A Signed Array Multiplier with Bypassing Logic

A low power digital signed array multiplier based on a 2-dimensional (2-D) bypassing technique is proposed in this work. When the horizontally (row) or the vertically (column) operand is zero, the corresponding bypassing cells skip redundant signal transitions to avoid unnecessary calculation to reduce power dissipation. An 8×8 signed multiplier using the 2-D bypassing technique is implemented on silicon using a standard 0.18 μm CMOS process to verify power reduction performance. The power-delay product of the proposed 8×8 signed array multiplier is measured to be 31.74 pJ at 166 MHz, which is significantly reduced in comparison with prior works.     

Electrical Percolation Behavior in Silver Nanowire–Polystyrene Composites: Simulation and Experiment

The design and preparation of isotropic silver nanowire‐polystyrene composites is described, in which the nanowires have finite L/D (< 35) and narrow L/D distribution. These model composites allow the L/D dependence of the electrical percolation threshold, ?_c, to be isolated for finite‐L/D particles. Experimental ?_c values decrease with increasing L/D, as predicted qualitatively by analytical percolation models. However, quantitative agreement between experimental data and both soft‐core and core–shell analytical models is not achieved, because both models are strictly accurate only in the infinite‐L/D limit. To address this analytical limitation, a soft‐core simulation method to calculate ?_c and network conductivity for cylinders with finite L/D are developed. Our simulated ?_c results agree strongly with our experimental data, suggesting i) that the infinite‐aspect‐ratio assumption cannot safely be made for experimental networks of particles with L/D < 35 and ii) in predicting ?_c, the soft‐core model makes a less significant assumption than the infinite‐L/D models do. The demonstrated capability of the simulations to predict ?_c in the finite‐L/D regime will allow researchers to optimize the electrical properties of polymer nanocomposites of finite‐L/D particles.     

A wireless brainwave-driven system for daily-life analyses and applications

Smartphones have become more popular in our lives. We will no longer need to use our hands to control phones to do such things as take pictures, switch music, or make phone calls in the future; we will use our brains: all that can be controlled with the use of brainwaves instead. In this study, we implement a novel system that contains the most commonly used functions of a smartphone, including camera use and music play, with an app that uses brainwave controls. In addition, we also provide an essential daily-use function which can remind us to concentrate when we drive, study, or do something important. Under the proposed system, when the wireless brainwave instrument is worn, brainwave signals transfer to the smartphone via Bluetooth automatically and execute the aforementioned functions. Experimental results indicate that the present system is effective and suitable for such applications in our lives. In the future, some more related applications will be developed with brainwave control for practical daily-life uses.     

Characteristic of copper wire and transient analysis on wirebonding process

In the present paper, two major analyses are achieved. In the first, experimental procedures were accomplished to measure tensile mechanical properties of copper (Cu) wire (? = 1 mil) before/after electric flame-off (EFO). Characteristics of free air ball (FAB), heat affected zone (HAZ) and thermal stable zone (TSZ) in as-drawn wire have been carefully investigated by microhardness, self-design pull test fixture, nanoindentation and atomic force microscopy (AFM). A 2nd EFO real-time technique has been conducted to reduce the strength of Cu wire and increase the bonding region. Secondary, with the obtained experimental material data, a comprehensive finite element wirebonding model based on explicit time integration software ANSYS/LS-DYNA is developed to predict the overall strain/stress distributions on the aluminum (Al) bond pad. Finite element analysis (FEA) results demonstrate that plastic deformation on Al bond pad around smashed FAB can be reduced by increasing the surface roughness on FAB. A series of comprehensive parametric studies were conducted in this research.     

Nitrogen implanted polysilicon resistor for high-voltage CMOStechnology application

A nitrogen-implanted polysilicon thin film resistor has been proposed to improve the electrical characteristics of resistors in high-voltage CMOS technologies. The SIMS profile shows the proposed nitrogen-implanted polysilicon resistor can raise 100 times of the concentration of nitrogen. Thereby, the temperature coefficient of resistance (TCR), voltage coefficient of resistance (VCR), and mismatch are improved 20.4%, 35.9%, and 23.5% in average, respectively. The improvements are attributed to the suppression of both hydrogen intrusion by the presence of high-nitrogen concentration in polysilicon     

CPW-fed circular slot antenna with slit back-patch for 2.4/5 GHz dual-band operation

A circular slot antenna fed by a coplanar waveguide (CPW) is proposed for dual-band operations. Dual frequency bands that cover the 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) bands were obtained by embedding a pair of slits in the circular back-patch that is printed on the backside of the substrate and concentric with the circular slot. This design resulted in broadside far-field patterns with low cross-polarisation levels in both frequency bands and a small antenna size of 40/spl times/40 mm with the ground plane regarded as part of the antenna structure.     

