TECHNICAL FIELD

The present invention relates to an antenna for mobile communications, for instance to a multi-band antenna. The antenna is particularly a compact antenna with a controlled horizontal beam width (HBW), for instance with a 65° Horizontal 3dB beam width. The antenna has a plurality of radiating elements, which are arranged in at least two parallel columns.

BACKGROUND

With the current LTE-advanced deployments and looking forward to 5G, in order to fully exploit the capability of the new radio standards, there is a growing demand in the market to develop antennas that have more arrays per band and support new frequency bands as well.

The new architectures must support 4x4 and 8x8 MIMO (which is necessary in higher frequency bands, but is also wished for in lower frequency bands, so as to be ready for future deployments). This means that the number of ports/antenna arrays needs to be duplicated at least in the higher frequency bands.

However, in spite of such an increased number of bands and ports per band, the limitation of having only one antenna per antenna site/sector (or a maximum of two in some exceptional cases) is still a very strict requirement. It is not possible to add new“boxes” in an antenna site, because this would involve an increase of the site renting costs, and therefore operating costs for the operator. For similar reasons, it is also not possible to increase the dimensions of the antenna. In order to facilitate the site acquisition and/or be able to reuse current mechanical support structures in the sites, the width and therefore the wind-load of any new antennas should further be comparable to legacy products. Moreover, in spite of the strict limitations in the dimensions and numbers of antennas per sector, the RF performance of any new antenna should be equivalent to legacy products, in order to maintain (or even improve) the coverage area and network performance.

Currently, in order to support LTE TM9, it is becoming particularly important to develop antennas that can support 8T8R (i.e. 4 arrays side-by-side with dual polarization). In order to maintain the coverage area, it is also required to keep the traditional 65° Horizontal 3dB beam width requirement and, for the reasons already mentioned, the width of the antenna is very restricted. In practice, this means that the number of arrays has to be duplicated, while keeping the same RF performance and not increasing significantly the antenna aperture.

As a non-limiting example, compared to legacy products like 1 x 690-960 MHz + 2 x 1.7- 2.7 GHz (1L2H) in 350 mm (175 mm/HB column) or 1L3H to 370 mm (l23mm/HB column), there are new requirements for a 1L4H antenna architecture in a width of less than 400 mm (100 mm/HB column).

Accordingly, new techniques are required that allow controlling the HBW, e.g., to keep it stable around 65° HBW over a wide frequency band in a very limited aperture, while having very tightly coupled columns/arrays of radiating elements side-by-side.

A conventional approach combines radiating elements from different columns with the target of achieving a HBW reduction. This approach relies on having displaced radiating elements in the horizontal antenna direction. However, this approach does not increase the gain of the antenna, because the arrangement also generates unwanted sidelobes in non principal planes that limit the maximum gain that can be reached. In addition, these unwanted sidelobes in non-principal planes create interference with other cells, thus degrading system performance. In other words, while this approach works to reshape the pattern in the horizontal plane, it introduces other problems that can have an impact on the system performance, and can only be identified when looking at the antenna 3D pattern (not only at the principal planes, horizontal and vertical). Another conventional approach makes use of a resonant slot for an improved HBW control. However, while the position of the slot helps reducing the HBW at one frequency, it also generates a strong back radiation, degrading the antenna front- to-back ratio. To compensate this effect, a reflector has to be extended beyond the slots, but this is not possible for very strict width limitations.

SUMMARY

In view of the above-mentioned challenges and disadvantages, embodiments of the present invention aim to improve the conventional techniques. An objective is to provide an antenna for which the HBW is controlled, particularly in multi-column and/or tightly coupled arrays of radiating elements. The HBW of the antenna should specifically be kept stable, e.g., around 65° over a wide frequency band, for a case where several antenna arrays or columns of radiating elements are strongly coupled to each other and placed in a narrow antenna aperture.

The objective is achieved by embodiments of the invention as provided in the enclosed independent claims. Advantageous implementations of the embodiments of the invention are further defined in the dependent claims.

Generally, embodiments of the invention base on the arrangement of at least one electrically conductive separator (e.g., an electrical wall) with a certain shape between radiating elements in at least two columns. The radiating elements are arranged with a vertical shift between the at least two columns, which allow reusing free gaps for introducing the separator. To conform the pattern and adjust the HBW, the separator may have a determined, particularly meandering shape, between neighboring columns. Further, a shape and position of a resonating slot in the separator is proposed, which does not degrade the antenna front- to-back ratio and/or the column-to-column coupling.

