Research On Key Technology Of Airborne MIMO Radar

Airborne MIMO radar,which used the MIMO technology in the airborne radars,it can implement air reconnaissance,topographical surveying and other functions.Inspired by the thought of MIMO communication,MIMO radar is known for using a plurality of antennas simultaneously transmit different waveforms and a plurality of antennas simultaneously receive the reflected signal.It has obvious advantages in mitigating the decline,enhancing resolution and suppressing interference and so on.Investigate the underlying cause of its advantages,MIMO radar break the traditional phase array radar by transmitting coherent signals to improve the limitations of coherent processing gain,transmit orthogonal signal in transmitter to achieve the spatial diversity.This paper focus on how airborne MIMO radar reflects its advantage,how airborne MIMO radar forms its beam and designs its orthogonal waveform.Firstly,this paper studies and analyzes the principles and characteristics of MIMO radar.Analyze some advantages of MIMO radar compare such as anti-clutter,anti-interference and low probability of intercept(LPI).Secondly,this paper proves two kinds of receivers have the same receiving effects in the transmitting diversity MIMO radar's narrowband signal.Based on the research of MIMO radar's beam forming principle,derives the optimum weight vector expression of static MIMO radar beam and adaptive beam.Finally,the simulation results prove the feasibility of the expression.Furthermore,this paper proposes adopting hybrid genetic algorithm(GA)to design orthogonal poly-phase codes signals.The design principle is same,but the key is how to define and optimize the cost function to search the satisfactory orthogonal code.Based on the study of orthogonal poly-phase codes signal model and genetic algorithm basic operating procedures,apply iterative optimization method.First search a group of better orthogonal code and corresponding weight vectors through genetic optimization algorithm,then optimize this group of better orthogonal code to search a group of much better orthogonal code signal,simulation proves the effectiveness of the optimization algorithm.Analyzes the impact of transmitting signals' incomplete orthogonal,proposes through mismatched filtering to reduce the side-lobe gain and Doppler frequency compensation to improve the detection probability,simulation experiments show that the method is effective.Airborne MIMO radar tends to work on the looking-down state,the echo is doped with a large amount of ground clutter.When the MIMO radar is operating in strong clutter,the radartarget-detection-performance will be greatly affected,therefore study the airborne MIMO radar's ground clutter characteristics at the last part of the paper.