EP1689025A1

EP1689025A1 - Compact multiband antenna.

Info

Publication number: EP1689025A1
Application number: EP06101259A
Authority: EP
Inventors: Andrea Tagliapietra
Original assignee: Calearo Antenne SpA
Current assignee: Calearo Antenne SpA
Priority date: 2005-02-03
Filing date: 2006-02-03
Publication date: 2006-08-09
Also published as: ITVI20050031A1

Abstract

Compact multiband antenna (1) comprising at least one metallic element (2), for the reception of radio-frequency signals relating to a plurality of frequency bands, and a multilayer printed circuit (3; 103), combined with the metallic element (2), provided with a first end layer (4; 104), made of conductive material and on which a plurality of electronic components (5) are arranged to create at least a first electronic circuit, and a second end layer (6; 106) opposite the first (4; 104), also made of conductive material and on which a plurality of electronic components (7) are arranged to create at least a second electronic circuit. The multilayer printed circuit (3; 103) comprises at least one intermediate layer (8; 108), made of conductive material and separated from said first and second end layers (4, 6; 104, 106) by one or more layers of insulating material (9; 109), said at least one intermediate layer (8; 108) constituting an earth reference electrically connected to said electronic circuits and suited to electromagnetically separate said first and second end layers (4, 6; 104, 106) from one another.

Description

The invention concerns a compact multiband antenna particularly suitable for use on motor vehicles.
It is known that a number of receiver antennas for radio signals on different frequency bands and for different applications can be necessary on motor vehicles.
All said antennas are combined with electronic circuits for initial processing of the signals received, said processing consisting generally in filtering, impedance adaptation and amplification of the radio signal received.
It is also known that the market trend is to offer multi-resonant, i.e. multiband, antennas.
The current state of the art comprises the production of multiband antennas, i.e. antennas able to receive signals on several frequency bands and for different applications, for example mobile telephone service, AM, FM and DAB radio, satellite navigators.
It is therefore necessary to incorporate in them the reception circuits for each application.
Said circuits operate with radio signals belonging to different frequency bands and, therefore, can obviously produce interference with one another, hence it is important to insulate them in the best possible way.
It is known that, more and more often, the antennas available on the market incorporate the reception circuits in their supporting base in order, among other things, to make the antennas as least intrusive as possible with respect to the structure of the motor vehicle.
Said tendency, however, can conflict with the demand, in the motor vehicle market, for small compact antennas with attractive aerodynamic profile.
Two types of multiband antenna exist on the market:

a first type which features one single printed circuit that comprises all the necessary electronic circuits, arranging the electronic components of the various circuits so that they are mixed and providing earth areas arranged in such a way as to favour integration, thus minimising the space occupied;
a second type in which each reception circuit is provided on a printed circuit separate from the others, thus favouring electrical insulation.

The drawbacks of said two different approaches are obvious:

in the first case antennas are obtained in which there is a high level of reciprocal radio-frequency interference among the electronic components of the various reception circuits which can, in some cases, considerably affect the quality of the application;
in the second case antennas are obtained having a supporting base of considerable dimensions which permanently and negatively affects, especially in the case of luxury cars, the appearance of the motor vehicle.

