Description

The invention relates to an arrangement of at least two plane antennas, comprising a printed circuit board, the printed circuit board having a first layer comprising a conductive material enclosing in a first area of the first layer non-conductive material having a bow-tie or butterfly-shaped contour, the first area of the first layer forming a dipole antenna having a first polarisation direction.

A plane dipole antenna arranged on a printed circuit board is known from the prior art. On the substrate of the printed circuit board, conductive material is arranged for this purpose, which has a recess, also called a slot, with a shape that reminds one of the shape of a fly or a butterfly. This recess is filled with a non-conductive material. Such antennas are also called bow-tie antennas or butterfly antennas. Depending on the design, several layers of a multilayer printed circuit board can be used to form structures of the antenna.

A large number of planar dipole antennas can be used in motor vehicles. On the one hand, several vertically polarised antennas arranged side by side can be used to determine the angle of incidence of radiation in a horizontal plane. The determination of the angle of incidence can be used, for example, to detect the location of an object in conjunction with radar-like signal processing.

Planar antennas can also be used to receive radio signals for communication or navigation. Such signals are often reflected on the way from the transmitter to the vehicle equipped with the antenna, so that they come from the transmitter to the receiving antenna in the vehicle on different paths and the waves transported on the different paths can be differently polarised. If an antenna with only a first polarisation direction is used for reception, and the waves of this polarisation direction arriving at the motor vehicle have only a low amplitude, but the waves arriving at the motor vehicle with a polarisation perpendicular thereto have a high amplitude, it is advantageous if not only the waves of the first polarisation direction can be received in the vehicle, but also waves with a polarisation direction perpendicular thereto. In known antenna arrangements, in which this so-called polarisation diversity is also important, an antenna for waves with a first polarisation direction and an antenna with a polarisation direction perpendicular to the first polarisation direction are therefore equipped.

One of the inventors' concerns was to reduce the number of antennas provided in a vehicle. A reduction in the number of antennas has various advantages: For example, costs for the manufacture and installation of the antennas can be reduced if fewer antennas are installed in a vehicle. In addition, less installation space must be provided for the installation of antennas and the routing of cables to the antennas or electrical devices connected to the antennas.

This is the starting point for the inventors, who have addressed the technical problem of reducing the number of antennas.

According to the invention, a reduction of the antennas is achieved by further developing an antenna arrangement of the aforementioned type and, according to the invention, the printed circuit board in the first or another layer has a second area in which the conductive material has a triangular contour, a triangle-like contour or a trapezoidal contour which is surrounded by non-conductive material, the second area of the first or the other layer forming a planar monopole antenna with a second polarisation direction.

The first area of the antenna arrangement according to the invention thus forms an antenna with the first polarisation direction and the second area forms an antenna with the second polarisation direction perpendicular to the first. The antenna arrangement is thus suitable for the reception of electromagnetic waves with all polarisation directions and thus fulfils the requirement of polarisation diversity. At the same time, the antenna arrangement can also be used to receive waves for determining the angle of arrival. For this purpose, it can be combined with a second antenna of the same design. However, it is also possible to further implement an antenna arrangement according to the invention in such a way that the arrangement forms at least one further planar dipole antenna, wherein in a third area of the first layer a first further planar dipole antenna is realised like the first planar dipole antenna in the first area of the first layer and this first of the further planar dipole antennas has the first polarisation direction. With the aid of the first planar dipole antenna and the first further planar dipole antenna, which are arranged next to one another and both have the first direction of polarisation, the angle of arrival of the waves with components in the first direction of polarisation received by means of the signals received by the antenna arrangement according to the invention can also be determined.

With the invention the inventors have realized an antenna arrangement supporting angle of arrival in a specific incidence plane but rather for two different polarizations, while at the same time reducing the array and/or PCB size. The use of two monopole antennas allows to support vertically polarized incoming waves. While the use of two slot antennas directly beneath the vertically polarized antennas allows to support horizontally polarized incoming waves, with these elements fitted longitudinally along a PCB.

