WO2019048902A1

WO2019048902A1 - Antenna device

Info

Publication number: WO2019048902A1
Application number: PCT/IB2017/055337
Authority: WO
Inventors: Marco De Gregorio; Matteo FRANZAN; Matteo CANALE; Andrea Polo Filisan
Original assignee: Calearo Antenne S.P.A. Con Socio Unico
Priority date: 2017-09-05
Filing date: 2017-09-05
Publication date: 2019-03-14
Also published as: EP3625849B1; EP3625849A1

Abstract

An antenna device (1) comprising an upper half-shell (3), a lower antenna base (4) that is coupled to the half-shell (3) so as to create an antenna housing, electronic means (6) arranged inside the antenna housing to receive an antenna signal, and an antenna unit (7), which is arrange inside the antenna housing and is electrically connected to the electronic means (6) to supply and/or receive the antenna signal. The antenna unit (7) comprises a planar antenna (9) provided with at least one spiral-shaped planar portion (8) made of an electrically conductive material.

Description

"ANTENNA DEVICE"

TECHNICAL FIELD

The present invention relates to an antenna device. In particular, the present invention relates to an antenna device that can preferably be installed on a vehicle, conveniently a powered vehicle such as, for example, a motor vehicle or a similar vehicle, to which the following description shall make explicit reference, without any loss of generality.

BACKGROUND ART

There are known antenna devices that are shaped like a shark fin and are structured to be permanently fixed on the roof of a motor vehicle.

An antenna device of the above-specified type is described, for example, in American Patent US 9,287,610 B2 and essentially comprises an external protective half-shell and an antenna base that is coupled to the bottom of the protective half-shell so as to create a closed antenna housing. Inside the antenna housing, the antenna device also comprises: an upper metal element shaped like an umbrella and defining a capacitive component, a signal amplifier substrate arranged on the lower antenna base beneath the umbrella-like element, and a rectangular support frame that is arranged on a central vertical plane between the amplifier substrate and the umbrella-like element and is structured to support the latter. A wire coil is arranged on a vertical side of the support frame and acts as an electrical connection between the umbrella-like element and the amplifier substrate to supply the antenna signal to the latter. In detail, the cylindrical wire coil is placed centrally in the antenna housing beneath the umbrella-like element, and is formed by filiform turns wound about a vertical axis so as to form a cylindrical winding that extends in a vertical direction. The vertical wire coil constitutes an inductive component and, with the upper umbrella-like capacitive element, forms an antenna resonating in the FM frequency band.

One technical problem of the above-described antenna device is represented by the fact that the vertical cylindrical wire coil and the associated central support frame occupy part of central space beneath the umbrella-like element and thus cause undesired bulk that significantly reduces the free space available in the antenna housing.

This technical problem is particularly critical in antenna devices, especially new-generation ones, as, on the one hand, there is the current need to be able to add new antenna types to the traditional antennas operating in the AM/FM and DAB bands in order to perform additional communications functions, such as V2V, V2X, Bluetooth, WiFi, GNSS and SDARS, and, on the other hand, there are restrictions on the maximum external size of the antenna device established by type-approval regulations, which impose a maximum housing height threshold of 70 mm that cannot not be exceeded.

Another antenna device is described in patent application US 2012/0001811, which teaches how to produce one or more radiant inductive elements directly on the outer surface of the upper half-shell. On the one hand, this solution requires complex and expensive operations for making the substrates of the radiant elements on the outer wall of the half-shell, and, on the other, is particularly exposed to the risk of damage to the radiant elements.

The applicant has therefore carried out in-depth research on antenna devices, with the aim of identifying a simple and inexpensive solution that enables achieving the objective of increasing the internal space available in the antenna housing. Another objective is that of maximizing the decoupling of the antenna unit in the antenna device from other radiant elements operating at neighbouring frequencies. DISCLOSURE OF INVENTION

The object of the present invention is therefore that of providing a solution that enables achieving the above-indicate objectives .

This object is achieved by the present invention in so far as it relates to an antenna device comprising an upper half- shell, a lower antenna base that is coupled to said half-shell to create an antenna housing, electronic means that are arranged inside said antenna housing and are designed to receive and/or supply an antenna signal, and at least one antenna unit provided with a planar antenna that is arranged inside said antenna housing to receive and/or supply said antenna signal from/to said electronic means and comprises a spiral-shaped planar portion made of an electrically conductive material. The spiral-shaped planar portion preferably comprises a series of spires with an approximately flattened shape, which are laid out approximately concentrically on a same surface approximately orthogonal to an axis (hereinafter axis B) and extend on said surface so as to occupy a progressively increasing surface area. Preferably, in said planar antenna, the spiral-shaped planar portion forms an inductive-capacitive component designed to make the planar antenna resonate in at least one predetermined frequency band. Preferably, the spiral-shaped planar portion is arranged in said antenna housing in a position approximately adjacent to the upper inner surface of said half-shell, set apart from said antenna base. Preferably, the spiral-shaped planar portion is arranged on a lateral portion of said planar antenna. Preferably, the spiral-shaped planar portion is arranged in a rear portion of said planar antenna. Preferably, the spiral-shaped planar portion is arranged in a front portion of said planar antenna. Preferably, the turns of said spiral-shaped planar portion have about a polygonal shape, or about a circular shape, or about a elliptical shape, or about a spiral-like shape. Preferably, the planar antenna comprises a sheet made of an electrically conductive material. Preferably, the spiral-shaped planar portion is obtained on said sheet so as so as to form a single/one-piece body therewith .

