Digital Coarse Tuning Loop for Wide-Band Fast-Settling Dual-Loop Frequency Synthesizers

A new coarse tuning loop for a wide-band dual-loop frequency synthesizer is presented. The coarse tuning structure is composed of two digital modules, including a successive approximation register and a frequency comparator with a novel structure. The frequency comparator counts the prescaler cycles within a certain reference time and compares the number with preset data to estimate the VCO frequency. The frequency comparison error is analyzed in detail. Within a given coarse tuning time,our proposed structure shows a comparison error 20 times smaller than that of other reported structures. This structure also reuses the programmable divider as a part of the coarse tuning loop so that the circuit is greatly simplified.

Effect of Y_2O_3 Content on Microstructure of Gradient Bioceramic Composite Coating Produced by Wide-Band Laser Cladding

To eliminate thermal stress and cracks in the process of laser cladding, a kind of bioceramic coating with gradient compositional design was prepared on the surface of Ti alloy by using wide-band laser cladding. And effect of Y2O3 content on gradient bioceramic composite coating was studied. The experimental results indicate that adding rare earth can refine grain. Different rare earth contents affect formation of HA and β-TCP in bioceramic coating. When the content of rare earth ranges from 0.4% to 0.6%, the active extent of rare earth in synthesizing HA and β-TCP is the best, which indicates that “monosodium glutamate” effect of rare earth plays a dominant role. However, when rare earth content is up to 0.8%, the amount of synthesizing HA and β-TCP in coating conversely goes down, which demonstrates that rare earth gradually losts its catalysis in manufacturing HA and β-TCP.

STOCHASTIC OPTIMAL CONTROL OF STRONGLY NONLINEAR SYSTEMS UNDER WIDE-BAND RANDOM EXCITATION WITH ACTUATOR SATURATION

A bounded optimal control strategy for strongly non-linear systems under non-white wide-band random excitation with actuator saturation is proposed. First, the stochastic averaging method is introduced for controlled strongly non-linear systems under wide-band random excitation using generalized harmonic functions. Then, the dynamical programming equation for the saturated control problem is formulated from the partially averaged Itō equation based on the dynamical programming principle. The optimal control consisting of the unbounded optimal control and the bounded bang-bang control is determined by solving the dynamical programming equation. Finally, the response of the optimally controlled system is predicted by solving the reduced Fokker-Planck-Kolmogorov （FPK） equation associated with the completed averaged Itō equation. An example is given to illustrate the proposed control strategy. Numerical results show that the proposed control strategy has high control effectiveness and efficiency and the chattering is reduced significantly comparing with the bang-bang control strategy.

An ultrathin wide-band planar metamaterial absorber based on a fractal frequency selective surface and resistive film

We propose an ultrathin wide-band metamaterial absorber （MA） based on a Minkowski （MIK） fractal frequency selective surface and resistive film. This absorber consists of a periodic arrangement of dielectric substrates sandwiched with an MIK fractal loop structure electric resonator and a resistive film. The finite element method is used to simulate and analyze the absorption of the MA. Compared with the MA-backed copper film, the designed MA-backed resistive film exhibits an absorption of 90% at a frequency region of 2 GHz-20 GHz. The power loss density distribution of the MA is further illustrated to explain the mechanism of the proposed MA. Simulated absorptions at different incidence cases indicate that this absorber is polarization-insensitive and wide-angled. Finally, further simulated results indicate that the surface resistance of the resistive film and the dielectric constant of the substrate can affect the absorbing property of the MA. This absorber may be used in many military fields.

Wide-Band Multi-spectral Space for Color Representation

This paper develops a wide-band multi-spectral space for color representationwith Aitken PCA algorithm. This novel mathematical space using the broad-band spectra matchingmethod aims at improving the accuracy of color representation as well as reducing costs forprocessing and storing multi-spectral images. The results show that the space can present ourexperimental original spectral spaces (i. e. Munsell color matt and DIN-6164 color chips) with highefficiency, and that the spanning space with three eigenvectors can present the original space atmore than 98% CSCR, and when 5 eigenvectors are used it can cover almost the whole o-riginal spaces.

