TECHNICAL FIELD

The present invention relates to relates to the technical field of antennas, in particular antennas for mobile communication. The invention accordingly presents an antenna, which is for example configured for massive Multiple Input Multiple Output (MEMO). The invention also presents a dual-polarized antenna element to be used in such an antenna.

BACKGROUND

With the growing demand for a deeper integration of antennas with radios, e.g. in Active Antenna Systems (AAS), new low-profile antennas with an extended bandwidth are requested, without compromising certain antenna Key Performance Indicators (KPIs). A deeper antenna integration leads to more complex systems, and strongly influences/limits the antenna form factor, which is fundamental for commercial field deployment of the antennas. In this context, one of the dominant limiting technological factors is the feeding complexity of the antennas, since the antennas need to be integrated with other active/passive components.

Simplifying the structure of antenna elements (wherein one or more antenna elements may form an antenna), and reducing the number of antenna element parts, would greatly facilitate the antenna assembly, and would reduce the cost of the antenna system, e.g. the AAS. To cover at the same time the standard operating bands in modem antenna systems, while also maintaining the same RF performance with antenna elements that can be easily integrated with other components, new concepts/architectures different from the legacy technology are required. Wideband and low-profile dual-polarized antenna elements are important for designing future antenna systems. In particular, slot-fed dual-polarized antenna elements offer many advantages. Conventional concepts for such slot-fed dual-polarized antenna elements exist, however, the conventional concepts are either costly, require too many parts, i.e. lead to complex structures, or are incompatible with the desired antenna KPIs. FIG. 8 shows an exemplary a dual-polarized antenna element 800. The antenna element 800 includes a patch radiating element 804 with a director 803 arranged above it. Further, the antenna element 800 includes an antenna reflector 805 arranged beneath the patch radiating element 804, and a stripline Printed Circuit Board (PCB) 801 arranged beneath the antenna reflector 805. The antenna element 800 may also include electromagnetic (EM) walls 802 surrounding the patch radiating element 804. Feeding slots for the patch radiating element 804 and transmission (RF) lines are integrated into the PCB 801.

A disadvantage of this antenna element 800 is that the EM walls 802 are an additional structure. Further, that the cavity for the patch radiating element 804 is realized with a dual layer PCB 80 E Thus, the antenna element 800 is rather expensive and complex.

SUMMARY

In view of the above-mentioned challenges and disadvantages of the conventional approaches, embodiments of the present invention aim to provide an improved dual- polarized antenna element. An objective is to provide particularly a dual-polarized slot-fed antenna element, which is less expensive, less complex, lighter, and more compact than conventionally. To this end, embodiments of the invention aim for a better integration of the components of the antenna element, particularly a better integration of feedings slots, EM walls, and transmission lines. The antenna element should be of low-profile and should be usable in an AAS (which means integration with a radio transceiver unit (RRU)). The antenna element should be suitable for placement in complex antenna arrays. The antenna element should particularly be usable in mMIMO arrays.

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

In particular, embodiments of the invention propose using a circuit board (e.g. PCB) and a dielectric structure to generate a stripline configuration for one or more transmission lines, and particularly to further integrate, by means of the dielectric structure, feeding slots and EM walls arranged around a patch radiating element. A first aspect of the invention provides a dual-polarized antenna element comprising: a circuit board including a bottom layer and a top layer; a dielectric structure with a conductive surface arranged above the top layer of the circuit board; a radiating element arranged above the conductive surface of the dielectric structure; wherein at least two slots configured to feed the radiating element are formed in the conductive surface of the dielectric structure; wherein transmission lines coupled to the slots are formed in the top layer of the circuit board; and wherein the transmission lines form a stripline configuration with the bottom layer of the circuit board and the conductive surface of the dielectric structure.

