Discussion and analysis of dumbbell defect‐ground‐structure (Db‐dgs) resonators for sensing applications from a circuit theory perspective

Abstract

Microstrip transmission lines loaded with dumbbell defect‐ground‐structure (DB‐DGS) resonators transversally oriented have been exhaustively used in microwave circuits and sensors. Typically, these structures have been modelled by means of a parallel LC resonant tank series connected to the host line. However, the inductance and capacitance of such model do not have a physical meaning, since this model is inferred by transformation of a more realistic model, where the DB‐DGS resonator, described by means of a resonant tank with inductance and capacitance related to the geometry of the DB‐DGS, is magnetically coupled to the host line. From parameter extraction, the circuit parameters of both models are obtained by considering the DB‐DGS covered with semi-infinite materials with different dielectric constant. The extracted parameters are coherent and re-veal that the general assumption of considering the simple LC resonant tank series‐connected to the line to describe the DB‐DGS‐loaded line is reasonable with some caution. The implications on the sensitivity, when the structure is devoted to operating as a permittivity sensor, are discussed.