ANTENNA ELEMENT FOR A MULTI-BAND ANTENNA DEVICE

Abstract

An antenna element for a multi-band antenna device includes a dielectric body provided with one or more metal layers. The dielectric body includes a base plate and one or more wall elements arranged on the base plate. One or more first radiating elements and one or more second radiating elements are arranged on the base plate, and are configured to radiate in a first and a second frequency band, respectively. A first feeding network is connected to the first radiating elements and a second feeding network is connected to the second radiating elements, for operating the first and second radiating elements as a first and second antenna array, respectively. The first feeding network is provided, at least partly, as a metal layer of the one or more metal layers on the one or more wall elements.

Claims

1. An antenna element for a multi-band antenna device, the antenna element comprising: a dielectric body provided with one or more metal layers, the dielectric body comprising a base plate and one or more wall elements arranged on the base plate; one or more first radiating elements arranged on the base plate, each of the one or more first radiating elements being configured to radiate in a first frequency band; one or more second radiating elements arranged on the base plate, each of the one or more second radiating elements being configured to radiate in a second frequency band; a first feeding network connected to the one or more first radiating elements, for operating the one or more first radiating elements as a first antenna array; and a second feeding network connected to the one or more second radiating elements, for operating the one or more second radiating elements as a second antenna array; wherein the first feeding network is provided, at least partly, as a metal layer of the one or more metal layers on the one or more wall elements.

2. The antenna element according to claim 1, wherein: the one or more wall elements comprise an outer wall element, which extends along edges of the base plate, and a part of the first feeding network is provided as a metal layer of the one or more metal layers on the outer wall element.

3. The antenna element according to claim 2, wherein: the part of the first feeding network is provided as a metal layer of the one or more metal layers on one of surfaces of the outer wall element, and a ground for the first feeding network is provided as a metal layer of the one or more metal layers on an opposite surface of the surfaces of the outer wall element.

4. The antenna element according to claim 2, wherein: the outer wall element is configured to conform radiation from the one or more first radiating elements and from the one or more second radiating elements; or the outer wall element is configured to conform radiation from the one or more first radiating elements or from the one or more second radiating elements.

5. The antenna element according to claim 2, wherein: the first feeding network comprises a first feeding element for operating the one or more first radiating elements according to a first polarization, and a second feeding element for operating the one or more first radiating elements according to a second polarization; the outer wall element comprises a first wall section and a second wall section; and the first feeding element is provided as a metal layer of the one or more metal layers on the first wall section, and the second feeding element is provided as a metal layer of the one or more metal layers on the second wall section.

6. The antenna element according to claim 2, wherein: the one or more wall elements further comprise one or more inner wall elements, each of the one or more inner wall elements connecting the outer wall element to one of the one or more first radiating elements; and a further part of the first feeding network is provided as a metal layer of the one or more metal layers on the inner wall elements.

7. The antenna element according to claim 1, wherein: the second feeding network is provided, at least partly, as a metal layer of the one or more metal layers on the base plate.

8. The antenna element according to claim 7, wherein: the one or more wall elements, the one or more first radiating elements and the one or more second radiating elements are arranged on an upper surface of the base plate; a part of the second feeding network is provided as a metal layer of the one or more metal layers on a lower surface of the base plate; and the base plate is arranged on a reflector plate of the antenna element, the reflector plate serving as ground for the second feeding network.

9. The antenna element according to claim 8, wherein: the reflector plate is configured to reflect radiation from the one or more first radiating elements and from the one or more second radiating elements into a main radiation direction; or the reflector plate is configured to reflect radiation from the one or more first radiating elements or from the one or more second radiating elements into a main radiation direction.

10. The antenna element according to claim 7, wherein: the one or more wall elements, the one or more first radiating elements and the one or more second radiating elements are arranged on an upper surface of the base plate; the second feeding network is provided as a metal layer of the one or more metal layers on the upper surface of the base plate; and a ground for the second feeding network is provided as a metal layer of the one or more metal layers on a lower surface of the base plate.