A first aspect of the invention provides an antenna, comprising: a plurality of first radiating elements arranged in a first column, a plurality of second radiating elements arranged in a second column parallel to the first column, and an electrically conductive separator extending between the first radiating elements and the second radiating elements, wherein the separator is located: partly in one or more first gaps formed between at least some of the first radiating elements, each of the first gaps being located next to one of the second radiating elements, and partly in one or more second gaps formed between at least some of the second radiating elements, each of the second gaps being located next to one of the first radiating elements.

The separator may be an electrically conductive wall or fence. The outline of the separator may go around the radiating elements, thereby extending along the free gaps between the first and second radiating elements (in column direction). As a consequence, the aperture of the at least two columns in horizontal direction is increased, and the HBW is reduced. In other words, the separator helps to control the HBW in the multicolumn tightly coupled antenna. Notably, the at least two columns may form or be part of one array or different arrays of the antenna. In a typical implementation, each column of the at least two columns forms one array of the antenna.

In an implementation form of the first aspect, the separator is a meandering wall or fence.

The meandering shape of the separator provides a good increase of the horizontal antenna aperture, particularly of each column. Accordingly, an efficient control of the HBW is achieved.

In a further implementation form of the first aspect, the separator partially surrounds each of the first and second radiating elements.

In a further implementation form of the first aspect, the separator comprises one or more U-shaped or V-shaped or rounded segments, wherein each of the segments is located at least partly in one of the first gaps or in one of the second gaps.

In a further implementation form of the first aspect, the separator is discontinuous. For example, the separator may comprise a plurality of separator parts. For example, each of the separator parts may separate a first radiating element and two closest second radiating elements. Material cost and weight can thus be saved. In a further implementation form of the first aspect, the separator is continuous. The separator can thus be manufactured using simple methods, and a good isolating effect can be achieved.

According to the above implementation forms, the separator is not limited to a specific shape or continuity.

In a further implementation form of the first aspect, any two adjacent first radiating elements and any two adjacent second radiating elements are separated by a same spacing, and the first column is displaced with respect to the second column by an offset which is less than said spacing.

The first gaps are formed between adjacent first radiating elements. The second gaps are formed between adjacent second radiating elements. In this way, the separator can be placed located partly in the first and second gaps, respectively, in order to control the HBW of the antenna.

In a further implementation form of the first aspect, the offset is in the range of 0.4*S to 0.6*S, wherein S is said spacing.

The offset may notably be 0.5*S.

In a further implementation form of the first aspect, the separator comprises one or more slots.

The slot is in particular a resonating slot and further improves the HBW. In particular, slot can reduce the HBW.

In a further implementation form of the first aspect, each slot is placed on a part of the separator located in a first gap or in a second gap.

In this way, the slot improves, particularly reduces, the HBW, while it creates no problems with a front-to-back ratio of the antenna. In a further implementation form of the first aspect, each slot is placed such that the center of the slot does not cross any imaginary straight line connecting a first radiating element and a closest one of the second radiating elements.

As a consequence, the slot does not have a negative impact on the column-to-column coupling and front- to-back ratio.

In a further implementation form of the first aspect, a length of a slot is between 0.4 and 0.6 times the wavelength corresponding to a working frequency of the first and/or second radiating elements.

Accordingly, the maximum reduction of the HBW is achieved at that frequency.

In a further implementation form of the first aspect, the antenna further comprises: a plurality of third radiating elements arranged in a third column parallel to the second column, a further electrically conductive separator extending between the second radiating elements and the third radiating elements, wherein the further separator is located: partly in one or more third gaps formed between at least some of the third radiating elements, each of the third gaps being located next to one of the second radiating elements, and partly in one or more of the second gaps formed between at least some of the second radiating elements.

In a further implementation form of the first aspect, the first and second radiating elements are configured to radiate in a first frequency band and in a second frequency band, respectively, wherein the first frequency band and the second frequency band are identical or overlapping.

The first and second radiating elements in the at least two columns may form or be part of the same array or a different array of the antenna.

In a further implementation form of the first aspect, the antenna further comprises: one or more further radiating elements configured to work in a different frequency band than the first and/or second radiating elements. Accordingly, the antenna have further antenna arrays. The solution of the invention is compatible also with complex antenna architectures, particularly multiband antenna architectures.

A second aspect of the invention provides a base station comprising an antenna according to the first aspect or any one of the implementation forms of the first aspect, and a radio transmitter connected to the antenna

The base station of the second aspect enjoys all advantages and effects of the antenna of the first aspect. The application of the antenna is, however, not limited to a base station.

