Research On Key Technology Of Ubiquitous Radar Weak Target Detection

The transmitted-received beam model of ubiquitous radar belongs to one kind of that models for Digital Array Radar(DAR).It has omnidirectional transmitted beam and the received beams are formed by Digital Beam Forming(DBF).Ubiquitous radar can provide multiple functions for surveillance space continuously,and the core concept is to detect every place for every time.Due to the low gain of transmitted antenna,ubiquitous radar owns low probability of interception,which is important for military research.Because of the characteristics of transmitted-received beam model for ubiquitous radar,the integration time is not limited by dwelling time of beams,and the detection probability of weak target can be improved by prolonging the integration time.However,across range unit(ARU)and Doppler frequency migration(DFM)would occur,which makes troubles for signal processing.Aiming to solve the problems in weak target detection for ubiquitous radar,this desertion carries out the research from the aspect of system design,signal model,methods design for target detection and practical application.The main contents of this dissertation can be summarized as follows:In the second chapter,according to the transmitted-received beam models for DAR,the relationship between ubiquitous radar and DAR is introduced at first.Then,the radar equation is derived for ubiquitous radar,and the features of searching and tracking models is analyzed.Finally,the signal processing flow of ubiquitous radar is provided,and the detection methods for weak targets and their detection standards are introduced.In the third chapter,the target integration and velocity estimation of stepped frequency(SF)waveform are studied for ubiquitous radar.A positive–positive–negative SF waveform is designed and a method for target integration and velocity estimation of SF waveform is proposed based on two-dimensional time-domain cross correlation(2D TDCC).For SF waveform of same stepped direction,another method is proposed based on the Doppler channel correction.The ambiguous function and integration principle are given for SF waveform,and the influence of velocity on target integration is analyzed.Simulations verify the performances of proposed methods on velocity estimation accuracy,computational complexity and stability.In the fourth chapter,the target integration is studied for frequency agile(FA)waveform of ubiquitous radar.For waveforms whose frequency agility is between pulses,a coherent integration method based on coherent integration for same carrier frequency and frequency arrangement is proposed.For waveforms whose frequency agility is between pulses trains,a hybrid integration method based on coherent integration among pulses trains is proposed.The classification and time-frequency analysis are given,the ambiguous function is derived and its feature is analyzed.Simulations verify the performances of proposed methods on detection probability,computational complexity and so on.In the fifth chapter,an outside experiment for wideband ubiquitous radar is introduced aiming of target integration for SF waveform,and a prototype system based on non-cooperative FA external illuminator is introduced.By filed experimental data processing,the effectiveness of signal processing flow and target detection for SF waveform is verified.The field experimental data by prototype system are processed and the results verify the validity and reliability of the signal processing flow for FA waveform.