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作者 Farooq, Jawad
書名 Frequency diversity for improving synthetic aperture radar imaging
國際標準書號 9781109078756
book jacket
說明 135 p
附註 Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1837
Thesis (Ph.D.)--Air Force Institute of Technology, 2009
Synthetic aperture radar (SAR) is a critical battlefield enabler as it provides imagery during day or night and in all-weather conditions. SAR image resolution is a function of the transmit signal parameters and collection time where classic measures of resolution depend on waveform bandwidth, operating frequency and sensor flight path. Improving resolution is challenging because of the two dimensional resolution: down-range and cross range. Decades of research exist for the down-range dimension, but very little exists for improving cross-range dimension
Fine cross-range resolution requires a long collection time, which increases an airborne sensor's exposure to hostile forces and causes undesirable defocusing effects from uncontrolled platform motion and moving targets in the scene. For the first time, this research investigates techniques to improve cross-range resolution using waveform diversity. The importance of waveform diversity has been highlighted by senior U.S. Air Force leaders as a growing and vital part of future operational capabilities
In this work, a novel theoretical framework is presented for using recent advances in frequency diversity arrays (FDAs). Unlike a conventional array, the FDA simultaneously transmits a unique frequency from each element in the array. As a result, special time and space properties of the radiation pattern are exploited to improve cross-range resolution. The idealized FDA radiation pattern is compared with and validated against a full-wave electromagnetic solver, and it is shown that the conventional array is a special case of the FDA. A new signal model, based on the FDA, is used to simulate SAR imagery of ideal point mass targets and the new model is used to derive the impulse response function of the SAR system, which is rarely achievable with other analytic methods
This work also presents an innovative solution for using the convolution back-projection algorithm, the gold standard in SAR image processing, and is a significant advantage of the proposed FDA model. The new FDA model and novel SAR system concept of operation are shown to reduce collection time by 33 percent while achieving a 4.5 dB improvement in cross-range resolution as compared to traditional imaging systems
School code: 0002
Host Item Dissertation Abstracts International 70-03B
主題 Engineering, Electronics and Electrical
0544
Alt Author Air Force Institute of Technology
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