New effective method of eliminating cyclic phase slips during double-frequency kinematic GNSS observations

Design and research results of a new effective method of processing double-frequency kinematic GPS observations with the purpose of detection, estimation and elimination of cyclic phase slips are presented. This method is based on using time increments of observation and a special procedure of joint least-square estimation for a set of informative (coordinate increments and clock divergence) and non-informative parameters (carrier cyclic phase slips). The estimation of carrier cyclic phase slips is carried out by direct enumeration in the preliminarily determined search region. Verification of the suggested method is performed using simulation and real GPS observations. It is shown that reliable detection and elimination of cyclic phase slips during complete or partial loss of data on 20 second intervals is achieved in the considered case.     

利用高次差与自相关函数对周跳探测与处理

针对载波相位数据观测过程中,由于接收机内外的原因导致出现周跳,周跳会造成高精度定位不准确,结合高次差和自相关函数的理论,提出一种基于高次差和归一化自相关函数法判断是否出现周跳,对其算法进行介绍、分析和推导,该算法具有较为深厚的理论基础,根据高次差法的特征子序列和归一化自相关函数的相关程度进行探测周跳,通过试验研究结果表明:能有效地探测周跳,判断出周跳的位置,并进行修正,进而提高观测值可靠性和准确性,具有较好的效果。     

网络RTK参考站数据实时周跳探测与修复

由于测量条件的复杂多变,载波相位观测值中周跳的产生是不可避免的,为了实现网络RTK技术高精度动态定位,必须对参考站数据进行实时的周跳探测与修复。本文充分考虑了连续运行参考站网络的特点,基于双频观测值的无电离层线性组合,并利用三差观测值作为约束条件,提出了一种简易的参考站数据实时周跳探测与修复方法,设计了相应的数据处理流程。实验结果表明,无论长基线还是短基线、短暂失锁或者失锁几分钟的数据,该方法都能正确实现周跳的探测与修复。     

一种“北斗”卫星导航系统三频周跳探测与修复方法

针对传统伪距-相位组合中伪距噪声过大的问题引入了多普勒观测值进行辅助，同时再联合无几何相位组合构成一种新的周跳探测与修复方法。在信号方面，选择B2a代替B2I,与B1I、B3I组成了“北斗”卫星导航系统(Beidou Navigation Satellite System, BDS)中定位性能更好的“北斗”三频观测组合。在选频方面，选用无几何相位系数[-1,1,0]、多普勒辅助伪距-相位系数[1,0,-1],[1,3,-4]组合进行周跳的探测。在修复方面，使用搜索法进行周跳的修复，并根据1-范数原则确保修复值的准确性。在1 s的采样率、电离层延迟稳定情况下，所提方法不仅能探测与修复出所有加入的1周在内的周跳，而且相比传统伪距-相位方法在小周跳探测方面性能更佳。     

联合多普勒及MW周跳探测和修复方法

导航定位中针对双频码相组合法(MW)无法探测L1和L2载波同一历元发生相同周跳,以及周跳探测后不能实现频率间周跳分离的情况,提出了一种联合多普勒及MW组合法的周跳探测改进方法。利用多普勒积分可对单频点进行周跳检测和修复的特性,将传统MW组合法与多普勒积分法相结合,建立改进模型,从而计算并分离出L1和L2载波相位产生的周跳。用实测数据进行验证和分析,对比了3种不同情况下改进方法的检测效果,实验表明新算法能精确探测和分离出L1和L2载波相位中的周跳组合,可以准确探测周跳发生位置及周跳数值,并且能够探测和修复1周以上的周跳,有效提高了MW组合算法探测与修复周跳的准确性和可靠性。     

GPS载波相位的周跳检测与修复分析

本文首先分析了宽巷载波与窄巷伪距法和电离层残差法检测和修复周跳的原理,结合宽巷载波与窄巷伪距法能够检测和修复较大的周跳,但无法检测同时发生在载波L1、L2上相同数量的周跳,而电离层残差法仅能检测出小周跳的特点,提出了将宽巷载波与窄巷伪距法和电离层残差法相结合的复合检测方法。首先由宽巷载波与窄巷伪距法检测和修复周跳,然后再由电离层残差法进行周跳检测和修复。仿真结果表明该复合方法能够有效地检测和修复GPS载波相位的周跳。     

Blind channel estimation using fractional sampling

We consider the problem of blind estimation of a communication channel based on the oversampled channel output. We propose a nonparametric approach that, based on the cyclic spectrum of the output, finds the channel phase response without neither the need of phase unwrapping nor channel length information. For band-limited channels, the cyclic spectrum has limited support. For this case, we propose an approximation for the discretized phase of the cyclic spectrum that, under certain conditions, results in a simpler channel estimation method. The proposed approach is applied to simulated data and real recordings and is compared to existing methods.     

