Integrated miniaturized RDS/DAB TMC antenna, communications device and method of integration

Abstract

 A communications device for vehicles adapted to receive traffic information via a traffic information service, a miniature integrated antenna adapted to receive signals in the FM/VHF/DAB band, and a method of integrating a miniature antenna within the communications device, wherein the integration enables the communication device to receive traffic information via a traffic information service transmitting signals in the FM/VHF/DAB band.

Description

FIELD OF THE INVENTION

[0001] The present invention relates generally to communications and more specifically to a novel and improved antenna for automotive applications. The present invention also relates to a novel and improved communications device for vehicles for providing traffic information.

BACKGROUND OF THE INVENTION

[0002] Latest state of the art communication devices currently may have many different kinds of applications, as Personal Digital Assistants (PDA), as Smart Phones, or as Personal Navigation Devices (PND), especially when adapted to provide a variety of services and able to function using a plurality of technologies and protocols. For automotive applications the visualisation in real time of the current state of the traffic is becoming increasingly popular and necessary. Therefore PVDs with location determination capability are increasingly supplied with traffic information, in order to automatically update the traffic depending on where the vehicle is located.

[0003] Such services may be implemented over the traffic message channel TMC of the FM Radio Data System FM RDS, over the Digital Audio Broadcasting DAB standard or over a system resulting from the combination of both systems. When using this protocol, the traffic information frames are transported through electromagnetic waves at FM/VHF/DAB frequency and received by an antenna connected to a TMC chipset able to process the signals. Due to the wavelength of these FM/VHF/DAB radio waves, antennas which may be used for this traffic information system are quite large, bulky and inconvenient.

[0004] The current commercialised solutions are based on a wire antenna, ranging in length from 75mm to 150mm. including suction-cups for fixation on the windscreen or on the dashboard, and sometimes with the TMC chipset at one extremity. The wire antenna offers good performances of reception as its characteristics resemble closely those of a monopole.

[0005] However wire antennas are inherently not robust and stable devices. Even the ones which are placed in the interior of a vehicle are impractically long and, since they are fixed to the vehicle, reduce the mobility of the PND device they are attached to.

[0006] The connection of the wire antenna to an existing PND has certain inconveniences, such as, it has to be attached manually by the end-user (that is, by the car driver mainly), it occupies part of the visibility of the driver with the consequent increase in the risk of accidents due to lack of visibility, and it may vibrate when driving resulting in a less comfortable driving experience. Additionally, the installation of an external antenna by a non-trained driver results in reduction in antenna performance, either due to non-optimal positioning of the antenna in relation to the communication device or other electronic components or a faulty connection. The need of disconnecting the wire antenna from the PND each time the PND is stored, when leaving the car, to prevent robbery or the intention to steal the PND, adds to the general inconvenience of such a device.

SUMMARY OF THE INVENTION

[0007] It is therefore an object of the present invention to provide a solution to the above mentioned problems.

[0008] According to one aspect of the invention a communications device is provided with at least one integrated antenna capable of performing wireless communications in order to provide traffic information.

[0009] In another aspect of the invention a personal navigation device is provided with at least one integrated antenna capable of performing wireless communications in order to provide location based traffic information.

[0010] Another aspect of the invention relates to a miniaturized RDS/DAB TMC antenna integrated into a communications device enabling it to provide traffic information.

[0011] In another aspect of the invention relates to a miniaturized RDS/DAB TMC antenna integrated into a personal navigation device enabling it to provide location based traffic information.

[0012] Another aspect of the invention relates to a method of integrating an RDS/DAB TMC antenna into a communications device enabling it to provide traffic information, or into a personal navigation device enabling it to provide location based traffic information.

[0013] The object of the invention is to specify a discrete antenna integrated inside a communications device which is still able to achieve good performances in terms of radio communication when compared to non-integrated external antennas, while solving the problems of external antennas of the prior art. This object is achieved by providing a self-contained communications device, including all the elements necessary to provide traffic information services, wherein all these elements are contained within the same housing. In this way handling of the device, and therefore the risk of incorrect manipulation, breaking, or robbery, is minimised, especially as the self-contained unit may be hidden without affecting its performance. With an integrated antenna, and communication modules, the number of accessories to be connected is also minimised.

[0014] Another object of the invention is to specify a discrete antenna integrated inside a communications device which is still able to achieve good performance in terms of radio communication when compared to external antennas even when co-located in close proximity to a location determination module.

