一种基于二极管的L波段行波管预失真电路

该文分析了行波管放大器的输入输出曲线,并计算得到理想预失真线性化电路的增益和相位响应曲线。提出一种由两条非线性支路组成的预失真电路,并讨论了电路中肖特基二极管主要参数对预失真曲线的影响。设计制作了L波段预失真电路,并与行波管放大器联合测试,实验结果表明,加入预失真电路后,行波管放大器三阶交调载波比IM3在输入功率回退3 dB、6 dB、9 dB时分别从-10.3 dBc、-14.3 dBc、-18 dBc改善到-12.1 dBc、-18.5 dBc、-26.9 dBc。     

一种行波管用毫米波射频预失真线性化器

射频预失真是提高功率放大器线性度的一种有效手段,精确补偿放大器的非线性失真需保证幅度和相位补偿同时满足要求.针对Ka波段行波管放大器的线性化,提出一种新型射频预失真电路.该电路由前置、后置电平调节模块和基于矢量合成技术的非线性信号产生模块构成.改变两电平调节模块的增益,可实现补偿区间的调节;改变非线性信号产生模块中两支路的偏置电压,可实现预失真补偿量调节及幅度/相位的独立调节.将实际电路与配用Ka行波管联测,在输出功率回退6 dB时,行波管三阶互调系数提高约11.5 dBc.     

一种用于K波段空间行波管模拟预失真电路的设计方法

空间行波管(TWT)预失真电路小型化、轻量化要求使得电路调试难度变大，迫切需要一种预失真电路精确仿真及设计方法来指导产品设计。该文在分析肖特基二极管等效电路模型基础上选择二极管MA4E2039作为非线性发生器件，并建立了MA4E2039的二极管仿真模型。之后通过分析反射式预失真电路结构，获得了影响电路性能的关键参数，并在元器件和版图联合仿真阶段对这些关键参数进行精确仿真。最后对依据仿真结果进行加工的预失真电路进行测试，发现仿真结果和电路实测结果偏差小于15%，将预失真电路与K波段行波管放大器级联实现在输入回退4 dB时3阶交调达到23.77 dBc，实现了行波管的线性化。可见该方法能够用于指导空间行波管预失真电路设计，帮助提高产品开发周期，对于预失真电路的小型化设计也有重要指导意义。     

Ka波段高精度模拟预失真线性化器

模拟预失真技术是改善行波管放大器非线性失真的一种有效方法,但补偿精度较低的缺点是制约其进一步发展的关键因素。增益相位独立调节技术和补偿曲线形状调节技术是提升模拟预失真补偿精度的重要技术。提出了一种适用于Ka波段行波管放大器的高精度模拟预失真器,该预失真器采用双路矢量合成式结构,在29~31 GHz 范围内,通过调节二极管偏置电压可以同时实现补偿曲线形状调节和增益相位扩张量独立调节,有效提升了补偿精度。与行波管放大器的联合测试结果表明,在30 GHz 时,该预失真器可以将行波管放大器的增益压缩从5.3 dB 减小到1.2 dB,相位偏移从62°减小到6.5°。线性化后的行波管放大器的非线性失真明显降低,在输出功率回退5 dB 时,三阶互调系数提高了9.3 dB。     

一种Ku波段空间行波管预失真器

提出一种无需直流偏置的Ku波段空间行波管预失真器.基于90°电桥、反向并联GaAs肖特基二极管对和负载电阻,产生预失真信号.同时可通过改变微带线长度和负载阻值实现可调性.此外,该电路自身具有良好的输入输出匹配特性,简化了电路结构.实测结果表明,该预失真器在带宽500MHz范围内可获得约7dB增益扩展和45°相位扩张.与行波管联测表明,行波管双音饱和输入功率回退3dB时,三阶交调可获得约6dB的改善效果.     

射频预失真器与基带预失真算法结合对行波管功率放大器线性化改善的影响

为了保证自适应算法的效果,一般会将行波管输出功率进行一定回退,但是会降低行波管的工作效率。通过在行波管前端加入射频预失真器,在额定输入功率范围内,线性化后的行波管的非线性失真现象得到了一定程度改善,然后再进行基带自适应算法的实现。X波段行波管在输出功率回退较少的同时,达到较好的非线性失真改善效果。     

Ku波段模拟预失真线性化器

提出了一种基于模拟预失真方法的线性化器设计。利用预失真技术设计行波管配用线性化器的数学模型,得出了预失真电路的功率转移特性曲线和相位特性曲线。预失真电路采用上下支路对消结构,通过二极管产生失真信号,并利用2个可调衰减器和可调移相器来调节其幅度和相位,以此补偿功率放大器的AM-AM,AM-PM失真特性,改善输出信号的线性度。此外通过改变二极管的偏压,线性化器能够提供不同种幅度和相位特性的组合方式,用于不同特性的功放。基于该模拟预失真方法设计了行波管线性化器,在给定的动态范围内幅度扩张5 dB,相位扩张40°。     

