International Journal of Research and Reviews in Wireless Communications (IJRRWC) Vol. 1, No. 3, September 2011, ISSN: 2046-6447 © Science Academy Publisher, United Kingdom www.sciacademypublisher.com 50 A Novel Design of Phased Antenna Array Based on Digital Beamforming Ridha Ghayoula 1 , Najib Fadlallah 2 , Bertand Granado 3 , Ali .Gharsallah 1 , and Mohamed Rammal 2 1 Faculty of Mathematical, Physical and Natural Sciences of Tunis, Department of Physic, El Manar University, Tunisia 2 RADIOCOM Team, High Institute of Technology Saida, Lebanon 3 ETIS-ENSEA, Cergy-Pontoise University, Paris-France Email: ridha.ghayoula@fst.rnu.tn Abstract –The phased antenna array consists of a combination of multiple antenna elements with a signal-processing capability to optimize its radiation and/or reception pattern automatically in response to the signal environment. In a telecommunication, the phased antenna array is the port through which radio frequency (RF) energy is coupled from the transmitter to the environment and, in reverse, to the receiver from the environment. In this paper, a novel design of phased antenna array based on digital beamforming is proposed. The goal of the design is to construct smart antenna beamforming systems with hardware-software implemented neural network. A newly proposed synthesis method is used to design antenna arrays capable of delivering a much better radiation performance in terms of homogenous coverage and reduced interference with phased arrays and capable to beamforming and electronic steering by adjusting the relative phases of the signal received or transmitted by each antenna. To verify the performances of the proposed technique, an 8-element array has been realized and tested for various types of beam configurations. Keywords – Neural network, back-propagation algorithm, synthesis method, phased antenna array, Steering beams, multiple steering, Interference nulling 1. Introduction IN RECENT years, wireless communication systems have progressed greatly and the market, especially for the cellular phone, has witnessed explosive growth. Moreover, as the demand for multimedia services increases, a wider bandwidth of information will be required for next generation wireless systems [1]. These systems will be allocated at a higher frequency band because a number of useful frequency bands have already been allotted to and are occupied by existing systems. In order to accommodate a larger number of subscribers and to provide better quality services, it is necessary to increase the channel capacity. Further, the technologies required for power saving and efficient frequency reusability will be necessary for various multimedia services. The efficient use of the frequency resources is necessary to achieve higher data transmission throughput. Smart antenna systems are capable of automatically changing the directionality of their radiation patterns in response to their signal environment. This can noticeably improve the performance characteristics, such as channel capacity and quality of a wireless system. Smart antenna systems, by using spatially separated antennas, referred to as antenna array, maximize the Signal-to- Interference-plus-Noise Ratio (SINR) of the received signals, and suppress interferences and noise power by digital signal processing after analog to digital conversion [2]. Conventional antenna systems, which employ a single antenna, radiate and receive information equally in all directions. This omni-directional 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. Interference and noise reduce the Signal-to-Noise Ratio (SNR) used for detection and demodulation, resulting in poor signal quality. Today‟s cellular systems usually introduce 120 ◦ sectorization of the coverage to enhance capacity [3]. On the other hand, smart antennas at the transmitter are capable of steering the maximum radiation pattern toward the desired mobile at the receiver; they can spatially separate the energy of the interference [4-6] and mitigate multipath fading using a software algorithm. This ensures that an optimum quality of service is delivered to users, and it provides maximum coverage for a base station. Smart antennas can use spatial domain processing by using multiple antennas, thus enabling them to have intelligence to process the data at both receiver and transmitter [9]. The smart antennas are often classified as switched-beam arrays and adaptive array antennas. The switched-beam arrays comprise beamforming networks and a beam selection processor. The processor selects the beam with maximum power response by switching the beams. However, the adaptive array antennas incorporate more intelligence than the switched beam arrays. Adaptive array antennas can estimate their environment in accordance with the propagation channel responses between the receiver and the transmitter. This information is then used to weigh the data received at/transmitted from the antenna array to maximize the response for the desired user. The processor determines the optimum weight vector. In [3] the author‟s describes prototyping of a neuroadaptive smart antenna beamforming algorithm using hardware-software implemented RBF (Radial- Basis-