[0015] The invention provides a method, apparatus and system elements that implement various aspects, embodiments, and features of the invention, as described in the following.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify correspondingly throughout.

Figure 1

depicts a miniature antenna according to the present invention.

Figure 2

shows examples of different fractal antenna patterns.

Figure 3

shows two different representations of a communications device according to the present invention wherein the antenna is integrated in a back housing cover.

Figure 4

shows the antenna integrated in a cradle a according to the present invention.

Figure 5

shows the antenna integrated in a holder according to the present invention.

Figure 6

is a graphic representation of the interfering signals due to an inadequate integration.

Figure 7

is a graphic representation of a Smith Diagram for antennas with and without a matching network.

Figure 8

is a graphic representation of the power transfer between an antenna and a TMC receiver.

Figure 9

represents a LC lumped element configuration for optimum signal transfer according to the present invention.

Figure 10

depicts another miniature antenna according to the present invention based on the Koch pattern.

Figure 11

depicts another miniature antenna according to the present invention based on Meander pattern.

DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

[0017] The Radio Data System (RDS) is a standard which enables information transmission via broadcast channels, and more specifically, using existing frequencies in the FM/VHF/DAB band. Since its inception, it has proved to be a very effective means of broadcasting data to vehicles, as most vehicles are equipped with standard radio receivers. The original data application was the transmission of the name of the radio channel being heard, as well as other information, such as the title or the author's name of the track being heard. Data transmission via FM RDS is performed using 57 kHz subcarriers to carry data at rates just over 1.1 kbit/s.

[0018] The analogue radio transmissions are currently being increasingly migrated to the digital standard. The Digital Audio Broadcasting DAB protocol will be the standard protocol for radio communications, as it offers a wide range of advantageous features, such as higher reuse factors, higher efficiency and lower interference, due to its use of Orthogonal Frequency Division Multiplexing OFDM, audio compression based on the MPEG standard, among others, thereby achieving data rates of approximately 192 kbit/s. Further advantages of the DAB system of audio broadcasting is its compatibility with information service providing technologies due to its digital format. As an advantageous example the application for the provision of traffic information to the mobile vehicle user could be implemented via DAB obtaining information from the Internet, either from a single page or a plurality of information providers. This option could be based on the availability of information depending on the geographical location of the user. This provision of information can also be implemented using the Traffic Message Chancel TMC.

[0019] It is to be understood that the advantageous features of the preferred embodiments of the present invention are equally applicable to all variants of this technology, be it analogue, or digital, according to the DAB standard or analogue FM, within VHF band allocated for FM broadcasting or in other areas of the VHF band, using the RDS service or the DAB broadcasting service.

[0020] Personal navigation devices (PND) have also lately populated the vehicular and non-vehicular markets. Location based services, either for the mobile or fixed user, either pedestrian or motorised, are being developed rapidly and provide solutions encompassing a wide variety of factors and parameters as inputs. For the case of vehicles, a very useful application would be the provision of the latest traffic information to the user, especially when this information may be made dependent on the current location of the portable device.

[0021] In order to receive up to date traffic information for vehicles, traffic information providers use a number of existing solutions. One prior art solution for transmitting traffic information is using the GSM system for mobile communications. However, GSM-based services are expensive and complex to operate, incurring excessive service charges to the end-user by the mobile service operators. Additionally country-wide coverage is not guaranteed as GSM base stations are normally not completely deployed throughout the full road network where commercial vehicles transit. These disadvantages are solved by the provision of the traffic information over a Traffic Message Channel (TMC), which may be transmitted using the FM RDS system or the digital radio DAB system. The RDS/DAB TMC protocol has as an advantage that the use of the FM/VHF/DAB band of frequencies is not subject to paid licenses, and thereby provides a free service. Additionally country wide coverage has been achieved already by radio broadcasting stations, thereby reaching most transit roads. The common element in these systems is the transmission of the traffic information via signals in the FM/VHF/DAB band 30MHz to 300 MHz, and more specifically, most applications focus on using the FM band of frequencies, which for Europe lies in the range of 87.5 MHz to 108 MHz, or in the band of frequencies corresponding to the Digital Audio Broadcasting DAB standard.

