Antenna for motor vehicles, and motor vehicle comprising such an antenna

Abstract

Antenna (100) for a motor vehicle, characterised by comprising at least: - a mounting base (1) suitable for connection to a mounting surface of said motor vehicle; - an electronic circuit (5) suitable to be placed on said mounting base (1); - a non-resonant radiating element (10) which is operatively connected to said electronic circuit (5) and is configured to simultaneously receive and transmit towards said electronic circuit (5), at least first signals and second signals emitted, from one or more devices external to the antenna (100), respectively in a first frequency band and in a second frequency band different from said first frequency band; and wherein said electronic circuit (5) is configured at least to selectively extract and process said first and second signals distinctly from each other.

Description

[0001] The present invention relates to an antenna for motor vehicles, and to a motor vehicle comprising such an antenna.

[0002] The antenna according to the invention is especially suitable for use in automobiles, for example mounted on the roof of a car, and will be described herein with reference to such use without limiting its possible applications to other types of motor vehicles, such as buses, trucks, commercial vehicles, et cetera, and to mounting in other positions.

[0003] As is well known, antennas intended to be mounted on the roof or another external surface of a motor vehicle essentially comprise a functional part, consisting of a plurality of suitably configured and assembled components that are suitable for mounting and operating the antenna, and a cover or dome whose purpose is to contain the various functional components of the antenna and to ensure, where possible, that the vehicle retains its aerodynamic appearance and efficiency once the antenna has been installed.

[0004] For example, in the case of rear-mounted antennas, the cover usually has a so-called shark fin shape.

[0005] In the case of antennas mounted at the front of the roof, the cover may also take different shapes, but in any case it must have an overall height lower than antennas mounted at the rear and ensure a certain aerodynamic efficiency.

[0006] Normally, the functional part of the antennas used comprises a plurality of radiating elements that can transceive data and signals of different types according to various standards and related frequency ranges that have been introduced over the years.

[0007] Although the antennas currently on the market can perform the functions for which they are designed, there are some aspects that could be improved.

[0008] In particular, the presence of several radiating elements inevitably placed close to each other in the narrow space delimited by the cover leads to problems with the actual quality of the signals due to the possible coupling between the signals afferent to two or more radiating elements and interfering with each other.

[0009] To overcome these drawbacks, especially in the case of low-profile antennas, an additional element is used, typically a coil that is driven by an electronic circuit to make it function as a resonant antenna.

[0010] This solution, although effective from a functional point of view, implies the use of at least one additional element and therefore has an impact on costs as well as installation difficulties due to the reduced available space.

[0011] Therefore, the aim of the present invention is to provide an antenna for motor vehicles that can at least partially mitigate these problems.

[0012] This purpose and others that may result from the following description are achieved by an antenna for a motor vehicle whose characteristics are defined in claim 1.

[0013] This purpose is also achieved by a motor vehicle according to claim 10.

[0014] Particular embodiments are the subject of dependent claims, the content of which is to be understood as an integral part of this description.

[0015] Further characteristics and advantages of the invention will appear from the following detailed description, carried out by way of non-limiting example only, with reference to the accompanying drawings, in which: Figure 1 is a view schematically illustrating a possible embodiment of an antenna according to the invention; Figure 2 is a view schematically illustrating another possible embodiment of an antenna according to the invention; Figure 3 is a view schematically illustrating another possible embodiment of an antenna according to the invention; Figure 4 is a block diagram schematically illustrating some components of an antenna according to the invention.

[0016] It should be noted that in the following detailed description, identical or similar components, from a structural and / or functional point of view, may have the same or different reference numbers, regardless of whether they are shown in different embodiments of the present invention or in separate parts.

[0017] It should also be noted that, in order to clearly and concisely describe the present invention, the drawings may not be to scale and some features of the description may be shown in a somewhat schematic form.

