光纤通信中声子损耗对受激布里渊散射的影响

对光纤通信系统中的受激布里渊散射（SBS）以及声子损耗对SBS的影响进行了研究.理论上,通过数值计算得出增大声子损耗能够提高布里渊阈值的结论;实验上,测量了不同长度的光纤在不同输入光功率下的反向Stokes光及输出光,观察了光纤中加入声子阻塞器对SBS阈值的影响,并测量了阻塞器位于光纤中不同位置时的SBS.研究结果表明,在光纤线路中加入声子阻塞器可以提高SBS阈值,而且在光纤的不同位置的阻塞器对SBS影响有所不同,在被测的60 km光纤上起点30 km处插入阻塞器时的布里渊阈值最高.     

Performance evaluation of random power capture on mobile communications

Power assignment schemes are man‐made methods to enhance the capture effect of radio communications. In a previous study, Wen and Yang investigated the combined capture effect of the fixed power assignment scheme, Rayleigh fading, and near–far effect on the performance of packet radios. The performance analysis was limited to an infinite population environment. This assumption is reasonable for a conventional packet radio system with a vast service area. However, for a cellular mobile system, a finite population model should be used. In this paper, we analyse the combined natural and man‐made capture effect on the performance of a cellular system with finite population in each cell. A random power assignment scheme is adopted to produce the man‐made capture. The system throughput and delay are carried out by a Markov model. Some numerical calculations are used to demonstrate the degree of performance improvement. Copyright © 2001 John Wiley & Sons, Ltd.     

Comprehensive study on a novel bidirectional tunnelingprogram/erase NOR-type (BiNOR) 3-D flash memory cell

In this paper a recently proposed bidirectional tunneling program/erase (P/E) NOR-type (BiNOR) flash memory is extensively investigated. With the designated localized p-well structure, uniform Fowler-Nordheim (FN) tunneling is first fulfilled for both program and erase operations in NOR-type array architecture to facilitate low power applications. The BiNOR flash memory guarantees excellent tunnel oxide reliability and is provided with fast random access capability. Furthermore, a three-dimensional (3D) current path in addition to the conventional two-dimensional (2D) conduction is proven to improve the read performance. The BiNOR flash memory is thus promising for low-power, high-speed, and high-reliability nonvolatile memory applications     

Behavioral modeling of the IGBT using the Hammerstein configuration

The Hammerstein model configuration, which includes a nonlinear static block followed by a linear dynamic block, is applied to model the static and dynamic characteristics of the insulated gate bipolar transistor (IGBT). Using least-squares methods, the parameters in the behavioral model can be extracted from the electrical measurements of physical devices or from the circuit simulations of physics-based models. A single set of extracted parameters has been found to yield satisfactory efficiency and accuracy for the tested hard- and soft-switched converters under prescribed ranges of operating conditions     

Linearity and power characteristics of SiGe HBTs at high temperatures for RF applications

In this paper, the power gain, power-added efficiency (PAE) and linearity of power SiGe heterojunction-bipolar transistors at various temperatures have been presented. The power characteristics were measured using a two-tone load-pull system. For transistors biased with fixed base voltage, the small-signal power gain and PAE of the devices increase with increasing temperature at low base voltages, while they decrease at high base voltages. Besides, the linearity is improved at high temperature for all voltage biases. However, for devices with fixed collector current, the small-signal power gain, PAE, and linearity are nearly unchanged with temperature. The temperature dependence of power and linearity characteristics can be understood by analyzing the cutoff frequency, the collector current, Kirk effect and nonlinearities of transconductance at different temperatures.     

The impacts of high tensile stress CESL and geometry design on device performance and reliability for 90 nm SOI nMOSFETs

The thickness effects of high-tensile-stress contact etch stop layer (HS CESL) and impact of layout geometry (length of diffusion and gate width) on mobility enhancement of 100/(100) 90 nm SOI nMOSFETs were studied in detail. Additionally, we also inspected the low frequency characteristic with low-frequency noise investigation for FB-SOI nMOSFETs. Experimental results show that devices with 1100 Å HS CESL possess worse characteristics and hot-carrier-induced degradations than devices with 700 Å HS CESL due to serious stress-induced defects happen. The lower plateau of Lorentzian noise spectrum observed from input-referred voltage noise (S_vg) implies higher leakage current for the devices with 1100 Å HS CESL. On the other hand, we found that devices with narrow gate widths possess higher driving capacity because of larger fringing electric fields and higher compressive stress in direction perpendicular to the channel. Owing to the more serious impact of compressive stress in direction parallel to the channel, the device performance was degraded particularly for devices with shorter LOD.     

