ENG-Sensor: Enhanced open-ended coaxial line sensor for material characterization application

Material characterization using microwave and radio frequencies has diverse applications such as moisture measurement, process control for food processing, and biological tissue measurement [1, 2]. Among the material characterization techniques, near field open-ended coaxial line sensors are widely used since they do not need extensive sample preparation and have a wide operation band. The design of a classical open-ended coaxial line sensor has been investigated in [3] to maximize the sensitivity in a specific range of measured permittivity. Moreover, in [3] it was shown that for a fixed system impedance, the optimization of the classical coaxial line sensor depended on a single parameter α, where α = af, a is the inner radius of the coaxial line and / is the operation frequency. Recently, it was shown that the use of double negative materials and single negative materials enhances the sensitivity of near field probes [4]. In [5], negative materials were used to improve the sensitivity of open-ended coaxial lines for crack detection on aluminum surfaces. In this paper, the sensitivity definition presented in [3] is used to demonstrate the advantage of using an epsilon negative (ENG) layer with a classical open-ended sensor for material characterization applications.