基于循环平稳分析的LFM信号盲处理结果可靠性评估

针对线性调频(LFM,Linear Frequency Modulation)信号盲处理结果的可靠性评估问题,提出了一种基于循环频率特征分析的处理算法.首先对观测信号进行调制方式识别及参数估计,并据此建立参考信号,后将观测信号与参考信号作相关运算.通过检测相关序列在零频率附近是否存在循环频率,实现对LFM信号盲处理结果的可靠性检验.文中对所提出检验算法的错误概率进行了理论推导,并以常用的离散多项式变换(DPT,Discrete Polynomial Transform)法为例进行了实证分析.仿真结果表明,相对于已有时域方法而言,本文算法无需估计信噪比,且在低信噪比条件下具有更好的统计性能.     

High-speed decoding technique for slip detection in data transmission systems using modified cyclic block codes

An efficient method is described for evaluating the error-checking syndrome for systems which are modified cyclic or shortened cyclic codes to detect slips of block synchronisation.     

Theory of phase tracking systems of arbitrary order: Statistics of cycle slips and probability distribution of the state vector

The time-dependent distribution of the number of cycle slips in positive and negative directions, and the correlation of their time spacings, are derived from a new statistical model of an(N + l)-order phase tracking system. The probability density of the phase error and the other system variables are shown to agree with known results. Relations for the steady state are obtained in a relatively simple form. Some limiting conditions are mentioned under which the model reduces to a computationally much simpler renewal model described earlier.     

Characterization and modeling of static and cyclic relaxation in nonconductive adhesives

Adhesive interconnections are considered to be attractive alternatives to lead or lead-free solder interconnects because of their lower processing temperatures and extendability to fine pitch applications. However, reliability issues, such as moisture-induced delamination and viscoelastic relaxation of the adhesive in both steady-state and cyclic loading, continue to pose a challenge to widespread implementation. To date, the static and cyclic relaxation characteristics of nonconductive adhesives (NCAs) are yet to be understood. This paper attempts to provide insights into this static and cyclic relaxation behavior through experimental characterization and modeling. The viscoelastic property of a typical NCA material was characterized, and a simulation program with integrated circuit emphasis (SPICE) modeling program was used to model the cyclic relaxation behavior. The modeling results were successfully validated with a series of experiments. This showed that cyclic relaxation of the adhesive can be successfully modeled using linear-viscoelastic property. The phenomenon of slower relaxation of the adhesive under cyclic loading than that in static loading suggests that accelerated reliability testing used in solder-joint fatigue durability investigations may not be directly applicable to the adhesive interconnections. A rework methodology applicable to adhesive interconnects using cyclic loading has also been proposed.     

强电离层影响下GPS精密单点定位的周跳实时探测与修复

 该文提出了一种应用于GPS精密单点定位的周跳实时探测与修复的方法。该方法基于双频P码,可在受到强电离层影响的情况下应用于静态定位与动态导航。为了保证周跳探测与修复的实时性与准确性,采用信号处理与数据处理相结合的方式并通过合理性检验降低误判概率。通过实际数据的处理验证了该方法在强电离层影响情况下的有效性。     

Introduction of plastic encapsulated devices in systems operating under severe temperature conditions

In this paper, we describe the evolution of the selection, qualification and implementation methods used to validate the introduction of plastic SMD's into electrical equipment submitted to extreme environmental conditions:The first introduction phase was addressing equipment operating up to 125°C. The selection process was intentionally kept to minimum with emphasis on qualification through mission profile at equipment level. The results in terms of cost, performance, reliability and field feedback experience were extremely positive.The second phase was initiated for operating conditions as high as 175 °C environmental temperature. The selection process of plastic components operating at such extreme conditions, includes a full qualification through mission profile at component level. The experiments using vehicle test boards led to numerous electrical failures originated by a unique failure mechanism: delamination.In consequence, the selection process is being reviewed: a short-test for capability will be run with emphasis on initial behavior versus delamination.Expected benefits are

reduction of overall qualification costs through elimination of complete qualification with mission profile at component level.

faster availability to designers.

     

High-precision GPS-positioning using the phase observations of differential frequency

The results of developing a complex of new efficient algorithms and software for high-precision GPS-positioning of moving and stationary objects have been described using the phase observations of differential frequency (Wide Lane observations). Experimental investigations of the algorithms for the phase ambiguity resolution of Wide Lane observations and high-precision positioning were presented using the real measuring data during the performance of aerial photography on board the aircraft and stations of the permanent network in Ukraine. Peculiarities and opportunities of implementing the proposed procedures for processing of GPS observations were discussed. It was shown experimentally that the complete resolution of phase ambiguity and the subdecimeter accuracy of positioning can be achieved under the standard conditions of observations. Typical root-mean-square errors in determining the location of dynamic objects amount to 3–5 cm in terms of plane coordinates and 3–7 cm in terms of height at base distances of up to 150 km. For static determinations the root-mean-square errors do not exceed 2–4 cm for all coordinates at base distances of up to 170 km. The developed domestic algorithmic software package is a high-precision toolset for the processing of observations and can be recommended for different practical applications.     

