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Dissertations / Theses on the topic 'Aperture Synthesis Imaging'

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Published: 4 June 2021

Last updated: 20 February 2023

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1

Conway, John E. "Multi-frequency synthesis with MERLIN : a new technique in aperture synthesis imaging." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328286.

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2

Burki, Jehanzeb. "Fast circular aperture synthesis in sar all-aspect target imaging." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26514.

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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Christopher F. Barnes; Committee Member: Andrew F. Peterson; Committee Member: Douglas B. Williams; Committee Member: Haomin Zhou; Committee Member: Justin K. Romberg. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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3

Krug, Sarah Elaine. "Digital Phase Correction of a Partially Coherent Sparse Aperture System." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1437476352.

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4

Crotty, Maureen. "Signal to Noise Ratio Effects on Aperture Synthesis for Digital Holographic Ladar." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1355245759.

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5

Hennen, John Andrew. "Registration Algorithms for Flash Inverse Synthetic Aperture LiDAR." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1576142937639181.

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6

Amy, Shaun Wallace. "A Radio Study of Selected Regions in the Magellanic Clouds." Thesis, The University of Sydney, 2000. http://hdl.handle.net/2123/358.

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The Magellanic Clouds have long provided a rich celestial laboratory for many astrophysical research programmes. Their location relatively close to the Earth and away from the plane of our Galaxy has made them a natural target for Southern Hemisphere ground-based instrumentation. Likewise, the continuing quest for images of the Clouds with higher dynamic range and improved angular resolution has driven a continual improvement in instrumentation across a range of wavelength bands. The cornerstone of this thesis is a study of selected sources in the Magellanic Clouds. The sample was chosen from the 843MHz Molonglo Observatory Synthesis Telescope survey of the Clouds, based on the existing knowledge of each source, its flux density and angular extent. This sample was used to explore observational and analysis techniques with the Australia Telescope Compact Array in order to better determine the nature of these objects and to identify those sources worthy of further study. This work highlights many pertinent issues associated with the correct classification of sources when only a limited amount of data is available. These issues led directly to the development of a more systematic approach in the classification of the Large Magellanic Cloud source sample, detailed for the first time in this thesis. Two supernova remnants in the Small Magellanic Cloud were studied in detail. The Australia Telescope images of 1E0102.2-7219 revealed, for the first time, the radio structure of this young oxygen-rich supernova remnant, and allowed a detailed comparison with existing optical and X-ray data to be undertaken. The comparisons presented in this thesis and in an earlier publication have prompted exciting new X-ray observations at unprecedented angular resolution. The second, 0101-7226, studied as part of an international collaboration, has a shell morphology at radio wavelengths but no associated X-ray emission and is therefore something of an enigma.

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7

Amy, Shaun Wallace. "A Radio Study of Selected Regions in the Magellanic Clouds." University of Sydney. Physics, 2000. http://hdl.handle.net/2123/358.

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The Magellanic Clouds have long provided a rich celestial laboratory for many astrophysical research programmes. Their location relatively close to the Earth and away from the plane of our Galaxy has made them a natural target for Southern Hemisphere ground-based instrumentation. Likewise, the continuing quest for images of the Clouds with higher dynamic range and improved angular resolution has driven a continual improvement in instrumentation across a range of wavelength bands. The cornerstone of this thesis is a study of selected sources in the Magellanic Clouds. The sample was chosen from the 843MHz Molonglo Observatory Synthesis Telescope survey of the Clouds, based on the existing knowledge of each source, its flux density and angular extent. This sample was used to explore observational and analysis techniques with the Australia Telescope Compact Array in order to better determine the nature of these objects and to identify those sources worthy of further study. This work highlights many pertinent issues associated with the correct classification of sources when only a limited amount of data is available. These issues led directly to the development of a more systematic approach in the classification of the Large Magellanic Cloud source sample, detailed for the first time in this thesis. Two supernova remnants in the Small Magellanic Cloud were studied in detail. The Australia Telescope images of 1E0102.2-7219 revealed, for the first time, the radio structure of this young oxygen-rich supernova remnant, and allowed a detailed comparison with existing optical and X-ray data to be undertaken. The comparisons presented in this thesis and in an earlier publication have prompted exciting new X-ray observations at unprecedented angular resolution. The second, 0101-7226, studied as part of an international collaboration, has a shell morphology at radio wavelengths but no associated X-ray emission and is therefore something of an enigma.

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8

Nova, Lavado Enrique. "Millimeter-wave and terahertz imaging techniques." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/129466.

