Power Spectral Densities of Modulated Error-Correcting Coded Sequences

This paper finds an expression for the spectral density of an error-correcting coded digital sequence after modulation. This expression is valid for dependent source words and error-correcting linear block codes. Several examples are given of the ratio of the spectral density of the coded sequence to an uncoded sequence with identical source word rates for both independent and dependent source words.     

Repetition Rate Multiplication of Pseudorandom Bit Sequences

We develop a method for the repetition rate multiplication by a factor of $2 ^{ n}$ of pseudorandom bit sequences (PRBSs). It makes recursive use of an optical or-gate in feedback and ensures that the complexity of the resulting circuit is independent of the multiplication factor or the PRBS order to be rate multiplied. We employ an all-optical circuit comprising of two nonlinear fiber Sagnac interferometers and show error-free quadrupling of 12.5-Gb/s PRBSs to 50 Gb/s.      

Convergence of Oscillator Spectral Estimators for Counted-Frequency Measurements

A common intermediary connecting frequency-noise calibration or testing of an oscillator to useful applications is the spectral density of the frequency-deviating process. In attempting to turn test data into predicts of performance characteristics, one is naturally led to estimation of statistical values by sample-mean and sample-variance techniques. However, sample means and sample variances themselves are statistical quantities that do not necessarily converge (in the mean-square sense) to actual ensemble-average means and variances, except perhaps for excessively large sample sizes. This is especially true for the flicker noise component of oscillators. This article shows, for the various types of noises found in oscillators, how sample averages converge (or do not converge) to their statistical counterparts. The convergence rate is shown to be the same for all oscillators of a given spectral type.     

火焰光谱探测器的光谱匹配因数

从测量得到的火焰光谱数据出发,对火焰探测器的光谱匹配因数进行研究,导出了光谱匹配因数的表达式,并在1～14μm波段范围内,计算了InSb红外探测器对不同温度黑体辐射的光谱匹配因数,为新型火焰探测器的研制提供一些必要的理论依据.     

红外系统光谱匹配因数

本文从最基本的红外系统－探测器对辐射源的响应出发，导出了辐射源组合系统的光谱匹配因数表达式。并在１￣１４μｍ波段范围内计算了常用红外探测器ＨｇＣｄＴｅ、ＩｎＳｂ、Ｐｂｓ对３００Ｋ、５００Ｋ、８００Ｋ、１０００Ｋ黑体辐射的光谱匹配因数。总结了这些红外探测器对不同温度黑体辐射光谱匹配因数的变化规律，可供红外系统设计者参考。     

噪声环境下遗传算法的收敛性和收敛速度估计

 问题求解的环境往往非常复杂,不确定的环境因素、人为因素等都可导致问题处于噪声环境,从而影响实际优化问题的目标函数值的评价.噪声环境下遗传算法的研究在国内外均起步较晚,特别是收敛性和收敛速度的分析是该领域急待解决的问题.本文根据优胜劣汰遗传算法的特性,基于吸收态Markov链的数学模型证明了噪声环境下优胜劣汰遗传算法的收敛性,提出了噪声环境下优胜劣汰遗传算法的首达最优解期望时间的估算方法.     

由相位谱重构离散信号的收敛性

研究由相位谱重构有限长离散信号，即幅度补偿问题的收敛性。文章独立地以归一化相关系数对经典迭代法的收敛性进行了证明。通过该证明，可体会到经典迭代法之所以可进行信号重构的机理。     

Detection of Tandem Repeats in DNA Sequences Based on Parametric Spectral Estimation

Tandem repeats, which occur frequently in genomes, are related to gene regulatory functions and various diseases. In this paper, an efficient algorithm for tandem repeat detection is proposed. In our method, the spectrogram of a DNA sequence is analyzed based on the autoregressive model. Then, significant peaks in the spectrogram are selected, and the corresponding regions in the DNA sequence are analyzed to search for tandem repeats. Experiment results show that our method has a superior performance in comparison with other algorithms.     

分形随机噪声信号处理的小波谱相关方法

提出了广义小波谱相关的概念,简要分析了其基本性质及其与谱相关的关系,通过对白噪声的谱相关和小波谱相关特性的研究,推导出分形噪声的小波谱相关函数,通过与白噪声的对比研究,分析了分形随机噪声在小波谱相关域的特性.考虑实际海杂波的特性,提出了一种分形噪声调幅调频的海杂波模型,分析了海杂波在小波谱相关域的表现,体现了小波谱相关对海杂波处理的优势.利用小波谱相关对分形噪声背景下的伪码脉冲串信号进行了识别仿真,结果表明该方法能有效抑制分形噪声,准确提取信号参数.     

