集成工艺中叠片BGA阵列翘曲的几何非线性预测分析

对层叠芯片BGA(SDBGA)阵列进行了线性小变形和非线性大翘曲仿真。与实验测量结果相比,线性方法不能反映翘曲形态而非线性大变形仿真能够反映出这种翘曲。原因在于,在小变形假设下,线性仿真不能考虑变形之后横断面惯性矩的变化。而非线性仿真则不受此假设的影响。文中基于非线性特性分析、预测了在整个集成工艺中SDBGA阵列的翘曲。利用“弯曲交互作用”和“翘曲竞争”解释了SDBGA阵列的翘曲特性。通过与线性仿真结果的比较,量化了几何非线性对集成工艺中SDBGA块封装翘曲的影响。     

A 1.75-GHz highly integrated narrow-band CMOS transmitter withharmonic-rejection mixers

A highly integrated 1.75-GHz 0.35-μm CMOS transmitter is described. The I/Q modulator-based transmitter facilitates integration through the use of a unique mixer, termed a harmonic-rejection mixer, and a wide loop bandwidth phase-locked loop (PLL) for the RF synthesizer. The harmonic-rejection mixers are used to eliminate the need for a discrete IF filter and the use of a wide loop bandwidth PLL allowed for the complete integration of the synthesizers using low-Q components while achieving low phase noise. The entire transmit signal path from the digital-to-analog converters to the power amplifier, including two fully integrated frequency synthesizers, is integrated into a single-chip solution. The transmitter was tested with a testing buffer before the power amplifier (PA) and achieved less than 1.3° rms phase error when modulating a DCS-1800 GMSK signal. The prototype consumed 151 mA from a 3-V supply. A class-C PA, capable of driving 25 dBm off-chip, was included and the output was compared to the testing buffer with little change in the transmitter performance     

PULSE DISCRIMINATION FOR ELECTRICAL DISCHARGE MACHINING WITH ROTATING ELECTRODE

This article presents a new method for discrimination of various types of pulses generated during an electrical discharge machining process in presence of a rotating electrode. Existing pulse discrimination methods do not perform efficiently in an electrical discharge machine with rotating electrode, as arcs rarely occur during the machining process. Our method involves simultaneous comparison of the gap voltage and current signals with various thresholds. The main advantage of our proposed method is its efficient computation and significantly better accuracy in discriminating between various pulse classes for electrical discharge machining devices with rotating electrode. Experimental studies demonstrate a superior performance of our method in distinguishing normal pulses from harmful arcs, open circuit and short circuit pulses, compared with the state-of-art methods.     

Efficient wavelet-based image denoising algorithm

Characterising the statistics of wavelet coefficients is a critical issue in image compression and denoising. Many powerful approaches have been investigated, but accurate modelling suffers from high computational complexity. In this work an efficient adaptive algorithm to capture the dependency of both inner and inter scale wavelet coefficients is proposed. Experimental results show that compared with other algorithms, in the case of higher noise variance, greater PSNR performance gain may be obtained     

A contactless biometric system using multiple hand features

With the advent of modern computing technology, there is increased reliance on biometrics to provide stronger personal authentication. Among the variety of biometric solutions in the market, hand-based system is the oldest, and perhaps the most successful form of biometric technology. This paper describes a contactless hand-based biometric system by using visible and infrared imagery. An acquisition device is developed to capture both color and infrared hand images. We modify an ordinary web camera to capture the hand vein that normally requires specialized infrared sensor. The design is simple and low-cost. No additional installation of special apparatus is required. The device can capture the epidermal and subcutaneous features from the hand simultaneously. In specific, five features namely hand geometry, palm print, palmar knuckle print, palm vein, and finger vein are acquired from the hand for recognition. Rigorous experiments had been performed to testify the robustness of the system.     

Efficient Wavelength Assignment Algorithms for Light Paths in WDM Optical Networks With/Without Wavelength Conversion

In order to reduce the overall wavelength number required in a wavelength division multiplexing (WDM) network with static traffic loading, new heuristic algorithms for wavelength assignment are proposed in this paper. A new parameter called one-wavelength-decrease cost is defined and used to compare the efficiency of these algorithms. Comparative simulation studies have been carried out for various network topologies to investigate the effectiveness of the proposed algorithms.     

Simulation and Design of AlGaAs/InGaAs CCDs Based on pHEMT Technology

This paper describes the modeling, design, and fabrication of quarter-micrometer double delta-doped AlGaAs/InGaAs charge-coupled devices (CCDs) whose epitaxial layers and geometry were based around the device structure of commercial pHEMTs. A quasi-2-D physical model has been developed to investigate the properties of this novel 2-D electron gas CCD. This physical model allows the characteristics of the InGaAs transport channel as well as the dc characteristics of the device to be predicted within a reasonable amount of time. This model also shows how "individual" charge packets can be controllably transferred through the device when appropriate clocking voltages are applied to the gates of the CCD. This capacitive gate structure device is then shown to be successfully fabricated using established GaAs heterostructure fabrication techniques to ensure good repeatability. The dc characteristics of the fabricated CCD delay line are included.