音频信号分析仪

以单片机和FPGA为核心的音频信号分析仪,利用傅里叶变换FFT法分析音频信号频谱.该分析仪主要由信号前级调理、有效值检波、采样保持等功能模块组成.频谱测量频率范围为20 Hz～10 kHz,频率分辨率达到5 Hz,幅度范围(峰-峰值)为10 μV～20V.系统设计控制简单,设计成本低,具有很高的实用价值.     

基于PWM的D类音频功率放大器的设计

系统旨在设计一种D类功率放大器,以高频三角波作为载波,对音频信号进行采样,生成PWM(Pulse Width Modulation)调制信号.采用高速开关管组成的互补对称式H桥电路对信号的功率进行放大,再将放大后的信号送入4阶Butterworth低通滤波器进行滤波,得到理想的音频信号.系统主要针对音频信号进行处理,对输入频率20 Hz～20kHz,振幅30～250 mV的音频信号可以实现很好的功率放大效果,最大不失真输出功率大于1W,最高效率可达到83％.还能对输入信号进行可调放大,实现信号输出功率可调.     

声音质量的评价

音质标准 所谓声音的质量,是指经传输、处理后音频信号的保真度。目前,业界公认的声音质量标准分为4级,即数字激光唱盘CD-DA质量,其信号带宽为10Hz～20kHz;调频广播FM质量,其信号带宽为20Hz～15kHz;调幅广播AM质量,其信号带宽为50Hz～7kHz;电话的话音质量,其信号带宽为200Hz～3400Hz。可见,数字激光唱盘的声音质量最高,电话的话音质量最低。除了频率范围外,人们     

音频信号分析仪设计

基于离散傅里叶变换原理,以单片机和可编程逻辑器件FPGA构成的最小系统为控制核心,由前级信号调理模块、抗混叠滤波模块、AD637检波模块、A／D采样模块等模块构成。采用数字信号处理技术．在FPGA内部完成了2048点的浮点型FFT计算,能准确判断频率成分在20Hz～10kHz、幅值范围在0．1mV-10V的输入信号的功率谱及其总功率,频率分辨力最高可达10Hz,并能分析正弦信号的失真度。系统对待测量5s刷新一次并可实时显示。另外还增加了掉电存储回放显示及信号频谱显示的功能。     

音频信号分析仪

以单片机和FPGA为核心的音频信号分析仪,利用傅里叶变换FFT法分析音频信号频谱。该分析仪主要由信号前级调理、有效值检波、采样保持等功能模块组成。频谱测量频率范围为20H加10kHz,频率分辨率达到5Hz。幅度范围（峰-峰值）为10μV-20V。系统设计控制简单,设计成本低,具有很高的实用价值。     

基于天底点的二相编码解调算法及实现

针对雷达高度表二相编码回波信号受多普勒和回波相位差双重调制问题,在深入分析雷达高度表回波信号模型及回波功率分布特征的基础上,提出了基于天底点的二相编码解调算法。该算法通过检测天底点回波中的多普勒和相位差信息,进行相应补偿从而实现码解调。仿真和实验表明:该算法多普勒频率检测误差小于20 Hz,相位检测误差小于2°,可有效实现码解调。     

K波段高稳光电振荡器

介绍了一种具有高稳定性、高谱纯度、低相位噪声的双环路光电振荡器(OEO)。理论上分析了光电振荡器的基本原理,采用光域双环路的方案有效地实现了边模抑制,通过检测输出信号频率的变化来控制光纤环路的长度,从而得到了高质量的20GHz微波信号,其频谱纯度高,线宽小于1Hz,相位噪声在10kHz时为-112dBc/Hz,而且在4h观测时间内,频率的稳定性小于10-10。     

基于MSP430的FM音频频谱分析仪设计与实现

频谱分析在教学科研和生产实践中都有着非常广泛的应用,显示的是信号频率和功率的关系,广泛应用于电子对抗、移动通信和广播电视等领域。调频广播的音频范围在30Hz～15KHz,音频质量的好坏影响了调频广播发射机整体的指标。因此有必要对调频广播的输入音频进行频谱分析,从而采用适当的措施来进行调整和改进。     

10.6μm天文外差光谱仪

本文报道一台以Cassegrain聚焦系统工作的天文外差光谱仪。工作波长是10μm,光谱分辨率λ/⊿在6×10~5～6×10~6。噪声等效功率接近理论极限1.88×10~(-20)W/Hz。阐述了在红外波段在外差接收条件下使噪声等效功率最佳化的方法,以及信噪比远小于工时信号检测的手段。文中还介绍了整个接收系统的光、电结构和一些实验数据。     

快速傅里叶变换算法在音频功放中的应用

文章基于TPA3112D1设计了一种带啸叫检测与抑制功能的音频功率放大器。利用快速傅立叶变换算法(FFT)、压控放大(VCA)、和滤波网络实现了对音频信号的放大和对啸叫的实时检测和抑制。实际测试结果表明：功放输出端的最大不失真功率为5W,输出功率在50mW~5W的范围内,其啸叫的频率响应在500Hz~10KHz的范围内;系统的整体误差小于10%,效率大于80%。     

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.     

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.     

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.     

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.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

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.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks