Compact and switchable dual-band bandpass filter with high selectivity and wide stopband

A compact and independently switchable dual-band bandpass filter is presented. To achieve high selectivity response, transmission zeros beside the two passbands are generated due to crossed coupling. On the other hand, the use of quarter-wavelength stepped-impedance resonators can not only miniaturise circuit size but also widen the stopband by arranging the resonant frequencies in a stagger with the same fundamental frequency. The pin diodes are loaded at the end of the resonators as the switching devices to independently control each passband. © The Institution of Engineering and Technology 2013.