[0018] Furthermore, when the term "adapted" or "configured" or "shaped" or a similar term is used herein, referring to any component as a whole, or to any part of a component or to a combination of components, it shall be understood to mean and include correspondingly the structure and / or configuration and / or shape and / or positioning.

[0019] In particular, when these terms refer to electronic hardware or software means, they are to be understood as including electronic circuits or parts of electronic circuits, as well as software / firmware, such as algorithms, routines and programs in general, running and / or resident in any storage medium.

[0020] In addition, when the term "substantial" or "substantially" is used herein, it is to be understood as referring to unavoidable construction / functional tolerances, or as encompassing a current variation of plus or minus 5% with respect to what is indicated as the reference value, direction or position, and when the terms "transverse" or "transversely" are used herein, they are to be understood as encompassing a direction not parallel to the reference part(s) / axis(s) to which they refer, and perpendicularity is to be considered a specific case of transverse direction.

[0021] Finally, in the following description and claims, the ordinal numerals first, second, et cetera, will be used for the sake of illustrative clarity and in no way should they be understood as limiting for any reason whatsoever, nor that the order should be exactly that in the sequence described with reference to the realisation examples described.

[0022] Figures 1 to 3 illustrate possible embodiments of an antenna according to the invention, indicated globally by the reference numeral 100, wherein the exemplary embodiments in Figures 1 and 2 illustrate an antenna 100 particularly suitable for mounting on the front part of the roof of a motor vehicle, while the exemplary embodiment in Figure 3 illustrates an antenna 100 particularly suitable for mounting on the rear part of the roof of a motor vehicle.

[0023] The antenna 100 according to the invention comprises at least: a mounting base 1 which, when antenna 100 is installed, is intended to be coupled to a mounting surface of a motor vehicle, e.g. on its roof; an electronic circuit 5 capable of being arranged on said mounting base 1 either directly or with one or more other components interposed between them; at least one non-resonant radiating element, indicated by the overall reference number 10, which is operatively connected to the electronic circuit 5 and is configured to simultaneously receive and transmit towards the electronic circuit 5 itself, at least first signals and second signals emitted, from one or more devices external to the antenna 100, in a first frequency band and in a second frequency band different from the first frequency band, respectively.

[0024] The non-resonant radiating element 10 has a high reactive component.

[0025] In particular, as known to those skilled in the art, a resonant radiating element is a radiating element whose input impedance has a reactive component that crosses zero at the center of the relevant transceiver frequency band, while a non-resonant one is a radiating element whose input impedance has a reactive component that is not zero and has a modulus substantially greater than the resistive component, e.g. about 5-6 times greater.

[0026] Usefully, the electronic circuit 5 is configured at least to selectively extract and process said first and second signals separately.

[0027] In this way, compared to known solutions, a single, non-resonant radiating element is used for both frequency bands, with the electronic circuit selectively extracting and appropriately processing the respective signals, without using any additional components, such as a resonant coil, for example, with consequent benefits in terms of cost and ease of implementation.

[0028] For example, the second frequency band is higher than the first frequency band.

[0029] In a possible embodiment, the non-resonant radiating element 10 is configured to simultaneously receive and transmit to said electronic circuit 5 first signals emitted in the FM (Frequency Modulation) frequency band and second signals emitted in the DAB (Digital Audio Broadcasting) frequency band.

[0030] In one possible embodiment, the electronic circuit 5 comprises or consists of at least one printed circuit board arranged on said mounting base 1, e.g. in a substantially horizontal position.

[0031] The mounting base 1 can have a suitable shape, e.g. when viewed in plan view from above, a quadrangular shape, e.g. rectangular or square, as illustrated in the exemplary embodiment of Figures 1 and 2, or another suitable shape, e.g. (when viewed in plan view from below or above) an iron shape, as illustrated in the example in Figure 3.

[0032] The mounting base 1 can be made in one or more pieces and in one or more materials suitably combined with each other.

[0033] For example, in the embodiments illustrated in Figures 1-3, the base 1 has a central part made of metal on which the electronic circuit 5 is placed and the remaining part of plastic material.

