Antenna device and vehicle including the same

Abstract

The present invention relates to an antenna device (1), comprising: at least two antennas (2), which are designed to transmit and / or receive electromagnetic waves; and a circuit board device (3), wherein the antennas (2) are arranged on the same circuit board device (3), and the circuit board device (3) comprises at least one decoupling layer (6), through which the parasitic coupling of the antennas (2) is reduced. The present invention stipulates that the circuit board device (3) comprises at least one upper substrate layer (11), on which at least one metal strip (14) is arranged, the metal strip having a predetermined size, wherein the metal strip (14) is separated from the at least one decoupling layer (6) by the at least one upper substrate layer (11).

Description

Technical Field

[0001] The invention relates to an antenna arrangement and a vehicle comprising at least one antenna arrangement. Background Art

[0002] In order to reduce the size of the antenna device, the scheme of arranging multiple antennas on one side of the circuit board device is widely used. For example, the antenna can be a monopole antenna or a patch antenna. These antennas can transmit and / or receive corresponding electromagnetic waves during operation. As expected, part of the corresponding electromagnetic waves is radiated into the surrounding environment. In particular, in the case of antennas on a circuit board including a dielectric substrate layer and a conductive layer, part of the electromagnetic waves are guided as surface waves along the boundary surface or as volume waves along the circuit board or within the circuit board. As a result, undesirable parasitic coupling occurs between the antennas. This coupling generally has a negative impact on the antenna performance, and in terms of the multiple-input multiple-output (MIMO) transmission method used in the current 5G mobile phone technology, this coupling can impair the signal-to-noise ratio and / or the possible transmission rate.

[0003] In order to reduce these parasitic couplings, the distance between the antennas can be increased, for example, although this is only possible to a limited extent in the case of MIMO antennas in motor vehicles or mobile terminals due to geometrical limitations on size.

[0004] One possibility for reducing parasitic coupling is to use electromagnetic bandgap structures. These structures exhibit increased impedance within a specific frequency range. This attenuates electromagnetic waves within that frequency range, thus reducing coupling between antennas.

[0005] This frequency range depends on the inductance and capacitance of the electromagnetic bandgap structure. Therefore, these inductance and capacitance must be selected to match the frequency range to be attenuated. According to the prior art, this is achieved by designing the individual components of the bandgap structure. However, this creates the problem of having to provide a corresponding bandgap structure for the respective frequency range.

[0006] The design of electromagnetic bandgap structures has been studied, for example, in the following scientific publications:

[0007] KUSHWAHA, Nagendra; KUMAR, Raj. Study of different shape electromagnetic band gap (EBG) structures for single and dual band applications. Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2014, Vol. 13, No. 1, pp. 16-30.

[0008] THAYSEN, Jesper; JAKOBSEN, Kaj B. Design considerations for low antenna correlation and mutual coupling reduction in multi antenna terminals. European transactions on telecommunications, 2007, Vol. 18, No. 3, pp. 319-326.

[0009] The following bandgap structures are known from the prior art:

[0010] US Pat. No. 7,760,140 B2 describes a multi-band antenna device having an electromagnetic bandgap structure, comprising two or more planar antennas arranged on a surface of a substrate, a first set of electromagnetic bandgap elements located on the surface with the antennas and between the antennas, and a second set of electromagnetic bandgap elements located within the substrate below the antennas.

[0011] CA 2 936 482 A1 describes an electromagnetic bandgap structure formed from a coplanar waveguide with inductors and capacitors selected so as to produce frequency-dependent coupling between a parallel plate waveguide mode and a coplanar waveguide mode to create an electromagnetic bandgap. Summary of the Invention

[0012] Therefore, an object of the present invention is to achieve a shift in the frequency range of an electromagnetic bandgap structure without changing the shape of elements in the electromagnetic bandgap structure.

[0013] This object is achieved by an antenna device and a vehicle. Advantageous developments of the invention emerge from the features of further exemplary embodiments, from the following description and from the accompanying drawings.

