The Study On Direction Of Arrival Estimation In Smart Antenna

With the fast development of telecommunication, the newly rising theories and technologies are applied to achieve the higher quality communication and service including smart antenna. Smart antenna takes advantages of the differences among the transmission directions of the signals to separate signals with same frequency and time slot. It can enlarge the communication capability enormously and be combined with other reusable technologies to make full use of the limited spectrum sources. Besides, it can also restrain the fading effects to improve the communication quality. But the precondition that smart antenna can achieve directional transmission is the DOA estimation of the signals can be got correctly. So the purpose of this paper is to use spatial spectrum estimation theories to get DOA estimations.Spatial spectrum estimation is a very important research direction of array signal processing which develops based on spatial filtering and time domain spectrum estimation. The biggest characteristic of spatial spectrum estimation is algorithms. On the basis of deep understanding of the algorithms, the application of spatial spectrum estimation could be realized. In this way, this paper studies and analyzes some of the algorithms and makes improvement according to the feature of the array. The contents are as follows:Firstly, the paper gives the introduction of the background and significance of the research area as well as the history and the development now of spatial spectrum estimation;Secondly, the basic principles of smart antennas are introduced including concepts, structures, classifications and so on. Then the basic knowledge of spatial spectrum estimation is studied, especially the array models, expressions and second-order statistics. These are the bases to realize effective DOA estimations;Thirdly, the paper focuses on the most common array-ULA. Making use of spatial spectrum estimation knowledge, the paper introduces several DOA estimation algorithms, and makes comparisons and analyses among different algorithms from the angles of signal and noise ratio (SNR) and the correlation;Fourthly, the paper also studies another important smart antenna array-UCA. Compared with ULA, UCA has many advantages, but also some disadvantages for DOA estimation because of its complicated array manifold. The paper studies several DOA estimation algorithms for UCA. What's more, according to the feature of UCA, improvement is made to UCA-RB-MUSIC algorithm and the interpolated array transformation is used to realize UCA shifts to get DOA estimations. Simulations show the effectiveness of these algorithms.At last, the plan for next step is made based on the summarization of the paper.