二阶偏振模色散补偿方案研究

该文首先从理论上导出了保偏光纤的偏振模色散矢量表达式,此表达式是由保偏光纤参数决定的。应用此矢量表达式推导出能够同时补偿一阶和二阶偏振模色散的矢量表达式,进一步提出使用三段保偏光纤的二阶偏振模色散补偿方案,通过调整第一段保偏光纤的长度和三段保偏光纤之间的耦合角度,即可实现二阶偏振模色散的补偿。最后数值模拟了该补偿方案的控制算法,这些结果表明该方案控制算法简单,能有效地对二阶偏振模色散进行补偿,降低了误码率,提高了通信系统性能。     

光纤通信系统中偏振模色散补偿方法的探讨

偏振模色散(PMD)已成为高速光纤通信系统发展的严重障碍。文章对目前几种偏振模色散的补偿方法进行了分析和比较,指出用保偏光纤(PMF)和偏振控制器(PC)来补偿PMD是目前比较可行的方法,用液晶进行PMD补偿的方法在进一步研究之中。     

光纤通信偏振膜色散误差消除研究与仿真

研究光纤通信准确接收优化问题。由于基本的光纤材料中,密度分布不均匀,造成偏振主态与差分群时延耦合性较差。传统光纤通信算法进行远程通信时,偏振膜密度的不均匀分布会发生色散,造成色散误差,降低了信号接收频谱的准确率。提出了一种偏振膜色散误差消除方法,提取矢量偏振态参数,利用光纤信号传递矩阵计算偏振膜色散误差,对偏振主态进行傅里叶变换,消除偏振膜色散对信号接收频谱的影响。实验证明,利用光纤通信偏振膜色散误差消除算法,能够提高光纤通信信号接收频谱的准确率,为提高通信的准确性提供了参考。     

啁啾布拉格光栅的可调谐色散补偿特性

本文讨论了啁啾布拉格光栅(CFBG)群时延波(GDR)的产生机理以及降低GDR的方法。采用迭代矫正GDR的方法能有效改进啁啾光栅的GDR,计算表明啁啾布拉格光栅有实现可调谐色散的可能,为高速WDM和OTDM系统提供了工程设计参数。     

基于传输补偿算法的光纤通信设计研究与仿真

研究光纤通信问题,提高通信的效率。针对光信号在传输过程中,不同的频率成分或模式成分因传播速度不同而相互散开,使传输的信号脉冲发生畸变,从而限制了光纤的传输效率,很难保证信息传播的高效性的问题。提出基于激光通信设备的光纤通信优化方案。通过激光能量补偿和偏振模色散补偿算法,校正了光纤通信过程中由于能量损耗和偏振模色散导致的通讯误差,从而能够快速、准确的使用激光通信设备在光纤通信中高效传输数据。实验证明,该算法能够补偿光纤通信中,色散导致的传递误差,取得了较好的效果,为光纤通信优化设计提供了依据。     

MEMS加速度计二阶非线性补偿方法研究

微惯性集成测量组合(MIMU)中的惯性传感器,陀螺仪和加速度计的标定补偿研究大多集中在安装误差角补偿和一阶线性常数的计算上,对二阶非线性系数的测量、计算研究的不多不深.通过分析含二次非线性系数的加速度计输出模型,提出一种补偿二次非线性系数的方法,并进行了完善的理论分析和试验.最终通过计算能有效补偿MIMU的输出精度,为后续的导航信息解算奠定了基础,具有重要的工程应用价值.     

二阶差分的自适应RED算法研究

在现有的AQM算法的基础上,使用经典控制理论中的时域分析方法对ARED算法的内部结构进行分析研究,根据分析的结果设计了新的基于二阶差分的离散控制器,并将其应用到AQM算法中。在NS-2仿真平台上进行 了大量的仿真,结果表明:基于二阶差分的ARED算法使得队列长度变得更加稳定,对队列具有更好的控制能力。     

偏振激光散斑的偏振态测量研究

偏振激光散斑偏振态的问题已进行过深入的研究,但在大多数研究中,没有考虑具有影响透射光的偏振和传播方向的各向异性折射率材料。为了对各向异性介质产生的偏振激光散斑展开研究,采用马赫-曾德尔干涉仪的方法,搭建偏振干涉实验光路,用MATLAB对双折射散射板产生的偏振激光散斑进行处理并分析。实验结果表明,各向异性折射率材料会影响透射光的偏振和传播方向,与普通磨砂玻璃相比,双折射散射板产生的偏振激光散斑图包含了更多的偏振信息,即椭圆偏振态、线偏振态和圆偏振态,而不是单一的一种偏振态。这对具有随机偏振态的表面散射现象的研究奠定了基础。     

高速光纤通信系统中信号损伤缓解与补偿技术探讨

目前造成高速光纤通信系统传输信号损失的主要原因是偏振模色散,笔者在本文的研究中主要从该角度出发,首先介绍了导致信号损伤的偏振模色散的相关概念,以及如何对其进行测量,最后就其补偿技术提出了一些对策建议。对于改善高速光纤通信系统中信号损伤的现象有着重要作用。     

一种新结构的偏振开关

一种新型的偏振开关被提出,它用电控的法拉第旋光片产生离散的偏振态。它可以改进偏振相关损耗的测量。使用这种偏振开关测出的数据与理论计算得出的结果吻合的很好.     

