Design of a Miniaturized Flexible Patch Antenna with Shorting-Pin Integration for Enhanced Gain in RFID, ISM, and Wearable Biomedical Applications

Waqas Ali; Nizam- Ud-Din; Muhammad Zahid

Authors

Waqas Ali Department of Electrical Engineering, HITEC University Taxila, Pakistan
Nizam- Ud-Din Department of Biomedical Engineering, HITEC University Taxila, Pakistan
Muhammad Zahid Department of Telecommunication Engineering, University of Engineering and Technology Taxila, Pakistan

Keywords:

RFID Antennas, ISM Band, Patch Antenna, IoT and IoE, Biomedical and Wearable Applications

Abstract

Antennas are integral parts of wireless communication because they can ensure that signals are transmitted and received effectively, encompassing a variety of frequencies, such as those used in IoT and overall RF systems. This paper introduces a miniaturized single-band antenna of 9 × 31.6 × 0.254 mm³ with a specific design for wearable applications, which was made on flexible Rogers RT5880 substrate. Using the CST Microwave Studio 2024 microchip as the design and analysis tool, the proposed antenna consists of a rectangular slot-based radiating structure with a shorting pin and probe feed, which can achieve stable design performances both in the free-space and on-body situation services. Compliant with the wearable safety requirements and operating at a low level specific absorption rate (SAR) less than 1.6 W/kg at the resonant frequency. The antenna has good radiation performance, with a maximum efficiency of 82% and a maximum gain of 4.1 dBi, having a bidirectional radiation pattern in the elevation plane and an omnidirectional radiation pattern in the azimuth plane. The introduction of shorting-pin as a strategic method of reducing the length of resonance allows the approach of substantial reduction in the resonant length without compromising radiation characteristics. Simulation results also provide further confidence scales of stabilizing impedance performance and omnidirectional radiation pattern properties in the target 5.725-5.875 GHz ISM band, which demonstrates the expectation of shorting-pin strategies for the development of small-size, high biocompatibility, and flexible antennas for next-generation wearable, body-area network, and radio frequency identification (RFID) communication systems.

References

“8.4 Billion Connected Things Will be in Use 2017 | Gartner.” Accessed: Dec. 24, 2025. [Online]. Available: https://www.gartner.com/en/newsroom/press-releases/2017-02-07-gartner-says-8-billion-connected-things-will-be-in-use-in-2017-up-31-percent-from-2016

K. V. S. Rao, P. V. Nikitin, and S. F. Lam, “Antenna design for UHF RFID tags: A review and a practical application,” IEEE Trans. Antennas Propag., vol. 53, no. 12, pp. 3870–3876, Dec. 2005, doi: 10.1109/TAP.2005.859919.

C. Sun, Z. Wu, and B. Bai, “A Novel Compact Wideband Patch Antenna for GNSS Application,” IEEE Trans. Antennas Propag., vol. 65, no. 12, pp. 7334–7339, 2017, doi: 10.1109/TAP.2017.2761987.

J. Ren, H. Liu, Y. Zeng, Z. Wang, and S. Fang, “Dual-Band Circularly Polarized Antenna with Wide Axial-Ratio and Gain Beamwidths for High-Precision BDS Applications,” Prog. Electromagn. Res. C, vol. 145, pp. 63–74, 2024, doi: 10.2528/PIERC24052202.

K. Wei et al., “A Dual-Band Rotational Feed Circularly Polarized RFID Reader Antenna Array With Stable Gain,” IEEE Antennas Wirel. Propag. Lett., vol. 24, no. 7, pp. 1620–1624, 2025, doi: 10.1109/LAWP.2025.3543388.

S. Chenaoui, L. Mouffok, S. Hebib, A. Fattouche, D. Allane, and S. Tedjini, “Gain stability improvement of a wideband antenna using an artificial magnetic conductor,” Microw. Opt. Technol. Lett., vol. 65, no. 8, pp. 2267–2277, Aug. 2023, doi: 10.1002/MOP.33673;REQUESTEDJOURNAL:JOURNAL:10982760;WGROUP:STRING:PUBLICATION.

