A Novel Microstrip Filter Using Three-Mode Stepped Impedance Resonator (TSIR)

A novel microstrip filter using three-mode stepped impedance resonator (TSIR) is presented, with its coupling scheme given so as to accurately predict its desired performance. A T-type open stub is introduced into the design of a miniaturized TSIR. It is shown that the developed filter exhibits quasi-elliptic characteristics with sharp skirt and wide stopband. Good agreements are obtained between its measured and simulated S-parameters.