一种双向测距与时间同步系统的设计与分析

在研究双向单程伪距测量原理的基础上,设计了双向测距与时间同步（DRTS）终端系统总体构架,阐述了在系统中使用的技术,并搭建了基于DSP＋FPGA的双向测距与时间同步系统软硬件平台。实验结果表明,此系统的码速率为5MHz、中心频率为15MI-Iz时,测距和时间同步的分辨率可达0．15cm和5ps（@1S）,采用不同频率源时测距和时间同步的精度分别为1．038m和3．46ns,采用相同频率源时分别为0．28cm和9．43ps（参考频率稳定度1×10^-10／d量级）。与国外同类产品相比具有测量精度优势,但考虑通用性,此系统的硬件仍需进一步优化,软件上需要做到码速率可调。     

共视法和综合法的GPS时间同步精度比较

对共视法和综合法的GPS时间比对对得到的两地协调世界的时间同步精度进行了比较,两种方法各有特点,都有实用价值,严格共视的GPS时间同步精度为5－10ns,不严格共视的GPS的时间同步精度为10－20ns,综合的GPS时间同步精度为6－12ns.     

无线传感器网络中基于时钟漂移补偿的时间同步技术

在分析和总结现有时间同步算法的特点及其存在问题的基础上,提出了一种在无线传感器网络的时间同步协议（TPSN）中同时考虑节点时钟偏移和频率漂移率的改进算法。该算法利用连续两次同步过程中所记录的时间信息来估算节点时钟的偏移和频率漂移率,并进行补偿。同传统算法相比,此算法通讯成本较低、精度较高。最后通过数学分析和仿真的方法对所提出的改进算法进行了验证。     

无线传感器网络时间同步实验平台的研究

介绍了用GAINS(global actable intelligent networks)节点搭建无线传感器网络(wireless sensor network,缩写为WSN)时间同步实验平台的过程,并实现了WSN时间同步协议TPSN(timing-sync protocol for sensor networks),详细阐述了组成平台的软硬件.在此基础上,可以进一步研究和开发更复杂的时间同步协议,在实际传感器网络中实现具体应用.     

一种高性能数字移相系统

阐述了一种用于时间同步系统的高性能数字移相系统的设计方案和实现过程,该系统采用直接数字合成（DDS）技术,其同步精度小于100 ns,移相精度可达5×10-10 s,同时能够实现精度为10-6 Hz的频率调节。该系统是为时间同步系统设计,并可广泛应用到军用、电力、通信等领域中。     

双向测距与时间同步系统中设备时延标定的研究

双向测距与时间同步系统采用的是双向单程伪距测量机制。因此设备时延包含在伪码测距的测距值与钟差值之中,这对系统的测距精度产生了不良的影响。针对这种设备时延,提出了双向测距与时间同步终端闭环校准方法。实验及分析表明该方法是有效的,并为系统的下一步设计提供了有效的参考。     

B码设备中的GPS时间信号接口

ＰＯ９７型ＧＰＳ／Ｂ码解调器把ＧＰＳ技术融入Ｂ码设备中,用于自动定时定位和精密时间同步。该设备的ＧＰＳ时码接口解出ＧＰＳ时间信号,并同步所有的时标信号和时间码信号。主要介绍了该接口的硬件和软件的实现过程。     

电视时间同步的可用性

本文综述了利用电视信号作时间、频率同步的各种技术和可能达到的精度，以及存在的一些问题和改进意见．     

一种高精度时间同步器的研制与性能测试

针对移动通信网络基站间需要建立高精度时间同步的需求,研制了一种具有高精度时间同步功能和高精度频率输出的时间同步器,并设计了相应的性能测试方法。测试结果表明,在同等条件下,不同时间同步器输出的1PPS平均同步精度优于5ns／d,24h内输出的频率准确度优于10^-12／s,其他各项指标基本合格,符合设计要求。     

时间同步对低频导航精度的影响(摘要)

从低频导航系统的工作原理分析,主副台的同步精度直接影响着导航精度。传统采用的主副台主从同步工作方式不可避免地要引入主副台间电波传播时延起伏导致的副台同步误差,进而会对导航精度产生影响。后来采用的被称为“自由同步”的主副台同步方式,副台发射时延作为一个常数由固定监测站通过对台对的时间差测量实施监测控制。这在原理上摆脱了副台测收跟综主台的电波传播不稳定因素的影响,但又较大程度地依赖台对至监     

UWB中Viterbi译码器的FPGA设计与实现

由于差错控制在超宽带室内导航系统中占据着十分重要的位置,并考虑到IEEE802．15．3a标准采用卷积编码和Viterbi译码来进行差错控制,因此利用现场可编程门阵列（FPGA）设计实现了一种约束长度为7,译码深度为64的全并行Viterbi译码器。本设计在xilinx ISE9．2环境下进行了综合,并采用Modelsim6．0对整个设计进行了仿真。仿真结果表明,该设计能够满足超宽带系统的要求。     

基于FPGA的IRIG-B（DC）码的解码方案的设计与实现

IRIG-B码是国际上通用的时间码格式,广泛应用于各种系统的时间同步。针对IRIG-B（DC）码的调制特性,介绍一种基于FPGA的B码解调方案。重点描述了如何在同步时序中准确提取秒同步信号并解调B码中包含的时间信息。整个方案中采用Verilog HDL语言进行设计,已成功实现,并给出了验证结果。     

建立同步卫星精密星历表的最佳数值方法

简要介绍当前天体力学中常用的各种数值计算方法,结合同步卫星运动方程的特点和轨道解的性质,分析各种数值计算方法在同步卫星情况下使用的优劣,确定一次和分形式的Cowell方法是建立同步卫星精密星历表的最佳方法,最后通过有效的数值实验,给出不同精度要求下Cowell方法的最佳阶和相应的最大步长.     

