Research And Implementation Of Direction Finding Algorithm Based On Multi-baseline Interferometer

With the deepening of the digital era,electronic warfare has gradually evolved into the main form of military warfare between countries,advanced and safe electronic reconnaissance technology has become a major development hotspot in the military field,passive positioning technology has also developed rapidly in recent years.In the passive location technology,there are many kinds of direction finding methods for enemy incoming signals.Most of the corresponding algorithms are implemented by software and embedded in our own countermeasure system.With the increasingly demanding real-time requirements of direction finding algorithm in the industry,the pure software implementation can not meet the speed requirements.Facing this deficiency,this thesis proposes a hardware implementation scheme of broadband digital receiver solution module based on multi baseline phase interferometer direction finding algorithm,which is implemented and tested on FPGA.The main contents of this thesis are as follows:Firstly,the structure of passive direction finding system and the most basic interferometer direction finding algorithm are introduced in detail.Aiming at the phase ambiguity problem in direction finding,two common multi-baseline interferometer direction finding methods in the industry are introduced: correlation interferometer direction finding and phase interferometer direction finding.According to the project requirements,this thesis selects the virtual baseline direction finding method of phase interferometer direction finding method as the theoretical support of module design.In addition,the antenna array arrangement method corresponding to virtual baseline direction finding method is introduced in detail,and the antenna array parameters that meet the requirements of the project are calculated.Secondly,this thesis shows and introduces the antenna array and system design index selected by the subject.Based on Matlab,the virtual baseline direction finding method is implemented by software,and the feasibility and rationality of the algorithm are preliminarily verified.Thesis has pointed out that the software can not meet the real-time requirements of the subject,and the necessity of hardware acceleration is clear.In addition,four experiments are used to analyze the effects of the total number of single sampling points,SNR,incoming frequency and incoming direction angle on the correct ambiguity resolution probability and direction finding error of the system.In addition,based on the shortcomings of the original software implementation scheme,this thesis puts forward specific improvement schemes from the perspective of algorithm implementation and algorithm function,so as to improve the ambiguity resolution efficiency of the algorithm and increase the frequency and direction finding calculation ability of the algorithm for pulse incoming waves.Finally,this thesis discusses the feasibility of the algorithm when a variety of incoming signals are incident.Subsequently,this thesis describes in detail the design scheme of the solution module of broadband digital receiver designed in this topic.The Broadband digital receiver module is divided into four parts: preprocessing module,transform processing module,frequency measurement module,direction finding and solution module and serial communication module.They are responsible for converting the output data of ADC subboard into sampling signal data,FFT processing the sampling signal of each channel to get the frequency and absolute phase of sampling signal of each channel,and calculating the frequency and direction Angle of incident wave.Finally,the data interaction between FPGA and PC is completed.This article also introduces the format of the result display on PC.Finally,the broadband digital receiver solution module designed by the subject is simulated and tested based on waveform.By comparing the simulation results with the software solution results,it is proved that the hardware system meets the preset index requirements of the subject.The feasibility of the module is verified by the combination of wired test and wireless test.