In this paper, a compact modified hexagonal spiral resonator-based tri-band patch antenna with an octagonal slot is presented for Wi-Fi/WLAN applications. The proposed antenna is designed on a low-cost FR4 substrate with a dielectric constant of εr=4.4 and loss tangent δ=0.02. The tri-band operations have been achieved by the a Modified Hexagonal Complementary Spiral Resonator (MHCSR) and an Octagonal slot. The loading of the MHCSR at the bottom of the substrate is to cover the 900MHz (IEEE 802.11ah) band, and an Octagonal slot on top of the 5 GHz (IEEE 802.11a/h/j/n/ac/ax) rectangle patch is to cover the 2.4 GHz (IEEE 802.11b/g/n/ax)band. The prototype of the proposed antenna is fabricated and tested to validate the simulation results. The measured impedance bandwidth is 105 MHz at 900 MHz, 160 MHz at 2.4 GHz, 18 0MHz at 5 GHz. The designed antenna has a compact size with overall dimensions of 0.054λ0 x 0.066 λ0 x 0.0048 λ0 (18 x 22 x 1.6 mm3). The 82.2% reduction in size has been accomplished as compared to a conventional patch antenna at 900MHz (lower resonance frequency). The waveguide setup method has been used to validate a negative permittivity property of the MHCSR. The parametric analysis of the proposed antenna had been carried out using the Ansoft HFSS19 software.
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