Novel reconfigurable multiple-band quasi-elliptic bandpass filter using defected ground structure

A novel reconfigurable bandpass filter with multiple quasi-elliptic passbands is presented in this paper using defected ground structure and PIN diodes. In contrast to the popular controllability on the center frequency or bandwidth given by conventional reconfigurable bandpass filters, the proposed filter can be controlled to switch between single, dual or triple bandpass characteristics. All these passbands are quasi-elliptic and their center frequencies and bandwidths can be predesigned through a proper selection on the lengths of some particular slotline sections. Two example filters are implemented to verify the effectiveness of the filter configurability. The measurements show very good agreements with simulations including diode model.