Research On Millimeter Wave Radiometric Characteristic And Imaging

Owing to practical application value and extensive potential application,the millimeter wave radiometric imaging technology is widely used in remote sensing, guidance, industry, medical science, public security, environmental monitoring and etc. However, the millimeter wave radiometric images possess low spatial resolution and have near operating distance because of the confinement of the antenna aperture size. Comparision to 8mm waveband research, 3mm waveband radiometric characteristic, imaging mechanism and methods of improving image resolution are studied systematically and the millimeter wave application research on metal objects is carried on in this paper. The main research work is shown as following. 1) 8mm waveband typical plane targets radiometric characteristic database consists of 8mm waveband radiometric data that was measured by the microwave remote sensing laboratory of Huazhong University of Science and Technology in 1982-1983 and 1994-1995. As the further research, this paper carries on the radiometric characteristic measurement and the model building in contrast to 8mm radiometric data of plane targets. The data modeling method adopts the least square cosine polynomial and cubic spline interpolation. The conclusion that 3mm objects'brightness temperature is usually higher than 8mm's is given. The theoretical calculation model is verified by inversion of the 3mm measurement data. The relationship of polarization mode and roughness degree was analysed qualitatively. Under the condition of lack of inland literature, 3mm radiometric data measurement and research can surport the national defence and science research. 2) Millimeter wave radiometric imaging has the merit of direct-viewing and easy target recognition. 3mm radiometric imaging research begins in our country in the near years. This paper studies on the radiometric imaging mechanism and analyses the imaging parameters. A set of MCU-PC controlled radiometric imaging system was developed. Furthermore the methods of the soft integration and the morphological composite structure shape filtering are used to improve image quality. Comparison to 8mm radiometric image, it does verify the spatial resolution that 3mm image has higher spatial resolution. Our 3mm radiometric imaging research has advanced technology in the country. 3) The Multiple-sensor image fusion is one of the researchful hotspot at present. The image fusion has involved in optical images, infrared images and radar SAR images but fewer involved in radiometric images. The millimeter wave image fusion with other higher image can acquire more useful information and premote the exactness rate for the scientific decision. The theoretical means and technical realization of image fusion is a significant working. This paper is the first tryout for the fusion by the millimeter wave image and the optical image. The simulation radiometric image from optical image and the millimeter wave image fusion model is presented to improving the low-resolution millimeter radiometric image. 4) The millimeter radiometric restoration and the millimeter data inversion are compatible. The low-resolution millimeter wave image restoration is an important task in the paper. According to the millimeter wave imaging mechanism and antenna pattern, we try out the image rebuilding, the image enhancement, the image restoration and the wavelet-based super-resolution methods and get satisfying results. These all will support the further research work, especially in the restoration by the antenna pattern. 5) As one of the applied research of the paper, the radiometric characteristic of metal targets is used to carry on terminal guidance. Because the concealed body technology based on radar has got huge advancement. Thus passive detection and ranging technology is the research hotspot at present. A passive millimeter wave radiometer can be used in guidance and tracing by the antenna temperature contrast that represents the power change quantity. According to the shrinking ratio simulation measurement theory, this paper measures the metal target and analyses the antenna contrast, signal characteristic and positioning method. It draws the conclusion of 3mm radiometric detection superior to 8mm's detection effect under the condition of the approximate sensitivity. In general, 3mm and 8mm radiometers in the experiments are developed by our laboratory. And their working center frequencies are 94GHz and 35GHz. All of the research contents are developed by 3mm and 8mm radiometric characteristic, radiometric imaging, image processing and practical application. In spite of giving some results, there are some shortcomings such as the quantized evaluation mechanism of the fusion images and the super-resolution images. The new idea and the new methods need further improving and come to perfection.