Research and Development of Millimeter Wave Imaging Technologies

毫米波焦平面成像能够在可见光和红外系统无法使用的情况下通过云层、烟雾和灰尘提供信息。传统的毫米波成像主要依赖于使用单个探测器，通过机械扫描光学器件来获得图像。然而，在成像阵列中使用多个检测器不需要机械扫描，并且使得实时成像成为可能。本研究的目的是开发一种用于成像阵列的元件。该单元由宽带天线、低噪声放大器（LNA）、检波器和低通滤波器组成。毫米波光学成像的发展也很重要。本研究的主要结果如下：1.考虑到大气衰减是毫米波频率的函数，对被动成像阵元进行了理论分析，给出了所需的阵元特性，实验频率为35 GHz.采用光线追迹法设计了具有较小像差的毫米波光学系统。使用聚乙烯制成直径为500 mm的非球面透镜。研制了具有费米-狄拉克函数锥度曲线的宽带渐变缝隙天线（专利申请中）. LNA的35 GHz频段的设计和建造使用市售MMIC的有一个放大器的40 dB增益和7 dB NF。使用成像元件，在35 GHz频段成功观察到天空、建筑物和树木等户外场景以及面部和手部等人体。毫米波被动成像的应用包括机器人传感器穿越火焰、地雷探测等。

Millimeter(MM) wave focal plane imaging is able to provide information through clouds, smoke, and dust when visible and IR systems are unusable. It can also be used in the fields of plasma measurement remote sensing, etc. Conventional millimeter wave imaging relies mainly on the use of a single detector, with the optics mechanically scanned to obtain an image. The use of multiple detectors in an imaging array, however does not require mechanical scanning and makes real-time imaging possible. The object of this research is to develop an element for the imaging array. The element consists of a wide-band antenna, LNA (Low Noise Amplifier), a detector and a low-pass filter. The development of MM-wave optics to form images is also important. The results of this research are as follows :1. Considering atmospheric attenuation as a function of frequency of MM-waves, theoretical analyses for passive imaging array elements have been performed to give required characteristics of the elements and the frequency for the experiments to be 35 GHz.2. The ray-tracing method was used to design MM-wave optics with less aberration. An aspherical lens with a diameter of 500 mm was made using polyethylene.3. A wide-band tapered slot antenna with the taper curve of Fermi-Dirac function was developed for the elements (patents pending).4. LNA's for the 35 GHz band have been designed and constructed using commercially available MMIC's to have an amplifier of 40 dB gain and 7 dB NF.5. Using the imaging element, outdoor scenes such as sky, building and trees and also human body such as face and hand have been successfully observed at the 35 GHz band. The applications of the MM-wave passive imaging include robot sensors through flame, detection of land mines and so on.