Open complementary split-ring resonator-embedded tri-band rectangular monopole antenna with offset feed for next-gen wireless applications

This paper presents the design and development of a compact tri-band rectangular monopole antenna tailored for Wireless Local Area Network (WLAN), Wireless Avionics Intra-Communications (WAIC), and Worldwide Interoperability for Microwave Access (WiMAX) applications. The antenna integrates an Open Complementary Split-Ring Resonator (OCSRR) etched onto the radiating patch and employs an offset microstrip feed to enhance impedance matching and multiband performance. Fabricated on an FR4 substrate (27.84 mm × 23.25 mm × 1.6 mm), the antenna achieves resonances at 3.16 GHz, 3.82 GHz, and 5.41 GHz. The OCSRR introduces a resonance at 3.16 GHz by exhibiting negative permittivity, verified through the Nicolson-Ross-Weir (NRW) method. Ground plane reduction and offset feeding contribute to additional resonances and bandwidth enhancement. The antenna demonstrates strong agreement between simulated and measured results, with reflection coefficient of - 19.83 dB, - 17.9 dB, and - 55.73 dB, and impedance bandwidths of 180 MHz, 190 MHz, and 2750 MHz, respectively. Radiation patterns remain stable across all bands, with peak gains of 2.19 dBi, 2.27 dBi, and 2.82 dBi. The proposed antenna offers a low-profile, high-performance solution for next-generation wireless systems requiring compact size, multiband operation, and reliable performance.