Windowpane antenna combined with a resisting heating area

Details Windowpane antenna combined with a resisting heating area Windowpane antenna combined with a resisting heating area

1999-11-24

2001-02-06

Le, Hoanganh (Department: 2821)

Communications: radio wave antennas

Antennas

With ice clearer or preventer

C343S713000

Reexamination Certificate

active

06184837

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an antenna disposed on a windowpane of a motor vehicle having an electrically conductive motor vehicle body. The windowpane has a substantially rectangular or trapezoidal heating field that is provided on each side with a bus-bar and has bus-bar connections for feeding heating current on both sides. A heating direct current source is connected to the heating field and is electrically connected to the electrically conductive body of the motor vehicle. The current is fed on each side via an inductively high-resistance current feed network which is installed within proximity of the side edges of the windshield. The heating field is largely high-frequency insulated against the body of the motor vehicle with the help of current feed networks due to their high impedance so that the heating field can conduct high-frequency voltage, that is insulated from the body of the motor vehicle.
2. Description of the Prior Art
A heating field inductively connected in such a way can thus be designed as an antenna with the help of the current feed networks, as shown, for example in FIG. 1 of German Patent DE 36 18 452. The high-frequency coupling to a heating field conducting the high-frequency voltage, to form the antenna, can be accomplished, for example, by a connection to a bus-bar of the heating field.
It is found in automobile construction that interference signals frequently caused by the electronic noise of the automobile are coupled in via the longer current feed lines connected to the bus-bars without any HF-effective filter means. These interference signals disturb the reception in undesirable ways. The advantage offered by the current feed networks installed on the two sides near the bus-bar lies in the possibility of a high-frequency connection of the heating current feeds to the auto body on each side of the respective feed network, facing away from the heating field, without requiring the current to be conducted by longer lines on both sides of the heating field.
Furthermore, high-frequency impedance conditions can be defined on the bus bars. These conditions are not dependent upon the way in which the heating current lines are configured. However, the problems connected with this arrangement are in providing a inductance value for heating currents, with intensities of up to 30 A, particularly within the range of AM radio transmission. The required inductance cannot be realized in the conventional way with small antennas and with light-weight feed networks. The invention is based upon designing feed networks of high inductance that are constructed as small as possible. Also, at low frequencies, the feed networks should have efficient RF insulation, and have adequately low high-frequency losses and filament wattage losses.
SUMMARY OF THE INVENTION
The invention relates to an antenna disposed on a windshield of a motor vehicle having an electrically conductive body. The windshield antenna comprises a direct current heating source electrically connected to the motor vehicle body. Disposed on the windshield of the car is at least one heating field having a bus-bar disposed on one side of each heating field. Connected to the bus-bar at a connection point is a network for feeding heating current to the bus-bar. The network is installed adjacent to the windowpane and comprises at least one magnetic core. Mounted on the magnetic core is a primary winding which has a sufficient number of turns to transfer the high-frequency, high impedance connection of the heating field to the antenna. In addition, there is also a field compensation winding, mounted on the one magnetic core, and connected to a compensating current source so that this connection has no substantial effect in reducing the inductive high-impedance of this feed network.
In this case, the field compensation winding receives a flow of direct current so that the magnetic fields, resulting from the number of turns, their winding direction and the primary winding receiving the flow of heating current, act in an opposite direction relative to one another in the magnetic core. In addition, the magnetic fields are compensated for in the magnetic core, so that there is no interfering saturation effect, so that the antenna is formed either by the heating field itself or by a wire-shaped or flat conductor on the windowpane adjacent to the heating field.


REFERENCES:
patent: 4914446 (1990-04-01), Lindenmeier
patent: 5239302 (1993-08-01), Maeda et al.
patent: 5933119 (1999-08-01), Fujii et al.
patent: 5959587 (1999-09-01), McHenry et al.
patent: 6072435 (2000-06-01), Terashima et al.

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