Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
1995-05-17
2001-11-06
Wimer, Michael C. (Department: 2514)
Communications: radio wave antennas
Antennas
Microstrip
C343S713000
Reexamination Certificate
active
06313796
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is related to a pane, in particular a laminated pane, for automobiles, for example, equipped with electrical conductors serving as an antenna inside the pane.
2. Description of the Related Art
It is known, notably from Patent Application EP-0 325 510, to embed metal wires in the intermediate film of plastic material in a laminated pane. These metal wires can serve as a radio antenna for frequencies which in general do not exceed 3 GHz. For the reception or transmission of signals having a higher frequency, and notably of ultra high frequency signals, these antenna made from metal wires are no longer effective. For these frequencies, it is known to use metal surfaces termed microstrips or “pellets”. On the other hand, this microstrip is not always sufficient and should advantageously be associated with an earth (ground) plane which is a conducting film of larger area. These two films are then separated from each other by a dielectric.
To improve reception, it is also possible to associate several microstrips connected in accordance with the techniques known to the person skilled in the art.
At present this type of frequency and, more especially, the 5795-5815 MHz, 63-64 GHz and 74-77 GHz bands, are used notably for vehicle-route communications, in particular for recognition of the vehicles and authentication of payment when the vehicles pass a remote toll charging station. These devices in development consist of disposing a casing behind the windscreen, this casing containing the antenna and being connected to a device enabling information to be received and instructions to be transmitted, notably payment instructions. It comprises, for example, a signal processing unit such as a keyboard associated with a screen. This latter device may be integrated into the vehicle dashboard, while in contrast the casing containing the antenna remains visible because it must be held at an orientation, defined by the transmitter, which enables the signal to be received while passing in front of this transmitter.
Another disadvantage associated with this device may be bad reception of the signal, or indeed impossibility of reception in the case where the windscreen possesses a film based upon a metallic oxide such as a reflective film. The signal is then in effect at least partly attenuated.
SUMMARY OF THE INVENTION
The present invention alleviates the disadvantages listed by proposing a new transmission and reception system of an ultra high frequency signal.
The problems presented by the use of such an antenna are resolved by the present invention, in which an antenna pane, notably for automobiles, is comprised of at least one sheet of rigid material comprising a surface antenna composed of a microstrip separated from an earth (ground) plane by a dielectric.
In one form of embodiment of the pane, this pane is a laminated pane constituted of at least one glass sheet and at least one film of plastic material. It may be, for example, an asymmetric type pane such as that described in Patent Application EP-A-132 198. Preferably, the laminated pane is composed of at least two glass sheets separated by an intermediate layer, notably of polyvinyl butyral, and the antenna is advantageously integrated between the two glass sheets.
The integration of the surface antenna into the pane thus make it possible to have the device not within the passenger compartment of the vehicle.
This realization also allows the antenna to hug the form of the pane closely and thus to avoid possible risks of bad reception.
Furthermore, the antenna inserted into the pane is protected from any degradation due to external influences.
Moreover, its position is fixedly defined and cannot be modified. Thus, the position of the transmitter being known, for example that of a toll station, the characteristics and position of the antenna in the pane are defined and the antenna cannot again be perturbed.
Another advantage of the system according to this invention is that the presence of a reflective film on one of the faces of the glass sheet intended to be towards the passenger compartment of the vehicle, which led to a risk of attenuating the signal received by an antenna situated in the compartment, no longer presents any disadvantage provided that it is disposed between the antenna and the passenger compartment. In addition, it can contribute to protecting the passengers against radiation from the antenna.
Also, according to one preferred form of the invention, the film deposited on one of the faces of the inner glass sheet, that is the sheet nearest the passenger compartment, can be used as an earth plane for the surface antenna.
Moreover, depending upon which face it is that the reflective coating is deposited, the glass sheet may, if desired, fulfill the function of a dielectric.
In a first variant, the surface antenna is disposed between an intermediate film formed between two glass sheets and one of the glass sheets.
A second variant according to this invention consists of placing the microstrip in contact with the glass sheet which is towards the outside of the vehicle, placing the earth plane in contact with the glass sheet towards the inside of the vehicle, and of using the intermediate sheet as the dielectric.
Another disadvantage of the known antennas concerns the cable carrying the signal received. In fact, as soon as this cable exceeds a given length, it may itself form an antenna and the signal that it receives perturbs the signal which it carries. Moreover, if its length is not exactly controlled, the phase at the end of the cable is also not controlled. Finally, ultra high frequencies have very high loss rates and the corrections are difficult to carry out. A solution according to this invention consists of using a cable of the “flat coaxial” type.
According to one preferred solution of the invention, the antenna is associated with an electronic chip enabling the signal received to be demodulated and a conductor wire conducting the demodulated signal to the outside of the pane. This second signal has a much lower frequency, which resolves the aforementioned problems.
The incorporation of a chip into the pane for this application is all the more advantageous since it can also serve for processing the signal received, or indeed for other applications. It may, for example, serve for the construction of demisting sensors, for the construction of devices enabling a vehicle to be found and identified, for example after a theft, or for the construction of any type of sensor. The person skilled in the art will be able to define and construct a chip enabling the various functions chosen to be simultaneously obtained.
With regard to the incorporation of the electronic chip, it is preferably deposited on an integration support by the “flip-chip” technique. Moreover, the electronic chip has dimensions allowing it to be inserted into a laminated pane. Its surface area is advantageously between 1 and 2 mm
2
and its thickness less than 150 microns.
Moreover, in order to withstand the conditions linked with the manufacturing conditions for a laminated pane, the electronic chip advantageously is resistant to temperatures between −70° C. and 160° C. and to pressures of at least 3 bars and preferably at least 10 bars.
The antenna has a relatively large area, which it is preferable to conceal. To achieve this, the antenna optionally in association with a chip may be deposited in a zone of the pane possessing an enamel on the outer face of the glass sheet towards the vehicle interior. This may be, notably, in the case of a windscreen or lateral window of the vehicle, the peripheral enamel strip enabling, in particular, the bonding of the antenna to the vehicle to be concealed.
The invention is also directed to a process for the production of these panes and, more particularly, to laminated panes comprising two glass sheets, and one intermediate film and a surface antenna placed between the two glass sheets.
The incorporation of such an antenna within a pane is no
Letemps Bernard
Potin Marc
Saint -Gobain Vitrage International
Wimer Michael C.
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