| People do research on millimeter wave imaging technology mainly because of its penetration ability to image the hidden objects under bad environment while optical imaging systems can’t. As the key component of millimeter wave imaging system, millimeter wave antenna has a great influence on the performance of the whole system and it is a significant target to develop the special resolution.In this paper, the millimeter wave dielectric lens antenna is studied systematically, and the main research work including the analysis of millimeter wave radiation theory, the design of millimeter wave dielectric lens, the research about focus characteristics and the antenna array on the focal plane of the lens. Specific works are as follows.Firstly, we redefine the half-power spot size of the lens antenna feeding as special resolution. And the spot size is the minimum size which the lens antenna can tell. Then we design two kinds of lens antenna:one is the traditional one, Hyperboloid-double convex lens antenna, which is proved that cannot satisfy the demanding of the system. The other one is the even-order aspherical - double convex lens antenna which is based on the optical imaging, it could solve many problems such as big focal spot and poor partial coke. What’s more, its spatial resolution spot size is 2.9 cm and feed gain difference is less than 1dB and it could meet the demanding of the imaging system experimentally.Secondly, three forms of feed antennas on the focal plane of lens are analyzed and compared. They are pyramidal horn antenna, conical horn antenna and tapered slot antenna. The gain are 16.3dB,14dB,16dB and the side-lobe level are - 17dBc,-20dBc and -16dBc, respectively. All of them have good symmetry of the main lobe and achieve the miniaturization. According to the antennas’ electrical properties, mechanical properties and processing cost, the final choice is the pyramidal horn antenna.Finally, the radiometer system is able to distinguish an object with a size of 2.5 cm*2.5 cm and the system’s field range is 70 cm* 190 cm at S0=3000 mm. |
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