Adaptive blind gain correction of time-interleaved ADCs forwide-band communication applications

High spectral efficiency is essential in design of multimedia communication systems such as L-band mobile in addition to various requirements of transmission quality. Time-interleaved A/D converter （TI-ADC） is an effective candidate to implement wide-band ADC with relatively slow circuits accounting for digital spectrum management. However, practical performance of TI-ADC is largely limited because of mismatches between different channels originated from manufacturing process variations. In this paper, a blind adaptive method is proposed to correct gain mismatch errors in TI-ADC, and it is verified through simulations on a two-channel TI-ADC. In proposed method, gain mismatch error is estimated and corrected in an adaptive scheme. Proposed compensated T1-ADC architecture is structurally very simple and hence suitable for realiza- tion in integrated circuits. Besides, proposed digital compensation algorithm not only is computationally efficient but also provides an improvement of 32.7 dB in the performance of two-channel TI ADC.

High-Efficiency Wide-Band Cross-Polarization Conversion Using Bi-layered Metal Hole Pairs

We present a polarization converter composed of bi-layered metal films perforated with rectangle hole pairs in each film. The proposed converter can convert the polarization of an incident linearly-polarized electromagnetic wave to its orthogonal direction with high efficiency and large bandwidth in the infrared or microwave regions.To make sure of the mechanism of polarization conversion, the current and electric-field distributions at different resonant frequencies are analyzed. It is found that the cross-polarized transmission is due to the near-field coupling between hole pairs in neighboring metal films. Finally, a prototype of the proposed converter is fabricated and measured in the microwave region. Good agreement between the experimental and simulated results is obtained.

Dynamics of Gradient Bioceramic Composite Coating on Surface of Titanium Alloy by Wide-Band Laser Cladding

The gradient bioceramic coating was prepared on the surface of titanium alloy using wide-band laser cladding.The dynamics of gradient bioceramic composite coating containing hydroxyapatite(HA)prepared with mixture of CaHPO4·2H2O and CaCO3 under the condition of wide-band laser was studied theoretically.The corresponding mathematical model and its numerical solution were presented.The examination experiment showed that HA bioceramic composite coatings can be obtained by appropriately choosing wide-band laser cladding parameters.The microstructure and surface morphology of HA bioceramic coating were observed by SEM and X-ray diffraction.The experimental results showed that the bioceramic coating is composed of HA,β-TCP,CaO,CaTiO3 and TiO2.The surface of bioceramic coating takes coral-shaped structure or short-rod piled structure,which helps osteoblast grow into bioceramic and improves the biocompatibility.

AN EFFICIENT IMPLEMENTATION ARCHITECTURE FOR WIDE-BAND DIGITAL DOWNCONVERSION

The wide-band digital receiving systems require digital downconversion(DDC) with high data rate and short tuning time in order to intercept the narrow-band signals within broad tuning bandwidth. But these requirements can not be met by the commercial DDC. In this paper an efficient implementation architecture is presented. It combines the flexibility of DFT tuning with the efficiency of the polyphase filter bank decomposition. By first decimating the data prior to filtering and mixing, this architecture gives a better solution to the mismatch between the lower hardware speed and high data rate. The computer simulations show the feasibility of this processing architecture.

2-D SPATIAL-SPECTRUM ESTIMATION FORWIDE-BAND SOURCES BASED ON INTERPOLATED CIRCULAR ARRAYS

In array signal processing, 2-D spatial-spectrum estimation is required to determine DOA of multiple signals. The circular array of sensors is found to possess several nice properties for DOA estimation of wide-band sources. C. U. Padmini, et al.(1994) had suggested that the frequency-direction ambiguity in azimuth estimation of wide-baud signals received by a uniform linear array (ULA) can be avoided by using a circular array, even without the use of any delay elements. In 2-D spatial-spectrum estimation for wide-band signals, the authors find that it is impossible to avoid the ambiguity in source frequency-elevation angle pairs using a circular array. In this paper, interpolated circular arrays are used to perform 2-D spatial-spectrum estimation for wide-band sources. In the estimation, a large aperture circular array (Υ】λmin/2) is found to possess superior resolution capability and robustness.

Genetic algorithm-based wide-band deterministic maximum likelihood direction finding algorithm

The wide-band direction finding is one of hit and difficult task in array signal processing. This paper generalizes narrow-band deterministic maximum likelihood direction finding algorithm to the wideband case, and so constructions an object function, then utilizes genetic algorithm for nonlinear global optimization. Direction of arrival is estimated without preprocessing of array data and so the algorithm eliminates the effect of pre-estimate on the final estimation. The algorithm is applied on uniform linear array and extensive simulation results prove the efficacy of the algorithm. In the process of simulation, we obtain the relation between estimation error and parameters of genetic algorithm.

