Study On Some Critical Technologies For Smart Antenna Systems

By direction of arrival (DOA) algorithm, smart antenna system can make clear the space diversity of the signals, interferences and noises. Considering the spatial diversity of signals, and with beamforming algorithms, the system can form a radiation pattern that can set high gain in the useful signal directions and much lower gain in the interferences directions through digital or analog method. It owns the advantages that, in the multiple signals environment, those signals will not interfere with each other, decreasing the impact of outer interferences and noises, saving the radiation power, decreasing the pollution of electromagnetic radiation and high level of information security. The smart antenna system is expected to be a mainstream antenna applied in the 3G/4G communication systems and can also be expected to be used in the advanced radar system ( e.g. Phase array antenna). In this paper, we have studied the wireless channel model and the signal model for smart antenna and we also investigated the beamforing algorithms and multiple beamforming algorithms and its performance in the anti-interference environment. Furthermore, we investigated the algorithm for wide-band signal beamforming.UWB technology is a non-carrier wave telecommunication technology. It is the most advanced technology for communication systems that work at frequencies above 1GHz and is considered to be one of the hottest pots in the telecom area in five years. The UWB system contains some advantages below: easy to be implemented, high data transferring speed, lower energy consuming and higher level of information security and etc. As its broad application in the communication and radar systems, a lot of the countries take it as an important research area. When applied to the smart antenna system, it can not only improve the data transferring speed and achieve impulse transfer but also can make good use of the high gain of the smart antenna system and the high level of information security of the UWB antenna, thus the performance of the system can be highly improved. In this paper, we investigated the theory of UWB antenna and some design principles. And we designed a kind of multiple notched UWB antenna with etching slot SRRs in the printed copper of the patched antenna that can avoid the impact of the interferences in two narrow bands and paved the way for its anti-interference applications in the smart antenna system.Metamaterial is a new kind of material, it is produced by artificial methods and can perform novel optical or electromagnetic characteristics that not exist in the natural materials. It owns some traits like negative refraction index, transferring backward waves, a different dispersion curve as normal materials and its transferring character can be electronically controlled by adding varactors in its structure. It can be used to implement novel leakage wave antenna and microwave devices that can be applied to novel smart antenna system. We have investigated the tuning theory and performances of the radiation angle and beamwidth of a metamaterial-based electronically controlled CRLH transmission-line structure works as a novel leaky wave antenna.My dissertation firstly investigated the above technologies for smart antenna systems and made use of all the advantages of each technology in order to find out the future possibility for the smart antenna system development. It also aimed to make them better serve in the future wireless telecommunication systems.