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This thesis presents the development and assessment of imaging techniques in the millimeterwave (mmW) and terahertz frequency bands. In the first part of the thesis, the development of a 94 GHz passive screener based on a total-power radiometer (TPR) with mechanical beamscanning is presented. Several images have been acquired with the TPR screener demonstrator, either in indoor and outdoor environments, serving as a testbed to acquire the know-how required to perform the research presented in the following parts of the thesis. In the second part of the thesis, a theoretical research on the performance of near-field passive screeners is described. This part stands out the tradeoff between spatial and radiometric resolutions taking into account the image distortion produced by placing the scenario in the near-field range of the radiometer array. In addition, the impact of the decorrelation effect in the image has been also studied simulating the reconstruction technique of a synthetic aperture radiometer. Guidelines to choose the proper radiometer depending on the application, the scenario, the acquisition speed and the tolerated image distortion are given in this part. In the third part of the thesis, the development of a correlation technique with optical processing applicable to millimeter-wave interferometric radiometers is described. The technique is capable of correlating wide-bandwidth signals in the optical domain with no loss of radiometric sensitivity. The theoretical development of the method as well as measurements validating the suitability to correlate radiometric signals are presented in this part. In the final part of the thesis, the frequency band of the imaging problem is increased to frequencies beyond 100 GHz, covering the THz band. In this case the research is centered in tomographic techniques that include spectral information of the samples in the reconstructed images. The tomographic algorithm can provide detection and identification of chemical compounds that present a certain spectral footprint in the THz frequency band.

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9

Walden, Aleksi. "SMOS satellite hardware anomaly prediction methods based on Earth radiation environment data sets." Thesis, Luleå tekniska universitet, Rymdteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-59789.

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SMOS (Soil Moisture and Ocean Salinity) is ESA's Earth Explorer series satellite carrying the novel MIRAS (Microwave Imaging Radiometer with Aperture Synthesis) interferometric synthetic aperture radar. Its objective is monitoring and studying the planet's water cycle by following the changes in soil moisture levels and ocean surface salt concentrations on a global scale. The success of the mission calls for nearly uninterrupted operation of the science payload. However, the instrument experiences sporadically problems with its hardware, which cause losses of scientific data and may require intervention from ground to resolve. The geographical areas in which most of these anomalies occur, polar regions and the South-Atlantic anomaly, give cause to assume these problems are caused by charged particles in the planet's ionosphere. In this thesis, methods of predicting occurrence of hardware anomalies from indicators of Earth radiation environment are investigated.

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10

Dutkiewicz, Marek Karol. "Synthetic aperture sonar for sub bottom imaging." Master's thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/21962.

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The major problems associated with implementing synthetic apertures in sonar may be overcome by applying the technique to sub-bottom imaging. The use of a low frequency aids both penetration of the sediment and the attainment of long coherent apertures. The implementation of synthetic apertures realises a narrow fan beam. By directing this beam out sideways, a more rapid survey rate is possible than that achieved by the normal echo-sounding mode used in sub-bottom profiling. The synthetic aperture technique appears to offer significant advantages over that of parametric arrays, for high resolution sub-bottom imaging. Synthetic apertures have been implemented in a laboratory tank, under controlled conditions at a fresh water reservoir, and under realistic operational conditions at sea. Encouraging results have been obtained.

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11

Kelly, Shaun Innes. "Iterative synthetic aperture radar imaging algorithms." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9368.

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Synthetic aperture radar is an important tool in a wide range of civilian and military imaging applications. This is primarily due to its ability to image in all weather conditions, during both the day and the night, unlike optical imaging systems. A synthetic aperture radar system contains a step which is not present in an optical imaging system, this is image formation. This is required because the acquired data from the radar sensor does not directly correspond to the image. Instead, to form an image, the system must solve an inverse problem. In conventional scenarios, this inverse problem is relatively straight forward and a matched lter based algorithm produces an image of suitable image quality. However, there are a number of interesting scenarios where this is not the case. Scenarios where standard image formation algorithms are unsuitable include systems with data undersampling, errors in the system observation model and data that is corrupted by radio frequency interference. Image formation in these scenarios will form the topics of this thesis and a number of iterative algorithms are proposed to achieve image formation. The motivation for these proposed algorithms is primarily from the eld of compressed sensing, which considers the recovery of signals with a low-dimensional structure. The rst contribution of this thesis is the development of fast algorithms for the system observation model and its adjoint. These algorithms are required by large-scale gradient based iterative algorithms for image formation. The proposed algorithms are based on existing fast back-projection algorithms, however, a new decimation strategy is proposed which is more suitable for some applications. The second contribution is the development of a framework for iterative near- eld image formation, which uses the proposed fast algorithms. It is shown that the framework can be used, in some scenarios, to improve the visual quality of images formed from fully sampled data and undersampled data, when compared to images formed using matched lter based algorithms. The third contribution concerns errors in the system observation model. Algorithms that correct these errors are commonly referred to as autofocus algorithms. It is shown that conventional autofocus algorithms, which work as a post-processor on the formed image, are unsuitable for undersampled data. Instead an autofocus algorithm is proposed which corrects errors within the iterative image formation procedure. The proposed algorithm is provably stable and convergent with a faster convergence rate than previous approaches. The nal contribution is an algorithm for ultra-wideband synthetic aperture radar image formation. Due to the large spectrum over which the ultra-wideband signal is transmitted, there is likely to be many other users operating within the same spectrum. These users can produce signi cant radio frequency interference which will corrupt the received data. The proposed algorithm uses knowledge of the RFI spectrum to minimise the e ect of the RFI on the formed image.

