Data Extraction from Terahertz Time Domain Spectroscopy Measurements

The potential of terahertz (THz) time domain spectroscopy to simultaneously determine the complex dielectric parameters of materials and their geometrical thickness is of high interest for scientific spectroscopy and for general metrology. This paper provides an overview of the background of the data extraction from THz measurements and discusses the accuracy and ambiguity of this extraction process. It is shown that the signal to noise ratio of the measurement as well as the bandwidth of the accessible THz spectrum define the limitation of the achievable accuracy in the data extraction.     

Comparative Study of Material Parameter Extraction Using Terahertz Time-Domain Spectroscopy in Transmission and in Reflection

As no terahertz signal is transmitted through opaque materials, reflection terahertz time-domain spectroscopy is obviously the dedicated setup. On the other hand, optical properties of transparent and thick samples are extracted more accurately with transmission terahertz time-domain spectroscopy. In this paper, we report the intrinsic frontier above or below which it is preferable to use either reflection or transmission setup for probing with the best accuracy possible a given sample.     

Uncertainty in Terahertz Time-Domain Spectroscopy Measurement of Liquids

Terahertz time-domain spectroscopy (THz-TDS) is a significant technique for characterizing materials as it allows fast and broadband measurement of optical constants in the THz regime. The measurement precision of the constants is highly influenced by the complicated measurement procedure and data processing. Taking THz transmission measurement of liquids into account, the sources of error existing in THz-TDS process are identified. The contributions of each source to the uncertainty of optical constants in THz-TDS process are formulated, with particular emphasis on the effect of multilayer reflections and plane wave assumption. As a consequence, an analytical model is proposed for uncertainty evaluation in a THz-TDS measurement of liquids. An actual experiment with a Di 2-Ethyl Hexyl Phthalate (DEHP) sample is carried out to show that the proposed model could be a basis to evaluate the measurement precision of optical constants of liquids.     

数据挖掘在IGBT模型参数提取中的应用研究

针对半导体器件的SPICE模型参数提取,提出了一种正向处理技术。对于选定的器件和模型,大量运行不同模型参数组合下的SPICE仿真,获得各种不同的电特性曲线,形成超大规模的数据集。若通过测试得到了确实的测试数据,则通过数据挖掘和人工智能中的数据处理算法得到数据集中、最匹配的曲线项,直接给出模型参数的估计值。针对IGBT模型,通过批量仿真获得约15 k个数据,使用kNN算法和多元回归法对测试曲线构成的测试集进行了参数提取。结果表明,该方法能快速获取器件的模型参数,具有稳健性的优点。该方法为研究者对器件模型特性提供了有益的认识。     

双基线极化干涉合成孔径雷达的植被参数提取

由于单基线极化干涉SAR技术(如三阶段法、ESPRIT算法等)反演植被参数的方法受限于具有最小地体幅度比的观测数据,影响冠层或地表有效相位中心的估计,因此往往低估植被的高度。该文通过增加另一个基线的极化干涉SAR数据在一定程度上解决单基线反演技术存在的这个缺陷,并适当改进双基线极化干涉SAR技术,降低植被参数估计的动态偏差,最后用模拟数据和实际数据验证了该方法。     

FEA实验数据进行参数提取的线性回归技术

本文讨论了对场发射阵列（ＦＥＡ）的实验数据利用线性回归的技术得到表征ＦＥＡ器件特性的几个关键多数的方法。并将这种方法应用于我们自己的ＦＥＡ器件样品。根据实验数据得到了器件的关键参数并证实了ＦＥＡ对特性满足ＦｏｗｌｅｒＮｏｅｄｈｅｉｍ方程。文章还对非线性因素对参数估计所带来的偏差问题进行了讨论。     

MOSFET模型＆参数提取

器件模型及参数作为工艺和设计之间的接口，对保证集成电路设计的投片成功具有决定意义。本文介绍了电路模拟中常用的几种MOSFET模型，并着重探讨了使用自动参数提取软件提取一套准确的模型参数的具体工作步骤。     

雷达辐射源特征参数提取算法复杂度分析

特征参数提取是雷达辐射源信号分选和识别的关键步骤.针对目前对特征参数提取算法时间复杂度研究较少较浅的现状,从算法设计和数据结构入手,推导了5种特征参数提取算法的时间复杂度数学表达式,并对其进行了分析.最后通过计算机仿真实验验证了所推导的时间复杂度的正确性.     

基于PHAF的多普勒参数估计

在通常情况下,多普勒参数是影响SAR成像质量的主要因素。目前,估计多普勒参数的算法主要有Mapdrift、相位梯度自聚焦以及对比度最优自聚焦等自聚焦算法,这些算法有一个共同的缺点,不能估计并补偿高阶多普勒参数。该文通过基于乘积型高阶模糊度函数(Product High-order Ambiguity Function, PHAF)算法来估计多普勒参数的新方法,该方法无需利用惯导数据预先计算多普勒调频斜率初值,可与杂波锁定并行完成,并且具有估计高阶多普勒参数的能力。仿真实验比较了PHAF和MapDrift分别在小信噪比,存在高阶误差时的自聚焦能力。结果说明该算法计算量小、鲁棒性强、估计精度高,在小信噪比情况下仍可得到较准确的估计结果。最后给出的成像结果说明该文提出的算法能够大大改善成像分辨率。     

VDMOS场效应晶体管电路模型的构造及参数提取

从VDMOS的物理结构出发建立子电路模型,进而导出描述其交直流特性的参数及模型公式.相对以往文献的结果,该模型避免了过多工艺参数的引入,同时对子电路进行了有效的简化.在参数提取软件中的加载结果表明,该模型结构简单,运算速度快,物理概念清晰,拟合曲线与测试数据符合精度高(直流误差5%以内,交流误差10%以内),适于在电路模拟及参数提取软件中应用.     

