Design of a compact orthogonal fed self‐diplexing bowtie‐ring slot antenna based on substrate integrated waveguide

In this article, a novel design of compact cavity‐backed slot antenna based on substrate integrated waveguide (SIW) technology is presented for dual‐frequency communication services. A single layer printed circuit board is applied to implement the proposed antenna. The bowtie‐ring slot engraved on the SIW square cavity is excited using two orthogonal microstrip feed lines to operate at two distinct frequencies (6.62 GHz and 11.18 GHz). The proposed antenna allows each of these frequencies to be designed independently. A prototype of the proposed cavity‐backed antenna that radiates at both 6.62 GHz and 11.18 GHz is fabricated and measured. The port isolation better than 29.3 dB is achieved by utilizing the transmission zeros (TZs), which are produced due to the orthogonal feed lines, TE₁₁₀ mode and coupling between the TE₁₂₀ and TE₂₁₀ modes. The measured peak gains of the proposed diplexing antenna are 5.77 dBi and 5.81 dBi at lower and upper resonating frequencies, respectively. The proposed dual‐frequency antenna exhibits the front‐to‐back‐ratio (FTBR) and cross‐polarization level greater than 26 dB and 21 dB, respectively, at both resonating frequencies.     

Wideband bow‐tie antenna with increased gain and directivity by using high impedance surface

Metamaterial surfaces offer a wide range of advantages in terms of antenna design. One such metamaterial is designed to capture the benefits of both high‐impedance surfaces as well as artificial magnetic surfaces. The confluence of both these properties delivers an added advantage to planar antennas by delivering high gain and directivity simultaneously. Bidirectional radiation pattern has been transformed to a directional radiation pattern by placing the metamaterial as substrate beneath the antipodal bowtie antenna. In addition, zero separation between the antenna and metasurface ensures low profile. The proposed design has been verified both by simulation and measurement which have shown an improvement on gain of 3.2 dBi with an almost steady gain response inside the resonating band of the antenna which lies between 12 and 16 GHz.     

Using eigenvectors of perturbed and collapsed adjacency matrices to explore bowtie structures in directed networks

The bowtie structure can illustrate not only the accessibility of the World Wide Web, but also the reachability of other directed networks. In this paper, we use the principal eigenvectors of the adjacency matrix with the unique largest eigenvalue to identify the strongly connected component of a directed network and fit the network into the bowtie structure. To ensure that the largest eigenvalue is unique, we add a little perturbation to the matrix before the eigen analysis. After the revelation of the bowtie structure centered on the strongly connected component with the largest unique eigenvalue, a directed network may have other bowtie structures centered on strongly connected components with smaller eigenvalues. To reveal other bowtie structures, we collapse the perturbed matrix by aggregating nodes of the strongly connected component with the largest eigenvalue into a supernode. Hence, the principal eigenvectors of the perturbed and collapsed matrix can be used to reveal the bowtie structure centered on the strongly connected component with the second largest eigenvalue. Furthermore, repeating the process of collapsing a strongly connected component and finding principal eigenvectors of the perturbed and collapsed matrix, we can reveal all the bowtie structures of a directed network.     

Fast bowtie effect elimination for MODIS L1B data

The bowtie effect refers to geometry distortions for the moderate resolution imaging spectrum-radiometer(MODIS) level 1B(L1B) data.Till now,to eliminate the bowtie effect,numerous methods are proposed.However,most of them have limitations in computation efficiency.Through a comparative study of existing methods,this article puts forward a fast method to eliminate the bowtie effect using the ephemeris data.In this method,the rough positions of overlapping data are first detected.Because of the influence caus...     

