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Synthetic Aperture Radar (SAR) is one of the main tools for microwave remote sensing because of its multi-dimensional high resolution characteristics and the capability to operate in nearly all weather conditions, day and night. The University of Nebraska-Lincoln (UNL) initiated the design and development of a low-cost airborne SAR in January 2001 to support our Airborne Remote Sensing Program. The objectives of this project are separated into various evolutionary stages. This thesis will focus on the initial phase of design and construction of an X-band high range resolution radar (HRR) using basic RF /microwave and digital components. The following stages will expand on the HRR design to achieve a functioning X-band airborne SAR for the remote sensing of underlying vegetation parameters (tree height, leaf area index, biomass content, etc.) from a low altitude platform from a range of 1000 meters. The SAR system is an X-band, stepped-chirp FM, single polarization radar system. One of its unique features is that the signal generation consists of a timing-controlled D /A converter and VCO arrangement to generate the step-chirp signal, thereby allowing for less design complexity and a much lower overall system cost.
The individual block-segments of the SAR include a stepped-chirp FM waveform synthesizer, transmission and receive paths, antennas, quadrature detection and image signal processing. The system underwent rigorous in house laboratory testing and subsequent outdoor field-testing from a van-mounted boom where preliminary HRR one-dimensional images were obtained. It is anticipated that the following progression of development for this HRR system will be to use this design as a basis towards fully coherent, data acquisition from an airborne platform.
Advisor: Ram M. Narayanan