Ground plane effects on the performance of SDARS antennas

Almost since the announcement of satellite digital audio radio services (SDARS), there has been a discussion about the challenging performance requirements for automotive antennas to receive these services. Regarding vehicle design, packaging and integration aspects, "non perfect" antenna mounting locations are playing a decisive role for the practical application of SDARS antennas on a car. The technically optimum antenna mounting location for these satellite based services, the center of the roof, is very often not available because of other conflicting vehicle design parameters and the existence of other components, which make cars enjoyable, e.g., a sliding roof. This paper focuses on the characterization of an SDARS antenna, mounted on different ground planes to show basic ground plane influences corresponding to a wide variety of car metal body shapes serving as antenna ground plane configurations. It is shown that the 3-dimensional antenna diagrams vary with respect to the different sizes and shapes of the applied ground plane, even if the same antenna module is used. This investigation helps to understand environmental influences on the performance of SDARS-antennas, if applied to a vehicle (see Kronberger, R. et al., ibid, p.740-3).