The antenna element of the first aspect profits from the use of the dielectric structure and its conductive surface. The dielectric structure is conformed such that it beneficially creates a substrate for the transmission lines implemented as strip lines in the stripline configuration. The dielectric structure further accommodates the slots required to feed the radiating element. Thus, it serves to generate the antenna environment. The conductive surface complements the dielectric structure by creating a top layer for the stripline configuration, and by realizing the slots. It may further create EM walls around the radiating element

Thus, the dielectric structure leads to a better integration of the components of the antenna element, particularly a better integration of the feedings slots, transmission lines, and optionally EM walls. The dielectric structure can be fabricated easily and is not expensive. Accordingly, the dual-polarized slot-fed antenna element of the first aspect is less expensive, less complex, lighter, and more compact than conventional dual-polarized antenna elements.

In an implementation form of the first aspect, the dielectric structure is a plastic structure with a metallized surface, particularly is a physical vapor deposition (PVD) metallized plastic structure or a molded interconnect device (MID) plastic structure.

In an implementation form of the first aspect, the bottom layer of the circuit board and the conductive surface of the dielectric structure form ground planes of the stripline configuration. Thus, a compact, low-profile antenna element can be realized.

In an implementation form of the first aspect, the dielectric structure and a dielectric material arranged between the bottom layer and the top layer of the circuit board form a substrate of the stripline configuration.

In an implementation form of the first aspect, the transmission lines are embedded in the substrate of the stripline configuration between the dielectric structure and the dielectric material of the circuit board.

In an implementation form of the first aspect, the bottom layer and the top layer are connected by a plurality of vias, and the vias are arranged such that they connect to a coupling area defined in the top layer, which is capacitively coupled to the conductive surface of the dielectric structure.

The coupling area closes a cavity created between the conductive surface of the dielectric structure and the bottom layer by the capacitive coupling.

In an implementation form of the first aspect, an electromagnetic wall is formed by the conductive surface of the dielectric structure around the radiating element.

Thus, the dielectric structure integrates the EM walls and the feeding slots, supporting a better integrated and improved antenna element.

In an implementation form of the first aspect, the radiating element is at least a metal patch.

In an implementation form of the first aspect, the at least two slots intersect each other, particularly form a cross-slot, each slot being configured to feed the radiating element according to a different polarization of the dual-polarized antenna element.

In an implementation form of the first aspect, the dielectric structure comprises an upward protrusion located at an intersection of the slots. The dielectric structure can beneficially be used to provide further functionalities. In this case, the protrusion may detach the center of the slots from the circuit board to generate a crossing path below the slots, such that very little energy is coupled to it.

In an implementation form of the first aspect, an air gap is formed by the upward protrusion between the dielectric structure and the top layer of the circuit board.

In an implementation form of the first aspect, the upward protrusion protrudes at least by a distance corresponding to 0.01 times a wavelength at a lowest radiating frequency of the radiating element.

In an implementation form of the first aspect, the dielectric structure forms a clearance at an outer edge.

The dielectric structure can provide additional features such as mechanical supports, cabling conduits, etc.

A second aspect of the invention provides an antenna including at least one antenna element according to the first aspect or any of its implementation forms.

The antenna of the second aspect enjoys the advantages of the antenna element, and can thus be improved. That is, due to the antenna element, the antenna can be built less complex and smaller.

In an implementation form of the first aspect, the antenna includes a plurality of antenna elements according to the first aspect or any of its implementation forms, arranged in at least one array, and/or is configured for mMIMO.

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 a dual-polarized antenna element according to an embodiment of the invention.

FIG. 2 shows a dual-polarized antenna element according to an embodiment of the invention with EM walls.

FIG. 3 shows a dual-polarized antenna element according to an embodiment of the invention, and particularly details of the circuit board.

FIG. 4 shows a dual-polarized antenna element according to an embodiment of the invention with additional features. FIG. 5 shows parts of a dual-polarized antenna element according to an embodiment of the invention in a top view.

FIG. 6 shows a dual-polarized antenna element according to an embodiment of the invention with additional features.

FIG. 7 shows a dual-polarized antenna element according to an embodiment of the invention compared to an example of a dual-polarized antenna element.

FIG. 8 shows an example of a dual-polarized antenna element. DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows a dual -polarized antenna element 100. The antenna element 100 may be configured for an antenna having one or more such antenna elements 100, particularly an array of such antenna elements 100, and may be suitable for mMIMO.

