Optimization of PZT-Based Radio-Frequency Filters

Analytical solutions are presented for the wave equation for the electrode-piezoelectric-electrode sandwich structure in film bulk acoustic resonators (FBAR). The impedance for lead-zirconate-titanate (PZT)-based FBAR was derived using the proper boundary conditions and material parameters. A method is presented to adjust the resonant frequency based on the process and material properties. Ferroelectric-based radio-frequency filters were designed using FBARs. An accurate result is given for the filter impedance which can be used for other piezoelectric devices.     

广州亚运会我国与亚洲主要国家田径竞赛实力比较分析

文中运用文献资料法,数理统计法,比较法等方法分析我国田径现状以及亚洲各主要国家的田径竞技实力。知己知彼方能百战不殆,为我国田径下一步的发展提供参考。     

Surface Micromachining of Bulk Acoustic Wave Filters

The most common typical bulk acoustic wave (BAW) filters are fabricated using bulk micromachining technology, but they have several disadvantages. This paper describes a new structure for front end passband BAW filters manufactured using surface micromachining. Porous silicon is used as a thick sacrificial layer. The structure reduces the influence of the support film on the filter to improve the VLSI compatibility as well as the filter quality. The cross-talk between resonators with different frequencies can be dramatically reduced by using resonators with a self-supporting structure.     

基于螺旋CT的高温气冷堆石墨构件及碳砖缺陷检测方法

石墨构件和碳砖是构成高温气冷堆(high temperature gas-cooled reactor, HTGR)堆芯及反射层的重要材料,在其生产运输过程中,不可避免会出现缺陷,当使用了有较为严重的缺陷的石墨构件或碳砖进行建设时,将对反应堆造成重大安全隐患。目前传统检测方法主要是基于目视的表面检查,无法检测其内部缺陷。该文提出了一种基于螺旋CT的石墨构件及碳砖检测方案,并采用数值模拟的方式,对大尺寸碳砖模体进行了螺旋CT重建,研究了不同螺距、旋转速度及不同重建算法对重建图像质量的影响。结果表明,螺距对重建图像质量影响较大,在螺距为0.8时可基本满足检测需求;旋转速度对图像质量影响相对较小;在较优参数下,采用CGLS重建算法,最小可检测至?2 mm的孔缺陷和宽1 mm的缝缺陷。该研究结果对螺旋CT石墨碳砖检测系统及检测方案的设计具有重要参考意义。