OMNIDIRECTIONAL HORIZONTALLY POLARIZED ANTENNA WITH HIGH CURRENT PROTECTION

Abstract

The disclosure is directed to an antenna assembly (1) comprising a horizontally polarized Vivaldi-type first antenna (5). The first antenna (5) comprises a horizontally polarized first radiator (6) extending in a horizontal plane (xy) having a flower-shaped outline comprising several tapered slots (7) arranged distributed around a radiator center (8). The first radiator (6) is horizontally (xy) extending with respect to the radiator center (8) in an outward direction. In vertical direction (z), the radiator extends by a certain thickness (t). A base plate (9) arranged at a certain distance below the radiator (6) interconnected to the radiator (6) by at least one post (10). A power divider (11) and a feeding stub (12) per tapered slot (7) are arranged between the base plate (9) and the first radiator (6). interconnected to the first radiator (6) for coupling radio signals into the first radiator (6).

Claims

1. An antenna assembly (1) comprising: a. a horizontally polarized Vivaldi-type first antenna (5) comprising a horizontally polarized first radiator (6) extending in a horizontal plane (xy) having a flower-shaped outline comprising several tapered slots (7) arranged distributed around a radiator center (8) and i. horizontally (xy) extending with respect to the radiator center (8) in an outward direction and ii. vertically (z) extending perpendicular to the horizontal plane (xy) by a certain thickness (t), b. a base plate (9) arranged at a certain distance below the first radiator (6) interconnected to the first radiator (6) by at least one post (10); and c. a power divider (11) and a feeding stub (12) per tapered slot (7) are arranged between the base plate (9) and the first radiator (6), interconnected to the first radiator (6) for coupling radio signals into the first radiator (6).

2. The antenna assembly (1) according to claim 1, wherein the first radiator (6) is made from solid metal.

3. The antenna assembly (1) according to claim 1, wherein the first radiator (6) is essentially plate-shaped.

4. The antenna assembly (1) according to claim 1, wherein the first radiator (6) is designed omnidirectional.

5. The antenna assembly (1) according to claim 1, wherein the several tapered slots (7) are arranged evenly distributed around the radiator center (8).

6. The antenna assembly (1) according to claim 1, wherein the tapered slots (7) are arranged in radial outward directions with respect to the radiator center (8).

7. The antenna assembly (1) according to claim 1, wherein the power divider (11) and the feeding stub (12) are arranged as at least one electrical conductor (19) on a printed circuit board (13).

8. The antenna assembly (1) according to claim 1, wherein the power divider (11) and the feeding stub (12) are attached to the bottom of the first radiator (6).

9. The antenna assembly (1) according to claim 1, wherein the power divider (11) has a star like design starting from the radiator center (8) of the first radiator (6) and comprising several branches (18) and wherein the feeding stubs (12) are curved in a forward direction from an outer end of each branch (18) and extend across a tapered slot (7) arranged in a coupling distance from each feeding stub (12).

10. The antenna assembly (1) according to claim 1, wherein the at least one post (10) is electrically galvanically interconnected to the first radiator (6) suitable to receive a high current from a catenary line of a railway track.

11. The antenna assembly (1) according to claim 1, wherein a feeding cable (14) extends at least partially through the first radiator (6).

12. The antenna assembly (1) according to claim 11, wherein the feeding cable (14) is arranged at least partially in a trench (15) of the first radiator (6).

13. The antenna assembly (1) according to claim 1, wherein a feeding cable (14) extends at least partially through the at least one post (10).

14. The antenna assembly (1) according to claim 11, wherein the feeding cable (14) is interconnected to the power divider (11) by a connector (16) arranged at least partially in the first radiator (6).

15. The antenna assembly (1) according to claim 14, wherein the connector (16) is arranged in the radiator center (8).

16. The antenna assembly (1) according to claim 1, wherein the base plate (9) encompasses a hollow space (22).

17. The antenna assembly (1) according to claim 1, comprising an omnidirectional vertically polarized second antenna (20) with at least one omnidirectional vertically polarized second radiator (21).

18. The antenna assembly (1) according to claim 17, wherein the second radiator (21) is cup-shaped.

19. The antenna assembly (1) according to claim 17, wherein the second radiator (21) is arranged vertically above and/or below and/or horizontally next to the first radiator (6).

20. The antenna assembly (1) according to claim 17, wherein the second radiator (21) is arranged on the same base plate (9) as the first radiator (6).

