AM upper/FM defogger grid active backlite antenna

摘要

A vehicle backlite antenna system that includes separate FM antenna/defogger elements and AM antenna elements. The antenna system includes various FM impedance matching elements that provide FM impedance matching between the defogger elements or the antenna elements and an RF amplifier. These impedance matching elements include a shorting bar connecting a plurality of the AM antenna elements that is positioned between end bars of an AM antenna grid. The shorting bar can be a certain distance from the AM feedpoint to provide impedance matching for the low end of the FM frequency band. Additionally, a floating impedance matching element is connected to the FM antenna/defogger elements between the defogger elements and the AM antenna grid. The floating element can have a certain length to provide impedance matching for the upper end of the FM band. Extended ground planes can also be provided it the upper corners of the window between the vehicle body and the AM antenna elements to control the gap between the AM antenna grid and the vehicle body to control the electrical coupling between the AM antenna grid and the vehicle body. Also, the FM antenna/defogger elements can include two vertical shorting elements between defogger grid bus bars.