Temperature dependence of the electrical parameters of frozen sand at low frequencies

The permittivity of moist sand is measured at frequencies of 120 Hz and 1, 10, and 100 kHz in the temperature range +20 to-150°C. It is found that the loss tangent is close to unity at the critical temperature at which through conduction vanishes. In the case of conduction of frozen sand, it is discovered that the sand demonstrates a permittivity hysteresis if a quasi-static electric field is applied.     

Temperature dependence of electrical and optical modulationresponses of quantum-well lasers

We present theory and experiment for high-speed optical injection in the absorption region of a quantum-well laser and compare the results with those of electrical injection including the carrier transport effect. We show that the main difference between the two responses is the low-frequency roll-off. By using both injection methods, we obtain more accurate and consistent measurements of many important dynamic laser parameters, including the differential gain, carrier lifetime, K factor, and gain compression factor. Temperature-dependent data of the test laser are presented which show that the most dominant effect is the linear degradation of differential gain and injection efficiency with increasing temperature. While the K-factor is insensitive to temperature variation for multiple-quantum-well lasers, we find that the carrier capture time and nonlinear gain suppression coefficient decreases as temperature increases     

Temperature dependence of tissue impedivity in electrical impedance tomography of cryosurgery

The temperature-dependent impedivity of rat liver, transverse abdominal muscle and full skin was determined in vitro as a function of frequency across the temperature range 5 degrees C to 37 degrees C and from 100 Hz to 10 kHz. This study was motivated by an increasing interest in using electrical impedance tomography (EIT) for imaging of cryosurgery and a lack of applicable data in the hypothermic range. Using a controlled-temperature impedance analyzer, it was found that as the temperature is reduced the resulting increase in tissue impedivity is more pronounced at low frequencies and that the beta dispersion, resulting from cell membrane polarization, shifts to lower frequencies. With these new data a simple case study of EIT of liver cryosurgery was examined, using a finite-element model incorporating the Pennes bio-heat equation, to determine the impact of this behavior on imaging accuracy. Overestimation of the ice-front position was found to occur if the EIT system ignored the effects of the low-temperature zone surrounding the frozen tissue. This error decreases with increasing blood perfusion and with higher measurement frequencies.     

Temperature dependence of barrier height parameters of inhomogeneous Schottky diodes

We have shown by numerical simulations of I-V-T curves that the ideality factor of inhomogeneous Schottky diodes does not increase for decreasing temperature to such extent as is commonly observed for Schottky diodes in experiment. The main consequence of such a result is that in spite of the fact that the barrier height inhomogeneities fullfil the conditions for barrier height lowering for decreasing temperature they might not be a general or the only reason for occuring of this effect in experimental structures. We found out much slower ideality factor temperature dependence than reported in the literature and the dependence was even not monotonous for simulation conditions used. We conclude that some other reason as barrier inhomogeneity is responsible for ideality factor temperature dependence.     

应用于EMI及ESD的新型片式元器件

进入21世纪,以数字式语音通信为代表的现代移动通信技术和以计算机与网络为核心的现代信息技术分别达到前所未有的新高度,进而呈现进一步融为一体的新趋势。兼具语音通信和电子邮件、证券、金融业务等数据通信以及PDA功能三位一体化的手机也已问世。WAP(Wireless Application Protocol)已进入商业化运行阶段。笔记本电脑、PDA等便携式终端通过调制解调器即可连接Internet。第三代移动通信最终将使高速率(2Mbps)无线传输的数据通信和多媒体通信实现真正的无缝漫游,全面推动现代通信与信息技术的个人化、移动化和全球一体化。顺应通信与信息终端的便携化、小型化与多功能化发展潮流,新型元器件呈现微型化、复合化、高频化、高性能化等趋势。片式元件的小型化、微型化与高频化     

Temperature dependence of Hall mobility and electrical conductivity in SIMOX films

Transport data obtained on SIMOX films between 77 and 300 K are qualitatively different from those derived for bulk silicon. Results suggest a strong nonuniformity of carrier mobility: the uppermost part of the SIMOX layer is of comparable quality to bulk Si, but near the buried oxide there is a degradation, confirmed by prevailing coulombian scattering even at 300 K.     

