Dual-polarized radiating element and antenna

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

TECHNICAL FIELD

The present invention relates to a dual-polarized radiating element for an antenna, i.e. to a radiating element configured to emit radiation of two different polarizations. The present invention relates further to an antenna, specifically to a multiband antenna comprising at least one dual-polarized radiating element, and preferably one or more other radiating elements, more preferably other radiating elements forming a massive Multiple Input Multiple Output (mMIMO) array.

BACKGROUND

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 4×4 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 6 GHz. 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 4×4 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.

SUMMARY

In view of the above-mentioned challenges and disadvantages, the present disclosure describes improved conventional radiating elements and conventional multiband antennas. In particular, the present disclosure provides 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 30%. Low profile means that the antenna height is smaller than 0.15λ, wherein λ is the wavelength at the lowest frequency of the frequency band of the operating radiating element.

The present disclosure describes 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 disclosure provides a dual-polarized radiating element, comprising a feeding arrangement comprising four 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 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 90° intervals, and the second angular arrangement of the four dipole arms is rotated by 45° with respect to the first angular arrangement of the four slots. The mentioned intervals can include a manufacturing tolerance interval e.g. ±5 degrees or even only ±2 degrees.

The radiating element can thus be arranged on an antenna such that its two emitted radiation polarizations are rotated by 45° 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 90° 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, 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.

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 disclosure 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 45° with respect to the longitudinal axis of the antenna.

Thus, 45° 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.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1shows a dual-polarized radiating element100according to an embodiment of the present invention. The radiating element100comprises a feeding arrangement101, and four dipole arms103. It further exhibits a specific angular arrangement of its components.

The feeding arrangement101comprises four slots102, which extend from a periphery towards a center of the feeding arrangement101, and which are arranged at regular angular intervals104, which forms a first angular arrangement. In particular, two adjacent slots102in the first angular arrangement are arranged with an angle α in between. Further, each of the slots102extends from the periphery of the feeding arrangement101to a center portion of the feeding arrangement101, preferably in a radial manner.

The four dipole arms103extend outwards from the feeding arrangement101, and are arranged at regular angular intervals105, which forms a second angular arrangement. In particular, two adjacent dipole arms103in the second angular arrangement are arranged with an angle θ in between. A dipole arm103is a structural element extending from the feeding arrangement101, with a length in extension direction that is larger than its width. Preferably, each of the dipole arms103has further a width that is smaller than the width of the feeding arrangement101side, from which it extends.

The second angular arrangement of the four dipole arms103is rotated106with respect to the first angular arrangement of the four slots102, particularly by an angle Φ106.

FIG. 2shows another radiating element100according to an embodiment of the present invention, which builds on the radiating element100shown inFIG. 1. Identical elements in these twoFIGS. 1 and 2are provided with the same reference signs.

In particular, the radiating element100ofFIG. 2has the four slots102and four dipole arms103, which are here respectively arranged at 90° intervals each. Further, the angular arrangements of the dipole arms103and the slots102are here rotated with respect to each other by 45°. Accordingly, the radiating element100extends with its dipole arms103mainly in two perpendicular directions (referred to as vertical and horizontal directions, respectively), but the polarizations of the radiating element100will lie at ±45° to these horizontal and vertical directions.FIG. 2specifically shows that adjacently arranged slots102extend perpendicular to another, and that non-adjacently arranged slots102extend in line with another in this radiating element100. Thus, two in line extending slot pairs are defined.

The two in line extending slot pairs define the two ±45° orthogonal polarizations of the dual-polarized radiating element100, when it is operated. To this end, the radiating element100is fed in operation preferably like a conventional square dipole, whereby the four slots102of the feeding arrangement101are particularly fed symmetrically 2-by-2.

FIG. 2also shows that each of the four slots102ends in a symmetrically bent, more or less U-shaped slot201. The purpose of the four slots201is to extend the total length of each of the four slots102, particularly for impedance matching purposes. Since the length of the four slots102cannot be extended further to a center portion of the feeding arrangement101(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 slot201preferably have the same pattern at both sides of a slot102. This leads to the symmetrically bent slots201, preferably the shown U-shaped ones.

The feeding arrangement101shown inFIG. 2comprises a PCB205, and the four dipole arms102are soldered to the PCB205through soldering pins206. The soldering pins206cross the PCB205from bottom to top. Capacitive coupling between the four dipole arms102, and to the PCB205, 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 arms102and the PCB205is small and stable.