A base station may also be referred to in the art as a network access node, a radio client device, an access client device, an access point, e.g., a Radio Base Station (RBS), which in some networks may be referred to as transmitter,“gNB”,“gNodeB”,“eNB”,“eNodeB”, “NodeB” or“B node”, depending on the technology and terminology used. The radio client devices may be of different classes such as macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. The radio client device can, for example, be a Station (STA), which is any device that contains an IEEE 802.11- conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The radio client device may also be a base station corresponding to the fifth generation (5G) wireless systems.

It has to be noted that all devices, elements, units and means described in the present application could be implemented in the software or hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof. BRIEF DESCRIPTION OF DRAWINGS

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

FIG. 1 shows an antenna according to an embodiment of the invention.

FIG. 2 shows an antenna according to an embodiment of the invention.

FIG. 3 shows an antenna according to an embodiment of the invention.

FIG. 4 shows an antenna according to an embodiment of the invention.

FIG. 5 shows an exemplary antenna.

FIG. 6 shows an antenna according to an embodiment of the invention.

FIG. 7 shows an exemplary antenna.

FIG. 8 shows an antenna according to an embodiment of the invention.

FIG. 9 shows an antenna according to an embodiment of the invention.

FIG. 10 shows an antenna according to an embodiment of the invention.

FIG. 11 shows an antenna according to an embodiment of the invention.

FIG. 12 shows an antenna according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Illustrative embodiments of antenna, and apparatus are described with reference to the figures. Although this description provides examples of possible implementations, it should be noted that the details are intended to be exemplary and in no way limit the scope of the present application.

FIG. 1 shows an antenna 100 according to an embodiment of the invention. The antenna 100 includes, as an example, radiating elements arranged in two columns. In particular, a plurality of first radiating elements lOle are arranged in a first column 101, and a plurality of second radiating elements l02e are arranged in a second column 102 parallel to the first column 101. The antenna 100 may include more columns and/or more (different) radiating elements than the ones arranged in the first and second columns 101, 102 shown in FIG. 1.

First gaps lOlg are formed between the first radiating elements lOle, and second gaps l02g are formed between the second radiating elements l02e. The columns 101 and 102 are arranged such that each of the first gaps lOlg is located next to one of the second radiating elements l02e, and each of the second gaps l02g is located next to one of the first radiating elements lOle. For instance, this can be realized by separating any two adjacent first radiating elements lOle and any two adjacent second radiating elements l02e by a same spacing, and arranging the first column 101 is displaced with respect to the second column 102, particularly by an offset which is less than said spacing.

The first and second radiating elements lOle, l02e may be configured to radiate in a first frequency band and in a second frequency band, respectively, wherein the first frequency band and the second frequency band may be identical or overlapping. That is, the first and second columns 101 and 102 may be part of or form one or more arrays of the antenna 100. Thus, the antenna 100 may be a multiband antenna. Notably, it is also possible that the first radiating elements lOle and second radiating elements l02e are configured to radiate in non-overlapping frequency bands. The antenna 100 may be part of an apparatus, for example, a base station, wherein it may be connected to a radio transmitter of the apparatus (e.g., base station).

As can be seen in FIG. 1, the antenna 100 further comprises an electrically conductive separator 103, which may be shaped as a wall or fence or the like. The separator 103 extends between the first radiating elements lOle and the second radiating elements l02e, particularly in the same direction as the columns. This may be regarded as the vertical direction of the antenna 100, especially with respect to the HBW of the antenna 100. The separator 103 is located partly in one or more first gaps lOlg formed between at least some of the first radiating elements lOle, and partly in one or more second gaps formed between at least some of the second radiating elements l02e. As shown exemplarily in FIG. 1, the separator 103 may be located partly in the first gaps lOlg formed between all of the first radiating elements lOle, i.e. all first gaps lOlg, and partly in second gaps l02g formed between all of the second radiating elements l02e, i.e. all second gaps l02g. Accordingly, the separator 103 may be a meandering separator, e.g., meandering wall or fence, i.e. with a meandering shape, and/or the separator 103 may partially surround each of the first and second radiating elements lOle, l02e, i.e. may extend partially around these elements lOle, l02e.

