样本容量对子孔径拼接检测精度影响的分析

应用数理统计理论及线性回归分析方法详细分析了在子孔径拼接检测中样本容量对测量精度的影响,通过计算确定了当子孔径拼接干涉检测中样本容量大于10 4时,即可保证检测精度,又能减小计算的复杂程度。     

FTIR光谱仪动镜速度和采样抖动的噪声分析

分析了傅里叶变换光谱仪由动镜速度和采样抖动的随机误差引起的光谱噪声,建立了基于噪声等效辐亮度差(NERD)和噪声等效温差(NETD)的噪声模型。分析表明,动镜速度的波动与抗混叠滤波器幅频响应、时间延迟的综合作用,以及采样触发的短时抖动,都会引起系统的噪声。通过MATLAB数值模拟,对动镜速度和采样抖动的噪声影响进行了仿真分析与模型计算,验证了理论模型,评估了实际仪器的噪声水平,为动镜控制、抗混叠滤波器的设计以及傅里叶变换光谱仪的噪声定量化计算和改善提供了依据。     

Estimation of the mean radar reflectivity from a finite number ofcorrelated samples

The authors compare estimators of the mean radar reflectivity on images with different spectral properties. By working on complex data rather than detected images, they can take the speckle correlation into account and thus obtain more accurate estimates. A robust and computationally efficient approximation of the optimal estimator is proposed     

Clock jitter impact on the performance of general charge sampling amplifiers

In this paper we present the detailed performance analysis of general charge sampling amplifiers (CSAs) due to clock jitter impact. A simple analytical model for quick estimation of the signal-to-noise ratio by considering clock jitter alone as a noise source is proposed for a general CSA. The proposed analytical model is compared with a previously published more complex model and also with the well known voltage sampling. Simulation results showing the performance due to clock jitter impact of CSAs are also presented here to confirm the proposed analytical model. The potential advantages of clock jitter tolerances in charge sampling are discussed in detail.     

Performance of a finite capacity asynchronous multiplexer with modulated input

In this paper, a finite capacity multiplexer in ATM environments with modulated deterministic input sources is investigated. We consider three cases of input traffic: (1) a fixed number of deterministic cell-generating sources, (2) a fixed number of sources where each source is modulated by an ON-OFF process, and (3) a variable number of ON-OFF sources, modulated by a call arrival process in conjunction with a connection admission control scheme. The main performance measures in this study are the cell and call blocking probabilities. For case (1), we give a tight upper bound for the transient phase of the state process to reach stationary conditions. The state probabilities and the corresponding cell blocking probability are determined by means of an exact analysis. For cases (2) and (3), where we deal with more complex input traffic, the compound state process and the overall cell blocking probability are analyzed using a quasi-stationary approximation technique. This approximation is validated by means of simulations. The analysis presented is shown to be able to give reasonably accurate approximate results for ATM-multiplexer performance for cases in which conventional simulation and analytic methods already approach computing time and complexity boundaries.     

Representation of electromagnetic fields over arbitrary surfaces bya finite and nonredundant number of samples

It is shown that the electromagnetic (EM) field, radiated or scattered by bounded sources, can be accurately represented over a substantially arbitrary surface by a finite number of samples even when the observation domain is unbounded. The number of required samples is nonredundant and essentially coincident with the number of degrees of freedom of the field. This result relies on the extraction of a proper phase factor from the field expression and on the use of appropriate coordinates to parameterize the domain. It is demonstrated that the number of degrees of freedom is independent of the observation domain and depends only on the source geometry. The case of spheroidal sources and observation domains with rotational symmetry is analyzed in detail and the particular cases of spherical and planar sources are explicitly considered. For these geometries, precise and fast sampling algorithms of central type are presented, which allow an efficient recovery of EM fields from a nonredundant finite number of samples. Such algorithms are stable with respect to random errors affecting the data     

采样时钟抖动在弱光信号检测中的影响分析

信号采样是弱光信号检测的关键技术环节,由于采样时钟抖动引起的采样信号的输出误差会影响后续的信号检测和处理。为此,分析了输入光信号为近高斯分布波形时由时钟抖动引起的采样误差,推导出了采样输出的信噪比损失公式,讨论了采样带宽、输入信噪比以及信号脉宽对输出信噪比损失的影响,最后以取样积分检测技术为对象,计算了在不同累积次数的条件下采样抖动对取样积分检测性能的影响,对弱光信号检测中的采样时钟选取具有一定的指导意义。     