Performance of multi-band orthogonal frequency division multiplexing ultra wide-band system on IEEE UWB channels

Multiband orthogonal frequency division multiplexing (MB-OFDM) ultra wide-band (UWB) is a novel wireless communication technology. It has many advantages and is being actively researhed. In this study, we constructed and implemented a simulation model of UWB communication systems in Simulink. We found the MB-OFDM UWB system has the best performance in distance between 4 m to 10 m without the line-of-sight requirement.

An Effective Thin Reservoir Identification Method for Fine Oilfield Development

Thin reservoirs prediction method such as spectral inversion has drawn considerable attention in recent years. In order to avoid extracting wavelets within the whole field area purposeless and to make the filtered data has preferable fidelity as well as signal-to-noise ratio, an effective structural constrained thin reservoir description method which combines spectral inversion and wide-band Ricker wavelet filtering technology has been proposed in this paper. The method given here is more credible and is suitable for the prediction of middle-deep thin reservoirs. We take LD-A structure within Bohai Bay Basin as an example to show the implement of our method. Several sets of thin sand layers which are hardly to recognize originally have been finally identified. Also, with the application of this method, a high-production thin reservoir of LD-B structure has been identified accurately, which provides credible information for subsequent fine oil exploration and development.

A monolithic InGaP/GaAs HBT power amplifier for W-CDMA applications

A monolithic microwave integrated circuit （MMIC） power amplifier （PA） is proposed. It adopts a new on-chip bias circuit, which not only avoids the instability of the direct current bias caused by the change in the power supply and temperature, but also compensates deviations caused by the increase in input power. The bias circuit is a current-mirror configuration, and the feedback circuit helps to maintain bias voltage at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit. A shunt capacitor at the base node of the active bias transistor enhances the linearity of the PA. The chip is fabricated in an InGaP/GaAs heterojunction bipolar transistor （HBT） process. Measured results exhibit a 26. 6-dBm output compression point, 33.6% power-added efficiency （PAE） and - 40.2 dBc adjacent channel power ratio （ACPR） for wide-band code division multiple access （W-CDMA） applications.

宽带网络信息安全实时保护管理系统的研究

本文介绍了统一控制平台下的具有智能检测功能的宽带网络信息安全实时保护管理系统,该系统包括统一的控制中心、网络入侵检测(NIDS)、主机入侵检测(HIDS)、漏洞扫描和网络密罐等子系统,可通过动态探查网络内的异常情况,及时向防火墙、路由器等设备发出警报,有效弥补了其它静态防御工具的不足。

基于宽带网的视频监控在实验教学管理中的应用

采用视频处理技术、宽带网传输技术、计算机多媒体技术,组建一种基于宽带网的实时视频监控系统,将其运用到实验工作的管理及实验室的多媒体教学中。

微型嵌入式GIS软件平台的重要意义及发展动态

近年来 ,嵌入式应用技术蓬勃发展 ,市场迅猛扩大 ,产品已经深入到工业生产和人们生活的各个角落 .制造工业、过程控制、通讯、汽车、船舶、航空、航天、军事装备、消费类产品等都已成为嵌入式计算机的应用领域 ,给微型嵌入式 GIS软件的研究与发展提供了良好的机遇 .本文从技术发展背景、含义及特点、应用发展前景、国内外发展动态、我国微型嵌入式 GIS软件平台发展的重要意义以及发展微型嵌入式 GIS软件平台的技术探讨与建议等几方面对微型嵌入式 GIS软件平台进行了详细的论述 .

浅论ADSL宽带网接入技术

本文就ADSL(Asymmetric Digital Subscriber Line)宽带网接入技术的特点和应用情况作了深入地分析,指出它是一种较为实用的宽带网接入技术方案。

宽带网发展及建议

介绍了我国宽带网的发展状况和面临的问题,提出了几点建议以推动我国的宽带网发展。

外语共同课网络化教学与外语教学改革展望

本文论述了高校外语共同课网络化教学应具备的软、硬件条件和网络环境下教材、教法特点及今后的趋势。