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12

Zalamans, Louise. "3D Synthetic Aperture Imaging Using LaserUltrasonics." Thesis, Luleå tekniska universitet, Signaler och system, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-85381.

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Synthetic Aperture Focusing Technique (SAFT) is a powerful method to createfocused images of the inside of opaque samples by using delay-and-sum of acquireddata. It gives a high resolution and when using a generation laser and a detectionlaser it is also non-contact. This thesis was made at Swerim, and the aim wasto create an 3D-SAFT algorithm and to visualise the reconstructed image. Twosamples were used, both were 3D-printed with known defects that varied in sizefrom 0.05 mm to 1 mm. The defects were lined up in rows, with 10 in each row.After the algorithm was used on the acquired data from the two samples, six toeight defects were found in each row. Both samples had three rows of defects. Themeasured sizes of the defects were not exactly as the actual size but ranged a fewmillimetre too small or big compared to the real size. Overall the algorithm workswell. The resolution of the 3D images are the same as for the 2D-SAFT algorithmalready made by Swerim. As of now the 3D images may not be worth the time ittakes to process, but if a better way to visualise the data is made in the future, itwill be good to be able to see the defects in 3D.

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13

Liu, Jun. "Ionospheric effects on synthetic aperture radar imaging /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/5890.

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14

Barkefors, Annea. "3D Synthetic Aperture Technique for Ultrasonic Imaging." Thesis, Uppsala University, Signals and Systems Group, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-121022.

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The group for non-destructive testing at Uppsala University has recently implemented the phase shift migration method, which is a method to focus images acquired unfocused using ultrasound. However, their work has been limited to 2D data, while for many applications the gathered data is 3D. This project has extended the old implementation to 3D data. The new implementation has been done in two different ways, giving one algorithm that works fast but needs much RAM, and one algorithm that takes long time but works on smaller computers, not demanding as much memory. The fast algorithm works faster than the time it takes to acquire the raw data, which makes real-time use realistic. To test the performance of the two algorithms with respect to image improvement, both against each other and against the previous 2D implementation, a number of experiments were carried out, which showed that, apart from processing time, the two new algorithms were equal in performance. The experiments also showed that the obtained resolution in both x- and y-directions matched the theoretical discussion.

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15

Schlutz, Matthew. "Synthetic Aperture Radar Imaging Simulated in MATLAB." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/92.

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This thesis further develops a method from ongoing thesis projects with the goal of generating images using synthetic aperture radar (SAR) simulations coded in MATLAB. The project is supervised by Dr. John Saghri and sponsored by Raytheon Space and Airborne Systems. SAR is a type of imaging radar in which the relative movement of the antenna with respect to the target is utilized. Through the simultaneous processing of the radar reflections over the movement of the antenna via the range Doppler algorithm (RDA), the superior resolution of a theoretical wider antenna, termed synthetic aperture, is obtained. The long term goal of this ongoing project is to develop a simulation in which realistic SAR images can be generated and used for SAR Automatic Target Recognition (ATR). Current and past Master’s theses on ATR were restricted to a small data set of Man-portable Surveillance and Target Acquisition Radar (MSTAR) images as most SAR images for military ATR are not released for public use. Also, with an in-house SAR image generation scheme the parameters of noise, target orientation, the elevation angle or look angle to the antenna from the target and other parameters can be directly controlled and modified to best serve ATR purposes or other applications such as three-dimensional SAR holography. At the start of the project in September 2007, the SAR simulation from previous Master’s theses was capable of simulating and imaging point targets in a two dimensional plane with limited mobility. The focus on improvements to this simulation through the course of this project was to improve the SAR simulation for applications to more complex two-dimensional targets and simple three-dimensional targets, such as a cube. The input to the simulation uses a selected two-dimensional, grayscale target image and generates from the input a two-dimensional target profile of reflectivity over the azimuth and range based on the intensity of the pixels in the target image. For three-dimensional simulations, multiple two-dimensional azimuth/range profiles are imported at different altitudes. The output from both the two-dimensional and three-dimensional simulations is the SAR simulated and RDA processed image of the input target profile. Future work on this ongoing project will include an algorithm to calculate line of sight limitations of point targets and processing optimization of the radar information generation implemented in the code so that more complex and realistic targets can be simulated and imaged using SAR for applications in ATR and 3D SAR holography.

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16

Vaish, Vaibhav. "Synthetic aperture imaging using dense camera arrays /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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17

Romero, Cindy G. "High Resolution Simulation of Synthetic Aperture Radar Imaging." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/345.

