A MULTIBAND ANTENNA SYSTEM AND METHOD FOR PROVIDING THE SAME

TECHNICAL FIELD

The present invention relates to equipment for wireless communication systems. More specifically, the present invention relates to a multiband antenna system for a base station for wireless communication in a communication network, in particular a 5G communication network, and a method of manufacturing such a multiband antenna system.

BACKGROUND

Antennas of base stations for wireless communication networks are usually configured to operate, i.e. transmit and receive signals in specific frequency bands. From time to time, such as when a new wireless communication standard is rolled out, new frequency bands become available. For instance, for the next generation of mobile communications MIMO frequencies will become available below 6 GHz. In order to be capable of operating in new frequency bands a base station can be upgraded, for instance, by just adding new equipment, in particular antennas, to the existing equipment, which however often increases the size of the base station, or by replacing the existing equipment with new equipment configured to operate at both the old frequency bands as well as at the new frequency bands (e.g. replacing legacy 700 MHz LTE equipment by new or updated equipment that can serve both 700 MHz LTE as well as the integrated MIMO band, i.e. C- band). The generally preferred option of replacing existing equipment with new more sophisticated equipment, however, often implies that more functionality has to be integrated in the new equipment, which should not exceed the size of the existing equipment. Higher integrated equipment in terms of antennas implies a tighter packaging of supported frequency bands in the same antenna, i.e. space. With respect to passive antenna design this implies that more antenna arrays must coexist in a system of a given size. This can become an issue in that with a higher integration the components required for beam-shaping and de-coupling, i.e. isolating the different frequency bands, such as metallic reflection layers, begin obstructing each other.

Thus, there is a need for a compact multiband antenna system and a method for providing such a multiband antenna system. SUMMARY

It is an object of the invention to provide an improved multiband antenna system and a corresponding method for providing such a multiband antenna system.

The foregoing and other objects are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

Generally, embodiments of the invention are based on the idea of utilizing frequency selective reflecting metal surfaces for beam-shaping and isolating different frequency bands in a multiband antenna system.

More specifically, according to a first aspect the invention relates to a multiband antenna system comprising: one or more first antenna elements configured to transmit or receive radio frequency (RF) signals at a first frequency f1 ; one or more second antenna elements configured to transmit or receive RF signals at a second frequency f2, which is lower than the first frequency, i.e. f2 < f1 ; a first metallic surface layer configured to reflect the RF signals at the first frequency and the RF signals at the second frequency for guiding the RF signals at the first frequency and the RF signals at the second frequency within the antenna system; and a second metallic surface layer configured to reflect the RF signals at the first frequency for guiding the RF signals at the first frequency within the antenna system, wherein the second metallic surface layer is transparent for the RF signals at the second frequency.

Thus, advantageously a compact multiband antenna system is provided, where the beam shaping and isolating components for the higher frequency can be designed independent of the lower frequency. In other words, antenna components, which are necessary for beam-shaping and isolating at the higher first frequency, but in conventional multiband antenna systems might obstruct beam-shaping and isolating at the lower second frequency, do not interfere with beam-shaping and isolating at the lower second frequency in a compact multiband antenna system according to the first aspect of the invention.

Thus, the selective frequency metallic surface layers can simplify the design of a multiband antenna system according to embodiments of the invention. Thus,

embodiments of the invention allow integrating a larger number of antenna arrays within the same spatial constraints. Moreover, embodiments of the invention can reduce the production costs of multiband antenna systems by replacing solid metal parts by using metallized polymers for providing the metallic surface layers on a support, while at the same time reducing the weight of the whole system.

In a further possible implementation form of the first aspect, the one or more first antenna elements are configured to transmit or receive RF signals in a first frequency band which includes the first frequency, and/or the one or more second antenna elements are configured to transmit or receive RF signals in a second frequency band which includes the second frequency. The first frequency band could be, for instance, the C-band, i.e. the frequency band from 3.3 to 3.8 GHz, and the second frequency band could be the 700 MHz LTE frequency band.

In a further possible implementation form of the first aspect, the multiband antenna system further comprises a support element, wherein the one or more first antenna elements and/or the one or more second antenna elements are supported by the support element and wherein the first metallic surface layer and/or the second metallic surface layer are arranged on a surface of the support element such that the first metallic surface layer beam-shapes and/or isolates the RF signals at the first frequency and the RF signals at the second frequency and the second metallic surface layer beam-shapes and/or isolates the RF signals at the first frequency within the antenna system but not the RF signals at the second frequency. Advantageously, the support element can provide stability to the potentially rather thin first and/or second metallic surface layer and can define the desired shape thereof for guiding RF signals within the antenna system.

