Application of the translated-SWE algorithm for the characterization of antennas installed on cars using a minimum number of samples

Automotive antenna measurements are increasingly demanding. Modern cars are equipped with a large number of integrated antennas, spanning a wide frequency range for a large number of applications. Integrated antennas are strongly coupled with the structure, final testing are thus performed on the vehicle to accurately determine the performance. The physical and electrical size of typical cars, impose different measurement challenges while performing radiated testing in automotive Spherical Near Field (SNF) ranges. At higher frequencies, the coupling between antenna and vehicle is often limited to the near vicinity of the antenna. It is therefore customary to position the vehicle in the range such that the measurement coordinate system is centered on the antenna. The sampling requirement, to represent the antenna and nearby environment, can be reduced while maintaining acceptable accuracy. In many cases, such desirable arrangement becomes impractical, either due to a high number of antennas to be tested in different positions or due to size of the range. The Translated Spherical Wave Expansion (Translated-SWE) has recently been introduced as an advanced post-processing tool to place the local coordinate system in any position within the measurement range [1-2]. This eliminate the necessity to move the vehicle during testing. In this paper, the Translated-SWE is applied to typical automotive measurements scenarios of antennas in displaced positions on vehicles. Sampling guidelines for full vehicle testing using this method are presented for the first time. Measurement accuracy is investigated experimentally on a 1:12 scaled vehicle with integrated antenna in a standard multi-probe system.