SATELLITENANTENNE

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.

[0002] Existing satellite antenna solutions for automotive applications typically cover only a narrow frequency range of around 50 MHz (e.g., 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 fin, hidden systems, etc.) but also due to the frequency range of the bands to be covered (GNSS: L5 & L2 band from 1.16-1.25 GHz and L1 & L band from 1.525 - 1.61 GHz; SDARS: 2.32 - 2.345 GHz). Such solutions are typically designed to radiate and receive primarily above the horizon, particularly toward the zenith. Therefore, these antennas are usually implemented with an electrically conductive ground plate beneath the actual antenna structure, ensuring that the antenna pattern is directed solely into the half-space above the horizon.the antenna pattern is reflected there from the ground plane.

[0003] The disadvantage of this measure is that it limits the antenna's usable frequency range to approximately the aforementioned 50 MHz bandwidth. Due to the narrow bandwidth and the associated high quality required for such antennas, they are also comparatively expensive and not robust against external influences.

[0004] EP 2 721 690 B1, DE 10 2016 207 434 A1, DE 10 2010 035 932 A1, DE 10 2016 010 200 A1, and US 2003 / 174098 A1 disclose a satellite antenna according to the preamble of claim 1. WO 2022 / 078604 A1 discloses a mobile radio antenna with radiators. US 2008 / 0111757 A1 discloses an arrangement with dipole antennas. EP 1 751 821 B1 discloses a directional dipole antenna.

[0005] It is the object of the present invention to provide a satellite antenna with improved bandwidth, which has a compact design and can be manufactured cost-effectively.

[0006] This object is achieved by the features of claim 1. Advantageous embodiments of the invention are described in the description, the drawing and the subclaims.

[0007] According to the invention, a second ring conductor is arranged in the vicinity of the ring conductor, in particular above the ring conductor, which is not galvanically coupled to the electrically conductive structure.

[0008] By adding a closed, conductive ring in the near field of the antenna, its usable bandwidth is multiplied (typically to several hundred MHz), thus enabling a very robust and broadband antenna solution. With appropriate dimensioning, the entire GNSS frequency range and also the intermediate range from 1.16 to 1.61 GHz can be covered with a virtually frequency-independent antenna.

[0009] The additional ring is positioned close to the antenna (for example, a few millimeters above the antenna).

[0010] The additional ring conductor is not galvanically coupled to the actual antenna structure. This can be solved mechanically, for example, by enclosing the additional ring conductor as a metal structure in a cover above the antenna (radome) or by applying it as a foil with a conductor structure to or within the radome. The additional ring conductor can also be integrated into an existing holder. Furthermore, the additional ring conductor can be used to concentrate the antenna pattern in certain preferred directions. This makes it possible to shift the antenna's main beam direction from the zenith to the horizon, if desired. This property of the additional ring conductor depends on its dimensions.

[0011] The track width of the ring structure influences the usable bandwidth of the antenna: a wider track width enables higher antenna bandwidths and even more robust performance than a narrower track width. The ring can be dimensioned so that the frequency at which the wavelength just fits the ring (hereinafter "ring natural frequency") f eig (called), is in the range of or close to the useful 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 be sufficient. λ eig is the wavelength at the ring's 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 is above the useful band, the antenna pattern is concentrated toward the zenith. If the ring's natural frequency is below the useful band, it becomes possible to shape the antenna pattern in a more monopole fashion (main beam direction near the horizon). This is atypical for such satellite antennas, but such a design is made possible by the additional ring.

[0012] The distance between the ring and the electrically conductive structure should be chosen so that the ring is in the near field of the antenna. Typically, for the given frequency ranges, this is a distance in the millimeter range.

[0013] The main advantage of adding an additional loop over an existing loop antenna (or patch antenna) is that the additional resonance of the added loop and the coupling with the antenna below it broaden the range of very good matching for the original antenna. This increased range of very good matching then significantly increases the usable bandwidth of the antenna.

[0014] According to an advantageous embodiment, it may be advantageous if the ring conductor of the satellite antenna and the second ring conductor have the same geometric shape, for example both are designed as a square or rectangle.