The aim of the present invention is to overcome the above-mentioned drawbacks.
In particular, the aim of the present invention is to produce a multiband antenna for motor vehicles that consists of one single multi-resonant shaft and in which all the necessary reception circuits are integrated in the same printed circuit, but with a reciprocal degree of radio-frequency insulation greater than that offered by the equivalent antennas belonging to the known art and having all the electronic reception circuits arranged on one single printed circuit, or in any case such as to minimise or make imperceptible said reciprocal interferences.
Advantageously, the antenna of the invention has a radio-frequency insulation among the electronic reception circuits comparable to the insulation obtained by arranging the electronic circuits separately on different printed circuits, but with reduced overall dimensions.
Said aim and advantage are achieved by a compact multiband antenna which, according to the first claim, comprises at least one metallic element for the reception of radio-frequency signals relating to a plurality of frequency bands, and a multilayer printed circuit combined with said metallic element, provided with a first end layer, made of conductive material and on which a plurality of electronic components are arranged constituting at least a first electronic circuit, and a second end layer opposite the first, also made of conductive material and on which a plurality of electronic components are arranged constituting at least one second electronic circuit, characterised in that said multilayer printed circuit comprises at least one intermediate layer, made of conductive material and separated from said first and second end layer by one or more layers of insulating material, said intermediate layer constituting an earth reference electrically connected to said electronic circuits and suited to electromagnetically separate said first and second end layers from one another.
According to the preferred embodiment, on the first end layer and on the second end layer several distinct areas are identified, electrically separated from one another, on each of which all the electronic components of one single electronic reception circuit are arranged.
Each of said electronic circuits, and therefore each of said areas, corresponds to a earth layer which functions as an earth reference for said circuit.
In particular, said layer obtains the favourable effect to electromagnetically separate from one another the electronic circuits present on different end layers.
According to a particular variant, there is one single intermediate earth layer for all the electronic circuits.
According to further variants, between the first end layer and the second end layer there are, in addition to one or more earth layers, one or more additional layers for the creation of electrical interconnections by means of tracks of conductive material between distinct points of different layers.
Said aim and advantage will be illustrated in greater detail in the description of preferred embodiments of the invention, which is provided for indicative purposes and is not binding, with reference to the attached drawings, in which:

fig. 1 is an exploded section view of an embodiment of the antenna of the invention;
fig. 2 is a cross-section view of the multilayer printed circuit belonging to the antenna of the invention;
fig. 3 is a cross-section view of a different embodiment of the multilayer printed circuit belonging to the antenna of the invention;
fig. 4 is a cutaway view of the multilayer circuit belonging to the antenna of the invention.

The multiband antenna subject of the invention is shown in a particular embodiment in fig. 1, where it is indicated as a whole by 1.
As can be observed, it comprises a metallic element 2 for the reception of radio-frequency signals relating to a plurality of frequency bands, and a multilayer printed circuit 3 combined with the metallic element 2.
The printed circuit 3 is provided with a first end layer 4, made of conductive material and on which a plurality of electronic components 5 are arranged to create a first electronic circuit.
On the side opposite the first end layer 4 there is a second end layer 6, also made of conductive material and on which a plurality of electronic components 7 are arranged to create a second electronic circuit.
According to the invention, the printed circuit 3 comprises two intermediate layers 8 made of conductive material and separated from each other and from the end layers 4, 6 by one or more layers of insulating material 9, each of said intermediate layers 8 constituting an earth reference for the above-mentioned electronic circuits.
Advantageously, since the intermediate layers 8 consist of a continuous surface of conductive material which identifies a covering area substantially the same as the area identified by the printed circuit, the earth reference they offer is such that the electronic circuits are less susceptible, with respect to the equivalent antennas belonging to the known art, to the reciprocal radio-frequency interferences.
In different embodiments, not shown, there are more than two electronic circuits and each of them has all its electronic components arranged on a distinct area of one of the two end layers.
Each of said areas therefore contains the electronic components of only one of the electronic circuits provided on the printed circuit.
Advantageously, the arrangement of the electronic components belonging to each individual circuit on distinct areas increases their radio-frequency insulation as it prevents sensitive components of different circuits from being positioned too near one another.
In further embodiments, there are one or more than one intermediate layers constituting the earth reference and each of them constitutes the sole earth reference for one or more electronic circuits provided on the printed circuit.
Advantageously, also said further embodiments increase the level of insulation between the electronic circuits present on the printed circuit, since it is possible to assign the electronic circuits, that are particularly sensitive to reciprocal radio-frequency interferences, a different intermediate layer as earth reference. As said, the end layers 4, 6 and the intermediate layers 8 are separated from one another by layers of insulating material 9 which, in the preferred embodiment, consist of a resin mechanically reinforced by fibreglass and also constitute support for the end layers 4, 6 and intermediate layers 8.
In the preferred embodiment, the conductive material of said end layers 4, 6 and of said intermediate layers 8 is copper.
The printed circuit 3, shown in cross section in fig. 2 and belonging to the antenna 1 of the invention, is provided with two through paths 10, 11, housing two connection elements 20, 21, which can be seen in fig. 1, for input and output of the radio-frequency signals received.
Said paths 10, 11 cross the printed circuit 3 throughout its cross section and constitute a mechanical support for the connection elements 20, 21.
A further through path 12 is also provided for connection of the printed circuit 3 to the metallic element 2 for reception of the radio-frequency signals.
As regards said metallic element 2, in the preferred embodiment it consists of a multi-resonant shaft 13 provided with an intermediate blocking element 14.
The latter insulates, in radio-frequency, the lower part of the metallic element 2, resonating at higher frequency, from the upper part, so as to optimise reception of radio signals belonging to different frequency bands.
In different embodiments, there are more than one blocking elements and the metallic shaft can therefore receive radio signals on a plurality of different bands.
The embodiment described so far is provided only as an example and therefore does not constitute a limitation for the construction of further variants. According to a different embodiment example, the printed circuit 103 belonging to the antenna of the invention includes several additional layers 115 arranged between the end layers 104, 106, as can be seen in fig. 3.
Said additional layers 115 consist of tracks of conductive material to provide interconnections among different points of different layers.
Fig. 4 shows a cutaway view of the printed circuit 3.
The compact multiband antenna therefore achieves the goals set.
In particular, a compact multiband antenna is produced consisting of one single multi-resonant shaft with all the necessary reception circuits incorporated in the same printed circuit, but with a higher level of reciprocal radio-frequency insulation than that offered by the equivalent antennas belonging to the known art and having all the electronic reception circuits arranged on one single printed circuit.
Upon implementation, further changes may be made to the antenna of the invention which, although not shown in the drawings and not described, will all be considered protected by the present patent if they come under the contents of the following claims.

