Compact second-order bandstop filter based on dual-mode complementary split-ring resonator

Abstract

A compact dual-mode bandstop filter is presented in this letter. From an equivalent circuit viewpoint, a second-order response is obtained by designing a two-pole notch filter with inductive coupling. This equivalent circuit is then implemented by using a dual-mode complementary split-ring resonator. The proposed bandstop filter prototype has dimensions of 0.1g 0.18g, where {g} defines the guided-wave wavelength. An experimental validation at the center frequency 0 of 2 GHz shows that the proposed filter can extend the harmonic-free upper passband up to 4.20.