A Matrix Inversion Normalized Least Mean Square (MI-NLMS) adaptive beamforming algorithm was developed for smart antenna application. The MI-NLMS which combined the individual good aspects of Sample Matrix Inversion (...A Matrix Inversion Normalized Least Mean Square (MI-NLMS) adaptive beamforming algorithm was developed for smart antenna application. The MI-NLMS which combined the individual good aspects of Sample Matrix Inversion (SMI) and the Normalized Least Mean Square (NLMS) algorithms is described. Simulation results showed that the less complexity MI-NLMS yields 15 dB improvements in interference suppression and 5 dB gain enhancement over LMS algorithm, converges from the initial iteration and achieves 24% BER improvements at cochannel interference equal to 5. For the case of 4-element uniform linear array antenna, MI-NLMS achieved 76% BER reduction over LMS algorithm.展开更多
Adaptive modulation can optimize the spectrum efficiency and system performance with the channel state information achieved by the long-range channel prediction. To avoid re-estimating channel correlation function as ...Adaptive modulation can optimize the spectrum efficiency and system performance with the channel state information achieved by the long-range channel prediction. To avoid re-estimating channel correlation function as the channel stationarity varies and to track the channel adaptively, LMS （Least-Mean-Square） based long-range channel prediction is discussed in the existing literature, but it needs long observation interval to reach the convergence. Given that all OFDM （Orthogonal Frequency Division Multiplexing） subcarriers have the identical time-domain correlation and stationarity during the same time interval, this paper proposed a 2-D LMS based predictor which updates the filter weights in both time and frequency domain. The proposed scheme can effectively decrease the observation intervals and significantly speed up the convergence than the conventional LMS and Parallel LMS （PLMS）. Complexity analysis and simulation results prove that the proposed scheme can improve the BER （Bit Error Rate） performance and spectrum efficiency with negligible complexity increase.展开更多
Based on the good time-frequency localization of the wavelet packet modulation （WPM） system and the analysis of the muhitone （MT） interference, an improved WPM narrow band interference （NBI） rejection system usi...Based on the good time-frequency localization of the wavelet packet modulation （WPM） system and the analysis of the muhitone （MT） interference, an improved WPM narrow band interference （NBI） rejection system using an adaptive least mean square （LMS） algorithm is discussed in this paper. In the WPM interference rejection system, according to the structure of the wavelet packet tree （WFF） and the characteristic of the MT interference, the demodulated WPM signal which contains the interference component is filtered using an adaptive LMS filtering implementation. Theoretical analysis and simulation resuits show that the proposed method improves the bit error rate （BER） performance of the WPM system in the presence of MT interference.展开更多
随着电力电子设备广泛应用于工业生产的各个领域,电网受到谐波污染的问题日益严重,混合有源滤波器(Hybrid Active Power Filter,HAPF)作为一种有效的谐波抑制手段,受到了广泛关注。然而传统谐波电流检测算法需要受到低通滤波器(LPF)性...随着电力电子设备广泛应用于工业生产的各个领域,电网受到谐波污染的问题日益严重,混合有源滤波器(Hybrid Active Power Filter,HAPF)作为一种有效的谐波抑制手段,受到了广泛关注。然而传统谐波电流检测算法需要受到低通滤波器(LPF)性能的制约,导致系统存在谐波检测精度与响应速度之间的矛盾,滤波效果往往受到限制。因此,采用一种基于LMS自适应滤波器的HAPF控制策略,解决了动静态性能无法兼顾的问题。最后设计了一个在输入电压为220 V、额定频率50 Hz、谐波源为三相整流器带可变负载的系统,并利用Matlab/Simulink验证该方案的正确性,研究结果表明,基于LMS自适应滤波器的HAPF控制器滤波效果良好,准确性和实时性较强,能够显著提高系统的控制性能和抗干扰能力,具有广阔的应用前景。展开更多
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
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
基金Project supported by the IRPA Secretariat, Ministry of Science,Technology and Environment of Malaysia (No. 04-02-02-0029) andthe Zamalah Scheme
文摘A Matrix Inversion Normalized Least Mean Square (MI-NLMS) adaptive beamforming algorithm was developed for smart antenna application. The MI-NLMS which combined the individual good aspects of Sample Matrix Inversion (SMI) and the Normalized Least Mean Square (NLMS) algorithms is described. Simulation results showed that the less complexity MI-NLMS yields 15 dB improvements in interference suppression and 5 dB gain enhancement over LMS algorithm, converges from the initial iteration and achieves 24% BER improvements at cochannel interference equal to 5. For the case of 4-element uniform linear array antenna, MI-NLMS achieved 76% BER reduction over LMS algorithm.
基金Supported by the National Natural Science Foundation of China (No.60496311).
文摘Adaptive modulation can optimize the spectrum efficiency and system performance with the channel state information achieved by the long-range channel prediction. To avoid re-estimating channel correlation function as the channel stationarity varies and to track the channel adaptively, LMS （Least-Mean-Square） based long-range channel prediction is discussed in the existing literature, but it needs long observation interval to reach the convergence. Given that all OFDM （Orthogonal Frequency Division Multiplexing） subcarriers have the identical time-domain correlation and stationarity during the same time interval, this paper proposed a 2-D LMS based predictor which updates the filter weights in both time and frequency domain. The proposed scheme can effectively decrease the observation intervals and significantly speed up the convergence than the conventional LMS and Parallel LMS （PLMS）. Complexity analysis and simulation results prove that the proposed scheme can improve the BER （Bit Error Rate） performance and spectrum efficiency with negligible complexity increase.
基金Supported by the National Natural Science Foundation of China （No. 60532030）.
文摘Based on the good time-frequency localization of the wavelet packet modulation （WPM） system and the analysis of the muhitone （MT） interference, an improved WPM narrow band interference （NBI） rejection system using an adaptive least mean square （LMS） algorithm is discussed in this paper. In the WPM interference rejection system, according to the structure of the wavelet packet tree （WFF） and the characteristic of the MT interference, the demodulated WPM signal which contains the interference component is filtered using an adaptive LMS filtering implementation. Theoretical analysis and simulation resuits show that the proposed method improves the bit error rate （BER） performance of the WPM system in the presence of MT interference.
文摘随着电力电子设备广泛应用于工业生产的各个领域,电网受到谐波污染的问题日益严重,混合有源滤波器(Hybrid Active Power Filter,HAPF)作为一种有效的谐波抑制手段,受到了广泛关注。然而传统谐波电流检测算法需要受到低通滤波器(LPF)性能的制约,导致系统存在谐波检测精度与响应速度之间的矛盾,滤波效果往往受到限制。因此,采用一种基于LMS自适应滤波器的HAPF控制策略,解决了动静态性能无法兼顾的问题。最后设计了一个在输入电压为220 V、额定频率50 Hz、谐波源为三相整流器带可变负载的系统,并利用Matlab/Simulink验证该方案的正确性,研究结果表明,基于LMS自适应滤波器的HAPF控制器滤波效果良好,准确性和实时性较强,能够显著提高系统的控制性能和抗干扰能力,具有广阔的应用前景。
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。
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.
