Low Complexity Compact Lowpass Filter Using T-Shaped Resonator Loaded With a Stub

A novel miniaturized microstrip low pass filter (LPF) with a wide stopband and sharp roll-off is presented. The designed filter is developed by realizing a T-shaped structure loaded with a stub as a resonator and open-stubs as suppressor cells to achieve a simple structure for ease of fabrication process. The new filter with a symmetrical structure has a 3 dB cut-off frequency of 2.15 GHz, the transition band is 123 dB/GHz from −3 dB to −40 dB, a stopband with an attenuation level better than −20 dB from 2.4 up to 22.1 GHz with a compact size of
$0.0132 {{\lambda _{g}}^{2}}$
. The insertion loss in the passband is less than 0.3 dB and return loss is lower than −20 dB. The filter is fabricated, and the results show agreement between the simulation and measurement.