KOCH FRACTAL OCTAGONAL ANTENNA WITH A COMPACT DESIGN AND DEFECTED GROUND STRUCTURE (DGS) FOR ULTRA-WIDEBAND (UWB) WIRELESS USAGE 10.5455/jjcit.71-1698995606 Tejaswita Kumari,Abu Nasar Ghazali,Anupama Senapati Koch fractal geometry,UWB,DGS,Group delay,Correlation coefficient,Fidelity factor,Octagonal,WBAN,WPAN 476 84 3-Nov.-2023 28-Dec.-2023 21-Jan.-2024 This paper introduces a Koch fractal octagonal antenna designed for the ultra wideband (UWB) frequency range. The utilization of the Koch fractal in the antenna design contributes to size reduction and provides compactness in the antenna for UWB. Additionally, it has been noted that the Koch fractal offers wideband operation. The antenna employs copper as the conductor material and Flame Retardant-4 (FR-4) serves as the substrate. The substrate has a dielectric constant ϵr =4.4, a loss tangent tanδ=0.02 and a thickness (h) of 1.6 mm. The overall antenna’s dimensions are 34.3 × 26.5 × 1.6 and its electrical dimensions are 0.68λ0 × 0.53λ0 × 0.032λ0. It achieves a maximum gain of 8.94 dBi at a frequency of 12.25 GHz, offering a broad bandwidth ranging from 2 GHz to 12.1 GHz. This antenna exhibits resonance at three distinct frequencies; namely, 3.3 GHz, 6 GHz and 8.6 GHz, making it highly efficient with an overall efficiency of 96.8%. The time-domain characteristic of the antenna is acceptable for UWB, group delay is 1.1 ns, the proposed antenna has a high-fidelity factor of 90.2 and the correlation coefficient is 0.9, which makes the antenna a good candidate for UWB. Due to its performance characteristics, this proposed antenna is wellsuited for short-range wireless personal area networks (WPANs), supporting high-data-rate applications, like Bluetooth and wireless USB and Wireless Body Area Network (WBAN) applications. Its proficiency also extends to industrial settings, where it helps with precision in control systems, asset tracking and short-range sensing and radar systems.