In a further possible implementation form of the first aspect, the support element is an injection-moulded or thermoform ed support element made from a dielectric material, in particular acrylonitrile butadiene styrene, ABS, copolymer and/or polycarbonate, PC.

Thus, advantageously, the support element can act as a dielectric and can be made from a robust, but inexpensive material.

In a further possible implementation form of the first aspect, the antenna system further comprises a protective coating, in particular an organic surface protection, OSP, coating arranged on top of the first metallic surface layer and/or the second metallic surface layer. Thereby, the first metallic surface layer and/or the second metallic surface layer can be better protected from performance degrading environmental effects. In a further possible implementation form of the first aspect, the thickness of the first metallic surface layer and/or the thickness of the second metallic surface layer is in the range of about 0.1 to about 10 pm. Thus, the first metallic surface layer and/or the second metallic surface layer can be provided with a rather small thickness and, thus, with small material costs using, for instance, a physical vapour deposition, PVD, process.

In a further possible implementation form of the first aspect, the first metallic surface layer and/or the second metallic surface layer comprises at least one of aluminium, copper, or chromium.

According to a second aspect the invention relates to a corresponding method for providing a compact multiband antenna system. The method comprises the steps of: providing one or more first antenna elements configured to transmit and/or receive RF signals at a first frequency; providing one or more second antenna elements configured to transmit and/or receive RF signals at a second frequency, which is lower than the first frequency; providing a first metallic surface layer configured to reflect the RF signals at the first frequency and the RF signals at the second frequency for guiding the RF signals at the first frequency and the RF signals at the second frequency within the antenna system; and providing a second metallic surface layer configured to reflect the RF signals at the first frequency for guiding the RF signals at the first frequency within the antenna system, wherein the second metallic surface layer is transparent for the RF signals at the second frequency.

In a further possible implementation form of the second aspect, the one or more first antenna elements are configured to transmit and/or receive RF signals in a first frequency band, including the first frequency, and/or the one or more second antenna elements are configured to transmit and/or receive RF signals in a second frequency band, including the second frequency.

In a further possible implementation form of the second aspect, the method further comprises providing a support element, wherein the one or more first antenna elements and/or the one or more second antenna elements are supported by the support element and wherein the first metallic surface layer and/or the second metallic surface layer are arranged on a surface of the support element such that the first metallic surface layer beam-shapes and/or isolates the RF signals at the first frequency and the RF signals at the second frequency and the second metallic surface layer beam-shapes and/or isolates the RF signals at the first frequency within the antenna system but not the RF signals at the second frequency.

In a further possible implementation form of the second aspect, the support element is an injection-moulded or thermoformed support element made from a dielectric material, in particular acrylonitrile butadiene styrene, ABS, copolymer and/or polycarbonate, PC.

In a further possible implementation form of the second aspect, the method further comprises providing a protective coating, in particular an organic surface protection, OSP, coating on top of the first metallic surface layer and/or the second metallic surface layer.

In a further possible implementation form of the second aspect, the step of providing the first metallic surface layer and/or the step of providing the second metallic surface layer comprises providing the first and/or second metallic surface layer using a physical vapour deposition, PVD, process.

In a further possible implementation form of the second aspect, the step of providing the first metallic surface layer comprises the step of providing the first metallic surface layer with a thickness depending on the material of the first metallic surface layer, the first frequency and/or the second frequency and/or wherein the step of providing the second metallic surface layer comprises the step of providing the second metallic surface layer with a thickness depending on the material of the second metallic surface layer, the first frequency and/or the second frequency.

In a further possible implementation form of the second aspect, the thickness of the first metallic surface layer and/or the thickness of the second metallic surface layer is in the range from about 0.1 to about 10 pm.

In a further possible implementation form of the second aspect, the first metallic surface layer and/or the second metallic surface layer comprises aluminium, copper and/or chromium.

Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

In the following embodiments of the invention are described in more detail with reference to the attached figures and drawings, in which:

Fig. 1 is a schematic cross-sectional view of a multiband antenna system according to an embodiment;

Fig. 2 is a graph illustrating the radiation penetration depth as a function of the frequency of radiation;

Fig. 3 is a schematic drawing illustrating different material layers of a multiband antenna system according to an embodiment;

Fig. 4 is a flow diagram illustrating steps of a method for providing a multiband antenna system according to an embodiment of the invention.

In the following identical reference signs refer to identical or at least functionally equivalent features.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the invention or specific aspects in which embodiments of the invention may be used. It is understood that embodiments of the invention may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the invention is defined by the appended claims.

For instance, it is to be understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless specifically noted otherwise.