Study of spectrum sensing exploiting polarization: From optimal LRT to practical detectors

Spectrum sensing exploiting polarization can be leveraged to improve detection performance. In this paper, we present an optimal likelihood ratio test (LRT) which serves as the upper bound on the performance of all methods that exploit polarization under Gaussian assumption. However, the performance of LRT for realistic blind sensing is unclear since the practical implementation of polarization sensing has to face several challenges, which is the focus of this paper. Four practical sensing algorithms utilizing polarization are considered in this work, that is, a generalized likelihood ratio test (GLRT) for polarization sensing using maximum likelihood estimate (MLE) method when any prior knowledge is unknown, an optimal test when the noise of channel between primary user and secondary user is partially polarized, a realistic detector considering that the received polarization wave arrived with a specific direction rather than is almost perpendicular to the receiver dual-polarized antennas, and a more practical blind detector for polarization channel exhibiting polarization mode dispersion (PMD) phenomenon especially in wideband system. The simulation results show the performance gains possible with proposed detectors and how well the proposed detectors are expected to perform in practice.     

偏振分集天气雷达研究新进展

偏振分集天气雷达能提高降雨测量精度,获取云雨区水成物粒子形状、大小、相态以及空间取向等信息,是近年来国际雷达气象界发展起来的重要探测手段。根据国内外最新资料,对偏振分集天气雷达的原理、技术作了概要介绍,为实际应用提供了一定依据。     

自适应滑模摩擦补偿在隔膜张力控制中的应用

为稳定放卷张力,提出了自适应滑模摩擦补偿控制算法,对放卷机构中的负载惯量与摩擦进行在线辨识。以放卷电机的转速和角位移误差为变量设计了线性滑模面;以惯量及摩擦估计误差变量及滑模面的偏移变量为基础设计了Lyapunov函数;以该函数的梯度下降为原则设计了在线辨识的自适应律。当系统在自适应滑模控制器的作用下稳定在滑模面上时,负载惯量及摩擦便趋近于其实际值。通过该摩擦补偿方法实现了张力控制目标。对所提方法进行单轴仿真及试验验证,表明该算法能有效提高张力的控制精度。     

基于观测器的滑模控制非线性中立型时滞系统

针对一类状态不可测的非线性不确定中立型时滞系统,基于滑模控制理论,采用线性矩阵不等式的处理方法,提出了滑动模态鲁棒渐近稳定时滞相关的充分条件,设计了一类滑模观测器,同时给出了该观测器存在的充分条件;然后应用滑模控制的趋近率方法和基于观测器所得到的系统估计状态,综合了一类滑模控制器,该控制器同时保证了估计状态下滑模面和估计误差状态下滑模面的渐近可达性;最后通过数值实例证明了该控制方案的可行性.     

Adaptive Observer‐Based Global Sliding Mode Control for Uncertain Discrete‐Time Nonlinear Systems with Time‐Delays and Input Nonlinearity

A new discrete‐time adaptive global sliding mode control (SMC) scheme combined with a state observer is proposed for the robust stabilization of uncertain nonlinear systems with mismatched time delays and input nonlinearity. A state observer is developed to estimate the unmeasured system states. By using Lyapunov stability theorem and linear matrix inequality (LMI), the condition for the existence of quasi‐sliding mode is derived and the stability of the overall closed‐loop system is guaranteed. Finally, simulation results are presented to demonstrate the validity of the proposed scheme.     

Position Control of a Series Elastic Actuator Based on Global Sliding Mode Controller Design

A series elastic actuator (SEA) is a powerful device in the area of human-machine integration, but it still suffers from difficult position control issues. Therefore, in this paper, an efficient approach is proposed to solve this problem. The approach design is divided into two steps: feedback linearization (FL) and global sliding mode (GSM) controller design. The bounded analysis is presented and global asymptotic convergence is analytically proven. Simulation and experiment results illustrate the effectiveness of the proposed scheme.      

Analytical modeling of H‐shape distributed topology with bandpass negative group delay behavior

This article describes an analytical modeling of a distributed negative group delay (NGD) circuit presenting a H‐shape topology. It acts as an innovative typical transmission line (TL) based topology with a feedback connected with an open‐stub termination. The equivalent circuit diagram is established based on TL representation of H‐topology constituting elements. The S‐matrix analytical model is developed. To validate the analytical model, a proof‐of‐concept prototype implemented in microstrip topology is designed, simulated, fabricated, and measured. The compared calculated, simulated, and measured S‐parameters are in very good agreement. In addition, the microstrip prototype confirm the bandpass NGD behavior of the H‐topology circuit with NGD value of approximately ?2 ns around the center frequency 1.67 GHz.     

A New Adaptive Sliding Mode Control of Uncertain Nonlinear Systems

In this paper, a new adaptive sliding mode control is proposed to control nonlinear systems with parametric uncertainties and matched and unmatched external disturbances. The proposed method first combines immersion and invariance (I&I) adaptive scheme with sliding mode control (SMC), which preserves the advantages of the two methods. The proposed method is different from the approach of combining the backstepping adaptive scheme and sliding mode control in the parameter estimation law, which allows for prescribed dynamics to be assigned to the estimation error and is easier to tune. Finally, the method is applied to control a class of power systems, and simulation results show the advantages of the proposed method.     

Synthesis of a New Robust Exponential Sliding Mode Differentiator with its Observer Applications

This paper proposes a new robust exponential sliding mode differentiator for estimating the (n ? 1) derivatives of a non‐linear function. Finite time convergence, robustness, and exactness are also ensured analytically with the proposed methodology. In addition, the results of the proposed sliding mode differentiator are extended to derive theorems for the novel state (SO) and extended state observers (ESO), which would estimate the system states as well as uncertainties recursively in finite time. Finally, three examples are implemented to validate the proposed methodologies and the obtained simulations are compared with the previously developed methods in literature.