Sonar generated acoustic signals transmitted in underwater channel for distant communications are affected by numerous factors like ambient noise, making them nonlinear and non-stationary in nature. In recent years, t...Sonar generated acoustic signals transmitted in underwater channel for distant communications are affected by numerous factors like ambient noise, making them nonlinear and non-stationary in nature. In recent years, the application of Empirical Mode Decomposition(EMD) technique to analyze nonlinear and non-stationary signals has gained much attention. It is an empirical approach to decompose a signal into a set of oscillatory modes known as intrinsic mode functions(IMFs). In general, Hilbert transform is used in EMD for the identification of oscillatory signals. In this paper a new EMD algorithm is proposed using FFT to identify and extract the acoustic signals available in the underwater channel that are corrupted due to various ambient noises over a range of 100 Hz to 10 kHz in a shallow water region. Data for analysis are collected at a depth of 5 m and 10 m offshore Chennai at the Bay of Bengal. The algorithm is validated for different sets of known and unknown reference signals. It is observed that the proposed EMD algorithm identifies and extracts the reference signals against various ambient noises. Significant SNR improvement is also achieved for underwater acoustic signals.展开更多
Underwater Wireless Communication, largely dependent on the acoustic communication between the machines, is largely affected by various types of noise in the shallow and deep water. However ambient noise which is due ...Underwater Wireless Communication, largely dependent on the acoustic communication between the machines, is largely affected by various types of noise in the shallow and deep water. However ambient noise which is due to multiple sources (e.g. shipping, wind) and no one source dominates. Ambient noise masks the acoustic signal to a large extent. Hence today it has drawn the attention of the experts to reduce its effect on the received signal. This paper discusses ambient noise problem and devises a new wavelet thresholding method to reduce its effect. Afterwards a comparative study on statistical parameters is shown to prove the efficiency of the devised method.展开更多
针对典型数字信号控制器(Digital Signal Controller,DSC)的电磁兼容问题,提出了电磁特性与温度特性相结合的分析方法,研究了环境温度对其传导电磁敏感度的影响.结合电磁敏感度行为级模型结构,分析了电磁干扰的作用机制,导出了DSC中金属...针对典型数字信号控制器(Digital Signal Controller,DSC)的电磁兼容问题,提出了电磁特性与温度特性相结合的分析方法,研究了环境温度对其传导电磁敏感度的影响.结合电磁敏感度行为级模型结构,分析了电磁干扰的作用机制,导出了DSC中金属-氧化物-半导体(Metal-Oxide-Semiconductor,MOS)器件阈值电压和迁移率随环境温度的变化关系;利用直接功率注入与环境温度联合控制技术,从实验和仿真两个方面分析了模型各部分特征参数在不同温度下的变化,揭示了电磁敏感度在不同环境温度下变化的内在因素,并测试了不同温度下典型DSC的电磁敏感度阈值.结果表明,DSC敏感度行为单元中MOS器件阈值电压和迁移率在不同温度下的变化,会造成其电磁敏感度随环境温度产生显著漂移.展开更多
文摘Sonar generated acoustic signals transmitted in underwater channel for distant communications are affected by numerous factors like ambient noise, making them nonlinear and non-stationary in nature. In recent years, the application of Empirical Mode Decomposition(EMD) technique to analyze nonlinear and non-stationary signals has gained much attention. It is an empirical approach to decompose a signal into a set of oscillatory modes known as intrinsic mode functions(IMFs). In general, Hilbert transform is used in EMD for the identification of oscillatory signals. In this paper a new EMD algorithm is proposed using FFT to identify and extract the acoustic signals available in the underwater channel that are corrupted due to various ambient noises over a range of 100 Hz to 10 kHz in a shallow water region. Data for analysis are collected at a depth of 5 m and 10 m offshore Chennai at the Bay of Bengal. The algorithm is validated for different sets of known and unknown reference signals. It is observed that the proposed EMD algorithm identifies and extracts the reference signals against various ambient noises. Significant SNR improvement is also achieved for underwater acoustic signals.
文摘Underwater Wireless Communication, largely dependent on the acoustic communication between the machines, is largely affected by various types of noise in the shallow and deep water. However ambient noise which is due to multiple sources (e.g. shipping, wind) and no one source dominates. Ambient noise masks the acoustic signal to a large extent. Hence today it has drawn the attention of the experts to reduce its effect on the received signal. This paper discusses ambient noise problem and devises a new wavelet thresholding method to reduce its effect. Afterwards a comparative study on statistical parameters is shown to prove the efficiency of the devised method.
文摘传统基于离线模型参数和典型运行方式设计的电力系统阻尼控制器存在适应性问题,提出一种基于辨识的自适应控制器设计方法,可解决一般自适应控制中快速性和准确性要求之间的矛盾。所用的多元自回归滑动平均模型(auto regressive moving averaging vector,ARMAV)辨识在电网正常运行过程中针对由负荷等随机扰动引起的类噪声信号进行;在综合考虑辨识误差、阻尼要求和稳定裕度基础上,提出阻尼控制零极点配置基本原则,并设计相应的遗传算法优化方法。为了充分检验上述辨识与控制系统的效果,基于广域测量平台对其进行软硬件实现,并在东北电网简化系统中进行实时数字仿真(real time digital simulation,RTDS)测试,实验结果说明了所提方法的可行性和有效性。
文摘针对典型数字信号控制器(Digital Signal Controller,DSC)的电磁兼容问题,提出了电磁特性与温度特性相结合的分析方法,研究了环境温度对其传导电磁敏感度的影响.结合电磁敏感度行为级模型结构,分析了电磁干扰的作用机制,导出了DSC中金属-氧化物-半导体(Metal-Oxide-Semiconductor,MOS)器件阈值电压和迁移率随环境温度的变化关系;利用直接功率注入与环境温度联合控制技术,从实验和仿真两个方面分析了模型各部分特征参数在不同温度下的变化,揭示了电磁敏感度在不同环境温度下变化的内在因素,并测试了不同温度下典型DSC的电磁敏感度阈值.结果表明,DSC敏感度行为单元中MOS器件阈值电压和迁移率在不同温度下的变化,会造成其电磁敏感度随环境温度产生显著漂移.
