海事BGAN系统数据链路测试及性能分析

概述了海事第4代卫星及BGAN系统的基本情况,针对某特殊用户对BGAN系统提出的要求,在数据Standard IP型和信道Streaming IP型2种通信业务模式下,对通信网络链路的时延、抖动、丢帧等性能进行测试实验,分析测试结果,证实了BGAN系统在远洋船舶中使用的可行性。     

基于TDC的高精度频标驯服系统设计与实现

介绍GPS驯服晶振的原理；采用高精度时间间隔测量芯片TDC测量时间间隔；设计了一种Kalman滤波算法对测量数据进行实时滤波，并通过实验对系统进行了验证。     

飞船测控跟踪功能备份方案设计与实现

针对＂神舟＂飞船测控跟踪功能没有备份的难题,首次提出利用FM（调频）跟踪接收机跟踪接收数传信号来实现跟踪功能备份。从数传信号调制特性、FM跟踪接收机组成及载波接收解调3个方面进行了理论分析,并通过FM跟踪接收机的数传信号接收解调、静态跟踪和动态跟踪试验验证了该方案的可行性和有效性。该技术在不增加辅助设备功能的基础上,通过船载测控设备中FM跟踪接收机来实现对飞船跟踪功能的备份,显著降低对飞船目标跟踪失效的风险。     

Non-Gaussian clutter characterization applied to OTHR using a mixture of two Rayleigh probability density functions

A practical technique for characterizing non-Gaussian radar clutter is specified and demonstrated using Over The Horizon Radar (OTHR) data, as an example. The technique employs maximum likelihood to fit the probability density of the clutter amplitude returns to a mixture of two Rayleigh probability densities instead of the single Rayleigh density typically used for Gaussian clutter. This model for non-Gaussian clutter is fully specified for any set of clutter amplitudes by a log likelihood, two Rayleigh parameters, and a mixing coefficient. A 3D plot of these values yields an easily-visualized clutter characterization, as is illustrated using OTHR data. This technique is a demonstration of clutter characterization using OTHR data, but the method can be applied to characterize other types of clutter data.     

Adaptive sensitive frequency band selection for VMD to identify defective components of an axial piston pump

The underlying study investigates single valued neutrosophic entropy based adaptive sensitive frequency band selection for variational mode decomposition(VMD) for the purpose of identifying defective components in an axial pump. The proposed methodology is applied in the following steps. First, VMD is applied for decomposing vibration signals into various frequency bands, called as modes. After computing energy of each VMD, the lower(minimum) and upper(maximum) bounds from these energy readings ...     

GLONASS-based precise point positioning and performance analysis

Current precise point positioning (PPP) techniques are mainly based on GPS which has been extensively investigated. With the increase of available GLONASS satellites during its revitalization, GLONASS observations were increasingly integrated into GPS-based PPP. Now that GLONASS has reached its full constellation, there will be a wide interest in PPP systems based on only GLONASS since it provides a PPP implementation independent of GPS. An investigation of GLONASS-based PPP will also help the development of GPS and GLONASS combined PPP techniques for improved precision and reliability. This paper presents an observation model for GLONASS-based PPP in which the GLONASS hardware delay biases are addressed. In view of frequently changed frequency channel number (FCN) for GLONASS satellites, an algorithm has been developed to compute the FCN for GLONASS satellites using code and phase observations, which avoids the need to provide the GLONASS frequency channel information during data processing. The observation residuals from GLONASS-based PPP are analyzed and compared to those from GPS-based PPP. The performance of GLONASS-based PPP is assessed using data from 15 globally distributed stations.     

一个新的频率源短期稳定度的表征式—沃尔什正弦方差

通过村频率源稳定度的时域测量来进行极低频频谱分析是一种有效的方法。哈达玛方差的传递函数由于具有选频特性,被人们用来进行频率源相对频率噪声谱S_y(f)的分析。本文从最佳“频窗”传递函数出发,结合微型计算机控制的计算计数器的特点,利用沃尔什函数的性质,经理论推导,获得了一个频率源稳定度的新表征式——沃尔什正弦方差。理论分析与计算机验证结果表明,该式充分发挥了微型计算机优良的数值计算和系统控制功能,能灵活而方便地获得频率源短期稳定度的各种表征量。特别是在用于S_y(f)测试时。它基本克服了哈达玛方差传递函数的谐波及其旁瓣所带来的误差,并通过测试数据的复用,使得此时测试时间大为缩短。文中给出了沃尔什正弦方差和阿仑方差与啥达玛方差的关系,指出沃尔什正弦方差在表征频率源短期稳定度方面有其内在含义。     

直接数字合成技术的应用

介绍直接数字合成（ＤＤＳ）技术的原理和当前发展水平。运用该技术改进设计了某型号作战系统中的多普勒频率     

浅谈模拟PID电路的学习与辨识

PID电路在信号运算处理和经典控制实现等方面应用非常广泛。从模拟PID发展到数字PID和软件PID,其可控性与精度不断完善和提高。模拟PID电路由于其电路结构特点,既有PID运算处理和控制功能(时域特性),又有信号频率处理与补偿功能(频域特性),在学习与应用中应加以理解和辨识。