基于ARMA-AKF的HRG随机误差建模分析

针对半球谐振陀螺(HRG)随机误差影响惯性测量单元测量精度的问题,提出了一种改进的基于自回归滑动平均(ARMA)模型和自适应滤波(AKF)的随机误差处理方法。该文对预处理的数据进行了自相关和偏相关特性分析,判断随机误差的适用模型,以及利用贝叶斯信息准则(BIC)准则估计ARMA模型的阶数,通过长自回归模型计算残差法获取模型参数,引入加权自适应因子在线调整一步预测误差阵和量测噪声矩阵用于改进滤波方程,并比较了5项主要误差系数值。结果表明,改进的算法能够有效抑制随机误差,为HRG的随机误差建模补偿提供了新方法。     

小波域中值滤波在激光陀螺信号处理中的应用

各种随机噪声是导致激光陀螺产生误差的主要因素，且其性质特殊，很难用传统的滤波方法去除。为了减小激光陀螺的随机误差，提高测量精度，提出了小波域的中值滤波器滤波方法，对激光陀螺零漂数据进行了滤波，并采用Allan方差法对滤波效果进行了定量分析。结果表明，此方法的滤波效果优于中值滤波和小波软阈值滤波效果，能有效地减小激光陀螺零漂信号中的角度随机游走、角速度随机游走、速率斜坡、零偏不稳定性和量化噪声，提高激光陀螺零漂输出的稳定性。     

基于Allan方差的MEMS陀螺仪性能评价方法

介绍了Allan方差的基本定义,以及采用Allan方差对陀螺零偏数据进行处理所需的测试系统构成及测试要点。详细推导了采用Allan方差法对陀螺仪噪声进行估算的过程,描述了应用MATLAB进行数据处理平台建设的主要流程。最后运用Allan方差理论对MEMS陀螺信号进行了定量分析,得到了MEMS陀螺仪的量化噪声系数、角度随机游走系数、偏差不稳定性系数、速率随机游走系数和速率斜坡系数5个误差源系数,实验表明该方法能有效地辨识微机械陀螺的各项随机误差成分,可以正确评价陀螺仪的性能指标,为陀螺仪的设计改进提供了依据。     

工作电流对二频机抖激光陀螺角随机游走影响的研究

理论上分析了二频机抖激光陀螺中由量子噪声和抖动噪声产生的角随机游走的影响因素;讨论了工作电流对量子噪声、比例因子的影响;根据陀螺参数定量的估计了抖动噪声产生的角随机游走的数量级。实验结果表明：电流在全测量范围内对陀螺比例因子的影响约为5ppm;对于本单位自行生产的二频机抖激光陀螺来说,由抖动噪声产生的角随机游走是总角随机游走的主要贡献者,比量子噪声产生的角随机游走大约高一个数量级。     

基于自适应卡尔曼滤波的光纤陀螺噪声系数估计方法

针对Allan方差法确定光纤陀螺ARW（angle random walk）噪声系数的一些不足,如大量存储数据、非实时处理、计算量大、耗时长等,提出了基于自适应卡尔曼滤波的光纤陀螺ARW系数在线估计方法.在角度随机游走、零偏不稳定性、角速率随机游走等主要噪声数学特性分析基础上,建立了光纤陀螺现代状态空间噪声误差模型,基于新息自适应卡尔曼滤波量测噪声协方差阵的迭代计算,实现光纤陀螺ARW系数的在线、实时估计,从而避免了存储大量历史数据,显著地减小了计算量,缩短了陀螺数据处理时间.数字仿真试验和光纤陀螺实测数据试验结果均验证了本文方法的可行性和有效性.     

