Application of UWB Arrays for Material Identification of Multilayer Media in Metallic Tanks

In this paper, a compact eight-element antenna array is designed for ultra-wide band (UWB) pulsed radar in highly reflective metallic environments, such as storage and transport tankers. The impact of the sidewalls in metallic tanks is to increase noise and create spurious signals due to sidewall reflection that limits accuracy and causes liquid level and material property measurement errors. The designed Vivaldi antenna and array are characterized in terms of the transient energy patterns and the signal fidelity given in terms of the off-angle signal correlation. Comparison with horn antennas is made. Antenna transient signals are calculated from the frequency-domain data. The 10-dB transient energy pattern beamwidth in the E-plane is improved from 130° to 50° using the eight-element array versus single element. Also, the signal correlation and fidelity for off-broadside angles is greatly reduced. The reflection data from a multilayer of canola oil on metal-backed marble is processed with a calibrated layer-stripping technique for material properties. The transient radiation patterns of the array are compared to that of two horn antennas with similar dimensions. The noise/interference and measurement error is shown to be greatly reduced using an array compared to horn antennas in a realistic tank environment.