用模拟退火算法从S参数提取HFET小信号等效电路模型参数

微波集成电路和微波器件的设计需要准确地提取HFET的小信号等效电路模型参数.采用带回火的模拟退火算法从S参数提取HFET小信号等效电路模型参数,得到了高质量的解.计算结果是全局最优解,摆脱了初始值的影响,并且克服了局部优化算法遇到的不收敛或收敛到错误解的问题.利用测量得到的栅电阻,计算结果的精度可以进一步提高.这个算法同样也适用于HBT、电容和电感等器件模型参数的提取.     

用改进的差分进化算法提取HEMT小信号模型的参数

高电子迁移率晶体管(HEMT)以其噪声低和频带宽等特点在微波毫米波领域得到了广泛的应用,本文在传统优化方法的基础上,对差分进化算法进行了改进,并基于该算法对HEMT小信号等效电路模型进行了模型参数提取。实验结果表明,2×20μm GaAs HEMT器件S参数模拟结果和测试结果在40 GHz频率范围内吻合很好,误差在2%以内。     

应用-种组合优化算法提取场效应管模型参数

提出一种将模拟退火法与基于主成份灵敏度分析的空间坐标变换相结合的优化算法，用以精确提取微波场效应管小信号等效电路参数。该法具有快速收敛，能够消去模型坏条件等优点，从而提高了低灵敏度元件Ｒｉ、Ｒｇ、Ｒｄ等的提取精度，使各个模型参数均能得到精确、快速提取。     

应用遗传算法提取GaAs场效应管小信号模型参数

利用阻抗矩阵法求出GaAs场效应管的小信号等效电路S参数,并提出应用遗传算法提取等效电路模型参数.该法具有收敛快速、精确度高的特点,使各个模型参数均能得到较为精确快速的提取.     

微波功率FET小信号等效电路参数提取方法

文章针对Ｓ参数提取微波功率ＦＥＴ小信号等效电路参数方法,着重论述二种改进的算法,并应用于我所研制的微波功率２１００μｍ栅宽的ＧａＡｓＭＥＳＦＥＴ管芯的小信号等效电路１３只元件参数计算,计算得出的Ｓ参数与实验数据相吻合,提高了计算速度和精度。     

基于遗传算法的场效应管模型参数的提取

建立一个精确的微波场效应管的等效电路模型对于微波场效应管电路的非线性分析,模拟和优化设计是十分重要的.本文提出了一种新的提取场效应管的等效电路模型参数的方法--混合遗传算法.混合遗传算法将遗传算法和模拟退火法有机地结合,发挥了两者的优点.文中给出了应用混合遗传算法提取场效应管NE32584的等效电路模型参数的实例,得到了具有很高精度的模型参数.     

氮化镓功率器件小信号模型参数提取算法研究

针对氮化镓高电子迁移率晶体管(GaN High Electron Mobility Transistor,GaN HEMT)小信号等效电路模型参数提取和优化过程中存在的误差累计问题,基于GaN HEMT 19元件小信号模型,提出了一种扫参与迭代相结合的参数提取算法.该算法在迭代过程中,每次使用比前一次更准确的元件值进行计算,可使结果趋向最优解.通过Mat-lab编程实现后计算结果表明,仿真与实测S参数在0.1～40 GHz频率范围内吻合良好.     

器件模型参数优化提取的混合算法

本文论述了器件模型参数优化提取中常采用的L-M算法存在的一些问题.提出了用(LM-BFGS)混合算法提取器件模型参数,这对优化收敛有极大的加速作用.本文例举了大量实验函数的计算结果并结合MOSFET的参数提取,证明了该算法可以大大减少迭代的次数和计算非线性目标函数的次数.     

GaAsFET大信号等效电路参数提取

将新型算法—退火遗传算法用于GaAsFET大信号等效电路模型参数的提取,给出了具体流程并提取了器件的模型,结果表明该算法快速可靠,文中为提取大信号模型提供了新的方法,并扩展了遗传算法的应用。     

用模拟退火算法提取HBT的小信号等效电路参数

采用模拟退火算法对基于物理模型的ＧａＡｓ／ＧａＡｌＡｓｈｂｔ小信号等电路参数进行了优化提取。计算结果表明，采用模拟退火算法，避免了求导优化算法收敛于局域极小的缺陷，结果与初值选取无关，精度得出了提高，速度也较快，是一种较好的等效电路参数优化提取算法。     

Characterization and modeling of AlGaN/GaN MOS capacitor with leakage for large signal transistor modeling

Dual mode AlGaN/GaN metal oxide semiconductor (MOS) heterostructure field-effect transistor (HFET) devices were fabricated and characterized. In HFET mode of operation the devices showed an f/sub t//spl middot/L/sub g/ product of 12GHz/spl middot//spl mu/m at Vgs=-2 V. The AlGaN devices showed formation of an accumulation layer under the gate in forward bias and a f/sub t//spl middot/L/sub g/ product of 6GHz/spl middot//spl mu/m was measured at Vgs=5 V. A novel piecewise small signal model for the gate capacitance of MOS HFET devices is presented and procedures to extract the capacitance in presence of gate leakage are outlined. The model accurately fits measured data from 45MHz to 10GHz over the entire bias range of operation of the device.     

长波及中波红外鱼眼镜头的计算机设计

按Tchebycheff积分方法计算垂轴像差曲线面积,进而建立基于这种面积的像质指标,以模拟阻尼最小二乘法中评价函数的构思,并将其融合于适应法光学设计程序中,实现两种优化思想的“复合”;借助这种复合优化能迅速改善初始结构,促成鱼眼镜头自动设计过程快速收敛;提出光学自动设计中的虚拟现实技术和多链节——可循环的“病态”处理方法;其中虚拟透镜技术可克服久禁不止的光线“溢出”、摆脱“病态”和求得最简光学结构,虚拟变光阑技术和“病态”处理方法可克服优化过程中的慢收敛、发散、震荡或无优化解的困难,促成快速而稳定地收敛;最后列举了实例.     

