Research On Passive Millimeter Wave Radiation Imaging Technology For Typical Covered Targets

Radiometer simulation imaging has important research significance in the field of scene detection.It can not only provide theoretical support for the actual radiometer detection work,but also serve as the verification of the detection results.Due to the special and strong penetrability of millimeter wave frequency band,passive millimeter wave(PMMW)imaging simulation has become an important branch of radiometer simulation imaging.At present,the research on imaging simulation of single-layer media has made some progress,but there are few studies on complex scenes with occlusion,and there is no effective solution for the underlying transmission model of simulated imaging.Based on this,the research work of this thesis mainly focuses on the simulation imaging of the layered medium rough surface.This work first proposes a layered rough surface model that is versatile for complex scenes,and then proposes an optimization scheme for the underlying transmission model.Aiming to expand the application range of simulation imaging.The main research results are as follows:1.Based on the basic theory of microwave radiation,the calculation model of common object surface radiation and the basis of type judgment are introduced.The physical characteristics of different object surface,atmospheric radiation and other external influence factors are discussed.Then,the ray-tracing model based on the brightness temperature tracing method and the brightness temperature inversion calculation process are described in detail.2.A hierarchical medium rough surface model is proposed for typical occlusion scenarios.The model takes into account the radiant brightness temperature from the upper layer of the rough surface medium,and it also considers the contribution of the lower layer radiant brightness temperature under the rough surface medium.The effectiveness of the hierarchical medium rough surface model is verified through practical experiments.And through a series of simulation experiments for typical occlusion scenarios,we study the relationship between the factors related to the roughness surface and the radiant brightness temperature in different media and different scenes.3.The characteristics of the bottom transmission model in the layered medium rough surface model are studied in depth.The problems of inhomogeneous ray emission and redundant ray are pointed out in traditional transmission model,and a new transmission model is proposed.We study the variation of the bistatic transmission coefficient and transmission coefficient.And two optimization models are established to improve the accuracy and efficiency of the simulation imaging in hierarchical media rough surface scenes.The two optimization transmission models are effective and correct for simulating multi-layer rough surfaces.