Dim Target Detection In Airborne Active Electronically Scanned Array Radar

The wide use of stealth technology makes the radar cross section(RCS)of typical military targets,such as aircrafts,missles as well as combat ships,much smaller than ever before.The reflected radar signals from these stealth targets are very dim,and hidden in strong land or sea clutter,which causes a greate challenge to radar detection.In order to enhance the detection performance of airborne radar in complex battlefield environment,major military powers in the world are struggling to develop innovative radar systems,as such airborne active electronically scanned array(AESA)radar.As compared with tranditional mechanically scanned radar,AESA radar has the advantages of flexible beam position,space power combining,versatile waveforms,as well as lower system loss,and thus possesses great potentials for dim targets detection.Chapter 1 is the introduction,which gives the research background,and reviews the development of airborne AESA radars and dim target detection approaches.Chapter 2 discusses several aspects of sytem optimization for airborne AESA radar systems.The key ideas of designing an airborne AESA radar are firstly presented,and then the antenna and processing subsystem as well as work mode are optimized.A method for implementing track and search work mode employing task scheduling and interacting multiple model-probabilistic data association algorithm is proposed,which can satisfy the need for stable and accurate multiple target tracking as well as volume search.As for the AEAS radar resource management,an open,highly modular,and extensible resource management architecture is proposed,which can satisfy the practical enginnering needs.Chapter 3 focuses on dim targets detection based on track before dtect(TBD)methods.A new dynamic programming based TBD method is proposed for dim air target detection,which exploits the information of integrated power as well as number of correlations for target detection,and has enhanced performance of false alarm suppression.In order to enhance the efficiency of TBD methods for dim maritime target detection,a new preprocessing approach is proposed,which make use of the differences of spatial characterisitcs between target and clutter detection cluster,as well as the differences of power spectral characterisitcs between target and clutter.Chapter 4 investigates dim target detection through waveform optimization.An approximate close-form expression for the detection probability of extended targets with regards to the transmitted waveform is first derived,which lay a foundation for waveform optimization.After that,approaches for designing optimal,suboptimal as well asymptotic optimal wavforms for rank-one targets detection are proposed.Chapter 5 investages dim targets detection employing stepped-frequency waveform.Firstly,the parameters of stepped waveform are optimized.Then,the decorrelation of sea clutter and detection performace of maritime target with stepped-freqency waveform is analyzed quantitatively.Simulation results show that the signal to clutter ratio(SCR)is greatly improved through high resolution processing with stepped-frequency waveform.Chapter 6 investigates dim target detection employing frequency modulated stepped-frequency waveform and phase-coded stepped-frequency waveform.The receiver and processing models for frequency modulated stepped-frequency waveform as well as phase-coded stepped-frequency is first studied,and the parameters are also optimized.Then,the detection performance of frequency modulated stepped-frequency in sea clutter is studied.Simulation results show that the SCR is greatly improved through high resolution processing with frequency modulated stepped-frequency waveform.Chapter 7 investigates dim target detection employing frequency-coded waveforms.The characteristics of ambiguity function and matched filter output for Costas and Puhsing frequency-coded waveform are first studied;then,a new pushing frequency-coded waveform is designed by increasing the frequency separation as well as adding linear frequency-modulated signal with appropriate parameters in each subpluse of the original waveform.The new waveform can achieve wider band with the same number of subpulses,and has much lower adjacent sidelobes,which will greatly alleviate the problem of dim targets being masked by sidelobes.