Electrical and Electronic Engineering 2013, 3(3): 86-95 DOI: 10.5923/j.eee.20130303.02 Circular Array with Central Element for Smart Antenna Anouar Dalli 1,* , Lahbib Ze nkouar 1 , EL Fadl Adiba 2 , Mohamed Habibi 2 , Seddik Bri 3 1 Laboratory Electronic and Communications, Engineering Mohammadia School Mohamed V University, Rabat, Morocco 2 Laboratory Systems and Telecommunications Engineering Decision, Ibn tofail University Sciences Faculty, Kenitra, Morocco 3 Materials and Instrumentations group, High School of Technology: ESTM Moulay Ismail University, Meknes, Morocco Abstract Numerous studies of smart antennas have already been conducted using linear or planar arrays, not as much effort has been devoted to other configurations. The performance of s mart antennas with circular array and circular array with central element are examined and simulated in C-band (4–8 GHz). In this paper, the first module presents the design of circular antenna array with central element suitable for beamforming technique in wireless applications. A circular arrangement of eight circular sector microstrip antennas is proposed, a central element was added to array to increase steering capability of proposed array. The second module suggests a MUSIC (MUltiple SIgnal Classification) to accurately estimate the DOA (Direction Of Arrival) of the signal of interest, and LMS algorithm for beamforming technique to concentrate the power in the desired direction and nullify the power in the interferer direction. The modelling and simulation of antenna array is computed using HFSS. The beamforming algorithm is designed in Matlab. Keywords Smart Antenna, Circular Antenna Array, Array Factor, MUSIC, DOA, LMS 1. Introduction Since the beginning of the twentieth century, antenna designers have investigated different antenna architectures to meet the requirements of communication systems. A large variety of antennas have been developed to date; they range from simple structures such as monopoles and dipoles to complex structures such as phased arrays. A detailed study of circular sector patch antenna is presented in[1]. This antenna has interesting dimension, so it can be integrated easily in antenna array. Recently , Smart antenna[2-3] have received increasing interest for improving the performance of wireless radio systems, their application has been suggested for mobile-communications systems, to overcome the problem of limited channel bandwidth, satisfying a growing demand for a large number of mobiles on communications channels. However Conventional Antenna systems, which employ a single antenna, radiate and receive information equally in all directions. This unidirectional radiation leads to the distribution of energy in all directions. This Wasted power becomes a potential source of interference for other users or for other base stations in other cells. On The other hand, smart antennas consist of an antenna array, combined with signal processing in both space and time, they are capable of automatically changing the directionality of their radiation patterns in the response * Corresponding author: anouar_dalli@yahoo. fr (Anouar Dalli) Published online http://journal.sapub.org/eee Copyright © 2013 Scientific & Academic Publishing. All Rights Reserved to their signal environment so they basically attempt to enhance the desired signal power and suppress the interferers by beamforming toward the DOA (direction of arrival) of the desired signal and null steering in the case of the interferences. The smart antenna systems can be divided into two categories. These are: switched beam system, and adaptive arrays. In this paper adaptive arrays are investigated and used for smart antenna model. MUSIC[4-5] algorithm is high resolution and accurate method which is widely used in the design of smart antennas. MUSIC is based on exploiting the eigenstructure of input covariance matrix. Our smart antenna will be designed using a circular sector microstrip antenna. This antenna was studied in [1]. A circular arrangement of eight circular sector microstrip antennas is proposed, then we added a central element to array to increase steering. This paper is organized as follow: Design and simulate of circular sector patch elements and arrays are presented in section II. In section III, DOA estimation algorithm is developed. Then, the DOA algorithm supplies this information to the beamformer to orient the maximum of the radiation pattern toward the SOI (Signal Of Interest) and to reject the interference by placing nulls toward their direction, followed by the conclusion. 2. Antenna Design 2.1. Single Element Design Figure 1 shows the architecture of the proposed antenna. It is a circular sector antenna fed by microstrip line. The