Improved approach using symmetric microstrip sensor for accurate measurement of complex permittivity

A novel symmetrical planar sensor based on splitter/combiner microstrip sections with a pair of interdigital capacitors (IDCs) and 2 complementary split ring resonators (CSRRs) structure is presented. A high sensitivity area to the dielectric property of surrounding materials has been established by locating IDC unit on the top-plane while a rectangular CSRR structure etched out on the ground plane. The symmetrical circuit makes the sensitivity further improved to the introduction of sample to be tested because of the destruction of the symmetry. The complex permittivity of the dielectric samples has been evaluated from the actual experimental scattering parameters by using back propagation neural network techniques. The proposed methodology is validated by fabricating the sensor on Rogers5880 substrate and testing various standard dielectric samples viz. PVC, Glass epoxy, FR4, and Glass in C-band. The measured complex permittivity of the test specimens is found to be in close agreement with their values available in literature with maximum error of <5%.