[0014] The present invention relates to an antenna device. The antenna device includes at least two antennas configured to transmit and / or receive electromagnetic waves. The antenna device includes a circuit board device, wherein the antennas are arranged on the same circuit board device. The circuit board device may include at least one circuit board, on which integrated circuits or components for antenna operation may be arranged. The circuit board device may include multiple layers stacked one on top of the other. These layers may, for example, include substrate layers composed of dielectric materials or conductive layers composed of conductive materials. The circuit board device may include at least one decoupling layer, which reduces parasitic coupling between the antennas. In other words, at least one layer is arranged in the circuit board device to reduce parasitic coupling between the antennas caused by electromagnetic waves. The decoupling layer may have an increased impedance within a predetermined frequency range. This reduces the surface component of electromagnetic waves propagating along the circuit board device within the predetermined frequency range. The circuit board device includes at least one upper substrate layer, on which at least one metal strip having predetermined dimensions is arranged. In other words, the circuit board device includes at least one dielectric substrate layer, with the at least one metal strip arranged in or on a surface of the substrate layer. The metal strip is separated from the at least one decoupling layer by the at least one upper substrate layer. For example, one side of the upper substrate layer may be disposed on the decoupling layer. The at least one metal strip may be disposed on the other side of the substrate layer. The metal strip may be, for example, a metal foil or a metal-coated area of the substrate layer. The dimensions of the metal strip may be determined so that the frequency range in which the two antennas are decoupled by the decoupling layer is shifted to a lower frequency range. In other words, the dimensions of the metal strip may be determined so that the frequency range in which high impedance is exhibited is shifted.

[0015] The invention offers the advantage that the frequency range in which the increased impedance occurs can be shifted without changing the decoupling layer.

[0016] The invention also includes optional further developments, which can lead to further advantages.

[0017] A further development of the invention provides that the decoupling layer comprises a high-impedance structure. In other words, the decoupling layer comprises at least one regular arrangement of metal surfaces in at least one conductive layer, wherein the respective metal surface is conductively connected to the ground layer through the substrate layer by means of respective connecting elements aligned perpendicularly to the metal surface. In other words, at least one substrate layer of the antenna device comprises a ground layer located on one side. The regular arrangement of metal surfaces is located on the side of the substrate layer opposite to the ground layer, wherein the respective metal surfaces are conductively connected to the ground layer via respective connecting elements passing through the substrate layer. The metal surfaces interact with the ground layer here and can provide a capacitance. The connecting elements can provide a predetermined inductance. This has the advantage that a resonance with a predetermined frequency can be provided by specifying a predetermined resonance and a predetermined inductance. The frequency can be selected in such a way that it corresponds to the frequency of the surface waves or volume waves to be suppressed.

[0018] For example, it can be provided that the capacitance of the elements in the high-impedance structure is specified by specifying the surface area of the metal surface, selecting a substrate material for the substrate layer with a predetermined dielectric constant, and selecting a predetermined spacing between the metal surface and the ground layer. The inductance of the elements in the high-impedance structure can be specified by selecting the dimensions of the connecting elements. For example, the high-impedance structure can be a so-called mushroom-shaped electromagnetic band gap structure. Since the impedance of the structure increases in the resonant frequency range, the propagation of parasitic couplings that exhibit a predetermined resonant frequency can be reduced. The present invention has the advantage that by determining the predetermined resonant frequency with the help of the high-impedance structure, the propagation of parasitic couplings at the predetermined resonant frequency can be reduced. For example, it can be provided that the high-impedance structure has at least one resonant frequency that is located in the frequency spectrum of one of the antennas.

[0019] A further development of the present invention provides that the decoupling layer comprises an incomplete floor structure. In other words, the decoupling layer comprises a conductive surface connected to ground potential, wherein the conductive surface has periodic incomplete regions along at least one plane direction of the surface, in which areas of the conductive material have been removed. For example, the conductive surface can be a copper layer with periodic holes that can be connected to ground potential. Such a structure is known as a planar electromagnetic bandgap structure, for example.

