SIW cavity based compact RF sensor for testing of dielectrics and composites

A novel SIW cavity based RF sensor is designed and developed for non-destructive testing (NDT) of dielectric and advanced composites at 1.5 GHz using the TE₁₀₁ mode. The proposed sensor is fabricated on low cost FR-4 substrate, and excitation of fabricated sensor is done with 3.5mm SMA connectors. The material testing is performed using the cavity perturbation theory for real part of the permittivity, while the loss tangent is calculated using the numerical curve fitting technique. Several standard dielectrics are tested using the proposed sensor, and the results are compared with their reported values. The designed sensor is compact having more sensitivity in comparison to other SIW sensors reported in the past with error in the real permittivity within 5%.