Design and Optimization of a Compact Stepped-Impedance Microstrip Low-Pass Filter with Enhanced Stopband Rejection

This paper presents the design and optimization of a compact stepped-impedance microstrip low-pass filter featuring an extended stopband for improved rejection of unwanted harmonics. The topology employs alternating high- and low-impedance λ/۴ sections to realize a sharp transition skirt and inherent spurious suppression. An equivalent lumped-element circuit model is first derived to guide initial dimensioning. Full-wave electromagnetic simulation in Cadence Spectre is then used to refine the section impedances and inter-section spacings, targeting under ۰.۵ dB insertion loss in the passband (DC–۲ GHz) and better than ۴۰ dB attenuation up to ۸ GHz. To validate robustness, process-voltage-temperature corners and Monte Carlo analyses (۱۰۰ runs, ۳% parameter variation) are performed on the post-layout netlist. Results demonstrate a measured stopband extending from ۲.۵ to ۱۰ GHz with minimum attenuation of ۴۵ dB, while the filter footprint is reduced by ۲۵% compared to conventional stepped-impedance designs. A comparative performance table against state-of-the-art filters highlights improvements in size, insertion loss, and stopband width. The proposed filter is well suited for integration in compact RF front-ends where stringent size and spurious-suppression requirements coexist.

کلیدواژه ها:

microstrip low-pass filter ، stepped-impedance ، stopband rejection ، compact design ، EM simulation