基于ISCP-DPSK调制的直接序列扩频技术

使用符号内连续相位差分相移键控(ISCP-DPSK)调制的直接序列扩频方法可以在实现扩频抗干扰的同时保留ISCP-DPSK调制信号的准恒包络特性和优良的频谱特性,有利于非线性和功率受限的应用场合。由于采用非相干的信号解扩解调方法,避免了低信噪比下的载波和相位估计与跟踪,简化了系统设计。计算机仿真表明,基于ISCP-DPSK调制的直接序列扩频能有效对抗本振偏离、多普勒频移等引起的符号间相位变化影响,8倍扩频和16倍扩频的增益仅与理论值分别相差0.1 dB和0.2 dB。     

基于PMF-FFT的扩频信号多通道并行捕获

目前在扩频测控通信系统中越来越多地采用了部分匹配滤波和快速傅里叶变换（PMF-FFT）的方法来实现扩频信号的捕获,这里分析了PMF-FFT实现扩频信号捕获的算法原理、过程和性能,充分利用多通道并行处理架构,提出了基于PMF-FFT的频域（频率分槽）多通道并行捕获和时域（伪码分区）多通道并行捕获两种不同的实现方法,以满足不同的扩频测控通信系统对伪码捕获性能的应用需求。     

FH/PSK混合调制扩频信号参数估计

针对混合调制信号参数难以估计的问题,本文通过对FH/PSK混合调制扩频信号特征的分析,提出了一种FH/PSK混合调制扩频信号参数估计方法。利用时频脊线分析、跳频分量数估计、快速四阶循环累积量算法与小波变换相结合的方法,实现了跳频频率和码速率等参数的高精度估计。仿真表明,本文方法可在较低信噪比下得到该混合调制扩频信号多个参数的高精度估计,具有较高的工程应用价值。     

一种新的多通道扩频接收机中频噪声模拟算法

该文提出了一种新的多通道直接序列扩频接收机中频回波噪声模拟算法。该算法将通道间扩频信号互相关的影响等效为噪声叠加,由此提出了一种新的适用于多通道直接序列扩频信号合成并保证输出功率恒定的比例因子计算方法,并将该方法成功应用于某多通道直接序列扩频接收机的中频回波噪声模拟中。实验结果表明利用该方法产生的中频信号信噪比模拟精度远优于传统的实现方法。     

基于脉冲压缩与载波恢复的直接扩频信号相位差提取方法研究

相位差测量技术是相位干涉测向系统的关键技术之一,相位差的测量精度直接影响系统的测向精度。为解决某相位干涉测向系统中直接扩频信号相位差的提取问题,本文对脉冲压缩与载波恢复两种相位差提取方法的原理进行了分析,通过Matlab对不同信噪比和多普勒条件下两种方法的相位差提取精度进行了仿真。     

多通道实时数字鉴相技术的FPGA实现

数字式干涉仪测向体制中的相位差信息在频域上提取,与传统的在时域提取相比能大大提高低信噪比条件下鉴相精度及对信号的适应能力。利用相位差信息的频域数字提取方法,实现了单片FPGA完成多通道相位信息的提取。与传统的计算机实现和DSP实现相比,不但提高了速度,而且设备量小,具有明显的优势。     

基于频率掩盖模型的自适应音频水印算法

提出了一种基于音频信号掩蔽曲线的水印嵌入方法.该方法根据扩频理论,将水印序列扩频调制后,结合音频信号的掩蔽阈值,自适应地修改音频信号的功率谱,从而达到嵌入水印的目的.给出了一种基于相关性检测误码率的水印提取和决策方法.实验结果表明,在不影响听觉效果的前提下,这种水印嵌入和检测方法对MPEG压缩、常规滤波、加噪等处理均具有很好的抗攻击性.     

基于TMS320C6678的多个同时到达信号脉内调制类型识别

针对雷达信号脉内调制中的5类信号,提出了一种基于改进相位差分的脉内调制类型识别方法.首先,对信号进行滤波处理,并快速识别出单频脉冲;然后,对滤波后的信号相位差分得到瞬时频率,将瞬时频率等分成两段并利用最小二乘法线性拟合,提取两个参数识别出线性调频和双线性调频;其次,对去跳变后的瞬时频率再利用最小二乘线性拟合提取斜率参数识别出复合信号,对剩下的信号平方后计算3 dB带宽内谱线数是否唯一识别出二相编码信号.最后,基于TMS320C6678实现了5类共7个同时到达信号的调制类型识别.仿真分析表明,当信噪比高于0 dB时,5类信号的识别概率优于90％,硬件实验表明,7个同时到达信号的调制类型识别处理时间在87μs以内.     

调制相位差对TDLAS信噪比的影响

用可调谐二极管激光吸收光谱技术检测气体时,不同的调制相位差结果不同。为了提高谐波检测灵敏度,采用同时考虑频率调制与振幅调制的方法分析和提取二次谐波信号,推导了相位差与二次谐波信号光电流和残余幅度调制噪声光电流的函数关系表达式,通过模拟实验分别取得了二次谐波信号和残余幅度调制噪声随相位差的变化趋势,并重点分析了相位差对信噪比的影响。结果表明,振幅调整和频率调制之间的相位差对信噪比的影响很大,与典型值/2时相比,最大降幅为59.18%;调制相位差是继残余幅度调制之外,影响信噪比的一个重要因素。     

JTIDS系统的低复杂度多进制扩频检测方法

传统多进制扩频调制使用多个相关器进行检测,每个相关器产生一个相关值,实现复杂.提出了一种使用FIR滤波器的基于扩频码段分路和延时相加的实用多进制扩频检测方法,通过FIR滤波即可产生所有相关值,实现结构简单,特别适合在使用周期移位伪随机序列的联合战术信息分发系统(JTIDS)中应用,可有效降低JTIDS系统中多进制扩频信号的检测复杂度和工程实现难度.仿真比较了优选扩频序列和Walsh正交码集的误比特率性能,获得了良好的性能结果.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

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.     

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.     

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.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.