> are particularly used for feeding the four slots <NUM>, and are combined, in order to feed two non-adjacent slots <NUM> in an identical manner. This leads to the dual polarization of the radiating element <NUM>. In <FIG>, the combination of the four transmission lines <NUM> into two transmission lines <NUM> is carried out on a PCB arrangement <NUM>. In particular, this PCB arrangement <NUM> extends from a bottom surface of the feeding arrangement <NUM>. The PCB arrangement <NUM> may specifically extend orthogonally from the feeding arrangement <NUM>. Because the four transmission lines <NUM> are combined into the two transmission lines <NUM>, firstly a feeding signal can be transmitted from the PCB arrangement <NUM> to, for example, a PCB <NUM> of the feeding arrangement <NUM>, and secondly the radiating element <NUM> can be grounded.

For instance, a ground of the PCB arrangement <NUM> may be connected (e.g. soldered) to a ground of the feeding arrangement <NUM>. The PCB arrangement <NUM> may also be connected to an additional PCB, which serves, for instance, as a transition between the radiating element <NUM> and a feeding network. Other implementations, like a direct connection to a phase shifter, or a direct connection to a coaxial cable, are also possible.

<FIG> shows another radiating element <NUM> according to an embodiment of the present invention, in which the transmission lines <NUM> are combined into transmission lines <NUM> in a different manner than in <FIG>. Nevertheless, identical elements in the two <FIG> are provided with the same reference signs. In particular, in <FIG> the combination of the four transmission lines <NUM> into two transmission lines <NUM> is carried out on the feeding arrangement <NUM>, particularly, on the PCB <NUM> of the feeding arrangement <NUM>. Thereby, the number of total soldering points can be reduced, since only two signal paths are present, instead of four. Furthermore, slots in the center of the PCB <NUM> can be divided into four small slots, which offers advantages in terms of isolation between different frequency bands.

<FIG> shows a dielectric support <NUM>, onto which the radiating element <NUM> according to an embodiment of the present invention can be mounted. This is also indicated in the previous figures showing the radiating elements <NUM>. The dielectric support <NUM> advantageously ensures mechanical stability of the radiating element <NUM>, and ensures that a distance from the radiating element <NUM> to an antenna reflector, as well as a distance from a parasitic director <NUM> to the radiating element <NUM>, is stably maintained. The dielectric support <NUM> may specifically comprise support feet <NUM>, which also define a distance of the radiating element <NUM> to, for example, a feeding network or to the antenna reflector. Further, the support <NUM> can include support elements <NUM>, in order to stably support the four dipole arms <NUM> of the radiating element <NUM>. The support <NUM> can also comprise attachment means <NUM>, which are configured to hold the feeding arrangement <NUM>, and preferably the parasitic director <NUM>.

<FIG> shows a radiating element <NUM> according to an embodiment of the present invention. Elements in <FIG> and identical elements in the previous figures, are provided with the same reference signs. In <FIG> the feeding arrangement <NUM> of the radiating element <NUM> is made out of one single bent metal sheet together with the dipole arms <NUM>, instead of comprising a PCB <NUM> and the four dipole arms <NUM> attached thereto. In particular, the feeding arrangement <NUM> comprises a metal sheet <NUM>, wherein the four slots <NUM> are preferably cutouts in the metal sheet <NUM>, and also the four dipole arms <NUM> are formed by the metal sheet <NUM>. This has, for example, the advantage that the metal sheet <NUM> can be easily designed with four further flaps <NUM>, which may be arranged in between the four dipole arms <NUM>. The further flaps <NUM> may be bent upwards or downwards with respect to the feeding arrangement plane. Furthermore, the slots <NUM> may further extend along the flaps <NUM>. Thereby, the extending slots <NUM> may actually divide each of the four flaps <NUM> into to two sub-flaps, as it is shown in <FIG>. By means of the flaps <NUM>, the slots <NUM> can be either be electrically extended without changing the size of the feeding arrangement <NUM>, or the size of the feeding arrangement <NUM> can be reduced without reducing the length of the slots <NUM>. In <FIG>, the flaps <NUM> are bent downwards, and furthermore slightly back towards the feeding arrangement <NUM>. However, the flaps <NUM> could also be bent upwards, in order to allow a better integration with an array of other radiating elements that are less high than the radiating element <NUM>. Further, as shown in <FIG>, also the dipole arms <NUM> can have additional bends, for instance, side flaps <NUM> for increasing the electrical width of the dipole arm <NUM>. The side flaps <NUM> may be formed by bending the dipole arms <NUM> along their extension direction. The slots <NUM> can be fed by transmission lines on a PCB e.g. arranged below the metal sheet <NUM>. In a further embodiment the slots <NUM> may be fed using a suitable cable feed e.g. arranged below the metal sheet <NUM>.

