带有并联电阻的双调谐滤波器参数特性分析

高压直流输电系统中,双调谐滤波器使用广泛。将电阻并联在双调谐滤波器上可使双调谐滤波器获得较好的高通滤波的性能,并减小滤波器之间及与系统之间发生谐振的可能性,但同时加大两个串联谐振附近的阻抗,也增加了整个滤波器的谐波有功损耗。通过分析双调谐滤波器和带有并联电阻的双调谐滤波器的元件参数特新,比较两种滤波器的元件参数对谐振频率灵敏度影响,确定了带有并联电阻的双调谐滤波器元件参数变化对系统影响明显优于普通双调谐滤波器。     

A novel artificial noise aided security scheme to resist blind source separation attacks

In this paper, we discuss the physical layer security from a new angle of view and propose a novel approach to resist some attacks in signal processing perspective. The scenario considered in this paper is that the eavesdropper has the similar channel performance compared to the legitimate receiver. We design the optimal artificial noise （AN） to resist the attacks of the eavesdropper who uses the blind source separation （BSS） technology to reconstruct the secret information. For speech signals, the optimal AN is obtained by minimizing the maximum of the correlation coefficients between the source signal and the received signals at Eve and the correlation coefficients between the source signal and separated results of BSS. For binary phase shift keying （BPSK） signals, we maximize the minimum bit error rates （BERs） of the separated signals and the obtained signals at Eve. Moreover, we consider the AN design from the point of breaking the BSS conditions, and propose a method by changing the correlation coefficient randomly. The simulation results show that the AN we proposed has better performance than that of the white Gaussian AN to resist the BSS attacks for both speech signals and the BPSK signals.     

减缩型聚羧酸减水剂的合成及其性能

选择了一种具有减缩性能的聚醚基团,将其接枝引入到梳状聚羧酸共聚物分子主链中,制得了减缩型聚羧酸减水剂HHG,用红外光谱表征了HHG结构,并考察了其对溶液表面张力以及水泥胶砂性能的影响。结果表明:本研究制备的HHG不仅拥有较好的减水效果,而且能够将溶液表面张力降低至45 mN/m,降低了30.87%的水泥胶砂28d干燥收缩率。较之萘系,脂肪族及其普通聚羧酸减水剂,更适宜应用于对减缩抗裂有较高要求的混凝土工程。     

DM6446与DDR2接口的信号完整性研究

为了研究电路拓扑结构对信号完整性的影响，采用Hyperlynx仿真软件，在布线前仿真软件LineSim中对TMS320DM6446与DDR2间的3种不同拓扑结构（树形结构、菊花链结构和星型结构）进行了信号完整性仿真，并通过布线后仿真工具BoardSim对布线前仿真结果进行了验证．研究结果表明，基于TMS320DM6446的数字视频处理系统适合采用星型结构来设计时钟信号网络．软件仿真可以在产品研发之初找到并解决潜在的信号完整性问题，最大限度地减小产品设计失败的概率，提高电路系统工作可靠性．