用纳米铜油墨印刷RFID标签天线

采用廉价的纳米铜导电油墨直接印刷电路图案,再经紫外固化形成导电线路,铜膜导电线路表现出金属般的外观,其电阻率是纯铜的10倍,成本接近当前印刷线路板的成本,且工艺简单、环保和生产灵活,可望在一些领域替代传统的蚀刻电子线路.     

A Low-Complexity Precoding Scheme for Downlink Massive MU-MIMO Systems with Low-Resolution DACs

In this paper, we investigate the problem of downlink precoding for the narrowband massive multi-user multiple-input multiple-output (MU-MIMO) system with low-resolution digital-to-analog converters (DACs). We introduce a low-complexity precoding scheme based on the alternating direction method of multipliers (ADMM) framework in this work. An efficient gradient descent (GD) algorithm with adaptive step-size determination mechanism (ASGD) is proposed to alleviate the computational complexity bottleneck of the inherent matrix inversion. Numerical results demonstrate that the ASGD precoder achieves an attractive trade-off between the performance and computational complexity compared with other counterparts.

     

DSSS/QPSK信号盲检测方法仿真

采用功率谱检测法,自相关检测法和高阶累计量检测法对低信噪比下DSSS/QPSK信号进行检测方法。计算机仿真表明,功率谱检测法在信噪比较低时失去了检测能力,而充分利用了伪随机码周期特性的自相关检测法和高阶累计量检测法的检测性能较优,高阶累计量法由于其更好的抑制噪声特性显示出更好的性能。同时,文中比较了DSSS/BPSK信号和DSSS/QPSK信号在相同检测方法下的性能差异。由于调制方式不同,相同的方法对DSSS/QPSK信号的检测性能略低于DSSS/BPSK信号。     

一种基于Lange耦合器的S波段小型化集成功放

设计了一种全部采用国产芯片研制的小型化集成功放模块。该模块采用一种全新的结构模式,通过Lange耦合器将GaAs MMIC单片、单电源GaAs功率芯片和硅功率芯片混合集成,使得其体积比同等性能的功率放大器减小。测试结果表明,在工作电压36V、脉宽300μs、占空比10%的测试条件下,2.7～3.1GHz或3.1～3.4GHz带内输出功率均能达到50W,36V电源效率大于40%。     

GaAs功率单片脉冲在片测试技术研究

讨论了功率单片在片脉冲测试中在片校准技术、脉冲功率测试技术等难题,并在讨论以上问题的基础上,实现工程化应用,该测试技术能够有效覆盖至40GHz。在建立的脉冲大功率在片测试系统上对输出功率典型值5W的GaAs功率单片放大器进行测试验证,测试结果和装架测试结果相比较,输出功率误差<0.2dB。     

Highly Crystalline Soluble Acene Crystal Arrays for Organic Transistors: Mechanism of Crystal Growth During Dip‐Coating

The preparation of uniform large‐area highly crystalline organic semiconductor thin films that show outstanding carrier mobilities remains a challenge in the field of organic electronics, including organic field‐effect transistors. Quantitative control over the drying speed during dip‐coating permits optimization of the organic semiconductor film formation, although the kinetics of crystallization at the air–solution–substrate contact line are still not well understood. Here, we report the facile one‐step growth of self‐aligning, highly crystalline soluble acene crystal arrays that exhibit excellent field‐effect mobilities (up to 1.5 cm V^?1 s^?1) via an optimized dip‐coating process. We discover that optimized acene crystals grew at a particular substrate lifting‐rate in the presence of low boiling point solvents, such as dichloromethane (b.p. of 40.0 °C) or chloroform (b.p. of 60.4 °C). Variable‐temperature dip‐coating experiments using various solvents and lift rates are performed to elucidate the crystallization behavior. This bottom‐up study of soluble acene crystal growth during dip‐coating provides conditions under which one may obtain uniform organic semiconductor crystal arrays with high crystallinity and mobilities over large substrate areas, regardless of the substrate geometry (wafer substrates or cylinder‐shaped substrates).     

Joint optimization of power allocation and relay location for regenerative relaying with multi‐antenna reception at destination

We consider joint power allocation (PA) and relay positioning in a dual‐hop regenerative relay system with multiple antennas equipped at the destination. With a fixed relay location, an adaptive PA strategy at the source and relay under a sum power constraint that minimizes the system outage probability is presented. With a fixed PA strategy, the optimal relay location is derived. We then propose to jointly optimize PA and relay location. It is shown that employing more destination antennas and/or choosing an appropriate relay location can significantly save the power needed at the relay. Numerical results are presented to demonstrate the performance of the proposed PA and relay positioning algorithms. Copyright © 2011 John Wiley & Sons, Ltd.     

A Novel Approach to BaTiO3-based X8R Ceramics by Calcium Borosilicate Glass Ceramic Doping

High-performance X8R dielectric materials could be sintered at 1150°C by doping calcium borosilicate (CBS) glass ceramic into the BaTiO₃-Nb₂O₅-ZnO system, with a dielectric constant greater than 1800 and a dielectric loss lower than 1.0%. The effects of CBS, Nb₂O₅, and ZnO on the dielectric properties were discussed in this article. The X8R specification was achieved with the content of CBS ≥ 4 wt.%, Nb₂O₅ ≥ 1.0 mol%, and ZnO ≤ 2.0 mol%. The sample doped with 4 wt.% CBS exhibited the highest density and lowest dielectric loss in our experiment. A reduction in grain size was observed in the specimens with 4 and 7 wt.% CBS as compared with CBS-free specimen, whereas the abnormal growth of rectangle-shaped grains took place in the 10 wt.% CBS-doped specimen. The Curie point progressively moved to higher temperatures with CBS content up to 7 wt.%. However, T _c of the sample decreased slightly in the case when 10 wt.% CBS was doped. X-ray diffraction (XRD) analysis indicated that the crystal structure of sintered ceramics changed from tetragonal to pseudocubic symmetry as increasing CBS content.     

一种新的无可信中心的门限签名体制

文章基于双线性对提出了一种新的无可信中心的门限签名体制。在多数环境中一个可信中心并不存在,所以没有可信中心的门限签名体制更受青睐,并且该协议几乎满足一个良好的门限签名体制的所有要求。该协议简单可行,在电子商务和电子投票中比其他协议更实用。     

Coherent and Differential Downlink Space-Time Steering Aided Generalised Multicarrier DS-CDMA

This paper presents a generalised multicarrier direct sequence code division multiple access (MC DS-CDMA) system invoking smart antennas for improving the achievable performance in the downlink. In this contribution, the MC DS-CDMA transmitter employs an antenna array (AA) and steered space-time spreading (SSTS). Furthermore, the proposed system employs both time and frequency (TF) domain spreading for extending the capacity of the system, which is combined with a user-grouping technique for reducing the effects of multi-user interference (MUI). Moreover, to eliminate the high- complexity multiple input multiple output (MIMO) channel estimation required for coherent detection, we also propose a Differential SSTS (DSSTS) scheme. More explicitly, for coherent SSTS detection MVN_r number of channel estimates have to be generated, where M is the number of transmit AAs, V is the number of subcarriers and N_r is the number of receive antennas. This is a challenging task, which renders the low-complexity DSSTS scheme attractive.