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由于超声波时差法测风速对于时间测量要求很高,0.1 m/s速度精度时差Δt仅为400 ns,这就需要很高的采样率和大的系统存储空间。将时差Δt的测量分为"粗测"、"细测"两部分,用插值相关的办法可以有效解决这个问题。插值后通过传统互相关法可准确测量时差Δt的"细测"部分,然而这种方法只有在平稳噪声环境下效果较好,局限性较大,实际测量中结果误差较大。为了克服这问题,通过广义互相关算法(GCC)可提高这部分时差测量的准确性。广义互相关法将回波信号在频域进行加权处理,提高了信号频谱特性,抑制了噪声对测量的影响。实验结果表明,广义互相关算法在白噪声以及有色噪声中都有很好的效果,测量准确性大大提高。 相似文献
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野值是一种异于总体数据的非高斯量测值,在实际传输中野值的加入常使信号出现厚尾特性。粒子滤波是基于贝叶斯框架的适用于非线性/非高斯系统的一种滤波方法。如果在量测噪声中存在野值会使粒子滤波的精度下降。该文利用学生t分布建模量测噪声模型,结合变分贝叶斯(VB)递推方法设计一种新颖的边缘粒子滤波(MPF-VBM),它在滤波同时可对量测噪声的包括均值在内的全部参数进行实时估计。进一步,利用该估计算法,在量测噪声时变条件下研究了噪声关联的粒子滤波算法(MPF-VBM-COR)。通过对典型单变量增长模型的仿真,验证了所提两种算法相比于已有算法在状态估计上具有更优越的鲁棒性。 相似文献
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Ryynänen OR Hyttinen JA Laarne PH Malmivuo JA 《IEEE transactions on bio-medical engineering》2004,51(9):1547-1554
The purpose of the present study was to examine the spatial resolution of electroencephalography (EEG) by means of inverse cortical EEG solution. The main interest was to study how the number of measurement electrodes and the amount of measurement noise affects the spatial resolution. A three-layer spherical head model was used to obtain the source-field relationship of cortical potentials and scalp EEG field. Singular value decomposition was used to evaluate the spatial resolution with various measurement noise estimates. The results suggest that as the measurement noise increases the advantage of dense electrode systems is decreased. With low realistic measurement noise, a more accurate inverse cortical potential distribution can be obtained with an electrode system where the distance between two electrodes is as small as 16 mm, corresponding to as many as 256 measurement electrodes. In clinical measurement environments, it is always beneficial to have at least 64 measurement electrodes. 相似文献
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Phase noise in two mutually coupled oscillators is analyzed by the describing function method, and the after-lock phase noise of the oscillators is calculated in terms of their free-running phase noise. A new phase-noise measurement technique based on inter-injection locking of two similar oscillators is proposed. Experimental results are presented, which confirm the theory. It is shown that in the case of zero phase of coupling coefficient, the system is in the optimum state where the only required parameter for the measurement is the locking bandwidth. In this optimum state, as far as the locking bandwidth is measured correctly, imperfections such as the frequency drift, parameters discrepancy, and nonlinear susceptance of the oscillators have no serious effect on the measurement accuracy. The proposed method is compared to the conventional ones. 相似文献
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Doppler tracking of planetary spacecraft 总被引:2,自引:0,他引:2
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Yisong Dai 《Microelectronics Reliability》1997,37(6):893-899
In this paper, some problems with previous ultra-low noise measurement methods have been discussed, then a double-channel preamplifier cross-spectrum measurement method has been adopted, different from the previous cross-correlation method [A. van der Ziel, Noise: Sources, Characterization, Measurement, p. 54. Prentice-Hall, Englewood Cliffs, NJ (1970), L. Stor, Experimental techniques in noise measurement with special emphasis on precision measurement, Proc. 10th Int. Conf. on Noise in Physical Systems, pp. 551–560. Budapest, Hungary (1989)] in that an average periodogram using a windowing procedure has been performed. The theoretical analysis shows that the expected value of the cross-spectrum is incoherent with background noise and zero-drift from the preamplifier and power supply system, the average periodogram can decrease the variance of the periodogram and the additional bias of the cross-spectrum periodogram.Experimental results demonstrate that if the equivalent input noise of measuremental set-up is two orders of magnitude lower than the noise of each preamplifier, then an ultra-low noise spectrum can be measured accurately, the low limit is about 0.1 nV/√Hz at 1 kHz, which is 20 dB lower than the noise of each preamplifier. The thermal noise of a small resistance and the shot noise of a diode under forward conditions have been measured, the experimental results are in good agreement with the theoretical value, this means that this method is feasible and accurate for an ultra-low noise spectrum measurement.Finally, the noise spectrum analysis procedure based on the curve fitting method has been presented, which ensures that we obtain an accuracy value of three noise components in the semiconductor, i.e. noise, white noise and g-r noise. This noise spectrum analysis method is a useful tool for investigation of noise mechanism, the diagnosis of defects in semiconductors and reliability estimation. 相似文献
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在微波噪声参数测量系统中,通过使用自动源调配器来改变源反射系数的方法,可以方便地求出各个参数。根据对所引入的自动源调配器的分析,总结出源调配器自身的额外噪声误差是可以忽略的,并在对自动源调配器与噪声源级联后组成的单端口网络进行误差分析后,做出了超噪比的补偿运算,这种误差修正方法在很大程度上减小了测量误差量级。使用该补偿方法可以在噪声参数测量时进行更大范围的源阻抗调配,并提高噪声测量的准确度。 相似文献
