Signal Analysis And Desing Of Data Transmission For Frequency Modulated Continuous Terahertz Wave Imaging

In recent years, because of unique characristics, terahertz (THz) wave technologyhas attracted a lot of attention and became research focus. Compared with X-rayimaging, ultrasound imaging and infrared imaging, with some specific uses andadvantages, terahertz imaging technology has become an important aspect in theterahertz wave technology research.Terahertz imaging experimental system for security is studied. After analyzingdifferent types and different applications in terahertz imaging technology, withcharacteristics of imaging targets and indicators demand of imaging system isconsidered, an overall framework is proposed. Electronics frequency modulatedcontinuous wave （FMCW） source is used in this imaging system to three-dimensionalimaging by point-by-point reflective scanning. In order to solve the problems ofirregular intervals, fuzzy distance and parasitic modulation arising in the process of FMranging, the calculation and selection of core parameters has been completed.This work focuses on the signal acquisition process and the design of thetransmission system of the terahertz imaging system. As a key part of the entire system,signal analysis and transmission subsystem affects the final image quality directly. Inorder to improve the sensitivity of the detection system, two separate frequency sourceare used to build a coherent system instead of the traditional single-source coherent.Heterodyne mixing receiving is used in receiving port. The echo signal is downconverted to IF signal by two mixers. Then, this paper introduces the flow of processingof the IF signal, calculation of the beat frequency range, design of anti-aliasing filteringand down-sampling. With data storage format is formulated, the system scan program isdesigned. During the process of designing data transmission scheme of the terahertzimaging system, Fast Ethernet is selected as the transmission mode according to thereal-time data transmission bandwidth requirements of imaging system. The design ofFast Ethernet includes hardware chip selection, schematic design, PCB design and PCBboard soldering. And to improve the efficiency of data transmission, the networkprotocol is simplified according to the characteristics of imaging data, and FPGA logiccode is written by Verilog hardware description language.In this paper, the theoretical analysis and design of the imaging system dataacquisition is completed. And theoretical resolution of plane and depth is far beyond the requirements of system indicators. In this system, the real-time data acquisition about32Mbps, effective transmission rate of87.2Mbps which meets the transmissionrequirements of the imaging system.