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The goal of this Master’s thesis is to develop a more realistic simulation of Synthetic Aperture Radar (SAR) that has the ability to image detailed targets, and that can be used for Automatic Target Recognition (ATR). This thesis project is part of ongoing SAR ATR research at California Polytechnic State University (Cal Poly) sponsored by Raytheon Space & Airborne Systems and supervised by Dr. John Saghri. SAR is a form of radar that takes advantage of the forward motion of an antenna mounted on a moving platform (such as an airplane or spacecraft) to synthetically produce the effect of a longer antenna. Since most SAR images used for military ATR are classified and not available to the general public, all academic research to date on ATR has been limited to a small data set of Moving and Stationary Target Acquisition and Recognition Radar (MSTAR) images. Due to the unavailability of radar equipment or a greater range of SAR data, it has been necessary to create a SAR image generation scheme in which the parameters of the radar platform can be directly modified and controlled to be used for ATR applications. This thesis project focuses on making several improvements to Matthew Schlutz’s ‘Synthetic Aperture Radar Imaging Simulated in Matlab’ thesis. First, the simulation is optimized by porting the antenna pattern and echo generator from Matlab to C++, and the efficiency of the code is improved to reduced processing time. A three-dimensional (3-D) graphics application called Blender is used to create and position the target models in the scene imaged by the radar platform and to give altitude, target range (range of closest approach from the platform to the center area of the target) and elevation angle information to the radar platform. Blender allows the user to take pictures of the target as seen from the radar platform, and outputs range information from the radar platform plane to each point in the image. One of the major advantages of using Blender is that it also outputs range and reflectivity information about each pixel in the image. This is a significant characteristic that was hardcoded in the previous theses, making those simulations less realistic. For this thesis project, once the target scene is created in Blender, an image is rendered and saved as an OpenEXR file. The image is rendered in orthographic mode, which is a form of projection whereby the target plane is parallel with the projection plane. This parameter means that the simulation cannot image point targets that appear and disappear during the platform motion. The echo generation program then uses the range and reflectivity obtained from the OpenEXR file, the optimized antenna pattern, and several other user defined parameters to create the echo (received signal). Once the echo is created in the echo generation program, it is then read into Matlab in order for it to go through the Range Doppler Algorithm (RDA) and then output the final SAR image.

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18

Chan, Tsz K. "Experimental studies on microwave detection and imaging of targets in clutter using correlation techniques /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/6011.

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19

Davis, Michael Scott. "MIMO radar: signal processing, waveform design, and applications to synthetic aperture imaging." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53566.

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This dissertation analyzes the capability of multiple-input, multiple-output (MIMO) radar techniques to improve the image quality and area-coverage rate of synthetic aperture imaging systems. A signal processing architecture for MIMO radar is used to understand the applicability of MIMO for synthetic aperture radar (SAR) and synthetic aperture sonar (SAS) systems. MIMO SAR/SAS is shown to be a natural extension of standard multichannel synthetic aperture imaging techniques to exploit transmit degrees of freedom in addition to those used on receive. Degradation in range sidelobe performance and the associated impact on image quality is identified as a key impediment to MIMO SAR/SAS. A novel mismatched filtering approach is presented to mitigate this issue. New results in sampling theory are derived that allow the aliasing that occurs when a wide-sense stationary random process is non-uniformly sampled to be quantified. These results are applied to the case of recurrent sampling and used to quantify the impact of azimuth ambiguities on MIMO SAR/SAS image contrast.

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20

Hawkins, David William. "Synthetic aperture imaging algorithms : with application to wide bandwidth sonar." Thesis, University of Canterbury. Electrical and Computer Engineering, 1996. http://hdl.handle.net/10092/1082.

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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.

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21

Marom, Moshe. "Interferometric SAR imaging of ocean surface currents and wavefields." Thesis, Monterey, Calif. : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA239312.

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Dissertation (Ph.D. in Physical Oceanography)--Naval Postgraduate School, June 1990.
Dissertation supervisor: Thornton, E.B. "June 1990." Description based on title screen as viewed on 19 October 2009. DTIC Identifiers: INSAR (INTERFEROMETRIC SAR). Author(s) subject terms: Interferometric SAR, scene coherence time, 2D wavenumber spectra, surface currents. Includes bibliographical references (p. 192-198). Also available in print.

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22

Bajpayee, Abhishek. "3D particle tracking velocimetry using synthetic aperture imaging." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/97940.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 63-65).
3D visualization of fluid flow is of critical significance to a number of applications ranging from micro-scale medical devices to design of ships and airplanes. Of the various techniques currently used to visualize flow fields, particle image velocimetry (PIV) offers great advantages because of the high resolution quantitative results it provides. The feasibility of using synthetic aperture (SA) imaging to conduct 3D Particle Image Velocimetry (PIV) has been previously demonstrated. This thesis presents the development of a technique that extends SA imaging to 3D Particle Tracking Velocimetry (PTV), adding the ability to conduct Lagrangian studies on flow fields over time. A new method has been developed to accurately locate seeding particles in volumes reconstructed using SA imaging, based on a proposed thresholding and average intensity based scheme, which is able to locate particles in densely seeded flows. In addition, a new and much faster method for reconstructing volumes, based on a homography fit (HF) refocusing method, is proposed which facilitates rapid processing of large amounts of data recorded using high speed cameras for example. The capability of using SA imaging to conduct PTV is demonstrated by tracking located particles using the relaxation based algorithm. The developed technique provides accurate and high resolution PTV results at a much higher computation speed compared to other state of the art techniques. If engineered further,the presented technique has the potential to become the method of choice to conduct velocimetry.
by Abhishek Bajpayee.
S.M.

