太赫兹雷达散射截面的仿真与时域光谱测量

Simulations and time-domain spectroscopy measurements for terahertz radar-cross section

太赫兹时域光谱技术在安检、无损检测、生物医学等领域有广泛的应用,而其在雷达目标特性领域的应用一直存在诸多争议.针对目前太赫兹时域光谱雷达散射截面定量测量的难题,本文基于太赫兹时域光谱技术搭建了太赫兹时域光谱目标散射测量系统,利用该系统测量了金属球、金属圆盘、金属圆柱等典型定标体在0.2-1.6 THz频段内的极窄时域脉冲回波,数据处理后得到了各定标体的雷达散射截面,与理论数据对比验证了系统测量结果的精度.在此基础上,测量了太赫兹频段电大尺寸复杂目标的雷达散射截面,并将表面积分方程法与多层快速多极子算法相结合对目标的雷达散射截面进行了数值计算,测量值与理论值达到了较好的一致性.研究结果为太赫兹时域光谱技术在太赫兹目标特性领域的应用奠定了基础.

Terahertz time-domain spectroscopy technology has a wide range of applications in security inspection,nondestructive testing, biomedical, etc. But its application to target characteristics has been under debates,because there exist so many differences between terahertz continuous wave and ultra short pulse wave(single pulse width about 1 ps). For investigating the problem of quantitatively measuring the terahertz radar cross section, in this paper, a terahertz time domain spectroscopy scattering measurement system is built based on the technology of terahertz time domain spectroscopy. After system optimization and error minimization of location and system, time domain echoes of targets, such as sphere, disk, cylinder and complex targets, are measured. After the process of fast Fourier transformation and calibration, radar cross sections of the abovementioned targets in a frequency range of 0.2 –1.6 THz are calculated. Furthermore, the surface integral equation method and multilevel fast multipole algorithm are used to simulate the radar-cross section(RCS)results. The measured radar cross section results are compared with the simulations, and their error is less than 3 dB. The error arises mainly from the location and uneven distribution of terahertz wave on quiet zone.Generally, it is acceptable though there is still much work to do. The accuracy of RCS measurement of terahertz time domain is varified. All those are progressing in terahertz time domain spectroscopy technology used in target characteristics. Moreover, the methods of improving dynamic range in high frequency and enlarging quiet zone are the focus of follow-up studies.