Design Of Signal Detection And Acquisition System For FMCW THz Imaging

Terahertz (THz) is a kind of electromagnetic radiation between0.1THz-10THz.Because of high frequency, low photon energy, high perspectivity for most non-polarsubstances and other excellent characteristics, the researches and applications ofterahertz communications, spectral analysis, imaging systems have becomed focus andforward subject recently. Because of the well security and high selectivity, terahertzimaging system has high research and application value in non-destructive testing andsafety testing.In this paper, a terahertz imaging system for security checks has been developed.Base on the requirements and technical specifications for the object, the imaging systemwhich based on single source-single probe-the reflection-’s FMCW THz is proposedafter comparatively analyzing the various THz wave generation and detection, andimaging modalities. And detection and acquisition critical subsystem is focus in thispaper. First, the FM technology principles are introduced in detail, and technicalindicators of the imaging resolution were analyzed. Then, the detection system wasdesigned according to the type and characteristics of the imaging system. The"non-coherent dual-frequency source systems Participation "structure had beenproposed through a comparative analysis of the advantages and disadvantages ofdifferent detection structure. And we also give the requirements of the design of theindicators. The launch, echo and IF signal model was get through the theoreticalderivation of the FM signal transmitter, echo reception and mixer. Meanwhile, we tooksimulation, and validated the feasibility of the design of the imaging system in theory.Finally, the data acquisition system for the IF output signal and the motor positionfeedback pulse signal were designed. This section includes hardware design and logicdesign. In the part of Hardware design, we built the acquisition platform structuresthrough the selection of key components, hardware circuit design and PCB production.Logic design portion achieves the acquisition of the detector output IF signa and theposition information through a modular design. Finally we analyze the results. Theacquisition system can meet the requirement for sampling of5MHz.