CDMA系统中LMMSE均衡器的时延参数对其性能的影响

介绍了码分多址CDMA系统中码片级线性最小均方误差均衡器 .针对时延参数的优化选取对线性最小均方误差均衡器性能的影响进行仿真分析 ,并同传统rake接收机的性能相比较 .结果表明 :在均衡器长度与信道最大多径时延相接近时 ,时延参数优化后的线性最小均方误差均衡器与同时延参数未经优化时相比性能有较大改善 ,而随着均衡器长度的增加 。

IP网络时延变化参数的分析

为了对IP网络的时延变化参数(IPDV)进行界定,给出了一个端到端IP网络的假设参考路径(HRP),在HRP上对影响IPDV参数的一些因素进行分析,并计算出IPDV参数值。

基于改进稀疏贝叶斯学习的时域信道参数估计方法

针对稀疏贝叶斯学习的信道估计方法在估计信道时延-多普勒二维参数时字典规模过大的问题,文章提出了一种改进的稀疏贝叶斯学习信道估计方法。首先采用匹配滤波器得到接收信号的模糊度函数;然后设置阈值并筛选大于阈值的信道响应,保留对应的索引和原子;接着利用保留的原子构建新的字典矩阵,同时构建相同规模的超参数矩阵;最后将保留的原子逐个代入稀疏贝叶斯学习算法进行超参数的迭代和收敛,最终得到信道冲激响应。该方法在不需要提前获知信道稀疏度的前提下,提高了信道参数估计的分辨率,相比传统的稀疏贝叶斯学习算法,大幅减小了计算量,使得采用稀疏贝叶斯学习算法估计二维时延-多普勒参数成为了可能。仿真结果表明,在预处理阈值设置合理的情况下,该方法相比原始稀疏贝叶斯学习算法,信道估计均方误差至少降低了约一个数量级,相比传统算法一次运算的时间大大缩短。

基于周期平稳的OFDM上行系统同步参数盲估计方法

针对脉冲成型OFDM上行系统,本文提出了一种多用户同步参数的盲估计方法。该方法利用信号的二阶周期平稳特性和共轭周期平稳特性,对信道的频偏和时延参数进行了估计,具有较高的精度和较好的抗噪特性。最后给出了性能仿真,并与已有的其他方法进行了对比。

基于时延优化的三维成像声呐视野展宽方法研究

针对平面阵,研究并探讨了一种近场聚焦波束形成中时延参数的优化方法,以扩大三维成像声呐的有效视野范围。该方法是在方位角和俯仰角重新定义时,将精确的近场时延表达式按泰勒公式展开,取前三项,并对每一项进行加权。然后,通过求三个加权系数的偏导,再令其等于0,得出最优加权系数,此时优化的时延表达式与精确的近场时延表达式的误差最小,即优化的时延表达式更接近于精确的时延表达式,能够有效地用于扩大成像声呐的有效视野。最后,通过计算机仿真验证了该方法的有效性。

基于触头燃弧损耗的动车组交流接触器剩余电寿命预测

动车组交流接触器的性能状态与列车运行安全密切相关。针对动车组交流接触器在三相不均匀燃弧损耗工况下,特征参数变化趋势与电寿命趋势的复杂映射关系问题,提出一种基于触头燃弧损耗的电寿命预测方法。首先,基于触点的燃弧机理,分析了导致三相触头之间燃弧损耗差异的原因,并在此基础上进行了随机燃弧损耗和定相燃弧损耗2种模式下的电寿命试验。然后,提取电寿命试验过程中的接触器特征参数,利用Spearman等级相关系数方法计算各特征参数与累积燃弧损耗之间的相关性,以此筛选出相关性强的特征参数构成状态识别的特征参数组。接着通过多元线性回归的方法对特征参数组进行融合,得到表征燃弧损耗状态的指标,对比指标曲线与实际寿命曲线发现试验样本存在初始燃弧损耗量的问题。之后建立基于相似性的接触器剩余燃弧损耗量预测模型,在评估环节引入能将初始燃弧损耗量的不确定性问题转化为时延问题的时延参数,通过交叉验证的方法选定最优时延参数,并建立综合评价指标对模型进行评估。最后,利用试验样本对预测模型进行了验证,并以定相燃弧损耗样本为例通过接触器电寿命映射模型对剩余电寿命进行了计算。结果表明,所提出的方法能够成功地定量评价接触器在三相不均匀燃弧损耗情况下的剩余电寿命,且能够直观表现剩余寿命的变化过程,预测误差仅为0.9%~12.1%。

