传统的最小均方误差(Least Mean Square,LMS)算法具有计算量低、易于实现的优点,广泛应用于各种场景,但其平均收敛速度和稳态误差相互制约。基于箕舌线函数(Tongue Line)的变步长LMS(Tongue Line Least Mean Square,TLLMS)算法引入箕舌...传统的最小均方误差(Least Mean Square,LMS)算法具有计算量低、易于实现的优点,广泛应用于各种场景,但其平均收敛速度和稳态误差相互制约。基于箕舌线函数(Tongue Line)的变步长LMS(Tongue Line Least Mean Square,TLLMS)算法引入箕舌线函数,改进了步长更新公式,从而提高了收敛速度并降低了稳态误差。然而,该算法的步长易受噪声干扰,导致滤波器权值在最优权值附近波动。为此,文章提出了改进箕舌线变步长LMS(Improved Tongue Line Least Mean Square,ITLLMS)算法。该算法进一步优化了步长更新公式,消除了输入端不相关噪声的干扰,以最小化收敛时的稳态误差,并加入上一步步长的影响以增强系统的跟踪能力。将ITLLMS算法应用于自适应噪声抵消系统的实验结果表明,与基于相关特性(Correlation Characteristic)的箕舌线变步长LMS(Correlation Characteristic Tongue Line Least Mean Square,CCTLLMS)算法相比,文章提出的ITLLMS算法具有更快的收敛速度、更低的稳态误差以及更低的计算量。展开更多
为了避免单个滤波器在收敛速度与稳态误差上相互制约,从而导致系统性能降低的问题,本文采用凸组合最小均方算法(Combined Least Mean Square,CLMS),将快速滤波器和慢速滤波器并联使用,同时为进一步改善CLMS算法的性能,对已有的变步长凸...为了避免单个滤波器在收敛速度与稳态误差上相互制约,从而导致系统性能降低的问题,本文采用凸组合最小均方算法(Combined Least Mean Square,CLMS),将快速滤波器和慢速滤波器并联使用,同时为进一步改善CLMS算法的性能,对已有的变步长凸组合最小均方算法(Variable Step-size Convex Combination of LMS,VSCLMS)做出改进,提出了一种新的VSCLMS算法.在该算法中,对快速滤波器选用以最小均方权值偏差(Minimization of Mean Square Weight Error,MMSWE)为准则的按步分析的变步长滤波器;对慢速滤波器采用以稳态最小均方误差(Least Mean Square,LMS)为准则的固定步长滤波器.通过理论分析与仿真实验表明,该算法能够在噪声、时变以及非平稳的环境下保持较好的随动性能,且在各个阶段均保持良好的收敛性,与传统的CLMS、VSCLMS算法相比,不仅具有更快的收敛速度,而且拥有稳定的均方性能和较优的跟踪性能,为自适应滤波算法的研究提供了一条可行途径.展开更多
It is very important for high temperature superconducting electronic devices to increase the grain size of YBCO epitaxial films because it can effectively reduce the defects and improve the probability of successful p...It is very important for high temperature superconducting electronic devices to increase the grain size of YBCO epitaxial films because it can effectively reduce the defects and improve the probability of successful preparation of Josephson junction.In this study,YBa_(2)Cu_(3)O_(7-δ)(YBCO)films with grain size in excess of 1.5μm were successfully prepared by the directly heating SrTiO_(3)substrates coated by Si C on their back.Interestingly,the grain size of YBCO film is enhanced greatly by this directly heating method,and the critical temperature TCand critical current density JCof YBCO films are as high as 91.5 K and 3.5 MA/cm^(2),respectively.Compared with the traditional indirect heating method,which involves applying silver paste and then using a heat soaking block(e.g.Inconel 600),this direct heating method effectively enhances the grain size of YBCO film and the possibility of successful preparation of Josephson junction.展开更多
文摘传统的最小均方误差(Least Mean Square,LMS)算法具有计算量低、易于实现的优点,广泛应用于各种场景,但其平均收敛速度和稳态误差相互制约。基于箕舌线函数(Tongue Line)的变步长LMS(Tongue Line Least Mean Square,TLLMS)算法引入箕舌线函数,改进了步长更新公式,从而提高了收敛速度并降低了稳态误差。然而,该算法的步长易受噪声干扰,导致滤波器权值在最优权值附近波动。为此,文章提出了改进箕舌线变步长LMS(Improved Tongue Line Least Mean Square,ITLLMS)算法。该算法进一步优化了步长更新公式,消除了输入端不相关噪声的干扰,以最小化收敛时的稳态误差,并加入上一步步长的影响以增强系统的跟踪能力。将ITLLMS算法应用于自适应噪声抵消系统的实验结果表明,与基于相关特性(Correlation Characteristic)的箕舌线变步长LMS(Correlation Characteristic Tongue Line Least Mean Square,CCTLLMS)算法相比,文章提出的ITLLMS算法具有更快的收敛速度、更低的稳态误差以及更低的计算量。
文摘为了避免单个滤波器在收敛速度与稳态误差上相互制约,从而导致系统性能降低的问题,本文采用凸组合最小均方算法(Combined Least Mean Square,CLMS),将快速滤波器和慢速滤波器并联使用,同时为进一步改善CLMS算法的性能,对已有的变步长凸组合最小均方算法(Variable Step-size Convex Combination of LMS,VSCLMS)做出改进,提出了一种新的VSCLMS算法.在该算法中,对快速滤波器选用以最小均方权值偏差(Minimization of Mean Square Weight Error,MMSWE)为准则的按步分析的变步长滤波器;对慢速滤波器采用以稳态最小均方误差(Least Mean Square,LMS)为准则的固定步长滤波器.通过理论分析与仿真实验表明,该算法能够在噪声、时变以及非平稳的环境下保持较好的随动性能,且在各个阶段均保持良好的收敛性,与传统的CLMS、VSCLMS算法相比,不仅具有更快的收敛速度,而且拥有稳定的均方性能和较优的跟踪性能,为自适应滤波算法的研究提供了一条可行途径.
基金Project supported by the National Key Research and Development Program of China(Grant No.2023YFF0720500)the State Key Program of the National Natural Science Foundation of China(Grant No.U22A2019)the National Key Project(Grant No.22-05-CXZX-04-03-15)。
文摘It is very important for high temperature superconducting electronic devices to increase the grain size of YBCO epitaxial films because it can effectively reduce the defects and improve the probability of successful preparation of Josephson junction.In this study,YBa_(2)Cu_(3)O_(7-δ)(YBCO)films with grain size in excess of 1.5μm were successfully prepared by the directly heating SrTiO_(3)substrates coated by Si C on their back.Interestingly,the grain size of YBCO film is enhanced greatly by this directly heating method,and the critical temperature TCand critical current density JCof YBCO films are as high as 91.5 K and 3.5 MA/cm^(2),respectively.Compared with the traditional indirect heating method,which involves applying silver paste and then using a heat soaking block(e.g.Inconel 600),this direct heating method effectively enhances the grain size of YBCO film and the possibility of successful preparation of Josephson junction.
