Polarization Mismatch Errors in Radio Phase Interferometers

An analysis is presented which deals with the effects of polarization mismatch errors on the accuracy of a phase interferometer used for position location of unknown emitters relative to known calibration emitters. Closed-form expressions for the induced phase difference between interferometer antennas are derived for several combinations of receiving and transmitting antenna polarizations. Errors contributed by mechanical misalignment between antennas, as well as effects of power loss attributable to polarization mismatch, are also considered. The analysis leads to the conclusion that circularly polarized interferometer and transmitter antennas are best suited for the position location application, if it is assumed that polarization tracking of the interferometer antennas is not available. It is shown that a reasonable amount of ellipticity can be tolerated before the phase error becomes significant.     

光学镜面磁流变抛光误差的频谱特征与分布特性研究

通过分析磁流变抛光误差的频谱特征,发现严重影响成像质量的敏感频率成分误差,采用二维连续小波变换算法确定出敏感频率误差的具体分布区域,分析其演变特征及其与工艺参数之间的关系,为修正加工提供指导,以实现精确控制不同频率成分、不同分布区域光学加工误差和改善成像质量的目的.     

旋转变频频率捷变雷达本振跟踪误差的分析

 本文从旋转变频磁控管式频率捷变雷达的本振频率跟踪原理出发,分析了产生本振频率跟踪误差的主要因素。文中着重讨论了本振频率冷跟踪误差问题。同时也提出了热跟踪后本振频率跟踪误差项。分析前者,可以决定热跟踪电路应予修正的频率范围,而后者则是跟踪本振最终的误差。以上分析对如何采取措施提高系统的跟踪精度是有参考作用的。     

双基地及其联网系统的定位方法及精度分析

讨论的双基地系统中,发射站只起照射目标的作用,而接收站测量距离和、方位角及俯仰角。分析了双基地系统的目标定位方法和定位误差。通过分析定位精度在受控区域内的分布,提示了双基地系统的定位性能。文中对组网双基地系统的定位处理方法进行了讨论,其中采用WLS(Weighted Least Square)算法进行数据融合处理,仿真结果表明,联网双基地系统的定位精度大有提高。     

The Effect of Random Steering Vector Errors in the Applebaum Adaptive Array

The effect of random errors in the steering vector of an Applebaum adaptive array is examined. Each component of the steering vector is assumed to have a random error component uncorrelated between elements. The array output signal-to-interferenceplus-noise ratio (SINR) is computed as a function of the error variance. It is shown that the array output SINR becomes more sensitive to steering vector errors as more elements are added to the array and as the received desired signal power becomes larger. The variance of the steering vector error that may be tolerated depends on the required desired signal dynamic range. The larger the dynamic range that must be accommodated, the smaller the error variance must be.     

SINS制导工具误差补偿研究

 针对现有SINS制导工具误差模型不能满足“天地一致性”的问题，提出了基于实际弹道数据的SINS制导工具误差补偿方法，即首先建立SINS制导工具误差模型，然后采用改进的特征值有偏估计方法(LRE)估计具有复共线性特性的误差模型，最后利用该误差模型对捷联惯性仪表进行误差补偿。半物理仿真试验的结果表明，高度通道的最大测量误差由补偿前的52米降低到补偿后的8米，其余通道的补偿效果类似。这证明了该误差模型的正确性和估计方法的有效性，为将来SINS制导工具误差补偿和提高SINS制导精度提供了充分的依据。     

双基地聚束SAR运动误差分析

将三维坐标系引入运动误差分析,建立了对任意匀速直线航迹双基地聚束SAR运动误差统一、清晰的分析方法;在此三维坐标系下,推导出各种运动误差引起的相位误差的计算公式。推导基于一般的双基地聚束SAR回波模型,可适用于任意匀速直线航迹的双基地聚束SAR,并且将通常的单基地SAR的运动误差分析作为一种特例也涵盖在内。给出了位置误差、速度误差和加速度误差所造成的相位误差计算公式。从推导结果得出结论:位于不同平台的同一误差,引起的相位误差是不同的;在小场景假设下,双基地聚束SAR的运动误差是空不变的,与目标位置无关。计算机仿真验证了误差分析的正确性。     

Algorithmic support of a small-sized navigation system on the basis of the magnetoinertial course transmitter

The algorithmic support of a small-sized navigation system on the basis of the magnetoinertial course transmitter is considered; the support makes it possible to significantly reduce accumulating errors that are due to incomplete data on wind parameters and decrease requirements for random errors of initial data sensors.     