High time resolution observations of solar radio emission at four frequencies: evidence for energy release in microflares

As evidence for energy release in microflares, high time resolution observations of solar radio emission obtained with our “synchronous observation system of solar radio radiation with high time resolution at four frequencies (1.42, 2.13, 2.84 and 4.26 GHz)” from December 1989 to April 1993 are presented in this paper. The observed events include weak ms spikes, “spike-likes”, fast pulsations as well as two kinds of newly discovered fast fine structures, i.e., microwave type III bursts and microwave patch-like structures. A statistical study of the duration of fast fine structures has been made and on its basis the various types of phenomena are illustrated with actual examples.     

The global structure of the pulsar magnetospheres

The model of the pulsar magnetosphere filled with massless charged particles (rest massm=0) is considered. The gas of charged massless particles can be found in two different phases: (1) dynamical phase (DP), when the particles move with nonvanishing energy along some base line, determined by the electromagnetic field only, (2) statical phase (SP), when the particles have vanishing energy =0. The pulsar magnetosphere occurs to be divided into regions of different types: (a) the accelerating regions (DP-regions) containing only DP, (b) the capture regions, containing only SP, (3) leaky capture regions, where DP moves through SP. The leaky capture regions are the active regions, which are responsible for the pulsar radioemission. In the case of oblique magnetic moment the equation for the capture surface has been obtained. The capture region is formed around this surface. Expressions for jumps of the electromagnetic field, the current density and the charge density on the capture region boundary have been obtained. The problem of the pulsar magnetosphere is stated mathematically in the case of oblique magnetic moment and ejection of only electrons.     

同步卫星短弧定轨

同步卫星受到摄动力的影响,它的实际轨道有一点漂移．卫星需要不断的调轨调姿,以保证其正常运行．为了研究卫星在几小时,甚至更短的时间内的轨迹情况,采用短弧段定轨法．用动力学方法进行短弧定轨,分别研究1小时和15分钟定轨并进行比较,目的是为了在同步轨道卫星变轨后,能尽快地为卫星提供精密的预报轨道．此外,在系列短弧定轨后,得到精密轨道系列,为研究轨道变化的力学因素及研究短弧中卫星转发器时延变化规律等提供依据．     

Orbit and spin evolution of synchronous binary stars on the main sequence(a theoretical improvement to the analytical method)

This paper provides a method to study the solution of equations for synchronous binary stars with large eccentricity on the main sequence.The theoretical results show that the evolution of the eccentricity is linear with time or follows an exponential form,and the semi-major axis and spin vary with time in an exponential form that are different from the results given in a previous paper.The improved method is applicable in both cases of large eccentricity and small eccentricity.In addition,the number of terms in the expansion of a series with small eccentricity is very long due to the series converging slowly.The advantage of this method is that it is applicable to cases with large eccentricity due to the series converging quickly.This paper chooses the synchronous binary star V1143 Cyg that is on the main sequence and has a large eccentricity(e = 0.54) as an example calculation and gives the numerical results.Lastly,the evolutionary tendency including the evolution of orbit and spin,the time for the speed up of spin,the circularization time,the orbital collapse time and the life time are given in the discussion and conclusion.The results shown in this paper are an improvement on those from the previous paper.     

The evolution of massive close binaries

The influence of tidal, interaction on the periods of massive X-ray binaries during the postsupernova evolution is investigated. It is assumed that after a certain time the orbit has become circular and synchronous. The tidal effects of subsequent evolutionary changes in the moment of inertia of the massive component are calculated. It is shown that, as is already suggested by Sparks and Stecher (1974), for small mass ratios and short binary periods a tidal instability may occur resulting in an accelerating inward spiral motion. Before the onset of the instability the tidal forces maintain a nearly synchronous orbit. Possibly the orbits of Cen X-3 and 3 U 1700-37 are already unstable at present.     

Simultaneous ground-satellite observations of Pi 2 magnetic pulsations and their high frequency enhancement

Pi 2 magnetic pulsations are a frequent occurrence at the earth's surface and have been shown to be clearly correlated with substorm expansion onset. These pulsations are also observed in space at synchronous orbit at the same time as they are seen on the ground at the satellite conjugate point. In this brief report we describe three days in 1969 on which Pi 2 magnetic pulsations were simultaneously observed at the synchronous satellite ATS 1 and at Tungsten, N.W.T., Canada, near the foot of the ATS 1 magnetic field line. These Pi 2 bursts all exhibit the characteristic waveform and frequency, as well as an ～0.3 Hz enhancement, at both locations. This high frequency enhancement appears to be an integral part of Pi 2 bursts both on the surface and at synchronous orbit and should be considered in the development of models of generation mechanisms.     

Dark energy model with variable q and ω in LRS Bianchi-II space-time

The present study deals with spatial homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi-II dark energy model in general relativity. The Einstein’s field equations have been solved exactly by taking into account the proportionality relation between one of the components of shear scalar $(\sigma^{1}_{1})$ and expansion scalar (?), which, for some suitable choices of problem parameters, yields time dependent equation of state (EoS) and deceleration parameter (DP), representing a model which generates a transition of universe from early decelerating phase to present accelerating phase. The physical and geometrical behavior of universe have been discussed in detail.