Lumped-Element Absorptive Bandstop Filter based on Dual Composite Right/Left Handed Transmission Line

This paper presents a design of an absorptive bandstop filter based on dual composite right/left-handed transmission line (D-CRLH TL), which exhibits infinite attenuation and good return loss at the center frequency using low-Q small-size resonators. Compared with the conventional absorptive filter structures, this design is smaller in size because the resonators are lumped elements and there is no physically long transmission line. Meanwhile, accurate mutual inductance between two resonators is not required. For verification of the design, a lumped-element bandstop filter has been designed and measured. Simulation and measurement showed good agreement.