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991.
Heung Ro Choo Beom-hoan O Chong Dae Park Hyung Mun Kim Jeong Soo Kim Dae Kon Oh Hong Man Kim Kwang Eui Pyun 《Photonics Technology Letters, IEEE》1998,10(5):645-647
The improvement of the linewidth enhancement factor in complex-coupled laser diode (CC-LD), or loss-coupled, was confirmed by measuring the spontaneous emission spectra below threshold from the sidewall of laser diodes. In addition, the serial resistance of the device was measured. The linewidth enhancement factor is improved by the presence of a light absorbing InGaAs grating for loss coupled distributed-feedback (DFB) laser diode (LD). We report the comparison of the linewidth enhancement factors of Fabry-Perot (FP) LD, conventional DFB-LD, and loss coupled DFB-LDs 相似文献
992.
The simple closed-form model of nonlinear response of a high-temperature superconducting disk resonator on microwave power is proposed. The model is based on superconducting film nonlinearity and describes the dependence of unloaded quality factor on the incident power. The specified normalizing power is used as the only fitting parameter. Good quantitative agreement of modeled and measured data has been obtained. The results observed exhibit the kinetic nature of the nonlinearity of the disk resonator on an LaAlO3 substrate at T=60 K and more complicated, presumably thermal, heating nature of the nonlinearity at lower temperature 相似文献
993.
An efficient technique to improve the accuracy of the finite-difference time-domain (FDTD) solutions employing incident-wave excitations is developed. In the separate-field formulation of the FDTD method, any incident wave may be efficiently introduced to the three-dimensional (3-D) computational domain by interpolating from a one-dimensional (1-D) incident-field array (IFA), which is a 1-D FDTD grid simulating the propagation of the incident wave. By considering the FDTD computational domain as a sampled system and the interpolation operation as a decimation process, signal-processing techniques are used to identify and ameliorate the errors due to aliasing. The reduction in the error is demonstrated for various cases. This technique can be used for the excitation of the FDTD grid by any incident wave. A fast technique is used to extract the amplitude and the phase of a sampled sinusoidal signal 相似文献
994.
Andrisano O. Tralli V. Verdone R. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1998,86(7):1383-1401
A framework for the performance characterization of short-range communications systems is developed with the intention of investigating the feasibility of new multimedia wireless services at millimeter waves (MMWs). Both narrow- and wide-band systems are considered for mobile and/or fixed users. This paper aims at defining and evaluating proper metrics to characterize the service quality for the user and jointly takes the propagation characteristics, the transmission techniques, and the multiple access protocols into account. The definition of service-oriented metrics is emphasized. Three different real scenarios operating at MMW are investigated with a unified perspective: intelligent transport systems, wide-band local-area networks, and local multipoint distribution systems for interactive video services. The role played by the MMW band in the development of these services is discussed. In each scenario, accurate propagation analysis is carried out and suitable countermeasure techniques are pointed out in order to join suitable service-quality levels. The methodology considered is based on both analytical and semianalytical tools for performance evaluation 相似文献
995.
Zhang J. Ahmad M.O. Swamy M.N.S. 《Vision, Image and Signal Processing, IEE Proceedings -》1998,145(6):399-407
The conventional overlapped block motion compensation (OBMC) technique, although effective in reducing the blocking effect for fixed-size partitioned frames, cannot be readily used for a frame partitioned region-wise or using variable-size blocks. The generalised OBMC (GOBMC) method, even though generally applicable, is not very effective in reducing the blocking effect and prediction error. Two windowing techniques are presented to reduce the blocking effect for a frame partitioned region-wise or using variable-size blocks. In the first technique, a virtual re-partitioning operation is employed, which maps a partitioned frame into its corresponding fully partitioned frame at the bottom level of the quadtree so that each resulting block has eight neighbouring blocks. In the second technique, the virtual re-partitioning operation for a given block (region) is carried out adaptively and performed locally; however, blocks (regions) need not always be virtually partitioned to the bottom level. Compared to the GOBMC method, the proposed techniques make use of more pixels in the close vicinity of boundaries of the regions in the windowing operation. Simulation results are included of applying the proposed techniques on a number of MPEG video sequences. These results indicate that the proposed techniques are superior to the GOBMC method in terms of reducing the prediction error as well as the blocking effect 相似文献
996.