FIG. 2 shows an antenna 100 according to an embodiment of the invention, which builds on the antenna 100 shown in FIG. 1. Same elements in FIG. 1 and FIG. 2 have identical reference signs and function likewise. The antenna 100 shown in FIG. 2 includes further a third column 201 of radiating elements 20 le. That is, a plurality of the third radiating elements 20 le are arranged in the third column 201 parallel to the second column 102 (and first column 101). The third column 201 is next to the second column 102, i.e. the second column 102 is in between the first column 101 and third column 201. Third gaps 20lg are formed between the third radiating elements 20 le, wherein each of the third gaps 20 lg is located next to one of the second radiating elements 102.

The antenna 100 of FIG. 2 comprises a further electrically conductive separator 203, which extends between the second radiating elements l02e and the third radiating elements 20 le, particularly in the same direction as the columns. The further separator 203 is located partly in one or more third gaps 20 lg formed between at least some third radiating elements 20 le, and partly in one or more of the second gaps formed between at least some of the second radiating elements l02e. Like the first separator 103, also the further separator 203 may be a wall or fence, particularly with a meandering shape.

The separator 103, 203 placement can in principle be used for any bi-dimensional antenna 100, but for practical implementations it has been found to be very effective to control particularly the HBW of a 1L4H antenna architecture, as exemplarily depicted in FIG. 3 (in a top view) and in FIG. 4 (in a perspective view). The total width of this antenna may be less than 400 mm, so less than 100 mm may be available for each HB array. In the antenna 100 of FIG. 3 and FIG. 4, the columns 101 and 102 are shifted against each other (in the vertical direction of the antenna 100), so as to arrange the first gaps lOlg and the second gaps l02g, respectively, next to the second radiating elements l02e and first radiating elements lOle. Further, the separator 103, here having an optimized meandering shape, is located between the first and second radiating elements lOle, l02e. Additional columns 301 and 302 are provided in the antenna 100. In particular, third radiating elements 30 le are arranged in a third column 301 parallel to the first and second columns 101, 102. In addition, fourth radiating elements 302e are arranged in a fourth column 302 parallel to the other columns 101, 102, 301. Third gaps 30lg are formed between the third radiating elements 30 le, and fourth gaps 302g are formed between the fourth radiating elements 302e. The third gaps 30 lg are arranged next to fourth radiating elements 302e, and the fourth gaps 302g are arranged next to the third radiating elements 30 lg. Further, a further separator 303, here with an optimized meandering shape, is added between the third and fourth radiating elements 30 le, 302e.

In addition, one or more further radiating elements 304e and/or 305e may be included in the antenna 100, for instance, to provide additional radiating frequency bands. For example, as shown in FIG. 3, first further radiating elements 304e may be arranged in a column 304, wherein said column 304 is placed into the second column 102, i.e. the said column 304 and the second column 102 are interleaved. Accordingly, further radiating elements 304e are arranged between some adjacent second radiating elements l02e. Likewise, second further radiating elements 305e may be arranged in another column 305, wherein said column 305 is placed into the fourth column 302, i.e. said column 305 and the fourth column 302 are interleaved. Accordingly, further radiating elements 305e are arranged between some adjacent fourth radiating elements 302e. The first further radiating elements 304e of the column 304 and the second further radiating elements 305e of the column 305 may be placed such that the columns 304 and 305 are shifted against each other along the column direction (vertically). In the above-described way, a compact multiband antenna 100 with improved HBW can be realized.

The width of the aperture for each of the individual columns 101, 102, 301, 302 (i.e. the surface that the respective radiating elements illuminate) can be increased, the radiation pattern can be correctly conformed, and as a consequence the HBW can be decreased while the gain can be increased. Notably, without the separators 103, 303, the coupling between the columns 101, 102, 301 and 302 would be very high, and the radiation would not be conformed correctly.

In the vertical direction of the antenna 100 (i.e. along the columns 101, 102, 301, 302), the pattern is mainly dominated by the array factor, so even if the unitary vertical pattern is impacted by the presence of the separators 103, 303, the impact on the vertical pattern overall can be neglected.

FIG. 5 shows an exemplary antenna not according to an embodiment of the invention, particularly since it shows how an equivalent aperture would look like without using separators 103 and 303. The resulting equivalent aperture for each column is shown alternatively in white and black color. In particular, counting from top to bottom, for columns 1 and 3 the equivalent aperture is filled with black color, and for columns 2 and 4, the equivalent aperture is filled with white color. FIG. 6 shows in comparison an antenna 100 according to an embodiment of the invention, which builds on the antenna 100 shown in FIG. 3 and FIG. 4 and this includes separators 103 and 303. Again the equivalent aperture for each column 101, 102, 301, 302 is filled alternatively in white and black color. Counting from top to bottom, for the first column 101 and the third column 301, the equivalent aperture is filled with black color, and for the second column 102 and the fourth column

302, the equivalent aperture is filled with white color.

