Compact Bandpass-to-Bandstop Reconfigurable Filter With Wide Tuning Range

A compact reconfigurable bandpass-to-bandstop filter with wide tuning range is presented. The bandpass-to-bandstop transformation is achieved by a p-i-n diode. In the bandstop mode, the two-pole bandstop response is obtained by introducing the inductive coupling between the two resonators of the notch filter. In the bandpass mode, the center frequency and an external quality factor are controlled by two pairs of varactors. A pair of transmission zeros is generated by two transmission paths, which improves the selectivity. The fabricated filter demonstrates a wide frequency tuning range with a miniaturized circuit size of 0.16λg×0.11λg. The simulated and experimental results are presented with good agreement.