[0034] The antenna 100 further comprises a cover, schematically illustrated in Figure 1 as a dotted line and partially illustrated in Figure 2 and indicated therein by the reference number 2, which is suitable for coupling to the mounting base 1 so as to form a closed containment enclosure housing within it various antenna components, including the electronic circuit 5 and the radiating element 10.

[0035] The cover 2 is made of a suitable plastic material, for example, and can have any configuration suitable for the purpose.

[0036] In particular, in the case where the antenna 100 is to be mounted on the front part of the roof of a motor vehicle, the cover 2 is configured in such a way that, once the antenna 100 is mounted on the front part of the roof of a motor vehicle, the cover 2 reaches a maximum total height (indicated for simplicity of description only in figure 1 by the letter H), measured from the upper surface of the roof, schematically indicated in figure 1 by the reference number 50, of less than 40 mm.

[0037] In the event that the antenna 100 is to be mounted on the rear of the roof of a car, the cover 2 can reach a higher height and can have a classic shape of a shark fin.

[0038] The mounting of the mounting base 1 on the roof or on a suitable mounting surface of a motor vehicle and the connection of the cover 2 to the same mounting base 1, are carried out in a manner known or readily implementable by a person skilled in the art, and in any event not relevant to the present invention, and therefore not described herein in detail.

[0039] In a possible embodiment, the electronic circuit 5 comprises a first filter stage, indicated in figure 4 by reference number 20, a second filter stage, indicated in figure 4 by reference number 22, and an active stage, indicated in figure 4 by reference number 21, which is interposed between the first and second filter stages 20 and 22.

[0040] In particular, the first filtering stage 20 includes at least: a first filter 20A which is configured to extract said first signals emitted in the first frequency band and let through toward and substantially adapt them to the input impedance of the active stage 21, while rejecting the second signals emitted in the second frequency band; and a second filter 20B which is configured to extract said second signals emitted in the second frequency band and let thorugh towards and substantially adapt them to the impedance of the active stage 21, while rejecting said first signals emitted in the first frequency band.

[0041] In practice, the two filters 20A and 20B are selective filters of the frequency bands of interest, e.g. FM or DAB, and are adaptive in that they are configured to compensate for the reactive part of the radiating element 10 in the band of interest (FM / DAB) by adapting it as much as possible to the complex conjugate of the input impedance of the active stage 21.

[0042] The complex conjugate is an input impedance value that has a resistive part substantially equal to the resistive part of the radiating element 10, and a reactive part that is of equal modulus but opposite sign to the reactive part of the radiating element 10.

[0043] Furthermore, these filters can also raise the remaining purely resistive value of the antenna impedance to better match the input value of the active stage 21, and are purely reactive, i.e. they do not introduce losses and optimise the performance of the stages from a noise point of view.

[0044] In one possible embodiment, the active stage 21 comprises at least a first plurality of active stages operatively connected to the first filter 20A and arranged in sequence with each other, and a second plurality of active stages connected to the second filter 20B and arranged in sequence with each other.

[0045] In particular, in the embodiment illustrated in figure 4, the active stage 21 comprises a first active stage 21A and a second active stage 21B which are operatively associated with the first filter 20A, and a third active stage 21C and a fourth active stage 21D which are operatively associated with the second filter 20B.

[0046] In particular, at least the first stage of the first and second plurality of active stages is optimised with regard to noise performance, while the following stage(s) of the first and second plurality of active stages is / are configured at least to optimise the dynamics performance so as to achieve an adequate compromise between the two requirements.

[0047] Clearly, the number of stages of the first and second plurality of active stages can be varied appropriately.