Analysis and spectral characteristics of a spread-spectrumtechnique for conducted EMI suppression

Frequency modulation (FM) and random switching methods have been used for reducing conducted electromagnetic interference (EMI) in power converters. Limited theoretical studies and comparisons of these schemes, however, are available. In this paper, a detailed analysis and the spectral characteristics of a random carrier-frequency (RCF) technique for suppressing conducted EMI in an offline switched-mode power supply are presented. The analysis provides a theoretical platform for studying the characteristics of this random switching scheme. The level of randomness is defined for the RCF scheme and varied in the converter example so that the effects on the power spectra can be demonstrated. Theoretical predictions of the spectral characteristics of this scheme are confirmed with measurements. The RCF scheme has been compared with the standard constant-frequency pulsewidth modulation (PWM) scheme and the FM scheme. Comparisons of their spectral performance show that the RCF scheme has better conducted EMI suppression than the FM and standard PWM schemes     

SMD焊接温度曲线的探讨与分析

针对BGA返修系统采用热风再流焊接技术组装SMD时的焊接温度曲线进行了探讨，为提高焊接质量。根据各种元器件的物理特性，设计合适的焊接温度曲线。提出了相应的解决方案。     

抑制电磁干扰用CL62型X2类聚酯膜电容器

按ＧＢ／Ｔ１４４７２－９３（ｉｄｔＩＥＣ３８４－１４（１９９３））分规范及其详细规范研制的ＣＬ６２型（Ｘ２类）聚酯膜电容器，适用于抑制电磁干扰。研制过程中围绕高电压瞬态脉冲试验、耐久性试验、阻燃性试验等三个技术难点进行攻关，产品通过了安全认证。     

Temperature dependence of the electrical conduction in RuO2-based thick film resistors

In this paper, the temperature dependence of resistance of two generic RuO₂-based resistors is investigated. The resistor compositions studied are 80 wt.% glass (63 wt.% PbO - 25 wt.% B₂O₃ - 12 wt.% SiO₂, designated as G1) - 20 wt.% RuO₂ and 80 wt.% glass (55.5 wt.% PbO - 22 wt.% B₂O₃ - 10.5 wt.% SiO₂ - 12 wt.% Al₂O₃, designated as G2) - 20 wt.% RuO₂. The sheet resistance of resistor 80 wt.% G1 - 20 wt.% RuO₂ fired at 850° C decreases as the temperature is increased from 100 K to ∼400 K, remains a minimum value at temperatures 400 K ∼690 K, and then increases as the temperature is further raised. A negative temperature coefficient of resistance (TCR) of ∼-480 ppm/°C is obtained from 100 K to 500 K. TheTCR becomes less negative when temperature increases. Three models for conduction mechanism of thick film resistors are employed to explain the experimental results. A modified model, consisting of both tunneling and parallel conduction approaches, is proposed to elucidate the change in slope in the resistance-inverse temperature curve as well as the temperature dependence of the resistance. In addition, an equivalent circuit model is proposed to describe the electrical behavior of the thick film resistors.     

Frequency domain model of conducted EMI in electrical drives

A harmful aspect of adjustable speed drives is the presence of large high-frequency stray currents. The most important, from the view of electromagnetic compatibility, are common-mode currents at the output and input sides of the converter. Currents at the output flow through the installation ground while those at the input flow through the grid ground. These common-mode currents can cause disturbances in other units that are connected within the same power section or placed close to the drive. This paper proposes a simulation model for a complete drive system based on the frequency domain. The model accurately reproduces the behavior of common-mode currents at any point of the system and allows the user to understand the influence of each system element on the currents. Thus, the model is useful both for designing filter structures and placing them at the proper position inside the adjustable speed drive. The model is validated by means of experimental results on a 5 kVA adjustable speed drive.     

Temperature dependences of the electrical parameters of anisotype NiO/CdTe heterojunctions

The I–V characteristics of NiO/CdTe heterostructures fabricated by reactive magnetron sputtering are measured at different temperatures. It is established that current transport through the NiO/CdTe heterojunction is mainly controlled via generation–recombination and tunneling under forward bias and via tunneling under reverse bias. The investigated heterostructures generate an open-circuit voltage of V _oc = 0.26 V and a short-circuit current density of I _sc = 58.7 μA/cm² at an illumination intensity of 80 mW/cm².     

Temperature stabilization of spin-wave ferrite devices

A method for the self-compensation of the temperature drift of frequency in spin-wave ferrite devices using reversible thermal demagnetization of permanent magnets is proposed. The efficiency of the method is demonstrated for the normal magnetization of the yttrium-iron garnet (YIG) film. A configuration of the magnetic system with the built-in system for the thermal stabilization and electric frequency tuning is presented. The advantages of the system are demonstrated for the frequency stabilization of a YIG film cavity.     

