Pulse Processing Techniques for Ultra Wide Band Electromagnetic Tomography

Lead Research Organisation: University of Manchester
Department Name: Electrical and Electronic Engineering


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.
Description This research project supported a one year visiting Fellowship by Professor Mohd Zaid Abdullah from the University of Science Malaysia to the Sensing Imaging and Signal Processing (SISP) Group in the School of Electrical and Electronic Engineering at the University of Manchester. This visit was built upon a history of collaboration with Professor Abdullah going back to the award of his MSc (1990) and PhD (1993) from the Industrial Process Tomography Unit at UMIST.
Initially, the aim of this particular project was directed towards developing and perfecting the wavelet transform technique for applications in UWB tomography. However, the visit served as a catalyst for our work on ultra wide band (UWB) electromagnetic tomography (EMT) bringing together the efforts of the PI (Peyton), the CI (Armitage), a Research Fellow partially funded from the SISP Group's EPSRC Tomography Platform Grant, EP/D031117/1 (Yin), and finally a first year PhD student (Bilal) into a team effort. Consequently, the scope of the work went beyond the pulse processing techniques in the original proposal to include the following aspects:
• Wavelet and pulse processing techniques
• UWB Antenna design
• Pulse Propagation in dispersive media in particular water
• Experimental tests on both frequency and time domain equipment
• Modelling using propriety Transmission Line Method (TLM) and commercial FDTD codes
• Image reconstruction
Exploitation Route These techniques could be used to improve image quality as reported in the publications arising from the work.
Sectors Electronics

Description The impact of this award has mainly been as an enabler with the tream by giving a capability in ultra wide band imaging. This subsequently lead to the use of these technique for security scanning of personnel with Rapiscan systems which is now an active theme of research.
First Year Of Impact 2008
Sector Electronics,Security and Diplomacy