Patent Application
20200006850
This patent application claims priority to European Provisional Patent Application No. 18382488.7, filed Jun. 29, 2018, which is incorporated herein by reference in its entirety.
The present disclosure relates to broadband and multiband antennas, and more particularly to broadband and multiband antennas used as remote or external antennas for vehicles.
Due to the large size of some electronic devices, it is difficult to accommodate a large antenna system inside a reduced space. For this reason, many communication devices of motor vehicles require remote (external) antennas to increase the performance of an internal antenna. In that scenario, it is critical that the dimension of the external antenna be as small as possible so that it can be fitted inside a reduced space within a vehicle.
External antennas produce less electronic noise than internal antennas. Internal antennas should obtain worst sensitivity of the whole system as being nearer of the electronic noise sources (clocks, microprocessors, etc.). Therefore, in case of the external antennas this situation is improved as they can be moved out from these noise sources.
For example, LTE antennas require at the same time both a main antenna and a diversity antenna. However, these two LTE antennas (main and diversity) cannot be accommodated in the narrow interior of a shark fin antenna, especially in the low frequency band (700 MHz-1 GHz), wherein signal interference is high, and the level of the un-correlation obtained between the antennas would be poor. When more than one antenna is needed on a mobile system as LTE, antennas must be as uncorrelated as possible between them.
On the other hand, in more current cellular technologies, the number of cellular antennas included in the car has increased, as well as the requested performance. For LTE systems, typically two (2) antennas are used. With regard to the more current evolutions of LTE antennas and for the upcoming 5G antennas, the number of antennas will increase, requiring at least four (4) cellular antennas in the vehicles.
However, vehicle styling is more important every day, and therefore antennas may be hidden and preferably do not impact vehicle external designs, therefore the available space for antennas is reduced.
In this scenario, it is also preferable to integrated two antennas in a single box with reduced space in order to reduce the number of antenna modules (i.e., with two antennas in each module) that the vehicle manufacturer needs to install in a vehicle during production.
Furthermore, it is a challenge to integrate a multiband, high efficient, low VSWR LTE antenna in this reduced dimension.
Therefore, it is desirable to develop an improved antenna system for a vehicle having a reduced size, with high efficiency, and broadband behaviour. It is also desirable to have an antenna system that operates on all LTE frequency bands without losing broadband and high efficient characteristics in any band.
An object of the present disclosure is to provide a broadband, multiband, and high efficiency antenna system of reduced dimensions, and capable of being fitted within a confined space, for example inside a component of a vehicle.
The antenna system of the present disclosure is preferably adapted to operate on the LTE communication network, and to provide 5G communication services.
The antenna system is defined in the attached independent claim, and it refers to an antenna topology that fulfills the above-described challenges of the prior art, by providing an antenna topology comprising two radiating elements sharing a common ground plane that features a broad bandwidth and high efficiency, and that it can be fitted inside a reduced space within a vehicle. The effect of having two radiating elements placed over a common ground plane, is that the bandwidth of the overall antenna system is increased.
The antenna system comprises first, and second radiating elements placed above an upper surface of the ground plane, and are folded such as each radiating element has a vertical surface and a horizontal surface.
The vertical surfaces of the two radiating elements are substantially orthogonal to the ground plane and parallel to each other, and the horizontal surfaces are substantially coplanar between them and parallel to the ground plane.
The area of the vertical surfaces widen progressively from the respective feeding points towards the respective horizontal surfaces. Preferably, the vertical surfaces have an asymmetric triangular shape, such as two feeding ports are respectively connected between a vertex of the vertical surfaces and the ground plane.
The vertical surfaces shaped as triangles are monopole elements that improve the antenna system overall bandwidth, especially at the upper range of the antenna system band of operation, that is, from several GHz up to 6 GHz frequencies.
On the other hand, the folded configuration of the radiating elements having a surface parallel to the ground plane, achieve the complete frequency range in a reduced height of around λ/33.
Furthermore, the two feeding ports of radiating elements, are placed on an interior region of the ground plane, in order to achieve an omni-directional pattern of the antenna at whole band of operation.
Additionally, the antenna system comprises first, and second parasitic elements placed above the ground plane, and substantially coplanar or parallel to the horizontal surfaces of the radiating elements. Each parasitic element is connected with the ground plane and extends around one of the radiating elements. These parasitic elements fine tune the antenna system at the lower frequency band, around 700 MHz.
The ground plane has first and second opposing large edges and two opposing short edges, and preferably the ground plane has generally a rectangular shape. The vertical surfaces of the first and second radiating elements are transversally arranged with respect to the two opposing large edges. The two feeding points are closer to the first large edge of the ground plane.
Furthermore, the first and a second parasitic elements are generally L-shaped having a short segment and a large segment, and the horizontal surfaces of the radiating elements are placed between the large segment of one of the parasitic elements and one of the short edges of the ground plane.
The ground plane has first and second cut-outs at the short edges of the ground plane and placed below a part of the radiating element. The technical effect of these cut-outs is that an omni-directional radiation pattern of the antenna at the whole band of operation is achieved.
Additionally, the ground plane has a slot that extends from one of the large edges of the ground plane and transversally to the ground plane. Preferably the slot is straight and shorter than the short edges of the ground plane. The slot is placed between the two radiating elements, such as this arrangement of the slot at the ground plane, increases isolation between the two radiating elements of the antenna system.