It is further possible that an antenna arrangement according to the invention has a fourth area and a second further planar monopole antenna like the second planar monopole antenna in the second area is also implemented in the fourth area and this second of the further planar antennas has the second polarisation direction. This could also be used to determine an angle of arrival of a wave with a component in the second polarisation direction.

The first and second polarisation directions can be perpendicular to each other. This is, after the above explanations, not surprising. In principle, however, it would also be possible for the polarisation directions of an antenna arrangement according to the invention not to be perpendicular to each other if they are only different from each other. The antenna arrangement may be installed in a vehicle such that the first polarisation direction is vertical and the second polarisation direction is horizontal when the vehicle is standing on a planar which is horizontal in each direction.

The printed circuit board of the antenna arrangement according to the invention on which the antennas are constructed may be a multilayer printed circuit board.

The non-conductive material with the bow-tie-shaped or butterfly-shaped contour may be formed by a first structure and a second structure of non-conductive material with a triangular contour or trapezoidal contour in the first area and optionally the third area of the first layer.

The conductive material with the triangular contour or trapezoidal contour provided in the second and possibly in the fourth area, the first structure provided in the first and possibly in the third area and the second structure provided in the first and possibly in the third area can be arranged symmetrically to a first axis of symmetry.

The first layer can be arranged on a first substrate layer made of a electrically non- conductive material, which is followed by a second layer with a material that is non- conductive in the first, in the second and possibly in the third and fourth area. In principle, electrically conductive structures could also be arranged in the first, in the second and possibly in the third and fourth areas of the second layer, in particular also outside the first and third areas.

The second layer can be arranged on a second substrate layer. It is then arranged between the first substrate layer and the second substrate layer. The second substrate layer can be followed by a third layer. In this third layer, a conductive material can be arranged in the first, second and possibly third and fourth areas. This can enclose a non-conductive material with a bow-tie-shaped or butterfly-shaped contour. This can be congruent or almost congruent with the bow-tie-shaped or butterfly-shaped contour of the non-conductive material in the first layer. The conductive material in the first and possibly third area of the first layer and the conductive material in the first and possibly third area of the third layer are connected to each other via linear vias or linearly placed vias through the first substrate layer, the second layer and the second substrate layer. These linear vias or linearly placed vias can be guided along edges of the recesses with the bow-tie-shaped or butterflyshaped contour.

The third layer can be arranged on a third substrate layer, which is followed by a fourth layer. In an area between the first structure and the second structure in the first and possibly the third area of the first layer, a first transmission line can end in each case, which is connected on the one hand to the conductive material in the first area or third area of the first layer and on the other hand through a via which leads through the first substrate layer, the second layer, the second substrate layer, the third layer, the third substrate layer to the fourth layer and is connected there to a first conductor path, and is connected through this first conductor path to a controllable switch in the fourth layer. If two first supply lines are provided, each of the transmission lines is connected to a first conductor.

According to the invention, the arrangement may comprise at least one second lead connecting the controllable switch to the conductive material having the triangular contour or trapezoidal contour in the second and/or fourth area.

The at least one switch may be a change-over switch which connects either the at least one first feed line or the at least one second feed line to a respective third feed line which is led to the receiving unit or transmitting and receiving unit of the antenna arrangement. In addition to the receiving unit or transmitting and receiving unit, an antenna arrangement according to the invention may also have a control unit, each of which is connected to the controllable switches via a control line.

An embodiment example for variants of an antenna arrangement according to the invention is described in more detail with reference to the drawing. It shows

Fig. 1 is a schematic representation of a printed circuit board of the first variant in a top view,

Fig. 2 a schematic representation of a printed circuit board of the second variant in a top view,

Fig. 3 a detail of a first layer of the printed circuit boards,

Fig. 4 a detail of a second layer of the printed circuit board,

Fig. 5 a detail from a third layer of the printed circuit board and

Fig. 6 a detail from a fourth layer of the printed circuit board.

The schematic illustration of Figs. 1 and 2 shows different structures of the two variants as if they were in one layer of the printed circuit board. In fact, the structures may be arranged in different layers of the PCB and the FOB may be a multilayer PCB comprising a sequence of layers with electrically conductive structures and substrate layers. It is particularly preferred if the various structures and possibly other structures not shown are arranged in several layers, for example in four layers in which conductive structures can be arranged and three substrate layers between the four layers.