The antenna element 100 comprises a circuit board 101, e.g. realized by a PCB, which includes a bottom layer 101a and a top layer 101b (above the bottom layer 101b). Top layer 101b and bottom layer 101a may be metallization layers, and may be separated by a, e.g. dielectric, material arranged in between.

Above the top layer 101b is arranged a dielectric structure 102, particularly a plastic structure. The dielectric structure 102 has a conductive surface 102a, which may be made by PVD onto the dielectric structure 102 or by forming a MID device. The dielectric structure 102 may be flat as shown in FIG. 1, but can also have more complex shapes as shown in the next figures.

Above the dielectric structure 102, particularly above its conductive surface 102a, is arranged a radiating element 103, e.g. a metal patch. That is, the radiating element 103 may be a patch radiating element. The radiating element 103 is fed by at least two slots 104, i.e. at least two feeding slots. These slots 104 are formed in the conductive surface 102a of the dielectric structure 102. The slots 104 can be formed only in the conductive surface 102a (e.g. by etching), or also in the dielectric structure 102 (i.e. by etching also into or through the dielectric material).

Further, transmission lines 105, particularly RF lines, are formed in the top layer 101b of the circuit board 101. These conductive transmission lines 105 are coupled to the slots 104 formed in the conductive surface 102a. The transmission lines 105 further form a stripline configuration with the bottom layer 101a of the circuit board 101 (below) and the conductive surface 102a (above). That is, the bottom layer 101a and the conductive surface 102a function as respective ground planes in the stripline configuration, and the top layer 101b and a e.g. dielectric material between the bottom layer 101a and the top layer 101b function as a substrate in the stripline configuration. The transmission lines are embedded in this substrate.

FIG. 2 show a dual -polarized antenna element 100, which builds on the antenna element shown in FIG. 1. Same elements in FIG. 1 and FIG. 2 share the same reference signs and function likewise. Accordingly, also the antenna element 100 of FIG. 2 has the circuit board 101, dielectric structure 102, and radiating element 103.

The dual-polarized antenna element 100 of FIG. 2 has further an EM wall 200 (or EM walls) arranged around the radiating element 103. The EM wall(s) is formed by the conductive surface 102a of the dielectric structure 102. To this end, the dielectric structure 102 may be bent upwards at its outer edges, in order to form a surrounding wall or fence structure around the radiating element 103. The radiating element 103 is accordingly arranged in a first cavity defined by the dielectric structure 102, particularly formed by the EM walls 200. The dielectric structure 102 is of course arranged above the circuit board 101 as also in FIG. 1.

FIG. 3 show a dual -polarized antenna element 100, which builds on the antenna element shown in FIG. 2. Same elements in FIG. 2 and FIG. 3 share the same reference signs and function likewise. Accordingly, also the antenna element 100 of FIG. 3 has the circuit board 101, dielectric structure 102, and radiating element 103.

In particular, FIG. 3 shows a detailed view of the circuit board 101. FIG. 3 shows again the dielectric structure 102 that forms the EM wall(s) 200, as in FIG. 2, which define the first cavity, in which the radiating element 103 is arranged. The circuit board 101 is shown with its top layer 101b and bottom layer 101a. The circuit board 101 further includes one or more vias 300, which connect the bottom layer 101a and the top layer 101b. The vias 300 are particularly arranged such that they connect to a coupling area 500 (see FIG. 5) defined in the top layer 101b, which coupling area 500 closes a gap between the conductive surface 102a and the bottom layer 101a of the circuit board 101 by capacitive coupling. Thus, a second cavity is formed between the bottom layer 101a and the conductive surface 102a.

FIG. 4 shows a dual-polarized antenna element 100, which builds on the antenna element shown in FIG. 2. Same elements in FIG. 2 and FIG. 4 share the same reference signs and function likewise. Accordingly, also the antenna element 100 of FIG. 4 has the circuit board 101, dielectric structure 102, and radiating element 103.

FIG. 4 shows in particular on the left side a detailed view of the slots 104, which are formed, e.g. etched, in the conductive surface 102a of the dielectric structure 102, and shows a metallized are in the top layer 101b of the circuit board 101. Also the vias 300 are shown, as in FIG. 3. Further, FIG. 4 shows on the right side details of additional features provided by the dielectric structure 102. In particular, a clearance 400 is shown, which is formed at an outer edge of the dielectric structure 102. Such a clearance is, for instance, suitable for cable conduits.

