Design of a Microstrip Dual-/Quad-band Switchable Bandpass Filter with Dual-band Bandpass Filters

A novel bandpass filter with four switchable configurations is presented in this paper. The proposed filter is composed of two parallel connected dual-band bandpass filters. In particular, each filter has two open stubs and one parallel-coupled line, series connected with the stepped transmission lines and switching diodes. With four switching diodes in the “on” state, the measured central frequencies of quadruple passbands are located at 2.65, 3.36, 4.65, and 5.36 GHz. The result matches well with the theoretical simulation.