11. The antenna element according to claim 1, wherein: the first feeding network and the second feeding network are arranged without line crossing of feeding lines of the first feeding network and the second feeding network.

12. The antenna element according to claim 1, wherein: the one or more first radiating elements are one or more low band (LB) radiating elements, and the one or more second radiating elements are one or more high band (HB) radiating elements; or the one or more first radiating elements are one or more HB radiating elements, and the one or more second radiating elements are one or more LB radiating elements.

13. The antenna element according to claim 1, wherein: the first frequency band is lower than the second frequency band; or the first frequency band is a frequency range of 1.7-2.7 GHz, and the second frequency band is a frequency range of 3.3-3.8 GHz.

14. The antenna element according to claim 1, wherein: the one or more first radiating elements comprise one or more dipole radiating elements; or the one or more second radiating elements comprise one or more patch radiating elements.

15. The antenna element according to claim 1, wherein: the one or more first radiating elements or the one or more second radiating elements comprise one or more linear dual-polarized radiating elements.

16. The antenna element according to claim 1, wherein: the one or more first radiating elements or the one or more second radiating elements are formed, at least partly, by the dielectric body.

17. The antenna element according to claim 1, wherein: each of the one or more second radiating elements comprises: a first patch formed by the dielectric body, and a second patch stacked onto the first patch.

18. The antenna element according to claim 1, wherein: each of the one or more first radiating elements comprises: a balun formed by the dielectric body, and a printed circuit boards (PCB), in which a dipole is formed, the PCB being connected to the balun.

19. A multi-band antenna device, comprising one or more antenna elements, each of the one or more antenna elements comprising: a dielectric body provided with one or more metal layers, the dielectric body comprising a base plate and one or more wall elements arranged on the base plate; one or more first radiating elements arranged on the base plate, each of the one or more first radiating elements being configured to radiate in a first frequency band; one or more second radiating elements arranged on the base plate, each of the one or more second radiating elements being configured to radiate in a second frequency band; a first feeding network connected to the one or more first radiating elements, for operating the one or more first radiating elements as a first antenna array; and a second feeding network connected to the one or more second radiating elements, for operating the one or more second radiating elements as a second antenna array; wherein the first feeding network is provided, at least partly, as a metal layer of the one or more metal layers on the one or more wall elements.

20. A method of producing an antenna element for a multi-band antenna device, the method comprising: forming a dielectric body comprising a base plate and one or more wall elements arranged on the base plate; forming one or more first radiating elements arranged on the base plate, each of the one or more first radiating elements being configured to radiate in a first frequency band; forming one or more second radiating elements arranged on the base plate, each of the one or more second radiating elements being configured to radiate in a second frequency band; forming a first feeding network connected to the one or more first radiating elements, for operating the one or more first radiating elements as a first antenna array; and forming a second feeding network connected to the one or more second radiating elements, for operating the one or more second radiating elements as a second antenna array; wherein the first feeding network is formed, at least partly, by metallizing the one or more wall elements.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0065] The above described aspects and implementation forms will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which

[0066] FIG. 1 shows an antenna element according to at least one embodiment.

[0067] FIG. 2 shows a top view of an antenna element according to at least one embodiment.

[0068] FIG. 3 shows an enlarged top view of the antenna element of FIG. 2.

[0069] FIG. 4 shows a bottom view of the antenna element of FIG. 2 and FIG. 3.

[0070] FIG. 5 shows an enlarged view of the antenna element of FIG. 4.

[0071] FIG. 6 shows an antenna element according to at least one embodiment.

[0072] FIG. 7 shows a further dielectric body of an antenna element according to at least one embodiment.

[0073] FIG. 8 shows an antenna element according to at least one embodiment comprising a dielectric body and a further dielectric body.

[0074] FIG. 9 shows an exemplary antenna element, according to at least one embodiment, with first and second radiating elements arranged along the same line.

[0075] FIG. 10 shows an exemplary antenna element, according to at least one embodiment, in a triple-band implementation.

[0076] FIG. 11 shows an exemplary antenna element, according to at least one embodiment, with a 2LB/4HB combination.

