Int. J. Electron. Commun. (AEÜ) 66 (2012) 647–654 Contents lists available at SciVerse ScienceDirect International Journal of Electronics and Communications (AEÜ) jou rn al h omepage: www.elsevier.de/aeue A modified ground apollonian ultra wideband fractal antenna and its backscattering Raj Kumar a,∗ , Pritam B. Nikam b a Department of Electronics Engg., Defence Institute of Advanced Technology (DU), Girinagar, Pune -411 025, India b M. Tech. Student, Microwave Engineering Department, PICT, Pune -411029, India a r t i c l e i n f o Article history: Received 17 April 2011 Accepted 5 December 2011 Keywords: Antenna Fractal antenna Resonant frequency UWB system Coplanar waveguide feed a b s t r a c t This paper presents the design of a modified ground apollonian ultra wideband (UWB) fractal antenna. The printed fractal antenna has been designed on a substrate with dielectric constant ε r = 4.3 and thickness h = 1.53 mm. The antenna has been fabricated with optimized dimension and tested. The experimental result of this antenna exhibits UWB characteristics from frequency range 3 GHz to 18 GHz. This corres- ponds to 142.86% impedance bandwidth with center frequency of 10.5 GHz. The experimental radiation patterns of this antenna are nearly omni-directional in H-plane and bidirectional in E-plane. The effect of various design parameters on UWB characteristics have also been analyzed using a 3D electromagne- tic simulator based on FEM method. The simulated and experimental results are in good agreement. The backscattering RCS of this UWB fractal antenna is better than -31 dB throughout the FCC band (3.1 GHz to 10.6 GHz). The proposed coplanar waveguide feed appollian fractal antenna can be easily integrated with radio-frequency/microwave circuitry with low-manufacturing cost and useful for UWB applications. © 2011 Elsevier GmbH. All rights reserved. 1. Introduction UWB technology has attracted much attention for use in short range high-speed wireless communication applications [1]. Antennas capable of operating in ultra-wideband (UWB) and/or multiband communication systems have been one of the primary interests of many researchers in this field. Low profile, compact- ness, simple radiating-element and signal-feeding configuration, good performance, easy fabrication, etc., are important conside- rations in such antenna designs. To operate the communication system with the multiple resonant frequencies, high accuracy in frequency is required to operate the system. Instead of using a multiband antenna, one can use an ultra wideband antenna, in which high accuracy of resonant frequencies are not required. One of the promising researches is antenna theory and design using the fractal concept [2]. Recently, various UWB fractal antennas have been developed for UWB applications [3–7]. In [3], Crown- Sierpinski microstrip antenna is proposed to reduce the size of a Crown square fractal. The frequency notched ultra-wideband microstrip slot antenna with a fractal tuning stub is proposed to achieve frequency notched function [4,5]. Raj Kumar and Mala- thi [6,7] have proposed UWB fractal antenna with CPW-fed by adopting the fractal concept. These UWB fractal antennas are truly ∗ Corresponding author. E-mail address: omnamhshivay2010@gmail.com (R. Kumar). multiband antennas. Their multiples resonances have been conver- ted into wide band characteristics by bringing the resonances frequencies closer and bands overlap. Liu et al. [8] has reported apollonian packing monopole antennas with multiband charac- teristics. The new appollian fractal antenna with CPW-fed and modified ground is proposed for UWB characteristics with detail parametric study in this article. The RCS of this proposed UWB fractal antenna is also neces- sary to study because antenna scattering is the main contribution to the total radar cross section (RCS) of low-observable platforms. Antenna is a special scatter whose scattering is related with its feed port termination [12,13]. With advent of target identification technology, UWB antennas with low RCS become important to the survivability of the antenna platforms [14,15]. It has been widely used for many military applications such as UWB radars, military high data rate wireless communications. This paper presents the unique modified appollian gasket fractal antenna for UWB characteristics with CPW-feed. To achieve ultra- wideband operation, the modified ground plane and the fractal concept are used. The proposed antennas have been successfully implemented. The good impedance bandwidth and radiation cha- racteristics in the operating frequency bands have been achieved. The effect of the various design parameters on the UWB characte- ristics were also studied. The backscattering of this UWB antenna is also studied in term of antenna mode and structural mode scat- tering using 3D-Electromagnetic Simulators HFSS [9]. This antenna has the advantages of lightweight, small size, easy to fabricate and 1434-8411/$ – see front matter © 2011 Elsevier GmbH. All rights reserved. doi:10.1016/j.aeue.2011.12.002