Vehicle antenna

Abstract

Vehicle antenna a first emitter (2), a second spotlight (3), a first feed point connected to the first radiator (2), a second feed point connected to the second radiator (3), characterized in that the two radiators (2, 3) are connected at their ends away from the feed point via an electrical line (5), the line (5) being connected at each of its ends via an ohmic resistor to (6) one of the two radiators (2, 3).

Description

[0001] The invention relates to a vehicle antenna with the features specified in the preamble of claim 1, as is known, for example, from EP 4 092 914 A1.

[0002] Such vehicle antennas are called MIMO antennas (Multiple Input Multiple Output) because the antenna's radiators can be used to send or receive different data sets simultaneously.

[0003] In modern antenna systems, the data stream to be transmitted is divided into multiple streams or transmission channels according to the number of participating radiators, which in principle allows for a significant increase in data rates. However, a problem arises from crosstalk between the radiators of an antenna. A portion of the power radiated by one radiator is received by another radiator of the same antenna and thus lost from the field. This problem of unwanted coupling between the radiators of an antenna is more pronounced the smaller the distance between them, and therefore occurs particularly frequently with compact vehicle antennas.

[0004] To solve the problem of coupling between the radiators of a vehicle antenna, EP 4 092 914 A1 recommends a decoupling mesh at the base of the radiators. An alternative way to reduce coupling is to use radiators with different polarization and radiation patterns.

[0005] The object of the present invention is to demonstrate a way in which the coupling between the radiators of a compact vehicle antenna can be reduced cost-effectively.

[0006] This problem is solved by a vehicle antenna having the features specified in claim 1. Advantageous embodiments of the invention are the subject of dependent claims.

[0007] In a vehicle antenna according to the invention, a first and a second radiator are connected at their ends furthest from their feed point via a line, at each end of which an ohmic resistor is arranged. In this way, a portion of the transmit power of one radiator can be fed into the other radiator via the line in opposite phase. Each radiator thus receives power from the other radiator both via the line and via the radiation field. The signal of the power fed in via the line and the signal of the power coupled in via the radiation field interfere destructively and, ideally, cancel each other out completely. Advantageously, crosstalk can thus be largely reduced, and a compact antenna can be created that enables efficient operation.

[0008] The amount of power fed into each radiator via the cable depends on the resistances at both ends of the cable. These resistances can be carefully selected to significantly reduce the decoupling of the two radiators in a vehicle antenna within a specific frequency band, for example, to a value of -10 dB. For most applications, resistances of at least 500 ohms are advantageous. Resistances greater than 10 kOhms generally offer no benefit, as the power fed into each radiator via the cable becomes quite low.

[0009] An advantageous embodiment of the invention provides that both the first and second radiators of the vehicle antenna are monopole radiators. Monopole radiators operate best in a frequency range where the electrical length of the monopole radiator corresponds to approximately one-quarter of the wavelength. By connecting the two radiators at their ends furthest from their feed point via an electrical conductor, the signal fed in via the conductor and the signal coupled in via the radiation field are largely out of phase, thus reducing the coupling between the two radiators through destructive interference.

[0010] Suitable monopole radiators include, besides classic monopole antennas, which are also called quarter-wave radiators, for example inverted F-antennas.

[0011] An advantageous embodiment of the invention provides that the vehicle antenna comprises a printed circuit board on which the radiators are each formed as metallized surfaces. The conductor connecting the free ends of the radiators can advantageously be designed as a stripline, i.e., a conductive trace. This allows for a cost-effective and compact design. The resistors at the ends of the conductor can be implemented as surface-mount components, which simplifies manufacturing.

[0012] Further details and advantages of the invention will be explained using an exemplary embodiment of the invention with reference to the accompanying drawing. Fig. Figure 1 shows a schematic sketch of a vehicle antenna.

[0013] The in Fig. The vehicle antenna shown in Figure 1 has a circuit board 1 on which a first radiator 2 and a second radiator 3 are formed as metallized surfaces. Both radiators 2 and 3 are monopole radiators, each connected at its feed point to an electrical connector 4, for example, a double connector. At their ends opposite the feed point, the radiators 2 and 3 are connected via an electrical conductor 5, which is formed as a stripline on the circuit board 1. At each end of the conductor 5, a high-impedance resistor 6, for example, of 500 ohms or more, is arranged, through which the conductor 5 is connected to one of the two radiators 2 or 3.

[0014] During operation, the signal emitted by the first radiator 2 is received by the second radiator 3, which in itself leads to an undesirable attenuation of the radiation field. However, in the antenna shown, a portion of the power fed into the first radiator 2 via the feed point is also fed into the second radiator 3, namely via line 5. The signal fed into the second radiator 3 via line 5 is out of phase with the signal received from the field and thus causes destructive interference.

[0015] Similarly, the first radiator 2 receives power from the second radiator in two ways: via the field and the line 5. The signals received via these two paths are out of phase and therefore interfere destructively. As a result, the coupling between the two radiators 2 and 3 is advantageously reduced.

[0016] The two in Fig.The schematically represented emitters 2 and 3 can also have a different shape, such as a flat, elongated, or branched structure made of conductive material. One end of the structure is connected to a feed point, the other to the line 5 via a resistor 6.

[0017] In the illustrated embodiment, a bracket 8 is attached to the circuit board, which is intended for mounting the vehicle antenna to a vehicle. This bracket 8 is designed as a metal sheet with one or more openings and can therefore, in addition to its mounting function, also be used to improve the radiation characteristics of the vehicle antenna, in particular to direct the radiation into the exterior of the vehicle towards an outer edge of the vehicle body. Reference symbol list 1 circuit board 2 spotlights 3 spotlights 4 connector 5 lines 6 Resistance 8 hangers QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 4 092 914 A1 [0001, 0004]

Claims

[1] Vehicle antenna with a first emitter (2), a second spotlight (3), a first feed point connected to the first radiator (2), a second feed point connected to the second radiator (3), characterized by , that the two radiators (2, 3) are connected at their ends away from the feed point via an electrical line (5), the line (5) being connected at each of its ends via an ohmic resistor to (6) one of the two radiators (2, 3). [2] Vehicle antenna according to claim 1, characterized by , that the first emitter (2) is a monopole emitter and the second emitter (3) is a monopole emitter. [3] Vehicle antenna according to one of the preceding claims, characterized by , that the electrical resistances (6) each have a value of at least 500 ohms. [4] Vehicle antenna according to one of the preceding claims, characterized bya printed circuit board (1) on which the first emitter (2) is formed as a metallized surface and the second emitter (3) is formed as a metallized surface. [5] Vehicle antenna according to claim 4, characterized by , that the resistors (6) are arranged as a surface-mounted component on the circuit board (1). [6] Vehicle antenna according to claim 4 or 5, characterized by , that the line (5) is designed as a stripline on the printed circuit board (1). [7] Vehicle antenna according to any one of claims 4 to 6, characterized by , that the circuit board (1) carries a double connector (4) which is connected to the first emitter (2) and the second emitter (3). [8] Vehicle antenna according to one of the preceding claims, characterized by , that a metal bracket (8) for attachment to a vehicle body is attached to the circuit board (1).

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