Preferably, the dipole arms102do not extend only horizontally and vertically, but—as shown inFIG. 2—also in the third perpendicular dimension, i.e. along a z-axis. In other words, at least a part203of each dipole arm102preferably extends upwards and/or downwards with respect to the feeding arrangement plane in which the feeding arrangement is arranged101. InFIG. 2, each dipole arm103extends upwards in a part203. By extending in the z-axis, the dipole arms102can 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 element100does not need to be increased. This is explained below with respect toFIG. 4.

As further shown inFIG. 2, the dipole arms102are preferably terminated with flaps204, which make the dipole arms102again electrically longer, without increasing their footprint. Preferably, as shown inFIG. 2, the flaps204are bent downwards. However, it is also possible to have upwards or downwards bent flaps204, and even a bending of flaps204back towards the feeding arrangement101is possible. Examples of alternative flaps204will be provided with respect to other figures further below. Also described further below is an optional support800for the radiating element100.

FIG. 3shows a comparison of simulations of a current-density plot in a radiating element100(left side) according toFIG. 2, and in a conventional square-shaped radiating element300(right side). In the conventional radiating element300, most of the current is concentrated in slots302of a feeding arrangement301, whereas in the radiating element100the 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 ±45° polarizations. This advantageously allows to maximize the surface efficiency of the radiating element100, which means that practically the whole surface of the radiating element100, i.e. both of the feeding arrangement101and the dipole arms103, contributes to the radiation. The amount of metallic surface is thus optimized. In the conventional square-shaped radiating element300, 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 element100, the feeding of the slots102is, 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 element100has broadband characteristics, but at the same time a very small footprint.

FIG. 4shows another radiating element100according to an embodiment of the present invention. The radiating element100ofFIG. 4builds on the radiating element100shown inFIG. 3. Identical elements in these twoFIGS. 3 and 4are provided with the same reference signs.FIG. 4shows a radiating element100that further comprises a parasitic director401, which is preferably arranged above the feeding arrangement101. The parasitic director401further helps to achieve the required bandwidth, and at the same time to minimize the dimensions of the radiating element100.

FIG. 5shows a side view of the radiating element100that is shown inFIG. 4. InFIG. 5, it shows that preferably the parasitic director401extends outwards from the feeding arrangement101less than each one of the four dipole arms103. Thus, the parasitic director401does not increase the width and length of the radiating element100in the horizontal and vertical directions, respectively. Further, additionally or optionally, each dipole arm103may comprise, as shown inFIG. 5, an outer part203that extends upwards with respect to the feeding arrangement plane. Then, the parasitic director401is preferably arranged in a recess501, which is defined within the four outer parts203. Thus, the parasitic director401does also not increase the height of the radiating element100. Further, as mentioned above, the dipole arms103are extended electrically in length due to the parts203, however, preferably not above the above plane of the parasitic director401. The height of the radiating element100ofFIG. 4is, for example assuming an operating frequency band of 690-960 MHz, about 65 mm. That means, the height of the radiating element100is about 0.15λ at 690 MHz, and even below 0.15λ at 960 MHz, wherein λ is the wavelength corresponding to the respective frequencies. That is, it is a low profile radiating element100.

FIG. 6shows another radiating element100according to an embodiment of the present invention in a bottom view. Elements shown inFIG. 6and identical elements in the previous figures, are provided with the same reference signs. The PCB205carrying the feeding arrangement101and the slots102,201is visualized transparent inFIG. 6, so that the crossings between the (feeding) transmission lines601and the slots102can be easily seen.

FIG. 6shows that the feeding arrangement101preferably further comprises four transmission lines601, wherein each transmission line601crosses one of the four slots102. The transmission lines601are preferably short-ended microstrip lines. The transmission lines601are particularly used for feeding the four slots102, and are combined, in order to feed two non-adjacent slots102in an identical manner. This leads to the dual polarization of the radiating element100. InFIG. 6, the combination of the four transmission lines601into two transmission lines602is carried out on a PCB arrangement603. In particular, this PCB arrangement603extends from a bottom surface of the feeding arrangement101. The PCB arrangement603may specifically extend orthogonally from the feeding arrangement101. Because the four transmission lines601are combined into the two transmission lines602, firstly a feeding signal can be transmitted from the PCB arrangement603to, for example, a PCB205of the feeding arrangement101, and secondly the radiating element100can be grounded.

