Design of a Compact Lowpass Filter with an Ultra-wide Stopband using Triangular Resonators

This research presents a compact Lowpass Filter (LPF) that employs triangular-shaped resonators to achieve an ultra-wide stopband and sharp response in the transmission band. An accurate LC equivalent model is computed for the basic resonator of this design. The proposed LPF features a -3 dB cut-off frequency of 2.2 GHz. Moreover, it provides an ultra-wide stopband extending from 2.9 GHz to 50 GHz, with attenuation levels above 20 dB. The compact dimensions of the LPF are 25.7 mm by 12.1 mm, which corresponds to 0.25 λg by 0.12 λ
g
, where λ
g
is the guided wavelength at 2.2 GHz. The proposed design employs the Rogers RT/duroid 5880 substrate, characterized by a 20 mil thickness and a relative dielectric constant of 2.2. The performance of the designed LPF is compared with several advanced filters to demonstrate its advantages. In upcoming studies, this LPF could be integrated into modern microwave communication systems to effectively suppress unwanted harmonics.