Reactively Loaded Microstrip Line Based 1-D Periodic Structure with All-Pass, Low Pass and Stopband Filter Characteristics

A 1-D periodic structure having two shorted patches bearing dissimilar dimensions, in a unit cell, have been investigated for its application as a reconfigurable filter. To demonstrate the working mechanism, reactive loading to microstrip line is changed by periodically altering the patch connection to ground through presence/absence of shorting vias. Six filter structures with same unit cell dimensions and different switching patterns have been fabricated that represent different configurations of the filter. The proposed structure behaves as an all-pass filter in one state, and as a low pass filter and bandstop filter in other states with tunable cutoff frequencies.