A novel dual-band bandpass filter using stepped impedance resonators with transmission zeros

novel dual-band bandpass filter using stepped impedonce resonator is proposed in this letter. New coupling structures are illustrated to replace the normal counterparts, the circuit size is reduced about 40% compared with the conventional BPF with the same specifications, while the new structure can generate two transmission zeros in the insertion loss response, to validate the design and analysis, two dual-band bandpass filters centered at 2.4 GHz/5.2 GHz and 2.4 GHz/5.7 GHz for WLAN application were fabricated and measured, it is shown that the measured and simulated performance are in good agreement. The bandpass filters achieved insertion loss of less than 2 dB and return loss of greater than 16 db in each band. (c) 2008 Wiley Periodicals, Inc.