Dual-Band Bandpass Filter Using Stepped Impedance Resonator with Analytical Tapped-Line Feeding

This paper proposes the design of a dual-band bandpass filter (DBPF) with an analytical tapped-line feeding using parallel-coupled stepped impedance resonators (SIRs). In SIRs, the fundamental frequency and higher order harmonics can be easily tuned. The proposed DBPF is applied for new mathematical design method for the SIR tapped-line schemes. In order to determine the tapped-line feeding position, J-inverter of the input resonator can be represented by its equivalent circuit using an input admittance. Also, the dual-frequency transformer is used for input matching. To validate the design and analysis, a 3rd order Chebyshev prototype of the DBPF is fabricated and characterized. The SIR DBPF shows a good simulation performance which is in good agreement with measurement results for dual-band wireless LAN applications at 2.4 and 5.2 GHz.