Inertial navigation system synthesis approach and gravity-inducederror sensitivity

A design criterion for improving the performance of the speed-damped inertial navigation system is presented. The single-axis speed-damped system is approached by optimizing the response of the system to a step-function disturbing signal. Butterworth, integral of time-multiplied absolute-value of error (ITAE), and solution-time standard forms are assumed to be the figures of merit for optimizing the system performance. The steady-state RMS (root-mean-square) gravity-induced navigation errors that are excited in the speed-damped system are determined for two gravity uncertainty models. The proposed figures of merit are compared. These comparisons reveal the sensitivity of predicted navigation errors to uncertainties in the gravity statistics, and simplify the choice of a suitable figure of merit for use in the design and error analysis of inertial navigation systems     

Effect of Radar Amplitude and Phase Weighting Errors on Clutter Rejection by Burst Waveforms

This correspondence derives simple expressions for the ambiguity function X and the Q function of uniformly spaced burst waveforms that are subject to independent random errors in the transmitter and receiver pulse phase and amplitude weightings. The expressions are similar to those in [1], but have been put in more simplified form, and are valid for more general sources of error.     

The effects of IF bandpass mismatch errors on adaptive cancellation

The effects of IF bandpass mismatch errors on adaptive cancellers are investigated. Frequency mismatch errors occur because of errors in the synthesis process of the bandpass filters which are designed to be identical and are in each input channel. Tapped-delay line transversal filters can be used to compensate for these frequency mismatches and thus improve cancellation performance. A pole/zero error model of the filters is developed whereby closed-form solutions of the maximum achievable average cancellation are obtained. This cancellation is a function of the order of the ideally matched frequency filters, the number of time-delay taps in the compensating transversal filter, the bandwidth-tapped time-delay product, and the constraints on these parameters. A design procedure is outlined for optimizing the canceller with respect to these parameters and their constraints; specifically, results are presented for Butterworth-type input filters. It is shown that an arbitrarily low output noise residue cannot be achieved by arbitrarily increasing the number of time-delay taps     

局域增强系统级联双频平滑技术研究(英文)

针对电离层误差时间梯度和空间梯度对局域增强系统的不利影响,提出使用级联双频平滤波方法解决此问题。级联双频平滤波先使用一个双频平滑滤波器精确估计电离层误差,利用得到的估计值修正码伪距观测量中的电离层误差,再使用一个双频平滑滤波器削弱噪声。这样,电离层误差被完全从平滑过程中移出,由L2码观测量引入的附加的噪声也被压制。基于中国民航新航行系统实验室的局域增强系统测试平台所采集的数据对级联双频平滤波的有效性和基于级联双频平滤波的局域增强系统的精度进行了分析。结果表明级联双频平滤波技术可以同时消除电离层误差时间梯度和空间梯度导致的平滑滤波残差和差分校正残差,并具有较低的滤波噪声。     

伺服加工平台的综合误差建模与补偿

伺服加工平台的几何误差是影响工件加工形貌精度的重要因素。在多体系统理论的基础上,首先,运用低序体阵列描述伺服平台多体系统的拓扑结构,建立各相邻体间的齐次变换矩阵,构建其综合误差模型;其次,利用雷尼绍测量系统对平台的定位误差、直线度误差、俯仰误差、偏摆误差以及两轴之间的垂直度误差进行辨识,将辨识得到的误差值代入构建的模型得出平台几何综合误差;最后,选择凸锥面、平面、球面3种面型工件补偿试验,对误差模型进行原理性验证。研究表明,经补偿后加工所得3种面型工件表面精度均提高了25%左右,证实了提出的补偿方法可用于伺服加工平台几何误差控制。     

基于足间距信息辅助的行人三维惯性定位算法

针对行人惯性导航系统误差随时间累积致使定位精度严重下降的问题,提出了一种基于足间距信息辅助的行人三维惯性定位算法。该算法在零速修正算法的基础上,利用足部安装的超声波测距模块实时测量行人双足相对距离,构建了基于超声测距的足间距约束模型,通过随机森林算法实现行人运动模式识别,并针对上下楼梯场景,利用台阶高度和足间距信息进行高度解算,最终实现行人三维惯性定位。在实际路线上开展了三维定位实验,数据显示,所提算法平面闭环误差为总路程的0.64%,与零速修正算法相比下降了55.56%,高度误差为0.06 m,与零速修正和气压计联合算法相比下降了64.70%,能够实现导航误差在总路程的0.50%以内的三维定位。实验结果表明,所提算法具有良好的工程应用价值。     