For instance, a ground of the PCB arrangement603may be connected (e.g. soldered) to a ground of the feeding arrangement101. The PCB arrangement603may also be connected to an additional PCB, which serves, for instance, as a transition between the radiating element100and 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. 7shows another radiating element100according to an embodiment of the present invention, in which the transmission lines601are combined into transmission lines702in a different manner than inFIG. 6. Nevertheless, identical elements in the twoFIGS. 6 and 7are provided with the same reference signs. In particular, inFIG. 7the combination of the four transmission lines601into two transmission lines702is carried out on the feeding arrangement101, particularly, on the PCB205of the feeding arrangement101. 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 PCB205can be divided into four small slots, which offers advantages in terms of isolation between different frequency bands.

FIG. 8shows a dielectric support800, onto which the radiating element100according to an embodiment of the present invention can be mounted. This is also indicated in the previous figures showing the radiating elements100. The dielectric support800advantageously ensures mechanical stability of the radiating element100, and ensures that a distance from the radiating element100to an antenna reflector, as well as a distance from a parasitic director401to the radiating element100, is stably maintained. The dielectric support800may specifically comprise support feet804, which also define a distance of the radiating element100to, for example, a feeding network or to the antenna reflector. Further, the support800can include support elements802, in order to stably support the four dipole arms102of the radiating element100. The support800can also comprise attachment means803, which are configured to hold the feeding arrangement101, and preferably the parasitic director401.

FIG. 9shows a radiating element100according to an embodiment of the present invention. Elements inFIG. 9and identical elements in the previous figures, are provided with the same reference signs. InFIG. 9the feeding arrangement101of the radiating element100is made out of one single bent metal sheet together with the dipole arms103, instead of comprising a PCB205and the four dipole arms103attached thereto. In particular, the feeding arrangement101comprises a metal sheet901, wherein the four slots102are preferably cutouts in the metal sheet901, and also the four dipole arms103are formed by the metal sheet901. This has, for example, the advantage that the metal sheet901can be easily designed with four further flaps902, which may be arranged in between the four dipole arms102. The further flaps902may be bent upwards or downwards with respect to the feeding arrangement plane. Furthermore, the slots102may further extend along the flaps902. Thereby, the extending slots102may actually divide each of the four flaps902into to two sub-flaps, as it is shown inFIG. 9. By means of the flaps902, the slots102can be either be electrically extended without changing the size of the feeding arrangement101, or the size of the feeding arrangement101can be reduced without reducing the length of the slots102. InFIG. 9, the flaps902are bent downwards, and furthermore slightly back towards the feeding arrangement101. However, the flaps902could 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 element100. Further, as shown inFIG. 9, also the dipole arms103can have additional bends, for instance, side flaps903for increasing the electrical width of the dipole arm102. The side flaps903may be formed by bending the dipole arms103along their extension direction. The slots102can be fed by transmission lines on a PCB e.g. arranged below the metal sheet901. In a further embodiment the slots102may be fed using a suitable cable feed e.g. arranged below the metal sheet901.

FIG. 10shows yet another radiating element100according to an embodiment of the present invention, which builds for instance on the radiating element100shown inFIG. 2. Identical elements in these twoFIGS. 2 and 10are provided with the same reference signs. InFIG. 10, the flaps204terminating the dipole arms103are not only bent downwards, but also back towards the feeding arrangement101. This provides further electrical length to the dipole arms103. Further, the optional parasitic capacitor401is shown to be arranged above the feeding arrangement101, and particularly within the extension length of the four dipole arms103.

FIG. 11shows another radiating element100according to an embodiment of the present invention, which builds on the radiating element100shown inFIG. 1. Identical elements in these twoFIGS. 1 and 11are provided with the same reference signs. Here, inFIG. 11, the dipole arms103extend outwards from the feeding arrangement101and are terminated by upward bent flaps204, respectively, for increasing their electrical length. Also, the optional PCB arrangement603extending from the feeding arrangement101is shown. The PCB arrangement603may serve also as mechanical support, for instance, instead of the support800.

Notably, with respect to the above-described radiating elements100, the decision of whether terminating flaps204of the dipole arms103are bent upwards or downwards can be decided after a detailed optimization process of the radiating element100. The decision can, for instance, depend on the arrangement of the radiating element100on an antenna, particularly together with other radiating elements arranged side-by-side the radiating element100.

FIGS. 12 and 13show RF performance of the radiating element100according to an embodiment of the present invention. Specifically, the Voltage Standing Wave Ratio (VSWR) and the radiation pattern of the radiating element100are shown.FIG. 12specifically shows that the VSWR is below 16.5 dB (1.35:1) from 690-960 MHz.FIG. 13shows that the radiation pattern is symmetric, the 3 dB beamwidth is around 65 degree and the Cross-polar discrimination is above 10 dB in the range from +60 to −60 degree.

