GB2461896A

GB2461896A - Antenna assembly for a motor vehicle

Info

Publication number: GB2461896A
Application number: GB0813019A
Authority: GB
Inventors: Gary Harding; Richard Parkins; James Howard
Original assignee: Jaguar Cars Ltd; Land Rover UK Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2008-07-17
Filing date: 2008-07-17
Publication date: 2010-01-20
Anticipated expiration: 2028-07-17
Also published as: EP2311137A2; WO2010007591A2; WO2010007591A3; EP2311137B1; GB2461896B; GB0813019D0

Abstract

An antenna assembly or a method of its installation comprises an antenna on a flexible circuit board 14 mounted on the front surface of a support structure 12 formed of dielectric material. The rear surface of the support structure 12 includes at least one mounting element 17 extending away from the rear surface. The mounting element 17 is used to secure the antenna in a spaced manner relative to a motor vehicle body 52 and a signal cable 18 extends through the support 12 and is connected to the circuit board 14. The front surface of the support 12 may be curved to conform to the space available and for a constant gap between the antenna and the vehicle body. Buttresses and bump stops 26 and a foam sealing strip may be arranged between the antenna and an external vehicle component such as a bumper 54. The support structure 12 may be formed as a one piece moulding which includes web, reinforcing ribs, fins and buttresses. The flexible circuit board 14 may be covered and sealed by a film of material secured to the board 14 by an adhesive and/or fasteners. The signal cable 18 may extend into the body of the vehicle to be connected to an amplifier 56 which is in the proximity of the antenna assembly.

Description

Antenna Assembly for a motor vehicle The present invention relates to an antenna assembly for a motor vehicle and more particularly to a device and a method for securing an antenna to a motor vehicle.

Antenna assemblies for mounting antenna on a vehicle body in a hidden location such that the antenna is not visible from the outside of the vehicle are known. WO-A-9629755 discloses an antenna that can be mounted in various locations within the vehicle passenger compartment. WO-A-9840927 provides a cover under which an antenna is positioned and which is positioned within the vehicle body adjacent the vehicle windscreen without impairment to its operation.

EP-A-0383017 describes an antenna which is integrated into a nonconductive motor vehicle bumper and which has separate conductors which are matched to the bumper contours. However, it is apparent that the antenna is greatly endangered in the event of a crash, especially when the antenna has portions which are located in the corner areas of the bumper and which are connected to one another by a line and optionally a line coupler.

Another problem with the prior art antenna assemblies is that it is difficult to maintain a consistent distance from the metallic vehicle body which is used as a ground in modern motor vehicles. Furthermore since the bumpers are typically located tightly against the body for reasons of design and safety, space behind the bumper may not be available for housing the antenna.

It is therefore an object of the present invention to provide a hidden antenna the conductors of which are held at a substantially consistent distance from the ground provided by the vehicle body.

According to the invention a first aspect of the present invention there is provided an antenna assembly for mounting on a motor vehicle body and which comprises a carrier having an antenna support formed from a di-electric material, the support having a front surface with a flexible antenna circuit board thereon, a rear surface having at least one mounting element thereon extending away from the rear surface and in use spacing the antenna from the vehicle body, and a signal cable extending through the carrier is connected to the circuit board.

The front surface is preferably a shallow curviform surface which may be substantially planar.

The carrier sits against a motor-vehicle panel and is secured thereto by suitable means such as fasteners extending through fixing apertures in the mounting element (s).

The or each mounting element may be any desired form or shape and preferably comprises a hollow sleeve having an internal web with fixing apertures passing therethrough. The underside of the web and/or the outer surface of sleeve may be provided with spaced apart reinforcing ribs.

The support may be any desired shape to fit the space available for the antenna and may be in the shape of a curviform irregular quadrilateral with a single mounting element located at one end portion (in use the upper end portion of the carrier) with the remainder of the carrier hanging downwardly in use. The front surface of the support at its other end portion may be provided with resilient bump stops which in use abut the outer surface of a non-metallic vehicle component, for example the rear of a bumper, a spoiler, trim panel or other vehicle body panel. The bump stops may be located on studs or raised bosses on the carrier. Alternatively, a second mounting element may be provided at said other end portion of the carrier.

