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. Froman 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 0.1 lambda(g) x 0.18 lambda(g), where lambda(g) defines the guided-wave wavelength. An experimental validation at the center frequency f(0) of 2 GHz shows that the proposed filter can extend the harmonic-free upper passband up to 4.2 f(0).