Concentric-arm Fractal Antenna for Wireless Applications Saurabh Srivastava, Avanish Deo Pandey and MR Tripathy Department of Electronics and Communication Engineering, Amity University, Noida, Uttar Pradesh, India Saurabhec89@gmal.com Abstract— This paper presents the design of a concentric shaped fractal antenna suitable for use in multiple frequency band .The CPW-feed and fractal concept have been used to achieve the wide bandwidth in multi frequency band. The shape of the fractal geometry, the number of iterations and the number of concentric shapes are the important factors for achieving wider impedance bandwidth. The Simulated result of the fractal antenna exhibits multiple frequency band characteristics in the frequency range of 1.09 GHz to 10.32 GHz corresponding to bandwidth in between range of 50 MHz- 88 MHz. The obtained radiation patterns of the proposed antenna are close to omni-directional in the H–plane and bidirectional in the E-plane Keywords; Planar Monopole antenna, Multiband antenna, Fractal Geometry, CPW - Feed and UWB System I. INTRODUCTION The recent progress in wireless communication applications has remarkably increased the demand for wideband antennas with smaller dimensions than conventionally possible [1]. The antenna size with respect to the wavelength is one of the critical parameter that will influence the radiation characteristics, gain and efficiency. Some Conventional microstrip antenna has limitations of narrow bandwidth, low gain and size of ƛ /2 [1-2]. There are several techniques used in the open literatures to gradualy improve the bandwidth of the microstrip patch antenna some of them are insertion of air gap, stacking, ground coupling etc. The coupling effect in the antenna is possible by changing the types of the feed and selecting the proper values for its parameters. The CPW feed gives better resonant characteristics and higher impedance bandwidth. [3-4]. The fractal geometry along with the CPW feed can be used for achieving ultra wide bandwidth [4]. The fractal geometry is utilized by using its two properties i.e. self- similarity and space filling [5]. The self-similarity property is most useful for having multiband or ultra wideband (UWB) feature while space filling property is useful for antenna miniaturization i.e reducing antenna size considerably. Using some of these properties, several UWB monopole antennas have been reported in the literature [5-6]. This paper presents an UWB antenna with bandwidth beyond the normal bandwidth obtained through the normal circular patch. Several modifications in the antenna structures like adding concentric arms, increasing the number of iterations and introducing the slots in the ground plane have been made to achieve the desired impedance bandwidth. All results are validated by simulations and experiments II. GEOMETRY OF ANTENNA Fractals are the space filling geometries that can efficiently incorporate very large electrical lengths in antennas. The dimension of the geometry can be interpreted as a quantification of the space filling ability of the concerned geometry. The fractal antenna structure taken for experimentation is shown in Figure.1. This fractal antenna is designed on a substrate of dielectric constant εr = 4.4, thickness 1.53 mm and with dimensions 75 mm x 65 mm. The fractal antenna is constructed from a solid circular disc of radius 12 mm as shown in the Fig. 1. Figure 1. Fourth iterative Concentric arm fractal antenna This fractal antenna is constructed by using a set of scaled versions of the same shape which is similar to the concept of