T. Lou, Z. Shen, and X. X. Yang, “Circularly Polarized UWB Antenna Based on a Single-Folded Substrate,” IEEE Antennas Wirel. Propag. Lett., vol. 23, no. 7, pp. 2195–2199, 2024, doi: 10.1109/LAWP.2024.3384979.

X. Liu, Y. Zhu, and W. Xie, “A Miniaturized Wideband Directional Circularly Polarized Antenna Based on Bent Vivaldi Antenna Structure,” IEEE Antennas Wirel. Propag. Lett., vol. 22, no. 2, pp. 298–302, Feb. 2023, doi: 10.1109/LAWP.2022.3209611.

H. Yang et al., “Aperture Reduction Using Downward and Upward Bending Arms for Dual-Polarized Quadruple-Folded-Dipole Antennas,” IEEE Antennas Wirel. Propag. Lett., vol. 22, no. 3, pp. 645–649, Mar. 2023, doi: 10.1109/LAWP.2022.3221468.

P. V. Nikitin and K. V. S. Rao, “Antennas and propagation in UHF RFID systems,” 2008 IEEE Int. Conf. RFID (Frequency Identification), IEEE RFID 2008, pp. 277–288, 2008, doi: 10.1109/RFID.2008.4519368.

G. Marrocco, “The art of UHF RFID antenna design: Impedance-matching and size-reduction techniques,” IEEE Antennas Propag. Mag., vol. 50, no. 1, pp. 66–79, Feb. 2008, doi: 10.1109/MAP.2008.4494504.

“(PDF) UHF RFID antenna architectures and applications.” Accessed: Dec. 24, 2025. [Online]. Available: https://www.researchgate.net/publication/266583117_UHF_RFID_antenna_architectures_and_applications

D. Zhao, Y. Z. Yin, and Y. Yang, “A review of antenna design and measurement for UHF RFID tags,” 2010 9th Int. Symp. Antennas Propag. EM Theory, ISAPE 2010, pp. 349–352, 2010, doi: 10.1109/ISAPE.2010.5696472.

J. Zhang, G. Y. Tian, A. M. J. Marindra, A. I. Sunny, and A. B. Zhao, “A Review of Passive RFID Tag Antenna-Based Sensors and Systems for Structural Health Monitoring Applications,” Sensors 2017, Vol. 17, Page 265, vol. 17, no. 2, p. 265, Jan. 2017, doi: 10.3390/S17020265.

J. Ghalibafan and F. H. Kashani, “A circularly polarized fractal microstrip antenna for RFID applications,” 2009 IEEE Int. Symp. Radio-Frequency Integr. Technol. RFIT 2009, pp. 319–322, 2009, doi: 10.1109/RFIT.2009.5383721.

P. Charoenchue, C. Phongcharoenpanich, K. Phaebua, and K. Aunchaleevarapan, “A circularly polarized square plate antenna with two inclined slots for UHF-RFID reader,” 2011 Int. Symp. Intell. Signal Process. Commun. Syst. "The Decad. Intell. Green Signal Process. Commun. ISPACS 2011, 2011, doi: 10.1109/ISPACS.2011.6146137.

K. S. Rana and D. S. Ajij, “Design and simulation of NFC printed antenna in near field wireless communication for SDC,” 2016 IEEE Int. Conf. Distrib. Comput. VLSI, Electr. Circuits Robot. Discov. 2016 - Proc., pp. 247–251, 2016, doi: 10.1109/DISCOVER.2016.7806249.

Y. Li, S. Sun, L. Jiang, and T. T. Ye, “A circular polarization hybrid-integrated rectangular ring antenna for RFID reader,” IEEE Antennas Propag. Soc. AP-S Int. Symp., 2012, doi: 10.1109/APS.2012.6349197.

S. C. Lin, H. T. Hsu, T. J. Huang, H. J. Jhang, and H. T. Chou, “A circularly-polarized shaped-beam antenna array for radio frequency identification (RFID) reader applications at 2.4 GHz,” 2012 IEEE Int. Conf. Wirel. Inf. Technol. Syst. ICWITS 2012, 2012, doi: 10.1109/ICWITS.2012.6417760.