[0022] In the RDS/DAB TMC system, traffic information is typically collected from police databases, cameras, or traffic reporting pools. Such data collection can be performed manually by people, such as policemen or emergency service personnel, which after witnessing incidents report them to a central location. Data collection may also be performed automatically, by continuously processing vehicle speeds, radar output data and the like, in order to extract information representing the traffic load at particular sections of a road network. Once collected, traffic data is coded into a format to be transmitted as a message. This traffic message may include, among others, an event code, a time code and a location code. However other systems and implementations exist which also aim at providing traffic information.

[0023] Typical TMC receivers designed in commercially available TMC chipsets aim at processing the received signals rapidly in order to provide the fastest response to urgent traffic problems, such as accidents, or on-road dangers. VHF/DAB band signal reception is maximised by typically comprising interference reduction, multipath compensation, redundant reception, diversity reception algorithms, or other signal quality enhancement algorithms commonly known to the skilled person in the art.

[0024] TMC messages may he transmitted in real-time or periodically. The real-time transmission assures the fastest traffic state updating, whereas periodic transmission assures a constant monitoring of the situation. Traffic messages comprise not only those informing of an incident, but equally importantly those informing of the cancellation of incidents, in order to render the most accurate picture possible.

[0025] Typically TMC transmissions are performed in an RDS/DAB sub-carrier, and transmitted at lower power than their counterpart audio transmissions. Therefore TMC receivers arc designed to receive and decode the current traffic information even in rural regions with low signal strength reception due to low coverage. Many commercially available chipsets contain active components which amplify the weak signals received for further processing.

[0026] The advantages of receiving on-road latest traffic information, both for the benefit of the individual user as for the increase in road security for the general public, is normally enhanced by linking the specific information transmitted with the current location of the vehicle in question. Hence TMC messages typically contain a location code linked with the traffic information being broadcast, allowing receivers to filter out the relevant information depending on the current location of the receiver itself. Therefore communication devices for receiving traffic information are increasingly merged with location determination capability, providing for multifunctional devices, such as personal navigation devices, smart phones, portables personal digital assistants, fixed vehicle navigation modules, or the like.

[0027] Location determination protocols may be GSM-based, giving a rough approximation to the location of the device using algorithms such as triangulation. However the most exact location determination system is provided by satellite based systems. One such system is the Global Positioning System GPS, readily made for use for the general public, with world-wide coverage and tree of charge. Other systems such as GLONASS, IRNSS or COMPASS also exist for different geographical regions in the world. In the case of Europe the satellite-based system being developed is the GALILEO satellite system.

[0028] A GPS receiver requires a highly stable clock and an antenna capable of receiving signals from a plurality of GPS satellite at frequencies ranging from 1176.45 MHz to 1575.42 MHz. Theoretically only 3 or 4 satellites are necessary for pinpointing the exact location of the receiver, but current satellite receivers topically track more than 20.

[0029] Prior art solutions have attempted to provide traffic information to mobile or fixed vehicles by fixing well known FM antennas to portable communication devices. Such well known antennas, known as wire antennas, are composed of a single long wire connected to the devices. For communications in the VHF/DAB band, these wires tend to range between 75 cm to 150 cm, which relative to the average size of portable devices, can be considered as long accessories. Due to this higher than average length they must be fixed to the vehicle via, for example, suction cups, and are prone to being caught somehow, torn down and pulled forcefully out of the device's connector.

[0030] Especially relevant to the end user, these long wires reduce the mobility of the portable device, as it is not a direct and swift task to carry the portable device with the metre long wire attached to it, in case updated traffic information is desired outside the vehicle. Additionally, long wires connected to state of the art navigation devices are not user-friendly, thereby reducing the commercialisation of such products, and preventing the proliferation of location based traffic information devices. The broadcasting of latest traffic information via FM RDS/DAB TMC service has as a principle objective the prevention of accidents and securing of road traffic. Therefore the use of long wires has a direct negative consequence in fultilling this objective.

[0031] Additionally wire antennas are normally attached to the exterior of the vehicle, and as such are not robust and stable devices. Even the ones which may be used in the interior are impractically long and, since they arc fixed to the vehicle, reduce the mobility of the communication device they are attached to.

[0032] Even the connection of the wire antenna to an existing communication device has certain inconveniences, such as, it has to be attached manually by the end-user (that is, by the car driver mainly), it occupies part of the visibility of the driver with the consequent increase in the risk of accidents due to lack of visibility, and it may vibrate when driving resulting in a less comfortable driving experience. The need of disconnecting the wire antenna from the communication device each time the device is stored, when leaving the car, to prevent robbery or the intention to steal the device, add to the general inconvenience of such a device.