Figure 1 shows a schematic cross-sectional view of a multiband antenna system 100 according to an embodiment of the invention. The multiband antenna system 100 is configured to operate simultaneously at a first frequency f1 (or a first frequency band including the first frequency f1 ) and a second frequency f2 (or a second frequency band including the second frequency f2), wherein the second frequency f2 (or frequency band) is lower than the first frequency f1 (or frequency band), i.e. f2 < f1. For instance, the first frequency f1 could be a frequency within the C-band, i.e. 3.3 - 3.8 GHz, or the C-band itself and the second frequency f2 could be a 700 MHz LTE frequency.

In the embodiment shown in figure 1 , the multiband antenna system 100 comprises two first antenna elements, i.e. radiators 101 configured to operate, i.e. transmit or receive RF signals at the first frequency f1 (referred to as“Radiator 1” and“Radiator 2” in figure 1 ). In other embodiments, the multiband antenna system 100 can have more or less than two first antenna elements 101.

In the embodiment shown in figure 1 , the multiband antenna system 100 further comprises a second antenna element, i.e. radiator 103 configured to operate, i.e. transmit or receive RF signals at the second lower frequency f2 (referred to as“Radiator 3” in figure 1 ). In other embodiments, the multiband antenna system 100 can have more than one second antenna element 103.

As illustrated by the dashed line in figure 1 , the multiband antenna system 100 further comprises a first metallic surface layer 105 configured to reflect the RF signals at the first frequency f1 and the RF signals at the second frequency f1 for guiding the RF signals at the first frequency f1 and the RF signals at the second frequency f2 within the antenna system 100 (as illustrated in figure 1 by the exemplary RF radiation ray emitted by the second antenna element 103 and reflected by the first metallic surface layer 105).

As illustrated by the dotted line segments in figure 1 , the multiband antenna system 100 further comprises at least one second metallic surface layer 107 or second metallic surface layer segments 107. Different to the first metallic surface layer 105, which is reflective for RF signals at both the first frequency f1 and the second frequency f2, the second metallic surface layer 107 is reflective for RF signals at the first frequency f 1 , but substantially transparent for RF signals at the lower second frequency f2 (as illustrated in figure 1 by the exemplary RF radiation ray emitted by the second antenna element 103 and reflected by the first metallic surface layer 105 and the plurality of exemplary radiation rays emitted by the first antenna elements 101 and reflected by segments of the second metallic surface layer 107). Consequently, the second metallic surface layer 107 is configured to reflect the RF signals at the first frequency f1 for guiding the RF signals at the first frequency f1 within the antenna system 100, but transparent for the RF signals at the lower second frequency f2.

In the embodiment shown in figure 1 , the multiband antenna system 100 further comprises a support element 109, wherein the first antenna elements 101 and the second antenna element 103 are supported by, i.e. arranged on the support element 109, which may be substantially planar (as illustrated in figure 1 ). At least partially, also the first metallic surface layer 105 and/or the second metallic surface layer 107 can be arranged on a top surface of the support element 109 such that the first metallic surface layer 105 beam-shapes and/or isolates the RF signals at the first frequency f1 and the RF signals at the lower second frequency f2 within the antenna system 100 and the second metallic surface layer 107 beam-shapes and/or isolates the RF signals at the first frequency f1 within the antenna system 100 but not the RF signals at the lower second frequency f2. According to an embodiment, the support element 109 can be an injection-moulded or thermoformed support element 109 made from a dielectric material, in particular acrylonitrile butadiene styrene (ABS) copolymer and/or polycarbonate (PC).

In figure 1 the dashed line illustrates the effective reflecting area for the second antenna element 103 (i.e.“Radiator 3”) at the lower second frequency f2. The dotted line segments illustrate the effective reflecting areas for the first antenna elements 101 (i.e.“Radiator 1” and“Radiator 2”) at the first frequency f1. For the lower second frequency f2 the ideal shape for avoiding mutual coupling between the two first antenna elements 101 (i.e. “Radiator 1” and“Radiator 2”) can be provided by physical walls for separating the two first antenna elements 101 (i.e.“Radiator 1” and“Radiator 2”) provided, for instance, by the support element 109. This function is provided by the second metallic surface layer segments 107 for the first frequency f1. For the lower second frequency f2 the ideal reflecting plane is just a planar surface. As the non-planar shape defined by the second metallic surface layer segments 107 is transparent for the lower second frequency f2, the effective reflecting plane is defined by the dashed line. Thus, the coexistence with the isolation elements for the higher frequency f1 can be ensured.