The printed circuit board and has a first area 1 , a second area 2, a third area 3 and a fourth area 4.

In the first area 1 and the third area 3 of the first layer, an electrically conductive material 11 , 31 is arranged which encloses non-conductive material having a bow tieshaped or butterfly-shaped contour. The non-conductive material is arranged in two parts 12, 13, 32, 33, each having a trapezoidal contour. Parallel edges of the parts 12,

32 are arranged parallel to parallel edges of the other part 13, 33. The parts 12, 13, 32,

33 are arranged mirror-symmetrically to each other, namely mirror-symmetrically

RECTIFIED SHEET (RULE 91) ISA/EP to two different axes which are perpendicular to each other, namely a first axis of symmetry A and a second axis of symmetry B. The two shorter of the parallel sections of the parts 12, 13, 32, 33 are separated from each other by a narrow bridge 14, 34 of conductive material, the bridge 14, 34 being interrupted by a slot filled with electrically non-conductive material 15, 35.

The structures in the first area 1 and the structures in the second area 2 form first planar antennas for waves with a first polarisation direction.

Vias 5 lead from these bridges 14, 34 through the first substrate layer, the second layer, the second substrate layer, the third layer and the third substrate layer to the fourth substrate layer. There, the vias 5 are connected to conductor paths 6 that go to a controllable changeover switch 7. The vias 5 and the conductor paths 6 form first transmission lines.

From the non-parallel edges of the parts 12, 13, 32, 33, linearly placed vias lead from the first layer through the first substrate layer, the second layer and the second substrate layer into the third layer. In this third layer, conductive material 16, 36 is arranged in the first area as well as in the second area, which encloses electrically non- conductive material 17, 18, 37, 38, which has the same bow-tie-shaped or butterflyshaped contour as the non-conductive material 12, 13, 32, 33 in the first area and in the third area of the first layer and also has two trapezoidal parts 17, 18, 37, 38. The trapezoidal parts 17, 18, 37, 38 in the first as well as in the third area are separated from each other by the bridge 14, 19. The vias 5 are guided through these bridges 14, 19 without there being an electrically conductive connection between the bridges 14, 19 and the vias 5.

In the second and the fourth area 2, 4 of the printed circuit board, electrically conductive material 21 , 41 with a triangle-like contour is arranged either in the first, the second, the third or the fourth layer of the printed circuit board. The conductive material 21 , 41 is surrounded by non-conductive material 22, 42. The material is arranged in the areas 2, 4 mirror-symmetrically to the first symmetry axis A. One tip of the contour of the material 21 , 41 faces the first planar antennas. The electrically conductive material 21 in the second area and the electrically conductive material 41 in the fourth area each form a second planar antenna for waves with a second polarisation direction which is perpendicular to the first polarisation direction.

A second transmission line leads from the tip of the contour of the electrically conductive material 21 , 41 , if the material is provided in the fourth layer, directly as conductor path 8 or, if the material is provided in the first, second or third layer, indirectly as via and conductor path 8 to the changeover switches 7.

The first transmission lines are connected to a first contact and the second transmission lines are connected to a second contact of the changeover switch 7, which can be alternately connected to a centre connection of the changeover switch depending on a control of the changeover switch 7. The centre connection is connected to a receiving unit or to a transmitting and receiving unit outside the printed circuit board via a third transmission line. Control terminals of the changeover switch 7 are connected to control units outside the printed circuit board via a control line not shown.

List of reference signs

1 first area

11 electrically conductive material

12 electrically non-conductive material

13 electrically non-conductive material

14 bridge

15 electrically conductive material

16 electrically conductive material

17 electrically non-conductive material

18 electrically non-conductive material

2 second area

21 electrically conductive material

22 electrically non-conductive material

3 third area

31 electrically conductive material

32 electrically non-conductive material

33 electrically non-conductive material

34 bridge

35 electrically conductive material

36 electrically conductive material electrically non-conductive material electrically non-conductive material fourth area electrically conductive material non-electrically conductive material via conductor paths controllable change-over switch conductor paths linearly placed vias