采用传输时延约束进行MPEG-2VBR视频业务平滑

由于ＭＰＥＧ－２ＶＢＲ视频码率变化剧烈,不利于信道带宽分配,因此,针对非交互式应用中视频传输延时可以大于帧周期这一情况,提出了一种基于给定传输时延下的ＶＢＲ业务平滑算法,算法主要是根据ＭＰＥＧ－２视频Ｉ,Ｐ,Ｂ帧码字数的差异,调整各帧的传输时间,在确保帧传输延进的前提下,减小帧之间的信道接入码率变化次数,从而便于进行接入控制。     

D2D通信中一种基于FFR的动态功率控制方案

工作在underlay方式下的D2D(device-to-device)通信利用资源复用共享蜂窝网络中的资源,在提高频谱资源利用率、降低移动终端功耗的同时,会给已有蜂窝网络带来干扰。在保证D2D用户和蜂窝用户的服务质量的前提下,研究了蜂窝用户和D2D用户的功率控制和资源分配问题。首先引入部分频率复用(FFR)实现蜂窝用户和D2D用户之间的资源划分和复用;然后以系统吞吐量最大化为原则,建立优化目标。结合部分功率控制(FPC)的基本思想,进而提出了一种动态功率控制(DPC)策略。仿真结果表明,所提出的方案能够有效地提高多小区系统的性能。     

面向DVB-S2标准LDPC码的高效编码结构

面向DVB-S2标准LDPC码,该文旨在实现一种基于FPGA的高效编码结构,提出一种快速流水线并向递归编码算法,可以显著提高编码数据信息吞吐率。同时,通过并向移位运算和并向异或运算的处理结构计算编码中间变量及校验位信息,在提高编码并行度的同时可有效减少存储资源的消耗。此外,针对动态自适应编码的情况优化了LDPC码编码存储结构,有效复用了数据存储单元和RAM地址发生器,进一步提高FPGA的硬件逻辑资源利用率。针对DVB-S2标准LDPC码,基于Stratix IV系列FPGA的验证结果表明,所提编码结构在系统时钟为126.17 MHz时,编码数据信息吞吐率达20 Gbps以上。     

HDTV中MPEG-2实时解码器的错误处理实用新算法研究

论述了国内外高清晰度数字电视中的ＭＰＥＧ－２实时解码器的错误处理的研究现状及其典型算法,提出了错误处理实用新算法的研究思路。算法研究与ＨＤＴＶ视频解码器硬件研制紧密结合,为国家重大项目－ＨＤＴＶ功能能样机研制直接提供算法支持。     

Is there a future for semiconducting silicides? (invited)

Silicon is commercially by far the most important semiconductor, however, because silicon has an indirect band gap it would initially appear to be unsuitable for optoelectronic applications. A major research challenge is, therefore, to achieve high intensity light emission from silicon and to engineer active and passive optical structures within it. This paper examines the potential of semiconducting silicides (principally, βFeSi₂ and Ru₂Si₃) for silicon-based optoelectronic applications. It traces the history of the subject from the first photoluminescence spectrum from βFeSi₂ to a working LED which uses βFeSi₂ precipitates as a route for fast radiative recombination. Recent results on semiconducting Ru₂Si₃ are also reported, which show, for the first time, that this material can be fabricated by high dose ion implantation. They also reveal a direct band gap of 0.91 eV. The future for semiconducting silicides is examined and, although there are still barriers to overcome — the future looks bright.     

HF chemical etching of SiO2 on 4H and 6H SiC

Thickness and etch rate of SiO₂ films thermally grown on hexagonal SiC substrates were compared to results obtained from SiO₂/Si samples. The data confirm that profilometry and ellipsometry yield the same thickness values for oxides grown on Si and SiC. Within the accuracy of our measurements, oxides grown on different polytypes and faces of SiC etch at the same rate in a HF acid solution. The etch rate using a 50:1 H₂O:HF(50%) solution at room temperature is 0.1 nm/s and is uniform throughout the thickness of the SiO₂ films. The rate is the same as that obtained for SiO₂ grown on Si.     

