科研成果 by Type: Conference Proceedings

In this paper, the design of a 10 mW concurrent triband RF rectifier at 1050 , 2050 and 2600 MHz using the high impedance transmission line with two short stubs is presented. Experimental results show that the efficiency is achieved 59.2 % at 1050 MHz, 35.6 % at 2050 MHz and 52.2 % at 2600 MHz. Compared to the state-of-the-art of multi-band rectifiers, the proposed triband rectifier has the ability to harvest RF energy from the corresponding operating frequencies sources.

This paper proposes a filter realised using only lumped-element components, implemented as a highly selective bandpass filter suitable for lowpass delta-sigma (LPΔΣ) RF transmitters. The proposed filter is characterised by low insertion loss, high selectivity and a transfer function tailored for filtering the close-up out-of-band noise of LPΔΣ RF transmitters. The circuit design is based on a modified loaded-stub ring-resonator structure, however, implemented using 4 π-shape lumped-element resonators with LC tanks. The measurements show good agreement with simulation and the proposed filter provides a fractional 3-dB bandwidth of 14.3 %, insertion loss of less than 1.6 dB, suppression of more than 18 dB on both sides of the desired band, and a sharp cut-off frequency response. This filter is combined with the delta-sigma transmitter to show the effective reduction of the out-of-band quantisation noise signals.

从十月革命到第二次世界大战爆发,苏联将南侧三个邻国作为中东地区的重点国家。第二次世界大战期间,苏联在中东一边清除德国势力,一边扩大在阿拉伯国家的影响。1955年苏东集团向埃及提供武器以及1956年苏伊士运河战争的爆发标志着美苏在中东对峙的正式形成。从1956年到1976年,苏联依托以埃及为核心的阿拉伯共和制国家与美国在中东展开对抗。随着1976年苏联与埃及关系的破裂以及随后一系列政策失误,苏联在中东的影响力日渐萎缩。苏联解体后,俄罗斯在中东的影响力由于外交政策的前后不连贯出现全面萎缩。2000年开始,俄罗斯在中东推行全方位外交以恢复和扩大影响力,2011年中东变局的爆发推动俄中东政策出现更为积...

基于细观力学复合球模型研究了含非均匀界面相球形颗粒填充复合材料的有效比热和其他热弹性性质,讨论了界面相性质沿径向的分布对有效性质的影响。首先,将不均匀界面相沿径向离散为多个同心球壳,假设每个球壳内材料性质是均匀的,不同球壳内的材料性质沿径向满足一定的分布。基于上述离散模型,利用含界面相的复合球模型,推导了复合材料的有效比热及有效体积模量、有效热膨胀系数的数值求解表达式。预测的有效热膨胀系数与实验结果吻合良好。另外,结果表明,界面相弹性模量和热膨胀系数的径向分布均对有效比热有较大的影响;而有效热膨胀系数虽然与界面相的模量和热膨胀系数都有关,但只有界面相热膨胀系数的径向分布对其影响较大。

提出了一种新的细观模型用以反映含连通开孔的饱和孔隙介质的结构特性。将流体作为基体,以取向随机分布的长柱形固体作为等效夹杂,利用Mori-Tanaka方法求解了饱和孔隙介质在排水和不排水状态时的有效弹性模量。该模型预测枫丹白露砂岩等岩土类饱和孔隙介质的有效弹性性质与实验相符很好。

本文用边界元方法求解颗粒填充复合材料的变形和界面分离问题,采用多子域法实现颗粒和基体之间的界面连续和分离条件,并采用主从自由度法(Master-Slave Elimination)[1]求解了界面从完美结合到分离的过程。算例表明,边界元法在此类问题中具有精度高和容易实施的优势。

阿富汗战争即将结束,有必要研究这场战争的历史影响。本文认为,这场以反恐为开端的战争同时也是一场政权更迭战争。推翻塔利班政权、通过新宪法、确立新的国体和政体,是战争最重要的产物。阿富汗塔利班作为反叛力量及其同跨国激进极端主义力量的联手、卡尔扎伊政权合法性缺失、美国—巴基斯坦—阿富汗之间错综复杂的关系,以及美国推动建立的阿富汗问题若干多边机制、地区大国介入阿富汗等,一系列源自于战争、政权更迭和地缘政治交互作用的产物,将对阿富汗和中南亚地区未来产生深远影响。

This paper proposes an energy recovery rectifier suitable for the use in outphasing and/or linear amplification with nonlinear components (LINC) transmitters. The proposed application oriented rectifier consists of a high-efficiency resistive rectifier and a stepped-impedance resonator (SIR) which stores the energy in order to reduce load sensitivity of the circuit. The rectifier is designed including harmonic frequency control to improve conversion efficiency and to provide a resistive input impedance at the fundamental frequency. The proposed rectifier has been implemented in hybrid technology. The fabricated circuit provides peak RF-to-DC efficiency of 73.5 % at 2.3 GHz and more than 60 % over a dynamic range of 8 dB. Furthermore, measurements show good agreement with simulation results.

This paper presents a dual-band rectifying circuit for wireless power transmission working at 2.45 GHz and 5.8 GHz. A modified dual-band matching network is adopted to realize the highly efficient dual-band rectifier. Source-pull simulations are performed, to determine the proper impedances at the two different frequencies. The proposed dual-band rectifier has been implemented and the measurements show good agreement with simulation. With a dual-band input matching network, the measurement results for an input power level of 10 mW show peak RF-to-DC efficiencies of 66.8 % and 51.5 % at 2.45 GHz and 5.8 GHz respectively.