Satellite antenna

Abstract

A satellite antenna comprises an electrically conductive base plate, above which an electrically conductive structure is arranged, containing a ring conductor with a central point. The ring conductor is electrically connected to vertical radiators, and each vertical radiator is capacitively coupled to the base plate at a coupling point.

Description

[0001] The invention relates to satellite antennas, particularly for GNSS and SDARS applications in the automotive sector. Typically, such antennas are circularly polarized, and their preferred radiation direction is in the zenith region. Existing satellite antenna solutions for automotive applications usually have the characteristic that they only cover a narrow frequency range of approximately 50 MHz (for example, for GNSS applications) with sufficiently good performance (gain, axial ratio, etc.). This is due to the limited space available in typical automotive installation situations (shark fins, concealed systems, etc.) but also to the frequency range of the data bands to be covered (GNSS: L5 & L2 bands from 1.16–1.25 GHz and L1 & L2 bands from 1.525–1.61 GHz; SDARS: 2.32–2.345 GHz). Such solutions are typically intended to transmit and receive primarily above the horizon and, in particular, in the direction of the zenith.Therefore, these antennas are usually implemented with an electrically conductive base plate beneath the actual antenna structure, which ensures that the antenna pattern is directed only into the hemisphere above the horizon or that the antenna pattern is reflected there from the base plate.

[0002] The disadvantage of this is that this measure limits the usable frequency range of the antenna to approximately the aforementioned 50 MHz bandwidth. Due to the narrow bandwidth and the associated need for high quality, such antennas are also comparatively expensive and not robust against external influences.

[0003] EP 2 721 690 B1, DE 10 2016 207434 A1, DE 10 2010 035932 A1, DE 10 2016 010200 A1, US 2003 / 174098 A1, and WO 2022 / 078604 A1 disclose a satellite antenna comprising a ring conductor with a center electrically connected to vertical radiators, wherein the vertical radiators are each capacitively coupled to the base plate at a coupling point and at least one coupling point is connected to an antenna connection for feed-in.

[0004] The object of the present invention is to create a satellite antenna with improved bandwidth, which has a compact design and can be manufactured cost-effectively.

[0005] This problem is solved by the features of claim 1. Advantageous embodiments of the invention are described in the description, the drawing and the dependent claims.

[0006] In a first advantageous embodiment, the ring conductor can be configured as a regular polygon, with the vertical radiators arranged centrally between the corners of the ring conductor. In contrast to conventional satellite antennas, where the vertical radiators are arranged in the center or at the corners of a usually square ring conductor, the corners of the ring conductor in this embodiment are freely oriented in space. The polygon can be configured as a square, rectangle, hexagon, or other regular polygon, with the vertical radiators in all cases being arranged, in particular, centrally between two adjacent corners of the ring conductor.

[0007] The arrangement of the vertical emitters between two corners of a ring conductor, as described above, makes it possible to fold the corners of the ring conductor towards its center or (relative to the base plate) to bend them upwards and fold them inwards. According to a further advantageous embodiment, this allows a ring conductor to be designed that is cross-shaped in plan view or that encloses a cross-shaped area.

[0008] In such embodiments, the ring conductor has several branches with parallel track sections in which the opposing current components largely cancel each other out in each branch.

[0009] According to a further advantageous embodiment, the ring conductor can be inclined at least in sections with respect to the base plate and, in particular, can be dome-shaped. This allows the antenna geometry to be well adapted to a radome contour above the antenna.

[0010] According to a further advantageous embodiment, at least one vertical radiator can be slotted and, in particular, have two parallel, spaced-apart legs. Such a slot can originate from the ring radiator and extend to the coupling point or even into a feed pad of the coupling point. The current components running in opposite directions on the resulting parallel legs of the vertical radiators render these vertical legs virtually "electrically invisible." The electrical connection path between the feed feet is lengthened, so that, with the same given installation volume, the resulting antenna can be used at lower frequencies.

[0011] According to a further advantageous embodiment, at least one vertical emitter can be U-shaped. In this embodiment, the vertical emitter also has two parallel, spaced-apart legs, which are connected at their underside by a crossbar that can be attached to the coupling point.