多频印刷单极子天线的设计

〗提出一种应用于2.4/5.2/5.8 GHz WLAN和2.5/3.5/5.5 GHz WiMAX共面波导印刷单极子天线。该天线结构紧凑,可以方便地植入无线通讯设备中,有较强的实用性。此天线由50 Ω的微带传输线通过共面波导馈电的方式对具有对称结构的蝶型贴片馈电。在设计中,通过开缝和添加倾斜微带条,使天线获得的阻抗带宽可以覆盖WLAN和WiMAX频段。天线的总体尺寸为30 mm×32 mm,其结构紧凑、便于集成和加工,适合无线通讯应用。     

Boosting Perovskite Photodetector Performance in NIR Using Plasmonic Bowtie Nanoantenna Arrays

Triple‐cation mixed metal halide perovskites are important optoelectronic materials due to their high photon to electron conversion efficiency, low exciton binding energy, and good thermal stability. However, the perovskites have low photon to electron conversion efficiency in near‐infrared (NIR) due to their weak intrinsic absorption at longer wavelength, especially near the band edge and over the bandgap wavelength. A plasmonic functionalized perovskite photodetector (PD) is designed and fabricated in this study, in which the perovskite ((Cs_0.06FA_0.79MA_0.15)Pb(I_0.85Br_0.15)₃) active materials are spin‐coated on the surface of Au bowtie nanoantenna (BNA) arrays substrate. Under 785 nm laser illumination, near the bandedge of perovskite, the fabricated BNA‐based plasmonic PD exhibits ≈2962% enhancement in the photoresponse over the Si/SiO₂‐based normal PD. Moreover, the detectivity of the plasmonic PD has a value of 1.5 × 10¹² with external quantum efficiency as high as 188.8%, more than 30 times over the normal PD. The strong boosting in the plasmonic PD performance is attributed to the enhanced electric field around BNA arrays through the coupling of localized surface plasmon resonance. The demonstrated BNA‐perovskite design can also be used to enhance performance of other optoelectronic devices, and the concept can be extended to other spectral regions with different active materials.     

领结分析在收球系统安全管理中的应用

目前国内领结分析流程并不统一,因此本文对于领结分析的流程进行了梳理,明确了领结分析所需的步骤以及各步骤对应的内容。收球系统在油气田工程及化工领域应用广泛,此系统中包容的高压介质或废弃物料都可能对人员及设备造成伤害。为了能够更好对收球系统进行安全管理,本文使用领结分析对收球系统中潜在的危害进行分析。收球系统中可能会出现"高压气体"、"可燃气体与液体"和"自燃物"这三类危害,利用领结分析的方法分别对上述3种危害下的原因、后果及保护屏障（预防屏障及减缓屏障）进行分析。通过领结分析可以将控制潜在危害的屏障进行有效梳理,对可能的原因及后果进行分析;能对其他安全评价工具所存在不足进行补充,并能为之后的风险管理提供直观的输入支持。     

一种蝶形平面超宽带(UWB)天线的设计

超宽带无线通信技术以其低功耗、高带宽、低复杂度等优点而倍受重视,使用蝶形结构设计了一种新的平面超宽带天线。该天线由同轴馈电,天线的制作是通过在介质基板上下面上分别印刷一个半圆形金属,在上层刻蚀掉2个正方形图案,下层刻蚀掉2个半圆形图案实现。仿真和实物实测结果都可以证实,天线的工作频带为3.1~10.6 GHz,有很好的全向辐射方向图和良好的线性相位响应。因此,该天线的特性能够满足超宽带的要求,可用于无载波超宽带无线数据通信系统。     

亚毫米波蝶形天线的设计

讨论了位于无限介质空间的蝶形天线理论和方向图，对阻抗进行了计算机辅助分析与计算．文中还给出了０．３３７ｍｍ蝶形天线的设计结果．     

基于不均匀超介质的宽带高增益天线研究

提出了一种由双层不均匀频率选择性表面(FSS)结构组成的领结型高增益天线,对其进行了仿真分析。结果显示该天线在不加外匹配网络情况下,|S11|≤–6 dB的阻抗带宽可达到72%,同时有很好的辐射方向图。与均匀频率选择性表面组成的天线相比较,该不均匀性天线带宽为均匀频率选择性表面组成的天线的1.5倍,并且仍然保持低轮廓。这种特性适用于点对点弱信号通信。