[0048] In a possible embodiment, the second filtering stage 22 comprises at least: a third filter 22A which is operatively connected to said first and second active stages 21A, 21B and is configured so as to allow said first signals to pass through, while rejecting said second signals and eliminating any undesired noise or harmonics that may be present in said first signals to be let through; a fourth filter 22B which is operatively connected to said third and fourth active stages 21C and 21D, and is configured to allow said second signals to pass through while rejecting said first signals and eliminating any undesired noise or harmonics that may be present in said second signals to be let through.

[0049] In practice, the third filter 22A and the fourth filter 22B are selective filters in such a way as to let the respective signals pass only in the band of interest (FM / DAB) and are configured to reject signals in the bands not of interest.

[0050] This makes it possible to reduce out-of-band noise and unwanted harmonics, e.g. upper harmonics or second-order intermodulation IM2.

[0051] In a possible embodiment, the electronic circuit 5 further comprises a combiner, schematically represented in figure 4 by reference number 25, which is configured to convey on a common coaxial cable, schematically represented in figure 4 by reference number 26, the first and second output signals from said third filter 22A and fourth filter 22B, respectively.

[0052] In this way, the combiner 25 allows the unification of signals (each in its own frequency band) on a single coaxial output cable 26, optimising overall implementation costs.

[0053] Usefully, in one possible embodiment, the non-resonant radiating element 10 is configured to also simultaneously receive and transmit to said electronic circuit 5 third signals emitted in a third frequency band, i.e. the frequency band related to GNSS satellite signals.

[0054] Conveniently, in one possible embodiment, the non-resonant radiating element 10 is made of a single body of sheet metal, e.g. tin-plated steel.

[0055] According to one possible embodiment, illustrated in Figures 1 and 2, the non-resonant radiating element 10 comprises at least one portion 12 with planar development which is arranged spaced from and substantially parallel to the printed circuit board which is part of or forms the electronic circuit 5.

[0056] The planar development portion 12 is operationally connected to the electronic circuit 5 via a connecting element along which the received signals are routed, and schematically indicated in Figures 1 and 2 by the reference number 11.

[0057] Conveniently, the connecting element 11 has an overall electrical length that is less than the operating wavelength for each frequency band, and particularly the band with the higher operating frequency (thus having shorter wavelength).

[0058] In particular, the connection element 11 has an overall electrical length equal to or less than 10% of the wavelength at the center of the upper frequency band between the first and second frequency bands, preferably equal to or less than 5%, more preferably equal to or less than 3%.

[0059] This may contribute or render the radiating element 10 non-resonant.

[0060] As known, the electrical length of an element may be defined as its physical length in relation to the working wavelength.

[0061] In the example illustrated, the connecting element 11 is formed by one section substantially straight.

[0062] In case it is formed by two or more sections, the electrical length has to be calculated by summing all lengths calculated along the centerline of each section.

[0063] For instance, in case of a curved section, the respective length can be calculated and summed up to the other sections once the curved section is considered straightened.

[0064] In the example illustrated, the second frequency band, e.g. the DAB frequency band, is the upper frequency band with respect to the lower first frequency band, e.g. the frequency band FM.

[0065] As illustrated in the implementation examples of Figures 1 and 2, the non-resonant radiating element 10 is mounted on a support structure, indicated by the overall reference number 14, which is connected to the mounting base 1 and is configured so as to position the planar development portion 12 spaced from and substantially parallel to the printed circuit board.

[0066] In the embodiment shown in Figure 1, the planar development portion 12 has, when viewed in plan view, a substantially quadrangular, in particular rectangular, shape, with walls or sections of side walls 13 extending transversally from opposite sides of the planar development portion 12 towards the printed circuit board 12.

[0067] In the embodiment of Figure 2, the planar development portion 12 presents, when viewed in plan view, a substantially quadrangular shape, in particular almost square, and includes a pair of opposite corners 16 and 17, which are cut at an angle of approximately 45° to their adjacent sides, 16A and 16B, 17A and 17B respectively.

[0068] This allows the radiating element to also receive third signals emitted in the GNSS frequency band.

[0069] In this configuration, the radiating element may possibly be realised from the planar development portion 12 alone.

