太赫兹微弱信号检测系统噪声处理方法研究

Analysis and processing of noise in weak terahertz signal detection system

为了能够量化物体太赫兹辐射的大小,对黑体辐射中的太赫兹信号进行测量,使测量系统处于真空状态下,并且使用液氮制冷来屏蔽外界杂散辐射。黑体辐射的太赫兹信号由卡塞格林系统聚焦于探测器上。探测器的输出信号用锁相放大器进一步处理,并观察不同时间常数下锁相放大器的输出信号。实验结果表明:当黑体温度为323k时,实验装置使用液氮制冷前后的测量结果有所不同,前后相差约3μv左右。时间常数对输出结果影响也很大,实验使用3s比较合适。由于噪声来源复杂、噪声水平很高,黑体在太赫兹波段辐射能量极为微弱,所以系统对温度分辨率要求不是很高。

In order to quantify the terahertz radiation of objects, the terahertz signals in black- body radiation were measured. All measuremerits were conducted in vacuum circumstance, with liquid-nitrogen refrigerating to avoid any outside stray light. Meanwhile, those terahertz signals were focused on a detector by Cassegrain telescope. Afterwards, the output signals were further analyzed by a lock-in amplifier, and were compared with each other in different time constants. Results suggested that, with a constant temperature of 323 K, the measure- ments before and after liquid-nitrogen refrigerating were different with a discrepancy of about 3 μv. Moreover, the time constant also had a great influence on the experimental results, with 3 s most appropriate in this study. However, due to the complicated noise sources and high noise levels, the radiation energy of the blackbody was too weak, and made the temperature resolution of the detection systems very low.