连续动力系统时间序列的非线性检验

用相位随机化的替代数据方法，研究了连续混沌动力系统时间序列的非线性检验判定.研究发现，在不同的采样情况下，混沌时间序列的非线性特性检验有所差异，尤其对于过采样时间序列，往往会出现虚假的判断结果.针对过采样时间序列，最好采用能够反映非线性特征的参数，作为检验统计量进行检验判断. 关键词： 替代数据 关联维数 连续时间序列 非线性检验     

数字全息图取样模型的简化研究

数字全息研究领域目前存在两种不同的数字全息图取样模型.按照这两种模型进行研究时, 不但涉及较复杂的数学运算, 在许多情况下还会导致不同的研究结果, 不便于理论分析及实际应用.基于对数字全息图记录的物理过程分析及电荷藕合器件(charge coupled device, CCD)几何结构的研究, 本文将这两种取样模型简化为相同的数学表达式. 利用数字全息图的余弦级数展开及取样定理对简化模型的研究表明, 简化模型不但具有清晰的物理意义, 而且可以方便地为应用研究服务. 基于简化模型对物光波通过光学系统到达CCD的数字全息记录系统进行了研究, 导出得到实验证实的波前重建表达式. 关键词： 数字全息 波前重建 相干光成像     

PID数字控制器多指标优化模拟设计方法研究

建立PID数字控制器多指标统一优化模拟设计方法;用SIMULINK仿真研究数字PID控制对模拟PID控制的复现能力和PID计算机控制系统的阶跃响应,用MATLAB仿真筛选PID参数的优化组合值;提出并建立了一种新的PID数字控制器多指标优化模拟设计方法,包括:PID初值确定方法、模拟PID优化参数MATLAB筛选方案和软件流程图、模拟PID参数转换数字PID参数的方法、SIMULINK仿真验证设计结果的有效性的方法等;研究表明,该方法可用于1～5ms采样周期的PID数字控制器多指标优化模拟设计,且能独立使用、无需PID经验数据和其它设计/整定方法;提供了4个代表性的实例设计,验证了该方法的有效性。     

上海光源数字化低电平控制系统的硬件设计与实现

 设计了上海光源高频低电平控制系统,它是以数字化技术为基础,采用上下变频和IQ调制解调技术,实现幅度、频率和相位的反馈控制。上海光源储存环的束流设计流强为300 mA,为了抑制由此带来的Robinson不稳定性和纵向零模束流振荡,加入了高频直接反馈和零模束流反馈环路。从上下变频技术、IQ调制解调技术、时钟分配及锁相技术等方面对上海光源数字化低电平系统的硬件设计及其实现进行了阐述,给出了该系统试验、高功率下运行的测试结果,实现了设计要求的幅度控制精度±1%、频率控制精度 ±10 Hz和相位控制精度± 1°的技术指标。     

光谱分析采样数据重建原始信号

用光谱分析方法分析信号的采样与恢复。用三个改进的升余弦脉冲构造对称的限带频谱F(ω),经理论推导获得时域信号f(t)。采用梳状函数δ_T(t)对f(t)采样,调节T值,获得Shannon采样。应用快速傅里叶变换,计算采样的频谱F_d(ω),比较计算频谱F_d(ω)与限带频谱F(ω)的差别,讨论由采样频谱F_d(ω)重建f(t)的方法。结果发现：计算频谱F_d(ω)与限带频谱F(ω)非常相似,由采样数据可以在时域直接重建原始信号,而由频谱数据经快速逆傅里叶变换,同样能准确重建原始信号。因此,信号存储,既可以存储其采样信号,也可以存储采样信号的数字频谱。     

Digital detection and processing of multiple quadrature harmonics for EPR spectroscopy

A quadrature digital receiver and associated signal estimation procedure are reported for L-band electron paramagnetic resonance (EPR) spectroscopy. The approach provides simultaneous acquisition and joint processing of multiple harmonics in both in-phase and out-of-phase channels. The digital receiver, based on a high-speed dual-channel analog-to-digital converter, allows direct digital down-conversion with heterodyne processing using digital capture of the microwave reference signal. Thus, the receiver avoids noise and nonlinearity associated with analog mixers. Also, the architecture allows for low-Q anti-alias filtering and does not require the sampling frequency to be time-locked to the microwave reference. A noise model applicable for arbitrary contributions of oscillator phase noise is presented, and a corresponding maximum-likelihood estimator of unknown parameters is also reported. The signal processing is applicable for Lorentzian lineshape under nonsaturating conditions. The estimation is carried out using a convergent iterative algorithm capable of jointly processing the in-phase and out-of-phase data in the presence of phase noise and unknown microwave phase. Cramér-Rao bound analysis and simulation results demonstrate a significant reduction in linewidth estimation error using quadrature detection, for both low and high values of phase noise. EPR spectroscopic data are also reported for illustration.     