Preferably, the planar antenna has about a rectangular form and is shaped in order to have about a semicircular section transversal to the longitudinal axis, for example an inverted U-shape. Preferably, the planar antenna comprises a solid planar portion (not spiral-shaped) made of an electrically conductive material that is electrically connected to said spiral-shaped planar portion and, with the latter, forms an inductive-capacitive component designed to make said planar antenna resonate in a predetermined frequency band. Preferably, the planar antenna has a profile, or shape, approximately complementary to the shape of the inner surface of the half-shell. Preferably, the spiral-shaped planar portion is on a portion of the sheet itself. Preferably, the spiral-shaped planar portion is cut out on the sheet. Preferably, the planar antenna is made by printing/depositing a thin film of electrically conductive material on a surface of a sheet of insulating material in order to form a spiral- shaped planar portion thereon. Preferably, the insulating sheet has a rectangular shape, and the remaining area of the surface of the sheet outside the area occupied by the spires is covered by a uniform and continuous layer of electrically conductive material so as to form at least one electrically conductive polygonal portion defining a solid planar conductive portion. Preferably, the sheet of insulating material comprises a thin, easily flexible/bendable sheet of insulating material. Preferably, a metallic film, shaped on the basis of the pattern/geometry of the planar antenna to be obtained, is connected/permanently fixed to the surface of the planar antenna's flexible insulating sheet. Preferably, the metallic film can be shaped so as have the spiral-shaped planar portion and a solid planar conductive portion. Preferably, a paint made with a conductive material can be applied on the flexible insulating sheet in order to form a conductive surface layer forming the aforementioned spiral- shaped planar portion and a conductive surface layer forming the aforementioned solid planar conductive portion electrically connected to the spiral-shaped planar portion. Preferably, the solid planar portion is electrically connected to an end of a spire of the spiral-shaped planar portion. Preferably, the solid planar portion made of an electrically conductive material is electrically connected to the end of the outer spire of the spiral-shaped planar portion. The planar antenna is preferably designed to resonate at one or more frequencies comprised in the FM frequency band and/or the DAB frequency band.

Preferably, the axis B of the turns of the spiral-shaped planar portion is transversal to the antenna base. Preferably, the axis B of the turns of the spiral-shaped planar portion is orthogonal to the antenna base. Preferably, the axis B of the turns of the spiral-shaped planar portion is approximately parallel to the antenna base. Preferably, the antenna device comprises fastening means structured to permanently couple said planar antenna onto the inner surface of said half-shell. Preferably, the antenna device comprises support means made of an insulating material that are connected to said antenna base and are structured in order to support, on their upper part, said planar antenna in a position adjacent to the upper inner surface of said half- shell. Preferably, the support means comprise a support frame provided with about a rectangular upper plate-like body, on the top surface of which said planar antenna is rested, and one or more lateral spacer elements that connect one or more sides of said plate-like body to one or more sides of said antenna base. Preferably, the support frame also comprises a series of lateral spacer brackets or rods. Preferably, each lateral spacer rod extends approximately orthogonal to the antenna base and has a top end permanently connected to the plate-like body, at one side thereof. Preferably, the bottom end of the spacer rod is connected to a lateral portion of the antenna base.

Preferably, said electronic means are arranged on said antenna base beneath said planar antenna and are electrically connected to said spiral-shaped planar portion by at least one conductive connection line to supply/receive the antenna signal. Preferably, the conductive connection line comprises a wire made of a conductive material that extends into said antenna housing on the inner surface of said half-shell. Preferably, the electronic means are provided with a receive and/or supply terminal for said antenna signal; said terminal being directly connected to an end/terminal of a spire of said spiral-shaped planar portion by a direct electrical connection, without electric and/or electronic inductive components. Preferably, the electrical connection between the terminal of said electronic means and the end/terminal of a turn of said spiral-shaped planar portion is constituted by an electric branch without electric and/or electronic inductive components. Preferably, the electrical connection between the terminal of said electronic means and the end/terminal of a turn of said spiral-shaped planar portion is constituted by a wire made of an electrically conductive material, and has no wire coils. Preferably, the spiral-shaped planar portion has two terminals defined by the ends of two respective turns, one terminal being electrically connected to the terminal of the electronic means by the electrical connection, and the other terminal electrically connected to the solid planar conductive portion .

Preferably, the antenna device comprises two planar antennas that are arranged in said antenna housing in positions approximately aligned with each other and are provided with respective spiral-shaped planar portions operating in respective frequency bands.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the accompanying drawings, which illustrate some non- limitative embodiments, in which:

- Figure 1 is an external perspective view of an antenna device made according to the principles of the present invention;

- Figure 2 is a side view of the antenna device shown in Figure 1;

- Figure 3 is a rear view of the antenna device shown in Figure 1;

- Figure 4 is a front view of the antenna device shown in Figure 1;

- Figure 5 is a schematic axonometric view, with parts in section and parts removed for clarity, of the antenna device made according to a preferred embodiment;

- Figure 6 is a side view, with parts in section and parts removed for clarity, of the antenna device shown in Figure 5;

- Figure 7 is a perspective view, on an enlarged scale, of a planar antenna of the antenna device shown in Figure 5;

- Figure 8 is a top view of the planar antenna shown in Figure 7;

- Figure 9 is a side view, with parts in section and parts removed for clarity, of the antenna device made according to a preferred embodiment;

- Figure 10 is an axonometric view, with parts in section and parts removed for clarity, of the antenna device according to an alternative embodiment;

- Figure 11 is a schematic side view, with parts in section and parts removed for clarity, of the antenna device shown in Figure 10;

- Figure 12 is a perspective view, on an enlarged scale, of a planar antenna of the antenna device shown in Figure 11; - Figure 13 is a top view of the planar antenna shown in Figure 12;

- Figure 14 is a schematic axonometric view, with parts in section and parts removed for clarity, of the antenna device according to an alternative embodiment;

- Figure 15 is a side view, with parts in section and parts removed for clarity, of the antenna device shown in Figure 14;

- Figure 16 is a perspective view, on an enlarged scale, of a planar antenna of the antenna device shown in Figure 14;

- Figure 17 is a top view of the planar antenna shown in Figure 16;

- Figure 18 is a schematic axonometric view, with parts in section and parts removed for clarity, of the antenna device according to an alternative embodiment;

- Figure 19 is a side view, with parts in section and parts removed for clarity, of the antenna device shown in Figure 18;

- Figure 20 is a perspective view, on an enlarged scale, of a planar antenna of the antenna device shown in Figure 18;

- Figure 21 is a top view of the planar antenna shown in Figure 20;

- Figure 22 is a schematic top view of a planar antenna according to an alternative embodiment;

- Figure 23 is a perspective view, with parts in section and parts removed for clarity, of the antenna device made according to an alternative embodiment;

- Figure 24 is a side view, with parts in section and parts removed for clarity, of the antenna device shown in Figure 23;

- Figure 25 is a perspective view, with parts in section and parts removed for clarity, of the antenna device made according to an alternative embodiment;

- Figure 26 is a side view, with parts in section and parts removed for clarity, of the antenna device shown in Figure 25; while

- Figure 27 is a graph of the average antenna signal gain obtained with the planar antenna in the antenna device shown in Figures 18-21. BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will now be described in detail, with reference to the accompanying figures, to enable an expert in the field to embody it and use it. Various modifications to the described embodiments will be immediately obvious to experts in the field, and the generic principles described herein can be applied to other embodiments and applications without departing from the scope of the present invention, as defined in the appended claims. Thus, the present invention is not intended to be limited to the embodiments set forth herein, but is to be accorded the widest scope consistent with the principles and features described, illustrated and claimed herein .

