Stepped Coplanar line-based Phase Sensor for Defect Detection

This work presents a stepped coplanar topology to measure the phase variation sensing mechanism in the specified frequency region (3.5 GHz-5.5 GHz). Stepping in CPW (Coplanar Waveguide) topology is carried out to ensure $50\Omega$ matching at excitation port and to provide adequate field localization over the sensing region. The central region of the stepped coplanar line is used as a sensing area where MUT (Material Under Test) can be placed for dielectric constant and defect detection. The Efield plots of conventional and proposed topologies are analyzed to show the enhanced field confinement. The performed numerical analysis shows that the proposed sensor produces an improved phase shift in transmission parameter (5°) than that of the conventional CPW (2°) counterpart for identical change in the dielectric constant. Finally, a numerical analysis is performed to appreciate the defect detection attribute of the designed sensor corresponding to the two samples with different profile of air void (defect pattern). It is found that the sensor may produce significant phase shifts corresponding to each sample, including defect-less samples, due to its improved phase sensitivity.