Thesis (PhD)--University of South Australia, 1995

Thesis (M.S.)--Ohio University, March, 1986. / Title from PDF t.p.

SAR Wave INteraction for Natural Targets Over Land (SWINTOL) is a project funded by the European Space Agency. The study’s goal is to better understand the interaction of high frequency radar (> X-band) with vegetation and soils, in order to drive the development of a high-frequency electromagnetic model to simulate SAR imagery at high resolution (< 1 m). Existing models work well at C and X band frequencies, but do not work properly at higher frequencies. Cranfield University’s role in this project was to provide the field data necessary for model validation and development. Radar imagery was taken of a barley crop over an entire growing season. The portable outdoor GB-SAR system used the tomographic profiling (TP) technique to capture polarimetric imagery of the crop. TP is a scheme that provides detailed maps of the vertical backscatter pattern through a crop canopy, along a narrow transect directly beneath the radar platform. Fully-polarimetric imagery was obtained across overlapping 6.5 GHz bandwidths over the X- and Ku-band frequency range 8-20 GHz. This gave the opportunity to see the detailed scattering behaviour within the crop at the plant component level, from emergence of the crop through to harvesting. In combination with the imagery, full bio-geophysical characterisation of the crop and soil was made on each measurement date. Surface roughness characterisation of the soil was captured using a 3D optical stereoscopic system. This work details the measurements made, and provides a comparative assessment of the results in terms of understanding the backscatter in relation to biophysical and radar parameters.

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sMany theories of structure from motion divide the process into twosparts which are solved using different assumptions. Smoothness of thesvelocity field is often assumed to solve the motion correspondencesproblem, and then rigidity is used to recover the 3D structure. Wesprove results showing that, in a statistical sense, smoothness of thesvelocity field follows from rigidity of the motion.

This thesis contains the complete end-to-end simulation, development, implementation, and calibration of the wide bandwidth, low-Q, Kiwi-SAS synthetic aperture sonar (SAS). Through the use of a very stable towfish, a new novel wide bandwidth transducer design, and autofocus procedures, high-resolution diffraction limited imagery is produced. As a complete system calibration was performed, this diffraction limited imagery is not only geometrically calibrated, it is also calibrated for target cross-section or target strength estimation. Is is important to note that the diffraction limited images are formed without access to any form of inertial measurement information. Previous investigations applying the synthetic aperture technique to sonar have developed processors based on exact, but inefficient, spatial-temporal domain time-delay and sum beamforming algorithms, or they have performed equivalent operations in the frequency domain using fast-correlation techniques (via the fast Fourier transform (FFT)). In this thesis, the algorithms used in the generation of synthetic aperture radar (SAR) images are derived in their wide bandwidth forms and it is shown that these more efficient algorithms can be used to form diffraction limited SAS images. Several new algorithms are developed; accelerated chirp scaling algorithm represents an efficient method for processing synthetic aperture data, while modified phase gradient autofocus and a low-Q autofocus routine based on prominent point processing are used to focus both simulated and real target data that has been corrupted by known and unknown motion or medium propagation errors.

Research work on fabricating organized and reproducible SERS substrates has been done in this thesis. Nano-aperture arrays with circular, bow-tie and cross bow-tie shapes were fabricated by using FIB milling. These arrays were imaged under SEM and their parameters were measured. The optical transmission properties of these arrays were measured by white light transmission. It was found that the shape of the nano-aperture could determine these arrays’ abilities to support SPR. Different shapes would give different SPR modes and generated optical transmission peaks at varied wavelengths. For nano-aperture array with identical shapes, the varied parameters, such as periodicity or tip-to-tip distances, would affect the position of the transmission peaks. Slight increase or decrease of these parameters can be manipulated to adjust the peak positions, catering to the best resonance of the excitation laser used in Raman spectroscopy. The enhancement properties of these arrays as SERS substrates were measured by Raman spectroscopy. Different SERS enhancement properties could be found across different shaped nano-aperture arrays and cross bow-tie nano-aperture arrays give the best SERS enhancement. For nano-aperture array with identical shapes, the varied parameters would affect its ability of SERS enhancement. Near field simulations were carried out in order to explain the relationship of the SERS results and these arrays’ SPR ability. Electrochemical study on these ordered nano-aperture arrays was also carried out in this thesis. / Graduate