[0020] A further development of the present invention provides that the at least one metal strip is aligned in the longitudinal direction of the at least two antennas. In other words, the metal strip is arranged on the upper substrate layer in such a way that its longitudinal direction runs parallel to the line connecting the two antennas. For example, it can be provided that the metal strip has a length greater than its width. The longitudinal direction of the length can be aligned parallel to the line connecting the two antennas. This has the advantage that the metal strip is aligned in the direction of maximum intensity of the surface waves.

[0021] The invention also includes a motor vehicle having at least one antenna arrangement.

[0022] The invention also includes developments of the motor vehicle according to the invention which have the features already described in conjunction with the development of the antenna device according to the invention. Therefore, corresponding further developments of the motor vehicle according to the invention will not be described again here.

[0023] The invention also covers combinations of features of the described embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following describes exemplary embodiments of the present invention. In this regard:

[0025] Figure 1 An antenna arrangement is shown;

[0026] Figure 2 shows a plan view of the antenna arrangement;

[0027] Figure 3 The antenna arrangement is shown without the metal strip;

[0028] Figure 4 An antenna arrangement having a metal strip is shown;

[0029] Figure 5 a graph showing an S12 parameter of an antenna of an antenna arrangement; and

[0030] Figure 6 A comparison between the two curves for the S12 parameter is shown.

[0031] The exemplary embodiments described below are preferred embodiments of the present invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the present invention, which should be considered independently of one another and each also independently develop the present invention and can therefore also be considered as part of the present invention individually or in combinations other than the combinations shown. In addition, the described embodiments can also be supplemented by further features of the present invention that have already been described.

[0032] In the figures, elements having the same function are each provided with the same reference numerals. DETAILED DESCRIPTION

[0033] Figure 1An antenna arrangement is shown. Antenna arrangement 1 may include at least two antennas 2, which may be arranged on one side of a circuit board arrangement 3 of antenna arrangement 1 and may be spaced apart. For example, antenna 2 may be a monopole antenna connected to respective antenna terminals 4. It may be provided that antennas 2 are fed through respective antenna terminals 4 to emit electromagnetic waves in respective frequency spectra. The frequency spectra of the two antennas 2 may overlap or be the same. The two antennas 2 may be controlled by an integrated circuit 5, which may be arranged on the same circuit board arrangement 3 as the antennas 2.

[0034] The circuit board arrangement 3 may include a decoupling layer 6. The decoupling layer may be provided to reduce electromagnetic coupling between the two antennas 2 due to parasitic waves. Parasitic waves may, for example, be surface components of electromagnetic waves radiated by the antennas 2 that are guided along the circuit board arrangement 3. The decoupling layer 6 may include a high-impedance structure 7. The high-impedance structure 7 may have a periodic arrangement of high-impedance elements 8. It may be provided that the high-impedance elements 8 may be so-called mushroom-shaped structures. The high-impedance elements 8 may be arranged on the ground layer 9 of the decoupling layer 6. The high-impedance elements 8 may include corresponding connecting elements 10, which may be arranged in the substrate layer 11 of the decoupling layer 6 to connect to a metal surface 12 arranged above the substrate layer 11 and parallel to the ground layer 9. The dimensions of the high-impedance elements 8 and the material of the substrate layer 11 may be selected so that the high-impedance elements 8 exhibit a predetermined capacitance and a predetermined inductance. As a result, resonance occurs in the decoupling layer 6 at specific frequencies. At these frequencies, the decoupling layer 6 may exhibit a higher impedance, thereby reducing the propagation of parasitic waves. These frequencies will be selected within the frequency range of the electromagnetic waves to be suppressed.

[0035] At least one upper substrate layer 13 may be disposed on the decoupling layer 6. Substrate layer 13 may be composed of a dielectric material. At least one metal strip 14 may be disposed on substrate layer 13. Metal strip 14 may be, for example, a foil bonded to substrate layer 13 or a metal-coated area. Metal strip 14 may be disposed between antennas 2. The at least one metal strip 14 and upper substrate layer 13 may have dimensions that shift the frequency range of the decoupling layer 6 to a lower frequency range.

