Ultra-Wideband Reconfigurable Filter with Electronically-Switchable Bandpass/Bandstop States

A novel multi-functional reconfigurable filter with four ultra-wideband (UWB) operational modes is presented. It consists of a transversal signal-interference filter structure with two controllable electrical paths, as follows: a main path made up of a commutable-open/short-ended quarter-wavelength coupled-line stage, and a secondary path with a selectable transmission line and short-ended stubs. In this manner, by switching these elements ON/OFF through p-in diodes, three bandpass-filter (BPF) and one bandstopfilter (BSF) states can be set. Moreover, the bandwidth for the sharp-rejection BPF states can be discretely controlled through the transmission zeros (TZs) created by the signal-interference effect and the stubs. For practical validation, a 1-GHz UWB microstrip prototype with bandwidths of 79.3%, 98.9% and 111.7% for the BPF modes and of 114.2% for the BSF mode is developed and characterized.