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23

Halcrow, Gavin. "Bistatic synthetic aperture radar imaging using Fournier methods." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/14960.

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24

Zhang, Renyuan, and Siyang Cao. "3D Imaging Millimeter Wave Circular Synthetic Aperture Radar." MDPI AG, 2017. http://hdl.handle.net/10150/624963.

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In this paper, a new millimeter wave 3D imaging radar is proposed. The user just needs to move the radar along a circular track, and high resolution 3D imaging can be generated. The proposed radar uses the movement of itself to synthesize a large aperture in both the azimuth and elevation directions. It can utilize inverse Radon transform to resolve 3D imaging. To improve the sensing result, the compressed sensing approach is further investigated. The simulation and experimental result further illustrated the design. Because a single transceiver circuit is needed, a light, affordable and high resolution 3D mmWave imaging radar is illustrated in the paper.

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25

Henry, Samuel C. "3-D Terahertz Synthetic-Aperture Imaging and Spectroscopy." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/693.

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Terahertz (THz) wavelengths have attracted recent interest in multiple disciplines within engineering and science. Situated between the infrared and the microwave region of the electromagnetic spectrum, THz energy can propagate through non-polar materials such as clothing or packaging layers. Moreover, many chemical compounds, including explosives and many drugs, reveal strong absorption signatures in the THz range. For these reasons, THz wavelengths have great potential for non-destructive evaluation and explosive detection. Three-dimensional (3-D) reflection imaging with considerable depth resolution is also possible using pulsed THz systems. While THz imaging (especially 3-D) systems typically operate in transmission mode, reflection offers the most practical configuration for standoff detection, especially for objects with high water content (like human tissue) which are opaque at THz frequencies. In this research, reflection-based THz synthetic-aperture (SA) imaging is investigated as a potential imaging solution. THz SA imaging results presented in this dissertation are unique in that a 2-D planar synthetic array was used to generate a 3-D image without relying on a narrow time-window for depth isolation [1]. Novel THz chemical detection techniques are developed and combined with broadband THz SA capabilities to provide concurrent 3-D spectral imaging. All algorithms are tested with various objects and pressed pellets using a pulsed THz time-domain system in the Northwest Electromagnetics and Acoustics Research Laboratory (NEAR-Lab).

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26

Sugavanam, Nithin. "Compressive sampling in radar imaging." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503277528254942.

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27

Pace, Phillip E. "A robust autofocusing technique for applications in synthetic aperture stripmap imaging radars - Design and simulation." Ohio : Ohio University, 1986. http://www.ohiolink.edu/etd/view.cgi?ohiou1183144736.

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28

Cook, Daniel A. "Synthetic Aperture Sonar Motion Estimation and Compensation." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14538.

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Synthetic aperture sonar (SAS) is the underwater acoustic counterpart to stripmap-mode synthetic aperture radar (SAR). Current seagoing SAS systems are deployed on unmanned robotic vechicles, commonly referred to as autonomous underwater vehicles (AUVs). As with SAR, SAS imaging is ideally done with a straight-line collection trajectory. However, SAS is far more susceptible to image degradation caused by the actual sensor trajectory deviating from a pefectly straight line. Unwanted motion is virtually unavoidable in the sea due to the influence of currents and wave action. In order to construct a perfectly-focused SAS image the motion must either be constrained to within one-eighth of a wavelength over the synthetic aperture, or it must be measured with the same degree of accuracy and then accounted for in the processing software. Since the former is not possible, the latter approach must be taken. The technique known as redundant phase centers (RPC) has proven to be insrumental in solving the problem of SAS motion compensation. In essence, RPC simply refers to the practice of overlapping a portion of the receiver array from one ping (transmission and reception) to the next. The signals observed by this overlapping portion will be identical except for a time shift proportional to the relative motion between pings. The time shifts observed by the RPC channels of the receiver array are scalars representing the projection of the array receiver locations onto the image slant plane, and these time shifts can be used to compensate for the unwanted platform motion. This thesis presents several extensions to the standard RPC technique in which the RPC time delays are combined with the AUV's on-board navigation data. The scalar time delays are decomposed into the components induced by the six degrees of freedom of the motion: i.e., the linear and angular velocities. Thus, the time delays observed in the image slant plane can be used to refine the motion estimate in an absolute frame of reference external to the AUV. Creating a high-resolution SAS image of the sea floor in an automatic fashion demands accurate and robust motion estimation. The performance of the motion estimation schemes presented is demonstrated using actual field data collected from an assortment of current research SAS systems.

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29

Schumm, Bryce Eric. "Effect of Atmospheric Turbulence on Synthetic Aperture Ladar Imaging Performance." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1509259463652724.

