Importance

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Abstract

The present invention is a moisture-insensitive system adapted to couple radio frequency energy at a low impedance from a matched two conductor transmission line, through a vehicle windshield and to an antenna in a manner which minimizes stray radio frequency radiation within the passenger compartment of the vehicle. The system includes two pair of conducting plates, one pair mounted on each side of the windshield, each pair opposite the other pair. A coaxial feed line is coupled to the inside pair of plates and a matching circuit is connected across the outside pair of plates. A full-size, unloaded antenna element is connected to the output of the matching circuit. A decoupling device, such as a decoupling sleeve or a RF choke, can be used to minimize RF current flow on the shield conductor of the coaxial feed line. The coaxial cable is coupled directly through the windshield, without an intervening matching network, so that RF energy at a low impedance is coupled to the outside pair of plates. This low impedance minimizes parasitic coupling of the feed system to moisture on the windshield, windshield wipers and other foreign bodies. The elements of the invention cooperate to minimize the level of stray radiation within the passenger compartment of the vehicle and provide, in the illustrated embodiment, a 2.0:1 VSWR bandwidth that extends from 830 to 880 megahertz.

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First Claim