<FIG> shows yet another radiating element <NUM> according to an embodiment of the present invention, which builds for instance on the radiating element <NUM> shown in <FIG>. Identical elements in these two <FIG> and <FIG> are provided with the same reference signs. In <FIG>, the flaps <NUM> terminating the dipole arms <NUM> are not only bent downwards, but also back towards the feeding arrangement <NUM>. This provides further electrical length to the dipole arms <NUM>. Further, the optional parasitic capacitor <NUM> is shown to be arranged above the feeding arrangement <NUM>, and particularly within the extension length of the four dipole arms <NUM>.

<FIG> shows another radiating element <NUM> according to an embodiment of the present invention, which builds on the radiating element <NUM> shown in <FIG>. Identical elements in these two <FIG> and <FIG> are provided with the same reference signs. Here, in <FIG>, the dipole arms <NUM> extend outwards from the feeding arrangement <NUM> and are terminated by upward bent flaps <NUM>, respectively, for increasing their electrical length. Also, the optional PCB arrangement <NUM> extending from the feeding arrangement <NUM> is shown. The PCB arrangement <NUM> may serve also as mechanical support, for instance, instead of the support <NUM>.

Notably, with respect to the above-described radiating elements <NUM>, the decision of whether terminating flaps <NUM> of the dipole arms <NUM> are bent upwards or downwards can be decided after a detailed optimization process of the radiating element <NUM>. The decision can, for instance, depend on the arrangement of the radiating element <NUM> on an antenna, particularly together with other radiating elements arranged side-by-side the radiating element <NUM>.

<FIG> and <FIG> show RF performance of the radiating element <NUM> according to an embodiment of the present invention. Specifically, the Voltage Standing Wave Ratio (VSWR) and the radiation pattern of the radiating element <NUM> are shown. <FIG> specifically shows that the VSWR is below <NUM> dB (<NUM>:<NUM>) from <NUM>-<NUM>. <FIG> shows that the radiation pattern is symmetric, the 3dB beamwidth is around <NUM> degree and the Cross-polar discrimination is above <NUM> dB in the range from +<NUM> to -<NUM> degree.

<FIG> shows, how the radiating element <NUM> according to an embodiment of the present invention can advantageously be arranged in a multiband antenna architecture. At both sides of the radiating element <NUM>, there are provided other radiating elements <NUM>, for instance, configured to work in a higher frequency band like in HB arrays. Due to the shape of the radiating element <NUM>, a distance between the other radiating elements <NUM> on either side of the radiating element <NUM> can be minimized, namely by arranging the other radiating elements <NUM> nested with the dipole arms <NUM> that extend from the feeding arrangement <NUM> of the radiating element <NUM>. Therefore, either the dimensions of the multiband antenna architecture can be reduced, or the number of HB arrays within the same dimensions of the architecture can be increased.

<FIG> shows in this respect an antenna <NUM> according to an embodiment of the present invention. The antenna <NUM> comprises three columns of radiating elements, each column extending along a longitudinal axis <NUM> of the antenna <NUM>. In particular, the radiating elements <NUM> are arranged in a first column <NUM>, which is located in between and side-by-side two second columns <NUM> comprising the other radiating elements <NUM>. Preferably, the second columns <NUM> are HB arrays, and the first column <NUM> is an LB array. <FIG> again shows, how two of the dipole arms <NUM> of each radiating element <NUM> extend between two of the other radiating elements <NUM> in the HB arrays, i.e. they extend along a lateral axis <NUM> of the antenna <NUM>. The other two dipole arms <NUM> of each radiating element <NUM> extend along the longitudinal axis <NUM> of the antenna <NUM>. This allows a very dense packing of the respective HB and LB arrays. However, as also desired, the radiation polarizations defined by the slots <NUM> of the radiating elements <NUM> are still ±<NUM>° with respect to the longitudinal axis <NUM> of the antenna <NUM>.

<FIG> shows another radiating element <NUM> according to an embodiment of the present invention, which builds on the radiating element <NUM> shown in <FIG>. Identical elements in these two <FIG> and <FIG> are provided with the same reference signs. Here, in <FIG>, the radiating element comprises four further flaps <NUM> extending from the feeding arrangement <NUM>. In particular, the four flaps <NUM> are connected to a PCB <NUM>, and are preferably bent upwards with respect to the feeding arrangement plane. The four flaps <NUM> are arranged in between the four dipole arms <NUM>, respectively. Each one of the four slots <NUM> further extends along the flaps <NUM>, that means, it is electrically extended on one of the four flaps <NUM>. Thereby, each flap <NUM> may be formed by two sub-flaps <NUM> creating one slot extension, as it is shown in <FIG>. Accordingly, the radiating element <NUM> comprises in this case eight sub-flaps <NUM>.