The carrier is formed as a single dielectric assembly, preferably as a one piece plastics moulding with the mounting element(s) and studs formed integrally. The preferred material is a polyolefinic material such as polypropylene.

The circuit board comprises one or more conductor elements, preferably two conductor elements, each of which is connected to one pole of a multi-pole signal cable, e.g. co-axial cable. The two elements are shaped and dimensioned to resonate for a desired frequency range and may for example be tuned to the DAB III frequency range (174 MHz -240 MHz). The use of a circuit board antenna provides for a simple construction which is economical in both production and installation. The conductor shape and balance between antenna parts can be accurately reproduced. In addition, the circuit board imparts stability to the thin conductors.

The antenna circuit board is covered by an RF transparent non conductive film material, for example polyethylene terapthalate (PET) film so that the antenna is sealed within the assembly.

According to a second aspect of the present invention, there is provided a motor vehicle having an antenna assembly according to the first aspect of the invention, hidden from view behind a vehicle component, the carrier sitting against a motor-vehicle panel and being secured thereto by suitable means associated with the mounting element.

One suitable site for the antenna is in proximity to the ventilation openings which are located on both sides of the boot or trunk compartment in most passenger cars for pressure equalization when the motor vehicle doors are quickly closed. These openings are covered by the bumpers and the antenna assembly is hidden behind the rear bumper.

Preferably, the support and antenna board are shaped to match the contours of the vehicle body so as to maintain a substantially constant distance between the antenna board and the vehicle body grounding.

The antenna assembly may be mounted externally of the vehicle and the signal cable is connected to an amplifier located within the vehicle in proximity with the assembly.

With the carrier mounted on the body, the connector cable passes through an opening in the body for connection to the RF amplifier. Because the antenna and the connecting lead are not components of the bumper, the danger of damage, at least in minor collisions, is greatly reduced compared to bumper antennas.

Furthermore changes in bumper design can be made without impact on the antenna assembly.

According to a third aspect of the present invention, there is provided a method of installation of an antenna on a motor vehicle wherein the antenna is mounted on a carrier having an antenna support formed from a di-electric material, the support having a front surface with a flexible antenna circuit board thereon following the contours of said front surface, a rear surface having at least one mounting element thereon extending away from the rear surface and in use spacing the antenna from the vehicle body, and a signal cable extending through the carrier is connected to the circuit board, the carrier is then mounted or the vehicle body at a suitable installation site and in use will be hidden by other components.

The carrier and antenna are mounted on the vehicle body before the bumper or other component is fitted. This facilitates the vehicle manufacture. Any bumper can be manufactured with suitable form on its rear to accommodate the antenna assembly.

A simple and relatively stable mounting may be achieved by use of screws or other fasteners.

The invention will now be described by way of example with reference to the accompanying drawings of which: -Fig.1 is a plan view of an antenna assembly according to the present invention; Fig.2 is a view of the underside of the assembly shown in Fig.1; Fig.3 is side elevation of the assembly shown in Fig.1; Fig.4 is a schematic drawing of mounting of the antenna to a vehicle; Fig.5 is a second schematic drawing of the antenna mounted on the vehicle, and Fig.6 is a schematic drawing of the antenna system on the vehicle.

With reference to FIGS. 1 to 3, there is shown an antenna assembly 10 for mounting on a motor vehicle body and which comprises a carrier 11 having a shaped antenna support 12 formed from a di-electric material such as an electrically non conductive polymeric material, for example polypropylene. The support 12 is shaped as is required to fit to the space available in its intended location on the vehicle and in this example is in the form of a curviform irregular quadrilateral and having a curved front surface 13 with a flexible antenna circuit board 14 sitting thereon and following the contours of the front surface. In this case the curved surface is substantially planar. The antenna 14 may comprise any desired number of monopole conductors. The present antenna 14 comprises two monopole conductors 15 and 16 etched onto a flexible board as is well known and is covered by an RF transparent non conductive film material 55 (see Fig.6) , for example polyethylene terapthalate (PET) film, so that the antenna board 14 is sealed within the assembly 10. The film 55 may secured to the circuit board 14 by adhesive and fasteners 20. The rear surface 20 of the support 12 may be formed with reinforcing ribs 1 2a thereon.