[0015] According to a further advantageous embodiment, the ring conductor can be designed as a regular polygon, with the vertical radiators arranged centrally between the corners of the ring conductor. In contrast to conventional satellite antennas, in which the vertical radiators are arranged in the center or at the corners of a mostly square ring conductor, the corners of the ring conductor in this embodiment are freely exposed. The polygon can be designed as a square, rectangle, hexagon, or other regular polygon, whereby in all cases the vertical radiators can be arranged, in particular, centrally between two adjacent corners of the ring conductor.

[0016] The above-described arrangement of the vertical radiators between two corners of a ring conductor makes it possible to fold the corners of the ring conductor toward its center or, for example, to bend them upwards (relative to the base plate) and fold them inwards. According to a further advantageous embodiment, this allows the design of a ring conductor that is cross-shaped in plan view or that encloses a cross-shaped surface.

[0017] In such embodiments, the ring conductor has several branches with parallel track sections in which the opposing current components in each branch largely cancel each other out.

[0018] According to a further advantageous embodiment, the ring conductor can be inclined at least in sections relative 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.

[0019] 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. Due to the current components running counter to each other on the resulting parallel legs of the vertical radiators, these vertical legs become virtually "electrically invisible." The electrical connection path between the feed feet is extended, so that the resulting antenna can be used at lower frequencies with the same given installation space.

[0020] According to a further advantageous embodiment, at least one vertical radiator can be U-shaped. In this embodiment, the vertical radiator also has two parallel, spaced-apart legs, which are connected at their bottom by a crosspiece that can be connected to the coupling point.

[0021] According to a further advantageous embodiment, at least one vertical radiator can be angled at an obtuse angle at its end remote from the coupling point to optimize the overall volume. The vertical radiator can be angled toward the center or away from the center.

[0022] According to a further advantageous embodiment, the ring conductor can have sections that extend orthogonally to the ground plane, wherein these sections can in particular connect to sections of the ring conductor that extend parallel to the ground plane. This design enables the creation of satellite antennas that are significantly taller than they are wide compared to conventional solutions, resulting in a monopole-like geometry. However, unlike a monopole antenna, such an antenna is circularly polarized and its main beam direction is predominantly directed towards the zenith or omnidirectional (in the upper half-space). Such a design significantly reduces the space required in the horizontal dimension, allowing several such antennas to be positioned next to one another in a space-saving and flexibly manner. This opens up new design possibilities for the implementation of complex multi-antenna systems in confined spaces.

[0023] According to a further advantageous embodiment, the ring conductor can have sections extending orthogonally to the base plate, each of which transitions into a vertical radiator. This can also 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, 8 times at 90°. It can also be advantageous if the ring conductor transitions coplanarly into the vertical radiators.

[0024] According to an unclaimed aspect, the ring conductor can be replaced by two, in particular intersecting, dipoles, each connected to a vertical radiator at their ends. 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 one or two are fed, thereby generating a circular excitation of the antenna. Only the excitation at two coupling surfaces is considered below. Circular radiation is achieved by excitations electrically shifted by 90°. In this case, each excited coupling surface and the opposite coupling surface form a "sub-radiator" (the other two coupling surfaces form another sub-radiator, which is geometrically positioned orthogonally to the first sub-radiator).When correctly dimensioned, both sub-radiators are almost ideally decoupled from each other, although they are galvanically connected to each other by a ring or by a galvanic contact in the center.

[0025] In the (unclaimed) embodiment with two dipoles instead of a ring conductor, the ring is progressively reduced in size, so to speak, 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 center. 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 brought into close range of this antenna's central connection point from all four sides.

[0026] Such an antenna thus offers additional possibilities for new antenna positioning and geometries. It is more flexible in design than a conventional loop-guide antenna, as a ring structure is no longer required. The struts to the central connection point and the vertical position of the central connection point can be designed almost arbitrarily, making it possible to seamlessly adapt the antenna shape to, for example, a round / convex radome shell above the antenna. Since the bandwidth of such an antenna is typically proportional to the volume enclosed by the antenna structure, this enables very good bandwidth utilization of a given installation space.