[0033] Therefore it is proposed to solve the above mentioned inconveniences, disadvantages, and problems via the integration of the antenna with the communication device in a preferred embodiment of the invention. Such integration would enable a communications device to receive RDS/DAB TMC signals without the inconveniences of the prior art devices. In another embodiment a location determination module comprising at least an antenna is also integrated, in order to provide a self-contained location based traffic information service device. Such device could be a personal navigation device with integrated traffic information processing capabilities. In yet another embodiment the antenna may be integrated directly within the portable device, in a single housing, or may be integrated into a vehicular accessory of the portable device. In either case the TMC electronic sub-system for receiving and processing traffic information from the antenna may also be integrated within the same housing as the antenna, or may be located separately. The communications device may either be portable or fixed to the vehicle, for example, as part of an on-board navigation system, or as part of an vehicle accessory, or communications device accessory. Independently from the specific embodiments and implementation details, the integrated antenna solves the disadvantages of the prior art antennas as well as providing improved communication capabilities necessary for receiving traffic information in a communication device.

[0034] FIG. 1 illustrates a miniature antenna 100 object of the present invention. This miniature antenna may be integrated, for example, into a communications device. However it will be readily apparent to the skilled person in the art that following the teachings of the present invention, it may also be integrated into other devices, potable or not. Due to the advantageous characteristics of the miniature antenna, it is specially suited for devices which require portability. In fact the integration of such antenna within a normally fixed communication device may render it advantageously a mobile device due to the integration.

[0035] In an embodiment antenna 100 may be a fractal antenna in the form of a circuit board 101, with a printed pattern 102, the antenna 100 being embedded inside a support. The support may either be a fixed support or it may be a mobile support, such as within a portable device. Due to the pattern 102 fixing process, there is no constraint that the board be flat. The circuit board 102 may have many different shapes and forms, be flat or curved, spherical or conical, as long as it can contain the copper serigraphy which will term the antenna pattern. The high adaptability of the pattern design allows for the integration of the miniature antenna 100 into a wide variety of supports. As in most antennas, antenna 100 comprises a feeding point 103. No matter the shape or form of the antenna, its fractal pattern is designed in order to enable it to receive RDS/DAB TMC waves in the VHF band, therefore providing the consequent advantages over the prior art. Examples of different fractal antenna patterns 102 can be seen in FIG. 2, FIG. 10 and FIG. 11.

[0036] Fractal antennas are characterised by their self-similar repetitive designs, enabling to maximise their length, or increase their perimeter, to cover inside sections or outside structures, of the suppor-ting material which can receive or transmit electromagnetic signals. The self-similar repetitive design is obtained via a multi-scalar repetition of a pattern, or motif, and results in the advantageous characteristics described, among which are its ability to operate simultaneously at a plurality of frequency bands, and frequency ranges, as well as providing the possibility of integration.

[0037] It is to be understood that the advantageous features of the preferred embodiments of the present invention are equally applicable to other types of antennas, be it fractal or otherwise, such PIFA, IFA, monopole, dipole, coupled monopole, or loop antennas.

[0038] Due to the specific frequency band of operation necessary in order to receive RDS/DAB TMC signals the inconvenience of the long wire antennas of the prior art are solved by providing an antenna with a highly compact fractal pattern. This characteristic enables the fractal antenna to be implemented in an exceptionally small surface area, resulting in miniature VHF antennas adapted to receive RDS/DAB TMC radio signals.

[0039] The fractal pattern may be printed on a standard copper printed circuit board. An example of such a board would be the thin FR4 PCB (example dimensions: 35µm Cu, 0.2mm thick) as well as other supports which offer a good compromise between ease of assembling, flexibility, cost and dielectric properties. As supports for the copper either blended plastic films, cartons or flex-film may be used. Other materials which offer the advantageous feature during integration of flexibility are ceramic-based materials. The antenna may be integrated into the device by attaching it via clips or heatstaking it to the device.