21. The antenna assembly (1) according to claim 17, wherein the first and the second antenna (5, 20) are interconnected to each other by a rat-race hybrid coupler and/or a magic-tee hybrid coupler.

22. An antenna assembly (1) comprising: an omnidirectional horizontally polarized first antenna (5) and an omnidirectional vertically polarized second antenna (20) wherein the first and the second antenna (5, 20) are interconnected to each other by a microwave device (24) comprising a first signal input (25) and a second signal input (26) and a first signal output (27) and a second signal output (28) with the following properties: a. the microwave device (24) is dividing i. a first signal received by the first signal input (25) equally and in-phase between the first and the second signal output (27, 28) and ii. a second signal received by the second signal input (26) equally but in counter-phase (i.e. out-of-phase, 180 degrees phase difference) between the first and the second signal output (27, 28); b. the microwave device (24) is reciprocal so the signals which are exiting the first and the second signal outputs (27, 28) are added in-phase at the first signal input (25) and in counter-phase at the second signal input (26).

23. The antenna assembly (1) according to claim 22, wherein the first (25) and the second (26) signal input are isolated from each other.

24. The antenna assembly (1) according to claim 22, wherein the microwave device (24) is a rat-race hybrid coupler and/or a mag-ic-tee hybrid coupler.

25. The antenna assembly (1) according to claim 22, wherein the first radiator (6) comprises leafs (17) which comprise a secondary slot (38) arranged with respect to the center (8) of the first radiator (6) in a radial direction.

26. The antenna assembly (1) according to claim 17, wherein the vertically polarized second radiator (21) of the second antenna (20) is arranged at least partially within the ground plot of the first radiator (6) of the first antenna (5).

27. The antenna assembly (1) according to claim 26, wherein the first radiator (6) comprises a recess (39) in which the second radiator (21) is arranged.

28. The antenna assembly (1) according to claim 27, wherein the recess (39) is designed such that the second radiator (21) is spaced a distance apart from the first radiator (6).

29. The antenna assembly (1) according to claim 22, wherein the horizontally polarized first antenna (5) comprises an impedance transformer (30).

30. The antenna assembly (1) according to claim 29, wherein the impedance transformer (30) is designed as a Klopfenstein transformer.

31. The antenna assembly (1) according to claim 29, wherein the impedance transformer (30) is arranged inside a depression (33) of the first radiator (6).

32. The antenna assembly (1) according to claim 22, wherein a GPS antenna module (40) is arranged in a depression of the first radiator (6).

Description

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0028] The herein described invention will be more fully understood from the detailed description given herein below and the accompanying drawings which should not be considered limiting to the invention described in the appended claims. The drawings are showing:

[0029] FIG. 1 shows a first antenna in a perspective view;

[0030] FIG. 2 shows a first variation of an antenna assembly comprising a first and a second antenna in a perspective view and partially sectionized;

[0031] FIG. 3 shows the first antenna in an exploded view from above;

[0032] FIG. 4 shows the first antenna in an exploded view from below;

[0033] FIG. 5 shows a second variation of an antenna assembly in a perspective view;

[0034] FIG. 6 shows a third variation of an antenna assembly in a perspective view;

[0035] FIG. 7 shows schematically a hybrid coupler device;

[0036] FIG. 8 shows a fourth variation of an antenna assembly in a perspective view;

[0037] FIG. 9 shows a fifth variation of an antenna assembly in a perspective view; and

[0038] FIG. 10 shows a detailed view of the fourth variation of FIG. 8

DETAILED DESCRIPTION OF THE INVENTION

[0039] Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.

[0040] FIG. 1 shows a variation of an omnidirectional horizontally polarized Vivaldi-type first antenna 5 in a perspective view. The hidden lines are shown as dashed lines. FIG. 2 shows a first variation of an antenna assembly 1 comprising a first antenna according to FIG. 1. FIG. 3 shows the first antenna 5 according to FIG. 1 in an exploded isometric view from above. FIG. 4 shows the first antenna 5 according to FIG. 1 in an exploded isometric view from below. FIG. 5 shows a second variation of an antenna assembly 1 comprising a first antenna according to FIG. 1. FIG. 6 shows a third variation of an antenna assembly 1 comprising a first antenna according to FIG. 1. FIG. 7 schematically shows a microwave device 24 as used in connection with the second aspect of the disclosure. FIG. 8 shows a fourth variation of the antenna and FIG. 9 shows a fifth variation of the antenna in a perspective manner from the front and above. FIG. 10 shows a sectional view of the fourth variation of the antenna (Detail D).

