Optimization of antenna array pattern used in a spaceborne Synthetic Aperture Radar (SAR) system is considered in this study. A robust evolutionary algorithm, Non-dominated Sorting Genetic Algorithms (the improved NS...Optimization of antenna array pattern used in a spaceborne Synthetic Aperture Radar (SAR) system is considered in this study. A robust evolutionary algorithm, Non-dominated Sorting Genetic Algorithms (the improved NSGA-Ⅱ), is applied on a spaceborne SAR antenna pattern design. The system consists of two objective functions with two constraints. Pareto fronts are generated as a result of multi-objective optimization. After being validated by a test problem ZDT4, the algorithms are used to synthesize spaceborne SAR antenna radiation pattern. The good results with low Ambi- guity-to-Signal Ratio (ASR) and high directivity are obtained in the paper.展开更多
Constellations of regional satellite navigation systems are usually constituted of geostationary satellites (GEO) and inclined geostationary satellites (IGSO) for better service availability. Analysis of real data sho...Constellations of regional satellite navigation systems are usually constituted of geostationary satellites (GEO) and inclined geostationary satellites (IGSO) for better service availability. Analysis of real data shows that the pseudorange measurements of these two types of satellites contain significant multipath errors and code noise, and the multipath for GEO is extremely serious, which is harmful to system services. In contrast, multipath error of carrier phase measurements is less than 3 cm, which is smaller than the multipath of pseudorange measurements by two orders of magnitude. Using a particular combination of pseudorange and dual-frequency carrier phase measurements, the pseudorange multipath errors are detected, and their time varying features are analyzed. A real-time multipath correction algorithm is proposed in this paper, which is called CNMC (Code Noise and Multipath Correction). The algorithm decreases the influence of the multipath error and therefore ensures the performance of the system. Data processing experiments show that the multipath error level may be reduced from 0.5 m to 0.15 m by using this algorithm, and 60% of GEO multipath errors and 42% of IGSO multipath errors are successfully corrected with CNMC. Positioning experiments are performed with a constellation of 3 GEO plus 3 IGSO satellites. For dual-frequency users the East-West position accuracy is improved from 1.31 m to 0.94 m by using the CNMC algorithm, the South-North position accuracy is improved from 2.62 m to 2.29 m, and the vertical position accuracy is improved from 4.25 m to 3.05 m. After correcting multipath errors, the three-dimensional position accuracy is improved from 5.16 m to 3.94 m.展开更多
文摘Optimization of antenna array pattern used in a spaceborne Synthetic Aperture Radar (SAR) system is considered in this study. A robust evolutionary algorithm, Non-dominated Sorting Genetic Algorithms (the improved NSGA-Ⅱ), is applied on a spaceborne SAR antenna pattern design. The system consists of two objective functions with two constraints. Pareto fronts are generated as a result of multi-objective optimization. After being validated by a test problem ZDT4, the algorithms are used to synthesize spaceborne SAR antenna radiation pattern. The good results with low Ambi- guity-to-Signal Ratio (ASR) and high directivity are obtained in the paper.
基金supported by the National High Technology Research and Development Program of China (863) (Grant Nos.2009Z12A324 and 2009AA12Z328)the National Natural Science Foundation of China (Grant Nos. 10703011, 11073047 and 11033004)the Science and Technology Commission of Shanghai (Grant No. 06DZ22101)
文摘Constellations of regional satellite navigation systems are usually constituted of geostationary satellites (GEO) and inclined geostationary satellites (IGSO) for better service availability. Analysis of real data shows that the pseudorange measurements of these two types of satellites contain significant multipath errors and code noise, and the multipath for GEO is extremely serious, which is harmful to system services. In contrast, multipath error of carrier phase measurements is less than 3 cm, which is smaller than the multipath of pseudorange measurements by two orders of magnitude. Using a particular combination of pseudorange and dual-frequency carrier phase measurements, the pseudorange multipath errors are detected, and their time varying features are analyzed. A real-time multipath correction algorithm is proposed in this paper, which is called CNMC (Code Noise and Multipath Correction). The algorithm decreases the influence of the multipath error and therefore ensures the performance of the system. Data processing experiments show that the multipath error level may be reduced from 0.5 m to 0.15 m by using this algorithm, and 60% of GEO multipath errors and 42% of IGSO multipath errors are successfully corrected with CNMC. Positioning experiments are performed with a constellation of 3 GEO plus 3 IGSO satellites. For dual-frequency users the East-West position accuracy is improved from 1.31 m to 0.94 m by using the CNMC algorithm, the South-North position accuracy is improved from 2.62 m to 2.29 m, and the vertical position accuracy is improved from 4.25 m to 3.05 m. After correcting multipath errors, the three-dimensional position accuracy is improved from 5.16 m to 3.94 m.