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30

Lee, Hua. "MOTION COMPENSATION FOR HIGH-RESOLUTION SYNTHETIC-APERTURE SONAR IMAGING." International Foundation for Telemetering, 2002. http://hdl.handle.net/10150/605603.

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International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California
This paper presents a motion estimation and correction technique for the realization of synthetic-aperture sonar imaging. It utilizes the redundancy provided by the multiple-element receiver array and physical-array sub-images are used for the estimate the motion errors between adjacent receiver positions in the form of phase errors. Subsequently, motion errors can be corrected accordingly by making adjustments to the wavefield data samples prior to the formation of synthetic-aperture images.

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Ozdemir, Caner. "Synthetic aperture radar algorithms for imaging antenna-platform scattering /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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Freethy, Simon. "Synthetic aperture imaging of B-X-O mode conversion." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/2352/.

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The conversion of thermally-born electrostatic waves in tokamak plasmas has the potential to be a powerful diagnostic for tokamak edge physics. Analytic theory and full wave modelling both conclude that analysis of emission in the microwave region carries with it information on the magnetic field in spatially localised areas which depend on density and frequency. Knowing these quantities and the 3D (2D + frequency) microwave emission pattern, it is in theory possible to calculate the current density which is vital to the understanding of the plasma pedestal. Motivated by a pilot experiment carried out on the Mega Ampere Spherical Tokamak (MAST), a novel microwave imaging device has been developed to obtain the first images of mode conversion in a Tokamak and to prove the principle of the synthetic aperture imaging technique on Tokamak devices. Here the design and calibration of the Synthetic Aperture Microwave Imaging (SAMI) radiometer is described, as well as the presentation and comparison of some of the first images of mode conversion with full wave simulations.

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Ravichandran, Kulasegaram. "Radar imaging using two-dimensional synthetic aperture radar (SAR) techniques /." abstract and full text PDF (UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1446797.

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Thesis (M.S.)--University of Nevada, Reno, 2007.
Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

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Oh, Seung-Mok. "Iterative space-time domain fast multiresolution SAR imaging algorithms." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/13544.

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35

Barratt, Nicholas Roy. "The simulation of SAR imagery using discretised scattering models." Thesis, King's College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283117.

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36

Guan, Lim Kian. "Battle damage assessment using Inverse Synthetic Aperture Radar (ISAR) /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FGuan.pdf.

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Thesis (M.S. in Combat Systems Technology)--Naval Postgraduate School, Dec. 2004.
Thesis Advisor(s): Brett H. Borden, Donald L. Walters. Includes bibliographical references (p. 97-98). Also available online.

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Gerbl, Florian. "Evaluation of wide beam, short-range synthetic aperture radar imaging." Berlin Logos-Verl, 2007. http://deposit.d-nb.de/cgi-bin/dokserv?id=3071690&prov=M&dok_var=1&dok_ext=htm.

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38

Belden, Jesse (Jesse Levi). "Synthetic aperture imaging for three dimensional resolution of fluid flows." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67577.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Fluid mechanics and instrumentation have a long history together, as experimental fluids studies play an important role in describing a more complete physical picture in a variety of problems. Presently. state-of-the-art instruments for fluid flows aim to resolve various quantities in three-dimensions. This thesis describes a novel three dimensional imaging system intended to extend laboratory measurement capabilities in complicated flows where knowledge is incomplete. In particular, the imaging system is designed to perform three-dimensional velocimetry in densely seeded flows where object geometry may partially occlude the field as well as to measure and locate bubbles, droplets and particles in three-dimensions in multiphase flows. An instrument of this kind has ramifications in a variety of engineering applications from air-sea interaction to Naval hydrodynamics to turbulence and beyond. The imaging system is based upon synthetic aperture (SA) imaging, which has received much attention in the computer vision community recently. In focus images from an array of synchronized cameras are recombined in software post-capture using a refocusing algorithm to generate a focal stack of synthetic images. Each synthetic image has a narrow depth of field, and objects residing at this depth appear sharp while off-plane objects appear blurred. The refocusing algorithm not only allows for 3D reconstruction of a scene, but also enables "see-through" effects, whereby an object occluded in some of the camera views will be seen in the synthetic images. In this thesis, considerations for development of a three-dimensional measurement system for fluid flows based on the SA imaging field are made. A high-performance three-dimensional particle image velocimetry technique is described and validated. Also, a method for auto-calibration of mutli-camera setups for fluids experiments is derived and developed. Finally, algorithms are generated for application to multiphase flows and the technique is applied to a circular plunging jet with results showing excellent agreement to prior literature and yielding new insight into the problem.
by Jesse Belden.
Ph.D.

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Hazard, Christopher R. "Real-time three-dimensional ultrasound imaging using synthetic aperture beamforming." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486399160107451.

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40

Soraghan, John J. "Synthetic Aperture Radar signal processing on the Distributed Array Processor." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254743.

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41

Preiss, Mark. "Detecting scene changes using synthetic aperture radar interferometry /." Title page, table of contents and abstract only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09php9242.pdf.

