对海监视雷达杂波的建模及仿真

杂波是雷达回波信号的重要组成部分,研究中常用幅度概率分布模型和相关谱型来描述。采用零记忆非线性变换法(ZMNL)进行建模设计,生成同时满足幅度分布条件和相关特性的随机序列,并将模拟杂波数据的概率密度和功率谱与理论曲线对比,进一步验证 ZMNL 法杂波建模的有效性和准确性。最后针对海航大学对海探测的雷达回波实测数据,进行海杂波和云雨杂波回波的幅度概率分布和功率谱的分析。     

基于ZMNL的雷达杂波仿真研究

杂波在雷达环境模拟中具有重要地位,文章利用零记忆非线性变换法(ZMNL),合理地设计了成形滤波器,对幅度和功率谱都服从一定分布的雷达杂波信号进行了仿真,并给出了有价值的仿真结果。     

雷达相关杂波的建模与仿真研究

为了研究杂波环境下的信号处理问题,需要对雷达杂波环境进行建模与仿真。文中归纳了雷达杂波的统计模型,包括幅度分布和功率谱模型,以及杂波的相应类型,并对服从一定幅度分布和功率谱分布的相关杂波序列产生方法进行了分析,给出了每种统计模型的仿真过程,最后根据杂波仿真的两种主要方法——无记忆非线性变换法ZMNL和球不变随机过程法SIRP对相关杂波进行了仿真,解决了仿真过程中成型滤波器的设计和特殊函数求值问题。仿真结果表明,用文中所述方法进行仿真可得到较好的结果。     

基于DSP的雷达杂波模拟实现

从雷达杂波的分布特性出发,分析了低分辨率雷达杂波的幅度统计特性和功率谱特性,并依据其分布特性对低分辨率雷达杂波模型进行了建立,同时为了降低杂波仿真计算量,采用频率变换法给出了杂波模拟的具体算法及仿真结果。最后结合某型以ADSP-BF533为核心处理芯片的雷达模拟器,进行了相应的软件设计,实现了高斯瑞利谱杂波回波输出。仿真结果表明,杂波模拟实时性较好,能够满足一般MTI、MTD体制雷达的测试和检测需求。     

FSK/PSK雷达杂波的建模与仿真

本文基于常规脉冲雷达杂波的产生原理,分析了FSK/PSK信号的特性,并对FSK/PSK雷达杂波模型进行了研究.用零记忆非线性(ZMNL)法,仿真出雷达杂波回波信号,并对其进行概率密度特性、功率谱特性和空间相关特性分析.由于子脉冲回波的叠加效应,FSK/PSK雷达杂波的统计特性与常规脉冲雷达杂波有所不同.     

FSK/PSK雷达杂波的建模与仿真

本文基于常规脉冲雷达杂波的产生原理,分析了FSK/PSK信号的特性,并对FSK/PSK雷达杂波模型进行了研究.用零记忆非线性(ZMNL)法,仿真出雷达杂波回波信号,并对其进行概率密度特性、功率谱特性和空间相关特性分析.由于子脉冲回波的叠加效应,FSK/PSK雷达杂波的统计特性与常规脉冲雷达杂波有所不同.     

基于MATLAB的雷达杂波建模与仿真研究

为评估杂波对雷达探测目标的影响,方便后续设计雷达探测算法,对雷达杂波信号特性进行研究。从杂波幅度分布模型、杂波功率谱模型、杂波仿真方法三个角度做了深入论述,并采用高斯杂波功率谱模型。通过MATLAB Simulink对威布尔分布、对数-正态分布以及K分布的幅度分布和数据序列进行仿真实验;实验结果与理论分析基本一致,证明了杂波模型的准确性,为雷达探测目标和抑制杂波干扰的设计提供参考依据。     

雷达杂波基带调制数据的数学产生方法

从雷达杂波的分布特性出发，分析了杂波的解析模型，阐述了雷达杂波幅度的概率密度分布及其功率谱密度分布。利用MATLAB软件，用数学计算的方法生成了幅度服从正态分布、对数正态分布，功率谱服从高斯谱分布、全极点谱分布的I，Q杂波基带调制数据，并用MATLAB进行了仿真。用该种方法生成的杂波基带调制数据已成功地用于某型雷达杂波模拟器。     

相参相关雷达杂波的建模与仿真

ZMNL法和SIRP法是目前最常用的两种杂波模拟方法，文中对这两种方法分别作了简要的介绍，并且详细讨论了基于以上两种方法的Rayleigh，Log Normal，Weibull分布和K分布杂波的产生原理和仿真流程。随后用ZMNL法对高斯谱Rayleigh分布和Log Normal分布杂波进行了仿真，同时分别用ZMNL法和SIRP法对基于相参脉冲雷达杂波模型的Weibull分布杂波和K分布杂波也作了仿真。最后，对所产生的杂波作了功率谱估计。实验结果证明，以上两种方法是有效可靠的。     

双基地前向散射雷达杂波分析与模拟方法北大核心CSCD

雷达杂波的统计特性研究与仿真模拟对雷达系统的设计、仿真、开发有重要意义。文中通过对前向散射雷达地表植被杂波实测数据的处理,观察到前向散射雷达杂波的幅度分布特性可根据风速和动态范围的不同分别采用K分布和对数正态分布拟合;同时杂波数据的谱分析结果表明可以采用全极点模型对前向散射雷达杂波建模。基于对杂波统计特性的分析,文中给出了一种SIRP法和ZMNL法相结合的前向散射雷达杂波模拟方法,模拟得到的杂波与实测杂波数据在统计特性上相一致,证实了模拟方法的有效性。     

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