[0077] FIG. 12 shows an exemplary antenna element, according to at least one embodiment, with a 1LB/3HB combination.

[0078] FIG. 13 shows an exemplary antenna element, according to at least one embodiment, with a 1LB/4HB combination.

[0079] FIG. 14 shows a flow chart of a method according to at least one embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0080] The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components, materials, values, steps, operations, materials, arrangements, or the like, are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. Other components, values, operations, materials, arrangements, or the like, are contemplated. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0081] In some embodiments, an antenna element is configured to have a dielectric body with one or more metal layers arranged on the dielectric body. The one or more metal layers form one or more feeding networks for at least two different antenna arrays of radiating elements of the antenna element, wherein each array comprises one or more radiating elements.

[0082] FIG. 1 shows an antenna element 100 according to at least one embodiment. The antenna element 100 may be used to form a multi-band antenna device, for instance, a dual-band antenna device or a triple-band antenna device. The antenna element 100 of FIG. 1 is exemplarily shown to work in two frequency bands, but it may work in more than two frequency bands.

[0083] The antenna element 100 comprises a dielectric body 101 provided with one or more metal layers. The one or more metal layers may be arranged on the dielectric body 101, particularly on surfaces of the dielectric body 101. However, one or more metal layers could also be provided within the dielectric body 101. Further, the dielectric body may be made of plastic. In particular, the dielectric body may thus be a selectively metallized plastic part. The dielectric body 101 comprises a base plate 101a and one or more wall elements 101b, 101c, which are arranged on the base plate 101a. The one or more wall elements 101b, 101c may protrude from the base plate 101a along a z-axis (i.e., an axis normal to the base plate), and may further be formed integrally with the base plate 101a. The one or more wall elements 101b, 101c may comprise an outer wall element 101b, for instance, surrounding the base plate 101a, i.e., extending along the edges of the base plate 101a (as shown in FIG. 1). Further, the one or more wall elements 101b, 101c may comprise one or more inner wall elements 101c, i.e., one or more wall elements 101c (shown in FIG. 2) that are arranged centrally on the base plate 101a and/or are arranged within the area surrounded by the outer wall element 101b.

[0084] Further, the antenna element 100 comprises one or more first radiating elements 102, which are arranged on the base plate 101a, for example regularly (e.g., in rows and/or columns) or irregularly, wherein each first radiating element 102 is configured to radiate in a first frequency band. The antenna element 100 also comprises one or more second radiating elements 103 arranged on the base plate 101a, for example regularly (e.g., in rows and/or columns) or irregularly, and/or interleaved with the first radiating elements 102, wherein each second radiating element 103 is configured to radiate in a second frequency band. The first frequency band and the second frequency band may be different frequency bands. For instance, the first frequency band may be lower than the second frequency band, or vice versa. The first frequency band and the second frequency band may be overlapping, in particular, partially overlapping, or they may be non-overlapping. For instance, the first frequency band may be a frequency range of 1.7-2.7 GHz, and the second frequency band may be a frequency range of 3.3-3.8 GHz.

[0085] The one or more first radiating elements 102 may comprise one or more dipole radiating elements, and/or the one or more second radiating elements 103 may comprise one or more patch radiating elements, or vice versa. Thereby, the one or more first radiating elements 102 and/or the one or more second radiating elements 103 may comprise one or more linear dual-polarized radiating elements. The first radiating elements 102 may comprise one or more LB radiating elements, and may thus form an LB antenna array. The second radiating elements 103 may comprise one or more HB radiating elements, and may thus form a HB antenna array. Alternatively, the first radiating elements 102 may comprise one or more HB radiating elements, and the second radiating elements, 103 may comprise one or more LB radiating elements. The one or more first radiating elements 102 and/or the one or more second radiating elements 103 may be formed, at least partly, by the dielectric body 101, i.e., by one or more metal layers of the dielectric body 101.