The study reported herein examines and compares damage to n-channel and p-channel metal-oxide-silicon field-effect transistors (MOSFETs) from direct current (d.c.) and alternating current (a.c.) electrical stresses as well as the relationship of this damage to plasma processing damage in MOSFETs. The lightly-doped drain (LDD) MOSFETs used are of 0.5 μm channel length and with a 90 Å thick thermally grown gate oxide fabricated using a full flow CMOS process up to and including metal-1 processes and post-metallization annealing (PMA). The damage to MOSFETs is assessed using transistor parameter characterization and charge-to-breakdown measurements on the gate oxide. It is found that manifestations of d.c. stress-induced damage and a.c. stress-induced damage to transistors are fairly similar in that both forms of damage are passivated by PMA and are reactivated by a subsequent d.c. electrical stress. However, a.c. stress-induced damage is observed to occur at much lower electric fields across the gate oxide than those necessary for d.c. stress-induced damage to be significant. This is attributed to a.c. currents, caused by carrier hopping, occurring at relatively low electric fields. One implication of our results is that plasma-charging damage, often attributed to d.c. electrical stress alone, may comprise an a.c. electrical stress component too. 相似文献
997.
Plastic encapsulated microcircuits (PEMs) are increasingly being used in applications requiring operation at temperatures lower than the manufacturer’s recommended minimum temperature, which is 0°C for commercial grade components and −40°C for industrial and automotive grade components. To characterize the susceptibility of PEMs to delamination at these extreme low temperatures, packages with different geometries, encapsulated in both biphenyl and novolac molding compounds, were subjected to up to 500 thermal cycles with minimum temperatures in the range −40 to −65°C in both the moisture saturated and baked conditions. Scanning acoustic microscopy revealed there was a negligible increase in delamination at the die-to-encapsulant interface after thermal cycling for the 84 lead PQFPs encapsulated in novolac and for both 84 lead PQFPs and 14 lead PDIPs encapsulated in biphenyl molding compound. Only the 14 lead novolac PDIPs exhibited increased delamination. Moisture exposure had a significant effect on the creation of additional delamination. 相似文献
998.
We report on the performance and hot carrier stress (HCS) reliability of n-channel and p-channel poly-Si thin film transisters (TFT)s fabricated on SiO2-coated 1737 glass or bare 1737 glass substrates. Low-pressure chemical vapor deposited (LPCVD) or atmospheric pressure chemical vapor deposited (APCVD) SiO2 with different thicknesses are used as the impurity diffusion barrier layers. We have found that the performance and HCS reliability of n-TFTs on SiO2-coated 1737 glass are superior to those of n-TFTs on bare 1737 glass. P-TFTs on SiO2-coated 1737 glass, on the other hand, are observed to perform better than p-TFTs on bare 1737 glass substrates, however p-TFTs on SiO2-coated 1737 glass are seen to undergo larger improvements in their OFF current, IOFF, following the HCS compared to p-TFTs on bare 1737 glass. We also explore the impact of SiO2 coating thickness on the performance and HCS reliability of the TFTs. The HCS reliability of the TFTs on SiO2-coated 1737 glass substrates is observed to depend on the SiO2 coating thickness. This was explained in terms of a phenomenological model which involves impurity and grain boundary traps. The presence of the former type of traps is controlled by the presence or absence of the SiO2 coating, whereas the grain boundary traps are proposed to be sensitive to compressive and tensile stresses in the SiO2 coating layer which are, in turn, dependent on the layer's thickness. 相似文献
999.
Since power devices require a thick electrically active n-type silicon layer with high resistivity and a large area, their electrical characteristics are extremely sensitive to contamination. If heavy metals diffuse into the silicon wafers during the high-temperature steps, an uncontrolled increase in the leakage current and the on-state voltage can be observed. Furthermore, current filamentation and instabilities of the electrical data can occur. It turned out that the optimization of the cleaning processes, high-temperature steps and gettering treatments alone is not sufficient to avoid such effects. It is also important to avoid silicon crystal defects by proper processing. A dramatic increase in the leakage current was correlated with the appearance of silicon defects decorated with heavy metals. As a consequence of the low doping level of the n-base, the blocking voltage and the failure rate due to cosmic radiation are sensitive to contaminating atoms acting as donors. 相似文献
1000.
M. Sadeghi A. Jauhiainen B. Liss E.Ö. Sveinbjörnsson O. Engström 《Solid-state electronics》1998,42(12):2233-2238
We simulate the charge carrier traffic between the energy bands and the interface states in structures like Al/SiO2/6H–SiC, Al/diamond/Si and Al/SIPOS/Si to explain their high frequency capacitance–voltage behavior. The structures have in common that traditional electrical measurement techniques performed at room temperature are prone to thermal non-equilibrium effects. This can result in large errors in the interface data extracted from such studies when thermal equilibrium conditions are assumed. In this work, high frequency capacitance–voltage data are compared to numerical simulations which include such thermal non-equilibrium conditions to enable more accurate estimates of interface state parameters in above-mentioned structures. 相似文献