[0012] According to a further advantageous embodiment, at least one vertical emitter can be angled at an obtuse angle at its end furthest from the coupling point in order to optimize the installation volume. The vertical emitter can be angled towards the center or away from the center.

[0013] According to a further advantageous embodiment, the ring conductor can have sections extending orthogonally to the base plate, and these sections can connect, in particular, to sections of the ring conductor extending parallel to the base plate. This design allows for the realization of satellite antennas that are significantly taller than they are wide compared to conventional solutions, resulting in a monopole-like geometry. Nevertheless, unlike a monopole antenna, such an antenna is circularly polarized, and its main beam direction is predominantly towards the zenith or omnidirectional (in the upper hemisphere). This design significantly reduces the space required in the horizontal dimension, allowing several such antennas to be positioned side by side in a space-saving and flexible manner. This opens up new design possibilities for the realization of complex multi-antenna systems in confined spaces.

[0014] In a further advantageous embodiment, the ring conductor can have sections extending orthogonally to the base plate, each transitioning into a vertical radiator. This, too, can contribute to a very slim and space-saving design of the satellite antenna. The same applies to another advantageous embodiment in which the ring conductor is angled multiple times, for example, eight times by 90°. It can also be advantageous if the ring conductor transitions coplanarly into the vertical radiators.

[0015] According to a further aspect of the present invention, the ring conductor can be replaced by two dipoles, in particular intersecting ones, each connected at its end to a vertical radiator. Such a satellite antenna differs from a conventional satellite antenna, which comprises a ring conductor connected to capacitive coupling surfaces via vertical radiators. Of the four coupling surfaces typically used, one or two are usually fed, thereby generating a circular excitation of the antenna. Hereinafter, only the excitation at two coupling surfaces is considered. By electrically shifting the excitations by 90°, a circular radiation pattern is achieved. In this case, one excited coupling surface and the opposite coupling surface each form a "sub-radiator" (the other two coupling surfaces form a further sub-radiator, which is positioned geometrically orthogonal to the first sub-radiator).With correct dimensioning, both subradiators are almost ideally decoupled from each other, even though they are galvanically connected to each other by a ring or by a galvanic contact in the center.

[0016] In the embodiment with two dipoles instead of a ring conductor, the ring is, so to speak, progressively reduced in size, so that it is reduced to a central connection point in the middle of the sub-radiators. This creates a capacitively fed crossed dipole, which consists, for example, of two dipole sub-radiators galvanically coupled in the middle. Such an antenna can also be used as a satellite antenna. Since there is no longer a ring structure, other antennas (e.g., adjacent 5G antennas or Wi-Fi antennas, etc.) can be positioned from all four sides within close proximity of the central connection point of this antenna.

[0017] Such an antenna thus offers additional possibilities for new antenna positions and geometries. It is more flexible in design than a conventional ring-type antenna, as a ring structure is no longer required. The struts to the central connection point, as well as the vertical position of the central connection point, can be designed almost arbitrarily, making it possible to smoothly adapt the shape of the antenna, for example, to a round / convex radome over the antenna. Since the bandwidth of such an antenna is typically proportional to approximately the volume enclosed by the antenna structure, this enables very efficient bandwidth utilization of a given installation space.

[0018] As described above, the two dipoles can be galvanically coupled at their intersection. However, according to a further advantageous embodiment, it is also possible to galvanically isolate the two dipoles at their intersection. This results in two completely galvanically separated, capacitively fed dipoles. This embodiment offers the possibility of further, novel antenna positioning. The separated dipole arms can be arranged in a T-shape or a V-shape, or, according to another embodiment, positioned completely separately from one another. Maintaining the orthogonal alignment of the individual dipoles can be advantageous for good polarization purity. Despite these extreme positioning, good functionality as a complete antenna with two sub-radiators is still ensured. The separated dipoles can be manufactured as a single unit, which represents an additional manufacturing advantage.

[0019] According to a further aspect of the present invention, in an embodiment with a ring conductor in the immediate vicinity of the ring conductor, particularly above the ring conductor, a second ring conductor is arranged which is not galvanically coupled to the electrically conductive structure. Similarly, in the case of a patch antenna, the ring conductor can be arranged above the patch antenna, particularly in its immediate vicinity.

[0020] Adding a closed, conductive ring in the immediate vicinity of the antenna multiplies its usable bandwidth (typically to several hundred MHz), thus enabling a very robust and broadband antenna solution. With appropriate dimensioning, the entire GNSS frequency range, as well as the intermediate range of 1.16–1.61 GHz, can be covered with a virtually frequency-independent antenna.

[0021] The additional ring can be positioned particularly close to the antenna (for example, a few millimeters above the antenna).

[0022] The additional ring conductor is not galvanically coupled to the main antenna structure. This can be achieved mechanically, for example, by integrating the additional ring conductor as a metal structure into a cover over the antenna (radome) or by applying it as a foil with a conductor structure to or within the antenna. The additional ring conductor can also be integrated into an existing support. Furthermore, the additional ring conductor can be used to focus the antenna pattern in specific preferred directions. This makes it possible to shift the main beam direction of the antenna from the zenith towards the horizon, if desired. This property of the additional ring conductor depends on its dimensions.

[0023] The conductor width of the ring structure influences the usable bandwidth of the antenna: a wider conductor width enables higher antenna bandwidths and even more robust performance than a narrower conductor width. The ring can be dimensioned so that the frequency at which the wavelength just fits onto the ring (hereinafter referred to as the "ring natural frequency") is... f eig (called), lies within or near the area of ​​the service band to be covered. This means that the mean or electrical length l m of the ring just the condition l m = λ eig = c f eig must suffice. This is λ eig the wavelength at the ring natural frequency and c is the propagation speed of the wave on the ring (in air this corresponds to the speed of light) c0). If the ring's natural frequency lies above the usable band, the antenna pattern is concentrated towards the zenith. If the ring's natural frequency lies below the usable band, it becomes possible to shape the antenna pattern in a more monopolistic manner (main beam direction near the horizon). This is atypical for such satellite antennas, but this configuration is made possible by the additional ring.

[0024] The distance between the ring and the electrically conductive structure must be chosen so that the ring is located in the near field of the antenna. Typically, for the given frequency ranges, this is a distance in the millimeter range.

[0025] The main advantage of adding a ring antenna above an existing loop antenna (or patch antenna) is that the additional resonance of the added ring, coupled with the coupling to the antenna below, broadens the area of ​​very good matching for the original antenna. This increased area of ​​very good matching then significantly increases the usable bandwidth of the antenna.

[0026] According to another advantageous embodiment, it can be advantageous if the ring conductor of the satellite antenna and the second ring conductor have the same geometric shape, for example, both being designed as a square or rectangle.

[0027] According to a further aspect of the present invention, it relates to an antenna arrangement comprising at least two satellite antennas of the type described above, each having a ring conductor, and whose ring conductors overlap each other in a top view. With such an antenna arrangement, several satellite antennas of the type described above can be nested within one another (e.g., to cover GNSS-L1 and GNSS-L2 simultaneously). In this case, the influence of an outer ring conductor on an inner ring conductor is reduced. The antenna pattern of the inner ring conductor is less affected (thereby improving, in particular, the gain of the inner ring towards the zenith), and the isolation between the rings is more favorable. Thus, this embodiment offers the possibility of improving the overall antenna performance of a combined antenna arrangement. This opens up new embodiments.Several such antennas – or even conventional satellite antennas – can be stacked inside each other in a completely three-dimensional way, like in a shell model.

[0028] This enables compact antenna designs and flexible positioning of the feed surfaces (even nested within each other). The antennas can also be nested thanks to the flexible positioning of the capacitive coupling surfaces.

[0029] The present invention is described below by way of example with reference to various embodiments and the accompanying drawings. These show: Fig. 1 a perspective view of a satellite antenna in which the corners of the ring conductor are folded towards the center; Fig. 2 a perspective view of a satellite antenna in which the vertical radiators are slotted; Fig. 3 a perspective view of a satellite antenna in which the ring conductor has sections extending orthogonally to the base plate; Fig. 4 a perspective view of a satellite antenna in which the ring conductor is replaced by two intersecting dipoles; Fig. 5 a perspective view of a satellite antenna with two intersecting dipoles that are not galvanically connected; Fig. 6 a perspective view of a satellite antenna with two non-intersecting dipoles; Fig. 7 a perspective view of an antenna arrangement with several nested satellite antennas; and Fig.8. A perspective view of a satellite dish showing a first ring conductor and a second ring conductor.

