基于FFT的阵列方向图快速计算

分析了等距线阵方向图与傅立叶变换的一致性,用FFT算法进行阵列方向图快速计算。通过严格的数学推导,揭示变换序列与可见空间的关系,讨论了不同单元间距情况下的处理方法。文中结合实例,阐述了FFT算法在阵列方向图计算中的应用技巧,如扫描处理方法、指向分辨精度和边缘数据点估计,并指出用FFT算法计算阵列方向图其运算速度可提高一个数量级以上。     

干涉图空域延拓技术研究

现代干涉测试的核心是用合理的算法处理干涉图而获得所需的面形及参数。用二维FFT方法处理干涉图时,由于FFT算法只能处理数字化的离散数据,且要求数据分布区域必须是矩形区域,因此必须设法将圆形区域干涉图扩展延拓成矩形区域。在研究二维FFT法进行干涉测试基本原理的基础上,提出了一种干涉图空域迭代延拓的原理和方法,利用该方法对一幅实际干涉图进行空域延拓,取得了满意的延拓效果。结果表明,该方法具有较高的处理精度,为波面相位复原奠定了基础。     

基于迭代FFT算法的平面阵列交错稀疏布阵方法

交错稀疏阵列天线的设计需要实现“稀疏布阵”和“子阵交错机制”两个关键技术的有机“协同”.提出一种基于改进迭代快速傅里叶变换(Fast Fourier Transformation, FFT)算法的均匀面阵交错稀疏布阵机制.鉴于均匀矩形平面阵列天线激励与方向图存在二维傅里叶变换的关系, 该方法通过对均匀面阵方向图采样的频谱能量分析, 采用交错选取子阵激励的方法, 实现了面阵天线方向图频谱能量的均匀分配, 获得了近似相同方向图的交错子阵设计.在此基础上, 采用迭代FFT算法对交错子阵激励进行迭代循环, 有效降低了交错子阵的峰值旁瓣电平.理论分析与实验仿真证明, 相对于基于循环差集和互补差集的稀疏交错优化方法, 该算法实现的交错稀疏阵列设计具有方向图近似程度更高, 且峰值旁瓣电平更低的优点.     

子阵级平面相控阵ADBF的旁瓣抑制方法

研究子阵级平面相控阵ADBF自适应方向图的旁瓣抑制方法.给出了二维子阵级ADBF的信号模型,适用于任意的平面相控阵.分析了常规的二维子阵级ADBF方法,引入了基于子空间投影的二维子阵级ADBF.研究了常规方法和基于子空间投影方法的结合方法,提高了对自适应方向图进行旁瓣抑制的灵活性,有效地降低了输出SINR损失;可在较好地进行旁瓣抑制的同时,得到与最优波束形成器非常接近的输出SINR.仿真结果证明了所提出方法的有效性.     

平面相控阵天线波束控制技术

以平面相控阵天线为研究对象,在给出阵面天线方向图函数模型的基础上,详细描述了波控码的计算方法;分析了波束控制的系统架构,提出了查表法与分布式计算相结合的波控码计算方法,阐述了其软件处理流程,并与传统方法对比分析了该方法的技术优势。通过对阵面天线方向图的仿真分析,该方法可以控制波束指向,实现一维扫描与二维扫描、单向扫描与全向扫描,并具有很好的控制精确度。对波控系统的设计可以推广到其他阵列天线模型上。     

超长可变点数FFT处理器设计与实现

介绍了超长可变点数序列FFT处理器的实现方法。采取将一维大点数FFT转换为二维小点数子FFT处理的措施,减小了存储器规模。使用乒乓RAM将基本运算模块级联,形成流水线结构,可连续高速计算N点复数序列FFT/IFFT。用现场可编程门阵列(FPGA)实现了可计算1k~1M点序列长度可变的FFT/IFFT处理器。     

一种基于波束-频域处理的自适应波束形成方法

在天波超视距雷达中 ,通道之间的频响不一致影响了自适应波束形成的性能。去斜处理使得不同距离对应于不同频率 ,故不同距离单元的幅相不一致性与不同的频率相对应。经距离维FFT处理后 ,各路之间的通道不一致性得到降低 ,带内起伏趋于固定。基于上述特性 ,本文提出一种波束 频域处理方法 ,该方法不仅有效对消干扰 ,同时不会恶化天线方向图。更重要的是该方法降低了处理维数 ,减少了计算的复杂度。     

采用FFT-PSO策略的多约束稀疏阵天线方向图综合

采用稀疏布阵的相控阵测控天线,阵元等幅激励时的阵列峰值副瓣电平无法满足指标要求.在考虑天线增益、半功率波束宽度等指标约束时设计了合适的适应度函数,并基于粒子群算法(PSO)对阵元激励幅度进行优化以降低天线副瓣电平.同时,分析了等间距栅格平面阵列天线方向图与离散傅里叶变换的关系,采用快速傅里叶变换(FFT)降低了阵列方向图计算复杂度.仿真结果表明,该方法可有效降低峰值副瓣电平和计算复杂度.     

一种高精度的大点数二维FFT处理器设计

基于传统的频域抽取快速傅里叶变换(FFT)算法以及二维FFT算法,设计了一种高精度的大点数FFT处理器。该处理单元采用一个状态机控制整个运算流程,针对小点数情况的一维FFT算法和大点数情况的二维FFT算法,该处理器都可以智能地选择合适的处理流程和缓存管理,自动地完成整个FFT运算而无需软件介入。在支持大点数的二维FFT算法的基础上,该设计还通过对旋转因子计算过程的优化,以提高在大点数情况下的精度表现,在4M长度的输入序列时可以获得130 dB以上的信噪比。     

旋转体天线罩远场方向图的快速计算

介绍了一种用矩量法分析旋转体天线罩问题中远场方向图的快速计算方法.利用旋转体天线罩结构上的特性,可以对天线罩上的场及等效电磁流进行模式分解,将二维问题转化为若干一维问题,这样求解得到的等效电流和磁流分布是以模式叠加的形式表示的.在求解远场方向图时,可以利用每个模式沿罩面环向的分布特性及天线罩的结构特性,通过解析的方法来处理方位角积分,从而可以快速计算远场方向图.     

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.     

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.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

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正Communications—VLSI Researches and industries of telecommunications have been growing rapidly in the last 20 years and will keep their high growing pace in the next decade.The involved researches and developments cover mobile communications,highway and last-mile broadband communication,domain specific communications,and emerging D2D M2M communications.Radio communication steps into its