光衍射数值模拟中不同抽样方法的适用性分析

基于标量衍射理论和快速傅里叶变换,分析了光衍射的数值模拟时可以采用的不同抽样方法及其适用性。理论分析表明,按照抽样对象的不同,存在三种适用范围不同的算法:传递函数抽样法、点扩展函数抽样法和加权函数抽样法。其适用范围分别为衍射距离小于、大于和等于特征距离的情况。在Matlab软件环境下给出了三种算法的模拟计算实例,并与相应的实验结果进行了比较,证明了理论分析的正确性。最后还给出了一种无需改变抽样点数和抽样间隔就可计算任意距离衍射过程的自适应抽样算法及其在数字全息再现中的应用实例。     

Enhancement of Kerr nonlinearity and its application to entangled state discrimination

In this paper, the recent research on the enhanced Kerr nonlinearity and its application in entangled state discrimination is reported. Two kinds of dynamics, including interacting double dark resonances and spontaneously generated coherence, are presented to enhance the Kerr nonlinearity. The application of Kerr nonlinearity in quantum state discrimination is also discussed. An arbitrary Greenberger-Horne-Zeilinger state can be discriminated using two-photon polarization parity detection which resorts to cross-Kerr nonlinearity between a single-photon qubit and probe field. In addition, a scheme for Greenberger-Horne-Zeilinger state discrimination of matter qubits is also proposed using the dipole induced transparency in a cavity-dipole system.      

磁压缩器中相干同步辐射对束团品质的影响

在进行束团压缩时,相干同步辐射导致束团能量再分配,这会引入一定类型的非线性,目前普遍认为该非线性会导致束团发射度的急剧增加.本文通过模拟计算发现该结论只在一定条件下成立,同时还发现相干同步辐射引入固定类型的非线性,在特定参数下,该非线性能在一定程度上抵消束团原有的非线性,最终可能对束团品质有改善作用.     

彩色数字全息的非插值波面重建算法研究

彩色数字全息及多波长照明的数字全息检测研究中,避免插值误差的可变放大率波面重建是一个重要的研究内容.由于Fresnel衍射积分可以表示成Fourier变换及卷积两种形式,对应地存在两种波面重建算法：其一,将重建距离分为两段的衍射“接力”算法;其二,用球面波为重建波的卷积算法.文中对这两种算法进行理论分析及实验研究,讨论让重建计算满足取样定理的条件.结果表明,卷积算法较容易满足取样定理,能够获得较好的重建物光场. 关键词： 彩色数字全息 波面重建 衍射计算     

彩色数字全息的非插值波面重建算法研究

彩色数字全息及多波长照明的数字全息检测研究中,避免插值误差的可变放大率波面重建是一个重要的研究内容.由于Fresnel衍射积分可以表示成Fourier变换及卷积两种形式,对应地存在两种波面重建算法：其一,将重建距离分为两段的衍射“接力”算法;其二,用球面波为重建波的卷积算法.文中对这两种算法进行理论分析及实验研究,讨论让重建计算满足取样定理的条件.结果表明,卷积算法较容易满足取样定理,能够获得较好的重建物光场.     

像面数字全息的重建相位误差分析和改善

像面数字全息是数字全息技术中常用的测量和成像方式,它通常采用离散傅里叶变换和频率滤波的方法进行物光波的重建.本文讨论了这些算法对重建相位的影响.首先分析了频谱泄露对于相位误差的影响,结果表明当采样周期为整数时,重建相位误差很小,因此具有极高的相位重建精度;而当不满足整周期采样时,相位重建误差有了明显的增加.为了改善频谱泄露所引起的相位误差,采用Hanning函数对数字全息图进行了预处理,结果表明Hanning窗的加入能够有效地提高重建相位的准确程度.     