Preferably, the first and second radiating elements and the first and second parasitic elements, are configured and arranged such as they are a mirror image of each other.
The ground plane might be implemented as a conductive layer on a surface of a (non-conductive) substrate, like a Printed Circuit Board (PCB). In that case, the antenna system may include a satellite navigation antenna (GNSS), attached to another non-conductive surface of the PCB, such as the substrate isolate the GNSS antenna from the radiating elements.
The antenna system of the of the present disclosure is preferably adapted to operate at least within one Long Term Evolution (LTE) frequency band, and to be used as remote antenna for a motor vehicle, and to provide 5G communication services.
Some of the advantages of the present antenna system are summarized below:
The above features and advantages, and other features and advantages of the disclosure are readily apparent from the following detailed description when taken in connection with the accompanying drawings.
Other features, advantages and details appear, by way of example only, in the following detailed description, the detailed description referring to the drawings in which:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
Each radiating element 1, 2 is folded such as it has a vertical surface 1a, 2a and a horizontal surface 1b, 2b, and wherein the vertical surfaces 1a, 2a of the two radiating elements 1, 2 are orthogonal to the ground plane 3 and parallel to each other. Additionally, the horizontal surfaces 1b, 2b of the two radiating elements 1, 2 comprise a rectangular area, are coplanar between them, and parallel to the ground plane 3. Preferably, the length of the horizontal surfaces 1b, 2b is around λ/10 (see
The ground plane 3 is generally rectangular and as such, it has two opposing large edges 3a, 3b and two opposing short edges 3c, 3d, and the vertical surfaces 1a, 2a of the first and second radiating elements 1, 2 are transversally arranged with respect two opposing large edges 3a, 3b. Furthermore, each of the first and second radiating elements 1, 2 is closer to opposite short edges of the ground plane 3.
With the above-described arrangement of components, the antenna system 8 generally configures a rectangular prismatic volume which larger side is around λ/5, that is 77 mm at 700 MHz.
Taking in account that the lowest frequency of operation is at 700 MHz and the velocity of wave propagation over the air (v=3e8 m/s) the operative wavelength is (λ=v/f=3e8/700e6=428 mm). As described on
The antenna system 8 further comprises a first and a second parasitic elements 6, 7 connected with the ground plane 3 and substantially coplanar with the horizontal surfaces 1b, 2b of the radiating elements 1, 2, and therefore parallel to the ground plane, and extending around one of the radiating elements 1, 2.
Each parasitic element (6,7) is L-shaped having a short segment and a large segment, such as the horizontal surfaces 1b, 2b of the radiating elements 1, 2 are placed between the large segment of one of the parasitic elements 6, 7 and one of the short edges 3c, 3d of the ground plane 3. Preferably, the length of the large segment is around λ/8, and the length of the short segment is around λ/16, as shown in
As shown in
The vertical surfaces 1a, 2a are triangular and the feeding ports 4, 5 are connected with one of the vertex. The feeding ports 4, 5 are placed in an interior region of the ground plane 3, in particular as shown in
The ground plane 3 has first and second squared cut-outs 9, 10 at the short edges 3c, 3d of the ground plane 3, such as each cut-out has three edges with a length around λ/21. As shown in
Furthermore, the ground plane 3 has a slot 11 that extends from one the second large edge (3b) of the ground plane 3. The slot 11 is straight with a length of around λ/9, that is, shorter than the short edges 3c, 3d, and it is placed transversally and right at the center of the ground plane 3 as shown in
The antenna system 8 is a symmetric structure, such as the set formed by the first radiating and parasitic elements (1,6), and the set formed by the second radiating and parasitic elements (2,7), are a mirror image of each other. For that, the first and second radiating elements 1, 2 are configured and arranged such as they are a mirror image of each other, and similarly the first and second parasitic elements 6, 7 are configured and arranged such as they are a mirror image of each other.
With this configuration, the antenna system 8 of the embodiment of
The ground plane 3 is a conductive layer formed on one of the faces of a PCB (13). As shown in
Nevertheless, in other preferred embodiments and in order to provide a more compact solution, the GNSS antenna (12) might be placed on top of the ground plane 3 suitably isolated from the radiating elements.
The ground plane 3 can be implemented as a Printed Circuit Board (PCB), that includes GNSS circuitry like: an amplifier, filter, couplers, a GNSS splitter (to provides two outputs), etc., without affecting the antenna performance.
The effect of having the GNSS antenna (12) in the opposite face of the ground plane 3 to the location of the radiating elements 1, 2, is that the ground plane 3 isolates the GNSS antenna from the radiating elements 1, 2.
For applications in which the antenna housing can be made larger, a GNSS multiband or multi constellation stacked patch can be provided to cover several frequency bands.
The antenna system 8 is designed to operate at least within one Long Term Evolution (LTE) frequency band, wherein the lowest frequency of operation is 700 MHz. Additionally, the antenna system is further adapted to provide 5G communication services.
While the present disclosure is described with reference to the figures, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the present disclosure. In addition, various modifications may be applied to adapt the teachings of the present disclosure to particular situations, applications, and/or materials, without departing from the essential scope thereof. The present disclosure is thus not limited to the particular examples disclosed herein, but includes all embodiments falling within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18382488.7 | Jun 2018 | EP | regional |
