Folded Finite-Ground-Width CPW Quarter-Wave Stepped Impedance Resonator Filters

This paper proposes two new types of folded finite-ground-width CPW lambda/4 stepped impedance resonators (SIRs). The newly proposed CPW lambda/4 SIRs are much shorter than the conventional CPW lambda/4 SIR. Comparing to the multifold CPW lambda/4 UIR[1], the proposed resonators show much higher first spurious resonant frequency. Filters implemented with these newly proposed CPW lambda/4 SIRs depict not only a small size but also a high spurious passband frequency. Besides, similar to that of multifold CPW lambda/4 UIR filters, the proposed folded CPW lambda/4 SIR filters can be easily configured as a cascade quadruplet (CQ) or a cascade tri-section (CI) filter. Several filters are implemented to demonstrate the feasibility of the proposed CPW lambda/4 SIRs.