基于自适应滤波器的MIMU/GPS组合系统的研究

设计了微惯性测量单元/卫星导航(MIMU/GPS)组合导航系统原理样机。针对低成本MIMU/GPS组合导航中的Kalman滤波器设计滤波参数(包括系统噪声方差阵Q和测量噪声协方差阵R)影响的问题,系统的分析了Kalman滤波器参数的选取对系统状态变量的估计精度和收敛性能的影响。根据分析设计了自适应估计技术的Kalman滤波器。试验结果表明:对于低成本MIMU/GPS组合导航采用自适应估计技术估计可得到满意的性能,在静态条件下,位置精度优于5 m(标准差),速度精度优于0.1 m/s;系统提供水平姿态角精度优于0.2°;航向角精度优于0.5°(磁罗盘辅助)。     

光束质量稳健估计非线性拟合求解方法

激光光束质量M2因子在测量过程中,数据不可避免的存在随机和非随机两类误差,为了减小测量过程中受到误差的影响以提高系统的测量精度和稳定性,针对不同误差影响进行分析并提出相应的解决方法。在随机误差情况下,对传统双曲线拟合的正规方程组解法进行了改进并提出了加权拟合的正规方程组解法;而对于非随机误差情况,双曲线拟合尚未发现有效的解决方案,为此提出了基于稳健估计的双曲线拟合方法,并对此进行了深入的理论研究。实验表明,在数据存在非随机的情况下采用稳健估计的方法,可以克服非随机误差对参数估值产生的影响,使其拟合优度接近最优值,稳健估计的误差要比正规方程组的误差低一个数量级。因此,稳健估计可有效地提高测量M2因子的测量精度,对评价光束质量方面有着重要的应用价值。     

再入式无源光纤陀螺随机误差分析

文章利用Allan方差法对Sagnac敏感环分别为20m和200m的再入式无源光纤陀螺（RE－FOG）的随机误差进行了详细的分析。结果表明,这种光纤陀螺的噪声中含有传统光纤陀螺中反映了不明显的指数相关（Markov)噪声,并且占有重要地位。估计了两个陀螺系统的噪声水平。最后认为,通过深入研究再入式光纤陀螺的误差源和相应的抑制措施,它的精度有望接近和达到传统光纤陀螺的水平。     

基于新息突变约束的自适应卡尔曼滤波研究

针对微机电系统(MEMS)陀螺仪易受影响且随机误差较大,导致建立模型不准确和测量精度低的问题,该文提出了一种改进的自适应卡尔曼滤波方法。首先建立ARMA模型,在传统卡尔曼算法中引入衰减系数以减小系统旧值的影响,同时引入基于系统新息突变的预测误差矩阵清除系统的突变值。使用Allan方差对原始陀螺仪数据和滤波后的陀螺仪数据进行分析对比。结果表明,实验所用陀螺仪的角度随机游走、零偏不稳定性和角速率随机游走至少小了1个数量级,标准差明显减小,这表明改进算法有效抑制了随机噪声,提高了MEMS的性能。     

基于椭球拟合的MIMU系统自标定方法

针对微惯性测量单元(MIMU)测量精度的提高,提出一种自适应的MIMU系统自标定方法。通过MIMU系统陀螺仪和加速度计误差模型分析,将陀螺仪和加速度计的误差模型转化为一个线性回归方程,使用椭球拟合的最小二乘方法对MIMU系统进行拟合,最后运用多次拟合模式进行总体标定。采用实验室三轴转台进行实验验证,得到标定的姿态测量系统的精度提高了3个数量级,证实了此标定方案的可行性。     

Flicker noise and the estimation of the Allan variance

Flicker noise is a random process observed in a variety of contexts, including current fluctuations in metal film and semiconductor devices, loudness fluctuations in speech and music, and neurological patterns. The quadratic-mean convergence of appropriate estimates of the Allan variance for flicker noise is established when the latter is modeled as a stochastic process with stationary increments. A precise asymptotic expression of the mean-square error is given along with the rate of convergence     

Design of efficient CMOS ring oscillator-based random number generator

Although studies have investigated the effects of flicker noise on randomness, such effects demand further examination. Despite the random nature of flicker noise, a coloured distribution is observed in the power spectral density of flicker noise, indicating to a correlation in between adjacent samples. Studies have employed ring oscillators (ROs) that produce random numbers by sampling the digitised analogue signals of their outputs. This sampling procedure may change the spectral properties of flicker noise resulting from the folding effect of noise. Another topic of interest regarding sampled flicker noise is its random behaviour. To investigate the contribution of flicker noise, white noise, and their combination to randomness, we produce synthetic bit streams of these noise sources. From observations, we find that flicker noise contributes to the entropy of bit streams. Using the generated synthetic bit streams, we also explore the entropy dependence of a bit stream on the sampling period and analyse and compare the entropy levels of the outputs of ROs operating in strong and weak inversion. Results of the comparison demonstrate that only one RO operating in weak inversion may be sufficient to attain the required entropy level for qualifying the generated bit stream as random. The results of the analysis are also confirmed by measurements. In addition, the paper proposes an efficient design of a RO-based random number generator.     

