FIELD OF THE INVENTION

[0001] The present invention relates to the field of wire-like antennas deposited on vehicle glazing.

BACKGROUND OF THE INVENTION

[0002] Nowadays there is a request from vehicle manufacturers to mount an increasing number of antennas in vehicles. Such antennas aim to render possible connected services (3G/4G/5G telecom, GNSS, RKE, V2X, Bluetooth, Wifi) or to allow broadcasting services (AM, FM, DAB, TV). The trend is to deploy those antennas on the roof and on the window of the vehicle.

[0003] Putting antennas on both the roof and the window of a vehicle leads to strong coupling of antennas, so that antennas interfere with each other. It means one antenna affects the performance of another antenna, and it leads to complex optimization of antenna performances.

[0004] Furthermore, in case of a combination of at least two antennas, where one is an active antenna, meaning an antenna both receiving and transmitting radio signal, the electronics connected to the other antenna get distortion due to the strong signal interference from the active antenna, leading to the electronics working unproperly. This problem limits the freedom of deployment of antennas in vehicles, and renders complex the designing process of vehicles.

[0005] WO2015/019904 discloses an antenna device which can reduce mutual interference between two antenna elements arranged adjacent to the same conductor, such as the roof of a vehicle. It relates to two antennas whose frequency bands are close to each other, such as, for example, a TV antenna between 470 and 710 MHz and an ITS (equivalent to V2X) antenna at 760 MHz. A wire-like parasitic element (typically L-shaped) is put between the two antennas to reduce the coupling. This document also specifies the ideal length, shape and location of the parasitic element to reduce the coupling efficiently.

[0006] The parasitic element is typically L-shaped with a certain length on the window glass. The parasitic element’s effect depends on its length, its position and its shape. If the combined set of length, position and shape is not ideal, the parasitic element does not have the decoupling effect.

[0007] Besides, in case the two antennas are placed close to each other, the parasitic element cannot be put between them due to the lack of space.

[0008] Moreover, such solution is not adapted to cancel multiple noise radio frequencies. The parasitic element is indeed designed for a specific frequency. It may rather increase the coupling at other frequency unexpectedly. It is therefore not adapted for multi-band antennas.

[0009] Additionally, the parasitic element is visible from the passenger of the vehicle. One branch of the L-shaped parasitic element cannot be hidden by the usual black band on the window glass. It leads to bad aesthetics and it may further have bad influence on driver’s view and therefore on safety.

SUMMARY OF THE INVENTION

[0010] The present invention concerns a wire-like antenna deposited on a vehicle glazing, near an edge of a vehicle opening. The wire-like antenna comprises a feeding point, a first radiator part able to radiate and/or receive a first radio signal, the first radiator part being at least partially substantially orthogonal to the closest edge of the vehicle opening, and an equivalent transmission line part able to transmit the first radio signal between the feeding point and the first radiator part, the equivalent transmission line part being substantially parallel to the edge of the vehicle opening. The wire-like antenna further comprises at least a first isolation tuner part, the first isolation tuner part being substantially parallel to the edge of the vehicle opening. The first isolation tuner part is connected to the equivalent transmission line part at a first connection point.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention will now be described further, byway of examples, with reference to the accompanying drawings, wherein like reference numerals refer to like elements in the various figures. These examples are provided by way of illustration and not of limitation. The drawings are a schematic representation and not true to scale. The drawings do not restrict the invention in any way. More advantages will be explained with examples. Fig.1a illustrates one example of a vehicle glazing. Fig.lb illustrates an interfering antenna.

Fig.2 illustrates a portion of the vehicle glazing equipped with a wire-like antenna according to the present invention.

Fig.3 illustrates an embodiment where the wire-like antenna comprises a first and a second isolation tuner parts.

Fig.4 illustrates a case where the wire-like antenna comprises a first and a second radiator part.

Fig.5 illustrates an embodiment where the feeding point, the equivalent transmission line part, the first isolation tuner part and the second isolation tuner part are masked by a black band present on the vehicle glazing.

