A wide stopband CPW low pass filter using quarter wavelength stepped impedance resonators

A novel wide stopband coplanar waveguide (CPW) low pass filter (LPF) using quarter wavelength stepped impedance resonators (SIR) is presented. The bandstop characteristics of the quarter wavelength short circuited stubs SIR are demonstrated. By cascading three tapered quarter wavelength short circuited stubs SIR and a CPW spurline resonator, the fabricated low pass filter has sharp rejection with cutoff frequency of 3.5 GHz, and deep attenuation from 3.7 GHz to 11 GHz lower than -24 dB. Good agreement between simulated and measured results is demonstrated.