(Received: 3-Nov.-2023, Revised: 28-Dec.-2023 , Accepted: 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.

[1] Revision of Part 15 of the Commissions’ Rule Regarding Ultra-wideband Transmission System, First Report and Order, "Federal Communications Commission FCC 02-48," Washington, Apr. 2002.

[2] C. A. Balanis, Antenna Theory Analysis and Design, 4th Edition, John Wiley & Sons, Inc., Hoboken, New Jersey, 2016.

[3] D. H. Werner, R. L. Haupt and P. L. Werner, "Fractal Antenna Engineering: The Theory and Design of Fractal Antenna Arrays," IEEE Antennas and Propagation Magazine, vol. 41, no. 5, pp. 37-59, 1999.

[4] J. Anguera, C. Puente, C. Borja and J. Soler, "Fractal-shaped Antennas: A Review," Encyclopedia of RF and Microwave Engineering, vol. 2, pp. 1620–1635, DOI: 10.1002/0471654507.eme128, 2005.

[5] C. Borja and J. Romeu, "On the Behaviour of Koch Island Fractal Boundary Micro-strip Patch Antenna," IEEE Transactions on Antennas and Propagation, vol. 51, no. 6, pp. 1281–1291, 2003.

[6] V. V. Reddy and N. V. S. N. Sarma, "Triband Circularly Polarized Koch Fractal Boundary Microstrip Antenna," IEEE Antennas and Wireless Propagation Letters, vol. 13, pp. 1057-1060, 2014.

[7] M. R. Haji-Hashemi, M. M. M. Sadeghi and V. M. Moghtadai, "Space-filling Patch Antennas with CPW Feed," Proc. of Progress in Electromagnetics Research Symposium, pp. 26–29, Cambridge, USA, 2006.

[8] M. G. Fekadu and S. N. Sinha, "UWB Fractal Slot Antenna Designs," Proc. of the 2011 IEEE Int. Conf. on Microwaves, Communications, Antennas and Electronics Systems (COMCAS), pp. 1–4, DOI: 10.1109/COMCAS.2011.6105799, 2011.

[9] S. Tripathi, A. Mohan and S. Yadav, "Ultra wideband (UWB) Antenna Using Minkowski Like Fractal Geometry," Microwave and Optical Technology Letters, vol. 56, no. 3, pp. 2273–2279, 2014.

[10] S. Tripathi, A. Mohan and S. Yadav, "A Multi Notched Octagonal Shaped Fractal UWB Antenna," Microwave and Optical Technology Letters, vol. 56, no. 11, pp. 2469–2473, 2014.

[11] C. Puente-Baliarda, J. Romeu, R. Pous and A. Cardama, "On the Behavior of the Sierpinski Multiband Fractal Antenna," IEEE Transactions on Antennas and Propagation, vol. 46, no. 4, pp. 517-524, DOI: 10.1109/8.664115, April 1998.

[12] D. Li and J.-f. Mao, "A Koch-like Sided Fractal Bow-tie Dipole Antenna," IEEE Transactions on Antennas and Propagation, vol. 60, no. 5, pp. 2242-2251, DOI: 10.1109/TAP.2012.2189719, May 2012.

[13] S. Tripathi, A. Mohan and S. Yadav, "A Compact UWB Koch Fractal Antenna for UWB Antenna Array Applications," Wireless Personal Communications, vol. 92, pp. 1423–1442, 2017.

[14] S. Dhar, R. Ghatak, B. Gupta and D. R. Poddar, "A Wideband Minkowski Fractal Dielectric Resonator Antenna," IEEE Transactions on Antennas and Propagation, vol. 61, no. 6, pp. 2895–2903, 2013.

[15] N. Tasouji, J. Nourinia, C. Ghobadi and F. Tofigh, "A Novel Printed UWB Slot Antenna with Reconfigurable Band-notch Characteristics," IEEE Antennas and Wireless Propagation Letters, vol. 12, pp. 922–925, 2013.