Fig.6a illustrates an example of a wire-like antenna without the present invention. Fig.6b illustrates the same example of a wire-like antenna with two isolation tuner parts according to the present invention.

Fig.7a illustrates the measurement results of the coupling between the wire-like antenna and a first interfering antenna placed on a roof of the vehicle. Fig.7b illustrates the measurement results of the coupling between the wire-like antenna and a second interfering antenna placed on a roof of the vehicle.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0012] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims.

[0013] While some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0014] The present invention proposes a wire-like antenna, meaning an antenna in the form of a wire, as commonly used in the automotive field. A vehicle includes car, van, lorry, motorbike, bus, tram, train, drone, airplane, helicopter and the like. A vehicle glazing can refer to any window on a car, including a windshield, a rearlite, a sidelite and/or a roof. [0015] A wire-like antenna can be formed by printing and baking paste containing conductive metal particles such as a silver paste, on an inner surface of a pane of glass. However, the invention is not limited to this forming method. A linear element or a foil element made of a conductive material such as copper may be formed on an inner or outer surface of a pane of glass or may be affixed to a pane of glass with an adhesive or may be provided between two or more panes of glass (laminated glazing). Additionally, a wire-like antenna may be formed by forming a conductor layer given synthetic resin film in which a conductor layer of an antenna conductor is provided, of a synthetic resin film. Further, a wire-like antenna may be formed by forming a flexible circuit board on which an antenna conductor is formed.

[0016] The wire-like antenna is intended to be deposited near an edge of a vehicle opening. The vehicle opening is closed by the glazing. The antenna is usually deposited near the edge of such glazing, but it may happen the edge of the glazing does not coincide with the edge of the vehicle opening, for example when the glazing extends beyond the edge of the vehicle opening.

[0017] The present wire-like antenna comprises a feeding point. The feeding point allows for electricity furnishing of the antenna.

[0018] The wire-like antenna further comprises at least a first radiator part. This radiator part is able to radiate and/or receive a radio signal at radio frequency fri in a first frequency band. The radiator part is at least partially substantially orthogonal to the closest edge of the vehicle opening, as well as being orthogonal to the closest edge of the vehicle glazing. If not, meaning if the radiator part was parallel to the edge of the vehicle glazing, then the propagation of the radio signal would become weak due to cancelling effect by image current induced on the edge of the vehicle opening. As the radiator part is at least substantially orthogonal to the edge of the vehicle glazing, the image current does not prevent the propagation of the radio wave.

[0019] The wire-like antenna further comprises an equivalent transmission line part. This equivalent transmission line part is intended to transmit the first radio signal between the feeding point and the first radiator part. The equivalent transmission line part is substantially parallel to the closest edge of the vehicle opening, as well as parallel to the closest edge of the vehicle glazing. The equivalent transmission line part is put close to the edge of window glass, as well as the edge of the vehicle body opening. [0020] The wire-like antenna further comprises a first isolation tuner part. This first isolation tuner part may be L-shaped, T-shaped, meander-shaped or any other shape known by the skilled in the art. The first isolation tuner part is substantially parallel to the edge of the vehicle opening, meaning the longest part of the first isolation tuner part is parallel to the edge of the vehicle opening. One end of the first isolation tuner part is connected to the equivalent transmission line part at a first connection point.

[0021] According to a preferred embodiment, the distance cfej between the equivalent transmission line part and the edge of the opening of the vehicle satisfies: where A _rl is the wavelength of the radio signal corresponding to the radio frequency fri in a first frequency band, a glass is the effective shortening ratio of wavelength on glass, typically comprised between 0.5 and 0.7 depending on the thickness, glass material composition and the antenna wires’ thickness and width. With C/EQ satisfying the equation above, the equivalent transmission line part realizes the efficient transmission of the first radio signal between the feeding point and the radiator part.

