Large truncated spherical near-field systems with conductive or absorbing floors are typically used in the measurement of the performances of vehicle-installed antennas. The main advantage of conductive floor systems is the ease of accommodation of the vehicle under test, but their performances are affected by the interaction with the reflecting ground floor. Instead, absorbing-based systems emulating free-space conditions minimize the effect of the interaction with the floor, but generally require longer setup times, especially at lower frequencies (70–400 MHz), where bulky absorbers are typically used to improve reflectivity levels. Considering scaled measurements of a vehicle model, the performances of these two typical implementations are analyzed in the 84–1500 MHz range and compared to free-space measurements. Absorbers with different dimensions and reflectivity have been installed in the scaled measurement setup, and measured data have been investigated with proper post-processing to verify the applicability to realistic systems. Figures of merit of interest for automotive applications, like gain and partial radiated powers, have been compared to free-space to evaluate the impact of different scenarios.

具有导电或吸收地板的大型截短球形近场系统通常用于测量车载天线的性能。导电地板系统的主要优点是易于容纳被测车辆，但它们的性能受到与反射底层相互作用的影响。相反，模拟自由空间条件的基于吸收的系统可最大限度地减少与地板相互作用的影响，但通常需要更长的设置时间，特别是在低频（70-400 MHz）下，通常使用笨重的吸收器来提高反射率水平。考虑到车辆模型的缩放测量，这两种典型实现的性能在 84-1500 MHz 范围内进行了分析，并与自由空间测量进行了比较。不同尺寸和反射率的吸收器已安装在比例测量装置中，测量数据已通过适当的后处理进行研究，以验证对实际系统的适用性。已将汽车应用感兴趣的品质因数（如增益和部分辐射功率）与自由空间进行比较，以评估不同场景的影响。