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Matthew, Pianto Donald. "Modeling synthetic aperture radar image data." Universidade Federal de Pernambuco, 2008. https://repositorio.ufpe.br/handle/123456789/7128.

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Made available in DSpace on 2014-06-12T18:29:09Z (GMT). No. of bitstreams: 2 arquivo4274_1.pdf: 5027595 bytes, checksum: 37a31f281a0f888465edbdc60cb2db39 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2008
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Nessa tese estudamos a estimação por máxima verossimilhança (MV) do parâmetro de aspereza da distribuição G 0 A de imagens com speckle (Frery et al., 1997). Descobrimos que, satisfeita uma certa condição dos momentos amostrais, a função de verossimilhança é monótona e as estimativas MV são infinitas, implicando uma região plana. Implementamos quatro estimadores de correção de viés em uma tentativa de obter estimativas MV finitas. Três dos estimadores são obtidos da literatura sobre verossimilhança monótona (Firth, 1993; Jeffreys, 1946) e um, baseado em reamostragem, é proposto pelo autor. Fazemos experimentos numéricos de Monte Carlo para comparar os quatro estimadores e encontramos que não existe um favorito claro, a menos quando um parâmetro (dado a priori da estimação) toma um valor específico. Também aplicamos os estimadores a dados reais de radar de abertura sintética. O resultado desta análise mostra que os estimadores precisam ser comparados com base em suas habilidades de classificar regiões corretamente como ásperas, planas, ou intermediárias e não pelos seus vieses e erros quadráticos médios

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Zhu, Sha. "A Bayesian Approach for Inverse Problems in Synthetic Aperture Radar Imaging." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00844748.

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Synthetic Aperture Radar (SAR) imaging is a well-known technique in the domain of remote sensing, aerospace surveillance, geography and mapping. To obtain images of high resolution under noise, taking into account of the characteristics of targets in the observed scene, the different uncertainties of measure and the modeling errors becomes very important.Conventional imaging methods are based on i) over-simplified scene models, ii) a simplified linear forward modeling (mathematical relations between the transmitted signals, the received signals and the targets) and iii) using a very simplified Inverse Fast Fourier Transform (IFFT) to do the inversion, resulting in low resolution and noisy images with unsuppressed speckles and high side lobe artifacts.In this thesis, we propose to use a Bayesian approach to SAR imaging, which overcomes many drawbacks of classical methods and brings high resolution, more stable images and more accurate parameter estimation for target recognition.The proposed unifying approach is used for inverse problems in Mono-, Bi- and Multi-static SAR imaging, as well as for micromotion target imaging. Appropriate priors for modeling different target scenes in terms of target features enhancement during imaging are proposed. Fast and effective estimation methods with simple and hierarchical priors are developed. The problem of hyperparameter estimation is also handled in this Bayesian approach framework. Results on synthetic, experimental and real data demonstrate the effectiveness of the proposed approach.

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Panzner, Berthold [Verfasser]. "Synthetic Aperture Radar Focusing Techniques for Subsurface Radar Imaging / Berthold Panzner." München : Verlag Dr. Hut, 2013. http://d-nb.info/1031844910/34.

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45

Logan, Cedric Leonard. "An estimation-theoretic technique for motion-compensated synthetic-aperture array imaging." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9122.

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Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.
Vita.
Includes bibliographical references (p. 351-354).
Synthetic-Aperture Radar (SAR) is an imaging technique that achieves high azimuth resolution by using coherent processing to exploit the relative motion between an airborne or spaceborne radar antenna and the imaged target field (effectively synthesizing the effect of a larger aperture array). From an estimation-theoretic perspective, this thesis addresses the following limitations of conventional imaging techniques for the spotlight-mode version of SAR: sidelobe imaging artifacts and loss of resolution for stationary SAR scenes containing high-amplitude scatterers, and blurring and object-displacement artifacts in the presence of moving targets. First, this thesis presents a generalized estimation-theoretic SAR imaging framework which exploits the idea of L1-norm regularization. Some results are included which demonstrate the utility of this approach for reducing sidelobes and improving resolution for stationary SAR images. A parameterized L-norm-based moving-target imaging technique is also presented. For the case of a single moving target, this technique is able to compensate for the blurring due to temporally-constant velocity rigid-body motion (even if the target scatterers are closely-spaced). However, the motion-induced object-displacement compensation performance of this technique is significantly affected by velocity estimation errors. This thesis also presents an estimation-theoretic moving-target SAR imaging framework which uses a multi-dimensional matched-filter for computing a set of scatterer-velocity estimates which are used as initial conditions for an L1-norm-based estimation algorithm which assumes that the target scatterers have temporally-constant spatially-independent velocities. Therefore, this framework is able to image a moving target and nearby high-amplitude stationary clutter simultaneously. This framework also shows potential for imaging targets with non-rigid body motion. However, the motion-induced object-displacement compensation performance of this approach is significantly affected by cross-scatterer interference effects.
by Cedric Leonard Logan.
Sc.D.