[0040] Referring to FIG. 2, one example of how the antenna may be designed is following the Hilbert geometry of space-filling miniature antennas as it offers a very high degree of miniaturisation. Consequently, it also offers good integration characteristics inside the device. The Hilbert geometry allows for a variety of designs for the antenna pattern 102. As can be seen in FIG. 2a; FIG. 2b, FIG. 2c and FIG. 2d, the fractal patterns 201, 202, 203, 204 may vary in complexity, degree in which the space of the antenna is filled and therefore effective length.

[0041] However other fractal antenna geometries exist which offer the advantages of high degree of miniaturisation. Referring to FIG. 10, is another example antenna 1000 of how the antenna 100 may be designed by using the Koch geometry 1002. Referring to FIG. 11, is another example antenna 1100 of how the antenna 100 may be designed by using the Meander geometry 1102.

[0042] The various patterns 201, 202, 203, 204, 1002, 1102 are carefully designed in order to provide a good compromise between antenna performance and degree of integration. The correct choice while designing the geometry of the antenna will depend on a number of factors, as well as finally affect the performance of a number of parameters of the antenna 100. Among these factors and parameters are antenna size, its relative gain, electromagnetic radiation patterns, the impedance characteristics, degree of flatness or curvature, frequency range of operation, antenna efficiency, specific absorption rate and polarization.

[0043] FIG. 3a and FIG. 3b depict the portable device 300 object of the present invention, and how the miniature antenna 100 may be integrated therein. As can be seen in FIG. 3a, the antenna 100 may be either integrated on the exterior of the back cover 301 of the portable device or it may be integrated between the back cover 301 and the front cover 303, inside the portable device. When integrated inside the back cover as in FIG. 3b, a pad 304 is attached to the feeding point 103 as an electrical connector. In this configuration the shape of the board 101 is chosen to fit in with the rest of the components of the portable device.

[0044] The advantages of integrating the miniature antenna within the same housing as the remaining components are readily apparent, as the fractal pattern 102 may be also designed to optimise its fit in relation to the remaining components, following the constraints of the printed circuit board size, area and forms. When integrated within the housing the antenna pattern 102 is designed to be located substantially along the outer perimeter of the communications device or of the antenna's PCB, in order to maximise its irradiating characteristics and minimise the interference and electromagnetic coupling of other electronic modules. The antenna may also be designed to be integrated ether in parallel to the PCB or perpendicular to it. Either way the advantages of flexibility while designing the fractal pattern exist in order to achieve the advantages of highest integration and lowest interference reception.

[0045] The fact that the board my require holes for fixation, gaps to allow the introduction of other components does not prevent the antenna's integration, as it would be a matter of designing the correct fractal pattern for each specific fit, taking into account not only the physical constraints as mentioned, but also the electrical and electromagnetic requirements of the miniature antenna, in particular referring to RDS/DAB TMC antennas operating in the VHF band. Therefore antenna 100 has at least one feeding point, however optionally the antenna 100 could have more than one feeding point, or more than one grounding points connected to the main PCB of the communications device.

[0046] In order to extend the possibilities of integration, to enable a certain customisation of the integrated miniature antenna dependent on the characteristics of the portable device, other embodiments of the invention exist. FIG. 4 depicts the integration of the miniature antenna within the cradle 401 of the portable device. Such a cradle is typically used in vehicles, and serves to host the device, be it either a personal navigation device or any other communication device. The cradle comprises a connector 402 as an electrical connection point with the portable device and a suction mount 403. In this embodiment the cradle may host the integrated antenna alone, or optionally, also the TMC receiver chipset.

[0047] In such a configuration the portable device would not be enabled to receive traffic information when not connected to the cradle unless an additional wireless communication module were also integrated within the cradle. In this embodiment this integration would also conform to the objective of the present invention, as the wireless antenna for communication would also be designed as a miniature antenna 100, and could also be hosted within the cradle, together with the corresponding wireless transceiver and processing elements. As an example, it is common to find Bluetooth modules within almost every commercially available portable device. Hence the integration process for receiving traffic information, when hosed by an element not part of the device itself, could include apart from a TMC module also a Bluetooth module. This integration would include two miniature antennas, one for TMC and the other for Bluetooth, with the corresponding transceivers and processing elements coupled either within the same housing, or separately.

[0048] In FIG. 5 the antenna 100 is integrated within the holder 500 of the portable device. The advantages of this embodiment are readily apparent, as the antenna is integrated into an otherwise unused space, therefore saving on space within the portable device 300 itself. Similar to the embodiment of FIG. 4, when the TMC module is integrated within such separate elements from the portable device, many different applications exist when integrated in addition with a wireless communication module.