The rear surface 20 of the support 12 has at least one mounting element 17 thereon extending away from the rear surface 20 and in use spacing the antenna 15, 16 from the vehicle body by a desired distance from a ground surface on the vehicle body. A single core or multi-core connector cable 18, as is required, is connected via a connector 22 passing through the support 12 to the circuit board. In the present example, a coaxial cable 18 has its core 21 connected to one monopole conductor 15 or 16, and the outer shielding 23 connected to the other of the two monopole conductors 16 or 15. The connector 22 may be sealed by encapsulation in resin. A grommet 19 is provided on the cable 18 for sealing a co-operating aperture 51 in the vehicle body 52 (see Fig.5) and the end of the coaxial cable is provided with a connector 53 for connection to a signal amplifier 56.

The mounting element 17 may comprise any suitable form such as a block, hook, integral clip etc. and preferably comprises a hollow sleeve 24 extending away from rear surface 20 by about 50mm and has an internal web 44 with fixing apertures 25 passing therethrough. The underside of the web 44 is provided with reinforcing ribs 46 and the outer surface of the sleeve 24 is reinforced by spaced apart fins or buttresses 27.

A single mounting element 17 is located at one end portion of the support 12 (in use the upper end portion) with the remainder of the carrier hanging downwardly in use. The front surface 13 of the support at its other end portion is provided with resilient bump stops 26 which in use abut the bumper. The bump stops 26 are located on studs or raised bosses (not shown) on the carrier 11. Additionally, or alternatively, a second mounting element 117 (see Fig. 5) could be provided at said other end portion of the support 12.

The carrier 11 may be formed as a one piece plastics moulding with the mounting element(s) and studs formed integrally with the carrier which is preferably formed from a polyolefinic material such as polypropylene. The support 12 may be curviform and is substantially planar and may be slightly curved to follow the contours of the adjacent portion of vehicle body to maintain a substantially constant spacing of the antenna board from the vehicle body grounding.

The antenna board 14, carrier 11, and cable 18 together form a sub-assembly that can be handled using normal care without damaging it. The sub-assembly may be utilised across a range of vehicles. The carrier 11 when mounted on the vehicle is held against a motor-vehicle panel and is secured thereto by fasteners extending through the fixing apertures 25 in the mounting element 17. The antenna is spaced from the ground effect of the vehicle body by the mounting element 17.

With reference now to Figures 4 -6, one suitable location, for the antenna assembly to be mounted to the vehicle body 52, is proximate to the ventilation openings 53 which in most passenger cars are located on both sides of the boot or trunk compartment for pressure equalization when the motor vehicle doors are quickly closed. These openings are covered by the rear bumper 54 and the antenna assembly 10 is hidden behind the rear bumper. The carrier 11 and antenna 14 are mounted externally of the vehicle body before the bumper is fitted. This facilitates the vehicle manufacture. Furthermore, since the antenna 14 is mounted on a separate support 12 from the bumper the likelihood of damage during minor collisions is reduced.

The carrier 12 is secured to the body 52 through the mounting element 17 and hangs from the element 17 at a slight inclination such that a foam sealing strip 28 on the PET film layer is substantially horizontal and in use seals against the bumper 54. Since the antenna assembly 10 is outside of the vehicle body 51 within the bumper 54, the antenna will be exposed to weather and occasionally to wet conditions. This has little effect on the workings of the antenna assembly since the assembly 10 is completely sealed and splash proof.