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46

Brown, Sarah Caroline Mellows. "High resolution polarimetric imaging of biophysical objects using synthetic aperture radar." Thesis, University of Sheffield, 1998. http://etheses.whiterose.ac.uk/10223/.

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A synthetic aperture microwave near-field system is used to image biophysical objects in order to investigate the nature of radar-target interaction. Two different imaging algorithms for focusing data collected over a two-dimensional planar aperture are investigated. The first of these is the single frequency backward propagation technique which is mathematically simple to implement and provides a high degree of resolution. Secondly, a multifrequency development of the backward propagation algorithm is presented and derived from two separate perspectives. This latter algorithm, known as the auto-focusing algorithm, requires no information about the range of the target from the aperture. Full characterisation by simulation of both algorithms is carried out and different filtering techniques are investigated. The backward propagation algorithm is applied to the polarimetric imaging of three different leafless trees and a sugar beet plant at the X-band frequency of 10GHz. The images so produced demonstrate that the backscattered signal is dependent on the orientation of individual tree elements with respect to the polarisation. Furthermore, multiple scattering terms can be identified within the structure of the tree. The auto-focusing algorithm is applied to the polarimetric imaging of two trees at 10GHz and repeat measurements are made over several months. As with the single frequency measurements, the backscattered signal is dependent on the orientation of individual tree elements relative to the polarisation. The relative contributions from the leaves and branches of the trees to the backscattered signal are assessed and found to be seasonally dependent. Measurements are also carried out to investigate the variation of backscatter from a beech tree with varying incidence angle. It is demonstrated that at small angles of incidence, the leaves are the dominant source of backscatter but at large incidence angles, the branches and trunk of the tree have the greatest contrbution.

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Rangarajan, Ranjani. "Inverse Synthetic Aperture Radar Imaging for Multiple Targets Using Compressed Sensing." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416233543.

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48

Lim, Kian Guan. "Battle damage assessment using inverse synthetic aperture radar (ISAR)." Thesis, Monterey, California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1223.

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Approved for public release; distribution in unlimited.
An imaging radar, like ISAR, offers a combatant the capability to perform long range surveillance with high quality imagery for positive target identification. Extending this attractive feature to the battle damage assessment problem (BDA) gives the operator instant viewing of the target's behavior when it is hit. As a consequence, immediate and decisive action can be quickly taken (if required). However, the conventional Fourier processing adopted by most ISAR systems does not provide adequate time resolution to capture the target's dynamic responses during the hit. As a result, the radar image becomes distorted. To improve the time resolution, time-frequency transform (TFT) methods of ISAR imaging have been proposed. Unlike traditional Fourier-based processing, TFT's allows variable time resolution of the entire event that falls within the ISAR coherent integration period to be extracted as part of the imaging process. We have shown in this thesis that the use of linear Short Time-Frequency Transforms allows the translational response of the aircraft caused by a blast force to be clearly extracted. The TFT extracted images not only tell us how the aircraft responds to a blast effect but also provides additional information about the cause of image distortion in the traditional ISAR display.

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Vachon, Paris W. "Synthetic-aperture radar imaging of the ocean surface : theoretical considerations, and experiments with simulated and actual SAR imagery." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27556.

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Three key areas of controversy in synthetic-aperture radar (SAR) imaging of ocean surface waves are considered: first, the nature of Bragg scattering; second, the role, magnitude, and calculation of the scene coherence time; and third, the relevant ocean wave velocities for coherent Doppler modulations. This work begins with a re-derivation and extension of existing SAR imaging theory for point and diffuse targets. Generic, relatively simple, closed-form expressions for the impulse response, the resolution, and the image bandwidth summarize this unified treatment. Theoretical differences between the imagery of point and diffuse targets are pointed out. Based upon these fundamental differences, a statistical testing procedure is formulated to address the question of scene target density. Background ocean surface wave theory is outlined in preparation for discussions of SAR ocean imaging. Of central importance is the role of the phase velocity, which is the speed of translation of the mean pattern of reflectivity, and the orbital motion, which leads to coherent (phase) modulation, and hence to velocity bunching, acceleration defocus, and target decorrelation. Based upon this theoretical background, one- and two-dimensional simulation models are developed. The one-dimensional simulation addresses the effects of various parameters upon the mean image contrast in a velocity bunching model and guides the development of the two-dimensional simulation. The two-dimensional simulation is unique because each target which constitutes the scene is explicitly considered. This leads to a degree of control and flexibility which is not available from actual SAR imagery. Qualitative and quantitative comparisons are drawn between the simulated and actual SAR imagery to address the key areas of controversy. The assertion that Bragg scattering is a coherent process is defended, despite inability to conclusively verify this using SEASAT data. Comparisons between simulation and C-SAR imagery of waves propagating into ice verify the roles of the scene coherence time and the wave phase velocity.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

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Lawlor, Michael Andrew. "A real-time parallel processing system for synthetic aperture sonar." Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360273.

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