[0022] According to a preferred embodiment, the length L _IS01 of the path from the feeding point to the open end of the first isolation tuner part satisfies: is the wavelength of a first interfering radio signal to be decoupled from the wire-like antenna, N _IS01 is an integer larger or equal to 1 , preferably comprised between 1 and 5, more preferably equal to 1 or 2, k _± is a decimal representing the bandwidth (in ratio relative to the first interfering radio frequency fn) in which the isolation effect can be obtained. Preferably, k _± is less or equal to 0.1 , more preferably less or equal to 0.05. The inventors indeed found that the isolation effect by the first isolation tuner part is effective in the bandwidth of +-10% of the interfering frequency fn, more effective in the band width of +-5% of the interfering frequency fn in the typical case for automotive window case (meaning the width of the wire of the first isolation tuner is between 0.4mm and 1 mm). The value k _± becomes larger if the width of the wire is increased. Lcabie is the length of the feeding cable for the antenna, connecting the feeding point of the wire-like antenna to an amplifier input, acabie is the effective shortening ratio of wavelength on cable.

[0023] It has been found that an isolation tuner part satisfying the above formula allows for a good isolation from another antenna emitting a signal at the interfering frequency fn by making the impedance of the wire-like antenna high at the radio frequency fn selectively. There is therefore no need to put additional element, such as a noise canceller element between the wire-like antenna on the vehicle glazing and another antenna on the roof of the vehicle, so that the isolation effect can be obtained even though there is not enough space between those antennas.

[0024] According to a preferred embodiment, the wire-like antenna further comprises a second isolation tuner part on the equivalent transmission line part. This second isolation tuner part may be L-shaped, T-shaped, meander-shaped or any other shape known by the skilled in the art. This second isolation tuner part is substantially parallel to the edge of the vehicle opening, meaning the longest part of the second isolation tuner part is parallel to the edge of the vehicle opening. The second isolation tuner part is connected to the equivalent transmission line part at a second connection point.

[0025] According to a preferred embodiment, the length L _IS02 of the path from the feeding point to the open end of the second isolation tuner part satisfies: where A ₍₂ is the wavelength of a second interfering radio signal to be decoupled from the wire-like antenna, N _IS02 is an integer larger or equal to 1 , preferably comprised between 1 and 5, more preferably equal to 1 or 2, k ₂ is a decimal representing the bandwidth (in ratio relative to the second interfering radio frequency fa) in which the isolation effect can be obtained. k ₂ is less or equal to 0.1 , preferably less or equal to 0.05.

[0026] It has been found that a second isolation tuner part satisfying the above equation allows for a good isolation from another antenna emitting a signal at the interfering frequency fa by making the impedance of the wire-like antenna high at the radio frequency fi2 selectively. There is therefore no need to put additional element, such as a noise canceller element between the wire-like antenna and another antenna, so that the isolation effect can be obtained even though there is not enough space between those antennas. The invention therefore allows for two and even more isolation tuner parts. It allows for good isolation towards multiple radio signals.

[0027] According to a preferred embodiment, the length L _RAD1 of the path from the feeding point to the open end of the first radiator part satisfies: where N _RAD1 is an integer larger or equal to 1 , preferably N _RAD1 is equal to 1 , 2, 3, 4 or 5.

[0028] According to a preferred embodiment, the wire-like antenna further comprises a second radiator part able to radiate and/or receive a radio signal in a second frequency band in which the wire-like antenna should be functional as an antenna. The second radiator part is at least partially substantially orthogonal to the edge of the vehicle glazing. The equivalent transmission line part is able to transmit the radio signal in the second frequency band between the feeding point and the second radiator part.

[0029] According to a preferred embodiment, the length L _RAD2 of path from the feeding point to the open end of the second radiator part satisfies: where N _RAD2 is an integer larger or equal to 1 , preferably N _RAD2 is equal to 1 , 2, 3, 4 or 5, and _r2 is the wavelength of the radio signal at the radio frequency fa in the second frequency band to be received and/or emitted by the wire-like antenna.