Claims

Compact multiband antenna (1) comprising at least one metallic element (2), for the reception of radio-frequency signals relating to a plurality of frequency bands, and a multilayer printed circuit (3; 103), combined with said metallic element (2), provided with a first end layer (4; 104), made of conductive material and on which a plurality of electronic components (5) are arranged to create at least a first electronic circuit, and a second end layer (6; 106) opposite the first (4; 104), also made of conductive material and on which a plurality of electronic components (7) are arranged to create at least a second electronic circuit, characterised in that said multilayer printed circuit (3; 103) comprises at least one intermediate layer (8; 108), made of conductive material and separated from said first and second end layers (4, 6; 104, 106) by one or more layers of insulating material (9; 109), said at least one intermediate layer (8; 108) constituting an earth reference electrically connected to said electronic circuits and suited to electromagnetically separate said first and second end layers (4, 6; 104, 106) from one another.
Multi-resonant antenna (1) according to claim 1), characterised in that in at least one of said end layers (4, 6; 104, 106) one or more distinct areas can be identified, in each of which the electronic components (5, 7) of one of said electronic circuits are arranged.
Multi-resonant antenna (1) according to claim 1), characterised in that one or more additional layers (115) made of conductive material are arranged between said end layers (104, 106).
Multi-resonant antenna (1) according to claim 3), characterised in that at least one of said additional layers (115) consists of a plurality of tracks made of conductive material.
Multi-resonant antenna (1) according to claim 1), characterised in that said metallic element (2) consists of a composite shaft (13) along which one or more blocking elements (14) for radio-frequency signals can be identified.
Multi-resonant antenna (1) according to claim 1), characterised in that said conductive material is copper.
Multi-resonant antenna (1) according to claim 1), characterised in that said insulating material is a resin mechanically reinforced by a fibreglass web.
Multi-resonant antenna (1) according to claim 1), characterised in that said multilayer printed circuit (3; 103) is crossed by one or more through paths (10, 11, 12; 110, 111, 112).
Multi-resonant antenna (1) according to claim 8), characterised in that said paths (10, 11, 12; 110, 111, 112) constitute a mechanical support for connection elements (20, 21) designed to electrically connect said electronic circuits to external elements.
Multi-resonant antenna (1) according to claim 9), characterised in that one of said external elements is said metallic receiving element (2).
Multi-resonant antenna (1) according to claim 9), characterised in that one of said external elements is an electronic reception device.