Passive Millimeter Wave Imaging Technology Research

Passive millimeter wave imaging makes use of the electromagnetic thermal emission of the subject and reflected thermal signals from the background. Passive millimeter wave imaging, in comparision to visible or infrared imaging ,has great potential advantage of imaging through fog, clouds, smoke, sandstorms and other poor weathter conditions . Current imaging systems relied on mechanical scanning of a single beam across the scene have problems of low spatial resolution and poor sensitivity. During the past several years, due to significant advances in the development of solid state components and high-speed signal processing technology, multi-beam array imaging systems, which promise an increase in sensitivity and resolution, have received considerable interest in both the military and civilian applications.At first, we present the state-of-the-art of passive millimeter wave imaging technology, and discuss the common theory and principles of it; Secondly, this thesis focuses upon passive millimeter wave imaging based on two-dimension conical mechanical scanning of a single beam. We analyze the the stucture, principles and performance of the system in theory and design the image sample/control interface circuit. In order to improve the low spatial resolution, a super-resolution algorithm-Fuzzy POCS is put forward; At last, we discuss the imaging principles of focal plane arrays, and consider critical aspects of imaging system design. Then we discuss the major constraint factors on array feed elements as well as the character of superheterodyne receiver. And the signal-to-noise ration of focal plane imaging system is analyzed for the performance evaluation.