Broadband Analysis of Holographic Power Combining Circuits

Holography is a promising technique for power combining applications in the frequency range of short millimeter and submillimeter waves. In this paper, quasi-optical holographic power combining circuits are investigated. An equivalent network is utilized which rigorously models horn arrays and biperiodic dielectric structures in order to design computer-generated holograms. We apply the network model to a 5-element quasi-optical power combiner and demonstrate its capability. The hologram is designed for 150 GHz and has an efficiency of 92.5 % with a 90 % bandwidth of 5.3 %. With the aid of a broadband waveguide power divider and a vector field measurement system, the circuit is analyzed.     

新型圆锥加脊TEM喇叭天线的分析

ＴＥＭ喇叭是一种超宽带天线，在瞬态场和超宽带雷达的研究中具有良好的理论和应用价值，本文首先应用格林函数法分析了壁无限薄的圆锥加脊ＴＥＭ喇叭天线，计算了喇叭上的电荷分布及截面阻抗，并分析这种ＴＥＭ喇叭天线在不同辐射方向的波形，结果表明这 超宽带和波形保真性。     

Two-Step Structure Phase Transition,Dielectric Anomalies,and Thermochromic Luminescence Behavior in a Direct Band Gap 2D Corrugated Layer Lead Chloride Hybrid of [(CH3)4N]4Pb3Cl10

A direct band gap 2D corrugated layer lead chloride hybrid, [(CH₃)₄N]₄Pb₃Cl₁₀ ( 1 ), shows analogous topology to the {Mg₃F₁₀⁴⁻}_∞ layer in Cs₄Mg₃F₁₀, and with the (CH₃)₄N⁺ cations locating in the inorganic layer voids and between the interlayers. Two reversible structural phase transitions occur in 1 at 225/210 K and 328/325 K upon heating/cooling, respectively. On going from the low- to intermediate-temperature phase, the space group changes from P2₁/c to Cmca, and the crystallographic axis perpendicular to the layers is doubled with the order–disorder transformation of (CH₃)₄N ⁺ cations between the interlayers. The intermediate- and high-temperature phases are isomorphic with similar cell parameters and packing structure; their main difference concerns the disorder degree of the (CH₃)₄N ⁺ cations between the interlayers. The two-step structural phase transitions lead to dielectric anomalies around the corresponding T_c. Interestingly, 1 shows multiband emission, originating from the recombination of exciton and emission of defects. Moreover, 1 exhibits divergent thermochromic luminescent features around the T_c on the intermediate to low temperature transition.     

压力传感器封装中的波纹膜片结构研究

针对压力传感器隔离式封装中的波纹膜片这一关键部件,采用有限元分析的方法研究了波纹膜片的厚度、波纹深度和波纹数目分别对最大压力约0.1 MPa下的压力传感器输出信号的影响,优化了波纹膜片结构的参数选择。通过对封装了不同波纹膜片的样品的测试与比较表明,较小的膜厚与波纹深度、较多的波纹数目有助于提高压力传感器的性能,从而验证了波纹膜片结构优化的正确性。     

EAST 装置电子回旋共振加热系统波纹圆波导研究*

在EAST装置上正在建设140GHz/4MW/1000s电子回旋共振加热(ECRH)系统,单个回旋管输出的1MW功率通过波纹圆波导传输到天线聚焦镜上,然后经天线反射镜进入等离子体。运用表面阻抗法对波纹圆波导进行了理论分析,针对EAST装置ECRH系统需求的140GHz波纹圆波导进行了设计研究,所设计的波导传输模式为HE11模,具备1MW连续波运行能力且欧姆损耗低于0.02d B/100m,同时分析了HE11模在波导口外辐射模式及其与TEM00模耦合特性。     

一种考虑互耦的脉冲天线阵列快速计算方法

基于有源单元方向图思想,提出了一种可用于计算脉冲天线阵列时域辐射场的快速方法.该方法在考虑单元间互耦的情况下,将大型阵列的时域辐射场计算问题转化为一个小型阵列的计算问题,大大地减少了计算量.采用文中的阵列综合方法,结合有限积分法软件,仅对一个5×5元阵列进行模拟,即可推算出大型阵列的远场方向图,其计算时间不超过全波模拟时的十分之一.计算结果与仿真软件的仿真结果吻合较好,验证了方法的正确性.     

一种高效率的四脊喇叭馈源

以天线口径效率为目标,研究了四脊喇叭口径对馈源波束等化、波束宽度恒定和天线口径效率等性能的影响,得到了一种3∶1带宽高效率圆四脊喇叭馈源的设计。该馈源在整个频带内具有较低的电压驻波比,三个主平面的主极化方向图波束等化较好,-10d B波束宽度基本恒定,且天线口径效率达到55%以上。     

角锥喇叭天线制造工艺

介绍了不同频段、不同尺寸的角锥喇叭天线成型方法,针对传统成型方法一些不足之处以及产品轻量化设计的要求,对喇叭的成型方法又提供了三种新的制造工艺,即电子束焊、真空钎焊及碳纤维复合材料成型法.     

基于同步辐射原位CT的水牛角结构性能关系研究

为探究水牛角的结构性能关系,基于上海同步辐射光源搭建了高分辨原位CT系统,对水牛角角鞘进行初始表征和准静态压缩下的实时表征,并通过Top-Hat方法提取了角鞘内孔洞三维形貌.结果显示,水牛角角鞘孔隙率在1％左右,椭圆柱状孔洞沿牛角生长方向排列成线,首尾相连却并未连通,均匀分布在波浪状片层之间.孔洞特征椭球的轴长分布满足...     

Intensification of delignification of Tectona grandis saw dust as sustainable biomass using acoustic cavitational devices

Delignification of sawdust was studied using ultrasound assisted alkali peroxide approach using longitudinal horn for the first time and the efficacy compared with more commonly used configurations of ultrasonic reactors. Comparison with the conventional approach based on stirring has also been presented to establish the process intensification benefits. Effect of different operating parameters such as sodium carbonate concentration (0.1, 0.15, 0.2, 0.25 M), hydrogen peroxide concentration (0.2, 0.4, 0.6, 0.8, 1 M) and biomass loading (2, 4, 6, 8, 10 wt%), on the efficacy of lignin extraction has been investigated for different ultrasonic reactors. The optimum conditions for probe type ultrasonic horn were established as 150 W, 50% duty cycle and 80% amplitude with optimum process conditions as Na₂CO₃ concentration as 0.2 M, H₂O₂ concentration as 1 M, biomass loading of 10 wt% and operating time of 70 min. Longitudinal horn resulted in best efficacy (both in terms of yield and energy requirements) followed by ultrasonic horn and ultrasonic bath whereas the conventional approach was least effective. The obtained lignin was also analyzed using different characterization techniques. The presence of peaks at wavelength range of 875–817, 1123–1110, and at 1599 cm⁻¹ for the extracted sample confirmed the presence of lignin. Increase in the crystallinity index of the processed sample (maximum for longitudinal horn) also confirmed the lignin removal as lignin is amorphous in nature. Overall it has been concluded that ultrasound can be effectively used for delignification with longitudinal horn as best configuration.