一种场效应管预失真电路对改善行波管非线性的作用

该文利用场效应管的非线性作用,替代通常预失真线性化电路中的衰减器和移相器,使这种预失真器在相位扩张量变化较小的同时,可以对增益扩张量进行调节控制,有效提升了预失真电路改善行波管非线性的作用。实际设计电路实验表明,在频率为8.38-8.58 GHz和额定输入功率范围内,设计了实际电路并完成相应的实验,获得了6 dB和45的增益和相位扩张以及15.4 dB的载波与交叉调制分量比值的改善。     

一种新型S波段微波功放预失真器

在微波功率放大器设计时,通常采用预失真技术来改善宽带信号的线性度.文章在普通的预失真技术基础上,对普通的反向并联肖特基二极管预失真线性化器电路进行了改进,使预失真器经过可调增益放大器后与微波功放直接级联.反向并联肖特基二极管对工作于相同偏置电压下,通过调节二极管的偏置电压, 同时控制IM3 和IM5的相位和幅度.采用这种预失真器的线性化技术能够有效的改善功率放大器的线性度,双音测试表明,在输出功率为41.4dBm时,IMD3 和IMD5 分别改善了19 dB 和14dB.     

反并联二极管实现预失真线性化器的电路设计

放大器的非线性失真特性严重影响信号的传输质量,射频预失真是一种有效改善行波管非线性度的方法。本文利用反并联肖特基二极管完成了X波段预失真线性化器的设计。仿真结果表明,在8.4GHz~8.6GHz频率范围和一定输入功率内,各个频点处增益扩张量保持在6dB左右,工作频带内增益平坦度在1dB以内,相位扩张基本保持在45°左右。     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Technology innovation and process integrations for sub-100nm gate patterning

This paper presents a brief overview of the Applied Centura(R)DPS(R)system,configured with silicon etch DPS Ⅱ chamber, with emphasis on discussing tuning capability for CD uniformity control. It also presents the studies of etch process chemistry and film integration impact for an overall successful gate patterning development. Discussions will focus on resolutions to key issues, such as CD uniformity, line-edge roughness, and multilayer film etching integration.     

White organic light-emitting devices based on fac tris（2- phenylpyridine） iridium sensitized 5,6,11,12-tetraphenylnap -hthacene

We have fabricated the white organic light-emitting devices （WOLEDs） based on 4,4＇ -bis（2,2 -diphenyl vinyl）-1,1＇ - biphenyl （DPVBi） and phosphorescence sensitized 5,6,11,12,-tetraphenylnaphthacene （rubrene）. The device structure is ITO/2T-NATA （20 nm）/NPBX （20 nm）/CBP： x%Ir（ppy）3：0.5% rubrene （8 nm）/NPBX （5 nm）/DPVBi （30 nm）/Alq（30 nm）/LiF（0.5 nm）/A1. In the devices, DPVBi acts as a blue light-emitting layer, the rubrene is sensitized by a phosphorescent material, fac tris （2-phenylpyridine） iridium [Ir（ppy）3], acts as a yellow light-emitting layer, and N,N＇ -bis- （1-naphthyl）- N,N＇ -diphenyl -1, 1＇ -biphenyl-4,4＇ -diamine （NPBX） acts as a hole transporting and exciton blocker layer, respectively. When the concentration of Ir （PPY）3 is 6wt%, the maximum luminance is 24960 cd/m^2 at an applied voltage of 15 V, and the maximum luminous efficiency is 5.17 cd/A at an applied voltage of 8 V.     

Complete approach to automatic identification and subpixel center location for ellipse feature

To meet the need of automatic image features extraction with high precision in visual inspection, a complete approach to automatic identification and sub-pixel center location for similar-ellipse feature is proposed. In the method, the feature area is identified automatically based on the edge attribute, and the sub-pixel center location is accomplished with the leastsquare algorithm. It shows that the method is valid, practical, and has high precision by experiment. Meanwhile this method can meet the need of instrumentation of visual inspection because of easy realization and without man-machine interaction.     

小角度扩展相关性近似算法分析

本论文提出一种在多天线MIMO信道相关性建模中小角度扩展近似理论算法,并应用于分析MIMO系统性能。分析中分别对三种不同角能量分布情况下的空间相关性研发快速近似计算法,并同时提出双模(Bi-Modal)角能量分布情况下的近似运算。通过分析这些新方法的近似效率,可以得到计算简单、复杂度低、而且符合实际的MIMO相关信道矩阵,对系统级的快速高效计算法的研究和系统级的评估以及误差分析具有重要的意义。     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.