[0086] The antenna element 100 further comprises a first feeding network 104 connected to the one or more first radiating elements 102, for operating the one or more first radiating elements 102 as a first antenna array. Further, the antenna element 100 comprises a second feeding network 105 connected to the one or more second radiating elements 103, for operating the one or more second radiating elements 103 as a second antenna array. The first feeding network 104 and/or the second feeding network 105 may comprise one or more feeding lines, in particular, to connect to the respective radiating elements 102/103 fed by the feeding network 104/105. The first feeding network 104 and the second feeding network 105 may thereby be arranged without any crossings of respective feeding lines. Neither the first feeding network 104 nor the second feeding network 105 may further require a multi-layer structure.

[0087] In particular, the first feeding network 104 is provided, at least partly, as a metal layer of the one or more metal layers on the one or more wall elements 101b, 101c, i.e., is formed by the dielectric body 101. For instance, the first feeding network 104 may be provided on the outer wall element 101b and/or on one or more inner wall elements 101c. That is, the first feeding network 104 may be integrated into the wall elements 101b, 101c of the dielectric body 101 of the antenna element 100. For instance, the one or more wall elements 101b, 101c may have first surfaces wherein the first feeding network 104 is provided, particularly as metallization or a metal layer, on the first surfaces. Further, the one or more wall elements 101b, 101c may have second surfaces, which may be used as ground for the feeding network 104, the ground being provided as metallization or a metal layer on the second surfaces. The outer wall element 101b may further serve as an electrical fencing, which is configured to conform the radiation pattern of one or both of the first and second frequency band. That is, the outer wall element 101b may be configured to conform radiation from the one or more first radiating elements 102 and/or from the one or more second radiating elements 103.

[0088] Also the second feeding network 105 may be provided, at least partly, as a metal layer on the dielectric body 101, particularly on the base plate 101a. That is, the second feeding network 105 may be integrated into a bottom part of the dielectric body 101 of the antenna element 100. It is, however, also possible to provide, at least part of, the second feeding network 105 on the one or more wall elements 101b, 101c.

[0089] FIGS. 2-5 show an antenna element 100 according to at least one embodiment, which builds on the antenna element(s) described with respect to FIG. 1. Same elements in FIG. 1 and FIGS. 2-5 are provided with the same reference signs, and may be implemented likewise. In particular, FIG. 2 shows a top-view of the antenna element 100, FIG. 3 shows an enlarged top-view of the antenna element 100, FIG. 4 shows a bottom-view of the antenna element 100, and FIG. 5 shows an enlarged bottom-view of the antenna element 100.

[0090] In particular, in FIGS. 2-5, the first radiating elements 102 are LB radiating elements and form an LB array, and the second radiating elements 103 are HB radiating elements and form a HB array.

[0091] As can be seen in FIG. 2 and FIG. 3, the first feeding network 105 of the LB radiating elements 102 is arranged at least partly on the one or more wall elements 101b, 101c. The first feeding network 104 is particularly arranged on the outer wall element 101b of the dielectric body 101. Thereby, one of the polarizations may be arranged in a first wall section of the outer wall element 101b, for instance, the left part of the outer wall element 101b. The other polarization may be arranged in a second wall section of the outer wall element 101b, for instance, the right part of the outer wall element 101b. The inner wall elements 101c of the dielectric body 101 may be used to route signals from the LB radiating elements 102 (those arranged in the center, particularly arranged between the HB radiating elements 103) to the outer wall element 101b. The first feeding network 104 could also be arranged on the inner wall elements 101c of the dielectric body 101.

[0092] As can be seen in FIG. 4 and FIG. 5, the second feeding network 105 of the HB radiating elements is arranged in the lower surface of the bottom area of the dielectric body 101, i.e., in the base plate 101a. The dielectric body 101 is further arranged on top of a reflector plate that serves as ground for the second feeding network 105 for the HB array. An implementation, in which the second feeding network 105 is arranged on the upper surface of the base plate 101a of the dielectric body 101, and the ground is arranged in the lower surface of the base plate 101a or vice versa (without using any reflector plate), is also possible.

[0093] In FIGS. 2-5, as an example, the HB is 3.3-3.8 GHz and the LB band is 1.7-2.7 GHz. The spacing between HB radiation elements 103 may be 43 mm in horizontal and 62.5 mm in vertical, whereas the vertical spacing between the LB radiating elements 102 may be 125 mm.