[0049] In one example the wireless communication module could conform to the Bluetooth standard. As an example, this TMC/Bluetooth module would enable a portable device within the area of the whole vehicle to receive the latest traffic information, and even in a radius around the vehicle. In one embodiment different, for very large vehicles, such as trains or lorries, the latest traffic information could even be received and displayed in areas far away from the vehicle's cockpit, or sitting area. In another embodiment, even within the sitting area, for example of a bus, there could be several seat displays, in order to inform the passengers of the latest traffic conditions, for example, in the case of an accident.

[0050] In an embodiment where the portable device includes also a location determination module for navigation purposes, this would enable the device to be used even outside the vehicle in order to update the route according to the current location and the latest traffic information.

[0051] In another embodiment traffic information sharing would also be possible, as this combined traffic/communication module would broadeast the latest traffic information to all neighbouring moving, or stationary, vehicles. This would enable the neighbouring vehicles having portable navigation devices without traffic information receiving capabilities to receive such information via a wireless communications module, such as a Bluetooth module, and therefore update their routes via a recalculation process. This kind of application could require these neighbouring vehicles to enable an option in their portable navigation devices to receive broadcast traffic information sent via a wireless communication protocol, as an example, Bluetooth or WLAN.

[0052] Yet in another embodiment of the present invention, the antenna pattern 102 may be directly printed onto the printed circuit board 101 of a communication device 300. In situations where the amount of space to integrate the antenna is highly limited, and not even a miniature antenna according to an aspect of the present invention may be fit into the available space, the RDS/DAB TMC antenna pattern 102 printed directly onto a pre-existent board 101 would provide such communication device with traffic information receiving capabilities. As an example of such scenario, latest generation media players, which play, as an example, MP3 music tracks, are being designed in very small dimensions, and in order to display the details of the track being heard, contain also a small display panel. Such small devices may be integrated with the RDS/DAB TMC antenna of the present invention, however, due to the close proximity of the device's ground plane to the antenna, careful attention has to be paid during the integration process in order to minimise capacitative effect, electromagnetic coupling, or other types of interference due to the antenna fractal pattern being printed or etched on the same board as the portable device's main board.

[0053] These integration problems are not limited to the embodiment as just described. Decrease in the antenna and/or receiver's performance, due to undesired capacitative effects, electromagnetic coupling, or interference from other electronic components, are issues that have to be dealt with while producing the miniature RDS/DAB TMC antenna object of the present invention and in the process of integrating the miniature antenna into communication devices resulting in the communication devices object of the present invention.

[0054] The extremely small dimensions in which the FM/VHF/DAB band antenna is implemented increases the design and manufacturing constraints to be fulfilled in order to provide a well performing product which solves the problems of the antennas of the prior art. Such a design process, ether for producing the miniature antenna itself, or the portable device object of the present invention, is a complex iterative process requiring not only careful conceptual design, but also extended Electromagnetic Compatibility simulations. As a general guideline, in order to maximise the correct performance of the antenna 100 and the communication device 300, at least one or more of the following conditions have to be fulfilled, either alone or in combination:

• The antenna's feeding point 103 should be placed as far away as possible from the device's battery. A minimum of approximately 18mm to 22mm is recommended.
• The antenna's feeding point 103 should be placed as close as possible to the TMC chipset input RF receiver. The copper track between them should not exceed approximately 33mm to 37mm.
• In the embodiment where an additional module exists, for example, a location determination module with a GPS antenna, the miniature RDS/DAB TMC antenna's feeding point 103 should be placed as far away as possible from the GPS antenna's ground-plane. A minimum of approximately 28 to 32mm is recommended.
• Any device shielding components should be placed no more than 1.5mm from the antenna.
• Due to the limited size available, maximising this usable surface area for antenna integration is an important factor taken into account in this process. Fractal antennas due to the flexibility in layout they offer are particularly suited for this purpose. The layout of the antenna also plays a role. The highest integration is achieved with an antenna integrated in parallel to the ground plane of the device. However if the antenna is placed perpendicular to the PCB, it is subjected to less interference from other neighbouring electronic modules, such as the location determination navigation module. Therefore it also conforms to the iterative integration process to find the optimum placement for maximising integration and minimising the effect of interference on the antenna.