Thus, embodiments of the invention make use of the fact that metallic surface layers having a sufficiently small thickness can be transparent, while for larger thicknesses become reflective for an RF signal at a given frequency. This is also known as the Skin effect, which describes the attenuation of an RF signal at a given frequency and defines the so-called skin depth, which depends on material properties and according to theory is inversely proportional to the square root of the frequency. Figure 2 is a graph illustrating the radiation penetration depth, i.e. skin depth as a function of the frequency of the RF signals for different thicknesses and different materials, such as silver, copper, gold, aluminium, brass or steel, of the first metallic surface layer 105 and the second metallic surface layer 107. Based on the information provided, for instance, in figure 2 the thickness of the second metallic surface layer 107 may be selected for a first frequency f1 = 3.5 GHz, a second frequency f2 = 700 MHz and the material of the second metallic surface layer 107 (e.g. aluminium) to be reflective for RF signals at the first frequency f 1 , but transparent for RF signals at the second frequency f2. According to an embodiment, the thickness of the first metallic surface layer 105 and/or the thickness of the second metallic surface layer 107 is in the range from 0.1 to 10 pm. For instance, according to an embodiment the second metallic surface layer 107 consists of or comprises aluminium and has a thickness of 2 pm so that it defines a reflective structure for the first frequency f1 in the C-band, i.e. 3.3 - 3.8 GHz, but is transparent for the lower second frequency f2 = 700 MHz (LTE).

Figure 3 is a schematic drawing illustrating different material layers of the multiband antenna system 100 according to an embodiment. As can be taken from figure 3, according to an embodiment the multiband antenna system 100 further comprises a protective coating layer 1 1 1 , in particular an organic surface protection, OSP, coating 1 1 1 arranged on top of the first metallic surface layer 105 and/or the second metallic surface layer 107. In the embodiment shown in figure 3, the first metallic surface layer 105 and/or the second metallic surface layer 107 are arranged on top of the support element 109, which can comprise or consist of a polymer, such as ABS/PC. According to another embodiment, the first metallic surface layer 105 and/or the second metallic surface layer 107 can be arranged on the bottom of the support element 109. The support element 109 can be provided, for instance, by injection moulding, deep drawing or thermoforming. According to an embodiment, the first metallic surface layer 105 and/or the second metallic surface layer 107 can be provided on the support element 109 with the desired thickness using a metallization process, in particular a physical vapour deposition, PVD, process.

Figure 4 is a flow diagram illustrating steps of a corresponding method 400 for providing the compact multiband antenna system 100 according to an embodiment of the invention. The method 400 comprises the steps of: providing 401 the one or more first antenna elements 101 configured to transmit and/or receive RF signals at a first frequency;

providing 403 the one or more second antenna elements 103 configured to transmit and/or receive RF signals at a second frequency, which is lower than the first frequency; providing 405 the first metallic surface layer 105 configured to reflect the RF signals at the first frequency and the RF signals at the second frequency for guiding the RF signals at the first frequency and the RF signals at the second frequency within the antenna system 100; and providing 407 the second metallic surface layer 107 configured to reflect the RF signals at the first frequency for guiding the RF signals at the first frequency within the antenna system 100, wherein the second metallic surface layer 107 is transparent for the RF signals at the second frequency. As already described above, the first frequency and/or the second frequency can be part of a first frequency band or a second frequency band, respectively.

According to an embodiment, the method 400 further comprises the step of providing the support element 109 for supporting the one or more first antenna elements 101 and/or the one or more second antenna elements 103, wherein the first metallic surface layer 105 and/or the second metallic surface layer 107 are arranged on a surface of the support element 109 such that the first metallic surface layer 105 beam-shapes and/or isolates the RF signals at the first frequency and the RF signals at the second frequency and the second metallic surface layer 107 beam-shapes and/or isolates the RF signals at the first frequency within the antenna system 100 but because of its transparency not the RF signals at the second frequency. According to an embodiment, the first metallic surface layer 105 and/or the second metallic surface layer 107 are provided on the support element 109 using a physical vapour deposition (PVD) process. The first metallic surface layer 105 may be provided with a thickness depending on the material of the first metallic surface layer 105, the first frequency f1 and/or the second frequency f2. Likewise, the second metallic surface layer 107 may be provided with a thickness depending on the material of the second metallic surface layer 107, the first frequency f1 and/or the second frequency f2. Based on the information provided, for instance, in figure 2 the thickness of the second metallic surface layer 107 may be selected for a first frequency f1 = 3.5 GHz, a second frequency f2 = 700 MHz and the material of the second metallic surface layer 107 (e.g. aluminium) to be reflective for RF signals at the first frequency f1 , but transparent for RF signals at the second frequency f2. According to an embodiment, the thickness of the first metallic surface layer 105 and/or the thickness of the second metallic surface layer 107 is in the range from 0.1 to 10 pm.

In several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described apparatus embodiment is merely exemplary. For example, the unit division is merely logical function division and may be other division in actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or

communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

In addition, functional units in the embodiments of the invention may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units are integrated into one unit.