[0070] In a possible embodiment, the antenna 100 may comprise a patch or patch-like radiating element, schematically represented in Figure 2 by the reference number 4, which is arranged resting on the printed circuit board constituting or being part of the electronic circuit 5.

[0071] Preferably, as schematically illustrated in figure 2, the patch 4 is placed on the printed circuit board 5 substantially at the central area of the planar development portion 12.

[0072] In this way, an overall 'stacked patch' radiating element structure made up of two layers is realised, with a first layer formed by radiating patch 4 and a second layer formed by the radiating element 10, which also receives the third GNSS signals.

[0073] In particular, in order to receive satellite signals in the third GNSS frequency band, in this configuration, it is possible to use a radiating element 10 formed by the planar development portion 12 alone, having, for example, a quadrangular shape and not necessarily provided with the oblique cuts 16 and 17.

[0074] Alternatively, reception of GNSS satellite signals can be achieved by a classical GPS receiver, illustrated in Figure 1 by reference number 6.

[0075] In the embodiment illustrated in Figure 3, the non-resonant radiating element 10 comprises a contoured body which is configured to fill as much space as possible between the cover 40 and the printed circuit board which forms or is included in the electronic circuit 5.

[0076] In particular, in this embodiment, the non-resonant radiating element 10 comprises a lower portion with planar development 120 which is arranged directly on and substantially perpendicular to the printed circuit board which is part of or forms the electronic circuit 5.

[0077] In the example illustrated, the planar lower portion 120 comprises a solid upper portion 121 and three engagement teeth 122 inserted in slots provided on the electronic circuit 5.

[0078] The contoured body of the non-resonant radiating element 10 also includes a second, or upper portion 140, which is configured to realize a capacitive cap.

[0079] The capacitive cap cooperates with the first planar development portion 120 and allows for the optimisation of the overall emissive capacity of the non-resonant radiating element 10.

[0080] In particular, according to a possible embodiment, the second portion 140 comprises, with reference to a frontal view of antenna 100 (i.e. from the pointed front edge of the mounting base): a first section 141 that extends transversally from the upper end of the first portion 120; a first arm 142 which rises away from the first section 141 moving away from the mounting base 1; a second section 143 which extends transversally from the first arm 142; and a second arm 144 which extends from the second section 143 towards the mounting base 1, said first and second arms 142, 144 extending from the second section 143 from opposite sides of the first portion 120 diverging from each other.

[0081] With reference to a side view of the antenna 100, the second section 143 is inclined downwards proceeding from the rear edge towards the pointed front edge of the mounting base 1.

[0082] Similar to the embodiment of Figure 1, the reception of GNSS satellite signals can also be achieved in this embodiment by a classical GPS receiver 6.

[0083] In practice, it has been proven that the antenna 100 according to the invention adequately fulfils its intended purpose as it uses a single non-resonant radiating element suitably driven by an appropriate electronic circuit for the simultaneous reception of signals in different frequency bands.

[0084] In this way, compared to known antennas, there is a reduced number of components, optimising the space occupied and reducing implementation costs.

[0085] Furthermore, the antenna 100 according to the invention has a structure that makes it suitable for use in new motor vehicles as well as for replacing antennas already installed on motor vehicles in use and, thanks to its reduced height, it can be mounted, for example, on the roof of a motor vehicle, either at the front or at the rear. In the latter case, as the regulations are less stringent, the cover can be made, for example, in the shape of a shark fin, if desired with an overall height H even higher than the previously mentioned dimension.

[0086] Of course, without prejudice to the principle of the invention, the forms of implementation and details of realisation may be widely varied with respect to what has been described and illustrated purely by way of non-limiting examples, without thereby departing from the scope of protection of the present invention as defined by the appended claims, including any possible combination, even partial, of the embodiments described above.

