Elliptic high-pass filters with stepped impedance resonators in coplanar waveguide technology

Ultra compact elliptic-function high-pass filters (HPFs) in coplanar waveguide (CPW) technology are presented.The required shunt-connected series resonators of the elliptic-function response are implemented by means of stepped impedance resonators (SIRs), etched in the back substrate side. The accurate circuit model of the filter, including parasitic effects, is presented and used for design purposes. An order-3 prototype HPF with 0.1-dB ripple and 3-GHz cutoff frequency is designed and fabricated as proof-of-concept demonstrator. The measured filter response is in good agreement with the ideal elliptic-function in the region of interest. Filter dimensions are as small as 0.092Δ g × 0.185Δ g, Δ g being the guided wavelength at the cutoff frequency. © 2012 Wiley Periodicals, Inc.