The research of gradation fusion algorithm based on multisensor asynchronous sampling system

This letter explores the distributed multisensor dynamic system, which has uniform sampling velocity and asynchronous sampling data for different sensors, and puts forward a new gradation fusion algorithm of multisensor dynamic system. As the total forecasted increment value between the two adjacent moments is the forecasted estimate value of the corresponding state increment in the fusion center, the new algorithm models the state and the forecasted estimate value of every moment. Kalman filter and all measurements arriving sequentially in the fusion period are employed to update the evaluation of target state step by step, on the condition that the system has obtained the target state evaluation that is based on the overall information in the previous fusion period. Accordingly, in the present period, the fusion evaluation of the target state at each sampling point on the basis of the overall information can be obtained. This letter elaborates the form of this new algorithm. Computer simulation demonstrates that this new algorithm owns greater precision in estimating target state than the present asynchronous fusion algorithm calibrated in time does.     

Feasibility study of parameter estimation of random sampling jitter using the bispectrum

An actual sampling process can be modeled as a random process, which consists of the regular (uniform) deterministic sampling process plus an error in the sampling times which constitutes a zero-mean noise (the jitter). In this paper we discuss the problem of estimating the jitter process. By assuming that the jitter process is an i.i.d. one, with standard deviation that is small compared to the regular sampling time, we show that the variance of the jitter process can be estimated from thenth order spectrum of the sampled data,n=2, 3, i.e., the jitter variance can be extracted from the 2nd-order spectrum or the 3rd-order spectrum (the bispectrum) of the sampled data, provided the continuous signal spectrum is known. However when the signal skewness exceeds a certain level, the potential performance of the bispectrum-based estimation is better than that of the spectrum-based estimation. Moreover, the former can also provide jitter variance estimates when the continuous signal spectrum is unknown while the latter cannot. This suggests that the bispectrum of the sampled data is potentially better for estimating any parameter of the sampling jitter process, once the signal skewness is sufficiently large.     

Effect of soliton interaction on timing jitter in communicationsystems

Timing jitter in soliton communication systems is studied, taking into account both soliton interaction and amplifier noise. Deviations from Gordon-Haus jitter for closely spaced solitons are observed. A new analytical model for the timing jitter is proposed. The model presented considers interaction in a random sequence of solitons and the effect of the amplified spontaneous emission noise added in each amplification stage. We obtain a good agreement between the new analytical model and simulation results for practical communication systems     

Step-like signal processing with distinct finite number of levels

An algorithm for filtering noisy step-like signals is proposed. This algorithm is based on the assumption of Gaussian contamination. In this procedure data within a moving window is divided into two almost equal clusters and a hypothesis tests (F-test) for differences in the means between two such clusters. Histograms analysis and/or our a priori knowledge about the number of discrete amplitudes in the ideal noise free signal provide information that is used to filter the signal further and produce a clean signal with the desired number of discrete amplitudes (levels). As an illustration the method is tested by simulation     

Simple measurement of eye diagram and BER using high-speed asynchronous sampling

This paper discusses eye diagram measurement using asynchronous sampling. Simple bit error rate (BER) estimation from eye diagrams is performed. The use of high-speed asynchronous optoelectrical (OE) sampling enables the monitoring of fixed timing Q-factors to be performed simply.     

Rapid and precise read-out of terahertz sensor by high-speed asynchronous optical sampling

High-speed asynchronous optical sampling is used for the rapid and precise determination of transmission resonances of terahertz surface sensors based on asymmetric double split ring resonator arrays. The sensor response represented by a characteristic resonant frequency is determined to 0.66113 THz with an accuracy of ±325 MHz within 2 seconds of read-out time.     

