Fast, Low-Invasive Visualization of EM-Very-Near-Field Distributions Around Wireless Communication/Sensing Devices: From Anechoic Chamber to Microscope

While fast visualization of Electromagnetic (EM) field distribution is satisfactorily obtained by numerical modelling, it still constitutes a key challenge for measurements in a wide spectrum of demanding applications spreading from the early design and prototyping of antenna modules to final online fabrication and compliance testing of mass-produced connected devices. But recently, the rapidity of measurement has been improved thanks to several modalities exploiting either various interaction mechanisms between EM waves with adequate sensitive materials or the combination of standard Near-Field (NF) measurements with optimized sampling strategies and advanced wavefront post-processing techniques to retrieve Very-Near-Field (VNF) distributions. The aim of this paper is to provide an overview of these modalities and a global comparison of their potential in terms of rapidity, sensitivity, invasiveness and spatial resolution.