[0030] According to a preferred embodiment, the radio signal frequencies fa, fa, fn and fa satisfy: fr2 < fll < frl fr2 < fl2 < frl meaning the wire-like antenna is designed to be functional in two different frequency bands, and the radio frequencies of the interfering signals exist in between those two frequency bands. Thus, the present wire-like antenna could achieve good performance as an antenna in two frequency bands as well as isolating the interfering signals between them.

[0031] For example, the first frequency band can be 470-710 MHz (meaning fri is one of the frequency from 470MHz to 710MHz) and the second frequency band can be 170-240MHz (meaning fr2 is one of the frequency from 170MHz to 240MHz), and the first interfering frequency fn can be 434 MHz and the second interfering frequency fa can be 315 MHz, both corresponding to RKE frequencies. This way the wire-like antenna is a dual band antenna for TV and DAB functions and isolated from the interfering signals from the other antenna for RKE function.

[0032] According to a preferred embodiment, the feeding point, the equivalent transmission line part, the first isolation tuner part and eventually the second isolation tuner part are masked by a black band on the vehicle glazing. As whole the elements of the wire-like antenna are put along the edge of the vehicle glazing, they can be hidden by a black layer printed on the glass. This way they are less visible from the passengers of the vehicle. Such black band can be made of ceramic or black enamel.

[0033] Fig.1a illustrates one example of a vehicle glazing (100), here being a rearlite, meaning the glazing placed in the vehicle opening (110) present in the back of a vehicle. A wire-like antenna (1 ) is usually placed on such rearlite, even if it can be placed elsewhere, meaning on another glazing of the vehicle.

[0034] Fig.1b illustrates an interfering antenna (200). It is usually placed on the roof of the vehicle, even if it can be put elsewhere, meaning on another exterior or interior part of the vehicle. As illustrated in the present figure, the vehicle glazing (100) usually exceeds the vehicle opening (110), meaning the vehicle glazing is bigger in size then the vehicle opening (110). However, the vehicle glazing (100) can also match the vehicle opening (110). For ease of the representation, the following figures will represent this last case, without limiting the present invention to this case.

[0035] Fig.2 illustrates a portion of the vehicle glazing (100). The vehicle glazing (100) is equipped with a wire-like antenna (1 ) according to the present invention. The wirelike antenna (1 ) is deposited next to an edge of the vehicle opening (110).

[0036] The wire-like antenna (1 ) comprises a feeding point (2), a radiator part (31 ) and an equivalent transmission line part (4). The radiator part (31 ) is at least partially substantially orthogonal to the closest edge of the vehicle opening (110), as well as being orthogonal to the closest edge of the vehicle glazing (100). The equivalent transmission line part (4) connects the feeding point (2) and the radiator part (31 ) so that the wire-like antenna (1 ) is able to receive and/or transmit a radio signal of a wavelength A _rl through the radiator part (31 ). The equivalent transmission line part (4) is substantially parallel to the closest edge of the vehicle opening (110), as well as parallel to the closest edge of the vehicle glazing (100). The equivalent transmission line part (4) is put close to the edge of the vehicle opening (110), as well as to the edge of the vehicle glazing (100).

[0037] The wire-like antenna (1 ) further comprises an isolation tuner part (51 ). The isolation tuner part (51 ) is substantially parallel to the edge of the vehicle opening (110), as well as to the edge of the vehicle glazing (100). The isolation tuner part (51 ) is connected to the equivalent transmission line part (4) at a first connection point (510).

[0038] Fig.3 illustrates an embodiment where the wire-like antenna (1 ) comprises a first and a second isolation tuner parts (51 , 52). Both isolation tuner parts are substantially parallel to the edge of the vehicle opening (110), as well as to the edge of the vehicle glazing (100). The first isolation tuner part (51 ) is connected to the equivalent transmission line part (4) at a first connection point (510), while the second isolation tuner part (52) is connected to the equivalent transmission line part (4) at a second connection point (520).

