Estimation of the Realistic Ground Effect in Free-Space Automotive Measurements

Testing of automotive antennas are commonly performed in large Spherical Near Field (SNF) ranges able to host the entire vehicle to test the effect of the antenna coupling with the structure. The impact of a realistic ground, such as asphalts or soil, on the radiation performance of the vehicle mounted antennas is often a desired information. As long as the free-space response of the vehicle is available, such information can be obtained with fairly good accuracy considering post-processing techniques based on the Image Theory (IT). Automotive systems with absorber material on the floor are thus ideal for estimating such effects because the free-space signature of the vehicle is directly measured and because the radiation pattern is usually available on more than just a hemisphere.

In this paper an IT-based technique which allows for the estimation of a realistic ground is proposed and validated with simulations where the measurement setup of a typical multi-probe free-space automotive system is emulated. The impact of the truncation of the scanning area is analyzed in detail showing how advanced post-processing techniques can be involved to mitigate the truncation errors and thus obtain a better estimation of the realistic ground effect.