[0030] In the following description of different embodiments, the same reference numerals are used for identical components.

[0031] Fig. 1 Figure 1 shows a first embodiment of a satellite antenna comprising an electrically conductive base plate 10 above which an electrically conductive structure is arranged. This structure includes a ring conductor 12 with a center Z, which is electrically connected to vertical radiators 14. In the illustrated embodiment, four vertical radiators 14 are provided, each capacitively coupled at its lower end to the base plate 10 via a coupling point 16 and a dielectric (not shown). At two adjacent coupling points 16, the illustrated embodiment provides a feed pad 18 for power input, which can be connected to an antenna connector (not shown).

[0032] At the in Fig. 1 In the illustrated embodiment, the ring conductor 12 is cross-shaped in plan view, and its conductor track also encloses a cross-shaped area. Conceptually, the ring conductor 12 is formed from a square whose four corners are folded towards the center Z, or rather, folded upwards and inwards. In other words, the ring conductor 12 forms a symmetrical cross in plan view, the four legs of which are slotted starting from the center Z. Thus, the ring conductor 12 is composed of a total of four U-shaped sections, each U having two parallel legs that are connected to each other in the region of the center Z. The lower transverse leg of each U is connected to a vertical radiator 14, the vertical radiators 14 being angled obtusely at their ends furthest from the coupling point 16 or the base plate 10. Fig. 1 As illustrated, the ring conductor 12 is inclined in sections with respect to the base plate 10. In the area of ​​the center Z, sections of the ring conductor 12 run parallel to the base plate 10, and inclined sections of the ring conductor 12 adjoin these sections, which are connected at their lower ends to the vertical radiators 14.

[0033] The described shape of the ring conductor 12 is made possible by arranging the vertical emitters 14 centrally between the corners of the ring conductor 12 before its corners are folded towards the center Z. However, it is also possible to arrange the vertical emitters in the region of the inner, upper corners of the ring conductor, close to the center.

[0034] Fig. 2 Figure 1 shows another embodiment of a satellite antenna whose ring conductor 22 has a square shape, with vertical radiators 24 arranged approximately midway between the four corners of the ring conductor 22. In this embodiment, all four vertical radiators 24 are slotted and have the shape of an upwardly open U, which has two parallel legs 24a and 24b connected to each other by a crossbar 24c that contacts the coupling point 16.

[0035] Fig. 3 Figure 1 shows another embodiment of a satellite antenna that has a monopole-like geometry. In this embodiment, the ring conductor 32 has the same shape in an unwound plan view as the ring conductor 12 of the embodiment shown in Figure 2. Fig. 1 However, in the embodiment of Fig. 3 The ring conductor 32 is bent a total of eight times by 90°. This results in the ring conductor 32 having a total of four sections 32a extending orthogonally to the base plate 10, each U-shaped and connected at its underside to a vertical radiator 34. At the top of the U, each leg of a U-shaped section 32a connects to an L-shaped section 32b angled at 90° and extending parallel to the base plate 10.

[0036] How Fig. 3 To illustrate, the sections 32a extending orthogonally to the base plate 10 transition coplanarly into a vertical radiator 16 at their underside or at their lower edge.

[0037] Fig. 4 Figure 1 shows another embodiment of a satellite antenna in which the ring conductor has been conceptually reduced to a single central connection point. This creates a capacitively fed crossed dipole, formed from two intersecting dipoles 42 and 43. The two dipoles 42 and 43 are orthogonal to each other and intersect at the center Z, with each dipole 42 and 43 connected at its two outer ends to a vertical radiator 44. Both dipoles 42 and 43 run parallel to and spaced apart from the base plate 10.

[0038] Fig. 5 shows a to Fig. 4 similar embodiment, which differs from the one in Fig. 4 The illustrated embodiment differs in that the two dipoles 52 and 53 are galvanically isolated. In this embodiment, the two dipoles 52 and 53 are designed as separate conductors, each of which has a U-shaped bend in the center, so that the two dipoles 52 and 53 do not touch each other.

[0039] Fig. 6 Figure 1 shows another embodiment of a satellite antenna with two dipoles 62 and 63, each electrically connected at its ends to vertical radiators 64. The two dipoles 62 and 63 are orthogonal to each other, but do not cross and are thus arranged in an L-shape above the base plate 10. Both dipoles 62 and 63 can be tapered in their middle third.

