Planar dual-mode dual-band dual-ring resonator bandpass filter

A dual-ring resonator with a new perturbation scheme is proposed for design of a dual-mode dual-band bandpass filter with two transmission zeros on both sides of each passband. The two center frequencies can be easily determined and design curves for controlling the two passband bandwidths are generated. Two circuits are fabricated and measured. The measurement data show good agreement with predicted responses obtained by EM simulation.