Implementation of high-coupling and broadband transformer in RFCMOS technology

This paper proposes a structure for transformer with high-coupling, broadband, and small chip area characteristics using current silicon-based technology. The proposed device has tight coupling (k=0.92), wide bandwidth (f/sub SR/=30.8 GHz), and minimum chip area (OD=140 /spl mu/m). Furthermore, the analytical formula for calculating mutual inductance is derived in this study; experimental results indicate that the analytical formula is feasible. The proposed transformer will be useful in designing high-performance RF integrated circuits for wireless applications.     

A Novel Character Segmentation Method for Text Images Captured by Cameras

Due to the rapid development of mobile devices equipped with cameras, instant translation of any text seen in any context is possible. Mobile devices can serve as a translation tool by recognizing the texts presented in the captured scenes. Images captured by cameras will embed more external or unwanted effects which need not to be considered in traditional optical character recognition (OCR). In this paper, we segment a text image captured by mobile devices into individual single characters to facilitate OCR kernel processing. Before proceeding with character segmentation, text detection and text line construction need to be performed in advance. A novel character segmentation method which integrates touched character filters is employed on text images captured by cameras. In addition, periphery features are extracted from the segmented images of touched characters and fed as inputs to support vector machines to calculate the confident values. In our experiment, the accuracy rate of the proposed character segmentation system is 94.90%, which demonstrates the effectiveness of the proposed method.     

Optimization of an RFID location identification scheme based on the neural network

An indoor localization technology is increasingly critical as location‐aware applications evolve. Researchers have proposed several indoor localization technologies. Because most of the proposed indoor localization technologies simply involve using the received signal strength indicator value of radio‐frequency identification (RFID) for indoor localization, radio‐frequency interference, and environmental factors often limit the accuracy of localization results. Therefore, this study proposes an accurate RFID localization based on the neural network (ARL‐N²), a passive RFID indoor localization scheme for identifying tag positions in a room, combining a location identification based on dynamic active RFID calibration algorithm with a backpropagation neural network (BPN). The proposed scheme composed of two phases: in the training phase, an appropriate BPN architecture is constructed using the training data derived from the coordinates of reference tags and the coordinates obtained using the localization algorithm. By contrast, the online phase involves calculating the tracking tag coordinates and using these values as BPN inputs, thereby enhancing the estimated location. A performance evaluation of the ARL‐N² schemes confirms its high localization accuracy. The proposed method can be used to locate critical objects in difficult‐to‐find areas by creating minimal errors and applying and economical technique. Copyright © 2013 John Wiley & Sons, Ltd.     

A new shared AWG-based OCDMA scheme implemented with time-spreading and wavelength-group-hopping embedded M-sequence code

This paper exploits the inherent cyclic and periodic free-spectral-range (FSR) properties of arrayed-waveguide grating (AWG) routers to construct a two-dimensional (2D) time-spreading and wavelength-group-hopping embedded M-sequence code for optical multiple-access networks. In the proposed codecs (encoder/decoder), a fine arrayed-waveguide grating (AWG) is used to generate an M-sequence code pattern, which is then spread in the wavelength domain by multiple coarse AWGs. The signals produced at the output ports of the coarse AWGs are then spread in the time domain using optical delay lines. The 2D code is evaluated in terms of its correlation, bit-error-rate (BER) and cardinality characteristics. It is shown that the TS/GH embedded M-sequence code yields a significant improvement in both the BER and cardinality performance of the optical multiple-access networks compared to that obtained using conventional prime-hop code (PHC), modified prime-hop code (MPHC), Barker and Walsh-based bipolar–bipolar sequence.