Ultra-broadband car antennas for communications and navigation applications

This paper presents two different ultra-broadband antenna designs for mobile communications and navigation, which can be integrated conformally into the bodywork of a car. Both antennas are based on the frequency-independent spiral structure. One antenna, which is intended to be integrated into the car's window, is an externally fed spiral antenna in order to obtain a flat structure. The second spiral antenna consists of four arms which are fed by a coplanar waveguide transmission line. This enables the excitation of two different radiation patterns for terrestrial and satellite services. With a low cost feed network both radiation modes can be excited simultaneously and independently of each other. Measurement results are presented within and beyond the specifications.