针对无人机数据链系统中下行宽带信号的隐蔽性和抗截获性不足的问题,提出宽带多进制正交扩频方案,结合宽带多进制正交扩频调制器的要求,设计了基于多相结构的FIR成形滤波器及高中频数字调制器。阐述了成形滤波的基本原理,高速FIR成形滤...针对无人机数据链系统中下行宽带信号的隐蔽性和抗截获性不足的问题,提出宽带多进制正交扩频方案,结合宽带多进制正交扩频调制器的要求,设计了基于多相结构的FIR成形滤波器及高中频数字调制器。阐述了成形滤波的基本原理,高速FIR成形滤波器的多相结构,运用Matlab和Quartus Ⅱ软件设计了多相成形滤波器,并且采用并行直接数字频率合成(Direct Digital Synthesis,DDS)和高速DA实现了宽带扩频数据高中频数字调制。结果表明,采用该设计方法的调制器具有良好的频谱特性。展开更多
Studies show that the Tianshan orogenic belt was built in the late stage of the Paleozoic, as evidenced by the Permian red molasses and foreland basins, which are distributed in parallel with the Tianshan belt, indica...Studies show that the Tianshan orogenic belt was built in the late stage of the Paleozoic, as evidenced by the Permian red molasses and foreland basins, which are distributed in parallel with the Tianshan belt, indicating that an intense folding and uplifting event took place. During the Triassic, this orogenic belt was strongly eroded, and basins were further developed. Starting from the Jurassic, a within-plate regional extension occurred, forming a series of Jurassic-Paleogene extensional basins in the peneplaned Tianshan region. Since the Neogene, a collision event between the Indian and the Eurasian plates that took place on the southern side of the Tianshan belt has caused a strong intra-continental orogeny, which is characterized by thrusting and folding. Extremely thick coarse conglomerate and sandy conglomerate of the Xiyu Formation of Neogene System were accumulated unconformably on the Tianshan piedmont. Studies have revealed that the strong compression caused by the Indian-Eurasian collision had a profound influence over the orogenic belt in the hinterland, and MesozoiC-Cenozoic brittle deformed structures superposed on the ductile deformed Paleozoic rocks. The Mesozoic extensional basins were converted into Cenozoic compressional basins. The deformation in the basins is featured by step thrusts and fault-related folds. Statistics of joints show that the principal compressive stress since the Neogene is in a N-S direction. Meanwhile, owing to the underthrusting of the basin toward the orogenic belt, the Paleozoic strata were thrust on the Meso-Cenozoic rocks as tectonic slices, revealing distinct kinematic features in different geologic units. The basin-range coupling zones are characterized by intensive compression, folding and thrusting, accompanied by local sub-E-W-trending strike-slip faults. In the Tianshan region, Cenozoic thrusting is the most common basin-range coupling mode. The folding and faulting of Mesozoic sedimentary rocks, spontaneous combustion of Jurassic coal layers and formation of展开更多
文摘针对无人机数据链系统中下行宽带信号的隐蔽性和抗截获性不足的问题,提出宽带多进制正交扩频方案,结合宽带多进制正交扩频调制器的要求,设计了基于多相结构的FIR成形滤波器及高中频数字调制器。阐述了成形滤波的基本原理,高速FIR成形滤波器的多相结构,运用Matlab和Quartus Ⅱ软件设计了多相成形滤波器,并且采用并行直接数字频率合成(Direct Digital Synthesis,DDS)和高速DA实现了宽带扩频数据高中频数字调制。结果表明,采用该设计方法的调制器具有良好的频谱特性。
基金supports from the National 973 Project on western China No.2001CB409804the key project of National Natural Science Foundation of China No.49832040.
文摘Studies show that the Tianshan orogenic belt was built in the late stage of the Paleozoic, as evidenced by the Permian red molasses and foreland basins, which are distributed in parallel with the Tianshan belt, indicating that an intense folding and uplifting event took place. During the Triassic, this orogenic belt was strongly eroded, and basins were further developed. Starting from the Jurassic, a within-plate regional extension occurred, forming a series of Jurassic-Paleogene extensional basins in the peneplaned Tianshan region. Since the Neogene, a collision event between the Indian and the Eurasian plates that took place on the southern side of the Tianshan belt has caused a strong intra-continental orogeny, which is characterized by thrusting and folding. Extremely thick coarse conglomerate and sandy conglomerate of the Xiyu Formation of Neogene System were accumulated unconformably on the Tianshan piedmont. Studies have revealed that the strong compression caused by the Indian-Eurasian collision had a profound influence over the orogenic belt in the hinterland, and MesozoiC-Cenozoic brittle deformed structures superposed on the ductile deformed Paleozoic rocks. The Mesozoic extensional basins were converted into Cenozoic compressional basins. The deformation in the basins is featured by step thrusts and fault-related folds. Statistics of joints show that the principal compressive stress since the Neogene is in a N-S direction. Meanwhile, owing to the underthrusting of the basin toward the orogenic belt, the Paleozoic strata were thrust on the Meso-Cenozoic rocks as tectonic slices, revealing distinct kinematic features in different geologic units. The basin-range coupling zones are characterized by intensive compression, folding and thrusting, accompanied by local sub-E-W-trending strike-slip faults. In the Tianshan region, Cenozoic thrusting is the most common basin-range coupling mode. The folding and faulting of Mesozoic sedimentary rocks, spontaneous combustion of Jurassic coal layers and formation of