UPCF: a new point coordination function with QoS and power management for multimedia over wireless LANs

In this paper, we propose a new novel polling-based medium access control protocol, named UPCF (Unified Point Coordination Function), to provide power conservation and quality-of-service (QoS) guarantees for multimedia applications over wireless local area networks. Specifically, UPCF has the following attractive features. First, it supports multiple priority levels and guarantees that high-priority stations always join the polling list earlier than low-priority stations. Second, it provides fast reservation scheme such that associated stations with real-time traffic can get on the polling list in bounded time. Third, it employs dynamic channel time allocation scheme to support CBR/VBR transportation and provide per-flow probabilistic bandwidth assurance. Fourth, it employs the power management techniques to let mobile stations save as much energy as possible. Fifth, it adopts the mobile-assisted admission control technique such that the point coordinator can admit as many newly flows as possible while not violating QoS guarantees made to already-admitted flows. The performance of UPCF is evaluated through both analysis and simulations. Simulation results do confirm that, as compared with the PCF in IEEE 802.11, UPCF not only provides higher goodput and energy throughput, but also achieves lower power consumption and frame loss due to delay expiry. Last but not least, we expect that UPCF can pass the current Wi-Fi certification and may coexist with the upcoming IEEE 802.11e standard.     

Failure modes and effects analysis for high-power GaN-based light-emitting diodes package technology

In this study, nondestructive test is developed to analyze the structure failure of LED package. The relationship between thermal resistance analysis and LED package failure structure is build with T3Ster thermal transient tester and scanning electron microscope (SEM). The failure LED device with defect in the attaching layer and gap between LED chip and copper are designed advisedly. The failure factors of LED package have been measured with thermal resistance analysis and SEM cross-section images. The thermal dissipation performance of LED with defect in the attaching layer is indicated by thermal resistance analysis combined with SEM cross-section images. The blister in attaching layer results in 4.4 K/W additional thermal resistance. The gap between LED chip and copper also makes high additional thermal resistance with 8.6 K/W. Different failures of LED packages are indicated obviously using thermal transfer analysis. The LED package failure structure such as interface defect between solder and cup-shaped copper is able to forecast without destructive measurement.     

Model for Increasing the Power Obtained from a Thermoelectric Generator Module

We have developed a model for finding the most efficient way of increasing the power obtained from a thermoelectric generator (TEG) module with a variety of operating conditions and limitations. The model is based on both thermoelectric principles and thermal resistance circuits, because a TEG converts heat into electricity consistent with these two theories. It is essential to take into account thermal contact resistance when estimating power generation. Thermal contact resistance causes overestimation of the measured temperature difference between the hot and cold sides of a TEG in calculation of the theoretical power generated, i.e. the theoretical power is larger than the experimental power. The ratio of the experimental open-loop voltage to the measured temperature difference, the effective Seebeck coefficient, can be used to estimate the thermal contact resistance in the model. The ratio of the effective Seebeck coefficient to the theoretical Seebeck coefficient, the Seebeck coefficient ratio, represents the contact conditions. From this ratio, a relationship between performance and different variables can be developed. The measured power generated by a TEG module (TMH400302055; Wise Life Technology, Taiwan) is consistent with the result obtained by use of the model; the relative deviation is 10%. Use of this model to evaluate the most efficient means of increasing the generated power reveals that the TEG module generates 0.14 W when the temperature difference is 25°C and the Seebeck coefficient ratio is 0.4. Several methods can be used triple the amount of power generated. For example, increasing the temperature difference to 43°C generates 0.41 W power; improving the Seebeck coefficient ratio to 0.65 increases the power to 0.39 W; simultaneously increasing the temperature difference to 34°C and improving the Seebeck coefficient ratio to 0.5 increases the power to 0.41 W. Choice of the appropriate method depends on the limitations of system, the cost, and the environment.