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Nondestructive testing and antennameasurements using UWB radar in industrial applications

Time: Tue 2021-03-23 13.00

Location: link for online defense (English)

Subject area: Electrical Engineering

Doctoral student: Vipin Choudhary , Teknisk informationsvetenskap, KTH royal institute of technology

Opponent: Professor Mats Pettersson, Blekinge Tekniska Högskola, 371 79 Karlskrona

Supervisor: Professor Magnus Jansson, Signaler, sensorer och system, ACCESS Linnaeus Centre, Teknisk informationsvetenskap; Professor Daniel Rönnow, University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics; Assoc. Professor Niclas Björsell, University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics

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Many industries are rapidly substituting the manual test operationsand move towards automated operations using modern technologies.Modern technologies such as digital cameras, sonic sensors, infraredsensors, and radar and lidar systems are used for non-destructive testingoperations. Among all the different sensors, radar systems have theability to penetrate built structures (dielectric materials), which makesthem flexible and suitable for a wide range of industrial and militaryapplications in non-destructive sensing. Such examples are the detectionof damages in goods manufacturing, monitoring the health of manystructures, object detection through the wall for security purposes, etc.In particular, ultra-wide-band (UWB) radar systems are beneficial inproviding high measurement accuracy and simultaneously reduced sensitivityto passive interference (such as rain, smoke, mist etc.), immunityto external radiation and noise.The objectives of this thesis are: I) to investigate electrically smallconcealed structures using synthetic aperture radar (SAR), II) to determinethe complex refractive index of objects using an UWB radar system,and III) to answer to the question how we can reduce the mutualcoupling (cross talk) in an UWB radar system with collocated transmitand receive antennae. In objective I, the aim is non-destructive testingof built structures, such as in concrete slab manufacturing or for use inthe renovation process. In addition electrically small periodic meshes,and their orientation, could not be distinguished in conventional SARimages. The proposed polarimetric analysis method demonstrates theusefulness of the singular value decomposition (SVD) using back projectionalgorithm (BPA) in extracting information about shape and forclassifying an electrically small object.Further in this thesis for objective II, a new method for determiningthe complex refractive index (or equivalently the complex relativepermittivity) of objects with planar interfaces is presented. The proposedmethod is relatively insensitive to hardware-impairments such asfrequency-dependence of antennas and analog front end. The objectscan be finite in size and at a finite distance. The limits in size anddistance for the method to be valid are experimentally investigated.Hence, the method is designed for industrial in-line measurements onobjects on conveyor belts. Furthermore, in the following parts of thisthesis −objective III− we investigate and show how a microwave metamaterialbased absorber can be used to improve the performance of aradar system for short range applications, when positioned between thetransmit and receive antennas. As results, the error in estimated targetdistance is reduced and clutter reduction is improved.