非理想均匀圆阵的波达方向和多普勒频率联合估计

针对均匀圆阵存在一般阵列误差 (如阵元的幅相误差和安装位置误差等 )的情况 ,提出了多个信号的波达方向和多普勒频率估计方法。直接利用均匀圆阵的阵列流形 ,采用波达矩阵法估计各个信号的多普勒频率。由一般阵列误差的统计特性构造加权矩阵 ,采用加权总体最小二乘法估计各个信号的波达方向。此方法具有鲁棒性强等特点。计算机仿真证明了此方法的有效性     

SAR resolution in the presence of phase errors

The author analyzes the effects of phase errors on synthetic aperture radar (SAR). The theory is applied to the following question: how does the achievable resolution vary with the carrier frequency when optimum quadratic focus and/or optimum processing interval (synthetic aperture length) are used? Numerous related results are given, so that much of the material is tutorial. For phase errors corresponding to uncompensated motion, the best achievable RMS resolution with any phase error spectrum satisfies the derived equation. For motion-induced phase errors it is seen that resolution improves with increasing carrier frequency when the first term in the expression applies (e.g. for phase errors concentrated at low frequencies) and resolution is independent of carrier frequency when R δ/v/v is the smaller term (e.g. with broad band or high frequency phase errors)     

Effects of Random Implementation Errors in Matched Filters for Binary Phase Code Pulse Signals

The effects of implementation errors in tapped delay line filters on the peak-to-sidelobe ratio and the signal-to-noise ratio of binary PSK pulse compression codes are considered. As error model the delay elements and weighting factors of such filters are assumed to have an error distribution with known mean and variance.     

Subspace array processing for the suppression of FM jamming in GPS receivers

The mitigation of FM interference in GPS receivers is considered. In difference to commonly assumed wideband and narrowband interferers, the FM interferers are wideband, but instantaneously narrowband, and as such, have clear time-frequency (TF) signatures that are distinct from the GPS coarse acquisition (C/A) spread spectrum code. In the proposed technique, the estimate of the FM interference instantaneous frequency (IF) and the interference spatial signature are used to construct the spatiotemporal interference subspace. The IF estimates can be provided using existing effective linear or bilinear TF methods. The undesired signal arrival is suppressed by projecting the input data on the interference orthogonal subspace. With a multisensor receiver, the distinctions in both the spatial and TF signatures of signal arrivals allow effective interference suppressions. The deterministic nature of the signal model is considered and the known underlying structure of the GPS C/A code is utilized. We derive the receiver signal-to-interference-plus-noise ratio (SINR) under exact and perturbed IF values. The effect of IF estimation errors on both pseudorange measurements and navigation data recovery is analyzed. Simulation results comparing the receiver performances under IF errors in single and multiantenna GPS receivers are provided.     

Reduction of Radar Tracking Errors with Frequency Agility

Frequency agility with random frequency in each pulse gives an improvement in radar angle tracking with a monopulse radar. With a conical-scan tracking radar, the glint error is reduced but fading error can be increased, and the net result must be studied in each case. A theory, usable for calculating angle tracking errors with a frequency agile radar, is given, and two examples showing the error reduction are presented. According to the theory, one part of the glint or fading spectra is ``smeared out' to half the pulse repetition frequency. Another part, the size of which depends on the degree of correlation between pulses, keeps the form of the original spectrum.     

安装误差对航空弧齿锥齿轮传动误差曲线的影响分析

传动误差曲线是评价弧齿锥齿轮副动态特性与啮合性能的重要指标,而安装误差又对动态特性与啮合性能产生直接影响。为此,分析了传动误差曲线对各类型安装误差变动的敏感性。依据局部综合法设计得到了齿轮副加工参数,形成弧齿锥齿轮副齿面。计入系统安装误差,通过对轮齿接触分析,得到了传动误差曲线与齿面接触印痕。定量分析了在不同安装误差条件下,传动误差曲线的变化情况,并对航空附件传动系统中的1对弧齿锥齿轮进行了传动误差曲线对安装误差的敏感性分析。结果表明:传动误差曲线对小轮安装距误差更为敏感。