[0055] The optimisation of these general parameters is a complex iterative procedure, for which an electromagnetic compatibility EMC simulation is necessary. The non-desirable signals, such as noisy and spurious transmission within the FM/VHF/DAB band, emitted by all the electronic components installed inside the portable device degrade the antenna's performance as such, as well as the overall system's functionality.

[0056] The resulting miniature antenna may have dimensions ranging as low as 68mm x 68mm in its largest surface area. As can be realised, when compared to prior art RDS/DAB TMC antennas, the antenna 100 is very compact. It is also completely passive, in the sense that there are no additional active systems to improve the overall performance by, as an example, amplifying the signal or filtering it.

[0057] Optionally it is possible to include a matching network as another passive element without affecting the antenna's performance. The impedance matching network, which may be implemented as an LC circuit, to be placed between the antenna feeding point 103 and the TMC chipset receiver, has the function of preventing any further losses in the interface between these two components due to variations in impedances, resulting in a maximum signal transfer from the antenna 100 to the receiver.

[0058] FIG. 6 is a graphic representation of the problem being confronted with, and the improvement obtained, via the iterative process described. The top line 601 depicts the level of interference measured for the case of a conventional FM antenna directly integrated within a portable device. The bottom line 602 depicts the level of the interfering signals of an integrated miniature antenna conforming to EMC restrictions for adequate performance.

[0059] For such an improvement over prior art solutions to be possible, the antenna itself should have as much as possible an isotropic behaviour in reception. This omnidirectional characteristic is obtained by an iterative optimisation process to find the global best performance provided by the following parameters:

• the fractal pattern 102 design;
• the position of the antenna 100 with respect to the device's ground plane and other components. This positioning is critical when other modules, such as location determination modules, such as according to standard GPS satellite location determination protocols, or wireless communication modules, such as Bluetooth, GSM, or WLAN, as well as a number of shielding components are included within the same housing;
• the design and parameter choice for the impedance matching network.

[0060] FIG. 7a depicts a Smith Diagram of an antenna without a matching network and FIG. 7b depicts an antenna with a matching network attached. It is clear from the comparison of these two charts how the antenna impedance when better matched to the TMC chipset input impedance results in a minimum loss of signal strength between the two components. Such advantage is again readily apparent from the signal transfer graphical representation of FIG. 9, where the top curve 801 represents the signal strength with a matching network and the bottom curve 802 represents the signal strength without a matching network. As can be seen curve 802 depicts heavy losses when compared to curve 801, especially in the lower regions of the spectrum.

[0061] An example of a matching network may be an LC lumped circuit as depicted in FIG. 9. This circuit is composed of a set of capacitors 902, 903 and 905 connected partially in series and partially in parallel, and further connected to an inductor 906. Connectors 901 and 904 serve as connection points to the antenna's feeding point 103 on one hand and to the input of the TMC receiver on the other.

[0062] It is to be understood that the advantageous features of the preferred embodiments of the present invention are equally applicable to all variants of the radio broadcasting technology, be it analogue, or digital, according to the DAB standard or analogue FM, within VHF band allocated for FM broadcasting or in other areas of the VHF band. The common element is the broad range of frequencies commonly known as the FM/VHF/DAB band, normally comprising frequency modulated FM signals, which define a specific wavelength, and therefore antenna dimensions and characteristics, object of the present invention.

[0063] When the iterative integration and optimisation process is performed correctly, the improvement in antenna performance allows it to receive a wide range of signal strengths, from weak to strong signals. In scenarios where the electromagnetic field is very weak, such as when the portable device finds itself in a region of low coverage, or is situated in a geographical area very far from the emitter, or if certain obstacles block the correct reception of radio waves, the antenna object of the present invention has proven to be able to achieve still 80% to 90% of the performance level of a conventional 75cm long wire antenna. Considering the relative miniaturisation combined with the complex integration into the portable device, this translates to an even considerably larger overall improvement,

[0064] It is to be understood to the skilled person in the art that the disclosure of the various embodiments of the invention is intended as non-limitative preferred examples and realisations of the inventions, and therefore features of different embodiments may be readily combined within the scope of the general inventive concept described.

[0065] The various logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented of performed with a general purpose processor, a digital signal processor (DSP), and application specific integrate circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine.

