Sharp Roll-Off Ultra Wide Stopband Compact Microstrip Lowpass Filter Using Square-Shaped Resonator

In this paper, a novel compact microstrip Low-Pass Filter (LPF) with sharp roll-off and ultra-wide stopband with high suppression level is presented. In the proposed filter, square-shaped resonators are used. The cut-off frequency at 3dB is 1.88GHz. The maximum insertion loss of this filter is less than 0.1dB and the return loss is also less than 16dB in the passband. In the proposed structure, the stopband extends from 2.07 to 29.5 GHz at 24dB level of suppression and is considered as an ultra-wide stopband. There is a significant relationship between simulation and fabrication results, which have justified the functionality of the proposed LFP, respectively.