Wideband Band-Stop X-Band Filter Using Electrically Small Tightly Coupled Resonators

摘要

An electrically small, coupled resonator X-band filter capable of exhibiting a 25% fractional bandwidth band-stop response is presented. Different than the existing designs, the capacitively-loaded open loop resonators of the filter are realized over a 7 $mu$m thin Benzocyclobutene (BCB) layer in order to bring them in close proximity of a microstrip feed line to achieve the desired wideband response. The resonator shape was specifically modified to minimize the width of the filter to 2.5 mm (i.e., $lambda_{{{0}}}/13$) at the center frequency of 9.2 GHz in order to be employed within the gaps of a tightly packed tile antenna array. The filter exhibits a measured band-stop performance with $>25$ dB insertion loss from 8.1 to 9.64 GHz. Within the band-pass regime (${<}7.3$ GHz and ${>}11.2$ GHz), the filter is shown to operate with ${<}1.5$ dB measured insertion loss.