A Microstrip Folded Hairpin Resonator Filter for the 2.4 GHz Band

Authors

DOI:

https://doi.org/10.18372/1990-5548.89.21486

Keywords:

folded hairpin resonator, microstrip bandpass filter, microwave filter, finite-element method, FR4 substrate, sensitivity analysis, electromagnetic simulation, industrial, scientific, and medical band

Abstract

A compact fourth-order folded hairpin resonator microstrip bandpass filter is designed, fabricated, and experimentally validated for the 2.4 GHz band on an FR4 substrate. Analytical synthesis, full-wave finite-element simulation, and numerical optimization of the filter structure are performed. It is shown that the degradation of the filter characteristics due to the use of an FR4 substrate is relatively small compared with the simulated results and can be attributed to manufacturing inaccuracies. The measured and simulated S-parameters show satisfactory agreement: the prototype’s center frequency is shifted by about 50 MHz, which is consistent with the sensitivity analysis, while the measured |S11| level within the passband is approximately 10 dB higher than the simulated value. A numerical sensitivity analysis of ±100 μm deviations shows that the coupling gaps affect the return loss (a variaton of 17 – 22 dB) far more strongly than the resonator length does (a variation of 4 dB and a 70 MHz frequency shift). Compared with a conventional hairpin filter of the same specification, the folded topology reduces the transverse filter dimension by approximately 30%.

Author Biography

Igor Trubarov , National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”

Candidate of Science (Engineering)

Associate Professor

Telecommunications Department

Educational and Research Institute of Telecommunication Systems

References

[1] P. Jarry and J. Beneat, Advanced Design Techniques and Realizations of Microwave and RF Filters, 1st ed. Wiley, 2008. https://doi.org/10.1002/9780470294178.

[2] L. Zhu, Microwave bandpass filters for wideband communications. in Wiley series in microwave and optical engineering. Hoboken, N.J: J. Wiley & Sons, 2012. https://doi.org/10.1002/9781118197981.

[3] R. W. Rhea, HF Filter Design and Computer Simulation. Institution of Engineering and Technology, 1994. https://doi.org/10.1049/SBEW010E.

[4] J.-S. Hong, Microstrip filters for RF/microwave applications, 2nd ed. in Wiley series in microwave and optical engineering. Hoboken, N.J: Wiley, 2011. https://doi.org/10.1002/9780470937297.

[5] A. O. Nwajana and E. R. Obi, “Application of Compact Folded-Arms Square Open-Loop Resonator to Bandpass Filter Design,” Micromachines, vol. 14, no. 2, p. 320, Jan. 2023, doi: https://doi.org/10.3390/mi14020320.

[6] T. Sie King, A. T. Ying Ying, and S. Hieng Tiong, “A microstrip diplexer using folded hairpins,” in 2011 IEEE International RF & Microwave Conference, Seremban, Negeri Sembilan, Malaysia: IEEE, Dec. 2011, pp. 226–229. https://doi.org/10.1109/RFM.2011.6168735.

[7] T. K. Das and S. Chatterjee, “Harmonic Suppression by Using T-shaped Spur-Line in a Compact Hairpin-Line Bandpass Filter,” Radioengineering, vol. 30, no. 2, pp. 296–303, Jun. 2021, doi: https://doi.org/10.13164/re.2021.0296.

[8] S. Chatterjee and T. K. Das, “Compact Hairpin-Line Bandpass Filter with Harmonic Suppression by Periodic Grooves,” in 2019 IEEE 19th Mediterranean Microwave Symposium (MMS), Hammamet, Tunisia: IEEE, Oct. 2019, pp. 1–4. https://doi.org/10.1109/MMS48040.2019.9157328.

[9] M. Nedelchev, “Design of microstrip meander-folded hairpin resonator filters,” in 2013 Conference on Microwave Techniques (COMITE), Pardubice: IEEE, Apr. 2013, pp. 69–72. https://doi.org/10.1109/COMITE.2013.6545045.

[10] I. Trubarov, “Design of a Microstrip Filter for 5 GHz Band Using Different Numerical Methods,” in Proceedings of the XIV International Scientific and Technical Conference “Modern Challenges in Telecommunications - 2020,” Kyiv, 2020, pp. 71–73. [Online]. Available: https://conferenc-journal.its.kpi.ua/article/view/200839

[11] S. S. Rao, Engineering optimization: theory and practice, Fifth edition. Hoboken, NJ: Wiley, 2020. https://doi.org/10.1002/9781119454816.

[12] I. Trubarov, “Design of a Hairpin Microstrip Bandpass Filter for the 2.4 GHz Band,” Information and Telecommunication Sciences, no. 1, pp. 92–98, Jun. 2026, https://doi.org/10.20535/2411-2976.12026.92-98.

Downloads

Published

2026-09-18

How to Cite

Trubarov , I. (2026). A Microstrip Folded Hairpin Resonator Filter for the 2.4 GHz Band. Electronics and Control Systems, 3(89), 145–152. https://doi.org/10.18372/1990-5548.89.21486

Issue

Vol. 3 No. 89 (2026)

Section

ELECTRONICS, ELECTRONIC COMMUNICATIONS, INSTRUMENTATION AND RADIO ENGINEERING

License

Copyright (c) 2026 Ігор Володимирович Трубаров

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

The scientific journal “Electronics and control systems” adheres to the principles of Open Access and provides free, immediate, and permanent access to all published materials without financial, technical, or legal barriers for readers.

All articles are published in Open Access under the Creative Commons Attribution 4.0 International (CC BY 4.0) license.

Copyright

Authors who publish their works in the journal “Electronics and control systems”:

  • retain the copyright to their publications;

  • grant the journal the right of first publication of the article;

  • agree to the distribution of their materials under the CC BY 4.0 license;

  • have the right to reuse, archive, and distribute their works (including in institutional and subject repositories), provided that proper reference is made to the original publication in the journal.