Leaky Wave Antenna

Abstract

An antenna device (1) and an antenna stack (20) comprising at least two antenna devices are disclosed. The antenna device comprises a leaky wave antenna structure comprising a waveguide structure (2) extending in a first plane along a first axis (101), wherein the waveguide structure comprises two opposite end portions (3) along the first axis, and a first feed point and a second feed point arranged at opposite end portions of the waveguide structure. The antenna device further comprises a dispersive lens structure (6) having an edge extending along the waveguide structure in the first plane, the dispersive lens structure having an extension along a second axis (102) extending in the first plane in a second direction perpendicular to the first axis. The waveguide structure further comprises a plurality of discontinuities along an interface between the waveguide structure and the dispersive lens structure for leaking electromagnetic energy into dispersive lens structure.

Claims

1-14. (canceled)

15. An antenna device, comprising: a leaky wave antenna structure comprising: a waveguide structure extending in a first plane along a first axis, wherein the waveguide structure comprises two opposite end portions along the first axis; a first feed point and a second feed point arranged at opposite end portions of the waveguide structure; a dispersive lens structure having an edge extending along the waveguide structure in the first plane, the dispersive lens structure having an extension along a second axis extending in the first plane in a second direction perpendicular to the first axis; wherein the waveguide structure comprises a plurality of discontinuities along an interface between the waveguide structure and the dispersive lens structure for leaking electromagnetic energy into dispersive lens structure.

16. The antenna device of claim 15: wherein the dispersive lens structure is configured such that a first main beam direction associated with an excitation of a first feed point is at an angle θ±20% relative to the second axis; and wherein a second beam direction associated with an excitation of a second feed point is at an angle θ±20%, relative to the second axis.

17. The antenna device of claim 16, wherein the dispersive lens structure is in the form of an isosceles triangle having two angles γ, wherein the angles γ are equal to ±20%.

18. The antenna device of claim 15, wherein the dispersive lens structure is in the form of an isosceles triangle having two angles γ, wherein the angles γ are below a predefined threshold.

19. The antenna device of claim 15, wherein the dispersive lens structure is geometrically symmetric with respect to the second axis.

20. The antenna device of claim 19, wherein the dispersive lens structure forms a dispersive two-dimensional prism which is symmetric with respect to the second axis.

21. The antenna device of claim 15, wherein the dispersive lens structure comprises a metasurface.

22. The antenna device of claim 21, wherein the metasurface is a pin-type metasurface.

23. The antenna device of claim 15, wherein a length of the edge extending along the waveguide structure is substantially the same as a length of the waveguide structure along the first axis.

24. The antenna device of claim 15, wherein the dispersive lens structure comprises an integrated filter arrangement.

25. The antenna device of claim 15, wherein the waveguide structure comprises an integrated filter arrangement.

26. The antenna device of claim 15: wherein the waveguide structure is a gap waveguide; and the antenna device further comprising an Electromagnetic Band Gap (EBG) structure extending along the waveguide structure on an opposite side of the waveguide structure relative to the dispersive lens structure.

27. An antenna stack, comprising: at least two antenna devices, wherein each antenna device comprises: a leaky wave antenna structure comprising: a waveguide structure extending in a first plane along a first axis, wherein the waveguide structure comprises two opposite end portions along the first axis; a first feed point and a second feed point arranged at opposite end portions of the waveguide structure; a dispersive lens structure having an edge extending along the waveguide structure in the first plane, the dispersive lens structure having an extension along a second axis extending in the first plane in a second direction perpendicular to the first axis; wherein the waveguide structure comprises a plurality of discontinuities along an interface between the waveguide structure and the dispersive lens structure for leaking electromagnetic energy into dispersive lens structure; wherein the at least two antenna devices are stacked along a third axis substantially perpendicular to the first plane.

28. The antenna stack of claim 27: wherein the first feed point of each antenna device is connected to a first common feed point via a first switch arrangement; wherein the second feed point of each antenna device is connected to a second common feed point via a second switch arrangement; wherein the first switch arrangement is configured so that each first feed point is selectively and individually connectable to the first common feed point; and wherein the second switch arrangement is configured so that each second feed point is selectively and individually connectable to the second common feed point.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Further objects, features and advantages of embodiments of the invention will appear from the following detailed description, reference being made to the accompanying drawings, in which:

[0023] FIG. 1 is a schematic illustration of an antenna device according to an embodiment of the present invention.

[0024] FIG. 2 is a schematic illustration of the antenna device of FIG. 1 with an indicated beam path according to an embodiment of the present invention.

[0025] FIG. 3 is a schematic illustration of an excited antenna device according to an embodiment of the present invention.

