一种应用于TD-LTE通信终端的天线设计与研究

运用传统的缝隙刻蚀技术与短路针加载技术,设计了一种构造简单的普通微带天线。同时将由微带线、三角形开口谐振环和缺地陷结构组建的超介质覆层加载到普通微带天线上方,构建形成一种基于超介质覆层的微带天线。MATLAB和HFSS联合仿真结果表明,超介质覆层在1-3GHz频段内具有负等效介电常数和负等效磁导率的特性。与普通微带天线相比,基于超介质覆层微带天线工作频带由原来的1.88-1.92GHz、2.6-2.65 GHz分别扩展为1.86-1.91GHz、2.57-2.64GHz,增益的最小增幅达到0.02d B。设计的超介质微带天线的工作频段和增益均满足了TD-LTE(1.880-1.900GHz、2.575-2.635 GHz)通信要求,其扩频手段和提高增益的方法也为设计性能更为优良的TD-LTE天线提供了一种参考思路。     

Ti-6A1-4V表面激光熔覆钛基复合涂层的微观组织及形成机制

Titanium matrix composite coatings were fabricated on Ti-6A1-4V substrate by laser cladding using powder mixtures of Ti Cr3C2 and Ti TiB2, respectively. The chemical compositions and mi-crostructures of the coatings were analyzed using scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). Microhardness was measured by a microhardness tester. The results showed that Cr3C2 particles were dissolved and deposited to form dendritic TiC in the upper section and spherical grain TiC in the bottom of Cr3C2 Ti coating. Most of TiB2 was dissolved in the molten pool by laser irradiation, then formed TiB with fine needles and coarse needles in the TiB2 Ti coating. A few quasi-melted TiB2 particles with irregular shape at the bottom of the coating were observed. The average microhardnesses were approximately HV850-V1000, HV800-V1050 in the Cr3C2 Ti and TiB2 Ti coating, respectively, which were 2-3 times higher than that of Ti-6A1-4V substrate.     

High-power superfluorescent source of Yb^3＋ -doped double-cladding photonic crystal fiber

A new type of high-power broadband superfluorescent source of Yb^3＋ -doped double-cladding photonic crystal fiber is reported experimentally, which is pumped at 976 nm by a high-power laser diode with the end-coupling method. We have obtained a smooth broadband output of superfluorescence The maximum output power is 1.649 W with a slope efficiency of 56.7%. The 3 dB bandwidth is 22.4 nm To the best of our knowledge, this is the first report about SFS with such high output power of 1.649 W.     

钢用硬质覆层材料的显微结构分析

用反应烧结法在A3钢表面制备了三元硼化物基硬质覆层材料YF-1，其硬度可达82～90HRA。用扫描电镜（SEM）、X射线衍射（XRD）和电子探针（EPMA）进行的显微结构研究结果表明：YF-1的表面硬质覆层主要是由三元硼化物基硬质相Mo2FeB2和铁基粘结相a-Fe组成，硬质相分散均匀。在硬质覆层和A3钢的界面存在明显的元素扩散，界面结合良好，界面结合强度高。     

激光熔覆层开裂行为的影响因素及控制方法

激光熔覆层开裂是影响覆层质量最主要的因素,特别是厚覆层。选用５ｋＷ 横流ＣＯ２ 激光器对各种不同材料和零件进行厚覆层激光熔覆,实验、检测和使用的效果说明：激光熔覆层开裂主要与激光系统参数、工艺处理条件、覆层材料、基体状况等四个方面有关。分析了熔覆层的开裂行为,并介绍了几种控制方法。     

基于进化神经网络的激光熔覆层质量预测

为了有效地控制激光熔覆层质量,采用反向传播(BP)算法建立了激光熔覆层质量(熔覆层宽度、熔覆层深度和稀释率)随激光功率、光斑直径和扫描速度变化的进化神经网络预测模型。针对BP算法存在收敛速度慢、容易陷入局部极小值及全局搜索能力弱等缺陷,采用遗传算法训练BP神经网络,取代了一些传统的学习算法,设计了基于进化神经网络的学习算法。经过理论分析和实验验证,在神经网络的输出端得到期望的线性输出,并在训练样本之外,选取了5组工艺参数检验神经网络模型的可靠性,预测结果与相应的实验结果的最大相对误差为2.14%。结果表明,运用该模型可以方便、准确地选择激光工艺参数,提高激光熔覆层的加工质量。     

送粉激光熔覆WC陶瓷层的高温组织与性能

实验研究了Co基自熔合金、Ni基自熔合金+WC、Co基自熔合金+WC激光熔覆层在不同温度下的显微组织和各种化合物的硬度,结果表明三种材料在相同激光熔覆工艺参数下获得的熔覆层的高温显微组织、性能存在很大的差异,Ni基自熔合金+WC在700℃时硬度开始显著降低且显微组织发生很大变化,而Co基自熔合金和Co基自熔合金+WC在700℃时才开始发生变化且变化幅度较小。同时证明WC在加热过程中硬度没有显著降低。实验结果对获得具有抗高温粘着磨损的激光熔覆层有重要的理论和实际意义。     

用于偶极子天线的高增益异向介质覆层设计

分析了基于金属柱阵列的高增益异向介质覆层,将偶极子的增益由2.15dB提高到14.5dB,且具有主瓣窄、副瓣电平低的特点.并提出利用PCB印制板工艺腐蚀出带状金属条替代金属柱制作异向介质覆层以减轻重量,便于加工.该结构同样能极大提高增益,且更具有工程实用性.