Communications: radio wave antennas – Antennas – With vehicle
Reexamination Certificate
1993-11-05
2001-03-06
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
With vehicle
C343S713000
Reexamination Certificate
active
06198447
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a pane antenna for automobiles, in which an antenna conductor is disposed on the surface of or inside an automobile glass pane. The antenna feed point is connected to the central conductor of a coaxial cable and is disposed in the vicinity of a conductive area located in the edge region of the glass pane and connected to the sheath of the coaxial cable.
2. Description of the Related Art
Antenna structures of this type are suitable as signal transmission antennas for radio communication, especially as antennas for digital radio telephone communication. For maximum transmission efficiency, such antennas must be precisely tuned. They require, for this purpose, a defined reference plane to which all electrical parameters are referred. As the reference plane, therefore, a strip-shaped, electrically conducting coating is disposed directly on the edge region of the glass pane.
An antenna structure of this type is known from WO 88/09569. In this known antenna, which is intended for use as a radio antenna, preferably for the frequency range from 890 to 960 MHz, the antenna conductor consists of a rectilinear conductor having a free end which projects from the edge of the glass pane into the viewing field of the glass pane. The antenna conductor having a conductive area and acting as a reference plane can be printed and baked onto the surface of the glass pane facing towards the interior of the vehicle, like heating conductors for heating panes.
The resonance frequency of this known antenna structure exhibits a certain dependence upon the materials of the glass pane and upon the geometrical tolerances necessary for installation of the glass pane. With these known antennas, therefore, it is still necessary to tune them again after installation if they are to possess an optimum efficiency.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a pane antenna of the initially named type, in which the dependence of the resonance frequency upon the materials used and upon the geometric and mechanical tolerances of the glass pane and of the window frame of the automobile body is further reduced.
According to the invention, this object is achieved by an antenna conductor having the form of a loop and connected at an end to a conductive area on the glass pane.
The antenna conductor of the antenna structure according to the invention is therefore formed as a folded unipole, one end of which is directly connected to a conductive area forming the reference potential. The antenna structure of this invention is substantially less sensitive to installation tolerance because, as a result of its direct connection to the conductive area, it is unambiguously earthed. It furthermore has the advantage that as a result of the ability to vary the width of the loop, it exhibits an additional degree of freedom of an impedance adaptation via the width of the loop.
REFERENCES:
patent: 3599214 (1971-08-01), Altmayer
patent: 3971030 (1976-07-01), Sauer
patent: 5220336 (1993-06-01), Hirotsu et al.
patent: 5255002 (1993-10-01), Day
patent: 5285210 (1994-02-01), Sato et al.
patent: 5293174 (1994-03-01), Kropielnicki et al.
Roberts, Input Impedance of a Folded Dipole, RCA Review, Jun. 1947, pp. 289-300.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Saint-Gobain Vitrage International
Wimer Michael C.
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