[0027] As described above, the two dipoles can be galvanically coupled at an intersection point. However, according to a further advantageous embodiment, it is also possible to galvanically separate the two dipoles at an intersection point. This creates two completely galvanically separated, capacitively fed dipoles. This embodiment offers the possibility of further, new antenna positioning. The separated dipole branches can be arranged in a T-shape or a V-shape, or according to a further embodiment, positioned completely separately from one another, whereby it can be advantageous to maintain the orthogonal alignment of the individual dipoles for good polarization purity. Despite these extreme positionings, good function as an overall antenna with two sub-radiators is still ensured. The separated dipoles can be designed as identical parts, which represents an additional manufacturing advantage. l m = λ eig = c f eig

[0028] 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, both having a ring conductor, and whose ring conductors overlap one another in plan view. In such an antenna arrangement, several satellite antennas of the type described above can be placed inside one another (e.g., to cover GNSS-L1 and GNSS-L2 simultaneously). In this case, the influence of an inner ring conductor by an outer ring conductor is less. The antenna patterns of the inner ring conductor are less influenced (thereby improving, in particular, the gain of the inner ring towards the zenith), and the insulation between the rings is more favorable. This embodiment thus 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 placed inside each other completely three-dimensionally, like in a shell model.

[0029] This allows for compact antenna shapes and flexible positioning of the feed surfaces (even within each other). The flexible positioning of the capacitive coupling surfaces also allows for nested antennas.

[0030] The present invention will now be described purely by way of example using various embodiments and with reference to the accompanying drawings. In the drawings: Fig. 1 is a perspective view of a satellite antenna in which the corners of the ring conductor are folded towards the center; Fig. 2 is a perspective view of a satellite antenna whose vertical radiators are slotted; Fig. 3 is a perspective view of a satellite antenna in which the ring conductor has sections extending orthogonally to the base plate; Fig. 4 is a perspective view of a satellite antenna in which the ring conductor is replaced by two intersecting dipoles; Fig. 5 is a perspective view of a satellite antenna with two intersecting dipoles that are not galvanically connected to each other; Fig. 6 is a perspective view of a satellite antenna with two non-intersecting dipoles; Fig. 7 is a perspective view of an antenna arrangement with several nested satellite antennas; and Fig.8A perspective view of a satellite antenna having a first loop conductor and a second loop conductor. .

[0031] In the following description of various embodiments, the same reference numerals are used for the same components.

[0032] Fig. 1 shows a first embodiment of a satellite antenna having an electrically conductive base plate 10, above which an electrically conductive structure is arranged, comprising a ring conductor 12 with a center Z, which is electrically conductively connected to vertical radiators 14. In the illustrated embodiment, four vertical radiators 14 are provided, each of which is capacitively coupled to the base plate 10 at its lower end at a coupling point 16 via a dielectric (not shown). In the illustrated embodiment, a feed pad 18 for a feed is provided for two adjacent coupling points 16, which can be connected to an antenna connection (not shown).

[0033] In the 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 surface. Conceptually, the ring conductor 12 is formed from a square whose four corners are folded toward the center Z or folded upwards and inwards. In other words, the ring conductor 12 forms a symmetrical cross in plan view, whose four legs are slit 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 area of ​​the center Z. The lower transverse leg of each U is connected to a vertical radiator 14, the vertical radiators 14 being angled at an obtuse angle at their end remote from the coupling point 16 or the base plate 10. Fig. 1 As illustrated, the ring conductor 12 is designed to be inclined in sections relative 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 these sections are adjoined by inclined sections of the ring conductor 12, which are connected at their lower ends to the vertical radiators 14.

[0034] The described shape of the ring conductor 12 is made possible by the fact that the vertical radiators 14 are arranged 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 radiators in the area of ​​the inner, upper corners of the ring conductor near the center.

[0035] Fig. 2 shows a further embodiment of a satellite antenna whose ring conductor 22 has a square shape, with vertical radiators 24 each arranged approximately centrally 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, which are connected to each other by a crosspiece 24c, which contacts the coupling point 16.

