UWB antenna array for level and permittivity measurement with calibrated layer stripping

The measurement of liquid level and material identification using ultra-wideband radar is an active area of research. In this paper a compact 8-element antenna array is designed for ultra-wide band (UWB) pulsed radar in highly reflective metallic environments, such as storage and transport tankers. The designed Vivaldi antenna and array are characterized in terms of the transient gain for a 3-10 GHz excitation pulse and the signal fidelity given in terms of the off-angle signal correlation. The 10 dB transient gain beam width in the E-plane is 50° compared to 130° using the 8-element array vs. single element. Additionally, the reflection data with the array is measured in a metallic tank environment and the noise/interference is shown to be greatly reduced compared to single antenna measurement. A calibrated layer stripping method used for material and layer-interface identification is outlined and the accuracy with an array compared to single element is shown. The measurement of a multilayer set-up consisting of canola oil on marble demonstrating the prediction accuracy is given proving the validity of the method.