[0094] The LB radiating elements may be cross-fed dipoles and the HB radiating elements 103 may probe-fed patches. Some or all radiating elements 102/103 may be linear dual-polarized +/−45 slant.

[0095] As exemplarily shown in FIGS. 2-5, there may be three dipole radiating elements 102 working in the LB, and twelve patch radiating elements 103 working in the HB. In this particular example, the HB radiating elements 103 are clustered into four groups of three dual-polarized radiating elements 103 each (best seen in FIG. 4), wherein two clusters are on one (long) side of the antenna element 100, and the other two clusters are on the other (long) side of the antenna element 100.

[0096] The above-mentioned frequency bands, dimensions and clustering serve only as an example to convey an idea of some embodiments. However, further embodiments can be extended to be used with any other combination of frequency bands, dimensions and clustering. The embodiments in the present disclosure are also not limited to any specific kind of radiating element(s) 102 and 103.

[0097] FIG. 6 shows an antenna element 100 according to at least one embodiment, which builds on the antenna element(s) described with respect to FIGS. 2-5. Same elements in FIG. 6 and FIGS. 2-5 are provided with the same reference signs, and may be implemented likewise. In particular, FIG. 6 shows that a first part 102a of a first radiating element 102 may be formed by the dielectric body 101, and a second part 102b of the first radiating element 102 may be implemented as separate part 102b, i.e., as a part 102b that is added onto the dielectric body 101. For example, as shown in FIG. 6, a dipole of the first radiating element 102 may be implemented in an additional PCB (being the part 102b), which may be soldered to the part 102a, specifically a balun, of the first radiating element 102 formed by the dielectric body 101. In particular, each of the one or more first radiating elements 102 may comprise a balun 102a formed by the dielectric body 101, and may comprise an additional PCB 102b, in which a dipole is formed, the additional PCB 102b being connected to the balun 102a.

[0098] Also a first part 103a of a second radiating element 103 may be formed by the dielectric body 101, and a second part 103b (shown in FIG. 7) of the second radiating element 103 may be formed as separate part 103b, i.e., as a part 103b that is added onto the dielectric body 101. For instance, each of the one or more second radiating elements 103 may comprise a first part (e.g., patch) 103a formed by the dielectric body 101, and may comprise a second part (e.g., patch) 103b connected to the first part 103a.

[0099] In this respect, FIG. 7 shows that the second parts 102b and 103b of the one or more first radiating elements 102 and the one or more second radiating elements 103, respectively, may be formed, at least partly, by a further dielectric body 701. For instance, the second patch 103b and the additional PCB 102b may be formed, respectively, by the further dielectric body 701 (e.g., with one or more metal layers) of the antenna element 100. The further dielectric body 701 may be attached/connected to the dielectric body 101 (shown in the assembled state in FIG. 8).

[0100] A reason for not including all the components into the dielectric body 101 may be, for example, that the presence of the dipole (in FIG. 7 provided/defined in the additional PCB 102b) would complicate the molding and the etching of the dielectric body 101, and would thus increase production costs. The additional stacked patches 103b may further increase the bandwidth of the second array (e.g., the HB array), and may thus be considered if the bandwidth requirements are not possible to achieve with only one single patch 103a. A good alternative to minimize the number of components would be to merge all the additional parts 102b and 103b (e.g., LB dipole PCB 102b, and HB stacked patches 103b) into the further dielectric body 701, for instance, being another metallized plastic part.

[0101] In at least one embodiment, HB radiating elements 103 may be arranged side-by-side with respect to LB radiating elements 102 (see e.g., FIGS. 2-5). However, as shown in FIG. 9, illustrating an antenna element 100 according to at least one embodiment, it may also be possible to have them arranged along the same line, e.g., along the length of the antenna element 100.