Ⅲ族氮化物及其二维电子气输运特性的研究进展

Ⅲ族氮化物半导体具有宽禁带和直接带隙 ,导带能谷间距大 ,强场输运特性好。Al Ga N/Ga N异质结产生高密度的二维电子气 ,屏蔽了杂质和缺陷的散射 ,改善了低场输运性能。它弥补了宽禁带半导体输运性能差的缺点 ,已研制成大功率的 HFET。利用强场下的速度过冲有望消除阴极端的速度凹坑 ,显著改进器件性能。电子气的强二维性使输运特征依赖于器件结构和工作状态 ,器件设计变为一个剪裁电子状态和输运特性的复杂工程。文中综述了 族氮化物及其二维电子气的输运特性 ,讨论了从输运特性出发 ,优化 HFET性能的问题。     

New continuous heterostructure field-effect-transistor model andunified parameter extraction technique

A continuous model for heterostructure field-effect transistors (HFETs) suitable for circuit simulation and device characterization is proposed. The model is based on the analytical solution of a two-dimensional Poisson equation in the saturation region. The HFET saturation current and saturation voltage have been experimentally determined by differentiating the output characteristics in a unified and unambiguous way. The results are used for the systematic extraction of device and process parameters. The deduced values agree well with other independent measurements. The results of experimental studies of HFETs with nominal gate lengths of 1, 1.4, 2, and 5 μm are reported. The models and techniques presented here are successfully applied to all these devices. A large short-channel effect is observed for the 1-μm-gate HFET. The gate length dependences of the device parameters determined by the method reveal that the effective gate length in the self-aligned structures is approximately 0.25 μm shorter than the nominal gate length     

Mode-coupling control and new index profile of GI POF for restricted-launch condition in very-short-reach networks

This paper confirms that numerical aperture (NA) is a key factor in mode coupling [the energy transfer among propagating modes in multimode fibers (MMF)] and that providing a high NA is a viable solution to reduce mode coupling in graded-index plastic optical fibers (GI POFs). Furthermore, the authors propose a new refractive-index-profile design of GI POFs when only small mode groups are launched (restricted-launch condition), which is a combined profile with the index exponents lower and higher than optimum value for the core center and periphery, respectively. The advantage of the new index profile is investigated both experimentally and theoretically. Furthermore, it is verified that the high-bandwidth performance of GI POF with the new index profile under the restricted-launch condition is maintained even when statistical fiber bendings are added to the GI POF and when misalignment is caused at the optical coupling between the light source and the GI POF.     

考虑量子力学效应的超薄栅氧nMOSFET's直接隧穿电流二维模型

研究了超薄栅氧MOS器件的直接隧穿(direct tunneling,DT)电流模型问题.利用修正的WKB近似方法(modified WKB,MWKB)得到电子隧穿栅氧的几率,利用修正的艾利函数(modified Airy function,MAF)方法计算得到在高电场条件下载流子的量子化能级,从而计算出在不同偏置条件下的DT电流.模型实现了nMOSFET's栅隧穿电流的二维模拟,可以模拟在不同栅漏偏置条件下的器件工作情况,具有较广泛的适用性.通过对比表明,本模型能够与实验结果很好地吻合,且速度明显优于数值方法.利用模型可很好地对深亚微米MOS器件的栅电流特性进行预测.     

Accurate small-signal modeling of HFET's for millimeter-waveapplications

In this paper we discuss the small-signal modeling of HFET's at millimeter-wave frequencies. A new and iterative method is used to extract the parasitic components. This method allows calculation of a π-network to model the heterojunction field-effect transistor (HFET) pads, thus extending the validity of the model to higher frequencies. Formulas are derived to translate this π-network into a transmission line. A new and general cold field-effect transistor (FET) equivalent circuit, including a Schottky series resistance, is used to extract the parasitic resistances and inductances. Finally, a new and compact set of analytical equations for calculation of the intrinsic parameters is presented. The real part of Y₁₂ is accounted for in these equations and its modeling is discussed. The accounting of Re(Y₁₂ ) improves the S-parameter modeling. Model parameters are extracted for an InAlAs/InGaAs/InP HFET from measured S-parameters up to 50 GHz, and the validity of the model is evaluated by comparison with measured data at 75-110 GHz     

Improved RF modeling techniques for enhanced AlGaN/GaN HFETs

Modeling procedures of an AlGaN/GaN HFET that incorporate the effects of both a GaN cap layer and an AlN sub-buffer layer are presented. A single off-state measurement method to extract all eight parasitic elements of an enhanced HFET has been successfully applied. In addition, procedures to model the nonlinear drain-to-source current characteristics featuring a kink are described.     

A symmetrical nonlinear HFET/MESFET model suitable forintermodulation analysis of amplifiers and resistive mixers

We propose a new symmetrical heterojunction FET (HFET)/MESFET model to predict intermodulation distortion in amplifiers and resistive mixers. The model is symmetric. That is, drain and source of the intrinsic FET are interchangeable. This reflects the characteristics of most microwave FET's. The model has few fitting parameters and they are simple and straightforward to extract. The model was installed into Hewlett-Packard's harmonic-balance program microwave design system and verified by measurements. The verification shows excellent results for an MESFET and an HFET in both amplifier and resistive mixer configurations