Design of dual-mode dual-band bandpass filters with controllable frequencies for multimode wireless communication applications

A flexible approach for designing dual-mode dual-band bandpass filters with controllable passband frequencies is presented. Two dual-mode dual-band bandpass filters are proposed for experimental verification. The first filter, whose two passbands are centered at 3.4 and 5.5GHz with the corresponding fractional bandwidth of 19 and 13%, respectively, is suitable for the applications of worldwide interoperability for microwave access (WiMAX) and wireless local area network. The second filter, whose two passbands are centered at 4 and 7.4GHz with the corresponding fractional bandwidth of 25 and 13%, respectively, is suitable for the downlink of C-band and X-band satellite communication systems. Both filters have been designed, fabricated, and measured. The measured results show good agreements with those of the simulation.