Indonesian Journal of Electrical Engineering and Computer Science Vol. 16, No. 2, November 2019, pp. 818~826 ISSN: 2502-4752, DOI: 10.11591/ijeecs.v16.i2.pp818-826  818 Journal homepage: http://iaescore.com/journals/index.php/ijeecs Development of MIMO antenna with decoupling structure for ultra-wideband application Muhammad Aslam Hasin, M. T. Ali, Hamizan Yong, Bazilah Baharom, Hadi Jumaat Antenna Research Centre (ARC), Faculty of Electrical Engineering, University Teknologi Mara (UiTM), Malaysia Article Info ABSTRACT Article history: Received Jan 19, 2019 Revised Apr 20, 2019 Accepted May 16, 2019 This paper presents the design of a double-sided Multiple-Input Multiple- Output (MIMO) antenna with a decoupling structure for Ultra-WideBand (UWB) applications. The proposed antenna consists of four square radiating elements printed on FR-4 substrate with partial slotted ground. The substrate consists of two sides and each side are consisting of two slotted partial ground and two square radiator antennas. The elements of the front side are orthogonal to the elements of the back side because it was to increase the isolation of the antenna. The front and back sides of the substrate were also presented with the decoupling structure to avoid the mutual coupling of each antenna. The results of simulated and measured of the proposed UWB MIMO antenna are observed and analyzed. The objective of the UWB MIMO antenna was achieved that large bandwidth of return loss below than - 10 dB from 3.3 GHz to 11GHz with an insertion loss lower than -20 dB within the required frequency band. The proposed MIMO antennas exhibits a nearly Omni-directional radiation pattern with average gain value 4.36 dBi. Keywords: Decoupling structure High isolation antenna Orthogonal radiator UWB MIMO antenna Copyright © 2019 Institute of Advanced Engineering and Science. All rights reserved. Corresponding Author: Muhammad Aslam Bin Hasin, Antenna Research Centre (ARC), Faculty of Electrical Engineering, University Teknologi MARA (UiTM), 40450, Shah Alam, Selangor Darul Ehsan, Malaysia. Email: aslam7484@gmail.com 1. INTRODUCTION In the development of modern communication, the ultra-wide band (UWB) technology play an interest to the researcher since the high data rate demand with a limited range in lower power spectral level [1] in order to protect the interference of UWB system from other existed wireless systems [2-3]. In numerous wireless applications, the technology of UWB becomes more tempting and bring attention to all researchers as the Federal Communication Commission (FCC) released the ultra-wide band (UWB) technology that operates from 3.1 to 10.6 GHz [1-2]. Larger bandwidth with stable radiation, compact size, and low profile are the challenges in order to design UWB antenna [5-7]. Moreover, when dealing with the compact size of the MIMO antenna, it will introduce mutual coupling that will limit the channel capacity of the system [4-6]. Multiple-input Multiple-output (MIMO) technology was used to overcome the Multipath fading that is one of the main problems that causes the performance of the UWB system to be downgraded [11-13]. The distance between elements of the MIMO system should be more than half lamda of the lowest operating frequency in order to avoid the mutual coupling between elements [14-16]. However, this method also increases the size of the MIMO antenna. For the proper performance in a MIMO system, the isolation between elements must be less than -15 dB [14], [17-18]. In this paper, four elements have been mounted on a 4 cm × 4 cm on a FR4 substrate of compact MIMO_UWB antenna. This is done to ensure that the allocated bandwidth for application of UWB from 3.3 GHz until 11.0 GHz has been satisfy. After decoupling structure between elements on the top and bottom