精英类克隆选择算法平均收敛速度估计

克隆选择算法收敛速度估计是算法研究的一个难问题,目前还是处于初始的研究阶段。本文对一大类精英保持策略克隆选择算法的收敛速度问题进行了研究。首先利用算法种群中最佳个体的定向转移概率导出最佳个体的转移概率矩阵,针对实际应用中由于算法种群规模过大而导致该矩阵求取较困难的问题,将最佳个体的转移概率矩阵构造成满足一定条件的矩阵范数,从而提出一种更为简单有效的算法平均收敛速度估计的新方法。对不同的精英保持策略克隆选择算法进行了收敛速度估计仿真实验,其结果表明了该估计方法的有效性。     

Some Properties of Division Factor Sequences in Fractional Phase Locked Loops

In the field of fractional divider phase-locked-loops (PLL) there exist several different methods for generating the division factor sequences controlling the programmable frequency divider in the PLL. The overall behaviour of the fractional PLL strongly depends on the proper choice of the division factor sequence. Therefore some concepts for generating these fractional sequences are discussed and the behaviour of the division factor sequences will be analysed with respect to the overall PLL behaviour. In addition some sources of disturbances are mentioned.     

随机COMID的瞬时收敛速率分析

COMID(Composite Objective MIrror Descent)是一种能够保证L1正则化结构的在线算法,其随机收敛速率可由在线算法的regret界直接得到,但其最终解是T次迭代平均的形式,稀疏性很差.瞬时解具有很好的稀疏性,因此分析算法的瞬时收敛速率在随机学习中变得越来越重要.本文讨论正则化非光滑损失的随机优化问题,当正则化项为L1和L1+L2时,分别证明了COMID的瞬时收敛速率.大规模数据库上的实验表明,在保证几乎相同正确率的同时,瞬时解一致地提高了稀疏性,尤其是对稀疏性较差的数据库,稀疏度甚至能够提升4倍以上.     

Convergence of the Multidimensional Minimum Variance Spectral Estimator for Continuous and Mixed Spectra

A proof of the pointwise convergence of the multidimensional minimum variance spectral estimator as the region of data support becomes infinite is given. It is shown that an octant is sufficient to ensure that the minimum variance spectral estimator will converge to the true power spectral density. The proof is valid for 1-D, multidimensional, continuous, and mixed spectra. Another useful result is that a normalized minimum variance spectral estimator can be defined to indicate sinusoidal power for processes with a mixed spectrum. Finally, upper and lower bounds on the continuous portion of the spectral estimate are given.     

改善直接数字合成周期信号频域特性的三种波形序列

本文首次提出三种用于改善直接数字合成周期信号频域特性的波形序列,其中两种序列能够在不改变合成信号幅频包络的前提下提高其频率分辨率,另一种序列可用于波形数据限定的情况下频谱可变信号的合成。文中对三种序列的性质分别进行了推导和实例验证。     

Stochastic Modelling and 3D Minimum Variance Recursive Estimation of Image Sequences

In this paper the 3D minimum variance filtering problem is considered. The proposed spatiotemporal filter is derived according to the assumption that the 3D signal can be modelled by an ensemble of smooth 3D gaussian random fields. The resulting filtering algorithm is given by an optimal combination of three 1D estimators and is endowed with an information on the location about the spatiotemporal discontinuities of the signal. This allows the filter to conciliate the two opposite requirements of an effective noise reduction and edge preservation.     

L1-Norm Convergence Properties of Correlogram Spectral Estimates

This paper establishes the following results concerning the estimation of the power spectrum of a single, deterministic, infinitely long signal. a) If S _x is the signal's power spectral density, correlogram spectral estimates obtained from increasingly longer signal segments tend to S _{x *} ? _x/2p in the L ¹-norm, where ? is the Fourier transform of the window used to generate the estimates. b) The L ¹-norm of S _x - S _{x *} ? _x/2p can be made arbitrarily small by an appropriate choice of window. It is further shown that the accuracy of the spectral estimates generated by a given window is related to a newly introduced function, termed the windowing error kernel and that this function yields bounds on the asymptotic error of the estimates. As an example, correlogram spectral estimates are used to analyze spectral regrowth in an amplifier.     

远距离热成像系统的光谱匹配因数

本文导出了远距离热成像系统的光谱匹配因数：并证明了红外系统的最大作用距离．     

Analyzing Product-Form Stochastic Networks Via Factor Graphs and the Sum-Product Algorithm

A large number of stochastic networks including loss networks and certain queueing networks have product-form steady-state probabilities. However, for most practical networks, evaluating the system performance is a difficult task due to the presence of a normalization constant. We propose a new framework based on probabilistic graphical models to tackle this task. Specifically, we use factor graphs to model the stationary distribution of a network. For networks with arbitrary topology, we can apply efficient message-passing algorithms like the sum-product algorithm to compute the exact or approximate marginal distributions of all state variables and related performance measures such as blocking probabilities. Through extensive numerical experiments, we show that the sum-product algorithm returns very accurate blocking probabilities and greatly outperforms the reduced load approximation for loss networks with a variety of topologies. The factor graph model also provides a promising approach for analyzing product-form queueing networks.     

频谱相位编码OCDMA系统的误码特性研究

本文利用中心极限定理和雅可比变换的方法，对频谱相位编码(spectral phase encoding)OCDMA系统中多址干扰和解码器输出信号的统计特性进行了研究，并据此推导出多址干扰和背景噪声共同作用下系统新的误码率公式．本文还分析了系统性能与判决门限选择的关系，数值结果表明：系统最佳的判决门限Rth=√P0/2，在此判决门限的条件下，系统的性能满足高速全光通信的需要．