Semi-empirical model for millimetre-wave vegetation attenuationrates

An improved empirical model of the attenuation rates due to propagation through vegetation at millimetre-wave frequencies is described. The measured vegetation attenuation rates of 38 GHz signals were fitted to a two-parameter model with a final slope of 0 dB/m, to give an improvement in fit over the current ITU recommendation. However, this final slope is not a typical characteristic and is not seen at other frequencies. A new three-parameter model has been developed, which may have a nonzero final slope, giving the model greater freedom and therefore a better fit to measured data at all frequencies     

Refinement of the Subthreshold Slope Modeling for Advanced Bulk CMOS Devices

We present here a simple analytical model of the subthreshold slope of CMOS devices that successfully describes the long-channel plateau, the initial improvement for medium gate lengths, and the final degradation for short gate lengths. The model is based on the voltage-doping transformation (VDT) that leads to a new term in the subthreshold slope expression, explaining the degradation of the slope at very short channels. The potential minimum at the virtual cathode was expressed using a semiempirical expression that allows our model to fit to data that were extracted from simulation in a wide range of device parameters. Finally, the new slope model successfully reproduced experimental data that were measured on devices based on 90- and 65-nm technologies, demonstrating the validity of our model for advanced bulk CMOS technologies.     

Linearisation of high-ratio, wide-range bipolar current mirrors

A new design strategy for implementing bipolar current mirrors with a high input to output ratio and a wide current range is presented. The strategy is based on a known area efficient topology. The new strategy improves the linearity of the current mirror at high currents.<>     

一种提高原边反馈AC/DC恒流精度的方法

针对传统原边反馈AC/DC由于峰值电流检测不准造成的输出恒流精度较低的问题,文中提出了一种应用于原边反馈的高精度恒流控制方法。该控制方法引入I_pk斜率检测来估计真正的原边峰值电流,以此提高输出恒流精度。通过LED驱动电路实验,验证结果表明,相比传统电路,此方法提高了恒流输出精度,在85~265 V输入电压范围下,恒流精度约为2%。     

A new reliability growth model: its mathematical comparison to the Duane model

The Duane reliability growth model has been traditionally used to model electronic systems undergoing development testing. This paper proposes a new reliability growth model derived from variance stabilisation transformation theory which surpasses the Duane model in typical reliability growth situations. This new model is simpler to plot and fits the data more closely than the Duane model whenever the Duane slope is less than 0.5. This paper explores the mathematical relationships between these two models; and shows that at a Duane slope of 0.5, both models are mathematically equivalent in their capacity to fit the observed data. The instantaneous MTBF of the new model is also developed and compared to that of Duane. As the new model is influenced by the later failures, compared to early failures for the Duane model, it has the further advantage of leading to reduced test times for achieving a specified instantaneous MTBF. As the reliability of electronic systems increases, this has positive implications for testing.     

Temperature-humidity-bias behavior and acceleration factors fornonhermetic uncooled InP-based lasers

The stability of uncooled InP-based laser diodes in humid ambients was studied. Nonhermetic devices were aged at two different temperatures and humidities at a constant current and at one temperature and humidity at six different drive currents. For all nonhermetic devices failure occurred as a result of a large increase in the threshold current. The reverse leakage current for the failures did not increase when the threshold current increased, indicating that the change in threshold was a result of a change in reflectivity of one or both facets. The hermetic control group of devices aged under many of the same conditions showed a gradual increase in both the threshold current and slope efficiency. The median lifetimes as determined by assuming a device was a failure when the threshold current increased by 50% was strongly dependent upon humidity temperature and drive current. The lifetime data was fit to and equation of the form lifetime exp(-E_α/kT) exp(-B_RH [RH²]). The values of E_α and B_RH were 0.52 eV and 4.9×10^-4/%², respectively. The current drive data was fit to and expression of the form lifetime a exp(I^αI_op) where I_α as 0.09 h/mA. The lifetime dependence on current drive was modeled by assuming that the drive current caused a local temperature rise through thermal resistance. This local temperature rise then caused a decrease in the local humidity at the diode surface through an expression of the form %RH_diodeα exp (-5990[1/(T_r+T_ambient)-1/T_ambient ])where where T_r is the local temperature rise due to thermal impedance. Finally, we present our preliminary results on the reliability of nonhermetic SiO_x passivated lasers. These results indicate that such lasers can be made with sufficient reliability for use in telecommunications application     

Drift estimation using pairwise slope with minimum variance in wireless sensor networks

