Nitride-Based High-Power Flip-Chip LED With Double-Side Patterned Sapphire Substrate

A nitride-based high-power flip-chip (FC) light-emitting diode (LED) with a double-side patterned sapphire substrate (PSS) was proposed and realized. Under 350-mA current injection, it was found that forward voltages were 3.24, 3.26, and 3.25 V for the conventional FC LED, FC LED prepared on PSS, and FC LED with double-side PSS, respectively. It was found that the 350-mA LED output powers were 79.3, 98.1, and 121.5 mW for the conventional FC LED, FC LED prepared on PSS, and FC LED with double-side PSS, respectively. In other words, we can enhance the electroluminescence intensity by 53% without increasing operation voltage of the fabricated LED     

Statistical Models for Hot Electron Degradation in Nano-Scaled MOSFET Devices

In a MOS structure, the generation of hot carrier interface states is a critical feature of the item's reliability. On the nano-scale, there are problems with degradation in transconductance, shift in threshold voltage, and decrease in drain current capability. Quantum mechanics has been used to relate this decrease to degradation, and device failure. Although the lifetime, and degradation of a device are typically used to characterize its reliability, in this paper we model the distribution of hot-electron activation energies, which has appeal because it exhibits a two-point discrete mixture of logistic distributions. The logistic mixture presents computational problems that are addressed in simulation.     

基于AMBE-1000与nRF401的无线语音传输系统的实现

介绍了Digital Voice System. Inc公司的AMBE-1000芯片与挪威Nordic 公司的nRF401芯片的特点与工作原理,给出了一种基于AMBE-1000和nRF401的无线语音传输系统的实现.系统采用AMBE-1000 结合TCM320AC36C进行语音信号的处理;同时,采用nRF401传输数字化后的语音信号;在整体上,采用AT89C52 处理器负责接口之间的数据处理.提出了系统的硬件设计、软件流程.此系统具有无需许可证、功耗低、使用方便等特点,可广泛应用于无线语音传输系统的产品设计中.     

Isometry-Based Shape-Adaptive Fractal Coding for Images

Fractal image coding is an effective method to eliminate the image redundancy through piecewise self-transformability. The fractal code consists of a set of contractive affine transforms. To improve the performance when a range block experiences large error, we usually partition the range block into square or nonsquare subrange blocks for two- or multilevel fractal coding. In this paper, we find an inherent property of fractal coding that can be used to decide the edge orientation of a range block. Then this property is used for shape-adaptive fractal coding (SAFC). In SAFC, the top-level range block is partitioned into square or nonsquare (rectangle or triangle) subrange blocks for multilevel fractal encoding. Here, the maximum size of the range block can be the same as that of the whole image size while the minimum size is 4×4. In SAFC, no additional computations are required to obtain the edge orientation of a range block. Instead, we propose an edge-orientation detector, where the edge orientation of a range block is obtained during the fractal encoding process. According to our simulation results, SAFC can reduce the bit rate requirement of the conventional fractal coding scheme.     

Noise reduction of VQ encoded images through anti-gray coding

Noise reduction of VQ encoded images is achieved through the proposed anti-gray coding (AGC) and noise detection and correction scheme. In AGC, binary indices are assigned to the codevector in such a way that the 1-b neighbors of a code vector are as far apart as possible. To detect the channel errors, we first classify an image into uniform and edge regions. Then we propose a mask to detect the channel errors based on the image classification (uniform or edge region) and the characteristics of AGC. We also mathematically derive a criterion for error detection based on the image classification. Once error indices are detected, the recovered indices can be easily chosen from a “candidate set” by minimizing the gray-level transition across the block boundaries in a VQ encoded image. Simulation results show that the proposed technique provides detection results with smaller than 0.1% probability of error and more than 86.3% probability of detection at a random bit error rate of 0.1%, while the undetected errors are invisible. In addition, the proposed detection and correction techniques improve the image quality (compared with that encoded by AGC) by 3.9 dB     

Efficient and fast iterative reweighted least-squares nonrecursivefilters

An efficient and fast technique for designing L_p approximation filters using the iterative reweighted least-squares (IRLS) algorithm is proposed. This technique introduces an extra frequency response which implicitly includes the weighting function such that the filter coefficients can be obtained with O(N²) complexity     

