Modified Annular Ring Antenna for GPS and SDARS Automotive Applications

Integrated Global Positioning System (GPS) and Satellite Digital Audio Radio (SDARS) antenna is proposed for automotive use. The GPS antenna is formed by modifying an annular ring antenna operating at
${\rm TM}_{12}$
mode, and the SDARS antenna is placed at the ring center using a slot-loaded degenerate mode
${\rm TM}_{11}$
square patch. The GPS antenna operates at 1575.4 MHz with right-hand circular polarization, and the SDARS antenna operates from 2320 to 2345 MHz with left-hand circular polarization. The antenna is also placed on an automotive model, and simulations with the vehicle are performed. Simulations and measurements of the antenna exhibit good performance for automotive use.