Compact Ultra-Wide-Stopband Microwave Bandpass Filter with Multiple Transmission Zeros by Integrating an L-Shaped Bandpass Filter and a Stepped Impedance Lowpass Filter

Authors

Keywords:

Bandpass filter, microwave filters, multiple transmission zeros, quarter-wavelength resonators, stepped impedance resonators, ultra-wide-stopband

Abstract

A compact ultra-wide-stopband microwave bandpass filter is introduced in this work using an L-shaped quarter-wavelength resonator and stepped impedance resonators. The bandpass filter (BPF-I) is designed at 2.1 GHz (f₀) using an L-shaped quarter-wavelength line. The lowpass filter is developed at 4 GHz using stepped impedance resonators. The introduced ultra-wide-stopband filter is created through integrating the BPF-I and the lowpass filter. Filter size reduction is achieved through the L-shaped quarter-wavelength line, while the ultra-wide-stopband is attained through the stepped impedance resonators. The mathematical analysis of the introduced ultra-wide-stopband bandpass filter is conducted through the extraction of ABCD and S-parameters. The lumped elements equivalent circuits are realized for the introduced filter, and their S-parameters are plotted. The introduced filter is fabricated on an FR4 substrate, and its S-parameters are measured. The comparison of mathematical analysis, EM simulated, circuit simulated, and measured results, showing good agreement. Measurements show a 140.4% fractional bandwidth (FBW), better than 20 dB return loss, higher than 28 dB rejection up to 30 GHz (14.3f₀) in the out-of-band with many transmission zeros, and 0.8 dB insertion loss. 0.23λg x 0.37λg is the overall dimension of the introduced filter.

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Author Biographies

Ramkumar S, Kumaraguru College of Technology, Coimbatore

Ramkumar S received his B.E. (2012) and M.E. (2014) in Electronics and Communication Engineering from Anna University, Chennai, and completed his Ph.D. in 2023 from NIT Puducherry. He has worked as a Research Scientist at SAMEER, Ministry of Electronics and IT, Government of India. His research focuses on wireless communication, microwave filters, reconfigurable filters, filter-integrated antennas, RF energy harvesting, and UWB filters. Additionally, he holds an M.A. in Yoga for Human Excellence from Tamil University, Thanjavur.

Anitha M, National Institute of Technology, Puducherry

Anitha M (Student Member, IEEE) received her B.E. in Electronics and Communication Engineering (2016) and M.E. in Applied Electronics (2018) from Anna University, Chennai. She is currently pursuing her Ph.D. at NIT Puducherry, focusing on satellite communication, air pollution studies, and the prediction of aerosol parameters using machine learning and deep learning.

Boopathi Rani R, National Institute of Technology, Puducherry

Boopathi Rani R (Senior Member, IEEE) holds a B.E. in Electronics and Communication Engineering from Bharathidasan University and an M.E. in Communication Systems from Anna University, where she secured University First Rank. She earned her Ph.D. in antennas from NIT Puducherry and is currently an Assistant Professor at NIT Puducherry, with over a decade of academic experience and 60+ research publications. She has received several awards, including the Best Teacher Award (2007) and ISTE's Best Women Engineering College Teacher (2010). She is a Fellow of IETE, ATMS, and a member of ISTE and SEMCE(I).

Muthuramya C, National Institute of Technology, Puducherry

Muthuramya C received her B.E. in Electronics and Communication Engineering (2009) and M.E. (2011) from Anna University, and earned her Ph.D. in antennas from NIT Puducherry (2022). She served as an Assistant Professor at SCAD College of Engineering and Technology, Tirunelveli, from 2012 to 2019, with 11 national and international research publications. Her research interests include wireless communication, miniaturized antennas, fractal antennas, UWB antennas, and super-wideband antennas.

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Published

2025-04-17

How to Cite

S, R., M, A. ., R, B. R. ., & C, M. . (2025). Compact Ultra-Wide-Stopband Microwave Bandpass Filter with Multiple Transmission Zeros by Integrating an L-Shaped Bandpass Filter and a Stepped Impedance Lowpass Filter. IEEE Latin America Transactions, 23(5), 437–443. Retrieved from https://latamt.ieeer9.org/index.php/transactions/article/view/9327

Issue

Vol. 23 No. 5 (2025): Ordinary Issue

Section

Electronics