FIG. 14shows, how the radiating element100according to an embodiment of the present invention can advantageously be arranged in a multiband antenna architecture. At both sides of the radiating element100, there are provided other radiating elements1400, for instance, configured to work in a higher frequency band like in HB arrays. Due to the shape of the radiating element100, a distance between the other radiating elements1400on either side of the radiating element100can be minimized, namely by arranging the other radiating elements1400nested with the dipole arms103that extend from the feeding arrangement101of the radiating element100. 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. 15shows in this respect an antenna1500according to an embodiment of the present invention. The antenna1500comprises three columns of radiating elements, each column extending along a longitudinal axis1501of the antenna1500. In particular, the radiating elements100are arranged in a first column1504, which is located in between and side-by-side two second columns1503comprising the other radiating elements1400. Preferably, the second columns1503are HB arrays, and the first column1504is an LB array.FIG. 15again shows, how two of the dipole arms103of each radiating element100extend between two of the other radiating elements1400in the HB arrays, i.e. they extend along a lateral axis1502of the antenna1500. The other two dipole arms103of each radiating element100extend along the longitudinal axis1501of the antenna1500. This allows a very dense packing of the respective HB and LB arrays. However, as also desired, the radiation polarizations defined by the slots102of the radiating elements100are still ±45° with respect to the longitudinal axis1501of the antenna1500.

FIG. 16shows another radiating element100according to an embodiment of the present invention, which builds on the radiating element100shown inFIG. 1. Identical elements in these twoFIGS. 1 and 11are provided with the same reference signs. Here, inFIG. 16, the radiating element comprises four further flaps1600extending from the feeding arrangement101. In particular, the four flaps1600are connected to a PCB205, and are preferably bent upwards with respect to the feeding arrangement plane. The four flaps1600are arranged in between the four dipole arms103, respectively. Each one of the four slots102further extends along the flaps1600, that means, it is electrically extended on one of the four flaps1600. Thereby, each flap1600may be formed by two sub-flaps1601creating one slot extension, as it is shown inFIG. 16. Accordingly, the radiating element1600comprises in this case eight sub-flaps1601.

The radiating element100shown inFIG. 16is particularly advantageous for integrating an array of many such radiating elements100with another array of other radiating elements1400, for instance with a mMIMO array. This is due to the fact that the shown modifications of the radiating element100improve the isolation and squint of closely spaced mMIMO radiating elements1400in such a mMIMO array. For instance, the size of the PCB205can be reduced without sacrificing length of the slots102, which is enabled by the flaps1600allowing to electrically extend the slots102. The flaps1600are preferably folded upwards, in order to minimize the squint of the lower-lying mMIMO array.

Furthermore, the size of the parasitic director401may also be minimized to minimize the radiating element100as a whole. Any loss of bandwidth that results from this size decrease of the parasitic director401can preferably be compensated by increasing at the same time the height of the radiating element100. Additionally, in contrast to the parasitic director401shown inFIG. 4, 10 or 11, the shape of the parasitic director401may be changed. The parasitic director401shown inFIG. 16does not have any flaps or arms extending from its central part. Preferably, the parasitic director401has an octagonal shape as it is shown inFIG. 16. Preferably, four sides of the octagonal parasitic director401are arranged at the same positions and at the same angular intervals of the second angular arrangement formed by the dipole arms103. Preferably, the other four sides of the octagonal parasitic director401are arranged at the same positions and at the same angular intervals of the first angular arrangement formed by the four slots102. Alternatively, however, the director401may also have a round shape, or a shape with more than eight sides.

The radiating element100ofFIG. 16can be further optimized for integration with a mMIMO array by having preferably dipole arms103that are folded downwardly. That is, at least a part204of each dipole arm103extends downwards with respect to the feeding arrangement plane. Optionally, the dipole arms103are further bent back towards the feeding arrangement101.

FIG. 17shows the radiating element100ofFIG. 16in a top view. The first and second angular intervals105and106of the four slots102and the four dipole arms103, respectively, are shown, and the above-described preferred shape and orientation of the preferred octagonal parasitic director401is illustrated.

