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  • 基于FPGA的高效灵活性数字正交下变频器设计

    数字正交下变频器DDC是数字接收机系统中的核心部件,其作用是将ADC数字化后输出的高速中频信号进行下变频、抽取降速和低通滤波,使之变为适合处理的基带信号.给出了DDC各模块在FPGA中高效实现的方法,并且利用嵌入式逻辑分析仪对系统加载板卡后的实时运行结果进行了测试分析.
    徐伟,王旭东 - 电子技术应用
    文章来源: 万方数据
  • The thermal scratch seriously affects the surface quality of the cold rolled stainless steel strip. Some researchers have carried out qualitative and theoretical studies in this field. However, there is currently a lack of research on effective forecast and control of thermal scratch defects in practical production, especially in tandem cold rolling. In order to establish precise mathematical model of oil film thickness in deformation zone, the lubrication in cold rolling process of SUS410L stainless steel strip is studied, and major factors affecting oil film thickness are also analyzed. According to the principle of statistics, mathematical model of critical oil film thickness in deformation zone for thermal scratch is built, with fitting and regression analytical method, and then based on temperature comparison method, the criterion for deciding thermal scratch defects is put forward. Storing and calling data through SQL Server 2010, a software on thermal scratch defects control is developed through Microsoft Visual Studio 2008 by MFC technique for stainless steel in tandem cold rolling, and then it is put into practical production. Statistics indicate that the hit rate of thermal scratch is as high as 92.38%, and the occurrence rate of thermal scratch is decreased by 89.13%. Owing to the application of the software, the rolling speed is increased by approximately 9.3%. The software developed provides an effective solution to the problem of thermal scratch defects in tandem cold rolling, and helps to promote products surface quality of stainless steel strips in practical production.
     - 中国机械工程学报
    文章来源: 万方数据
  • 基于认知系统的编码调制体系研究

    利用NMSK(N重最小频移键控)的旁瓣快速衰减特性,提出了一种新型OFDM-NMSK编码调制体系用于降低OFDM认知无线电系统的带外干扰.该方法仅通过关闭干扰频段上的相应NMSK子载波,能够快速生成符合要求的频谱凹槽深度,从而实现与其地窄带系统的共存.理论与仿真表明,与传统的相邻频带编码( AFC)方法相比,OFDM-NMSK编码效果更佳.
    唐菁敏,冯思泉,龙华,邵玉斌 - 电子技术应用
    文章来源: 万方数据
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