Investigation of penetration ability of UWB antennas in near-field sensing applications

Characterization of antennas in far-field applications, both in Line-Of-Sight (LOS) applications (such as in radar systems, point-to-point communications, satellite communications, radio telescopes, etc.) and multipath environment applications (such as mobile communications, indoor communications and indoor geolocations, etc.), is well defined and can be evaluated by well-developed measurement techniques. However, it is still not established how to characterize antennas in near-field sensing applications, where most of the characteristics of antenna in far-field applications are not valid anymore. In this paper, we investigate the characteristics of antennas in near-field sensing applications. The penetration ability, both in time-domain and in frequency-domain is introduced and evaluated. Three UWB antennas, with both simulated and measured results are presented here to demonstrate and evaluate the penetration ability, and the difference from the far-field characteristics, such as the directivity. It is concluded that the higher directivity in far-field does not guarantee a deeper penetration in near-field.