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Full-Text Articles in Engineering
Backprojection For Synthetic Aperture Radar, Michael Israel Duersch
Backprojection For Synthetic Aperture Radar, Michael Israel Duersch
Theses and Dissertations
Synthetic aperture radar (SAR) is a type of radar capable of high-resolution coherent imaging. In order to produce coherent imagery from raw SAR data, an image formation algorithm is employed. The various image formation algorithms have strengths and weaknesses. As this work shows, time-domain backprojection is one algorithm whose strengths are particularly well-suited to use at low-altitudes. This work presents novel research in three areas regarding time-domain backprojection. The first key contribution of this work is a detailed analysis of SAR time-domain backprojection. The work derives a general form of backprojection from first principles. It characterizes the sensitivities of backprojection …
Development Of A Grond-Based High-Resolution 3d-Sar System For Studying The Microwave Scattering Characteristics Of Trees, Justin Frank Penner
Development Of A Grond-Based High-Resolution 3d-Sar System For Studying The Microwave Scattering Characteristics Of Trees, Justin Frank Penner
Theses and Dissertations
This thesis presents the development of a high-resolution ground-based 3D-SAR system and investigates its application to microwave-vegetation studies. The development process of the system is detailed including an enumeration of high-level requirements, discussions on key design issues, and detailed descriptions of the system down to a component level. The system operates on a 5.4 GHz (C-band) signal, provides a synthetic aperture area of 1.7 m x 1.7 m, and offers resolution of 0.75 m x 0.3 m x 0.3 m (range x azimuth x elevation). The system is employed on several trees with varying physical characteristics. The resulting imagery demonstrates …
Generalized Image Formation For Pulsed And Lfm-Cw Synthetic Aperture Radar, Evan C. Zaugg
Generalized Image Formation For Pulsed And Lfm-Cw Synthetic Aperture Radar, Evan C. Zaugg
Theses and Dissertations
Approximations made in the traditional signal model for synthetic aperture radar (SAR) processing cause defocusing of the radar images when the system operates under conditions where the approximations lose validity. This dissertation investigates a number of these approximations and presents algorithmic improvements based on generalizations of the approxmations of the SAR signal model. These improvements result in better focused imagery from SAR systems with varied designs and parameters. Among the advancements presented is the development of a generalized chirp-scaling algorithm and a generalized frequency scaling algorithm to address the problems caused by approximations based on a Taylor series expansion of …
Multi-Aperture Coherent Change Detection And Interferometry For Synthetic Aperture Radar, David D. Madsen
Multi-Aperture Coherent Change Detection And Interferometry For Synthetic Aperture Radar, David D. Madsen
Theses and Dissertations
Interferometry and coherent change detection (CCD) utilize phase differences between complex SAR images to find terrain height and to detect small changes between images, respectively. A new method for improving interferometry and CCD using multiple sub-apertures is proposed. Using backprojection processing, multiple sub-aperture images are created for a pair of flights. An interferogram and coherence map is made from each sub-aperture. For CCD, each sub-aperture coherence map offers an independent estimate of the coherence over the same area. By combining coherence maps, low coherence areas associated with residual motion errors are reduced, shadowed areas are minimized, and the overall coherence …
Design Of A Continuous-Wave Synthetic Aperture Radar System With Analog Dechirp, Matthew C. Edwards
Design Of A Continuous-Wave Synthetic Aperture Radar System With Analog Dechirp, Matthew C. Edwards
Theses and Dissertations
This thesis presents a design methodology for continuous wave (CW) synthetic aperture radar (SAR) systems. The focus is on design considerations specific to small, low-power systems suitable for operation on small aircraft and unmanned aerial vehicles (UAVs). Well-known results which have been derived in other works, such as the radar equation, are explained in the context of low-power, CW systems. Additionally, design issues unique to CW SAR are addressed and the results generalized. A method for controlling feedthrough between antennas is developed, and the resulting limitations on swath width are discussed. Methods are developed which allow an engineer to design …
A Detailed Look At The Omega-K Algorithm For Processing Synthetic Aperture Radar Data, Matthew A. Tolman
A Detailed Look At The Omega-K Algorithm For Processing Synthetic Aperture Radar Data, Matthew A. Tolman
Theses and Dissertations
In this thesis, the Omega-k algorithm used for processing stripmap synthetic aperture radar (SAR) data is explored in detail. While the original Omega-k algorithm does not achieve the same SNR as a matched filter, a modification is presented which enables the algorithm to nearly achieve that SNR. It is shown that the focused point spread function obtained when the Omega-k algorithm is used differs in important ways from the output of a modified version of the matched filter. Spread out sidelobes and a stretched mainlobe are observed when the data is processed by the Omega-k algorithm. These differences may increase …
Byu Micro-Sar: A Very Small, Low-Power Lfm-Cw Synthetic Aperture Radar, Michael Israel Duersch
Byu Micro-Sar: A Very Small, Low-Power Lfm-Cw Synthetic Aperture Radar, Michael Israel Duersch
Theses and Dissertations
Brigham Young University has developed a low-cost, light-weight, and low power consumption SAR for flight on a small unmanned aerial vehicle (UAV) at low altitudes. This micro-SAR, or uSAR, consumes only 18 watts of power, ideal for application on a small UAV. To meet these constraints, a linear frequency modulation-continuous wave (LFM-CW) transmit signal is utilized. Use of an LFM-CW signal introduces some differences from the typical strip map SAR processing model that must be addressed in signal processing algorithms. This thesis presents a derivation of the LFM-CW signal model and the associated image processing algorithms used for the uSAR …
Motion Compensation Of Interferometric Synthetic Aperture Radar, David P. Duncan
Motion Compensation Of Interferometric Synthetic Aperture Radar, David P. Duncan
Theses and Dissertations
Deviations from a nominal, straight-line flight path of a synthetic aperture radar (SAR) lead to inaccurate and defocused radar images. This thesis is an investigation into the improvement of the motion compensation algorithm created for the BYU inteferometric synthetic aperture radar, YINSAR. The existing BYU SAR processing algorithm produces improved radar imagery but does not fully account for variations in attitude (roll, pitch, yaw) and does not function well with large position deviations. Results in this thesis demonstrate that a higher order motion compensation algorithm is not as effective as using a segmented reference track, coupled with the current lower-order …
The Phase Gradient Autofocus Algorithm With Range Dependent Stripmap Sar, James S. Bates
The Phase Gradient Autofocus Algorithm With Range Dependent Stripmap Sar, James S. Bates
Theses and Dissertations
The Phase Gradient Autofocus (PGA) algorithm is widely used in spotlight mode SAR for motion compensation. The Maximum Likelihood PGA (ML PGA) algorithm has been shown to be a superior autofocus method. The PGA is restricted to high altitude aircraft. Since lower altitude SARs have significant range dependencies that cannot be ignored, the PGA could not be used. This thesis eliminates the high altitude restriction and extends the PGA for use with all spotlight SARs. The new algorithm is tested with three images. Each image has a unique quality. A desert image provides a low signal to clutter ratio with …