W. Ali et al., “Design and Analysis of a Quad-Band Antenna for IoT and Wearable RFID Applications,” Electron. 2024, Vol. 13, Page 700, vol. 13, no. 4, p. 700, Feb. 2024, doi: 10.3390/ELECTRONICS13040700.

W. Ali, Nizam-Uddin, M. Zahid, and S. Shoaib, “Performance Analysis and Design Optimization of Wearable RFID Sensor-Antenna System for Healthcare Applications,” IEEE Access, vol. 13, pp. 145540–145555, 2025, doi: 10.1109/ACCESS.2025.3596519.

S. S. A.-B. Md. Ashraful Haque, Md Afzalur Rahman, “Machine learning-based technique for gain and resonance prediction of mid band 5G Yagi antenna,” Sci. Rep., 2023, [Online]. Available: https://www.nature.com/articles/s41598-023-39730-1

G. S. B. Sourav Ghosh, “A dual-port, single-fed, integrated microwave and mm-wave MIMO antenna system with parasitic decoupling mechanism for 5G-enabled IoT applications,” AEU - Int. J. Electron. Commun., vol. 176, no. 1, p. 155122, 2024, doi: 10.1016/j.aeue.2024.155122.

M. A. Rahman, S. S. Al‑Bawri, M. T. Islam, M. J. Singh, and M. A. Rahman, “A Novel Compact Ultrawideband Microstrip Patch Antenna for Satellite Communications System,” Springer Proc. Phys., vol. 303, pp. 243–251, 2024, doi: 10.1007/978-981-97-0142-1_25.

M. A. Rahman, S. S. Al‑Bawri, M. T. Islam, M. J. Singh, D. Saha, and M. A. Haque, “A Compact Multiband Microstrip Antenna Design for 5G IOT and Satellite Communication Applications,” Springer Proc. Phys., vol. 303, pp. 125–132, 2024, doi: 10.1007/978-981-97-0142-1_13.

S. S. A.-B. Md Afzalur Rahman, “Miniaturized tri-band integrated microwave and millimeter-wave MIMO antenna loaded with metamaterial for 5G IoT applications,” Results Eng., vol. 24, p. 103130, 2024, doi: https://doi.org/10.1016/j.rineng.2024.103130.

A. J. A. A.-G. Nazrin Haziq Jemaludin, “A comprehensive review on MIMO antennas for 5G smartphones: Mutual coupling techniques, comparative studies, SAR analysis, and future directions,” Results Eng., vol. 23, p. 102712, 2024, [Online]. Available: https://www.sciencedirect.com/science/article/pii/S2590123024009678

J. L. and H. L. F. Xue, Y. Zhang, “Circularly Polarized Cross-Dipole Antenna for UHF RFID Readers Applicated in the Warehouse Environment,” IEEE Access, vol. 11, pp. 38657–38664, 2023, doi: 10.1109/ACCESS.2023.3253542.

& T. B. P. Sonali A. Kale, “Hybrid Metamaterial-Based Microwave Amplifiers for Enhanced Power Efficiency and Miniaturization in IoT Devices | Journal of RF and Microwave Communication Technologies,” Journal of RF and Microwave Communication Technologies. Accessed: Jan. 01, 2026. [Online]. Available: https://matjournals.net/engineering/index.php/JoRFMCT/article/view/1267

A. A. Elena García, “Overview of Reconfigurable Antenna Systems for IoT Devices,” Electronics, vol. 13, no. 20, p. 3988, 2024, doi: https://doi.org/10.3390/electronics13203988.

M. A. S. A. Faroq Razzaz, Saud M. Saeed, “Compact Ultra-Wideband Wilkinson Power Dividers Using Linearly Tapered Transmission Lines,” Electronics, vol. 11, no. 19, p. 3080, 2022, doi: https://doi.org/10.3390/electronics11193080.

J. I. L. Junho Yeo, “Gain Enhancement of Microstrip Patch Array Antennas Using Two Metallic Plates for 24 GHz Radar Applications,” Electronics, vol. 12, no. 7, p. 1512, 2023, doi: https://doi.org/10.3390/electronics12071512.

