Experimental Investigation of Different Floor Materials in Automotive Near Field Antenna Testing

In this paper we present the results from scaled automotive spherical near field measurements of a vehicle model conducted on absorbing and conducive floors. The purpose of the study is to compare accuracies of the different floor scenarios in the 84-1500 MHz frequency range. Two different scaled absorbers are considered to emulate full scale 48-inch and 18-inch absorbers. The larger ones ensure good absorption down to 70-80 MHz but are expensive and difficult to handle, leading to longer setup time. It is thus interesting to verify the level of accuracy that can be reached by using the smaller 18-inch absorbers. To cope with the expected performance degradation at low frequencies, measurements with the vehicle in a configuration raised from the floor, combined with a spatial filtering technique, are also performed. The analysis is carried out in the StarLab multiprobe system, considered a 12-time down-scaled version of typical full-size multiprobe automotive systems. Measurement results relevant to three antenna positions on the car body are shown estimating the measurement uncertainties for the peak gain and the Upper Hemisphere Radiated Power (UHRP).