An advanced monolithic digitalized random carrier frequency spread-spectrum clock generator for EMI suppression

A novel monolithic digitalized random carder frequency modulation spread-spectrum clock generator (RCF-SSCG) is proposed. In this design, the output frequency of the proposed RCF-SSCG changes with the inten-sity of the capacitive charge and discharge current. Its analytical model is induced and the effect of the modulation parameters on the spread spectrum is numerically simulated and discussed. Compared with other works, this design has the advantages of small size, low power consumption and good robustness. The circuit has been fabricated in a 0.5 μmCMOS process and applied to a class D amplifier in which the proposed RCF-SSCG occupies an area of 0.112 mm2and consumes 9 mW. The experimental results confirm the theoretical analyses.     

Temperature dependence of threshold and electrical characteristics of InGaAsP-InP d.h. lasers

Measurements are reported of the electrical characteristics and temperature dependence of threshold current of InGaAsP-InP d.h. lasers (? = 1.3 ?m). Analysis of the I dV/dI characteristics of these devices indicates that drift leakage of carriers from the active region is not responsible for the high temperature sensitivity of threshold in this material system.     

Temperature dependence of electrical properties for MOS capacitor with HfO2/SiO2 gate dielectric stack

We investigated the temperature dependence of C–V and I–V characteristics in p-type Metal Oxide Semiconductor (MOS) capacitors with HfO₂/SiO₂ dielectric stacks. Dramatic degradation in the C–V characteristics at/over the measurement temperature of 125 °C was observed, which was caused by the increased effective oxide thickness, oxide trapped charge density, and interfacial density of state (D_it) with rising temperature during bias temperature stress. In the accumulation region, the leakage current density displayed strong temperature dependence in the ?3 V<Vg<0 V region, as expected for the direct tunneling compared to the trap-assisted component (DT+TAT) effect. The conduction mechanism was transformed into Fowler–Nordheim (FN) tunneling (weak T and Vg dependence) from DT+TAT (strong T and Vg dependence) at Vg <?3 V, which was confirmed by FN tunneling fitting. According to the conventional Shockley–Read–Hall model, the different levels in D_it were found at various measurement temperatures to interpret the strong temperature dependence and weak Vg dependence inversion current property.     

一种用于抑制EMI的单片数字式随机载波扩频时钟产生器

本文提出一种全集成的随机载波频率调制扩频时钟产生器,抽象出了它的解析模型并且仿真和讨论了调制参数对扩频效果的影响。该扩频时钟信号产生器利用数字化可变电流调制技术,通过直接改变时钟信号产生器中振荡电容的充/放电电流的大小来改变时钟信号产生电路输出时钟信号频率,产生扩频时钟信号。本电路避免使用难以集成的滤波器件,从而降低了芯片的面积;而用数字技术来产生扩频时钟信号具有较低的功耗和良好的鲁棒性。本文中的RCF-SSCG已经在0.5µm CMOS工艺下制造出来并用于Class D放大器,占用面积 0.112 mm2 ,功耗为9mW。实验结果验证了理论分析。     

Measurement of ferrite parameters at microwave frequencies

A method for determining, at microwave or millimetre-wave frequencies, the relative permittivity and the saturation magnetisation of a ferrite is described. The method is based on the measurement of the guide wavelength in a rectangular guide completely filled with the ferrite and magnetised transversely. Tentative results are presented.     

副瓣消隐技术在抑制雷达间电磁干扰中的应用

为了更好地抑制地面雷达之间的电磁干扰,通过与随队干扰的干扰样式进行对比,得出了雷达间电磁干扰信号主要通过天线副瓣耦合进入接收机的特点,并在此基础之上将副瓣消隐技术引入到抑制雷达间电磁干扰中。分析了副瓣消隐的基本原理,通过相位补偿的方法消除了传统副瓣消隐技术中的相位差问题。最后对副瓣消隐技术的抗干扰效能进行了验证。     

Temperature dependence of the electrical properties of polycrystalline silicon in the dark and in sunlight

The electric resistance and effective carrier mobility in polycrystalline silicon are calculated as functions of temperature and the photoexcitation level. The theoretical results are in agreement with existing experimental data. Fiz. Tekh. Poluprovodn. 31, 954–956 (August 1997)