[0102] Further, in at least one embodiment, the second feeding network 105 may be arranged in the bottom, i.e., the base plate 101a, whereas the first feeding network 104 is arranged in the one or more wall elements 101b, 101c, particularly the outer wall element(s) 101b (see e.g., FIGS. 2-5). This may be a preferred option when a number of columns of second radiating elements 103 is higher than a number of columns of first radiating elements 102 (a column being a set of radiating elements 102/103 arranged one after the other on a common axis, wherein the common axis is, in particular, directed across to the length of the base plate 101a, more particularly perpendicular to the length (longer side) of the base plate 101a; similarly a row of radiating elements 102/103 may be perpendicular to a column of radiating elements 102/103). However, for a situation, in which the number of columns of second radiating elements 103 is the same as the number of columns of first radiating elements 102, as in the antenna element of FIG. 9, it may be preferable to have the second feeding network 105 arranged in the one or more wall elements 101b, 101c, particularly outer wall element(s) 101b, and/or the first feeding network 104 in the base plate 101a.

[0103] In at least another embodiment, a third frequency band may be added coexisting in the same dielectric body 101. For instance, FIG. 10 shows an antenna element 100 according to at least one embodiment, which builds on the antenna element(s) described with respect to FIGS. 2-5. Same elements in FIG. 10 and FIGS. 2-5 are provided with the same reference signs, and may be implemented likewise. In particular, FIG. 10 shows a triple-band antenna element 100. The antenna element 100 comprises one or more third radiating elements 1000 configured to radiate in a third frequency band (higher than the first and the second frequency band, or lower than the first and the second frequency band, or between the first and the second frequency band). The antenna element 100 may also comprise a third feeding network connected to the one or more third radiating elements 1000, for operating the one or more third radiating elements 1000 as a third antenna array. The third feeding network may be formed, at least partly, as a metal layer on the dielectric body 101, for instance, on the one or more wall elements 101b, 101c like the first and second feeding networks 104 and 105 described above.

[0104] Moreover, in other embodiments, different combinations of HB/LB radiating element columns could be considered. For instance, in FIGS. 11-13 some examples are depicted. In particular, FIG. 11 shows an exemplary antenna element 100 according to at least one embodiment with a 2LB/4HB combination, i.e., each of LB columns includes two LB radiating elements 102, and each of HB columns includes four HB radiating elements 103. FIG. 12 shows an exemplary antenna element 100 according to at least one embodiment with a 1LB/3HB combination, i.e., each of LB columns includes one LB radiating element 102, and each of HB columns includes three HB radiating elements 103. FIG. 13 shows an exemplary antenna element 100 according to at least one embodiment with a 1LB/4HB combination, i.e., each of LB columns includes one LB radiating element 102, and each of HB columns includes four HB radiating elements 103.

[0105] FIG. 14 shows a flow chart of a method 1400 according to at least one embodiment. The method 1400 may be used to fabricate the antenna element 100 described with respect to any of the previous figures.

[0106] The method comprises a step 1401 of forming a dielectric body 101 comprising a base plate 101a and one or more wall elements 101b, 101c arranged on the base plate 101a. Further, the method comprises a step 1402 of forming one or more first radiating elements 102 arranged on the base plate 101a, each first radiating element 102 being configured to radiate in a first frequency band, and a step 1403 of forming one or more second radiating elements 103 arranged on the base plate 101, each second radiating element 103 being configured to radiate in a second frequency band. Further, the method 1400 comprises a step 1404 of forming a first feeding network 104 connected to the one or more first radiating elements 102, for operating the one or more first radiating elements as a first antenna array, and a step 1405 of forming a second feeding network 105 connected to the one or more second radiating elements 103, for operating the one or more second radiating elements as a second antenna array. The first feeding network 104 is formed, at least partly, by metallizing the one or more wall elements 101b, 101c, in particular, one or more outer wall elements 101b and/or one or more inner wall elements 101c. The second feeding network 105 may be formed, at least partly, by metallizing the base plate 101a.

[0107] The foregoing descriptions are merely specific implementations of this application, but are not intended to limit the protection scope of this application. Any variation or replacement readily figured out by a person ordinarily skilled in the art within the technical scope disclosed in this application shall fall within the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the 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.