Dual-Band Uniaxial Dielectric Anisotropy Sensor Using Coupled-Line Resonators

In this paper, a new dual-band sensor to measure uniaxial anisotropy at two frequency bands is proposed. This sensor is composed of two dual-mode resonators separated by a T-shaped structure implemented in microstrip technology. The configuration of vertical and horizontal electric field lines for the two resonance modes allows for the characterization of a uniaxial anisotropic sample placed on top of the sensor. The resonance frequencies of different modes are separated using active S-parameters measured at the input port. They are subsequently used in the space mapping process to extract the dielectric constants of the sample in two directions, parallel and normal to the surface of the sensor, by means of electromagnetic analyses. The sensor is used to extract the dielectric constants of anisotropic FR4, RO4003C, and RO3010 samples at 2.4 and 3.4 GHz. An isotropic PTFE sample is also characterized to verify the reliability of the proposed method. Two single-band sensors are also implemented to measure RO3010 sample and the extracted dielectric constants are compared to those resulted from the proposed dual-band sensor.