Characterization of A Folded Stepped Impedance Resonator for Miniature Microstrip Bandpass Filter Applications

In this paper we propose a Folded Stepped Impedance Resonator(FSIR) which is effective in realizing extremely compact microstrip bandpass filters. To characterize this new structure we use an FDTD algorithm where all discontinuity effects have been considered. For identical resonant frequencies, the proposed FSIR is found to be approximately 43 percent shorter in total length than conventional half-wavelength microstrip resonators. The accuracy of our FDTD analysis is verified through comparison with results in the open literature, and the effectiveness of the FSIR is also confirmed by experiments with two test resonators we have fabricated.