[0026] FIG. 4 is a schematic illustration of an excited antenna stack according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0027] FIG. 1 is a schematic top-view illustration of an antenna device 1 according to an exemplary embodiment of the present invention. The antenna device 1 comprises a leaky wave antenna structure with a waveguide structure 2 extending in a first plane along a first axis 101. The waveguide structure 2 has two opposite end portions 3 along the first axis 101. In other words, the end portions 3 are arranged on opposite sides of a second axis 102 perpendicular to the first axis 101. The leaky wave antenna structure further has a first feed point 4 and a second feed point 5 arranged at a respective end portion 3 of the waveguide structure 2.

[0028] Further, the antenna device 1 comprises a (frequency) dispersive lens structure 6 having an edge extending along the waveguide structure 2 in the first plane. The dispersive lens structure 6 also has an extension along the second axis 102 extending in the first plane in a second direction perpendicular to the first axis 101. The waveguide structure 2 further has a plurality of discontinuities 7 along an interface between the waveguide structure 2 and the dispersive lens structure 6 for leaking electromagnetic energy into the dispersive lens structure 6. Stated differently, a leakage is introduced along the edge of the waveguide structure 2 facing the dispersive lens structure 6.

[0029] Moreover, the dispersive lens structure 6 can be understood as a two-dimensional (2D) lens, defined by the three outer edges which indicate the interfaces in which the leaky-mode (propagating in the waveguide structure 2) is dispersedly refracted, resulting in a frequency independent final radiation.

[0030] The dispersive lens structure 6 comprises a metasurface. Metasurfaces can be understood as materials that are designed to control the propagation of electromagnetic waves. They are generally formed as periodic structures to create a stop-band of the propagating waves in a certain frequency range and to allow propagation of the electromagnetic waves only along desired/defined directions. In this way, unwanted radiations, leakage and surface waves can be reduced, resulting in antenna structures that can be realized in a simpler and more cost effective way.

[0031] The dispersive lens structure 6 is in FIG. 1 illustrated in the form of a dispersive two-dimensional prism. The prism is symmetric with respect to the second axis 102. In more detail, the dispersive lens structure forms an isosceles triangle having a pin-type metasurface. The dispersive lens structure 6 may be realized in alternative ways, and may comprise periodic structures than the illustrated metal pins, such as e.g. an array of holes on a metal surface or an array of protrusions having other shapes than the illustrated pins Further, a length of the edge of the dispersive lens structure 6 extending along the waveguide structure 2 is substantially the same length as a length of the waveguide structure 2 along the first axis 101. Substantially the same length is in the context of the present application to be interpreted as exactly the same ±20% (of the total length), preferably exactly the same length ±15% (of the total length), or more preferably exactly the same length ±10% (of the total length).

[0032] Further, the waveguide structure 2 is in FIG. 1 illustrated in the form of a gap waveguide. The antenna device 1 further comprises an Electromagnetic Band Gap (EBG) structure 8 extending along the waveguide structure 2 on an opposite of the waveguide structure 2 relative to the dispersive lens structure 6. The EBG structure 8 serves the purpose of blocking electromagnetic radiation in the “back direction”, i.e. away from the dispersive lens structure 6. Moreover, EBG structures using high-symmetries are particularly suitable for mm-wave applications as they can achieve wide band-gaps and can be realized in a relatively simple way, for example by merely drilling holes in the metal surface. Thus, EBG structures are attractive for these frequencies where the dimensions are quite small and manufacturing techniques can be complex and expensive. However, as an alternative the antenna device 1 may comprise a solid metal wall arranged on an opposite side of the waveguide structure 2 relative to the dispersive lens structure 6 in order to block electromagnetic radiation in the “back direction”.

[0033] The waveguide structure 2 and/or the dispersive lens structure 6 may comprise an integrated filter (not shown). One possible filtering solution may for example be providing further discontinuities (e.g. drilling holes) in the waveguide structure 2. However, as mentioned the filtering means may be provided in other ways (e.g. by filtering in the EBG structure 8 or in the dispersive lens 6). The filtering characteristic may for example be controlled by controlling the a size and/or a position of the EBG structure 8 or the metasurface structures of the dispersive lens 6. Moreover, control of a radiation pattern characteristics can be implemented by varying the dimensions of the single row of square pins 7 (i.e. the discontinuities 7).

[0034] Still further, the antenna structure 1 is centre-symmetric (i.e. symmetric with respect to the second axis 102). The antenna structure 1 is capable of radiating energy in two directions, depending on which feeding point 4, 5 is used. This is further elucidated in FIG. 2.