Referring to the accompanying Figures 1 to 27, reference numeral 1 indicates, as a whole, an antenna device made according to the present invention. Figures 1 and 2 are respectively a perspective view and a side view that show an illustrative external configuration of the antenna device 1 according to the present invention. Figures 3 and 4 are respectively a rear view and a front view that show an illustrative external configuration of the antenna device 1 according to the present invention.

As shown in the accompanying figures, the antenna device 1 made according to the example of the present invention, is structured for being preferably fixed on the roof 2 of a vehicle (not shown) . In other words, the antenna device 1 can conveniently be an antenna device 1 for vehicles, preferably motor vehicles or similar. The antenna device 1 has a longitudinal axis A and comprises a half-shell 3 approximately defining an upper outer cover, and a lower antenna base 4 that is permanently coupled to the half-shell 3 at the opening, in order to form an antenna housing, for example a closed antenna housing. The external half-shell 3 can be made of a material suitable to allow the passage of radio waves. For example, the half-shell 3 could be made of plastic materials or similar materials, for example, based on one or more synthetic resins suitable for the above-indicated purpose.

In one embodiment shown in Figures 1 to 4, the half-shell 3 can be conveniently shaped in the form of a shark fin. Nevertheless, it is understood that the present invention is not limited to a half-shell 3 in the form of a shark fin, but can also be extended/applied to antenna devices 1 provided with half-shells 3 having any shape, preferably, but not necessarily, shapes with aerodynamic profiles suitable for motor vehicles.

In the embodiment shown in the accompanying figures, the shark-fin half-shell 3 has two portions, hereinafter indicated as the front portion 3a and rear portion 3b (for greater clarity, Figure 2 shows a vertical broken line K that separates the two portions 3a and 3b) . The front portion 3a can have, for example, a tapered longitudinal section (on the vertical centre plane Ml passing through longitudinal axis A) , which progressively narrows towards the antenna base 4 beneath, until it reaches the front end of the antenna housing, so as to substantially form a tip. In other words, the front portion 3a can have about a triangular longitudinal section. The rear portion 3b can instead have a roughly rectangular longitudinal section (on the centre plane Ml) and an internal volume larger than the internal volume of the front portion 3a (Figures 6, 9, 11 and 19) . It is understood that the profile and dimensions of the antenna housing with a shark-fin shaped half-shell 3, i.e. portion 3a and/or portion 3b, can vary on the basis of the type and/or number of communications functions that the antenna device 1 must implement. For example, the antenna housing with a shark-fin shaped half-shell 3 of the antenna device 1 could be shaped and sized in order to have a length (measured along the longitudinal axis A) of between approximately 155 mm and approximately 190 mm, a width (measured orthogonally to the longitudinal axis A) of between approximately 62 mm and approximately 80 mm, and a height of less than approximately 70 mm, preferable greater than approximately 60 mm.

The antenna device 1 can also be provided with a lower connection and fastening member 5 formed, for example, by a metal element preferably, but not necessarily, tubular, which projects in a cantilevered fashion from the bottom surface of the antenna base 4, orthogonal to the latter, so to engage in use, an aperture (for example a through hole) made in the roof 2 of the vehicle. The tubular element can have cables /wires / fibres or similar (not shown) passing through it for electrically connecting the antenna device 1 to electronic communications equipment (not shown) present on board the vehicle . Figures 5 to 9 show an internal configuration of the antenna device 1 according to a preferred embodiment of the present invention. Figure 5 is a perspective view of the antenna device 1 with the half-shell 3 sectioned longitudinally along the section line I-I (shown in Figure 4) . Some internal parts/components of the antenna device 1 have been removed in Figure 5 for greater illustrative clarity of the present invention .

In the embodiment shown in the accompanying figures, the antenna base 4 can comprise a lower insulating plate or base 4a made of an electrically insulating material, for example a plastic material or similar, which, in use, can abut with its outer surface (bottom in Figure 5) against the roof 2 of the vehicle. In addition, the antenna base 4 can comprise a conductive substrate or plate or base 4b made of an electrically conductive material, metal for example, arranged permanently resting on the surface, preferably the inner (top) surface, of the insulating base 4a.

In the embodiment shown in the accompanying figures, the antenna device 1 also comprises a processing device 6, which is arranged inside the antenna housing and is equipped with a connection terminal 6a designed to receive and/or supply an antenna signal. In the example shown, the processing device 6 is integrated/ included/contained in a printed circuit board (PCB) , in turn is provided with at least one terminal corresponding to terminal 6a for receiving and/or supplying the antenna signal. Preferably, the printed circuit board containing the processing device 6 can be arranged and permanently connected in a known manner (with screws or similar systems) on the inner surface of the antenna base 4 so as to be located above the conductive base 4b, preferably in a position adjacent to the latter. The printed circuit board containing the processing device 6 can also be conveniently positioned so as to face and be immediately adjacent to the inner rear surface of the antenna base 4, so as to be facing, and beneath, the rear portion 3b of the half-shell 3.

The processing device 6 can be configured in order to perform analogue and/or digital processing on the antenna signal. To this end, the processing device 6 can comprise at least one amplifier circuit designed to amplify the antenna signal. However, in addition to, the printed circuit board of the processing device 6 can additionally or alternatively comprise other antenna signal processing and treatment circuits, such as, for example: a filter circuit and/or an equalization circuit and/or a modulation and demodulation circuit. The analogue/digital processing methods performed on an antenna signal by means of electronic circuits are known and, not being the main subject of the present invention, will not be described any further. In the embodiment shown in the accompanying figures, the antenna device 1 also comprises at least one antenna unit 7, which is arranged inside said antenna housing beneath the half-shell 3 and is connected to the processing device 6 by an electrical connection to receive and/or supply said antenna signal .