Dual-material gate (DMG) field effect transistor

A generic new type of field effect transistor (FET), the dual material gate (DMG) FET, is proposed and demonstrated. The gate of the DMGFET consists of two laterally contacting materials with different work functions. This novel gate structure takes advantage of material work function difference in such a way that the threshold voltage near the source is more positive than that near the drain (for n-channel FET, the opposite for p-channel FET), resulting in a more rapid acceleration of charge carriers in the channel and a screening effect to suppress short-channel effects. Using the heterostructure FET as a vehicle, the principle, computer simulation results, design guidelines, processing, and characterization of the DMGFET are discussed in detail     

Defect Engineering in Ambipolar Layered Materials for Mode-Regulable Nociceptor

Defect engineering represents a significant approach for atomically thick 2D semiconductor material development to explore the unique material properties and functions. Doping-induced conversion of conductive polarity is particularly beneficial for optimizing the integration of layered electronics. Here, controllable doping behavior in palladium diselenide (PdSe₂) transistor is demonstrated by manipulating its adatom-vacancy groups. The underlying mechanisms, which originate from reversible adsorption/desorption of oxygen clusters near selenide vacancy defects, are investigated systematically via their dynamic charge transfer characteristics and scanning tunneling microscope analysis. The modulated doping effect allows the PdSe₂ transistor to emulate the essential characteristics of photo nociceptor on a device level, including firing signal threshold and sensitization. Interestingly, electrostatic gating, acting as a neuromodulator, can regulate the adaptive modes in nociceptor to improve its adaptability and perceptibility to handle different danger levels. An integrated artificial nociceptor array is also designed to execute unique image processing functions, which suggests a new perspective for extension of the promise of defect engineered 2D electronics in simplified sensory systems toward use in advanced humanoid robots and artificial visual sensors.     

Compact Harmonic Filter Design and Fabrication Using IPD Technology

An integrated passive device (IPD) technology has been developed to meet the ever increasing needs of size and cost reduction in radio front-end transceiver module applications. Electromagnetic (EM) simulation was used extensively in the design of the process technology and the optimization of inductor and harmonic filter designs and layouts. Parameters such as inductor shape, inner diameter, metal thickness, metal width, and substrate thickness have been optimized to provide inductors with high quality factors. The technology includes 1) a thick plated gold metal process to reduce resistive loss; 2) MIM capacitors using PECVD SiN dielectric layer; 3) airbridges for inductor underpass and capacitor pick-up; and 4) a 10 mil finished GaAs substrate to improve inductor quality factor. Both lumped element circuit simulations and electromagnetic (EM) simulations have been used in the harmonic filter circuit designs for high accuracy and fast design cycle time. This paper will present the EM simulation calibration and demonstrate the importance of using EM simulation in the filter design in order to achieve first-time success in wafer fabrication. The fabricated IPD devices have insertion loss of 0.5 dB and harmonic rejections of 30dB with die size of 1.42 mm for high band (1710 MHz-1910 MHz) and 1.89 mm for low band (824-915 MHz) harmonic filters.     

Analytic forward link performance of pilot-aided coherent DS-CDMAunder correlated Rician fading

This paper presents a methodology for analyzing the forward link performance of a pilot-aided coherent DS-CDMA system under correlated Rician fading. In the forward link of a CDMA system, orthogonal modulation is usually used to minimize the self-interference. To maintain the orthogonality and reduce the receiver complexity, a common pilot channel (shared by all users) is employed to provide the reference for coherent demodulation. A tradeoff shows that a higher pilot ratio yields good channel estimates but takes away some capacity from traffic users, while a lower pilot ratio results in poorer channel estimates and leads to higher traffic power per user. This paper derives the analytical error performance, which includes (1) imperfect channel estimation by the pilot channel, (2) a very general channel model where correlations between paths as well as Rician fading are considered, and (3) interference patterns due to multiple paths and the surrounding base stations' transmissions. This paper also considers self-interference due to the loss of orthogonality caused by pulse shaping