一种高速变采样系统输入延时自适应校准方法

针对高速采样系统不同采样频率下会产生不同的数据输入延时,提出了一种高速变采样系统输入延时自适应校准方法,该方法以现场可编程门阵列(FPGA)、高速模数转换器(ADC)和时钟芯片为平台设计核心,采用了高速ADC、时钟芯片与FPGA串行外围接口设计、采样频率动态设计、两级降速架构设计、主从时延校准算法等,实现了采样频率动态控制、并行采样支路数量可调和高速采样数据输入延时的动态校准,完成了高速ADC复杂调制信号无误采样的技术工程实践。

电阻耦合单电子晶体管电学性能分析

基于单电子系统半经典模型 ,分析了电阻耦合单电子晶体管的电学特性 ,得到其电学性能不随背景电荷分布变化的特点 .通过时域特性分析 ,指出了时延参数τ=CΣ Rg,并用 Monte-

SUBSAMPLE TIME DELAY ESTIMATION BASED ON PHASE SPECTRUM OF BAND LIMITED STOCHASTIC SIGNALS

The accuracy of conventional time delay estimation （TDE） algorithms is limited by the sampling interval. A novel algorithm of subsample TDE suitable for widehand signals is presented to improve the accuracy. This algorithm applies periodogram and parabolic interpolation to the cross correlation spectrum of band limited stochastic signals, and can obtain a continuous time delay estimator. Simulations are carried out to compare the performance of the proposed algorithm with that of other subsample TDE algorithms. Results show that the proposed algorithm outperforms other algorithms and reachs the Cramer-Rao lower bound （CRLB） at a high signal- to-noise ratio. For the wideband characteristic and the randomness of the transmitting signal, the proposed algo- rithm is suitable for the low probability of intercept radars.

基于时间因子的网络安全态势评估系统设计

受噪声因素的影响,传统方法对网络安全攻击识别与评估的灵敏度较低,对应的安全态势评估结果与实际情况存在一定差异。为此,本文设计了一种基于时间因子的网络安全态势评估系统。利用高性能的MYC-CZU5EV核心板作为系统的硬件装置,在软件设计阶段,引入时间因子分析时延参数的波动程度,以此确定网络安全态势的评估模式。当分析结果为噪声扰动模式时,直接利用时延波动幅度计算对应的安全态势值;当分析结果为网络攻击模式时,通过叠加当前网络状态与攻击作用计算得到对应的安全态势值。测试结果表明,所设计系统对安全态势评估结果与实际值具有较高的拟合度。

应急广播调频同步网设计与建设

本文介绍四川广播电视台利用调频同步技术建设全省应急广播无线覆盖网的思路和技术要点,同时对调频同步技术涉及的关键技术进行分析探讨,提出时延模型的建立与计算,以及系统调试测验方法等。

Stochastic Analysis of Interconnect Delay in the Presence of Process Variations

Process variations can reduce the accuracy in estimation of interconnect performance. This work presents a process variation based stochastic model and proposes an effective analytical method to estimate interconnect delay. The technique decouples the stochastic interconnect segments by an improved decoupling method. Combined with a polynomial chaos expression （PCE）, this paper applies the stochastic Galerkin method （SGM） to analyze the system response. A finite representation of interconnect delay is then obtained with the complex approximation method and the bisection method. Results from the analysis match well with those from SPICE. Moreover, the method shows good computational efficiency, as the running time is much less than the SPICE simulation＇s.

IMC-PID tuning method based on sensitivity specification for process with time-delay

To overcome the deficiencies addressed in the conventional PID control and improve the dynamic performance and robustness of the system, a simple design and parameters tuning approach of internal model control-PID （IMC-PID） controller was proposed for the first order plus time-delay （FOPTD） process and the second order plus time-delay （SOPTD） process. By approximating the time-delay term of the process model with the first-order Taylor series, the expressions for IMC-PID controller parameters were derived, and they had only one adjustable parameter 2 which was directly related to the dynamic performance and robustness of the system. Moreover, an analytical approach of selecting 2 was given based on the maximum sensitivity Ms. Then, the robust tuning of the system could be achieved according to the value of Ms. In addition, the proposed method could be extended to the integrator plus time-delay （IPTD） process and the first order delay integrating （FODI） process. Simulation studies were carried out on various processes with time-delay, and the results show that the proposed method could provide a better dynamic performance of both the set-point tracking and disturbance rejection and robustness against parameters perturbation.

Guaranteed cost sampled-data control for uncertain nonlinear time-varying delay system

The robust guaranteed cost sampled-data control was studied for a class of uncertain nonlinear systems with time-varying delay. The parameter uncertainties are time-varying norm-bounded and appear in both the state and the input control matrices. By applying an input delay approach, the system was transformed into a continuous time-delay system. Attention was focused on the design of a robust guaranteed cost sampled-data control law which guarantees that the closed-loop system is asymptotically stable and the quadratic performance index is less than a certain bound for all admissible uncertainties. By applying Lyapunov stability theory, the theorems were derived to provide sufficient conditions for the existence of robust guaranteed cost sampled-data control law in the form of linear matrix inequalities (LMIs), especially an optimal state-feedback guaranteed cost sampled-data control law which ensures the minimization of the guaranteed cost was given. The effectiveness of the proposed method was illustrated by a simulation example with the asymptotically stable curves of system state under the initial condition of x(0)=[0.679 6 0].

Stabilization of a class of nonlinear discrete time systems with time varying delay

The stability and stabilization of a class of nonlinear discrete time delayed systems(NDTDS) with time-varying delay and norm-bounded nonlinearity are investigated. Based on discrete time Lyapunov–Krasovskii functional method, a sufficient delaydependent condition for asymptotic stability of nonlinear systems is offered. Then, this condition is used to design a new efficient delayed state feedback controller(DSFC) for stabilization of such systems. These conditions are in the linear matrix inequality(LMI) framework. Illustrative examples confirm the improvement of the proposed approach over the similar cases. Furthermore, the obtained stability and stabilization conditions will be extended to uncertain discrete time delayed systems(UDTDS) with polytopic parameter uncertainties and also with norm-bounded parameter uncertainties.

On Stabilizing Sets of PI Controllers for Multiple Time Delayed Process

This paper considers the problem of stabilizing multiple time delayed processes using proportional integral(PI) controller.The presented approach is based on finding all possible values of control parameters which will result in pure imaginary roots of closed loop characteristic equation under all process parameters fixed.The ergodic search of three PI control parameters are converted from the range of infinity to finite range by introducing trigonometric tangent function.After all possible stability boundaries are obtained,the Nyquist stability method is used to determine the actual stability region of the controller parameters.This method also permits design for simultaneous minimum gain and phase margin requirement.An illustrative example case is also presented.

An accurate calculation method of the power harmonic parameters based on the delay time theorem of Fourier transform

A new accurate calculation method of electric power harmonic parameters was presented. Based on the delay time theorem of Fourier transform, the frequency of the electric power was calculated, and then, suing interpolation in the frequency domain of the windows, the parameters （amplitude and phase） of each harmonic frequency signals were calculated accurately. In the paper, the effect of the delay time and the windows on the electric power harmonic calculation accuracy was analysed. The digital simulation and the physical measurement tests show that the proposed method is effective and has more advantages than other methods which are based on multipoint interpolation especially in calculation time cost; therefore, it is very suitable to be used in the single chip DSP micro-processor.