Looking at FIG. 6 in comparison to FIG. 5, it is easy to understand that the surface that each radiating element lOle, l02e, 30le, 302e illuminates in a horizontal direction of the antenna 100 (compared to the vertical direction of the antenna 100, in which the columns 101, 201, 301, 302 are arranged) increases significantly after adding the separators 103 and

303.

In addition to the separator 103 and/or 203 and/or 303 in the above described antennas 100 according to embodiments of the invention, one or more resonant slots may be added to the separator 103, 203, and/or 303, in order to further improve the HBW at least at a certain frequency. Placing resonant slots in side walls is a conventional technique to reduce HBW. However, conventionally, the slots create problems with front-to-back ratio (FBR), of an antenna, when placed in the outer side, or problems with coupling between columns of radiating elements, when placed in inner side. FIG. 7 shows an exemplary antenna, in which slots are placed as conventionally.

FIG. 8 shows an antenna according to an embodiment of the invention, which bases on the antenna 100 shown in FIG. 1, FIG. 3 and FIG. 4. Same elements in these figures are labelled with the same reference signs and function likewise. The antenna 100 of FIG. 8 includes at least the separator 103 between the first radiating elements lOle and the second radiating elements l02e. A resonant slot 800 is placed in a determined location of the separator 103, in order to achieve a positive impact on the HBW and radiation pattern, but without having a negative impact on column-to-column coupling and front-to-back ratio, respectively. The separator 103 may particularly comprise one or more slots 800. Each of the one or more slots 800 is particularly placed such on the separator 103 that it does not cross any imaginary straight line connecting a first radiating element lOle and a closest one of the second radiating elements l02e (i.e. closest to said first radiating element lOle).

In other words, the slot 800 is particularly not placed directly in the outer edge of the reflector, which mitigates potential front-to-back radiation issues. In addition, the slot 800 is not placed such that the center of the slot is crossing an imaginary line connecting two radiating elements lOle, l02e of different columns 101, 102, which mitigates the column- to-column coupling issue. Conventionally (as shown in FIG. 7) a slot is placed either in the outer edge (what creates the FBR issues) or such that the center of the slot is crossing an imaginary line connecting two elements from different columns when placed in the inner side (which creates coupling issues).

For a better understanding of the antenna 100 shown in FIG. 8, in FIG. 9 an exemplary antenna and in FIG. 10 an antenna 100 according to an embodiment of the invention are depicted in a 3D view. It is specifically show how the slot 800 looks like conventionally (shown in FIG. 9) and according to embodiments of the invention (shown in FIG. 10). The total length of a slot 800 in the antenna 100 may be approximately half-wavelength at the frequency, where maximum reduction in the HBW is to be achieved. For instance, a length of the slot 800 may be between 0.4 and 0.6 times the wavelength corresponding to a working frequency of the first and/or second radiating elements lOle, l02e, particularly 0.5 times. The antennas 100 according to embodiments of the invention are not limited to any specific shape of the separator 103 (and/or 203 and/or 303), in particular not the meandering shape of the e.g., wall or fence. That is, the separator 103 may have straight, chamfered or rounded comers, wherein the number of bends is not fixed, and the separator 103 can be continuous or discontinuous. The only requirement is that it should prolong along the free gaps lOlg, l02g between the radiating elements lOle, l02e of the adjacent columns 101, 102 in a vertical direction (i.e. along the columns). That is, that it is at least partly located in some of each gaps lOlg, l02g. For instance, the separator 103 may comprise one or more U-shaped or V-shaped or rounded segments, wherein each of the segments is located at least partly in one of the first gaps lOlg or in one of the second gaps l02g. FIG. 10 notably shows a separator 103 with U-shape segments 900.

FIG. 11 and FIG. 12 show each an antenna 100 according to an embodiment of the invention. The antennas 100 of FIG. 11 and FIG. 12 are two additional examples with a different shape of the separator 103 (for reducing a number of bends) and with a discontinuous separator 103, respectively. Again these are merely two additional examples with illustrative purpose, and other possible implementations can be derived from them. FIG. 11 particularly shows an antenna 100 with a separator 103 having V-shaped segments 1000. FIG. 12 shows an antenna 100 with a discontinuous separator 103 having particularly separated U-shaped segments 1100.

The present invention has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed invention, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word“comprising” does not exclude other elements or steps and the indefinite article“a” or“an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.