| Compare with analog multi-beamforming, array antenna element can be used repeatedly to form different beam with no falling SNR(signal to noise) in digital beamforming system, which has the capabilities of Beam steering agility, self-tuning and low side lobe, adaptive beamforming to realize spatial domain anti-jamming and nonlinear process method to improve spatial resolution. Base on these advantages, digital beamforming technology bring far-reaching influence to improve the radar capability.After decades of advance in digital beamforming and DOA estimation technology, there arc numerous research achievements. However in realistic application, there are still many key problems to be solved. For example, antenna array structure design, direction finding for weak signal, beam forming, calibration of mutual coupling and channel errors, these problems are still hard to be solved.The main contributions of this dissertation can be summarized as follows:1) Array signal processing model is studied and the method of time domain wide-band digital beamforming technology is researched. Based on array signal receive model, FIR filter with specific frequency response is designed and the capability is validated by the simulation result.2) Spatial smoothing-rank sequence method to the number of signal estimation and general MUSIC method to DOA estimation are analysied. The application of these methods for spatial spectrum estimation is studied. The decorrelation method is analysied, and the decorrelation capability is validated by the simulation result.3) An algorithm of wide-band multichannel calibration based on adaptive equalization is studied. The digital filter is synthetized by means of self-adaptive filtering principle,solving amplitude variation and phase shifting mismatching among receiver channels precisely. The influence of these mismatching to the capability of beamforming and DOA estimation is simulated by computer. The simulation results show that the calibrating algorithm is effective. 4) Engineering implementation for DOA estimation system based on wide-band digital beamforming is studied. Time domain wide-band beamforming method is adopted and the work flow and Operating Principle are introduced. The design is optimized to array antenna and array signal processing subsystem.5) The testing and calibration method for large scale fixed array is studied. Beam Pointing and pattern for real antenna is measured and calibrated on the antenna testing ring platform. The engineering feasibility is validated by the direction finding experimentation in real signal field environment. |
PDF Full Text Request