Conveniently, the antenna unit 7 comprises a planar antenna 9 provided with at least one spiral-shaped planar portion 8 made of an electrically conductive material. The spiral-shaped planar portion 8 in the planar antenna 9 forms an inductive- capacitive circuit designed to resonate in at least one predetermined frequency band. The spiral-shaped planar portion 8 comprises a series of approximately coplanar spires substantially set apart from one another. The spires of the spiral-shaped planar portion 8 are substantially concentric to each other with respect to a common axis B and lay on a same surface approximately orthogonal to axis B. The spires extend over the surface so as occupy a progressively increasing surface area. In other words, the spires of the spiral-shaped planar portion 8 extend over the same surface such that, they progressively move away from axis B and, are delimited by an inner spire adjacent to axis B and enclosed by the other turns and an outer spire, opposite to the inner spire and enclosing the remaining spires. In the example shown, the spires of the spiral-shaped planar portion 8 extend on a roughly horizontal plane. It is understood that the surface on which the spires forming the spiral-shaped planar portion 8 lie, can have any geometry/ shape , for example, flat (such as a plane for example) and/or curved (such as a portion of a segment of a sphere for example) or similar. The spires that form the spiral-shaped planar portion 8 are conveniently flattened. For example, the spires could be formed by a continuous spiral- shaped metal strap wound around the axis B and preferably having a widened, roughly rectangular, cross-section. It is understood that the width and thickness of the spiral-shaped metal strap can be preferably determined on the basis of the frequency band of the antenna unit 7.

In the preferred embodiment shown in Figures 5 to 12 and 22, in which the turns lie approximately coplanar to one another on a more or less horizontal surface (approximately parallel to the antenna base) , the axis B is approximately transversal to the plane on which the antenna base 4 lies. In the alternative embodiment shown in Figures 14 to 21, the axis B of the turns of the spiral-shaped planar portion 8 is approximately orthogonal to the antenna base 4. It is understood that the present invention should not be considered as limited to an antenna device in which the turns of the spiral-shaped planar portion 8 extend over a surface so as to have axis B transversal or orthogonal to the antenna base 4, but can provide for other embodiments in which axis B has a different position, i.e. not transversal/orthogonal. For example, according to an alternative embodiment described in detail hereinafter and shown in Figures 23 to 25, where the turns lie approximately coplanar to each other on an approximately vertical surface portion of the planar antenna (approximately orthogonal to the antenna base) , the spiral- shaped planar portion 8 is arranged so as to have the axis B approximately parallel to the antenna base 4.

The planar antenna 9 is shaped in order to be arranged in a position preferably immediately adjacent to the inner surface of the half-shell 3. Conveniently, the planar antenna 9 is shaped such that it can be arranged in a position immediately adjacent to the inner surface, preferably on the upper part of the half-shell 3. In the embodiment shown in the accompanying figures, the planar antenna 9 is shaped so as to be conveniently arranged in a position immediately adjacent to the upper inner surface of the rear portion 3b of the half- shell 3 (Figures 5, 6, 9, 10, 14, 15 and 19) . In the preferred embodiment shown in the accompanying figures, the planar antenna 9 is constituted by a planar plate-like element, separate and independent of the half-shell 3. In other words, the planar antenna 9 does not constitute part of the half-shell 3, but is formed by a single flat plate-like element. Nevertheless, it is understood that, as will be explained hereinafter, the planar antenna 9 can be connected to the half-shell 3 by fastening means. In the preferred embodiment shown in the accompanying figures, the planar antenna 9 has about a rectangular shape (if seen from above, as in Figure 8) and is shaped in order to have about a semicircular cross-section along the longitudinal axis A, for example, an inverted-U shape. As shown in the embodiments illustrated in the accompanying figures, the planar antenna 9 can conveniently have a profile/shape approximately complementary to the shape of the inner surface of the half-shell 3. Advantageously, the planar antenna 9 can have a shape approximately complementary to the shape of the inner surface of the rear portion 3b of the half-shell 3 in order to extend in the antenna housing while remaining adjacent, i.e. following the profile/shape of the upper inner surface of the latter. The planar antenna 9 can have a substantially concave shape, where the concavity faces the antenna base 4 beneath. For example, the planar antenna 9 could approximately have the shape of a saddle or half- cylinder, or a half-cone or any other similar concave shape. The half-shell 3 is arranged above the planar antenna 9, approximately straddling the latter.

According to a preferred embodiment, the planar antenna 9 can comprise, for example, a thin sheet or film (for example with a thickness between approximately 0.05 and approximately 0.5 mm) , while the spiral-shaped planar portion 8 can be conveniently created on a portion of the sheet. The sheet can be made of a metal material, for example, copper or aluminium or similar materials, while the spiral-shaped planar portion 8 can be conveniently obtained on the sheet so as to form a single body with the latter. For example, the spiral-shaped planar portion 8 can be obtained on the body of the sheet by means of a cutting process, laser cutting for example, or by punching or any similar cutting operation. The cutting process enables making, for example, a linear through aperture or slot (of small width) in the sheet that extends without interruption (without continuous solution) along a spiral path about axis B so as to form the turns of the spiral-shaped planar portion 8 on the sheet.

It should be specified that the spiral-shaped planar portion 8 preferably occupies one part of the sheet. The remaining portion of the sheet not occupied by the spiral-shaped planar portion 8 forms a planar portion, hereinafter indicated as the "solid planar conductive portion" (i.e. a uniform and continuous portion that is not spiral-shaped) , which, in use, forms a capacitive component electrically connected to the spiral-shaped planar portion. In other words, the spiral- shaped planar portion 8 and the solid planar conductive portion form an inductive-capacitive component designed to make the planar antenna 9 resonate in one or more frequencies ranging in at least the predetermined frequency band. Nevertheless, it is understood that the present invention is not limited to producing the planar antenna by means of a thin metal sheet, but can provide for other alternative solutions.

