UWB CYLINDRICAL MICROWAVE IMAGING SYSTEM EMPLOYING VIRTUAL ARRAY ANTENNA CONCEPT FOR BACKGROUND EFFECT REMOVAL

摘要

In this letter, an Ultra Wideband (UWB) Microwave Imaging System with a novel image reconstruction algorithm aiming at detecting and locating small targets in a homogenous circular cylindrical body is presented. The system uses a double circular scan in which the second scan is achieved after rotating the antenna sub-system or the imaged body by a small angle. The obtained two sets of data serve the purpose of removing a large background signal that masks a small signal due to a target. This is done by forming difference signals for adjacent antenna positions. The procedure is equivalent to using a virtual 2-element 180° out-of-phase fed array antenna. By assuming that the imaged body is symmetric with respect to the axis of the virtual array, the background effect is removed while the signal due to an off-axis target is detected. The difference data is scaled and mapped to produce an image showing the target location. The validity of the proposed image reconstruction algorithm is demonstrated in an example of a cylindrical plastic container filled with a vegetable oil and small diameter cylindrical water targets.