A Circular Sierpinski fractal antenna for UWB applications A. El Hamdouni LAMEET Laboratory of Faculty of Sciences and Techniques of Settat Morocco akram.elhamdouni@yahoo.fr A. Tajmouati LAMEET Laboratory of Faculty of Sciences and Techniques of Settat Morocco tajmoua@gmail.com J. Zbitou LAMEET Laboratory of Faculty of Sciences and Techniques of Settat Morocco jazbitou@gmail.com ABSTRACT In this paper 1 a depicted survey of a Coplanar Waveguide (CPW) printed antenna achieved by using the Sierpinski Gasket as fractal geometry in the radiator which is taken as circular shape, the iterations has been performed three times in order to improve the matching of Input Impedance at 50  in the Ultra-wide band (UWB), which is the frequency range 3.1 – 10.4 GHz released by the Federal Communications commission (FCC). The electromagnetics solvers CST of Microwave Studio have been used to design the proposed antenna by the methods of optimization included in the software tool and to compute the coefficient of reflection and the gain radiation pattern. The FR4 has been chosen as substrate to simulate the printed antenna with an overall dimension of 34 x 43 mm 2 . KEYWORDS CPW, Fractal Geometry, Sierpinski Gasket, Input Impedance, UWB, Gain, Radiation Pattern. 1 INTRODUCTION The Coplanar Waveguide (CPW) device is one of the techniques of feeding which is become more and more involved in the domain of printed antenna due to several and unique features missed in the others methods of antenna conception. So it’s important to note that CPW antennas are characterized by a less dispersion, low radiation loss, simplicity to design and integrate with passive and active circuits, also the CPW antenna is one of Permission Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Permissions@acm.org. ICCWCS'17, November 14–16, 2017, Larache, Morocco © 2017 Association for Computing Machinery. ACM ISBN 978-1-4503-5306-9/17/11…$15.00 https://doi.org/10.1145/3167486.3167560 the devices that can be operate in wider bandwidth by a good input impedance matching. Those advantages are because of the way of configuration of this kind of antennas which is based on co-location in the same side of substrate the ground, the feed line and the radiator, by depositing symmetrically of the feed line conductor in between the two narrow grounds [1–4]. The Fractal geometry can used together with CPW feeding method in order to give some specifics characteristics such self- similarity which is mandatory to improve the matching of input impedance in some frequencies and the space filling which can be utilized to increase the miniaturization behavior, also the fractal technique can help to optimize the gain of the antennas that can be used in the indoor applications. There are many fractal geometries to etch the CPW antennas such as the Sierpinski Carpet, Cantor Set, Koch Curves and Sierpinski Gasket. The last one still the more popular geometry used in the printed antenna. The process to create the Sierpinski Gasket geometry is given by two steps which are iterated infinitely, the first step is to take a plane triangle and the second step is to remove a central triangle with vertices which are located at the midpoint first triangle sides [5–8]. The CPW feeding technique merged with Sierpinski Gasket fractal geometry become widely existing in the design of printed antenna proposed for Ultra-Wide Band applications. Therefore the definition of UWB still too complicated due to the diversity of standards. The definition of UWB in European regulation based on the use of spectral masks in order to classify the applications by frequency range, while the American regulation is based on two main standards to provide a definition of the UWB, the first one is by The Defense Advanced Research Projects Agency (DARPA) which use the below Taylor expression.  = 2  −   +  (1) Where  is the fractional Bandwidth of the signal and respectively  is the higher and  is the lower -3dB point in a spectrum. According to DARPA a signal is identified as UWB when the  is greater than 0.25.