A. Hossain and A. V. Pham, “A Novel Gain-Enhanced Miniaturized and Lightweight Vivaldi Antenna,” IEEE Trans. Antennas Propag., vol. 71, no. 12, pp. 9431–9439, Dec. 2023, doi: 10.1109/TAP.2023.3310611.

M. H. J. Sahar Saleh, “Compactness and performance enhancement techniques of ultra-wideband tapered slot antenna: A comprehensive review,” Alexandria Eng. J., vol. 74, pp. 195–229, 2023, doi: https://doi.org/10.1016/j.aej.2023.05.020.

A. A. R. Saba Tariq, “Metasurface based antenna array with improved performance for millimeter wave applications,” AEU - Int. J. Electron. Commun., vol. 177, p. 155195, 2024, doi: https://doi.org/10.1016/j.aeue.2024.155195.

Y. F. Cheng, Z. H. Gao, W. J. Chen, C. Liao, and X. Ding, “Metasurface-Covered Planar Endfire Antenna with Vertical Polarization,” IEEE Trans. Antennas Propag., vol. 71, no. 6, pp. 5410–5415, Jun. 2023, doi: 10.1109/TAP.2023.3255643.

C. Zhou, W. Yang, Q. Xue, Y. Liu, Y. Xu, and W. Che, “Millimeter-Wave Wideband Dual-Polarized LTCC Antenna Array Based on Metasurfaces for Beam-Scanning Applications,” IEEE Trans. Antennas Propag., vol. 70, no. 10, pp. 9912–9917, Oct. 2022, doi: 10.1109/TAP.2022.3177448.

S. Verma, L. Mahajan, R. Kumar, H. S. Saini, and N. Kumar, “A small microstrip patch antenna for future 5G applications,” 2016 5th Int. Conf. Reliab. Infocom Technol. Optim. ICRITO 2016 Trends Futur. Dir., pp. 460–463, Dec. 2016, doi: 10.1109/ICRITO.2016.7784999.

S. Muzaffar, D. Turab, M. Zahid, and Y. Amin, “Dual-Band UWB Monopole Antenna for IoT Applications,” Eng. Proc. 2023, Vol. 46, Page 29, vol. 46, no. 1, p. 29, Sep. 2023, doi: 10.3390/ENGPROC2023046029.

C. H. Chang, T. A. Chang, M. Z. Kuo, T. M. Koo, C. I. G. Hsu, and X. Wang, “Low-Backward Radiation Circular Polarization RFID Reader Antenna Design for Sports-Event Applications,” Electron. 2025, Vol. 14, Page 3582, vol. 14, no. 18, p. 3582, Sep. 2025, doi: 10.3390/ELECTRONICS14183582.

W. Abdelrahim and Q. Feng, “Wideband Circularly Polarized Slot Antenna for Universal UHF RFID Reader,” 2018 Int. Conf. Microw. Millim. Wave Technol. ICMMT 2018 - Proc., Dec. 2018, doi: 10.1109/ICMMT.2018.8563580.

J. H. Lu and S. F. Wang, “Planar broadband circularly polarized antenna with square slot for UHF RFID reader,” IEEE Trans. Antennas Propag., vol. 61, no. 1, pp. 45–53, 2013, doi: 10.1109/TAP.2012.2220103.

B. Xu, S. Zhang, Y. Liu, J. Hu, and S. He, “Compact broadband circularly polarised slot antenna for universal UHF RFID readers,” Electron. Lett., vol. 51, no. 11, pp. 808–809, May 2015, doi: 10.1049/EL.2015.0593.

E. Mireles and S. K. Sharma, “A novel wideband circularly polarized antenna for worldwide UHF band RFID reader applications,” Prog. Electromagn. Res. B, no. 42, pp. 23–44, 2012, doi: 10.2528/PIERB12051019.

