Multiple FM window antenna system for scanning diversity with an integrated processor

Modern active AM/FM window antennas and FM-antenna-diversity systems used for cars are described, and a novel type of window antenna is presented. For the antenna diversity system two main problems had to be solved. First, an extremely fast working criterion for FM distortions (noise, multipath distortion, equal channel, adjacent channel, and intermodulation distortion) had to be found. The time required for distortion detection in the realized system is only 25 μs. In consequence, no audible distortion occurs before the next antenna is switched on. Second, multiantenna systems adequate for modern cars had to be developed. For increased FM performance quality multiantenna diversity systems are used. One of the systems has been implemented in a production by Philips, Fuba, and BMW. It consists of a diversity processor and three narrow-spaced active window antenna arranged in the rear window of BMW type seven and type five cars