FIG. 5 shows a dual-polarized antenna element 100, which builds on the antenna element shown in FIG. 2. Same elements in FIG. 2 and FIG. 5 share the same reference signs and function likewise. Accordingly, also the antenna element 100 of FIG. 5 has the circuit board 101, dielectric structure 102, and radiating element 103.

FIG. 5 shows on the left side a top view of the antenna element 100 without the radiating element 103. The slots 104, which are formed in the conductive surface 102a of the dielectric structure 102, are shown. The slots 104 are particularly cross-slots, which intersect each other. Each slot is responsible for feeding a different polarization into the radiating element 103 of the dual -polarized antenna element 100.

FIG. 5 shows further on the right side a top view of the antenna element 100 without the radiating element 103, and without the conductive surface 102a. Further, the dielectric structure 102 is shown transparent. The transmission lines 105, which are coupled to the slots 104, are thus visible. The transmission lines 105 may cross the slots 104 in the top view. In particular, each slot 104 may be symmetrically crossed by two transmission lines 105 on each of its ends, i.e. symmetrically to a mid-point of the slot, which may be defined by the slot intersection.

FIG. 5 also shows on the right side the coupling area 500, which is arranged along the outer edges of the dielectric structure 102, and is formed in the top layer 101b of the circuit board 101. Notably, the vias 300 shown in FIG. 3 may connect the bottom layer 101a and that coupling area 500. FIG. 6 shows a dual-polarized antenna element 100, which builds on the antenna element shown in FIG. 2. Same elements in FIG. 2 and FIG. 6 share the same reference signs and function likewise. Accordingly, also the antenna element 100 of FIG. 6 has the circuit board 101, dielectric structure 102, and radiating element 103.

FIG. 6 shows in particular a detailed view of (3D) properties of the dielectric structure 102. FIG. 6 shows that additional features can thus be realized by the dielectric structure 102 (PVD and/or MID). For instance, by means of forming the dielectric structure 101, the center of the (crossing) slot(s) 104 may be detached from the top layer 101b of the circuit board 101 (where currents are minimum), in order to generate a crossing path (tunnel) below the slot(s) 104, such that very little energy is coupled to it. To this end, the dielectric structure 102 may comprise an upward protrusion 600 located at the intersection of the slots 104. Accordingly, in the point where the slots 104 intersect, the intersection is lifted to a higher level (e.g. at least 0.01 lambda at the lowest frequency). This may effectively create an air gap between the circuit board 101 and the dielectric structure 101. That is, the air gap may formed by the upward protrusion 600, wherein the upward protrusion 600 protrudes at least by a distance corresponding to 0.01 times a wavelength at a lowest radiating frequency of the radiating element 103.

FIG. 7 shows a clipped plane comparing the profile of the antenna element 100 according to an embodiment of the invention with an exemplary antenna element, as it is shown in FIG. 8. It can be derived that due to the better integration of transmission lines 105, slots 104, and EM walls 200, provided by the dielectric structure 102, the antenna element 100 is less complex and has fewer parts.

In summary, embodiments of the present invention achieve multiple benefits. In particular, the embodiments reduce the complexity and cost of a dual-polarized antenna elements, by using material properties of the dielectric structure 102 and embedding several functionalities into this structure 102. The use of e.g. metallized plastic such as PVD or MID as the dielectric structure 102 reduces significantly the weight of the antenna element 100, and thus even more a full array of such antenna elements. The antenna element 100 meets all the requirements needed to work in an AAS. It can be produced by simple mechanical implementation, of only two parts. The described antenna element 100 can be placed in complex antenna arrays. The feeding of the radiating element 103 can be placed on top of an antenna reflector (e.g. implemented by the circuit board 101), and the bottom of the feeding can be completely clear such that active/passive components can be directly soldered into it. The antenna element 100 thus has an increased flexibility of use. The antenna element can be used in mMIMO, due to its compact size (43x43mm @CB frequency range).

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.