An analysis of the reliability and design optimization of aluminium ribbon bonds in power electronics modules using computer simulation method

Ribbon bonding technique has recently been used as an alternative to wire bonding in order to improve the reliability, performance and reduce cost of power modules. In this work, the reliability of aluminium and copper ribbon bonds for an Insulated Gate Bipolar Transistors (IGBT) power module under power cycling is compared with that of wire bonds under power and thermal cycling loading conditions. The results show that a single ribbon with a cross section of 2000 μm × 200 μm can be used to replace three wire bonds of 400 μm in diameter to achieve similar module temperature distribution under the same power loading and ribbon bonds have longer lifetime than wire bonds under cyclic power and thermal cycling conditions. In order to find the optimal ribbon bond design for both power cycling and thermal cycling conditions, multi-objective optimization method has been used and the Pareto optimal solutions have been obtained for trade off analysis.     

航天器产品可靠性指标验证方法探究

对于受到多方条件限制的航天器产品而言,在交付验收阶段和型号出厂前,需要开展可靠性验证工作.航天器产品可靠性定量要求(指标)的验证可以选用多种方法进行.结合光学载荷产品可靠性指标验证的工作经验,提出了一种充分利用产品寿命周期各阶段的可靠性信息,采用贝叶斯法进行可靠性评估的方法.试验证明,这是一种经济、有效和可行的方法.     

2.5D硅转接板TSV结构研究

针对结构参数对TSV可靠性影响不明确的问题,文中采用有限元分析和模型简化的方法,分析了TSV结构在温度循环条件下的应力应变分布,并进一步研究了铜柱直径、SiO₂层厚度以及TSV节距等结构参数对TSV结构可靠性的影响。结果表明,采用文中的方法简化模型后得出的结果拟合度在0.95以上;在TSV结构上施加温度循环载荷时,在SiO₂界面会出现应力集中,而在钝化层中会出现应变增大;改变铜柱直径、绝缘层厚度和TSV节距将显著影响TSV结构的可靠性;减小填充铜的直径、增加SiO₂层的厚度、增加TSV节距,都将有助于减小TSV结构的最大应力。     

Heterodyne measurements of light propagation through atmospheric turbulence

Experiments on the phase perturbation of optical beams due to atmospheric turbulence were carried out using coherent radiation at 6328 Å, and 1.15 µ. The measurements were accomplished using a modulated interferometer to produce Doppler beats between a reference beam and one reflected from a plane mirror at a distance. This paper presents preliminary results of the phase measurements taken over total horizontal paths of 4.0 km and 23.8 km. The experimental data were consistent with a propagation theory based on the accepted model of atmospheric turbulence. Perturbation free apertures up to 10 cm were observed in good seeing conditions and as low as 1 mm under poor conditions. The corresponding variance of refractive index of the atmosphere showed a magnitude and diurnal variation consistent with published observations of temperature fluctuations.     

Reliability assessment from fatigue micro-crack data

Micro-cracks are generally defined to be cracks less than 1 mm in length, which propagate under cyclic stresses until they grow large and cause failure in an item (e.g. component or structure). This paper proposes a method of using data on `fatigue micro-crack growth in a material' to predict its reliability. It is increasingly important to model such cracks effectively, Their growth properties, which differ in several respects from larger cracks, are discussed. The paper develops a hierarchical model for the propagation of micro-cracks in a material. This stochastic model attempts to model the dependence of growth on local conditions, varying throughout the material, that causes variation in growth rates across the specimen. Given the model, data on micro-crack growth are used to compute posterior distributions of model parameters, from which a predictive distribution for reliability can be calculated. Computation of the posterior distributions is by Gibb's sampling and kernel density estimation. The methodology is illustrated with two data sets, one simulated and the other from a cast-iron specimen. Some possibilities for further work are presented     

综合利用电离层残差法和载波相位变化率法探测并修复周跳

针对参考站单站静态双频的特点,提出一种周跳检测与修复的新方法,根据接收机提供的锁定时间信息,综合利用电离层残差和载波相位变化率准确探测并修复周跳。检验证明该方法能够准确可靠地探测并修复失锁 3秒以内的周跳,避免了周跳对载波相位平滑伪距的影响。