Time synchronization is mandatory for applications and services in wireless sensor networks which demand common notion of time. If synchronization to stable time sources such as Coordinated Universal Time (UTC) is required, employing the method of flooding in order to provide time synchronization becomes crucial. In flooding based time synchronization protocols, current time information of a reference node is periodically flooded into the network. Sensor nodes collect the time information of the reference node and perform least-squares regression in order to estimate the reference time. However, least-squares regression exhibits a poor performance since sensor nodes far away from the reference node collect the time information with large deviations. Due to this fact, the slopes of their least-squares line exhibit large errors and instabilities. As a consequence, the reference time estimates of these nodes also exhibit large errors.This paper proposes a new slope estimation strategy for linear regression to be used by flooding based time synchronization protocols. The proposed method, namely Pairwise Slope With Minimum Variance (PSMV), calculates the slope of the estimated regression line by considering the pairwise slope between the earliest and the most recently collected data points. The PSMV slope is less affected by the large errors on the received data, i.e. it is more stable, and it is more computationally efficient when compared to the slope of the least-squares line. We incorporated PSMV into two flooding based time synchronization protocols, namely Flooding Time Synchronization Protocol (FTSP) and PulseSync. Experimental results collected from a testbed setup including 20 sensor nodes show that PSMV strategy improves the performance of FTSP by a factor of 4 and preserves the performance of PulseSync in terms of synchronization error with 40% less CPU overhead for linear regression. Our simulations show that these results also hold for networks with larger diameters and densities.     

Sensorless torque control of SyncRel motor drives

This paper describes a direct self-control (DSC) scheme for synchronous reluctance motor drives. The presented DSC scheme develops a new torque control methodology that does not require any position transducer to synchronize the stator current vector with the rotor. Such a control strategy differs from the conventional DSC approach in order to fit some specific requirements of synchronous reluctance (SyncRel) machines. First, torque and rotor position are controlled instead of torque and stator flux as in a conventional DSC scheme. Second, the operating sector is selected according to the actual position of the current vector rather than the position of the stator flux. The proposed methodology allows simplifying implementation of the torque control on SyncRel drives and reducing the global cost for medium-performance electric drives. Simulations and experimental tests on a 1.5-kW motor drive are provided to evaluate the consistency and the performance of the proposed control technique     

Compensation strategies for shunt active-filter control

Compensation strategies for control of shunt active filters are compared in the paper. It is shown that the strategy based on unity-power factor control is appropriate when the supply voltage waveform of the plant where the active filter is connected shows significant distortion. As voltage distortion increases, this strategy provides compensated line current having lower harmonic distortion and RMS value with respect to the strategy generally used. This contributes to diminish the current and voltage distortion in networks. The unity-power factor compensation strategy conditions the current flowing in the plant where compensation is realized to fit the voltage waveform, thus reaching a unity power factor. Hence, the line current RMS value is minimum. The comparison of the strategies is performed by both Monte Carlo and ATP simulation     

分级复合服务策略的多站循环服务系统

对于多站(多队列)循环服务系统,本文提出一种可动态调整服务量的分级复合型新策略,以适应站点负荷非均衡系统。文章讨论的主要内容有:(1)新策略简介;(2)新策略系统排队服务模型特点;(3)新策略系统在队列容量有限时的队列状态转移规律;(4)队列状态转移概率算法;(5)队列状态概率的非常规算法。     

Analytical model for the high-temperature behaviour of the subthreshold slope in MuGFETs

As MuGFETs are promising contenders for the end of the silicon Roadmap, their high-temperature behaviour needs to be addressed. In this work we investigate the variations of the subthreshold slope (SS) of double-gate devices and MuGFETs with intrinsic doping as a function of the temperature and fin width. Focus is placed on the superlinear behaviour of SS occurring above a certain temperature threshold. Numerical simulations are performed using Comsol Multiphysics^™ and a 1D analytical model is developed. The model, which includes the effect of film and gate oxide thickness, is shown to accurately fit the numerical data. A new definition for the subthreshold slope under high-temperature operation is proposed. The high-temperature subthreshold slope degradation is shown to increase with fin width.     

一种新型开关电流余量放大器

提出了一种基于互补双极工艺的新型余量放大器。该余量放大器由电阻反馈阵列、开关电流阵列和互补双极运算放大器组成,采用了恒定共模电流的方式。相比于传统余量放大器,该余量放大器的时序更简单、精度更高。采用开关电流阵列来调整整个余量放大器的电流流向,采用带高增益放大器的电阻反馈阵列来产生相应的余量放大。在流水线模数转换器中,该余量放大器实现了分段放大功能。     

高斜效率高功率850nm氧化限制型垂直腔面发射激光器

报道了MOCVD生长的高性能850nm氧化限制型垂直腔面发射激光器.研制出的氧化直径为9μm的激光器25℃时的斜效率和阈值电流分别为0.82mW/mA和2.59mA,激光器在23mA时输出16mW最大光功率.氧化直径为5μm的激光器25℃时的最小阈值电流为570μA,其最大饱和光功率为5.5mW.     