[0040] Fig. 7 Figure 1 shows an antenna arrangement with a total of three nested satellite antennas whose ring conductors overlap each other. A first satellite antenna with a square ring conductor 22' is arranged above the base plate 10, the vertical radiators 24' of which are positioned centrally between the corners of the ring conductor 22'.

[0041] A second satellite antenna is arranged within the ring conductor 22' of the first satellite antenna, the ring conductor 12' of which is connected in the same way as the ring conductor 12 of the exemplary embodiment of Fig. 1 The vertical radiators 14' of this satellite antenna are, however, bent obtusely outwards at their upper end, so that they and thus also the ring conductor 12' cover the ring conductor 22' of the first satellite antenna.

[0042] Finally, inside and below the first and second satellite antennas, a third satellite antenna with an approximately square ring conductor 72 is arranged, which is also connected to four vertical radiators.

[0043] Fig. 8 Figure 1 shows another embodiment of a satellite antenna with a square ring conductor 82 arranged parallel to a base plate 10. In the region of the four corners of the ring conductor 82, it is connected to vertical radiators 84, which, as in the embodiments described above, are capacitively coupled to the base plate 10, wherein two of the vertical radiators 84 in turn have a coupling point 18 for feeding into an antenna connection.

[0044] In this embodiment, a second ring conductor 83 is arranged slightly above the first ring conductor 82, but it is not galvanically coupled to the electrically conductive structure consisting of the first ring conductor 82 and the vertical radiators 84. Both ring conductors 82 and 83 have the same geometric shape, with the second ring conductor 83 having slightly narrower traces and projecting beyond the outer contour of the first ring conductor 82. The second ring conductor 83 is secured in its position by means of fasteners (not shown). Fig. 8 The position shown was maintained.

[0045] In the embodiments described above, all ring conductors can be manufactured in a known manner, for example, as stamped and bent parts. The capacitive coupling to the base plate and the connection to an antenna connector are also carried out in a manner known to those skilled in the art.

Claims

1. A satellite antenna comprising an electrically conductive base plate (10) above which an electrically conductive structure is arranged that comprises a ring conductor (12, 12', 22, 22', 32, 72, 82) having a center (Z) which is electrically conductively connected to vertical radiators (14, 14', 24, 24', 34, 44, 54, 64, 84), wherein the vertical radiators (14, 14', 24, 24', 34, 44, 54, 64, 84) are each capacitively coupled to the base plate (10) at a coupling point (16) and at least one coupling point (18) is connected to an antenna terminal for feeding, wherein the ring conductor (12, 12', 22, 22', 32, 72, 82) is formed as a regular polygon, the vertical radiators (14, 14', 24, 24', 34) are centrally arranged between corners of the ring conductor (12, 12', 22, 22', 32, 72, 82) and the corners of the ring conductor (12, 12', 32) are folded in the direction of the center (Z).

2. A satellite antenna according to claim 1, characterized in that at least one vertical radiator (24) is formed as slit and in particular has two legs (24a, 24b) spaced apart in parallel.

3. A satellite antenna according to one of the preceding claims, characterized in that at least one vertical radiator (24) is U-shaped.

4. A satellite antenna according to any one of the preceding claims, characterized in that the ring conductor (12, 12') encloses a cross-shaped surface.

5. A satellite antenna according to any one of the preceding claims, characterized in that the ring conductor (12, 12') is at least sectionally inclined and in particular dome-shaped with respect to the base plate (10).

6. A satellite antenna according to any one of the preceding claims, characterized in that at least one vertical radiator (14, 14') is angled at an obtuse angle at its end remote from the coupling point.

7. A satellite antenna according to any one of the preceding claims, characterized in that sections (32a) of the ring conductor (32) extending orthogonally to the base plate (10) merge into a respective vertical radiator (34).

8. A satellite antenna according to any one of the preceding claims, characterized in that the ring conductor (32) merges in a coplanar manner into the vertical radiators (34).

9. An antenna arrangement comprising at least two satellite antennas according to at least one of the preceding claims whose ring conductors (12', 22', 72) overlap one another in a plan view.

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