[0066] The methods or algorithms described may be embodied directly in hardware, in a software module executed by a processor, or a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0067] The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art. Likewise, the generic principles disclosed herein may be applied without departing from the spirit or scope of the invention. Therefore, the present invention is not intended to be limited by the embodiments disclosed but to be accorded the widest scope consistent with the principles and the novel features disclosed herein.

[0068] Those skilled in the art should appreciate that the foregoing discussion of one or more embodiments does not limit the present invention, nor do the accompanying figures. Rather, the present invention is limited only by the following claims.

Claims

1. A communications device for vehicles, characterised in that it is adapted to receive traffic information via a traffic information service broadcasting in the VHF/DAB band, comprising:

- at least one antenna and a signal receiver for traffic information reception;

- wherein the at least one antenna is integrated within the device.

2. The communications device of claim 1, wherein the device is portable or fixed to the vehicle via a support and wherein the VHF/DAB band of frequencies comprises analogue frequency modulated FM band as well as the digital audio broadcasting DAB band.

3. The communications device of any of the preceding claims further comprising at least one antenna for location determination and a processor for location determination, wherein at least the location determination antenna is also integrated within the device.

4. The communications device of any of the preceding claims wherein the at least one antenna is integrated within the housing of the device, inside its back cover, or on the exterior of its back cover.

5. The communications device of any of the preceding claims, wherein the support may be a cradle for housing the device, or a holder for attaching the device and the cradle to the vehicle, and wherein the at least one antenna is integrated within the support of the device.

6. The communications device of any of the preceding claims, wherein the at least one antenna is a fractal antenna, or PIFA antenna, or IFA antenna, or monopole antenna, or dipole antenna, or coupled monopole antenna, or a loop antenna.

7. The communications device of any of the preceding claims wherein the antenna may be placed in parallel or perpendicular to the printed circuit board of the communications device.

8. The communications device of any of the preceding claims wherein the at least one fractal antenna has a fractal pattern located substantially along the outer perimeter of the communication device.

9. The communications device of any of the preceding claims, wherein the at least one antenna is connected directly to the signal receiver, or via a matched network.

10. The communications device of claim 9, wherein the matched network is an LC lumped circuit.

11. The communications device of any of the preceding claims, wherein the traffic information is broadcast through the Radio Data System, RDS, or via the Digital Audio Broadcasting DAB system, or a combination of both, using the Traffic Message Channel, TMC, or another channel adapted for traffic information transmission.

12. A VHF/DAB antenna for vehicles characterised in that it is adapted to receive traffic information via a traffic information service broadcasting in the VHF/DAB band, wherein the antenna is adapted to be integrated within a communications device.

13. The antenna of claim 12, wherein the antenna is a fractal antenna and the fractal pattern is adapted for integration within the communication device and wherein the VHF/DAB band of frequencies comprises analogue frequency modulated FM band as well as the digital audio broadeasting DAB band.

14. The antenna of any of the preceding claims 12 to 13, wherein the fractal pattern substantially fills the central part of the antenna, or the outer diameter, or a combination of both.

15. The antenna of any of the preceding claims 1 to 14, wherein the fractal pattern follows the Hilbert geometry or Koch geometry or Meander geometry, or a combination of any geometry conforming to its integration.

16. The antenna of any of the preceding claims 12 to 15, further comprising a printed circuit board adapted to any shape and form, such as flat, curved, spherical, circular, conical, or cubed, and wherein the printed circuit board is made from a flexible ceramic-based, plastic, flex-film or carton material.

17. A method of integrating a VHF/DAB antenna into a communication device for vehicles characterised in that the integration step enables the device to receive traffic information via a traffic information service broadcasting in the VHF/DAB band.

18. The method of claim 17, wherein the antenna is a fractal antenna and the integration is an iterative process for maximizing the antenna's electromagnetic properties by optimizing the fractal antenna pattern's electromagnetic characteristics to the device's physical and electromagnetic constraints and wherein the VHF/DAB band of frequencies comprises analogue frequency modulated FM band as well as the digital audio broadcasting DAB band.

19. The method of claim 18, wherein the integration further comprises the steps of:

- maximizing the distance between a feeding point of the antenna and other electric components of the device, such as other antennas or batteries:

- minimizing the distance between a feeding point of the antenna and a VHF/DAB signal receiver for receiving the signal from the antenna; and

- minimizing the distance between the antenna and a shielding component for reducing electromagnetic coupling; and

- shaping the antenna to maximize its integration while minimizing the interference received.

Drawing