Study of diversity techniques for ultra-wideband ground penetrating radar
Marpaung, Delphine Helena Natasha
Date of Issue2017-06-08
School of Electrical and Electronic Engineering
Ground penetrating radar (GPR) is a subsurface imaging method that utilizes an electromagnetic wave in microwave frequency domain. GPR has very wide applications in many different fields, such as civil engineering, archaeology, military, geophysics, and etc. This thesis presents a study of emerging GPR techniques that incorporate spatial diversity waveform diversity, and polarization diversity techniques on GPR systems in addition to ultra-wideband (UWB) technologies. The main contributions of this study are from the following three aspects. Firstly, MIMO configuration has been evaluated for UWB GPR system. The performance of MIMO array is compared with single-input single-output (SISO) and single-input multi-output (SIMO) arrays over various applications and migration methods of GPR. It is shown that MIMO configuration improves the resolution and signal to noise ratio (SNR), reduces the side-lobe level and image artefacts, and has better capability in imaging various target shapes. In addition, an efficient autofocusing method has been proposed for MIMO configuration. This method utilizes migration to zero-offset operator that transform a MIMO data into its equivalent SISO data. The proposed method successfully reduces the computational complexity in focusing MIMO data while preserving the performance improvement provided by MIMO configuration. Secondly, a study of waveform diversity on UWB GPR has been performed. The waveform diversity is implemented by collecting the data with 4 different impulse waveforms. A processing method that combines these datasets has been proposed to distinguish several target materials on some target shapes. Thirdly, the implementation of polarimetric decomposition methods on UWB GPR has been investigated. Several incoherent and coherent polarimetry decompositions from synthetic aperture radar are applied to UWB GPR data. The performance of these methods is evaluated on several target models based on utilities mapping application. The results show that most of the polarimetry decomposition methods provide colour information that can be used to distinguish the shape of the target. The incoherent decompositions outperform the coherent decompositions in providing cleaner images, but at the expense of higher computational complexity. Finally, the polarimetry characteristic of MIMO and SISO configuration are compared. The simulation results show that both configurations provide almost similar polarimetry characteristic. The performance of MIMO configuration and waveform diversity method are investigated based on simulation data. Meanwhile, the polarimetry techniques are verified experimentally in addition to the analysis on simulation data.