[16] A. Gobinath, N. Sureshkumar, K. K. Hema, T. Sureka and B. Pavithra, "Design of Koch Fractal Antenna for Wireless Applications," International Journal of Engineering Research & Technology (IJERT) NCIECC-2017, vol. 5, no. 9, 2017.

[17] S. Mythili, K. Akshaya, B. Charanya and K. Ayyappan, "Design and Analysis of Koch Fractal Antenna for WLAN Applications," ICTACT Journal on Microelectronics, vol. 06, no. 02, pp.923-927, 2020.

[18] M. Gupta and V. Mathur, "Koch Boundary on the Square Patch Microstrip Antenna for Ultra Wideband Applications," Alexandria Engineering Journal, vol. 57, no. 3, pp. 2113-2122, 2018.

[19] S. Singhal, T. Goel and A. Kumar Singh, "Inner Tapered Tree-shaped Fractal Antenna for UWB Applications," Microwave and Optical Technology Letters, vol. 57, no. 3, pp. 559-567, 2015.

[20] H. Z. Liu, J. C. Coetzee and K. Mouthaan, "UWB Antenna Array for Wireless Transmission along Corridors," Microwave and Optical Technology Letters, vol. 50, no. 4, pp. 886–890, 2008.

[21] S. Mahesh, A. Khairnar and M. Hasan, "A New Approach to Fractal Antenna Design for UWB Applications: An Analysis," Mathematical Statistician and Engineering Applications, vol. 71, no. 4, pp. 2326-9865, 2022.

[22] I. H. Nejdi et al., "UWB Circular Fractal Antenna with High Gain for Telecommunication Applications," Sensors, vol. 23, no. 8, p. 4172, 2023.

[23] M. A. Khan, U. Rafique, H. Ş. Savci, A. N. Nordin, S. H. Kiani and S. M. Abbas, "Ultra-wideband Pentagonal Fractal Antenna with Stable Radiation Characteristics for Microwave Imaging Applications," Electronics, vol. 11, no. 13, p. 2061, 2022.

[24] S. Ullah, C. Ruan, M. S. Sadiq, T. U. Haq, A. K. Fahad and W. He, "Super Wideband, Defected Ground Structure (DGS) and Stepped Meander Line Antenna for WLAN/ISM/WiMAX/UWB and other Wireless Communication Applications," Sensors, vol. 20, p. 1735, DOI: 10.3390/s20061735, 2020.

[25] M. Rohaninezhad et al., "Design and Fabrication of a Super-wideband Transparent Antenna Implanted on a Solar Cell Substrate," Scientific Reports, vol. 13, no. 1, p. 9977, 2023.

[26] H. Şerif Savcı, "A Four Element Stringray-shaped MIMO Antenna System for UWB Applications," Micromachines, vol. 14, no. 10, p. 1944, 2023.

[27] S. Hassan Kiani et al., "An Ultra-Wide Band MIMO Antenna System with Enhanced Isolation for Microwave Imaging Applications," Micromachines, vol. 14, no. 9, p. 1732, 2023.

[28] S. Hassan Kiani et al., "A Novel Shape Compact Antenna for Ultra Wideband Applications," Int. Journal of Antennas and Propagation, vol. 2021, p. 7004799, DOI: 10.1155/2021/7004799, 2021.

[29] A. Chowdhury and P. Ranjan, "A Novel Circularly Polarized, CPW-based MIMO Antenna for 5G-Wireless Communication in Sub-6 GHz Band," Int. Journal of Electronics Letters, DOI: 10.1080/21681724.2023.2266608, 2023.

[30] M. A. Sufian, N. Hussain, H. Askari, S. G. Park, K. S. Shin and N. Kim, "Isolation Enhancement of a Metasurface-based MIMO Antenna Using Slots and Shorting Pins," IEEE Access, vol. 9, pp. 73533-73543, 2021.