The radiating element <NUM> shown in <FIG> is particularly advantageous for integrating an array of many such radiating elements <NUM> with another array of other radiating elements <NUM>, for instance with a mMIMO array. This is due to the fact that the shown modifications of the radiating element <NUM> improve the isolation and squint of closely spaced mMIMO radiating elements <NUM> in such a mMIMO array. For instance, the size of the PCB <NUM> can be reduced without sacrificing length of the slots <NUM>, which is enabled by the flaps <NUM> allowing to electrically extend the slots <NUM>. The flaps <NUM> are preferably folded upwards, in order to minimize the squint of the lower-lying mMIMO array.

Furthermore, the size of the parasitic director <NUM> may also be minimized to minimize the radiating element <NUM> as a whole. Any loss of bandwidth that results from this size decrease of the parasitic director <NUM> can preferably be compensated by increasing at the same time the height of the radiating element <NUM>. Additionally, in contrast to the parasitic director <NUM> shown in <FIG>, <FIG> or <FIG>, the shape of the parasitic director <NUM> may be changed. The parasitic director <NUM> shown in <FIG> does not have any flaps or arms extending from its central part. Preferably, the parasitic director <NUM> has an octagonal shape as it is shown in <FIG>. Preferably, four sides of the octagonal parasitic director <NUM> are arranged at the same positions and at the same angular intervals of the second angular arrangement formed by the dipole arms <NUM>. Preferably, the other four sides of the octagonal parasitic director <NUM> are arranged at the same positions and at the same angular intervals of the first angular arrangement formed by the four slots <NUM>. Alternatively, however, the director <NUM> may also have a round shape, or a shape with more than eight sides.

The radiating element <NUM> of <FIG> can be further optimized for integration with a mMIMO array by having preferably dipole arms <NUM> that are folded downwardly. That is, at least a part <NUM> of each dipole arm <NUM> extends downwards with respect to the feeding arrangement plane. Optionally, the dipole arms <NUM> are further bent back towards the feeding arrangement <NUM>.

<FIG> shows the radiating element <NUM> of <FIG> in a top view. The first and second angular intervals <NUM> and <NUM> of the four slots <NUM> and the four dipole arms <NUM>, respectively, are shown, and the above-described preferred shape and orientation of the preferred octagonal parasitic director <NUM> is illustrated.

<FIG> shows a radiating element according to an embodiment of the present invention, which builds on the radiating element <NUM> shown in <FIG>. The radiating element <NUM> in <FIG> is shown without a parasitic director <NUM>. The four slots <NUM> can thus be seen well, here they are provided on the PCB <NUM>, and it can be seen how they extend onto the four flaps <NUM>. It can also be seen that each flap <NUM> is preferably soldered with two soldering points <NUM> to the PCB <NUM>. In particular, in case of the flaps <NUM> being formed by sub-flaps <NUM> creating the slot extensions, each sub-flap <NUM> is preferably soldered with one soldering point <NUM> to the PCB <NUM> as shown in <FIG>. Further, each dipole arm <NUM> is preferably soldered with one soldering point <NUM> to the PCB <NUM>. These soldering points <NUM> improve the mechanical stability of the radiating element <NUM> and also electrical continuity is provided.

<FIG> shows exemplary parts of a radiating element <NUM> according to an embodiment of the present invention, for instance, parts of the radiating element <NUM> of <FIG>. Here in <FIG>, each one of the four flaps <NUM> is formed by two-sub flaps <NUM>. Further, the four dipole arms <NUM> and the four flaps <NUM> are formed by four separate integral elements <NUM>. Each integral element is formed by one dipole arm <NUM> and two (opposing) sub-flaps <NUM>, particularly with one sub-flap <NUM> being arranged on either side of the dipole arm <NUM>. For instance, two metallic sub-flaps <NUM> with a metallic dipole arm <NUM> in-between them may form one integral element <NUM>. The four integral elements <NUM> are arranged such in the radiating element <NUM> that their diploe arms <NUM> are arranged at the regular intervals <NUM> forming the second angular arrangement, preferably that their dipole arms <NUM> are arranged at <NUM>° intervals. Further, the four integral elements <NUM> are arranged such in the radiating element <NUM> that two sub-flaps <NUM> of two adjacent integral elements <NUM> form one flap <NUM> and accordingly create an extension for one of the four slots <NUM>. Such a particular arrangement of integral elements <NUM> is shown in <FIG>.