[0036] Figure 2A plan view of an antenna device 1 is shown. The antenna device can include at least two antennas 2. A metal strip 14 can be arranged on an upper substrate layer 13 between the antennas 2. A decoupling layer 6, which can include a high-impedance structure 7, can be arranged below the upper substrate layer 13. The high-impedance elements 8 of the high-impedance structure 7 can be arranged periodically. The metal surface of the high-impedance element 8 can have a predetermined shape, such as a swastika, a cross, or a rectangle. The metal surface of the high-impedance element 8 can have dimensions of 4.8 mm * 4.8 mm * 0.8 mm. The width of the metal strip can be 2.3 mm. The upper substrate layer 13 can have a thickness of 1.3 mm. The antenna device 1 can be arranged, for example, in a motor vehicle 15.

[0037] Figure 3 An antenna arrangement 1' is shown, wherein the circuit board arrangement 3' may comprise a decoupling layer 6' with a high impedance structure 7'. The antenna arrangement 1' does not have any metal strip 14' between the two antennas 2'. The antenna 2' may be a monopole antenna.

[0038] Figure 4 The antenna device 1 is shown. Figure 3 , wherein, unlike the antenna arrangement 1 , the antenna arrangement 1 may include a metal strip 14 between the two antennas 2. The metal strip may include copper and may have dimensions of 16 mm×3.7 mm.

[0039] Figure 5 A graph shows the S12 parameter for antenna 2' of antenna assembly 1', which includes neither a decoupling layer 6' with a high-impedance structure 7' nor a metal strip 14'. The S21 parameter can describe the transmission of electromagnetic waves from one antenna 2' to another. The S12 parameter is plotted against frequency f. The graph shows a relatively constant value at all frequencies f.

[0040] Figure 6 A comparison between two curves of the S12 parameter is shown. Curve 1 shows Figure 3 The S12 parameter of the antenna device 1' is shown in FIG. The antenna device includes a decoupling layer 6' but does not include a metal strip. Curve II shows Figure 4 The S12 parameter curves of the antenna device 1 are shown in Figure 1. The antenna device 1 includes a decoupling layer 6 and a metal strip 14. Both curves I and II show characteristic frequency ranges fI and fII with relatively low S12 parameter values. Curve II has a similar shape, but the drop is more pronounced and shifts to a lower frequency by approximately 0.5 GHz.

[0041] Overall, this example shows how the invention can influence the frequency range of the decoupling layer.

Claims

1. An antenna device (1), comprising: at least two antennas (2) designed to transmit and / or receive electromagnetic waves, and A circuit board arrangement (3), wherein the antenna (2) is arranged on the same circuit board arrangement (3), The circuit board arrangement (3) comprises at least one decoupling layer (6), by which the parasitic coupling of the antenna (2) is reduced, wherein The circuit board device (3) comprises at least one upper substrate layer (13), on which at least one metal strip (14) of predetermined size is arranged, wherein The metal strip (14) is separated from the at least one decoupling layer (6) at least by the at least one upper substrate layer (13), and The at least one decoupling layer comprises a conductive surface connected to ground potential, wherein the conductive surface has periodic imperfect regions.

2. The antenna device (1) according to claim 1, characterized in that The at least one decoupling layer (6) comprises a high impedance structure (7).

3. The antenna device (1) according to claim 1 or 2, characterized in that The at least one decoupling layer comprises an incomplete floor structure.

4. The antenna device (1) according to claim 1 or 2, characterized in that The at least one metal strip (14) is aligned in a longitudinal direction toward the at least two antennas (2).

5. The antenna device (1) according to claim 1 or 2, characterized in that The at least one decoupling layer is a copper layer having periodic holes.

6. A motor vehicle (17) having at least one antenna arrangement (1) according to one of claims 1 to 5.

Images