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针对测距测角相对导航中测量噪声不可精确获知往往导致相对定位精度下降的问题,本文研究了基于自适应扩展卡尔曼滤波(EKF)的相对导航算法。利用泰勒级数展开对测量矩阵进行线性化处理,并利用自适应时变噪声估计方法对测量噪声方差阵进行动态估计,状态噪声方差阵通过惯导特性的先验值获得。仿真结果表明,基于自适应EKF的相对导航算法可获得高精度且连续平滑的相对定位信息,尤其在测量噪声发生变化时更是表现出良好的导航参数估计性能。 相似文献
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A great deal of interest has been paid to autoregressive parameter estimation in the noise-free case or when the observation data are disturbed by random noise. Tracking time-varying autoregressive (TVAR) parameters has been also discussed, but few papers deal with this issue when there is an additive zero-mean white Gaussian measurement noise. In this paper, one considers deterministic regression methods (or evolutive methods) where the TVAR parameters are assumed to be weighted combinations of basis functions. However, the additive white measurement noise leads to a weight-estimation bias when standard least squares methods are used. Therefore, we propose two alternative blind off-line methods that allow both the variance of the additive noise and the weights to be estimated. The first one is based on the errors-in-variable issue whereas the second consists in viewing the estimation issue as a generalized eigenvalue problem. A comparative study with other existing methods confirms the effectiveness of the proposed methods. 相似文献
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一般配置非智能噪声源的噪声系数分析仪,当环境温度变化时,不能及时修正环境温度对噪声系数测量的影响。文中介绍了噪声系数的测量原理及影响噪声系数测量不确定度的各种因素。从Y因子法测量噪声系数的原理出发,详细论述并推导了环境温度变化时噪声系数测量结果的修正方法。通过补偿温度变化对测量结果的影响,提高噪声系数测量,特别是低噪声器件噪声系数测量准确度。最终通过实验数据验证了理论推导的正确性,提供了温度修正曲线。 相似文献
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《Advanced Packaging, IEEE Transactions on》2005,28(3):445-448
For the high-performance microprocessors with high-bandwidth I/O, the power supply noise needs to be controlled to ensure reliable high speed bus operation. This is generally done with high-quality package capacitors. These capacitors are generally lower equivalent series inductance (ESL) and lower equivalent series resistor (ESR). In this paper, we will present two implementations of an approach of using on-die resistors in series with the package capacitance to dampen the high-frequency noise. We will show by validation on the 90-nm technology that this technique is capable of reducing the noise by nearly 80% without adversely affecting the timings. The results of several validation experiments, including the measurement of noise and impedance of the I/O power delivery, and the post-layout simulation will also be presented. 相似文献
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捷联惯性导航系统(SINS)/视觉组合导航系统的融合算法主要是卡尔曼滤波,卡尔曼滤波实现最优估计的前提是系统的模型必须准确已知。对于SINS/视觉组合导航系统,获取量测信息需经图像处理、特征点提取和匹配等过程,使量测噪声统计模型不完全可知,这会导致卡尔曼滤波器的估计精度下降。因此,该文提出一种改进的自适应两级卡尔曼滤波,根据求解遗传因子的不同方法对传统自适应两级卡尔曼滤波进行改进。改进后的算法分别适用于系统噪声统计模型和量测噪声统计模型不准确可知两种情况,且二者具有统一的滤波框架。仿真结果表明,改进的自适应两级卡尔曼滤波比卡尔曼滤波精度高,有效解决了SINS/视觉组合导航系统因噪声统计模型不准确导致的精度下降问题。 相似文献
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提出了一种"开路-直通"的级联结构的二端口网络的晶体管高频噪声去嵌结构以及与此相关的基于噪声相关性矩阵的去嵌方法。和传统的需要配备两个"直通"结构的方法相比较,该结构及方法在版图配合的基础上,只需要使用一个"开路"结构和一个"直通"结构,而且多个不同尺寸的被测试器件结构可以共用一个直通去嵌测试结构进行测试及去嵌,结果显示,使用该方法测试及去嵌后的精度几乎不受影响。该方法的意义在于能极大地减少硅片上直通去嵌测试结构的数量从而节省硅片面积;同时,又减少了测试时间、提高了测试效率,极大地降低了成本。 相似文献
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Strasilla U.J. Strutt M.J.O. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1974,62(12):1711-1713
A measurement method is described which enables the separate measurement of the power spectra of the normal noise (white and l/f) superimposed on burst noise. With this method the power spectra of normal noise can be determined for each burst noise level. It is found that the clean burst noise and the superimposed normal noise are generated by statistically independent processes. The fact that burst noise devices have a higher 1/f noise power content than devices without burst noise indicates that there exists a common condition for the generation of burst noise and 1/f noise. 相似文献
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This paper presents a technique for characterizing the statistical properties and spectrum of power supply noise using only two on-chip low-throughput samplers. The samplers utilize a voltage-controlled oscillator to perform high-resolution analog-to-digital conversion with minimal hardware. The measurement system is implemented in a 0.13-/spl mu/m process along with a high-speed link transceiver. Measured results from this chip validate the accuracy of the measurement system and elucidate several aspects of power supply noise, including its cyclostationary nature. 相似文献
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Fixed-interval Bayesian smoothing in state–space systems has been addressed for a long time. However, as far as the measurement
noise is concerned, only two cases have been addressed so far : the regular case, i.e., with positive definite covariance
matrix; and the perfect measurement case, i.e., with zero measurement noise. In this paper we address the smoothing problem
in the intermediate case where the measurement noise covariance is positive semi definite with arbitrary rank. We exploit
the singularity of the model in order to transform the original state–space system into a pairwise Markov model with reduced
state dimension. Finally, the a posteriori Markovianity of the reduced state enables us to propose a family of fixed-interval
smoothing algorithms. 相似文献