[0036] Fig. 3 shows another embodiment of a satellite antenna having a monopole-like geometry. In this embodiment, the ring conductor 32 has the same shape in a developed plan view as the ring conductor 12 of the embodiment of Fig. 1 However, the design of Fig. 3 The ring conductor 32 is angled 8 times by 90°. As a result, the ring conductor 32 has a total of four sections 32a extending orthogonally to the base plate 10, each of which is U-shaped and connected at its bottom to a vertical radiator 34. At the top of the U, each leg of a U-shaped section 32a adjoins an L-shaped section 32b angled by 90°, which extends parallel to the base plate 10.

[0037] How Fig. 3 As illustrated, the sections 32a extending orthogonally to the base plate 10 merge coplanarly into a vertical radiator 16 at their underside or at their lower edge.

[0038] Fig. 4 shows another embodiment of a satellite antenna in which the ring conductor has been reduced to such an extent that it is reduced to a central connection point. This creates a capacitively fed cross dipole formed from two intersecting dipoles 42 and 43. The two dipoles 42 and 43 run orthogonally to each other and intersect at the center Z, with each dipole 42 and 43 being connected at its two outer ends to a vertical radiator 44. Both dipoles 42 and 43 run parallel above the base plate 10 and spaced from it.

[0039] Fig. 5 shows a Fig. 4 similar embodiment, which differs from the one in Fig. 4 The embodiment shown differs in that the two dipoles 52 and 53 are galvanically isolated. In this embodiment, the two dipoles 52 and 53 are formed as separate conductors, each provided with a U-shaped bend in the center region so that the two dipoles 52 and 53 do not touch each other.

[0040] Fig. 6 shows another embodiment of a satellite antenna with two dipoles 62 and 63, each electrically connected at its end to vertical radiators 64. The two dipoles 62 and 63 extend orthogonally to each other, but do not intersect, 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.

[0041] Fig. 7 shows an antenna arrangement with a total of three nested satellite antennas whose loop conductors overlap each other. A first satellite antenna with a square loop conductor 22' is arranged above the base plate 10, the vertical radiators 24' of which are arranged centrally between the corners of the loop conductor 22'.

[0042] Within the ring conductor 22' of the first satellite antenna, a second satellite antenna is arranged, the ring conductor 12' of which is arranged in the same way as the ring conductor 12 of the embodiment of Fig. 1 However, the vertical radiators 14' of this satellite antenna are bent outwards at an obtuse angle at their upper ends, so that they and thus also the ring conductor 12' cover the ring conductor 22' of the first satellite antenna.

[0043] Finally, a third satellite antenna with an approximately square ring conductor 72 is arranged inside and below the first and second satellite antennas, which is also connected to four vertical radiators.

[0044] Fig. 8 shows a further embodiment of a satellite antenna with a square ring conductor 82 arranged parallel above a base plate 10. In the area of ​​the four corners of the ring conductor 82, this is connected to vertical radiators 84, which are capacitively coupled to the base plate 10 as in the previously described embodiments, with two of the vertical radiators 84 in turn having a coupling point 18 for feeding into an antenna connection.

[0045] In this embodiment, a second ring conductor 83 is arranged slightly above the ring conductor 82, which, however, 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 somewhat narrower tracks and projecting beyond the outer contour of the first ring conductor 82. The second ring conductor 83 is fastened in its Fig. 8 held in the position shown.

[0046] In the embodiments described above, all ring conductors can be manufactured in a known manner, for example, as a stamped and bent part. 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, characterized in that a second ring conductor (83) is arranged in a near region of the ring conductor (82) and is not galvanically coupled to the electrically conductive structure.

2. A satellite antenna according to claim 1, characterized in that the ring conductor (12, 12', 22, 22', 32, 72, 82) is formed as a regular polygon, wherein 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).

3. A satellite antenna according to one of the preceding claims, 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.

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

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

6. 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).

7. 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.

8. 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).

9. 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).

10. A satellite antenna according to any one of the preceding claims 1 to 9, characterized in that the second ring conductor (83) is arranged above the ring conductor (82).

11. A satellite antenna according to claim 1, characterized in that both ring conductors (82, 83) have the same geometric shape.

12. 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.