For example, in an alternative embodiment (not shown) in which the use of a metal sheet is not contemplated, the planar antenna 9 is made using a sheet of insulating material and the printing/depositing of a thin layer of electrically conductive material on a surface of the sheet of insulating material, so as to form the spiral-shaped planar portion 8. One or more approximately coplanar and substantially concentric linear conductive tracks can be made on the sheet of insulating material with predetermined widths and thicknesses, defining the spires of the spiral-shaped planar portion 8 . The sheet of insulating material can have, for example, a rectangular shape, similar to that of the antenna 9 to be obtained, and the remaining area of the greater surface of the sheet, outside the area occupied by the turns, can also be partially, preferably completely, covered in a uniform and continuous layer of electrically conductive material, so as to form at least one electrically conductive (polygonal) portion defining the solid planar conductive portion. To this end, for example, the sheet of insulating material can be advantageously composed of a thin sheet of easily flexible/bendable insulating material (similar to an insulation sheet) . For example, the application of paint containing a conductive material on the flexible insulating sheet can be provided, for example via a silk-screen printing, so as to create the conductive surface layer forming the aforementioned spiral- shaped planar portion 8 and a conductive surface layer forming the aforementioned solid planar conductive portion electrically connected to the spiral-shaped planar portion 8 . As an alternative to depositing a layer of conductive material on the surface of the flexible insulating sheet of the planar antenna 7, provision can be made to use a metallic film shaped on the basis of the pattern/geometry of the planar antenna 9 to be obtained. For example, the metallic film could be shaped so as to have the aforementioned spiral-shaped portion 8 and the "solid" planar conductive portion, and be consequently permanently coupled/fixed to the flexible sheet (for example, by gluing) .

In the preferred embodiment shown in the accompanying figures, the solid planar conductive portion made of an electrically conductive material is electrically connected to an end/terminal of a turn of the spiral-shaped planar portion 8 . Preferably, the solid portion made of an electrically conductive material of the planar antenna 9 is defined by the portion of planar antenna 9 that surrounds the preferably outer turn of the spiral-shaped planar portion 8 and is electrically connected to one end of the outer turn. The spiral-shaped planar portion 8 can be structured in such a way that the turns have an approximately constant given width. Nevertheless, it is understood that the present invention is not limited to the use of turns of constant width, but can provide for other alternative embodiments. For example, the spiral-shaped planar portion 8 could be structured in such a way that the turns have a width that progressively decreases along its length between the two end turns. For example, the width of the turns could progressively decrease from the outer turn until reaching the innermost turn is reached, or vice versa.

According to a further embodiment, it is contemplated that at least one spire has a width greater than the other spires and that this width is sized so as to also form the capacitive component on the spiral-shaped planar portion 8 necessary for resonance. In fact, the applicant has found that in addition to the inductive component, it is also possible to obtain a capacitive component in the spiral-shaped planar portion 8 by opportunely widening at least one turn, conveniently the outermost turn. The widening of the turn actually enables the solid conductive portion to be obtained directly on the spiral-shaped planar portion. In this case, the turns of smaller width of the spiral-shaped planar portion 8 form the inductive component, and the turn(s) having a greater width form the capacitive component that cooperates with the inductive component to make the planar antenna resonate in the predetermined frequency band. It is understood that the smaller and greater widths of the turns can be sized on the basis of the required frequency band.

The applicant has found that the use of the planar antenna 9 with a spiral-shaped portion 8 made as described above is extremely advantageous, as it enables confining the bulk of the inductive-capacitive antenna circuit to a space delimited by the upper part of the half-shell 3 and therefore completely frees the central space beneath.

The applicant has also found that the positioning of the planar antenna 9 in the upper part of the half-shell 3 above the rear part of the antenna base 4 enables maximizing both the gain and quality of the antenna signal. In this regard, Figure 27 shows a graph, obtained through laboratory tests carried out by the applicant, which shows the average antenna signal gain obtained by the above-described planar antenna 9. It is also opportune to specify that, on the one hand, the gain and quality of the antenna signal are substantially proportional to the distance between the planar antenna 9 and the conductive base 4b, while on the other hand, the maximum height not to be exceeded by the half-shell 3 is restricted to 70 mm. In this regard, the applicant has found that the embodiment of the planar antenna 9 provided with the above- described spiral-shaped planar portion has two technical effects: a first technical effect is represented by the fact that due to its geometry, the planar antenna 9 can be placed at the maximum useful distance from the conductive base 4b beneath, with all of the above-described advantages; a second technical effect is represented by the fact that due to the integration of the spiral-shaped planar portion 8 defining the inductive component necessary for resonance, the planar antenna 9 significantly increases the free space available beneath, usefully allowing for the installation of other electronic components in the antenna device, such as other antennas for example. In fact, thanks to the presence of the spiral-shaped planar portion 8, the planar antenna 9 forms a single planar element that contains both an inductive component and a capacitive component. This integration and, in particular, the spiral-shaped geometry of the portion of the above-described planar antenna 9, also enables simplifying the installation of the antenna unit 7 in the antenna device 1 and achieving both a reduction in costs and optimization of the internal spaces. In fact, the integration of the spiral-shaped planar portion 8 in the body of the planar antenna 9 enables overcoming both the technical problem of having to install additional inductive electronic components, for example the vertical cylindrical wire coil and connecting it to the processing device 6, and the technical problem of having to use and install a frame to support the wire coil.

In the preferred embodiment shown in Figures 5-9, the spiral- shaped planar portion 8 can be arranged laterally with respect to a longitudinal centre plane Ml (vertical plane of symmetry) of the antenna device 1. In other words, the spiral-shaped planar portion 8 can be conveniently decentred in the planar antenna 9 in such a way that its axis B lies at a given non^¬ zero distance from the longitudinal centre plane Ml. As visible in the example shown in Figure 8, the centre plane Ml geometrically divides the planar antenna 9 into two opposite lateral semi-portions, while the spiral-shaped planar portion 8 is conveniently arranged on one of the two lateral surface semi-portions of the planar antenna 9.

In the preferred embodiment shown in Figures 5-10, the turns of the spiral-shaped planar portion 8 have about a trapezoidal shape. Conveniently, the smaller bases of the trapezoidal spires can face towards the centre plane Ml. Nevertheless, it is understood that the present invention is not limited to a spiral-shaped planar portion 8 with trapezoidal turns, but can provide for turns having any shape, such as a circular or elliptical shape, or a polygonal shape, for example, rectangular, triangular, rhomboidal or similar. For example, in an alternative embodiment shown in Figures 10-16, the spiral-shaped planar portion 8 can comprise turns having about a rectangular shape. In an alternative embodiment shown, for example, in Figures 19-21, the spiral-shaped planar portion 8 can instead comprise turns having a roughly circular shape, preferably a roughly spiral shape, logarithmic for example. Preferably, the inner turn of the spiral-shaped planar portion 8 can delimit (surround) a central through aperture on the planar antenna 9, the aperture being rectangular or circular according to the shape of the turns. It is understood that the present invention is not limited to a spiral-shaped planar portion 8 positioned laterally to the centre plane Ml, as shown in the embodiments in Figures 5-13, but can provide for any other positioning of the spiral-shaped planar portion 8 in the planar antenna 9.