CMOS LC-oscillator phase-noise analysis using nonlinear models

In this paper, a second-order stochastic differential equation is used as a tool for the analysis of phase noise in a submicron CMOS LC oscillator. A cross-coupled topology typical of integrated CMOS designs is considered. Nonlinear limiting and mobility degradation effects in the circuit are modeled and used to predict the statistics of the random amplitude and phase deviations in terms of design variables. Assuming Gaussian noise disturbances and describing the phase noise as a random diffusion process, the average phase-noise power spectrum is derived and its accuracy verified with measurement and simulation results. Calculations for phase noise arising from stationary tank noise, nonstationary channel thermal noise, and flicker noise are discussed. The analysis is used to emphasize the fundamental power/performance tradeoff associated with compensation of tank losses via adjustments in the power supply and device size.     

A Spectral Model for RF Oscillators With Power-Law Phase Noise

In this paper, we apply correlation theory methods to obtain a model for the near-carrier oscillator power-spectral density (PSD). Based on the measurement-driven representation of phase noise as a sum of power-law processes, we evaluate closed form expressions for the relevant oscillator autocorrelation functions. These expressions form the basis of an enhanced oscillator spectral model that has a Gaussian PSD at near-carrier frequencies followed by a sequence of power-law regions. New results for the effect of white phase noise, flicker phase noise and random walk frequency modulated phase noise on the near-carrier oscillator PSD are derived. In particular, in the case of$1/f$phase noise, we show that despite its lack of stationarity it is possible to derive a closed form expression for its effect on an oscillator PSD and show that the oscillator output can be considered to be wide-sense stationary.     

A statistical model of flicker noise

By the method of fractional order of integration, it is shown that it is possible to generate flicker noise from "white" noise. A formal expression for the relation of flicker noise to white noise is given. An approximate method, amenable to the use of digital computers, is also given for the generation of flicker noise modulated numbers from random, independent numbers.     

Flicker (1/f) noise generated by a random walk of electrons in interfaces

Flicker noise can be generated by a random walk of mobile electrons in interfaces via interface states. It is proposed that these electrons interact with surface phonons to form polarons, which have very low mobilities. The flicker-noise model is a general one and may be used to explain flicker noise on MOSFET's, clean Si surfaces, metallic resistors, grain boundaries, amorphous layers, electron tubes, metal-insulator-metal junctions, diodes, and transistors. The dependence of the noise intensity is calculated as a function of device parameters such as interface state density, source-drain current, source-drain voltage, gate voltage, oxide layer thickness, grain size, temperature, size of the cathode, diode current, base current, and the surface recombination in the emitter-base area. Hooge's parameter is calculated quantitatively for several devices.     

An Adaptive Filtering Algorithm for Direct-Conversion Receivers: Architecture and Performance Analysis

An adaptive filtering algorithm is proposed in this paper to remove mismatch, dc offsets, flicker noise, and intersymbol interference (ISI) simultaneously in a direct-conversion receiver. mismatch is cancelled by a real valued adaptive mismatch canceller, and dc offsets are removed with one complex tap. In addition, flicker noise is modeled as a complex autoregressive (AR) random process so the system to be identified transforms to an ARX model. After estimating the coefficients in the model during the training period, the desired signal can be estimated using the decision feedback method. To accelerate the convergence of the algorithm and to reduce the estimation variance, an internal iterative algorithm is introduced. The convergence analysis of the proposed algorithm is also given, and the closed form of the minimum mean square error of the proposed algorithm is derived. Simulation results are provided to verify the superior performance of the proposed algorithm.