VOL. 10, NO. 4, MARCH 2015 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences © 2006-2015 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 1762 DESIGN OF ULTRA WIDEBAND SMALL CIRCULAR PATCH ANTENNA FOR WIRELESS COMMUNICATION Soufian Lakrit and Hassan Ammor Electronic and Communication Laboratory, Mohammed V University Agdal, UM5A EMI- Avenue Ibnsina, Agdal, Rabat, Morocco E-Mail: lakritsoufian@gmail.com ABSTRACT This paper presents the design of an ultra-wideband Circular microstrip patch antenna for (UWB) communications. In this structure there is a small Circular patch consists of a partial ground plane and fed by a 50 Ω microstrip line. The proposed antenna can achieves a wide bandwidth from 2.72 GHz to 12.17 GHz with VSWR < 2 with stable and bi-directional radiation pattern. The simulation of this antenna has been performed by using Ansoft High Frequency Structure Simulator (HFSS) and Computer Simulation Technology- Microwave Studio (CST). Keywords: microstrip, ultra-wideband (UWB), VSWR, HFSS, CST. 1. INTRODUCTION With the rapid developments in broadband wireless communications and the great number of commercial and military applications, necessitate new types of antennas, which can support higher bit rates. 4G mobile terminals are gaining immense popularity thanks to their advanced and user-friendly features. Also, designing new compact antennas with good characteristics applied for 3G mobile terminals is quite necessary although number of similar studies had been conducted so far[1], since the Federal Communications Commission(FCC) allowed 3.1 to 10.6 GHz or the signal bandwidth is more than 500MHz unlicensed band for UWB communication [2]. UWB also have wide applications in short range and high speed wireless systems, such as ground penetrating radars, medical imaging system, high data rate wireless local area networks WLAN (5.15–5.35 and 5.725–5.825 GHz), downlink of X-band satellite communication systems (7.25–7.75 GHz) and ITU (8.025– 8.4 GHz). Many techniques have already been applied to design wideband antennas for different applications, one of which to increase the bandwidth. Since microstrip patch antennas inherently have narrow bandwidth characteristic, there have been numerous techniques developed for bandwidth enhancement in order to achieve the UWB characteristics[3]. These antennas have been discussed in the literature, for instance, U-slot stacked patch antennas [4], triangle Circular fractal antenna [5], H-slot antenna [6], E-shaped patch antenna [7]. Other techniques employed to increase the bandwidth of antennas include meandered ground plane [8], slot loading [9], meandering slots [10], tulip-shaped monopole antenna [11] and T-slot in the radiating element [12]. In this paper, a novel small Circular patch antenna is proposed, This structure present a wide bandwidth and miniaturized dimensions, sufficient impedance bandwidth and highly stable and bi-directional radiation pattern is obtained. The planar antenna consists of a circular shaped radiating patch and partial ground plane with a T-shaped slot on the upper edge to cause a broad bandwidth from 2.76 to 11.71 GHz frequency. The antenna structure is flat, and its design is simple and straightforward. Details of the proposed design are presented and discussed in this paper. The proposed antenna design and performances are analyzed by using Ansoft High Frequency Structure Simulator (HFSS) and Computer Simulation Technology- Microwave Studio (CST). 2. ANTENNA GEOMETRY AND DESIGN Figure-1 illustrated the configuration of the proposed antenna, which consist of a circular patch, a partial ground plane and a T-shaped slot on the ground plane. The antenna, which has a compact dimension of 5mm The radius a, is printed in the front of a FR4 substrate of thickness 1.58mm and relative permittivity 4.4. The dimension of partial ground plane, which is printed in the bottom side of the substrate, is chosen to be 12×3.5mm 2 in this study. The bottom of the patch is connected by a microstrip line, which is fed by a 50Ω coaxial probe from the side of the antenna. The microstrip line was etched on the same side of the substrate as the radiator. The antenna has the following parameters: LSub=18mm, WSub=12mm, a = 5mm, LG = 3.5mm, lf= 7mm, Wf = 2mm, h=1.58mm, wS1=lS1=1mm, wS2=0.5mm, lS2=6mm. Top view Bottom view side view Figure-1. Geometry of proposed antenna. 3. RESULTS AND DISCUSSIONS In this section, the circular patch antenna with various design parameters is constructed, and the