Nakagami衰落信道上组合SC/MRC的性能分析

研究Nakagami衰落信道上组合发射机选择合并(SC)/接收机最大比合并(MRC)天线分集系统的性能.使用矩生成函数方法,推导采用组合SC/MRC天线分集和相干检测的MPSK(M进制相移键控)、MQAM(M进制正交幅度调制)、MPAM(M进制脉冲幅度调制)、BFSK(二进制频移键控)、最小相关BFSK(BFSKmin)、差分编码BPSK(DE-BPSK)和预编码MSK(最小频移键控)等几种M进制数字调制方式在Nakagami衰落信道上的误符号率性能,获得了M进制数字调制系统误符号率性能的精确数学表达式.数值计算结果阐明了发射天线和接收天线数目以及衰落参数对数字调制系统误符号率性能的影响.     

Hepta-Band Internal Antenna for Personal Communication Handsets

Modern personal communication handsets are shrinking in size and are required to operate at multiple frequency bands for enhanced functionality and performance. This poses an important challenge for antenna designers to build multiband antennas within the limited allowable space. In this paper, an internal antenna covering seven frequency bands is presented for personal communication handsets. The proposed antenna operates at GSM (880-960 MHz), DCS (1710-1880 MHz), PCS (1880-1990 MHz), UMTS (1900-2170 MHz), WiBro (2300-2390 MHz), Bluetooth (2.4-2.48 GHz), and WLAN (5.0-5.5 GHz) frequency bands. Measured input return loss of the antenna is better than dB at all the frequency bands with reasonable radiation performance. Antenna volume is 30 mm times15 mm times 4.0 mm (1.8 cm) that makes it attractive for modern multiband and multifunctional slim handsets.     

共溅射钨硅化合物真空快速热退火行为(英文)

The behavior of co-sputtering tungsten silicide after vacuum rapid annealing at 1000-1100℃ for 15s is investigated by Raman scattering, scanning electron microscope, X-ray diffraction, Auger electron spectrum and resistivity measurements. There are two Raman peaks at 331 and 450cm-1, and their intensities increase with the temperature rise of rapid thermal annealing. Scanning electron micrograph exhibits crystallization at 1000℃ and its enhancement with increase of annealing temperature. In addition to the (002), (101), (110), (103), (112) and (200) diffraction peaks of WSi2, there are some W5Si3 peaks in X-ray diffraction pattern. However, the composition of WSi2 is found in Auger electron spectrum at 1000℃, and the measurement results of sheet resistance also conclude WSi2 characteristics.     

CDF and MGF based analysis over Rayleigh TWDP shadowed fading channel for indoor communication

Recently, the two-wave with diffuse power (TWDP) distribution has been extensively used to model the shadowing in multipath-faded/shadowed indoor environment. In this article, novel expressions for joint moments, mean, second moment, variance and cumulative distribution function for Rayleigh TWDP shadowed fading model are derived. By using the derived expression of mean and variance, the expression for amount of fading is obtained. Also, the outage probability, moment generating function and average bit error rate (ABER) for various modulation schemes namely binary phase shift keying (BPSK), binary frequency shift keying (BFSK), minimum shift keying (MSK), differentially coherent phase shift keying (DCPSK) and non-coherent frequency shift keying (NCFSK) are calculated. The derived expressions for cumulative distribution function, outage probability and ABER are presented in analytical format and have been numerically evaluated. Moreover, the numerical results of ABER using MSK and DPSK modulation schemes is compare with results of Rayleigh Gamma composite fading model. The study shows that better outage probability (0.01) is observed at 40dB average signal to noise ratio (SNR) with 5dB lowest threshold SNR, however, at higher threshold SNR (>5dB) with fixed average SNR (40dB), poor outage probability performance are obtained. Further, at higher shadowing (10dB), for fixed average SNR (15dB), minimum error probability (10^?4) is observe, while at lower shadowing (less than 10dB), higher error probability (greater than 10^?4) is observed that represents poor BER performance.     

