Wideband Bandpass Filter With Reconfigurable Bandwidth

This letter proposes a novel building block for developing tunable wideband bandpass filters. The proposed circuit block mainly consists of short circuit coupled lines and short circuit stubs with pin diodes as tuning elements. This work aims to demonstrate reconfigurable bandwidth of this type of filter. Two filters are designed and fabricated; one can be switched between a fractional bandwidth (FBW) of 16.3% and 35% at a center frequency of 1.9 GHz, and the other can be switched from a FBW of 27.8% to 37.4% at a center frequency of 1.9 GHz. The insertion loss and return loss in the first filter range from 4.17 dB to 0.4 dB and 27.54 dB to 19.04 dB. The second filter exhibits an insertion loss ranging from 0.73 dB to 0.43 dB and a return loss range from 31.1 dB to 27.7 dB. The tested filters show good agreement with EM simulations.