[0041] As e.g., visible in the perspective view of FIG. 1, an antenna assembly 1 according to a first aspect of the disclosure preferably comprises an omnidirectional horizontally polarized Vivaldi-type first antenna 5. The first antenna 5 comprises an omnidirectional horizontally polarized first radiator 6 arranged extending in an essentially horizontal plane (xy-plane) having an essentially flower-shaped outline with several leaves 17 separated from each other by tapered slots 7 arranged distributed around a radiator center 8. The tapered slots 7 are extending horizontally with respect to the radiator center 8 in an outward direction. Vertically, (z-direction) the tapered slots 7 are extending perpendicular to the horizontal plane (xy-plane) by a certain thickness (t). A base plate 9, which in FIG. 1 is only schematically indicated, is arranged in general parallel at a certain distance (b) below the radiator 6 and interconnected to the radiator 6 by at least one post 10. In the variation according to FIG. 1, the at least one post 10 is arranged at a leaf 17 to which it is attached by a bolt 29. A power divider 11 and, per tapered slot 7, a feeding stub 12 are arranged between the base plate 9 and the first radiator 6. They are electromagnetically coupled to the first radiator 6 for coupling radio signals into the first radiator 6. The first radiator 6 is preferably made from solid metal, such that it can withstand high currents easily as described herein above. Good results can be achieved, when the first radiator 6 is essentially plate-shaped as shown in the drawings. If appropriate, the first radiator may comprise at least one recess and/or opening on the inside as long as they do not have a negative impact on the performance. The several tapered slots 7 are preferably arranged evenly distributed around the radiator center 8. The tapered slots 7 are usually arranged in radial outward direction with respect to the radiator center 8. Depending on the field of application, other arrangements are possible as well. In a preferred variation, the power divider 11 and the feeding stubs 12 are arranged as at least one electrical conductor 19 on a printed circuit board 13 attached to the bottom of the first radiator 6. As e.g., visible in FIG. 3 and FIG. 4, the printed circuit board 13 may have a circular shape. Depending on the field of application, other designs are possible.

[0042] The at least one post 10 may be electrically galvanically interconnected to the first radiator 6 suitable to receive a high current from a catenary line of a railway track as mentioned herein above. A feeding cable 14 preferably extends at least partially through the first radiator 6. T hereby a compact and robust design with a low overall height may be achieved. The feeding cable 14 can at least partially be arranged in a trench 15 of the first radiator 6, In a preferred variation, the feeding cable 14 extends at least partially through the at least one post 10. The feeding cable 14 can be interconnected to the power divider 11 by a connector 16 arranged at least partially in the first radiator 6, Preferably, the power divider 11 and the feeding stub 12 are arranged as at least one electrical conductor 19 on a printed circuit board 13. Especially with respect to the high current protection, the power divider 11 and the feeding stub 12 are preferably attached to the bottom of the first radiator 6. As shown in the drawings, the power divider 11 may have a star like design starting from the center 8 of the radiator 6 and comprising several branches 18. Good results can be achieved, when the feeding stubs 12 are curved in a forward direction from an outer end of each branch 18 and extending across a tapered slot 7 arranged in a coupling distance from each feeding stub 12 and each tapered slot 7 end. Usually, the connector 16 is arranged in the radiator center 8. Far save connectivity, the connector 16 can be interconnected to the electrical conductor 19 by soldering.

[0043] Good results can be achieved, when the first antenna 5 is combined with an omnidirectional vertically polarized second antenna 20 with at least one omnidirectional vertically polarized second radiator 21. Preferably, the second radiator 21 is arranged on the same base plate 9 as the first radiator 6. In a preferred variation, the second radiator 21 is cup-shaped. Depending on the field of application, different arrangements are possible: The second radiator 21 can be arranged vertically above and/or below and/or horizontally next to the first radiator 6. The base plate 9 may encompass a hollow space suitable to receive a cabling for the several elements of the antenna assembly 1. To obtain a dual slant antenna, the first 5 and the second antenna 20 may be interconnected to each other by microwave device as schematically shown in FIG. 7. Good results can be achieved by a microwave device 24 in form of a rat-race hybrid coupler and/or a magic-tee hybrid coupler.

