Indonesian Journal of Electrical Engineering and Computer Science Vol. 27, No. 2, August 2022, pp. 849~858 ISSN: 2502-4752, DOI: 10.11591/ijeecs.v27.i2.pp849-858  849 Journal homepage: http://ijeecs.iaescore.com Bandwidth enhancement of ultra-wideband monopole antenna designed with v-shaped defected ground structure Lee Yee Hui 1 , Dayang Azra Awang Mat 1 , Dyg Norkhairunnisa Abang Zaidel 1 , Kismet anak Hong Ping 1 , Shafrida binti Sahrani Shahran 2 1 Department of Electrical and Electronics Engineering, Faculty of Engineering, University Malaysia Sarawak (UNIMAS), Samarahan, Malaysia 2 Research Fellow, Institute of IR4.0, Aras 1, Akademia Siber Teknopolis, Universiti Kebangsaan Malaysia, Bandar Baru Bangi, Malaysia Article Info ABSTRACT Article history: Received Jul 22, 2021 Revised May 25, 2022 Accepted Jun 10, 2022 This paper discusses the design of a monopole antenna with various types of defected ground structures (DGS) for ultra-wideband (UWB) applications. The various types of DGSs are designed and acted as the ground layer of the antenna. The bandwidth of each design is then compared with and without the existence of DGS. Conventional monopole antenna has a bandwidth of 88.6% and operates in the frequency range of 3.1 to 8 GHz. According to the simulation results, the bandwidth of the monopole antenna with V-shaped DGS was the highest, which was at 133.3% (2.98-14.9 GHz), as compared to other types of DGS. The efficiency was between 30 to 64%, with a peak realized gain of 5.3 dB. The V-shaped DGS is then fabricated on a rogers RO4003C substrate with a relative permittivity, , of 3.38 and a dimension of 29.86×39.03×0.81 mm. The antenna is measured using R&S network analyzer and the results were 3-8.5 GHz and 95.4% of BW, which signified the increased performance of the antenna. Keywords: Bandwidth enhancement Defected ground structures Monopole antenna Rogers RO4003C U&V-shaped This is an open access article under the CC BY-SA license. Corresponding Author: Dayang Azra binti Awang Mat Department of Electrical and Electronics Engineering, Faculty of Engineering Universiti Malaysia Sarawak (UNIMAS) Sarawak, Malaysia Email: amdazra@unimas.my 1. INTRODUCTION Nowadays, the antenna represents the key component in wireless communication and microwave imaging applications. Compact, easy to fabricate, low profile and low cost are the requirements of antennas for future communication applications and microstrip monopole antenna fulfills these requirement [1], [2]. The main aim of the current research is to propose a design for a small high-performance antenna. Various approaches have been taken by previous researchers, such as notches and slots [2]–[8], tuning stub [8], [9], electromagnetic bandgap (EBG) [10]–[12], magneto-dielectric substrate [13], dielectric substrates with high permittivity [14] and defected ground structure (DGS) [15]. In this research, the focus is on the DGS. DGS can be defined as the region of any shape that is etched off from the ground plane. Electrical current flow distribution is affected by the design of the ground plane and causes excitation and propagation of an electromagnetic wave, which is manipulated by passing the current through the substrate [16]. As compared to other techniques such as EBG, DGS can be easily applied to microwave circuits and could increase the accuracy with just its basic structures [17]. The advantage of DGS is that the slow-wave effect can be achieved easily by using only one or a few DGS structures. This results in