A simple electrically small microwave sensor based on complementary asymmetric single split resonator for dielectric characterization of solids and liquids

The article presents an asymmetric single split resonator (ASSR) unit cell, its resonant properties, and an electrically small microwave sensor employing the complementary asymmetric single split resonator (CASSR) structure with high quality factor (Q) on the FR4 substrate. The structure is compared with the conventional symmetric split ring resonator. The CASSR sensor designed and fabricated on a substrate of dielectric constant 4.4 and a thickness 1.6 mm has an electrically small size of 0.127λ0 × 0.127λ0 × 0.007λ0 at 1.27 GHz, which yields ka = 0.56