[0035] FIG. 2 shows a top view illustration of the antenna device 1 from FIG. 1 where two radiation paths through and out of the antenna device 1 are indicated. In more detail, by feeding/exciting the antenna device 1 from the first feed point 4, the antenna device will radiate energy in a first direction (indicated by the arrow 9a). By feeding/exciting the antenna device from the second feed point 5, the antenna device will radiate energy in a second direction (indicated by the arrow 9b), different from the first direction. The radiation will have a maximum intensity at a defined angle ±θ.sub.1 (sign depends on feeding point/port) with respect to the second axis 102. According to an exemplary embodiment, the inclination angles 11, 12 of the lens structure 6 are substantially the same as the angles 10a, 10b between the second axis 102 and the direction of maximum radiation intensity 9a, 9b.

[0036] Stated differently, the prism design is made symmetric, with respect to second axis 102. Hence, beam-switching is enabled and thus electrical steerability in one plane (the first plane spanned by the first axis 101 and the second axis 102). One independent beam can radiate at each side of the prism 6, thus getting two beams 9a, 9b. The beams 9a, 9b can be arranged to radiate at the same angle 10a, 10b, but in “opposite” directions (for example +45 degrees and −45 degrees).

[0037] Even though, the dispersive lens structure 6 is illustrated in the form of an isosceles triangle in the figures, prisms of other geometrical shapes are feasible and within the scope of the present invention. For example, if triangular prisms are employed the inclination angles 11, 12 need not be the same, and the dispersive lens structure need not be symmetric with respect to the second axis 102.

[0038] Further, by having two feed points it provides for beam-switching capability by either feeding the antenna device from the first feed point 4 or the second feed points 5. Moreover, in order to adjust or control the radiation direction 9a, 9b one can adjust properties of the dispersive lens structure 6, either in terms of refractive properties, inclination angles 11, 12, or both. If the inclination angles 11, 12 are below a predefined threshold, a simultaneous excitation of both feed points 4, 5 of the waveguide structure 2 will result in a merging of the radiation patterns 9a, 9b and accordingly broadside radiation.

[0039] This is illustrated in FIG. 3, showing a top perspective view of an antenna device 1 according an exemplary embodiment of the present invention. Here, the inclination angles of the dispersive lens structure 6 are below a predefined threshold value, and both the first feed point 4 and the second feed point 5 are excited simultaneously, resulting in broadside radiation 9. In FIG. 3 the vertically opposite angles 11′, 12′ are indicated in the illustration for clarity reasons, however, as the skilled reader realizes, the vertically opposite angles 11, 12′ are equal to the inclination angles of the isosceles triangle forming the 2D prism of the dispersive lens.

[0040] FIG. 4 shows a perspective view of an antenna stack 20 according to an exemplary embodiment of the present invention. The antenna stack 20 has a plurality (only two are illustrated) antenna devices stacked along a third axis 203, substantially parallel to the first plane. Thus, the three axes can be said to form a three dimensional Cartesian coordinate system as illustrated by the three axes 201, 202, 203. The antenna stack 20 has a first common feed point 13a and a second common feed point 13b. The first feed point 4 of each antenna device in the antenna stack 20 is connected to the first common feed point 13a via a first switch arrangement (only schematically indicated by the bifurcated arrow). The second feed point 5 of each antenna device in the antenna stack 20 is connected to the second common feed point 13b via a second switch arrangement (only schematically indicated by the bifurcated arrow).

[0041] Each switch arrangement is configured so that each corresponding feed point 4 of each antenna device is selectively and individually connectable to the respective common feed point 13a. In other words, it is possible to choose which one of the plurality of antenna devices that is to be activated, and also by selecting a specific feed point one can also control the direction of the main beam 9a, 9b, 9c, 9d. The switching arrangement can be realized by any appropriate means as known in the art, such as e.g. by utilizing varactor diodes, mechanical switching, etc.

[0042] Further, in accordance with another exemplary embodiment, two or more of the antenna devices in the antenna stack 20 are identical. In that case, a one-dimensional (1D) 1D array configuration is obtained, which extends in the orthogonal direction from the first plane (i.e. the plane spanned by the first axis and the second axis). In more detail, in this configuration the beam can be steered by phase shifting the signals to each element (antenna device) in the 1D array (c.f. phased array operation), whereby beam-scanning in a plane orthogonal to the first plane is enabled.

[0043] Still further, the antenna stack 20 may comprise a stack configuration in which every other antenna device is identical, i.e. two directly adjacent antenna devices have different dispersive lens structures 6 (e.g. different inclination angles).

[0044] The present disclosure has been presented above with reference to specific embodiments. However, other embodiments than the above described are possible and within the scope of the disclosure. Thus, the different features of the embodiments may be combined in other combinations than those described.