Effect of distributed Raman amplification on timing jitter indispersion-managed lightwave systems

It is shown that the timing jitter of dispersion-managed soliton systems can be reduced by up to 40% by using a hybrid amplification scheme in which fiber losses are compensated by using erbium-doped fiber amplifiers in combination with backward pumped Raman gain. The jitter is smallest in the case of 100% Raman amplification, but considerable reduction occurs even for partial distributed amplification     

Synthesis of hazard-free control circuits from asynchronous finite state machines specifications

We discuss a special class of state machine specifications called Asynchronous Finite State Machines (AFSM) which allows the specification and synthesis of hazard-free control circuits under the unbounded delay model. AFSM are useful for the specification of sequential behavior involving choices. In contrast, models such Signal Transition Graphs (STGs) are more amenable to the specification of deterministic concurrent behavior.AFSM specifications are transformed into STGs and then to State Graphs (SGs). At the SG level of representation, hazards can be identified as a type of violations of the Complete State Coding (CSC) property. Algorithms for obtaining SGs from AFSMs, and conditions for hazard-free implementation of SG derived from AFSM are discussed. A hazard-free synthesis technique from SG is described. A CAD prototype called CLASS (Cirrus Logic Asynchronous Synthesis System) has been built and used to successfully synthesize and verify the state machine benchmark from HP Laboroatories [1] and various other real applications.     

泽尔尼克多项式拟合波面中采样点数目的研究

为了研究采样点数目对由泽尔尼克多项式所拟合的波面的拟合精度的影响,采用不完全归纳法进行了理论分析,取得了数十个不同的测试函数的采样点与拟合精度之间的数据关系.结果表明,不同的测试函数遵循相同的规律,即采样点数目达到一定数目后,拟合精度随采样点的变化很小;并通过计算得到了在较高拟合精度时,采样点数目与泽尔尼克多项式的项数...     

一种基于有限更新率的非带限信号采样方法

针对Shannon采样定理只能处理带限信号的缺陷,推导论证了一种基于有限更新率的非带限信号采样方法.该方法处理的是更新率有限的信号,先将信号经过一个采样核滤波,然后以不低于信号更新率的采样率对其采样,就可以借助抵消滤波器和范德蒙方程从采样点中重建出原信号.计算机仿真结果表明,该方法重建原信号的精确度较高,并且具有较好的抗噪声性能,信噪比为20dB时信号估计值的均方差只有10-5的数量级,完全能满足实际工程的需求.     

Ao基于振荡采样的真随机数发生器设计与实现

基于时钟振荡采样原理,提出一种真随机数发生器结构。利用噪声源数学模型保证噪声源的可靠,利用并行输出及控制的方式确保随机数的输出速率,参考FIPS 140-2设计在线随机测试模块以避免遭受硬件篡改问题。通过测试表明,序列的产生速率可达33.5Mb/s,且具有较高的质量,可应用于密码芯片等相关领域产品中。     

The reconstruction of a band-limited function and its Fouriertransform from a finite number of samples at arbitrary locations bysingular value decomposition

A method for the stable interpolation of a bandlimited function known at sample instants with arbitrary locations in the presence of noise is given. Singular value decomposition is used to provide a series expansion that, in contrast to the method of sampling functions, permits simple identification of vectors in the minimum-norm space poorly represented in the sample values. Three methods, Miller regularization, least squares estimation, and maximum a posteriori estimation, are given for obtaining regularized reconstructions when noise is present. The singular value decomposition (SVD) method is used to interrelate these methods. Examples illustrating the technique are given     

The bispectrum of sampled data. II. Monte-Carlo simulations ofdetection and estimation of the sampling jitter

For pt.I see IEEE Trans. Acoust. Speech, Signal Process., vol.41, no.1, p.296-312 (1993). The effect of jitter in sampling on the spectrum and bispectrum of the sampled data has been considered previously. Methods of detecting the presence of jitter in a uniform sampling process and of estimating its variance based on a test statistic calculated from the bispectrum estimates have been proposed. The present authors demonstrate, by means of Monte-Carlo simulations, how these results can be applied in an actual case. For this purpose, samples taken from a stationary band-limited process in sampling times given by a random jitter process are generated by computer. The authors then apply the jitter detection and estimation methods that have been developed in previous work and study how their performance depends on signal duration and on jitter variance. They examine the actual simulation results concerning detection probability, estimation bias, and estimation variance in comparison with the theoretical results. This comparison indicates that the bispectrum is a domain where jitter detection and estimation with high performance can be achieved, provided that a signal with sufficiently long duration and high skewness is available