Research On Key Technology Of Array Signal Processing

After decades of advance in array signal processing, there are numerous research achievements. However in realistic application, there are still many key problems are to be solved. For example, antenna array structure design, direction finding for weak signal, beamforming, calibration of mutual coupling and channel errors, these problems are still hard to be solved. Especially when using satellite platform to sense the weak signal on the ground, we are facing many problems such as limitation of the number of array units, limitation of the area and the shape of the platform for array disposing, limitation of the radius of the minimum unit, weakness of the received signal, the difficulty of emendation of mutual coupling and channel errors. We have to optimize the design of the array structure for satellite carrier, research the direction finding and beamforming method for weak signal based on the array structure, amend the mutual coupling and channel error according to the impact of the direction finding and beamforming, thus we can improve the receive sensitivity and the precision of direction finding. In this dissertation, several key techniques in array signal processing such as the collocation and optimization method of the antenna array, direction finding method, digital beamforming and array calibration method are to be studied. Several novel and valuable algorithms were proposed and derived in the dissertation, computer simulation validated their efficientness. The main contributions and innovations of this dissertation are as follow:1. Based on the micro-genetic optimization algorithm and the particle swarm optimization algorithm, the array collocation and optimization methods are studied, one dimensional nonuniform linear array, seven arm circle array and modified seven arm circle array are designed. We synthesized, analyzed and simulated the performance of the one dimensional nonuniform linear array, seven arm circle array and modified seven arm circle array, the synthesized and simulation results are given. The simulations show that the seven arm circle array owns the lowest sidelobe level in the same condition.2. The MUSIC algorithm based on twice organized array is proposed, this algorithm chooses multiple subarray in the array as subarray set, thus improving the array gain for the whole array by crossing or overlapping the subarrays, and realize the direction of arrival(DOA) estimation for weak signal. Combining with seven arm circle array and modified seven arm circle array, we simulated the the direction finding algorithm, the simulation validated the efficiency of the algorithm. The circular array received 2D-DOA separable estimation method based on twice virtual interpolation is proposed. This method interpolated the circular array twice, according to the shift invariance of the two interpolated virtural circular array, we can obtain the estimation of the azimuth and elevation by using ESPRIT and MUSIC algorithm respectively. Computer simulation shows that the performance of twice interpolation is superior than single interpolation.3. Single beam forming methods which based on covariance matrix load, amplitude weighted using generalized linear combination are studied. The amplitude weight method is designed. We simulated these beamforming algorithms based on seven arm circle array, simulation results shows that we can get lower sidelobe in wider band by using circle amplitude weighted method. Beamforming method based on particle swarm optimization algorithm is proposed. This method is easy to realize, can improve the computation efficiency greatly. From the simulation, we can see that the performance of this algorithm is as good as SMI algorithm, when there is channel error, the algorithm can also be convergence efficiently. Parallel and linearity restriction multiple beamforming method were studied respectively. The simulation is based on seven arm circle array, the simulation validated the efficiency of the two algorithm, they can beamform efficiently, and can separate multiple signals.4. The array output model and array calibration problem are studied in presence of mutural coupling, a new active array calibration algorithm is proposed to solve the problem of mutural coupling. This algorithm is based on uniform circular array. It is suitable to calibrate the array when multiple sources exist.