蔡氏电路混沌信号频谱分布特征及其在电路设计中的应用

本文对蔡氏电路从Ｈｏｐｆ分叉变化到双蜗卷混沌过程中的输出信号频谱进行了计算机模拟，模拟表明混沌信号频谱分布具有一定的特征，本文给出了一个估计其频谱分布范围的简单公式，从该公式和蔡氏电路α－β分叉曲线出发可以设计输出信号基本满足预先指定的频谱分布范围的蔡氏电路。     

锁相鉴频器混沌现象的研究

该文研究无线电技术与现代通信领域广泛使用的锁相鉴频器中的混沌现象,利用Melnikov方法,证明了当输入信号参数、系统参数满足一定条件时,锁相鉴频器有混沌信号输出。通过电路实验,从频谱分析仪上观察到电路出现混沌时,压控振荡器输出端的连续频谱,进一步证实了锁相鉴频器电路中存在混沌现象。实验结果与理论分析相吻合,文中的结论对实际设计和应用锁相鉴频器,具有重要的指导意义。     

蔡氏混沌非线性电路及其频率特性研究

混沌电路是一种非线性电路，具有宽频谱特性，但在实际通信应用中，通信信道的带宽有一定限制，如何调节混沌电路的频谱范围成为混沌电路实际应用的一个问题。本文以蔡氏混沌电路为例，利用MATLAB软件分析蔡氏混沌电路产生的混沌信号及其频率特性。通过对蔡氏混沌电路中元器件R、L和C参数的调整，可以获得具有期望频谱范围的混沌信号。     

用于移动设备的视频驱动技术

如今,越来越多的移动设备带有视频输出端口。这些端口必须驱动符合显示标准的视频信号。例如,NTSC视频就是利用75Ω线路驱动的1V峰值信号。如果电路在电缆两端进行端接,那么来自视频驱动器输出端口的信号必须是2V。在许多情况下,视频ASIC(编码器)是基于低压平台的,采用1.8V甚至     

TDA8946J双通道立体声功率放大集成电路

TDA8946J是双声道立体声音频功率放大器。两路互补式BTL型推挽输出,其输出低阻抗与外接8Ω扬声器相匹配。当电源电压为18V时,最大输出功率2×15W;当工作电压为15.5V时,输出功率不小于2×10W。无需隔直流电容,故频域宽,低频成分丰富。四个输出端口,1、4、14 和17脚 均有Vcc/2的直流电压,四个(两对)音频输入端口,6、8, 12 、9,其输入阻抗均为45kΩ,端口的直流电平通过内部电路已达平衡,电压均为Vcc/2,因此适宜采用交流耦合形式输入,既可单端耦合也能双端对称输入,其实际应用电路如图1所示,每通道电压增益32dB。由内部电路框图可知:TDA8…     

电阻抗成像压控电流源的参数匹配设计

电压控制电流源的性能对电阻抗成像的效果影响很大,分析了由3个ICL7650S运算放大器构成的电压控制电流源电路,通过设置电路中匹配电阻的数值,使该压控电流源满足电阻抗成像系统的设计要求。仿真结果表明,该电压电流源的频率和幅值可调,在频率为10 k Hz~1 MHz范围内输出波形失真小,在信号频率为50 k Hz时输出阻抗可高达1.3 MΩ,信号频率小于150 k Hz时输出阻抗不小于100 kΩ,满足电阻抗成像系统要求。     

预设信号频谱蔡氏电路设计

首先简单介绍蔡氏电路的实现,分析其输出信号的频谱分布特征,利用估算的频谱分布公式,计算出电路中各元件参数,最终设计出上限频率为20kHz的低频蔡氏混沌振荡电路,电路仿真结果表明了设计的正确性。     

LM1875高性能价格比的音频功率放大器

LM1875音频功率放大器是单片音频功率放大器,在工作电源电压为±25V、负载阻抗为8Ω时,输出功率为20W。当电源电压为±30V、负载阻抗为8Ω时,输出功率可达30W。该电路具有外围元件少、调试简单、音频功率带宽较宽（可达70kHZ）、在大信号输出时失真小等特点,电路内部?..     

L波段高效率内匹配GaN HEMT

研究了一种基于国产SiC衬底的L波段GaN高效率内匹配器件。利用在片微波测试和直流测试相结合方法获得器件的小信号模型,外推得到大信号模型,并进行负载牵引方法验证。在此基础上设计两胞匹配电路,采用电感-电容匹配网络,器件阻抗提升到12Ω,利用改进型威尔金森功率分配器和功率合成器将阻抗由12Ω提升到50Ω,功率分配器和匹配电容使用高Q值陶瓷基片加工。研制的内匹配GaN HEMT器件在测试频率为1.20~1.32 GHz时,输出功率大于80 W,功率增益大于16.2 dB,最大功率附加效率达到72.1%。     

DC绝缘阻抗测试仪的设计与实现

针对电子电气等产品在生产过程中需进行DC绝缘阻抗测试的要求,设计并实现了一种基于Cortex-M3的DC绝缘阻抗测试仪。该测试仪以Cortex-M3作为核心控制器,配置DC高压产生电路、信号采集调理电路和LCD显示电路,从而达到对产品进行实时有效绝缘阻抗测试的目的。经实验证明,该测试仪能进行1 MΩ~10 GΩ的绝缘阻抗测量,且具有输出功率大、测量精度高等优点,可广泛应用于各类电子、电气等产品生产企业。     

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.