Design of a tri-section folded SIR filter

This letter reports the design of a suspended substrate stripline bandpass filter with relocatable second pass band using tri-section folded stepped impedance resonators (TFSIRs). Resonance conditions for the TFSIR in terms of impedance ratios have been derived. Location of the second pass band as a function of impedance ratios (of TFSIRs) has been studied in detail. Experimental results of a filter designed at 2.95 GHz with 31% bandwidth have been compared against the simulation results.