For example, in a possible alternative embodiment shown in Figures 14-21, the spiral-shaped planar portion 8 is arranged in a central position of the planar antenna 9. The turns of the spiral-shaped planar portion 8 can thus be arranged in such a way that axis B lies approximately on the centre plane Ml .

In the embodiment shown in the accompanying figures, the planar antenna 9 has a roughly rectangular rear portion 9a that extends substantially beneath the rear portion 3b of the half-shell 3, and a substantially tapered front portion 9b that extends at least partially inside the front portion 3a of the half-shell 3 so as to face the latter (Figure 8) . In the embodiment shown in the accompanying figures, the spiral- shaped planar portion 8 is conveniently arranged in the rear portion 9a of the planar antenna 9. Laboratory tests carried out by the applicant have demonstrated that the positioning of the spiral-shaped planar portion 8 inside the antenna housing in the portion most distant from the antenna base 4, for example above the latter in the rear portion 9a, provides the best performance, both in terms of gain and in in terms of quality/strength of the antenna signal.

In the embodiment shown in the accompanying figures, the antenna device 1 can also comprise a support frame 10 made of an insulating material that is permanently arranged resting preferably on one or more sides of the outer perimeter portion of the antenna base 4. The support frame 10 is structured to support the planar antenna 9 at a given distance from the antenna base 4. Conveniently, the support frame 10 can be structured to keep the planar antenna 9 immediately abutting against the upper inner surface of the half-shell 3, preferably of the rear portion 3b.

In the embodiment shown in the accompanying figures, the support frame 10 comprises a plate-like body 11, on the top surface of which the planar antenna 9 is permanently fixed. Conveniently, at least the top surface of the plate-like body 11 can have a semicircular shape, approximately complementary to the bottom surface of the planar antenna 9, such that the latter can be arranged in one or more support positions on the plate-like body 11. For example, the plate-like body 11 could comprise a semicircular sheet of insulating material, preferably rigid, for example a plastic material. The plate^¬ like body 11 could be conveniently concave facing the antenna base 4. In addition, through apertures (not shown) could also be conveniently provided on the plate-like body 11.

In the preferred embodiment shown in the accompanying figures, the support frame 10 further comprises a series of lateral spacer brackets or rods 12. Preferably, each lateral spacer rod 12 extends approximately orthogonally to the antenna base 4 and has a top end permanently connected to the plate-like body 11, preferably on one side of the latter. Preferably, the bottom end of the spacer rod 12 is instead permanently connected to the antenna base 4 beneath, preferably by a lateral portion, for example, at one side. It is understood that the present invention is not limited to the use of the support frame 10, but can provide for other systems/mechanisms structured to support the planar antenna 9 above the antenna base 4, so as to keep it at a certain distance from the latter. For example, in an alternative embodiment (not shown) in which the antenna device 1 does not have the support frame 10, the planar antenna 9 can be permanently fixed onto the inner surface of the half-shell 3 by fastening means, for example screws, clips, gluing or similar means.

In a further alternative embodiment (not shown, and in which the antenna device 1 does not have the above-described support frame 10), the planar antenna 9 can be arranged resting on the antenna base 4 by means of a vertical printed circuit board (PCB) made of a rigid insulating material. The printed circuit board can be rectangular and have a bottom end abutting against the antenna base 4 and the upper end supporting the planar antenna 9. The printed circuit board can thus act as a support structure for the upper planar antenna 9. The printed circuit board can conveniently comprise at least one circuit branch that can act as an electrical connection between the upper planar antenna 9 and the antenna signal reception and/or supply terminal 6a of the processing device 6 beneath. Furthermore, the printed circuit board can be arranged on one side of the antenna base 4, parallel to the latter, so as not to occupy the central space of the antenna housing, or, alternatively, on the centre plane Ml. The vertical-support printed circuit board can also conveniently contain/integrate the amplification circuit of the processing device 6.

In a further alternative embodiment (not shown, and in which the antenna device 1 does not have the above-described support frame 10), the planar antenna 9 can be self-supporting. The planar antenna 9 can be provided at the bottom with a rigid, vertical, electrically conductive element arranged with a bottom end resting on the antenna base 4. The vertical conductive element can be constituted, for example, by a metal strap or a wire made of an electrically conductive material, opportunely sized to permanently support the planar antenna 9 and also to conveniently act as an electrical connection between the latter and the terminal 6a of the processing device 6 beneath. In the preferred embodiment shown in the accompanying figures, the electrical connection between the planar antenna 9 and the processing device 6 for reception or transmission of the antenna signal is achieved using a wire 13 made of an electrically conductive material. Conveniently, the wire 13 has one end connected to the planar antenna 9, preferably to a terminal of a turn and the other end connected to the terminal 6a of the processing device 6.

In the preferred embodiment shown in the accompanying figures, the wire 13 extends vertically, passing through the internal space of the half-shell 3, preferably, but not necessarily, the central space. Nevertheless, it is understood that the present invention is not limited to a wire 13 that extends centrally in the half-shell 3, as shown in Figure 5, but can provide for any other positioning of said wire. For example, according to an alternative embodiment, the wire 13 can extend vertically downwards from the top, remaining close to or, alternatively, in contact with the lateral inner surface of the half-shell 3 so as not to occupy the space beneath the planar antenna 9. For example, the wire could run remaining conveniently close to the inner surface of the rear wall of the half-shell 3, opposite to the tip of the latter. For example, the applicant has found that the feed wire 13 for the antenna signal can be conveniently sized to have a diameter approximately ranging between 0.3 mm and approximately 0.8 mm. It is understood that the connection wire 13 between the turn of the spiral-shaped planar portion 8 and the input terminal 6a of the processing device 6 can run along any path and have any length. In other words, it is possible to size and position the wire 13 so as to reduce or completely eliminate the occupation of space beneath the planar antenna 9.

