Measuring the radiation patterns of SDARS installed in vehicles

Satellite Digital Audio Radio Systems (SDARS) place stringent requirements on the radiation characteristics of the system antennas. The antenna radiation properties are affected by the location of the antenna on the vehicle and the method used to mount it. Hence it is necessary to measure the radiation characteristics with the system installed in the vehicle. This paper describes an antenna measurement system designed to measure the radiation characteristics of SDARS with the antennas embedded in the windshield glass. Since the windshield glass design is different for each model automobile, it is necessary to verify the performance of the antenna/windshield combination on the prototype vehicles before committing the design to production. A review of the requirements of the SDARS is given, followed by a description of the spherical measurement system designed for the requirement. The completed installation is presented, along with suggestions for future upgrades and improvements.