International Symposium on Devices MEMS, Intelligent Systems & Communication (ISDMISC) 2011 Proceedings published by International Journal of Computer Applications® (IJCA) 1 Irregular Circular Fractal Slot Antenna for Dual Wideband Applications Sujeet Kumar Rai Dept. of Electronics and Communication Engg, National Institute of Technology, Rourkela Rourkela, India Yogesh Kumar Choukiker Dept. of Electronics and Communication Engg, National Institute of Technology, Rourkela Rourkela, India S K Behera Dept. of Electronics and Communication Engg, National Institute of Technology, Rourkela Rourkela, India ABSTRACT A compact CPW-fed fractal circle monopole antenna with dual wideband is presented for simultaneously satisfying wireless local area network (WLAN) for 2.4/5.2/5.8 GHz application. The antenna consists of irregular shape circles based on the Descartes circle theorem. The simulated -10 dB bandwidth for return loss is from 2.04 to 3.35 GHz and 4.96 to 5.9 GHz, covering all the 2.4/5.2/5.8 GHz WLAN Bands obtained. It is observed that the gain of proposed antenna for 2.4 GHz and 5.2 GHz is 3.606 dBi and 5.96 dBi respectively. This antenna gives stable monopole-like radiation patterns. Keywords Dual wide band; Circular Antenna; Fractal Antenna; CPW- fed; Descartes Circle Theorem 1. INTRODUCTION Recently, the ability to integrate more than one communication standard into a single system has become an increasing demand for a modern portable wireless communication device. However, it is difficult to simultaneously set the dual or multiple antennas and a diplexer into such a device due to the limited space of device. This indicates that a modern antenna requires not only the function of providing a dual- or multiband operation, but also a simple structure, compact size, and easy integration with the system circuit. For this, many promising dual- or multiband planar antenna designs such as the as microstrip-fed printed double-T monopole [1], dual loop antenna [2] and reduced size PIFA [3] were proposed to provide dual-band characteristics to cover the 2.4/5.2 and 5.8 GHz Wireless local area network (WLAN) bands . However, these antennas could not provide uniform omnidirectional coverage. The printed dipole antenna reported in Ref. [4] incorporates two separate dipoles of different arm lengths printed on both sides of the dielectric substrate for dual band operation. The longer and shorter dipoles were designed to generate resonant radiation at 2.4 and 5.2 GHz bands. The primary limitation of this kind of design is large size of antenna and limited bandwidth. In dual-band dipole antenna reported by Su et al. [5], two resonances were obtained by cutting a U-slot in arms of the dipole. Other dual-band antenna reported by Yang, F et al. [6], the two resonances were obtained by cutting an E-slot in arms of the antenna. Wu et al. [7] reported a dual broad band slot antenna, in which the two wide resonances were obtained by using a U-shaped strip inset at the center of slot antenna. The dual-band WLAN dipole antenna proposed by Zhang et al. [8]. In fractal electrodynamics, fractal geometry is used to investigate a new class of radiation, propagation, and scattering problems. One of the promising researches is antenna theory and design using the fractal concept [9]. Most fractal objects have self similar shape, with different scale [10, 11]. The fractal shape carried out by applying the infinite number of iteration using multiple reduction copy machine (MRCM) algorithm [12]. On the other hand, a circular generator with a non-constant fractal ratio dependent on the Descartes Circle theorem in CPW-fed structure is reported for dual and wideband antennas [13-15]. A simple and compact design of a dual band printed antenna operating at 2.4/5.2/5.8 GHz band is proposed for in this paper. The proposed antenna, designed for the WLAN applications, retains the advantage in terms of size when compared to the ultra wide band slot antennas tailored for the FCC approved UWB band (3.1–10.6 GHz), in spite of the lower frequencies of operation [16]–[19]. The design of the antenna was performed and optimized using CST Microwave Studio Suit TM 2010 based on three dimensional finite integration time-domains (FITD) method. This antenna also provides the detail study of different iteration, radiation pattern and gain and the EM characteristics by surface current distribution. 2. ANTENNA DESIGN The proposed dual wideband Circular fractal antenna is shown in Fig. 1. The classical fractal circle shape antenna is reported in [19]. The following design is based on the principle of Descartes circle theorem with different radius [15]. If four mutually tangent circles have curvatures k i (for i=1,2…..4), Then, the curvatures satisfied the relation [13-14] (k 1 +k2+k 3 +k 4 )=2(k 2 1 +k 2 2 +k 2 3 +k 2 4 ) Where, k 1 =1/R k1, K2=1/R k2, k 3 =1/R k3, k 4 =1/Rk4 And radius of the circles are R k1 ,R k2 ,R k3, R k4 .