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Tham khảo tài liệu 'advances in satellite communications part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 184 Advances in Satellite Communications 4. Adaptive antenna array Adaptive antennas can be described as systems usually based on three main parts the antenna array the receiver architecture and the beamforming scheme. Thus adaptive antennas have those advantages owing to those three main parts. The system capabilities increase as complexity and development cost do. Furthermore since signal processing is the basement of the adaptive antenna concept it is important to analyze the design challenges in terms of hardware architecture and components such as processors and embedded systems. The antenna array provides the capability of performing the antenna pattern meeting the environment requirement under study. Besides receiver architectures have some interesting advantages depending on the implemented receiver arraying technique such as signal to noise ratio SNR and bit error rate BER performance enhancement. Furthermore symbol synchronization and carrier recovery can be used increasing the receiver complexity but providing higher performances. Finally beamforming schemes use multiple antennas in order to maximize the strength of the signals being sent and received while eliminating or at least reducing interference as discussed in Section 4.3. Adaptive antenna arrays are often called Smart Antennas because they have some key benefits over traditional antennas by adjusting traffic patterns space diversity or using multiple access techniques. The main four key benefits are First enhanced coverage through range extension by increasing the gain and steering capability of the ground station antenna Second enhanced signal quality through multi-target capability and reduction of interferences finally adaptive antennas improve the data download capacity in the ground segment of satellite communication by increasing the coverage range Martínez et al. 2007 . 4.1 Design and architecture based on software defined radio For design there is the well known waterfall life cyclic .