Pulse Processing Techniques for Ultra Wide Band Electromagnetic Tomography

对改进产品和工艺的需求推动了将断层扫描技术用于工业和环境应用的研究。因此，人们研究和开发了一系列传感模式，包括电学、电磁（EM）、声学、光学和核子现象，每种模式都为它们的目标应用领域提供了特定的优势。电学和电磁层析成像（EMT）系统具有快速、低成本、非侵入性和相对安全的特点。然而，与其他模态（如X射线、MR、US等）相比，它们的图像质量相对较差。这是因为电气系统具有有限数量（例如23至25个）的固定、单频激励/检测元件。因此，可以重建图像帧的独立测量的数量是有限的（通常为102至103），因此在不使用先验知识的情况下难以进行高分辨率图像重建。另一个基本限制是物体材料影响询问电磁场的方向。这通常被称为软场效应，并对图像重建提出了重大挑战。因此，电气和EMT系统的应用范围仅限于那些只能接受中等分辨率的系统。UWB电磁层析成像（EMT）是基于电磁脉冲在目标中的传播，具有高分辨率成像的潜力，特别是如果能够实现<10 ps的时间抖动（相当于脉冲在水中传播的亚毫米距离），并且能够充分模拟脉冲色散机制，则更是如此。与标准的电层析成像技术相比，高分辨率是可能的，因为精确的定时信息可以沿着更大的带宽。该项目考虑脉冲处理技术，这可能有助于通过提供更准确的估计脉冲分量的到达时间来提高图像质量。

The demand for improved products and processes has driven research in using tomography techniques for industrial and environmental applications. As a result, a range of sensing modalities have been researched and developed, embracing electrical, electromagnetic (EM), acoustic, optical and nucleonic phenomena, with each modality offering particular advantages for their target application areas.Electrical and electromagnetic tomography (EMT) systems are fast, low cost, non-intrusive and relatively safe. However, their image quality is relatively poor compared to other modalities such as X-ray, MR, US, etc. This is because electrical systems have a limited number (say 23 to 25) of fixed, single frequency, excitation / detection elements. Consequently, the number of independent measurements upon which an image frame can be reconstructed is limited (typically 102 to 103), and therefore high-resolution image reconstruction is difficult without the use of a priori knowledge. Another fundamental is limit is that the object material affects the direction of the interrogating EM fields. This is often known as the soft field effect and presents a major challenge for image reconstruction. Consequently the range of applications for electrical and EMT systems has been limited to those where only modest resolution is acceptable. Clearly a high resolution EM technique would represent a major breakthrough for the discipline.UWB electromagnetic tomography (EMT) is based on the propagation of EM pulses through the target and offer the potential for high-resolution imaging, especially if timing jitters of <10ps can be achieved (equivalent to a sub mm distance for a pulse travelling in water) and pulse dispersion mechanisms can be adequately modelled. High resolutions are possible, compared to standard electrical tomography techniques, because precision timing information is available along with much greater bandwidth. This project considers pulse processing techniques which may help to improve image quality by providing more accurate estimations of the arrival times of the pulse components.