一种新型高阶两通道时间交织∑△调制器系统结构

为了减小两通道时间交织∑△调制器中通道之间系数失配引起的折叠噪声，提出了一种新型的高阶两通道时间交织∑△调制器的系统结构．通过在传统噪声传递函数（NTF）中增加一个z=-1的零点，得到了一种新的NTF．新增的零点减小了NTF在高频处的幅值，从而能够减小两通道时间交织调制器结构中由于系数失配引起的折叠噪声．以实现新NTF的单通道单环4阶3b前馈分布型∑△调制器结构为原型，利用多抽样率系统和块数字滤波器基本原理，得到其对应的两通道时间交织系统结构．在两个通道的系数存在1％的失配条件下，     

一种新型高阶两通道时间交织∑△调制器系统结构

为了减小两通道时间交织∑△调制器中通道之间系数失配引起的折叠噪声,提出了一种新型的高阶两通道时间交织∑△调制器的系统结构．通过在传统噪声传递函数（NTF）中增加一个奈奎斯特频率处的零点,得到了一种新的NTF．新增的零点减小了NTF在高频处的幅值,从而能够减小两通道时间交织调制器结构中由于系数失配引起的折叠噪声．以实现新NTF的单通道单环4阶3位前馈分布型∑△调制器结构为原型,利用多抽样率系统和块数字滤波器基本原理,得到其对应的两通道时间交织系统结构．在两个通道的系数存在1％的失配条件下,调制器的信号噪声失真比只降低了3．1dB,这表明系数失配对该调制器的性能影响很小．     

一种新型高阶两通道时间交织ΣΔ调制器系统结构

为了减小两通道时间交织∑Δ调制器中通道之间系数失配引起的折叠噪声,提出了一种新型的高阶两通道时间交织∑Δ调制器的系统结构.通过在传统噪声传递函数(NTF)中增加一个奈奎斯特频率处的零点,得到了一种新的NTF.新增的零点减小了NTF在高频处的幅值,从而能够减小两通道时间交织调制器结构中由于系数失配引起的折叠噪声.以实现新NTF的单通道单环4阶3位前馈分布型∑△调制器结构为原型,利用多抽样率系统和块数字滤波器基本原理,得到其对应的两通道时间交织系统结构.在两个通道的系数存在1%的失配条件下,调制器的信号噪声失真比只降低了3.1 dB,这表明系数失配对该调制器的性能影响很小.     

一种新型级联∑△调制器系统结构

针对传统高阶级联∑△调制器结构电路复杂和对运算放大器的增益和线性度要求较高的缺点,提出了一种新型的2-3两级5阶多位量化器级联EA调制器系统结构.该结构的第1级采用2阶多位量化器的低失真∑△调制器结构,减小了运算放大器的非线性有限增益对调制器性能的影响.第2级采用信号传递函数等于单位增益的单环3阶∑△调制器,而不是传统级联结构中1阶或2阶∑△调制器,降低了电路的复杂程度.系统仿真结果表明:在最大增益为70 dB的非线性运算放大器增益、±0.2%的随机数模转换误差的非理想条件下,该调制器的最大信号噪声失真比能够达到95 dB.     

一种新型级联ΣΔ调制器系统结构

针对传统高阶级联ΣΔ调制器结构电路复杂和对运算放大器的增益和线性度要求较高的缺点,提出了一种新型的2-3两级5阶多位量化器级联ΣΔ调制器系统结构.该结构的第1级采用2阶多位量化器的低失真ΣΔ调制器结构,减小了运算放大器的非线性有限增益对调制器性能的影响.第2级采用信号传递函数等于单位增益的单环3阶ΣΔ调制器,而不是传统级联结构中1阶或2阶ΣΔ调制器,降低了电路的复杂程度.系统仿真结果表明：在最大增益为70 dB的非线性运算放大器增益、±0.2%的随机数模转换误差的非理想条件下,该调制器的最大信号噪声失真比能够达到95 dB.     

