Research On Techniques Of Multi-Beam Forming In Digital Array Radar Based On Linear Power Amplifier

The modern information war requires radar to have high scanning rate, high Doppler and angular resolution and simultaneous multi-function(such as scanning and tracking), as well as the ability of anti-interference etc. Digital array radar(DAR) adopts digital beam forming(DBF) technology on both receiving terminal and transmitting terminal, which enables DAR to change the beam pointing, beam pattern rapidly and form multiple beams conveniently. Those advantages make DAR a perfect device to solve the above problems. So it is of high significance to study transmitting digital multi beam technology. Based on the theory of DBF, this thesis explains the mechanism and the implementation algorithm of transmitting digital multi-beam forming. It also gives the theoretical analyses and matlab simulation results of the engineering problems that would arise during implementation. The following work is done in this thesis:1. The background of digital array radar is given and the history and present state of DAR are introduced to help to understand the great significance of transmitting digital multi-beam simultaneously.2. Based on the theory of DBF, the mechanism of transmitting digital multi-beam is described, along with three implementation algorithms including the digital phase distribution method, the IFFT method and the orthogonal projection method. Detailed analysis has been done to show the advantages and disadvantages of each algorithms.3. The sum-beam power pattern is applied as an important tool to study effect of system parameters on the performance of multi-beam transmitting. The characteristic of each algorithm above is analyzed using the sum-beam power pattern. The results show that the method based on orthogonal projection has better performance in anti-interference. Transmitting coherent signals will produce inter-disturbances while different forms of signals could reduce the damage. Limited bits in digital data processing have bad influence on the transmitting beams. Using more bits usually leads to a better pattern.4. The effects of the channel amplitude and phase error on digital beam-forming and adding-window technique is discussed. The pattern has different distortion features when using different implementation methods. Under channel mismatching condition, the adding-window technique does not work effectively.5. Based on the nonlinear model of power amplifier(PA), how PA influences the transmitting multiple beams is discussed by using theoretical analysis and simulation results. Those work gives technical support for linearization technique. The experiments show that the distortion features caused by memoryless PA is related to the signal forms. While in PA-with-memory, both memorability and nonlinearity have effects on the transmitting signals. And the impact is up to the input power.