Research On The Digital Broadband Electromagnetic Tomography System

Electromagnetic Tomography(EMT), a modality of Progress Tomography(PT)based on the law of Electromagnetic induction, has been developed since1990s. It hasbeen used to obtain spatial distribution information through acquisition of theboundary measurements and suitable image reconstruction algorithms.Compared to other electrical tomography techniques, EMT is capable ofobtaining greater amount of information, and it has advantage of being non-contact,harmlessness, multi-point measurement, real-time imaging and non-radiative. EMThas received wide attention.Despite a late start, EMT has developed rapidly; some domestic universities suchas Tianjin University, have developed their prototype. However, due to the lowoperating frequency, most of the EMT equipments can only work on highconductivity materials, which have greatly limited its application. For this reason, it isof great practical significance to carry out the research of wideband EMT.In view of the problem above, this paper works in the following four areas:Firstly, a kind of front-end circuit board is designed for high frequency signal,which is susceptible to interference and difficult to transmit, by pre-processing theuseful signal at the place close to the signal source, the board can improve the signaltransmission quality and ensure the correct sensor signal acquisition.Secondly, based on the front-end circuit board, a type of high-frequency signalacquisition board is designed, aiming at achieving high-frequency induction signalacquisition controlled by FPGA, and finally complete the signal’s sampling andprocessing, providing raw data for the image reconstruction.Thirdly, by designing the USB communication module, a high-speed datadelivery has been achieved, which ensure the imaging’s validity and real-timing.Finally, on the basis of the works above, some experiments have been done,intending to detect the objects of different conductivity. The data processing followedhas verified the possibility to detect the low conductivity objects with the widebandEMT system.