紫外线诱变DNA 的发射光谱研究

利用光栅摄谱仪获取脱氧核糖核酸(DNA)在紫外线诱变前后的光谱分布。实验结果表明：经过紫外线诱变以后，分别反应脱氧核糖磷酸盐链振动和C—O伸缩振动的谱线884cm^-1、1010cm^-1、1068cm^-1都有不同程度的减弱；属于脱氧核糖在1468cm^-1处的谱线消失。碱基中：属于胸腺嘧啶(T)的652cm^-1线消失；出现归属于T的新的谱线670cm^-1；属于腺嘌呤(A)的1304cm^-1线增强；属于鸟嘌呤(G)和胞嘧啶(C)的1526cm^-1线减弱。     

纳米晶ZnO:Dy3+粉体的制备和发光性质

通过固相反应法制备了ZnO:Dy3+纳米粉末,样品的X射线衍射、透射电镜和选区电子衍射证实了ZnO:Dy3+纳米粉末属于六方纤锌矿多晶结构.研究了光致发光谱与激发波长和掺杂离子浓度的依赖关系.结果表明,从ZnO:Dy3+纳米粉末的光致发光光谱中首次发现除了Dy3+的4f→4f跃迁外,出现了Dy掺入ZnO后产生的两个缺陷A和B的宽谱带发射峰,峰值分别在600和760nm,半高宽分别约为200和100nm.在ZnO的激子激发下(385nm),峰值760nm的发光强度远远大于峰值在600nm的发光强度.样品的发射光谱中峰值的相对强度变化依赖于激发波长和Dy3+的掺杂浓度.当在Dy3+4f→4f激发下(454nm),光谱中只有Dy3+的4f态间的特征发射,而缺陷A,B不发光.     

电子显微镜的现状与展望

本文扼要介绍了电子显微镜的现状与展望，透射电子显微镜方面主要有：高分辨电子显微学及原子像的观察，像差校正电子显微镜，原子尺度电子全息学，表面的高分辨电子显微正面成像，超高压电子显微镜，中等电压电镜，１２０ｋＶ，１００ｋＶ分析电镜，场发射枪扫描透射电镜及能量选择电镜等，透射电镜将又一次面临新的重大突破，扫描电子显微镜方面主要有：分析扫描电镜和Ｘ射线能谱仪，Ｘ射线波谱仪和电子探针仪，场发射枪扫描电镜和     

纳米ZnO光学性质研究进展

介绍了纳米ZnO常见发光谱的发光机制。在室温光致发光谱(PL)中,一般在380 nm处出现紫外发光,也有报道在357和377 nm处的紫外发光,列举了几种不同的发光解释。对于深能级发光,一般在400～550 nm出现连续的发光带,也有观察到深能级的声子伴线和声子复制现象。在低温光致发光谱的紫外发射中,一般观察到由自由激子发射(FX)、中性施主束缚激子发射(D0X)、施主-受主对跃迁峰(DAP)、中性施主束缚激子对应的双电子卫星峰(TES)以及声子伴线。综述了纳米ZnO的喇曼光谱、透射光谱、电致发光谱(EL)的特征,最后展望了纳米ZnO的光学性能研究前景。     

Synthesis and photoluminescence properties of Mn-doped ZnS nanobelts

Mn-doped ZnS nanobelts have been prepared through a thermal evaporation method at 1100℃. The synthesized nanobelts are characterized with X-ray diffraction （XRD）, scanning electron microscopy （SEM）, selected area electron diffraction （SAED）, high-resolution transmission electron microscopy （HRTEM）, and photoluminescence （PL） spectroscopy. The results show that the nanobelts have an uniform single-crystal hexagonal wurtzite structure and grow along [0001 ] direction. Room-temperature photoluminescence reveals that the intrinsic PL of the nanobelts disappears and a new PL peak of the Mn-doped ZnS nanobelts emerges at 575 nm.     