[0087] For example, in all described embodiments, the non-resonant radiating element 10 may also receive signals in the AM frequency band. In this case, the AM signals can be processed by the electronic circuit 5 in parallel with the signals in the other frequency bands described above, e.g. by using low-pass filtering at the input and then amplifying the signals in parallel with the others, and then feeding the AM signals also into the combiner 25.

Claims

1. Antenna (100) for a motor vehicle, characterized in that it comprises at least: - a mounting base (1) configured to be connected to a mounting surface of said motor vehicle; - an electronic circuit (5) suitable for being arranged on said mounting base (1); - a non-resonant radiating element (10) which is operatively connected to said electronic circuit (5) and is configured to simultaneously receive and transmit to said electronic circuit (5), at least first signals and second signals emitted, from one or more devices external to the antenna (100), in a first frequency band and in a second frequency band different from said first frequency band, respectively; and wherein said electronic circuit (5) is configured at least to selectively extract and process said first and second signals distinctly from each other.

2. Antenna (100) according to claim 1, wherein said electronic circuit (5) comprises a first filter stage (20) and a second filter stage (22), and an active stage (21) interposed between said first and second filter stages (20, 22); wherein said first filter stage (20) comprises at least: - a first filter (20A) configured to extract said first signals emitted in said first frequency band and let through toward and substantially adapt them with the input impedance of said active stage (21) while rejecting said second signals emitted in said second frequency band, and a second filter (20B) configured to extract said second signals emitted in said second frequency band and let through toward and substantially adapt them with the input impedance of said active stage (21) while rejecting said first signals emitted in said first frequency band; wherein said active stage (21) comprises at least a first active stage (21A) and a second active stage (21B) operatively associated with said first filter (20A), and a third active stage (21C) and a fourth active stage (21D) operatively associated with said second filter (20B); and wherein, said second filter stage (22) comprises at least: - a third filter (22A) which is operatively connected to said first and second active stages (21A, 21B) and is configured to let through said first signals while rejecting said second signals and eliminating unwanted noise or harmonics that may be present in said first signals to be let through; - a fourth filter (22B) that is operatively connected to said third and fourth active stages (21C, 21D) and is configured to let through said second signals while rejecting said first signals and eliminating noise or unwanted harmonics possibly present in said second signals to be let through.

3. Antenna (100) according to claim 2, wherein said electronic circuit (5) further comprises a combiner (25) configured to convey on a common coaxial cable (26) at least the first and second signals output from said third filter (22A) and fourth filter (22B), respectively.

4. Antenna (100) according to one or more of the preceding claims, wherein said non-resonant radiating element (10) is configured to simultaneously receive and transmit to said electronic circuit (5) first signals output in the FM frequency band and second signals output in the DAB frequency band.

5. Antenna (100) according to one or more of the preceding claims, wherein said non-resonant radiating element (10) is configured to further simultaneously receive and transmit toward said electronic circuit (5) third signals emitted in a third GNSS frequency band.

6. Antenna (100) according to one or more of the preceding claims, wherein said electronic circuit board (5) comprises or is constituted by a printed circuit board disposed on said mounting base (1), and said non-resonant radiating element (10) comprises at least one portion (12) having a planar development that is disposed spaced apart from and substantially parallel to said printed circuit board.

7. Antenna (100) according to claim 6, in which said planar-developing portion (12) presents, when viewed in a plan view, a substantially quadrangular shape with a first edge (16) and a second edge (17) opposite each other cut according to an angle of about 45°.

8. Antenna (100) according to one or more of claims 6 and 7, comprising a patch (4) disposed below and spaced apart from said planar-developing portion (12).

9. Antenna (100) according to one or more of the preceding claims, comprising a cover (2) suitable for being coupled to said mounting base (1) and configured so that, when the antenna is mounted on the roof of a motor vehicle, the cover (2) reaches a maximum height (H), measured from the top surface (50) of the roof, of less than 40mm.

10. A motor vehicle, characterized by comprising at least one antenna (100) according to one or more of the preceding claims.

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