FIG. 18shows a radiating element according to an embodiment of the present invention, which builds on the radiating element100shown inFIG. 16. The radiating element100inFIG. 18is shown without a parasitic director401. The four slots102can thus be seen well, here they are provided on the PCB205, and it can be seen how they extend onto the four flaps1600. It can also be seen that each flap1600is preferably soldered with two soldering points206to the PCB205. In particular, in case of the flaps1600being formed by sub-flaps1601creating the slot extensions, each sub-flap1601is preferably soldered with one soldering point206to the PCB205as shown inFIG. 18. Further, each dipole arm103is preferably soldered with one soldering point206to the PCB205. These soldering points206improve the mechanical stability of the radiating element100and also electrical continuity is provided.

FIG. 19shows exemplary parts of a radiating element100according to an embodiment of the present invention, for instance, parts of the radiating element100ofFIG. 18. Here inFIG. 19, each one of the four flaps1600is formed by two-sub flaps1601. Further, the four dipole arms103and the four flaps1600are formed by four separate integral elements1900. Each integral element is formed by one dipole arm103and two (opposing) sub-flaps1601, particularly with one sub-flap1601being arranged on either side of the dipole arm103. For instance, two metallic sub-flaps1601with a metallic dipole arm103in-between them may form one integral element1900. The four integral elements1900are arranged such in the radiating element100that their diploe arms103are arranged at the regular intervals105forming the second angular arrangement, preferably that their dipole arms103are arranged at 90° intervals. Further, the four integral elements1900are arranged such in the radiating element100that two sub-flaps1601of two adjacent integral elements1900form one flap1600and accordingly create an extension for one of the four slots102. Such a particular arrangement of integral elements1900is shown inFIG. 19.

The four integral elements1900improve further the mechanical stability of the radiating element100. Each integral element1900is preferably soldered at its dipole arm103with one soldering point206to the PCB205, and at each of its two sub-flaps1601with one soldering point206to the PCB205for the best mechanical stability. However, it is also possible to form the four dipole arms103and the four flaps1600, respectively, in a different manner. In particular, two sub-flaps1601forming one flap1600need not necessarily belong to two separate integral elements1900, but could be formed by a single integral piece, like the flaps902shown inFIG. 9.

FIG. 20shows a radiating element100according to an embodiment of the present invention, which builds on the radiating element shown inFIG. 16. The further flaps1600and the extensions of the slots102on each of these flaps1600are well visible. Further, it can be seen that a PCB arrangement603may extend from the bottom surface of the feeding arrangement101, particularly from the PCB205. On the PCB arrangement603preferably four transmission lines601that are coming from the PCB205are combined into two transmission lines602.

FIG. 21shows a radiating element100according to an embodiment of the present invention, which builds on the radiating element100ofFIG. 16, and is working in a multiband antenna architecture. The radiating element100is arranged such that its dipole arms103extend between the other radiating elements1400that are arranged in at least two columns. Preferably, these other radiating elements1400form a mMIMO array. It can be seen that due to the fact that the radiating elements100comprises the upwards bent flaps1600, wherein the flaps1600electrically extend each of the four slots102, the form factor of the radiating elements100can be made much smaller. Therefore, the other radiating elements1400are less shadowed. Accordingly, the squint of the mMIMO array and its radiating elements is minimized.

FIG. 22shows a radiating element100according to an embodiment of the present invention working in a multiband antenna architecture with other radiating elements1400. For purposes of illustration, a conventional, disc-shaped radiating element2200is shown in comparison to the radiating element100, as it would be arranged if integrated with the array of other radiating elements1400. It can be seen that the radiating element100, due to its small footprint and its smarter space filling, results in a much lower shadowing effect on the other radiating elements1400than the conventional radiating element2200.

FIG. 23shows a plurality of radiating elements100according to embodiments of the present invention working in a multiband antenna architecture integrated with a mMIMO array. The radiating elements100are preferably arranged in at least one column along the longitudinal axis1501or direction of the antenna1500. In case of more than one column, these columns are separated along the lateral axis1502or direction of the antenna1500. The other radiating elements1400form the mMIMO array, which preferably includes the other radiating elements1400arranged in a plurality of columns. The radiating elements100may be arranged in gaps or in increased radiating element spacings or in vacant positions created by left-out radiating elements100in these columns, respectively. The radiating elements100are thus preferably interleaved with the plurality of other radiating elements1400. Thereby, different types and/or sizes of dual-polarized radiating elements100can 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 element100is made low profile, but is at the same time provided with broadband characteristics. Furthermore, that and how the radiating element100has a shape that minimizes interference with other radiating elements1400arranged side-by-side in a multiband antenna1500, and minimizes the width of the antenna1500.