Research And Realization Of DOA Estimation And Correlative Techniques In VHF/UHF Smart Antenna

Smart antenna technology is of great importance to modern array signal processing. It has been widely used in radar, communication, electronic countermeasure and etc. Due to the smart antenna technology has a great performance on the improvement of spectrum efficiency, system capacity, suppression of interference and etc, many researchers and scientific research institutions, from all over the world, have put a high value on it. Under the funding of a pre-research project about communication, the thesis mainly concentrate on DOA estimation and correlative techniques of VHF and UHF Smart Antenna, aiming to meet the requirement of array miniaturization, low expense, instantaneity, high-performance, high maneuverability and etc. The main work of the research is as follows:1. As the spatial spectrum estimation algorithms, which is based on eigen-subspace, requires that the number of source should be less than the number of array. A modified MUSIC algorithm based on the rotation of virtual array has been proposed. The proposed algorithm can increase the receiving array's degrees of freedom through combining the sub-array in series. Hence, the proposed algorithm makes the DOA estimation come true when the source number is greater than the number of array, without having a impact on the original algorithm's statistic performance. The simulation experiments demonstrate the reliability of the algorithm. In a word, it provides a new method of implementation of array miniaturization, low expense and etc.2. Considering the application limitation that the algorithms based on information theory are effective for solving the problems related to white Gaussian noise. Also, diagonal loading technique and Gerschgorin disk method rely heavily on the participation of human. In order to overcome these limitations, an refined algorithm which is based on eigenvalue weighted (SGDE) has been proposed. The proposed refined algorithm makes full use of the similar features in Gerschgorin center and Gerschgorin radii to construct a new Gerschgorin disk with stronger grouping properties by unitary transformation. In addition, a criteria, which can estimate the signal source numbers without the participation of humans, has been proposed. The simulation experiments show that the performance of these algorithms is SGDE>MGDE>GDE, along with the variation of signal to noise ratio, the source number, the spatial correlation factor, the source angle and the source power.3. The research work mainly focus the problem of array calibration and DOA estimation through quantitative analysis, considering the effect of amplitude and phase errors. The classical active correction and WF algorithm are so limited in practical use because both of their performances depend on the accuracy of the prior information. However, the self-correcting algorithm based on Hadamard multiplication can estimate the array errors and DOA at the same time without any prior information and it's independent of phase error. Unfortunately, this algorithm is so complex with low searching efficiency. To solve this problem, this paper not only reduces the effect of the interference factor, but also proposes a new method that transforming two-dimensional searching spectrum into one-dimensional searching spectrum. The proposed method is simple and easy to be realized. Both of the theory analysis and the simulation experiments show that the estimation performance of the proposed algorithm can be as same as the classical MUSIC algorithm's when having two signal source numbers.4. To realize the fast implementation of DOA estimation, the pre-processing unitary transformation of arbitrary center symmetric array is derived and the algorithm process is mapped from the complex number domain to the real number domain; In order to solve the problem of low efficiency of regular iterative and large scale of computing when implementing the eigenvalue decomposition with the classical Jacobi and CORDIC algorithm, a Jacobi parallel optimized sorting algorithm and an iteration algorithm based on CORDIC rotations on the basis of the objective metrics'regularities of maximum distribution and the properties of rotated angle's approximation have been proposed. The proposed method can decrease the computation effectively, and the convergence can be realized quickly. In addition, a one-dimensional spatial spectrum searching algorithm based on the threshold's constraint and a two-dimensional spatial spectrum whole searching algorithm based on digital quantification have been proposed. The two proposed algorithms transform the problem of maxim a searching into the problem of zeros searching and sign query in FPGA. The proposed algorithms greatly reduce the computational complexity, simplify the computation. Thus, they can satisfy the needs of real-time response in engineering.5. In order to satisfy the needs of system's automation and intelligentization, an intelligent signal receiving and processing system for the smart antenna system based on the thought of software radio has been designed, which provides a new method for up-conversion which restores the fixed Intermediate Frequency, and the proposed method is suitable for the system's wide band and high frequency operation. In addition, a control software system for the smart antenna has been designed, which consists of online control subsystem, intelligent detecting subsystem, information store subsystem, offline analysis subsystem and etc. It is flexible and easy to use. Thereby, it not only decreases the expense on maintaining the system, but also decreases the number of operators for the system. The whole proposed design and algorithms for the system have been demonstrated to be feasible and reliable through both of the closed-loop testing and several field experiments.