采用CMOS太赫兹波探测器的成像系统

Imaging system based on CMOS terahertz detector

太赫兹波成像技术在生物医疗和安全检测等领域具有广阔的应用前景。针对新一代信息技术对便携式太赫兹波成像设备的需求,设计了基于CMOS太赫兹波探测器的成像系统。该系统包括一款CMOS太赫兹波探测器、片外模数转换器(ADC)、FPGA数字信号处理器、二位步进机、四个抛物面镜和太赫兹波辐射源等。CMOS太赫兹波探测器集成了片上贴片天线以及作为检波元件的NMOS晶体管,探测器由180 nm标准CMOS工艺制成。太赫兹波探测器的输出被片外模数转换器(ADC)采集并转换为数字信号,该数字信号被FPGA采集并传输到电脑上成像。所有上述元件均被装备在印刷线路板(PCB)上以减小系统体积。该系统实现了透射式太赫兹波扫描成像而无需斩波-锁相技术,并给出在860 GHz的太赫兹波照射下隐藏在信封内部金属的成像结果。

Terahertz imaging has wide applications such as biomedical, security check and so on. With the development of modern information technology, portable terahertz imaging devices are demanding. An imaging system based on CMOS terahertz detector was proposed. The system includes a CMOS terahertz detector, an off-chip ADC, an FPGA, a 2-D step motor, four parabolic mirrors and a terahertz source.The terahertz detector integrates an on-chip patch antenna and a source-feeding NMOS transistor as detection element, which was implemented in 180 nm standard CMOS process. The output signal of the detector was a dc voltage signal which depends on the detected terahertz radiation power proportionally.An external ADC converts the output signal of the detector into digital signal which was captured by an FPGA and then transferred to a computer to realize imaging. In order to reduce the system volume, all above elements were mounted on a set of printed circuit boards（PCBs）. Clear raster-scanning transmission images can be obtained by the imaging system with continuous terahertz illumination. The image of metals in an envelope was obtained by the imaging system at 860 GHz.