67 International Journal of Communication Networks and Information Security (IJCNIS) Vol. 1, No. 3, December 2009 Analysis and Design of Printed Fractal Antennas by Using an Adequate Electrical Model Ferchichi Abdelhak 1 , Fadlallah Najib 2 , Sboui Noureddine 1 , Gharssallah Ali 1 1-Unit of research Circuits and Electronics Systems High Frequency Faculty of Science, University El Manar Tunis, Tunisia 2- Radiocom Team, Lebanese University IUT Saida, Lebanon abdelhakferchichi@yahoo.fr, n_fadlallah@yahoo.com Abstract: In this paper, we propose two electrical models of carpet and gasket Sierpenski patch antenna. In our approach, we replace the antenna structure by its equivalent rectangular patch. Then, we build the electrical model in which we extract the resonant circuit RLC parameters. Return losses of the models are compared to physical patch for frequency band [1GHz, 3GHz]. Simulation results given by our approach, show that the antenna and its model have the same resonant frequency at 2.45GHz but with a little difference in Bandwidth. Keywords: Fractal antenna, Sierpenski carpet, Sierpenski Gasket, Radio Frequency Identification RFID, electrical model 1. Introduction The booming progress of wireless communication systems and the variety applications increase the demand of microstrip patch antenna. They are used in many applications because of their low-profile, ease of fabrication, small size and low cost. One of the solutions is the fractal antenna. It is made in order to obtain a small and multiband patch. The sierpenski antenna is the first example of a multiband fractal antenna and it gives a small patch [1]. Those types of antennas were introduced in different applications like in RFID application which consist one of the new techniques of automatic identification and where the system size has a great importance and it depends essentially on the antenna size [2]. In this way, we design a patch based on sierpenski carpet and sierpenski gasket antenna by using ADS simulator. In order to analyze those structures, we proposed the equivalent electrical model of Sierpenski and we compared it to a physical patch. The two models are based on the electrical model of square patch. This paper is organized as follows. In section 2, a proposed equivalent circuit of the first iteration of Sierpenski carpet patch antenna is presented. In section 3, the electrical model of the first iteration of sierpenski gasket patch is developed. Finally, section 4 deals with the different conclusions. 2. Sierpenski carpet antenna 2.1. Design of square antenna Figure (1) shows the geometry of a square microstrip patch on a dielectric substrate with a ground plane. The antenna have an edge a = 36mm and it is mounted on a substrate material with a thickness h=3.2mm, a dielectric constant 2.6 r ε = and loss tangent (tangδ) = 0.002. The dimension ‘a’ of the square edge is calculated using equation (1): c 2 r r a f ε = (1) Figure 1. Square patch