联合深度限幅的自适应数字预失真技术研究

提出联合峰均比降低技术(PAPR)和数字预失真技术(DPD)对国标地面数字电视广播（DTMB）系统功率放大器进行线性化处理. PAPR降低技术采用深度限幅滤波,计算复杂度低. DPD方法则是采用基于查找表的预失真技术,为提高查找表的收敛速度,自适应算法采用变步长的RASCAL算法,并在查询表收敛过程中,对查找表进行拉格朗日内插. 仿真结果表明,使用深度限幅与预失真联合技术时功放效率可以得到较大提高. 以功率回退值为指标,与单独使用预失真技术时的功放效率相比,可以减少功率回退4.5dB,ACPR可以达到-45dBc. 与传统的联合技术相比,ACPR可以改善4dB.     

基于查找表的功放线性预失真方法研究

在无线通信系统中,高功率放大器因其具有非线性特性,会导致频谱再生和邻道干扰等问题.为克服这一特征,采用一种基于查找表的自适应预失真方法.首先对查找表进行初始化,再采用自适应算法实时更新查找表内容,从而有效消除功放的非线性失真.仿真实验表明,该自适应预失方法可降低互调失真(IMD),能有效提高功放线性度,从而提高系统性能.     

基于查找表的功放线性预失真方法研究

在无线通信系统中,高功率放大器因其具有非线性特性,会导致频谱再生和邻道干扰等问题。为克服这一特征,采用一种基于查找表的自适应预失真方法。首先对查找表进行初始化,再采用自适应算法实时更新查找表内容,从而有效消除功放的非线性失真。仿真实验表明,该自适应预失方法可降低互调失真(IMD),能有效提高功放线性度,从而提高系统性能。     

无线射频通信中改进式功放数字预失真技术

提出了一种用于无线射频通信系统中补偿由于高功率放大器引起的非线性失真的改进式的基带查找表预失真方法.查找表预失真方法是基于对高功率放大器的非线性特性进行训练,由训练得到的功放非线性参数对功放进行线性化校正,以达到预失真补偿的效果.由计算机仿真结果和实测结果表明,该方法具有稳定性高、收敛速度快、补偿算法简单、硬件开销较少、补偿效果较好等优点.     

一种基于记忆LUT的多倍频程预失真方案

针对多载波无线通信系统中多倍频程功率放大器存在的强非线性失真与记忆效应失真问题,提出了一种基于记忆查找表的LUT+MP多倍频程预失真方案。方案模型由记忆查找表(LUT)和记忆多项式(MP)串联构成,采用间接学习法的LMS和RLS算法对模型参数训练辨识。仿真结果表明,针对维纳模型高功率放大器,在输出功率回退OBO=2.27 d B时,对Wiener模型功放的三阶互调失真改善达到了55.9 d B,五阶互调失真改善达到了44.5 d B。与现有的LUT+FIR和LUT+并联FIR预失真方案相比较,能带来更好的建模精度和线性化效果。同时,设计使用的学习算法简单实用,稳定性能好。     

一种基于Hammerstein模型的数字预失真算法

记忆非线性放大器的预失真问题一直是预失真技术的难点.本文首先介绍了数字预失真器的几种模型结构和识别算法,它们虽然能够很好地实现功率放大器的线性化,却存在运算量较大的问题.结合LS算法和Hammerstein模型的优点,提出了一种基于Hammerstein模型的数字预失真算法,用几次简单的迭代运算代替一次复杂的直接运算,从而以较少的运算量,获得较好的线性化性能.通过计算机软件仿真验证了这种算法的有效性,它能以较少的参数,快捷、简便地实现记忆非线性功率放大器的预失真,显著提高了放大器的线性化性能.     

用于多比特正交发射机的基于图形转换的全自动预失真技术

多比特正交架构是全数字发射机方案中最有前景的一种,但因为存在着显著的非线性,而需要复杂的二维预失真,并且前人提出的迭代测量法建立预失真表时间长约1ms.本文提出了图样转换的方案来解决预失真表建立时间过长的问题.本文方案将预失真表的建立时间缩短到20μs之内,同时对7.2dB PAPR和40MHz带宽的长期演进(Long Term Evolation,LTE)信号,布局前仿真中预失真后信号带内误差能减少到-30.07dB.本文方案不仅节省了预失真过程的时间和功耗,也使多比特正交发射机预失真表的实时建立首次成为可能.     

一种基于滤波器矩阵的Hammerstein预失真器

预失真器建模的准确性是保证有效补偿带记忆功率放大器非线性失真的重要因素之一,尤其是模型对功率放大器逆记忆特性的描述能力.针对目前预失真器模型对功率放大器逆记忆效应描述不充分的问题,提出一种改进的Hammerstein预失真器,该预失真器以查找表级联滤波器矩阵作为其实现形式,较好地描述了功率放大器的逆记忆特性.仿真实验表...     

基于查找表的基带自适应预校正方法的系统仿真

本文提出了一种高功率放大器的非线性预校正系统设计方案.本系统基于复数增益的查找表,通过射频解调后的基带IQ信号与原始基带IQ信号的比对来更新查找表,从而实现数字基带信号的自适应预失真.Matlab仿真结果表明,本校正方法收敛速度快,校正效果明显,较好地补偿了高功率放大器的幅度失真和相位失真.     

基于极坐标的自适应数字预失真器

基于极坐标方式,以Taylor级数拟合预失真器的AM/AM和AM/PM特性曲线,输入信号幅度作为索引信号创建幅度与相位并联的两张查找表,运用最小均方自适应算法更新表项系数来补偿功放的非线性,设计了自适应数字预失真器.通过Matlab搭建了基于16-QAM调制解调的自适应数字预失真系统.仿真结果表明,邻近通道功率比降低近20dB,功放的线性度得到了明显改善.     

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.     

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     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

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     

Journal of Donghua University ( English Edition) Contents of Volume 31

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