基于LabVIEW的多采样率数字滤波器1/3倍频程计算方法

利用多采样率数字滤波器法计算噪声1/3倍频程谱在硬件上设计困难。因此为降低设计的难度,提出基于LabVIEW实现多采样率数字滤波器法计算1/3倍频程。信号首先通过抗混叠滤波器降低信号频谱混叠,然后经过降采样减少数据计算量,最后利用数字带通滤波器实现通带内信号的能量衰减并进行均方根计算得到1/3倍频程谱值。通过Lab VIEW设计出FIR抗混叠滤波器和8阶巴特沃斯IIR数字带通滤波器,并在此基础上结合声卡搭建噪声分析系统完成1/3倍频程计算。结果表明,所设计的系统能快速准确地计算1/3倍频程谱值,得到理想的低频处频谱分析。     

∑-Δ ADC中数字抽取滤波器的多级实现

设计和实现了一个应用于音频∑-Δ模数转换器的数字抽取滤波器.该抽取滤波器采用多级多采样率结构,由梳状滤波器、补偿滤波器和2个FIR半带滤波器构成.补偿滤波器补偿梳状滤波器的通带滚降,补偿后整个抽取滤波器带内纹波小于0.006 dB,同时补偿滤波器实现了2倍降采样,减少了一个FIR半带滤波器的硬件开销.滤波器系数均采用规范符号编码实现,避免使用规模很大的乘法器单元.数字抽取滤波器采用SMIC 0.18μm CMOS工艺实现,芯片测试表明,该滤波器对256倍过采样率、三阶∑-Δ调制器的输出码流进行处理得到的信噪比达到107 dB,能够满足高端音频模数转换器的要求.     

超宽带系统中基于时域插值和抽取的新型Sigma-Delta转换器

无线通信系统中,超宽带(UWB)与正交频分复用(OFDM)技术相结合,具有超宽带、低功耗、抗多径衰落等优势.针对多频带OFDM-UWB信号的特点,提出一种基于时域插值和抽取的新型sigma-delta转换器用于完成数据的转换.时域插值使得多频带OFDM-UWB子载波间形成空隙,sigma-delta调制器将输入信号量化为1比特数据流的同时完成量化噪声整形.该sigma-delta调制器在量化噪声频谱中引入位于多频带OFDM-UWB子载波频点上的零点,将大部分量化噪声推到子载波空隙中,达到噪声整形效果.新型sigma-delta调制器采用无过采样结构,使得硬件实现相对容易,同时该结构还避免了OFDM系统的高峰均比问题.对信号进行时域插值与抽取降低了硬件复杂度和处理时间.理论分析和仿真结果表明了该调制器的有效性和可行性.     

低复杂度可变带宽全数字调制器

针对不同通信系统的不同带宽要求,提出一种低复杂度数字带宽可配置调制器(D-BCM),该调制器基于数字基带的可配置速率变换模块,其中可配置速率变换模块将多种不同输入码率转换为同一输出码率,使得后端数模转换(DAC)和射频调制(RF)与传统调制器相同。其核心部件可配置速率变换模块由两部分组成:第一部分是可配置速率变换的上采样单元;第二部分是单一的去镜像滤波器,且通过对多种去镜像滤波器的比较得出N yqu ist滤波器更适合低复杂度的实现要求。文中详细阐述D-BCM结构,并重点设计和实现可配置速率变换模块,最后在窄带系统中验证了调制器可行性。     

低复杂度可变带宽全数字调制器

针对不同通信系统的不同带宽要求,提出一种低复杂度数字带宽可配置调制器(D-BCM),该调制器基于数字基带的可配置速率变换模块,其中可配置速率变换模块将多种不同输入码率转换为同一输出码率,使得后端数模转换(DAC)和射频调制(RF)与传统调制器相同。其核心部件可配置速率变换模块由两部分组成:第一部分是可配置速率变换的上采样单元;第二部分是单一的去镜像滤波器,且通过对多种去镜像滤波器的比较得出Nyquist滤波器更适合低复杂度的实现要求。文中详细阐述D-BCM结构,并重点设计和实现可配置速率变换模块,最后在窄带系统中验证了调制器可行性。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with