基于CAN总线的煤矿机车电池管理系统设计

针对煤矿机车锂电池,文章设计了一种基于CAN总线的多节锂电池串联电池组管理系统,实现了对电池信息的检测与分析处理,并将传统的电压法与电流积分法相融合,提出一种剩余电量的估算策略。从硬、软件两个方面保证了系统的工作效率与可靠性。     

Microdischarge in microbridge plasma display with holes in thecathode

A new microbridge plasma display structure with holes in the cathode has been fabricated and operated at high gas pressure (400-700 Torr). With a hole diameter of 100 μm, the slope of the I-V curve in the discharge cell of the new structure is positive at 700 Torr. It is found that the discharge in this new structure has about 100 kohm internal resistance, and the discharges are stable when operated without current limiting resistors. The operating current in the new structure is about 50 μA with smaller 75 μm diameter holes in the cathode     

Some new calculations on antenna superdirectivity

The fundamental limitation of superdirective antenna arrays was previously demonstrated through calculation of Chebyshev arrays. Those arrays are not optimum and have an extraneous parameter (sidelobe level). A new calculation is made using maximum directivity arrays and it is shown that log Q varies approximately linearly with directivity. A close fit to this behavior is given by log Q = π(G- G0). The π slope has been inferred from work of Rhodes but cannot be physically justified at this time.     

一种高速宽带升压转换器斜坡补偿电路的设计

峰值电流模式升压型直流-直流转换器在连续导通模式下,当占空比大于50%时会出现闭环不稳,产生次谐波振荡等现象,需进行斜坡补偿.讨论了斜坡补偿的意义,并设计了一种结构简单的电流检测和斜坡补偿电路,该电流检测采用一种电流负反馈电路进行电压箝位,斜坡补偿时未采用传统的加法器对补偿斜率相加的方式,而是直接将采样电流和补偿电流在电流节点加和,解决了比较器引入附加回路对带宽的限制,瞬态响应速度较快.此电路基于MagnaChip公司HL18GFL 0.18 μm工艺设计,并进行了流片.测试结果表明,斜坡斜率为3.17 mV/ns,满足系统稳定性要求.本电路面积仅为128.7 μm×62.8 μm,电流检测精度在5%以内.     

Modeling of multilevel structures: a general method for analyzingstress evolution during processing

This work presents a general modeling technique for following the evolution of the stress field during the manufacturing of multilevel structures. This technique combines the finite element method with a modeling strategy that uses artificial nodes to simulate material interfaces. It can be applied to both linear and nonlinear structures. The main advantage of this approach is that it allows one to account for all topological and geometric changes during the manufacturing process, as well as the residual stresses introduced at each stage. Its implementation is very straightforward since it is compatible with current finite element technology and most commercial codes. The usefulness of this technique is illustrated with an example concerning an encapsulated copper line     

Diffusion length and surface recombination velocity measurements with the scanning electron microscope: The highly-doped emitter of a p-n junction

Analytical solutions of the electron-beam induced current response for a spherical source excitation are formulated for a finite region of semiconductor using the method of images. The analytic approach is different from that normally reported for semi-infinite region analysis because it incorporates a third boundary condition into the problem. Consequently, it is more general because it is valid for all regions of width greater than or equal to two real excitation volume radii. The analytic solutions predict that absolute, not relative, current responses must be used to determine diffusion lengths in finite regions of semiconductors and that the slope of the response is relatively insensitive to the surface recombination velocities. The solutions are demonstrated to correctly fit normalized data for the response of a highly-doped emitter.     

Application of a generalized current multilevel cell tocurrent-source inverters

In this paper, a new cell which lends itself as a generic current multilevel one is applied to current-source inverters with output current harmonics minimization and without the use of high-frequency modulation. In this cell, inductors acting as current sources ensure equal current division among switches. DC current balance in the inductors is achieved, also, without closed-loop control. It is also shown that, while, for the five-level structure it is easy to find a proper control strategy, for higher levels, it is necessary to use numerical simulation programs to find out a proper switching strategy. Simulation and experimental results are included to show the performance of the new cell for high-power applications