Conveniently, according to the present invention, the electrical connection between the terminal 6a of the processing device 6 and a terminal of a turn of the spiral- shaped planar portion 8 is constituted by an electrical branch free of inductive electronic components, in particular without any wire coil. The electrical branch is preferably constituted by the wire 13. In the preferred embodiment shown in the accompanying figures, the spiral-shaped planar portion 8 has the free end of the outer turn connected to the solid planar conductive portion and the free end of the inner turn connected to the processing device 6 solely by the wire 13. In the preferred embodiment shown in the accompanying figures, the antenna signal exchanged between the planar antenna 9 and the processing device 6 via the wire 13 is an AM/FM antenna signal. Incidentally, the planar antenna 9 made as described above, i.e. equipped with the spiral-shaped planar portion 8, is designed to operate as a resonating antenna in the FM radio frequency band and as a non-resonating antenna in the AM radio frequency band.

It is understood that the present invention is not limited to a planar antenna 9 designed to operate in the FM/AM radio band, but can be structured/sized/configured to operate in another frequency band. For example, in an alternative embodiment (not shown) , the planar antenna 9 operates as a resonating antenna in the DAB radio frequency band. It is also understood that the present invention is not limited to an antenna device 1 equipped with a single planar antenna 9 with a spiral-shaped planar portion 8, which as described above can be made according to the various embodiments shown in Figures 5 to 21, but can provide for an antenna device 1 equipped with two or more planar antennas 9 structured to operate in respective frequency bands.

As shown in Figures 23 to 26, the two planar antennas 9 can be arranged preferably side by side, one after the other along the axis A. For example, in an alternative embodiment shown in Figures 23 and 24, the antenna device 1 comprises two planar antennas 9 that are equipped with corresponding spiral-shaped planar portions 8 and operate in the AM/FM frequency band and in the DAB frequency band, respectively. A planar antenna 9 operating in the AM/FM radio frequency band can be conveniently structured so as to be arranged approximately in the rear portion 3b of the half-shell 3 and be positioned above, and at the maximum distance from, the antenna base 4. The other planar antenna 9 operating in the DAB radio frequency band can be conveniently structured so as to be arranged in the front portion 3a of the half-shell 3. The two planar antennas 9 are distinct and separate from one another, and are provided with respective, preferably lateral, spiral- shaped planar portions 8. According to the embodiment shown in Figures 23 and 24, the antenna device 1 is also conveniently equipped with a pair of electrical connections 13 made of an electrically conductive material and designed to electrically connect the two spiral-shaped planar portions 8 to the two respective terminals 6a of the processing device 6. According to the embodiment shown in Figures 23 and 24, the two electrical connections 13 can usefully comprise vertical metal straps sized to be arranged resting on the antenna base 4 and supporting the planar antennas 9 above them.

It is understood that the present invention is not limited to an antenna device 1 equipped with a pair of planar antennas 9 provided with respective lateral spiral-shaped planar portions 8, but that each planar antenna 9 can be made according to any of the above-described embodiments and shown in the accompanying figures (5 to 22) . According to an embodiment shown in Figures 25-26, the antenna device 1 can also comprise a support frame 10 structured to support the two planar antennas 9. The support frame 10 can be made of an insulating material and, close to each spiral- shaped planar portion 8, can comprise projections 21, each of which is inserted/arranged in the through apertures between the adjacent turns of the spiral-shaped planar portion 8 to keep them set apart from each other. The applicant has found that the projections 21 enable conveniently keeping the turns in a reciprocal stable predetermined position so as not to degrade antenna performance in the case of mechanical stress on the antenna. Preferably, the projections 21 can be defined by cylindrical elements conveniently arranged on the support frame 10 so as to be inserted in the through apertures between the turns according to a crosswise layout.

The applicant has found that by keeping an opportune axial distance (along axis A) between the two planar antennas 9, for example a distance of approximately 5-10 mm, it is possible to obtain a first planar antenna 9 conveniently resonating in the FM radio frequency band and the other planar antenna 9 conveniently resonating in the DAB radio frequency band. In this embodiment, the AM frequency band can instead be obtained via either of the two planar antennas 9 as no resonance is required/entailed be the latter. In this regard, laboratory tests carried out by the applicant have also demonstrated that a reciprocal aligned positioning of the two planar antennas 9 causes an increase in the metallic area affected by the AM frequency band, which conveniently causes an increase in sensitivity of the antenna device. Preferably, the planar antenna 9 operating in the DAB frequency band can be conveniently sized in such a way that its longitudinal length (measured along axis A) is less than the (longitudinal) length of the other planar antenna 9 operating in the FM frequency band . In the preferred embodiment shown in the accompanying figures, in which the planar antenna 9 operates in the AM/FM radio frequency band, the antenna device 1 can also comprise a series of first additional antennas 15, which are conveniently arranged close to the antenna base 4 beneath the planar antenna 9. For example, referring to Figure 10, the first additional antennas 15 can optionally comprise one or more of the following antennas: a telephone antenna (TEL - GSM, UMTS, LTE) and/or a V2V antenna (Vehicle To Vehicle) or V2X antenna (Vehicle To Everything), a Bluetooth antenna and/or a WIFI antenna, and a GNSS antenna (GPS, GLONASS, GALILEO etc.) and/or a SDARS antenna (Satellite Digital Audio Radio Service) .

In an alternative embodiment, the device can also comprise second additional antennas 16, which can be conveniently arranged in the front part of the antenna base 4 beneath the front portion 3a of the half-shell 3. The second additional antennas 16 can optionally comprise one or more of the following antennas: GNSS antennas (GPS, GLONASS, GALILEO, etc..) or SDARS antennas (Satellite Digital Audio Radio Service) .

In the preferred embodiment shown in Figures 5 to 19, the antenna device 1 can also comprise a DAB antenna 18 operating in the DAB frequency band separate and distinct from the planar antenna 9. For example, the DAB antenna 18 could be arranged in an intermediate portion of the antenna base 4, i.e. in the space between the first additional antennas 15 and the second additional antennas 16. In the example shown, the DAB antenna 18 conveniently comprises a meander antenna. In the example shown, the DAB antenna 18 is provided with a vertical, rigid, rectangular, dielectric support on the opposite walls and on which the radiating zigzag tracks of conductive material are printed. The tracks of the DAB antenna 18 can be conveniently adjacent to the planar antenna 9 in order to exploit the capacitive contribution of the latter and thus achieve a wider DAB frequency band.

It is understood that the number, thickness and distance between the turns of the spiral-shaped planar portion 8, as well as their shape, can be varied/established at least on the basis of the frequency band of the antenna to be made.

