Coplanar waveguide periodic structures with resonant elements and their application in microwave filters

Coplanar waveguide (CPW) periodic structures with resonant elements on the ground plane have been investigated for lowpass and bandstop filter applications. The resonator is constructed by etching out radial shapes on the ground plane. The use of resonant elements allows larger attenuation in the stop band to be obtained with less number of periodic structures as compared with conventional photonic bandgap (PBG) structures. A theoretical study of this type of periodic structure has revealed some useful information for designing filters. Two filters of this type, one for lowpass application and the other for bandstop application have been designed, fabricated and tested. The results are presented.