Doa Estimation In The Mobile Communications Smart Antenna Technology

With the developing of mobile communication, more requirements of its working quality is putting forward. In the Third Generation mobile communication, to develop the using of frequency spectrum , enlarge the capability of the system, expend the radiation of the base station, improve the quality of the communication and reduce the electromagnetic pollution, the concept of Smart antenna was brought forward. From the latest reports, we know that Smart antenna could improve the communication quality of the system obviously, and it has become one of the spotlights of the mobile communication.Smart Antenna has two critical tasks, one is to filter the uplink signals, and the other is to form the downlink beam, and we need adaptive algorithm and digital signal processing (DSP) technology to fulfill these work. Adaptive algorithm is one of the most important technology of Smart Antenna, and it determines Smart antenna's respondent speed to the wanted signal and the complexity of the circuit of the communication system. Consequently, the system should select reasonable algorithms in various communication environment, and algorithm diversity technology could optimize the system to work well. In this paper, we compare some algorithms. Then, we use MUSIC algorithm and DOA matrix method to filter the uplink signals, and get the DOA of the signals, at the same time, we compare the performance of these two algorithms. MUSIC algorithm is the classical algorithm to Spectral analysis, and it has many virtues except that the algorithm need relative time to seek the peak of the signal spectrum. However, DOA Matrix method avoids seeking the peak of the spectrum. Consequently, even the estimating efficiency of 2-D DOA Matrix method is much better than 1-D MUSIC algorithm.In real communication environment, signal transmits with multi-path. So, some general DOA estimating algorithms are invalid, and we should look for some especial algorithm. In this paper, we analysis signal model of multi-path environment, and use high order cumulant method, together with some general DOA estimating method, to estimate DOA of multi-path accurately.In former work, it's easy to neglect the complex mutual coupling between elements of communication antenna. In 3G communication, for the reason of Smart Antenna works, the antenna of communication is much more important. Base Station antenna works in complex environment, in order to improve the performance of Smart antenna, to increase the users of the communication channel and reduce interfere between vary channels, the main lobe of base station antenna should as narrow as possible, and the gain of the antenna should be as high as possible. Moreover, in the application of mobile communication, we change the weights of the antenna to change the main lobe, and then fulfill real-time tracking of the wanted signal. So in this paper, we also analysis the linear array and the circular array. In order to get high gain, narrow main lobe and low sub-lobe antenna pattern, we synthetize the array pattern with Chebyshev method and Unconstrained method seperately.