S. Bhaskar, M. G. Siddiqui, S. Singhal, and A. Bansal, “Miniaturized Circularly Polarized Vicsekcross-Shaped Slot Antenna for UHF-RFID Reader Handset Applications,” IEEE J. Radio Freq. Identif., vol. 6, pp. 515–523, 2022, doi: 10.1109/JRFID.2022.3195031.

C. Y. D. Sim, C. W. Lin, T. A. Chen, J. R. Liou, and H. T. Chou, “An eccentric annular slotted patch with parasitic element for UHF RFID reader applications,” 2019 IEEE Int. Conf. RFID Technol. Appl. RFID-TA 2019, pp. 37–40, Sep. 2019, doi: 10.1109/RFID-TA.2019.8892001.

I. U. Din, S. Ullah, N. Mufti, R. Ullah, B. Kamal, and R. Ullah, “Metamaterial-based highly isolated MIMO antenna system for 5G smartphone application,” Int. J. Commun. Syst., vol. 36, no. 3, p. e5392, Feb. 2023, doi: 10.1002/DAC.5392.

M. Y. Zeain, “A New Technique of FSS-Based Novel Chair-Shaped Compact MIMO Antenna to Enhance the Gain for Sub-6GHz 5G Applications,” IEEE Access, vol. 12, pp. 49489–49507, 2024, doi: 10.1109/ACCESS.2024.3380013.

Y. Qin, P. Wang, Y. Wang, Z. Yan, and H. Zhou, “Wideband Fabry-Perot Cavity Antenna Based on Single-Layer Partially Reflective Surface With Multiple Resonances,” IEEE Antennas Wirel. Propag. Lett., vol. 23, no. 12, pp. 4688–4692, 2024, doi: 10.1109/LAWP.2024.3465931.

Q. Liu and L. Zhu, “A Compact Wideband Filtering Antenna on Slots-Loaded Square Patch Radiator under Triple Resonant Modes,” IEEE Trans. Antennas Propag., vol. 70, no. 10, pp. 9882–9887, Oct. 2022, doi: 10.1109/TAP.2022.3184494.

Y. I. A. Hevin A. Muhammad, “A highly flexible and low-profile metasurface antenna for wearable WBAN systems,” Optik (Stuttg)., vol. 313, p. 171974, 2024, doi: https://doi.org/10.1016/j.ijleo.2024.171974.

N. K. Sonal Jatkar, “Investigation of SAR Reduction and Bending Effect Using a Flexible Antenna with EBG Structure for 2.45 GHz Wearable Applications,” Int. J. Intell. Syst. Appl. Eng., vol. 12, no. 21s, pp. 1006–1014, Mar. 2024, Accessed: Jan. 01, 2026. [Online]. Available: https://ijisae.org/index.php/IJISAE/article/view/5499

N. Sirait, F. Fathurahman, M. Alaydrus, and U. Umaisaroh, “Design of a Textile Antenna Using Metasurface Technology for Wireless Body Area Networks,” J. Telecommun. Electron. Control Eng., vol. 6, no. 2, pp. 89–96, Jul. 2024, doi: 10.20895/JTECE.V6I2.1326.

H. K. Nie et al., “Wearable Antenna Sensor Based on EBG Structure for Cervical Curvature Monitoring,” IEEE Sens. J., vol. 22, no. 1, pp. 315–323, Jan. 2022, doi: 10.1109/JSEN.2021.3130252.

S. S. Yuhao Wu, “Design of Quasi-Endfire Spoof Surface Plasmon Polariton Leaky-Wave Textile Wearable Antennas,” IEEE Access, 2022, [Online]. Available: https://ieeexplore.ieee.org/document/9933449

M. N. Youcef Braham Chaouche, “A Wearable Circularly Polarized Antenna Backed by AMC Reflector for WBAN Communications,” IEEE Access, 2022, [Online]. Available: https://ieeexplore.ieee.org/document/9693945

Y. Dong, Z. Wang, Y. Pan, and J. H. Choi, “Characterization of shorted dipole antennas for low-cost RFID reader applications,” IEEE Trans. Antennas Propag., vol. 68, no. 11, pp. 7297–7308, Nov. 2020, doi: 10.1109/TAP.2020.2998163.