An Efficient Chemical Solution Deposition Method for Epitaxial Gallium Nitride Layers Using a Single‐Molecule Precursor

An efficient chemical solution deposition (CSD) approach to growing epitaxial GaN layers at relatively low temperatures using a single‐molecule precursor (SMP) is described. The precursor employed was bisazido diethylaminopropyl gallium, which exists as a dimer in the solid state and decomposes at relatively low temperatures. Using this precursor, epitaxial GaN layers were grown and characterized for their morphology, microstructure, and composition by X‐ray diffraction (XRD), X‐ray rocking curve (XRC) analysis, pole figure measurements, reciprocal space mappings, scanning electron microscopy (SEM), Rutherford backscattering (RBS), X‐ray photoelectron spectroscopy (XPS), and room temperature photoluminescence (PL) measurements.     

Lattice parameter determination of mullite by energy-filtered needle-texture electron diffraction pattern

The thermal transformations of pyrophyllite to mullite by heating were re-examined using mainly energy-filtering transmission electron microscopy and, for the first time, the texture electron diffraction pattern of the mullite was completely interpreted. Through a temperature range in which pyrophyllite dehydroxylate maintained a long-range order with a fluctuation of approximately 1% in d-spacings of (100) and (010) planes at 1000 degrees C, without prominent exothermic feature, pyrophyllite dehydroxylate was gradually decomposed and transformed into mullite through topotaxy. Pyrophyllite dehydroxylate did not collapse completely until 1100 degrees C, which promoted the rapid growth of mullite in random orientation at 1200 degrees C and the crystallization of amorphous silica to cristobalite at 1300 degrees C. The mullite needles, having their c-axis (texture axis) parallel to the elongation direction, lined up along the b(*)-axis of the pyrophyllite dehydroxylate in the needle-texture electron diffraction patterns. The mullite needles had monoclinic symmetry with lattice parameters of 7.27 A (a), 7.75 A (b), 2.90 A (c), 90 degrees (alpha), 90 degrees (beta) and 88.41 degrees (gamma), which, because of the structural affiliation to the parent pyrophyllite dehydroxylate, differ to the orthorhombic 3/2-mullite.     

Cathodoluminescence investigation of silicon nanowires fabricated by thermal evaporation of SiO

Silicon nanowire samples fabricated by thermal evaporation of SiO powder were investigated by Cathodoluminescence. Three main bands were found at low temperatures, namely, peak 1 at about 620–650 nm (2.0–1.91 eV), peak 2 at 920 nm (1.35 eV), and peak 3 at 1280 nm (0.97 eV). An additional broad band (peak 4) in the infrared region with its maximum at ∼1570 nm (0.79 eV) appears at room temperature. The origins of the emission bands are discussed. The text was submitted by the authors in English.     

相关衰落信道上MIMO系统中组合SC/MRC的性能分析

研究相关瑞利衰落信道上MIMO系统中组合发射机选择合并(SC)/接收机最大比合并(MRC)的天线分集系统性能.使用矩生成函数方法,推导相关瑞利衰落信道上采用组合SC/MRC天线分集争相干检测的M进制相移键控(MPSK),M进制正交幅度调制(MQAM),M进制脉冲幅度调制(MPAM)等几种M进制数字调制方式的误符号率精确表达式.数值计算结果阐明相关性和天线阵结构对采用组合SC/MRC天线分集的几种M进制数字调制方式的平均误符号率性能的影响.     

New UV and IR transitions in gold, copper, and cadmium hollow cathode lasers

We have observed four additional ion laser transitions in gold, copper, and cadmium hollow cathode discharges. The new lines are at 2264 Å (Au II), 2722 Å (Cu II), 8599 Å (Au II), and 8652 Å (Cd II).     