The connecting cable 18 passes through an aperture 51 into the interior of the vehicle, for example the trunk T. The cable 18 is sealed in the aperture by the grommet 19 and connects with an RF amplifier 56 located within the dry interior of the trunk T. The cable 18 from the assembly 10 to the amplifier 56 can be kept to a minimal length and this helps maintain good signal strength to the amplifier. Signal variability is also reduced by maintaining a substantially constant spacing between the antenna board 14 and the vehicle body ground. The amplifier 56 is then connected via cable 57 to a receiver or tuner 58.

The antenna element is then tuned to the vehicle to resonate at the required frequency range.

Claims

CLAIMS1. An antenna assembly for mounting on a motor vehicle body, the assembly comprises a carrier having an antenna support formed from a di-electric material, the support having a front surface with a flexible antenna circuit board thereon, a rear surface having at least one mounting element thereon extending away from the rear surface and in use spacing the antenna from the vehicle body, and a signal cable extending through the support is connected to the circuit board.
2. An assembly as claimed in Claim 1, wherein the front surface is a curviform surface which is substantially planar.
3. An assembly as claimed in Claim 1 or Claim 2 wherein the or each mounting element comprises a hollow sleeve having an internal web with fixing apertures passing therethrough.
4. An assembly as claimed in Claim 3, wherein the underside of the web is provided with reinforcing ribs.
5. An assembly as claimed in Claim 3 or Claim 4, wherein the outer surface of sleeve is strengthened by spaced apart fins or buttresses,
6. An assembly as claimed in any one of Claims 1 to 5, wherein the support is substantially in the shape of an irregular quadrilateral and a single mounting element is located at one end portion, in use the upper end portion of the carrier.
7. An assembly as claimed in Claim 6 wherein the support at its other end portion is provided with a further mounting element and/or resilient bump stops on its front face.
8. An assembly as claimed in any one of Claims 1 to 7, wherein the carrier is formed as a one piece plastics moulding including mounting element (s).
9. An assembly as claimed in any one of Claims 1 to 8, wherein the antenna circuit board is covered by an RF transparent non conductive film material, so that the antenna is sealed within the assembly secured to the circuit board by adhesive and/or fasteners.
10. A motor vehicle having an antenna assembly as claimed in any one of Claims 1 to 9, hidden behind a vehicle component so that it is hidden from view, the carrier sitting against a motor-vehicle panel and being secured thereto by suitable fixing means associated with the mounting element(s).
11. A motor vehicle as claimed in Claim 10, wherein the support and antenna board are shaped to match the contours of the vehicle body so as to maintain a substantially constant distance between the antenna board and the vehicle body grounding.
12. A motor vehicle as claimed in Claim 10 or Claim 11, wherein the antenna assembly is mounted externally of the vehicle and the signal cable is connected to an amplifier located within the vehicle in proximity with the assembly.
13. A method of installation of an antenna on a motor vehicle wherein the antenna is mounted on a carrier having an antenna support formed from a di-electric material, the support having a front surface with a flexible antenna circuit board thereon following the contours of said front face, a rear surface having at least one mounting element thereon extending away from the rear surface and in use spacing the antenna from the vehicle body, and a signal cable extending through the carrier is connected to the circuit board, the carrier is then mounted on the vehicle body at a suitable installation site and in use will be hidden by other components.
14. A method as claimed in Claim 13, wherein the assembly is on the vehicle in proximity to the vehicle bumper prior to fitting of the vehicle rear bumper, and the antenna assembly is hidden behind the subsequently fitted rear bumper.
15. A method as claimed in Claim 13 or Claim 14, wherein the carrier is mounted externally of the body, and the signal cable passes through an opening in the body for connection to an RF amplifier located within the vehicle body in proximity to the antenna assembly to minimise the cable length..
16. A method as claimed in any one of Claims 13 to 15, wherein the antenna support and antenna board are shaped to the contours of the adjacent portion of vehicle body to maintain a substantially constant spacing of the antenna from the vehicle body grounding.