In this regard, it should be specified that the planar antenna 9 is advantageously tuneable in the desired frequency band. Laboratory tests carried out by the applicant have demonstrated that a planar antenna constituted solely by a rectangular metal sheet (i.e. constituted solely by the "solid" concave planar conductive portion) constitutes a short monopole, less than the wavelength (approximately fiftieth of the wavelength) and has a prevalently capacitive behaviour. In the light of this, in order to obtain an inductive-capacitive circuit in a single body capable of resonating at a preferred frequency, the applicant has also implemented the aforementioned spiral-shaped planar portion 8, which constitutes a prevalently inductive component, on the planar antenna. It is understood that the resonance frequencies of the planar antenna 9 can be fixed/variable on the basis of several factors, such as: number of turns of the spiral-shaped planar portion 8, and/or width of the turns, and/or distance separating the turns. In addition to determining the resonance frequency, these parameters also determine the antenna' s bandwidth, together with the portion of area projected by the radiant element group onto the conductive base beneath, to which the amplifier circuit is fixed. In order to preserve the aforementioned projected area, it is possible, for example, to increase the thickness of the flattened tracks that define the turns of the spiral-shaped planar portion 8 and, at the same time, reduce the distance between them, in this way ensuring the same performance that would be achieved with a "solid" planar antenna (without through apertures) .

According to a preferred embodiment schematically shown in Figure 22, the planar antenna 9 can be shaped so as to comprise one or more rear planar extensions 23 with, for example, a roughly triangular or trapezoidal shape, which protrude in a cantilevered fashion from the rear portion 9a. Conveniently, the rear extensions 23 can be arranged on opposite sides with respect to the centre plane Ml. Conveniently, the rear extensions 23 can be bent towards the antenna base 4 so as to lie on a plane approximately orthogonal to the latter. The applicant has found that the preferably bent rear extensions 23 increase the sensitivity of the antenna device 1, in terms of both peak and bandwidth.

According to a preferred embodiment schematically shown in Figure 22, the planar antenna 9 can be shaped so as to have a front extension 24 shaped on the basis of the geometry of the front portion 3a of the half-shell 3 such that it can be contained within the latter. The front extension can protrude in a cantilevered fashion from the central end of the front portion 9 along axis A. The front extension 24 can also be slightly bent downwards with respect to the front portion 9a so as to approximately follow the upper centre edge of the front portion 3a. The applicant has found that the front extension 24 increases the receptive surface for the radio signal and thus causes a significant increase in antenna gain.

After having being revealed in the foregoing, the many advantages of the above-described antenna device will not be further described other than specifying that the antenna device 1 enables significantly increasing the internal space available in the antenna housing whilst maintaining performance in signal reception or transmission.

Finally, it is clear that modifications and variants can be made regarding the antenna device described and illustrated above without departing from the scope of the present invention defined by the appended claims.

Claims

1. An antenna device (1) characterized in that it comprises:

- an upper half-shell (3),

- a lower antenna base (4) , which is coupled to said half- shell (3) to create an antenna housing,

- electronic means (6), which are arranged inside said antenna housing and are designed to receive/supply an antenna signal,

- at least one antenna unit (7) provided with a planar antenna (9) that is arranged inside said antenna housing to receive/supply said antenna signal from/to said electronic means (6) and comprises a spiral-shaped planar portion (8) made of an electrically conductive material.

2. The antenna device according to claim 1, wherein said spiral-shaped planar portion (8) comprises a plurality of turns which are laid out approximately concentrically on a same surface approximately orthogonal to a first axis (B) and extend on said surface so as to occupy a progressively increasing area.

3. The antenna device according to claims 1 or 2, wherein said spiral-shaped planar portion (8) is shaped so as to form, in said planar antenna (9), an inductive-capacitive component designed to make the planar antenna (9) resonate in at least one predetermined frequency band.

4. The antenna device according to any of the preceding claims, wherein said planar antenna (9) further comprises a solid planar portion made of an electrically conductive material that forms a capacitive component; said solid planar portion and said spiral-shaped planar portion (8) being reciprocally connected to each other so as form an inductive- capacitive component designed to make said planar antenna (9) resonate in one or more frequencies ranging between a predetermined frequency band.

5. The antenna device according to any of the preceding claims, wherein said spiral-shaped planar portion (8) has an antenna terminal connected directly to a signal terminal (6a) of said electronic means (6) by a conductive connection line (13); the electrical connection between the antenna terminal and the signal terminal (6a) being without inductive electronic components.

6. The antenna device according to claim 5, wherein said antenna terminal corresponds to an end of a spire of said spiral-shaped planar portion.

7. The antenna device according to claims 5 or 6, wherein said conductive connection line (13) comprises a wire made of an electrically conductive material that extends in said antenna housing approximately beneath said planar antenna (9) .

8. The antenna device according to any of the preceding claims, wherein said planar antenna (9) is arranged in said antenna housing so as be approximately adjacent to the upper internal surface of said half-shell (3) at a predetermined distance from said antenna base (4) .

9. The antenna device according to any of the preceding claims, wherein said spiral-shaped planar portion (8) is arranged in a lateral portion of said planar antenna (9) .

10. The antenna device according to any of the preceding claims, wherein the spires of said spiral-shaped planar portion (8) have about a polygonal shape, or about a circular shape, or about a elliptical shape, or about a spiral shape.

11. The antenna device according to any of the preceding claims, wherein said planar antenna (9) comprises a sheet made of an electrically conductive material; said spiral-shaped planar portion (8) being made on said sheet so as to form a single body therewith.

12. The antenna device according to any of the preceding claims, comprising fastening means structured to permanently couple said planar antenna (9) onto the inner surface of said half-shell (3) .

13. The antenna device according to any of claims 1 to 11, comprising support means (10) made of an insulating material, which are connected at the bottom to said antenna base (4) and are structured so as to support, on their upper part, said planar antenna (9) in a position approximately adjacent to the upper inner surface of said half-shell (3) .

14. The antenna device according to claim 13, wherein said support means (10) comprise a support frame provided with a plate-like body (11) on the top surface of which said planar antenna (9) is rested, and one or more lateral spacer elements (12) that connect said plate-like body (11) to one or more sides of said antenna base (4) .

15. The antenna device according to any of the preceding claims, comprising two or more planar antennas (9) provided with respective spiral-shaped planar portions (8) operating in respective frequency bands.

16. The antenna device according to any of the preceding claims, wherein said planar antenna (9) is configured so as resonate in the FM frequency band or in the DAB frequency band, and is designed not to resonate in the AM frequency band .