[0039] Fig.4 illustrates a case where the wire-like antenna (1 ) comprises a first and a second radiator part (31 , 32). Both radiator parts (31 , 32) are able to radiate and/or receive a radio signal. Both radiator parts (31 , 32) are at least partially substantially orthogonal to the edge of the vehicle opening (110), as well as to the edge of the vehicle glazing (100). The equivalent transmission line part (4) is able to transmit both radio signals emitted and/or received by the radiator parts (31 , 32).

[0040] Fig.5 illustrates an embodiment where the feeding point (2), the equivalent transmission line part (4), the first L-shaped isolation tuner part (51 ) and the second L-shaped isolation tuner part (52) are masked by a black band (300) present on the vehicle glazing (100).

PRACTICAL EXAMPLE

[0041] Fig.6a illustrates an example of a wire-like antenna (1 ) without the present invention. The wire-like antenna (1 ) is placed on a tempered glass (thickness 3.1 mm). The wire-like antenna (1 ) is composed of printed silver ceramics lines (line width 0.7mm), meaning a _gias s is approximately 0.67. Furthermore, the wire-like antenna (1 ) is connected to an amplifier by a typical cable wrapped by thin PVC layer, meaning Ocabie is approximately 0.97.

[0042] Fig.6b illustrates the same example of a wire-like antenna (1 ), but this time with two isolation tuner parts (51 , 52) according to the present invention, as described in Fig.3.

[0043] To show the effectiveness of the two isolation tuner parts (51 , 52), two sets of experiments were done with two different interfering antennas (200, 210) on a roof of a vehicle. The first interfering antenna (200) transmits RKE signal at 434MHz, and the second interfering antenna (210) transmits RKE signal at 315MHz. In most European countries, RKE must use 434MHz, while in Japan and in the United States, RKE must use 315MHz. Such rules are defined by each country’s government. As vehicle manufacturers want to have only one wire-like antenna design for all countries in order to reduce the designing/manufacturing cost and for easy project management, best is to optimize the wire-like antenna for both frequencies. The present invention, allowing multiple frequencies isolation by using several isolation tuner parts, is therefore clearly replying to such request by vehicle manufacturers.

[0044] In each experiments, signal transmission between the wire-like antenna (1 ) on the vehicle glazing (100) (including the feeding cable connecting the feeding point to amplifier) and the interfering antennas (200, 210) on the roof were measured by vector network analyzer.

[0045] Fig.7a illustrates the measurement results of the coupling between the wirelike antenna (1 ) and an interfering antenna (200) placed on a roof of the vehicle. As shown in this graph, the wire-like antenna (1 ) comprising the two isolation tuner parts (51 , 52) as shown in Fig.6b has a weaker coupling, meaning a signal transmission lower than -20dB, to the interfering antenna (200) than the comparative example as shown in Fig.6a.

[0046] Fig.7b illustrates the measurement results of the coupling between the wirelike antenna (1 ) and an interfering antenna (210) placed on a roof of the vehicle. As shown in this graph, the wire-like antenna (1 ) comprising the two isolation tuner parts (51 , 52) as shown in Fig.6b has a weaker coupling, meaning a signal transmission lower than -20dB, to the interfering antenna (210) than the comparative example as shown in Fig.6a.

[0047] These sets of results prove the effectiveness of the isolation tuner parts (51 , 52) for decoupling the wire-like antenna (1 ) deposited on the vehicle glazing from the interfering antennas (200, 210) placed on roof. Furthermore, by comparing the two curves on both graphs (continuous line and dotted line in the graphs), the effect of the isolation tuner parts (51 , 52), meaning a decrease of transmission, was observed not only at frequency points fn and fi2 but also in the bandwidths around fn and fi2, which are +/-10% of center frequencies fn and fi2 in this case. It reveals that the isolation tuner parts (51 , 52) have such isolation effect in the bandwidth of around +/-10% of interfering frequency in typical window glass application cases.

[0048] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illus- trative or exemplary and not restrictive. The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the invention may be practiced in many ways. The invention is not limited to the disclosed embodiments.