The four integral elements <NUM> improve further the mechanical stability of the radiating element <NUM>. Each integral element <NUM> is preferably soldered at its dipole arm <NUM> with one soldering point <NUM> to the PCB <NUM>, and at each of its two sub-flaps <NUM> with one soldering point <NUM> to the PCB <NUM> for the best mechanical stability. However, it is also possible to form the four dipole arms <NUM> and the four flaps <NUM>, respectively, in a different manner. In particular, two sub-flaps <NUM> forming one flap <NUM> need not necessarily belong to two separate integral elements <NUM>, but could be formed by a single integral piece, like the flaps <NUM> shown in <FIG>.

<FIG> shows a radiating element <NUM> according to an embodiment of the present invention, which builds on the radiating element shown in <FIG>. The further flaps <NUM> and the extensions of the slots <NUM> on each of these flaps <NUM> are well visible. Further, it can be seen that a PCB arrangement <NUM> may extend from the bottom surface of the feeding arrangement <NUM>, particularly from the PCB <NUM>. On the PCB arrangement <NUM> preferably four transmission lines <NUM> that are coming from the PCB <NUM> are combined into two transmission lines <NUM>.

<FIG> shows a radiating element <NUM> according to an embodiment of the present invention, which builds on the radiating element <NUM> of <FIG>, and is working in a multiband antenna architecture. The radiating element <NUM> is arranged such that its dipole arms <NUM> extend between the other radiating elements <NUM> that are arranged in at least two columns. Preferably, these other radiating elements <NUM> form a mMIMO array. It can be seen that due to the fact that the radiating elements <NUM> comprises the upwards bent flaps <NUM>, wherein the flaps <NUM> electrically extend each of the four slots <NUM>, the form factor of the radiating elements <NUM> can be made much smaller. Therefore, the other radiating elements <NUM> are less shadowed. Accordingly, the squint of the mMIMO array and its radiating elements is minimized.

<FIG> shows a radiating element <NUM> according to an embodiment of the present invention working in a multiband antenna architecture with other radiating elements <NUM>. For purposes of illustration, a conventional, disc-shaped radiating element <NUM> is shown in comparison to the radiating element <NUM>, as it would be arranged if integrated with the array of other radiating elements <NUM>. It can be seen that the radiating element <NUM>, due to its small footprint and its smarter space filling, results in a much lower shadowing effect on the other radiating elements <NUM> than the conventional radiating element <NUM>.

<FIG> shows a plurality of radiating elements <NUM> according to embodiments of the present invention working in a multiband antenna architecture integrated with a mMIMO array. The radiating elements <NUM> are preferably arranged in at least one column along the longitudinal axis <NUM> or direction of the antenna <NUM>. In case of more than one column, these columns are separated along the lateral axis <NUM> or direction of the antenna <NUM>. The other radiating elements <NUM> form the mMIMO array, which preferably includes the other radiating elements <NUM> arranged in a plurality of columns. The radiating elements <NUM> may be arranged in gaps or in increased radiating element spacings or in vacant positions created by left-out radiating elements <NUM> in these columns, respectively. The radiating elements <NUM> are thus preferably interleaved with the plurality of other radiating elements <NUM>. Thereby, different types and/or sizes of dual-polarized radiating elements <NUM> can be used, for instance, to operate in different kinds of frequency bands in overlap with the mMIMO array.

In summary, the detailed description and the figures show, that and how the radiating element <NUM> is made low profile, but is at the same time provided with broadband characteristics. Furthermore, that and how the radiating element <NUM> has a shape that minimizes interference with other radiating elements <NUM> arranged side-by-side in a multiband antenna <NUM>, and minimizes the width of the antenna <NUM>.

Claim 1:
Dual-polarized radiating element (<NUM>), comprising
a feeding arrangement (<NUM>) having a planar shape comprising four feedable slots (<NUM>), which extend from a periphery towards a center of the planar shape of the feeding arrangement (<NUM>) and are arranged at regular angular intervals (<NUM>) of the planar shape forming a first angular arrangement, and four dipole arms (<NUM>), which extend from the feeding arrangement (<NUM>) outwards with respect to the center of the planar shape and are arranged at regular angular intervals (<NUM>) of the planar shape forming a second angular arrangement,
characterised in that
the second angular arrangement of the four dipole arms (<NUM>) is rotated (<NUM>) with respect to the first angular arrangement of the four slots (<NUM>),
wherein the feeding arrangement (<NUM>) comprises four transmission lines (<NUM>), each transmission line (<NUM>) crossing one of the four slots (<NUM>).