Impact of underlap spacer region variation on electrostatic and analog performance of symmetrical high-k SOI FinFET at 20 nm channel length

Continued scaling of CMOS technology to achieve high performance and low power consumption of semiconductor devices in the complex integrated circuits faces the degradation in terms of electrostatic integrity,short channel effects (SCEs),leakage currents,device variability and reliability etc.Nowadays,multigate structure has become the promising candidate to overcome these problems.SOI FinFET is one of the best multigate structures that has gained importance in all electronic design automation (EDA) industries due to its improved short channel effects (SCEs),because of its more effective gate-controlling capabilities.In this paper,our aim is to explore the sensitivity of underlap spacer region variation on the performance of SOI FinFET at 20 nm channel length.Electric field modulation is analyzed with spacer length variation and electrostatic performance is evaluated in terms of performance parameter like electron mobility,electric field,electric potential,sub-threshold slope (SS),ON current (Ion),OFF current (Ioff) and Ion/Ioff ratio.The potential benefits of SOI FinFET at drain-to-source voltage,VDS =0.05 V and VDS =0.7 V towards analog and RF design is also evaluated in terms of intrinsic gain (Av),output conductance (gd),trans-conductance (gm),gate capacitance (Cgg),and cut-off frequency (fT =gm/2πCgg) with spacer region variations.     

兴隆大气视宁度测量

本文报导了在北京天文台兴隆观测站分别用校差图像运动（DIMM）、星像亮度半峰值全宽度（FWHM）、温度脉动探空（TFS）、声雷达四种不同的测量方法对当地的大气视宁度进行观测的结果。观测资料证明，这几种方法之间有很好的相关性，而且DIMM与TFS之间在定量上也很符合。     

Gigabit-per-second cryogenic optical link using optimizedlow-temperature AlGaAs-GaAs vertical-cavity surface-emitting lasers

We describe the design of GaAs-AlGaAs vertical-cavity surface-emitting lasers (VCSELs) that are optimized for operation at very low temperatures and the experimental demonstration of a free-space optical interconnect for cryogenic electronic systems using a VCSEL. We demonstrate high-speed modulation of the optical link at a data rate of up to 2 Gb/s at 77 K, with a very low bit-error rate of <10^-13 , and thermally stable operation is achieved over a wide range of cryogenic temperatures without laser bias current compensation. Cryogenic VCSELs with excellent lasing characteristics have been achieved over the entire temperature range from 150 K to 6 K, including high output power (22 mW), high power-conversion efficiency (32%), high slope efficiency (~100%), low threshold voltage (1.75 V) and current (1.7 mA), as well as a high-modulation bandwidth (12 GHz) for a 16 μm diameter device at 80 K     

Digital characteristics of a CMOS ternary inverter at the liquid nitrogen temperature

Static and dynamic performance of a CMOS ternary inverter has been studied in the MOSFET's threshold voltage region at the liquid nitrogen temperature (77K), and compared with the corresponding room temperature (296K) operation. It is observed that the positive ternary inverter (PTI), simple ternary inverter (STI) and negative ternary inverter (NTI) exhibit sharper voltage transfer characteristics and improved transient response at the liquid nitrogen temperature.     

Design and performance of free-space concave grating demultiplexersfor ultrawideband WDM networks

The design methodology and the simulated performance in terms of coupling efficiency and crosstalk for three different types of demultiplexers, constructed by means of holographic concave gratings, are presented. In-plane and out-of-plane geometries are discussed and a parameter sensitivity (tolerance) analysis is presented. These devices are tailor made for three different network types: access (1000 wavelength channels at 2.5 Gb/s), metropolitan (500 wavelength channels at 10 Gb/s), and core (80 wavelength channels at 80 Gb/s). The simulated performance reveals that these devices could play a key role in future multiterabit networks     

混合激励线性预测低速率语音编码研究

为了满足数字通信及其他商业应用的需求,语音压缩编码技术得到迅速发展。近年来主流的低速率语音编码方案主要基于LPC-10,混合激励线性预测（MELP）,多带激励编码（MBE）,正弦变换编码（SCI）,波形内插编码（WI）。大多都工作在2．4kb／s速率下。作为一种重要的低速率语音编码算法。MELP算法对LPC-10编码方案进行大量改进,引入混合激励,非周期脉冲,残差付氏幅度谱,脉冲散布和自适应谱滤波5个特征。实验结果表明,该混合激励线性预测编码在2．4kb／s上得到了更好的合成语音,并使得合成语音能更好地拟合自然语音。