[0044] In the fourth variation according to FIG. 8 and FIG. 10 and fifth variation according to FIG. 9 of the antenna assembly 1 both horizontally as well as vertically polarized first and second antennas 5, 20 are integrated. In comparison to the variations described above, the first antennas 5 are considerably bigger to also cover low frequency bands, such as e.g., 5G 700 MHZ band. The housings 22 are shown in an unfolded state above the base plate 9. In FIG. 8, the first radiator 6, the printed circuit board 13, as well as certain posts 10 in the front of the drawing are shown in a section view to offer better visibility on the structure underneath. The feeding stub 12 which is normally arranged underneath the printer circuit board 13 is shown uncut.

[0045] Each first radiator 6 is preferably fed using an electric conductor 19 in the form of a microstrip line 19, which is printed on the printed circuit board 13 which is placed on the bottom side of the Vivaldi radiator 6. The microstrip lines 19 are fed using a power divider/combiner 11 as mentioned herein above in more detail. The power divider 11 input is connected to a feeding cable 14, which in the shown variation is embedded inside the Vivaldi radiator 6. The feeding cable 14 is not directly connected to the power divider 11 on the bottom side of the first radiator 6. Instead, it is first connected by a coaxial connector 16 to an impedance transformer 30. As best visible in FIG. 10, in the shown variation, the impedance transformer 30 is designed as an electric conductor 31 arranged on a printed circuit board 32 which is arranged in a depression 33 on the upper side of the first radiator 6. In the center area of the first radiator 6 the impedance transformer 30 is interconnected to the power divider 11 arranged on the bottom side of the first radiator 6 by a connector 34 arranged in a bore 35 of the first radiator 6. The connector 34 comprises a connection pin 36 surrounded by a sleeve 37 made from a dielectric material. The advantage of an impedance transformer 30 is that the input impedance of the power divider 11 is comparatively low (in the range of 20-30 Ohm) due to the fact that several Vivaldi feeding stubs 12, in the shown variation five, are connected in parallel to the power divider 18 output. Also, the connection pin 34 and the sleeve 35 arranged inside the Vivaldi radiator 6 are preferably matched to this low impedance. The impedance transformer 30 is preferably adapted to the standard 50 Ohm impedance which is used in the coaxial adapter and coaxial cable. Good results can be achieved when the impedance transformer 30 is designed as so-called “Klopfenstein transformer”. However, any other design of impedance transformer (quarter-wavelength, multi-section, Chebyshev, maximally-flat, exponential, etc.) would be applicable if it fulfills performance and bandwidth requirements.

[0046] In the “leafs” of the first radiator 6 additional secondary slots 38 are integrated in order to mitigate the mutual coupling between single, neighboring first radiators 6. The secondary slots extend in radial direction with respect to the center 8 of the first radiator 6. This may improve the overall matching of the horizontally polarized radiator.

[0047] To safe space the vertically polarized second radiator 21 of the second antenna 20 is arranged at least partially within the ground plot of the first radiator 6 of the first antenna 5. In view of the often limited height and the need to eliminate the detuning of the vertically polarized radiator by the proximity of the Vivaldi first radiator leafs 17, the herein shown fourth and fifth variations comprise a recess 39 in at least one leaf 17. The recess 39 is designed such that it is spaced a distance apart from the cup-shaped second radiator 21. Good results can be obtained when no post 10 supports the respective leaf 17 with the recess 39 in order not to influence the vertically polarized radiator RF performance.

[0048] If appropriate a GPS antenna module 40 can be integrated in the antenna assembly 1. In the shown variation, there are two possible options for positioning the GPS antenna module 40. It can be either integrated in the antenna baseplate 9 or in a respective recess 41 in a leaf 17 of the first radiator 6. Integrating the GPS antenna module in the baseplate 9 is simpler from the mechanical point of view but some part of the module field of view is covered by the other elements. This might limit the GPS signal reception performance. An alternative solution is to mount the GPS antenna module 40 at less restricted position. The GPS antenna module 40 is preferably arranged such that it does not protrude above the top surface of first radiator 6. This is still to provide high current protection to the GPS antenna module 40. If the top surface of GPS antenna module 40 is below the top surface of the first radiator 6, a damaged catenary line will stop on the first radiator 6 which is well grounded as described above.

[0049] The variation according to FIG. 9 is optimized to fit an existing antenna platform. The horizontally polarized first radiator 6 is adjusted in order to fit into a smaller housing 22. Therefore, some sections of the Vivaldi radiator leafs 17 have been removed. Also, the height of the posts 10 was reduced. The resulting antenna assembly 1 is more compact and uses existing elements.

[0050] The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.