逻辑参数库中Power参数的提取

本文介绍了在LPE这个逻辑参数(电学参数)自动提取工具里，Power参数的定义以及提取Power的输入激励波形的生成算法。对于不同的Related Pin以及电路的反馈特性需要不同的激励波形生成算法。     

VDMOS场效应晶体管电路模型的构造及参数提取

从VDMOS的物理结构出发建立子电路模型,进而导出描述其交直流特性的参数及模型公式.相对以往文献的结果,该模型避免了过多工艺参数的引入,同时对子电路进行了有效的简化.在参数提取软件中的加载结果表明,该模型结构简单,运算速度快,物理概念清晰,拟合曲线与测试数据符合精度高(直流误差5%以内,交流误差10%以内),适于在电路模拟及参数提取软件中应用.     

Parameter Estimation of LFM Signals Based on Scaled Ambiguity Function

A method based on the scaled ambiguity function for parameter estimation of LFM signals under noncooperative conditions is presented. In the proposed algorithm, the scaling principle is employed to remove the linear frequency migration brought by the coupling between the time variable and the lag variable. Afterward, the Fourier transform is performed for feature extraction of LFM signals on the centroid frequency versus chirp rate plane. The method avoids centroid frequency information loss, which is almost inevitable in the Radon-ambiguity transform. Furthermore, fractional lower-order statistics and the scaled ambiguity transform are combined to improve the performance in practical impulsive noise environments. Simulation results show that the fractional lower-order scaled ambiguity transform is robust for both Gaussian and impulsive noise, and it achieves significant performance improvement in a heavy noise environment.     

Stability Analysis and Synthesis of Discrete Impulsive Switched Systems with Time-Varying Delays and Parameter Uncertainty

This paper studies the problem of stability and stabilization for discrete impulsive switched systems with time-varying delays and norm-bounded parameter uncertainty. By using the Lyapunov–Krasovskii functional technique and the method of linear matrix inequalities (LMIs), some delay-dependent criteria on asymptotic stability are established. A stabilization condition using feedback control is formulated to stabilize the closed-loop system. Some numerical examples are given to illustrate the main results.     

太赫兹雷达目标微动特征提取研究进展

微动特征是目标探测与识别的重要辅助特征。随着近年来太赫兹研究的兴起,太赫兹雷达目标微动特征提取正在逐渐凸显出其特殊优势。本文首先对近年来国内外太赫兹频段雷达目标微动特征提取方面的研究进行整理总结,从太赫兹频段微动特性分析、微动特征提取和微动目标成像等几个方面进行了深入的介绍和分析。然后针对太赫兹频段的优势和特殊性,介绍了本单位在太赫兹微动目标特性分析、特征提取和高分辨高帧频成像方面的工作。最后对太赫兹雷达目标微动特征提取的发展趋势进行了展望,并分析了本领域值得进一步深入研究的技术方向和有待解决的技术难题。      

N-Sequence RSNS Ambiguity Analysis

The robust symmetrical number system (RSNS) is a modular system formed using Nges2 integer sequences and ensures that two successive RSNS vectors (paired terms from all N sequences) differ by only one integer. This integer Gray-code property reduces the possibility of encoding errors and makes the RSNS useful in applications such as folding analog-to-digital converters (ADCs), direction finding antenna architectures, and photonic processors. This paper determines the length of combined sequences that contain no vector ambiguities. This length or longest run of distinct vectors we call the RSNS dynamic range (Mcirc). The position of Mcirc which is the starting point in the sequence is also derived. Computing Mcirc and the position of Mcirc allows the integer Gray-code properties of the RSNS to be used in practical applications. We first extend our two-sequence results to develop a closed-form expression for Mcirc for a three-sequence RSNS with moduli of the form 2^r-1,2^r,2^r+1. We then extend the results to solving the N-sequence RSNS ambiguity locations in general     

Upstream Problem Solving Under Uncertainty and Ambiguity: Evidence From Airport Expansion Projects

Environmental changes are common during development of large engineering (infrastructure) projects. To accommodate them when they occur, developers design and physically execute the upstream base building with preliminary information about the downstream business-critical fit-out. Base-building subsystems provide service space for occupancy, whereas fit-out subsystems make the space functional. We build theory on design under uncertainty and ambiguity from case study research, drawing on theory of preliminary information exchange in concurrent development. We find that the base-building subsystem shows low sensitivity to incremental changes in fit-out. However, it shows high sensitivity to radical changes, unless the two subsystems interact in a modular fashion. In the face of slow resolution of downstream uncertainty and difficulties in decoupling the physical interfaces (as is the case in modular design for example), upstream developers avoid starvation by making working assumptions at risk and exploring the space of possible design solutions through an early “optioneering” stage. Two patterns for problem-solving upstream stand out: 1) iterate design when preliminary information is either ambiguous or precise, but unstable and 2) build buffers in the design definition to absorb foreseeable changes when the preliminary information lacks precision but is not ambiguous. Buffers can be designed out if downstream uncertainties resolve favorably before the buffers are physically executed.      

太赫兹在片S参数测量串扰修正方法研究

为修正太赫兹在片S参数测试时探针间串扰误差,提出了一种包含串扰的新型误差模型,以及基于此误差模型的校准方法.该方法分别对待校准和测试时的串扰误差.基于这一概念,开发了一种新型12项误差模型,将串扰误差视为与被测件(DUT)并联的独立二端口网络.在测量DUT前通过测量一对长度与DUT相同的开路标准实现对串扰误差的表征并移...