用于数字条纹轮廓术的一种基于广义分析模型的后滤波方法

由于数字投影和采集系统的非线性失真,传统的方法通常需对采集到的条纹进行低通或带通滤波从而抑制高次谐波并获取基频分量。基于广义分析模型针对数字条纹轮廓术提出一种对测量后的物体形貌进行后滤波的算法,消除了非线性失真对测量结果所造成的影响并提高了数字条纹轮廓术的测量精度。论述了条纹轮廓术的原理和广义分析模型,分析推导出后滤波算法。仿真和实验结果表明,后滤波方法能够快速准确地实现基于数字投影的三维形貌重建。     

The impact of ADC nonlinearity in a mixed-signal compressive sensing system for frequency-domain sparse signals

Compressive sensing (CS) holds new promises for the digitization of wideband frequency-domain sparse signals at sub-Nyquist rate sampling without compromising the reconstruction quality. In this paper, the impact of ADC nonlinearity in a CS receiver for frequency-domain sparse signals is investigated. In a mixed-signal CS system, signals are randomized before sampling. The signal spectrum at each building block in the mixed-signal CS system is analyzed and compared to a conventional Nyquist-rate sampling system. It is shown that the signal randomization in a mixed-signal CS system is able to spread the spurious energy due to ADC nonlinearity along the signal bandwidth, rather than the concentration of harmonic distortion on a few frequencies as it is the case for a conventional ADC. As a result, this paper shows that a significant ADC SFDR (Spurious Free Dynamic Range) improvement is achieved in a CS receiver when processing sparse signals. Simulation results are reported which are in good agreement with the qualitative analysis.     

Bit-rate adaptive optical performance monitoring method for fiber communication systems

A novel bit-rate adaptive method, by varying the optical sampling rates alternatively, is proposed in this paper for optical performance monitoring. Firstly, the theoretical model and the differential software-synchronized algorithm are developed. Then, the results verify that different channel bit-rate can be estimated with high precision irrespective of the modulation formats and signal distortion caused by chromatic dispersion and nonlinearity along the fiber link. Employing the proposed bit-rate adaptive method, the eye diagrams and Q values of 10 Gbit/s, 40 Gbit/s and even higher bit-rate signal can be monitored by a single optical performance monitoring system without any prior knowledge about bit-rate or signal period. The method we propose in this paper has the advantage that different channel bit-rates can be adaptively estimated and the differential software-synchronized algorithm is much simpler.     

数字全息中的一些基本问题分析

利用全息理论、傅里叶频谱分析和采样定理，在模拟和数字全息光栅实验基础上，分析了数字全息记录和再现中的一些基本问题。结果表明：在物体和CCD尺寸确定的情况下，记录光路结构参量只取决于对图像采样的要求及CCD的像素尺寸，只要物体到CCD的距离满足采样要求，数字全息图再现光场的三个部分就可以分离；用准直平行光作为记录参考光和模拟再现光，可以得到与物体大小和形状完全一致的再现像；采样条件对再现像的影响大于分离条件，减小参物光的夹角记录适当过采样的数字全息图，有利于提高再现像的质量；另外，在获得高质量再现像方面，根据物体的具体特征，尽可能记录高质量的数字全息图，与满足采样条件和分离条件具有同样重要的意义。     

Mathematical theory of slow light optical solitons

This paper studies the dynamics of slow light optical solitons from a mathematical point of view. It is mathematically proved that optical solitons, with a proper choice of time-dependent coefficients of dispersion and nonlinearity, can be made to slow down, and in the limiting case, to zero velocity. The types of nonlinearity that are studied in this paper are the Kerr law, power law, parabolic law, dual-power law and log law. Both bright and dark solitons are studied.     

Potential of digital holography in particle measurement

This paper describes the potential power of digital holography in particle measurement and its expected development in the near future. In digital holography, image reconstruction is carried out numerically on a computer using observed hologram patterns and some quantitative information can be derived from the reconstructed images. In this paper, the basic concept and procedure of digital in-line holography are shown mainly for particle depth measurement and the performance test results obtained in numerical simulations and experiments are demonstrated to examine the potential of the present method.     

Elliptic behaviour in the sawtooth standard map

This paper examines the standard map with sawtooth nonlinearity when the eigenvalues of the Jacobian lie on the unit circle. This is an area-preserving map of the torus to itself that is linear except on a line on which it is discontinuous. We discuss the closure of the set of images of the discontinuity and present numerical evidence that its Lebesgue measure is positive. Moreover, we present evidence that the measure of the closure of images of the discontinuity changes continuously with the parameter k. This means that the sawtooth standard map may exhibit coexistence of two positive measure subsets on which the dynamics is respectively regular and irregular in a certain sense. In the appendix we show that this map is equivalent to a map studied by electronics engineers as a model for the quiescent behaviour of a linear lossless digital filter with “two's complement” overflow.