Effect of copper and chlorine on the properties of SiO2 encapsulated polycrystalline CdSe films

The effects of different copper doping concentrations on the properties of SiO₂ encapsulated CdSe films have been investigated. Two methods were used to dope the films with copper: ion implantation and diffusion from a surface layer. The room temperature dark resistivity of films annealed in oxygen at 450°C was found to increase as the copper concentration was increased until a maximum resistivity of 10⁸ ohm cm occurred at a copper concentration of 10²⁰ atoms cm⁻³. The room temperature resistivity in the light was found to be independent of the copper concentration and whether the films were annealed in argon or oxygen. During annealing the grains grew from 0.03 μm to 0.3 μm and this growth was independent of the doping or the annealing ambient. The energy levels, carrier mobilities, and microstructure of the annealed films were dependent on the method of doping. The ion implanted films had an additional energy level at 0.33 eV and their mobility was a factor of 4 smaller than films doped by the surface diffusion method, whose mobilities were 20 to 35 cm²V⁻¹ s⁻¹. The addition of chlorine to copper doped films had no effect on either the resistivity or photosensitivity but slowed the response times of the photocurrent by a factor of 10. No energy levels were observed which could be associated with the copper nor was the copper found to affect the density of the observed intrinsic levels at 0.65 and 1.1 eV.     

A detailed calculation of the auger lifetime in p-type HgCdTe

There has been recent experimental evidence that showed, in heavily doped p-type HgCdTe, the lifetime may be limited by the Auger 7 recombination mechanism. We have performed a detailed calculation of both the Auger 7 and Auger 1 lifetimes as a function of Cd composition (x), temperature (T), and doping (N_A). Compared with those done 20 years ago, the depth and breadth of these calculations result in a significant increase in the accuracy of the predictions. We present here the Auguer 7 lifetime for two different compositions, x=0.305 and x=0.226 over a range of temperature extending from 60 K to 300 K and for acceptor doping from 10¹⁵ cm⁻³ to 10¹⁸ cm⁻³. The calculated results for MWIR (x=0.305) are in reasonably good agreement with recent experiments performed on MWIR HgCdTe at 77 K over a range of doping. In addition, we calculated γ (≡ τ_A7 /τ_A1) with the same doping, composition (x ≈ 0.22), for a range of temperatures (40–80 K) and found γ=3–6.     

BaO-Ln2O3-TiO2系微波介质陶瓷的研究进展

综述了BaO-Ln2O3-TiO2(BLT)系微波介质陶瓷的发展历程、掺杂改性、粉体的制备方法、添加烧结助剂,改变烧结工艺等方面的进展。指出了高纯超细原料粉体的制备,先进的烧结设备,高精度的测试仪器与微波器件的混合集成化,是其今后的研究方向。     

Interfacial reaction between 42Sn-58Bi solder and electroless Ni-P/immersion Au under bump metallurgy during aging

The interfacial reaction between 42Sn-58Bi solder (in wt.% unless specified otherwise) and electroless Ni-P/immersion Au was investigated before and after thermal aging, with a focus on the formation and growth of an intermetallic compound layer, consumption of under bump metallurgy (UBM), and bump shear strength. The immersion Au layer with thicknesses of 0 μm (bare Ni), 0.1 μm, and 1 μm was plated on a 5-μm-thick layer of electroless Ni-P (with 14–15 at.% P). The 42Sn-58Bi solder balls were then fabricated on three different UBM structures by using screen printing and pre-reflow. A Ni₃Sn₄ layer formed at the joint interface after the pre-reflow for all three UBM structures. On aging at 125°C, a quaternary phase, identified as Sn₇₇Ni₁₅Bi₆Au₂, was observed above the Ni₃Sn₄ layer in the UBM structures that contain Au. The thick Sn₇₇Ni₁₅Bi₆Au₂ layer degraded the integrity of the solder joint, and the shear strength of the solder bump was about 40% less than the nonaged joints.