具有宽频特性带通频率选择表面的设计

基于高阶特性的频率选择表面（FSS）有更好的带宽展宽性,提出了利用高阶带通FSS的方法 来 设计具有宽频特性的带通FSS。设计了一种基于圆结构具有五层结构的FSS,利用仿真软件对 FSS单元进行计算和分析。分析结果表明：此五层结构的FSS具有三阶单通带性能,其绝对 带宽达到6.07 GHz,相对带宽达到72%,通带平稳光滑,通带内插损小,对不同角 度、 不同极化方式入射的电磁波保持很好稳定性。此FSS具有很稳定的宽频特性,从而验证了此 宽频带通FSS设计方法的可行性。     

一种Ku波段/毫米波波段独立双通带微型化频率选择表面

为了满足现代通信设备多频带及集成化要求,基于三屏耦合机制和双屏谐振机制,设计了一种在Ku波段和毫米波波段具有独立双通带、微型化和"矩形化"滤波特性的频率选择表面(FSS).根据物理结构分析了其作用机理,并采用矢量模式匹配法计算了其传输特性.结果表明:该结构单元尺寸仅为第一通带谐振波长的0.104倍,具有微型化特征;第二通带在42.6 GHz和49.6 GHz时出现双峰,在47.4 GHz时出现-0.828 dB的"浅谷",具有"矩形化"传输特性;两个通带间隔约30 GHz且相互独立,在0°~60°扫描范围内均具有良好的角度稳定性.这种多功能的FSS可以满足工程应用要求.     

一种新型双通带频率选择表面

针对多通带频率选择表面(Frequency Selective Surface,FSS)带宽较窄的问题,基于方环形缝隙及其互补结构设计了一种工作于X/Ku波段的双通带频率选择表面。在单层介质两侧加载互补贴片的基础上提出了两层介质加载三层金属贴片结构,得到了一个一阶通带和一个二阶通带,二阶通带两个极点的反射率达到–30 d B以上,实现了宽频特性。仿真结果表明:该频率选择表面具有很好的角度稳定性和极化稳定性,两个通带的相对带宽分别达到了13.87%和28.57%,第二通带带内平坦,中心插损很小,整体带外抑制明显,综合性能较好。     

一种新型扇形环状频率选择表面的设计

通过在矩形环为基本单元结构的基础之上设计了一种新型双频双极化低通高阻型频率选择表面（Frequency Selective Surface,FSS）。此结构将普通矩形环的每条边顺时针延长,再沿贴片的四周开槽矩形孔径后两边加载介质板的多层结构,实现了Ka波段带通、W波段带阻的空间滤波特性。经过电磁仿真软件HFSS的仿真与优化,所设计的新型扇形环状FSS结构在35GHz谐振频率处,插损为0.02dB,-0.5dB通带衰减带宽为5.85GHz;在94GHz谐振频率处,反射系数为-54.57dB,-20dB阻带带宽为4.29GHz,且在入射角0°~30°范围内具有良好的极化稳定性和角度不敏感性。     

贴片-网栅级联二阶宽带带通频率选择表面设计

采用贴片谐振型与网栅感性型单元级联组合的方法,设计了一款二阶宽带带通频率选择表面(FSS),在0°～45°入射角范围内,通带为8.0～12.6 GHz,覆盖X波段,平均插入损耗小于1dB.该结构由两层贴片型单元阵列和一层感性金属网栅级联组成,优化确定的FSS单元尺寸为0.136 λ×0.136 λ(λ为工作波长).设计...     

基于频率选择表面的宽角扫描阵列

设计并加工了一种基于双层频率选择表面(frequency selective surface, FSS)的一维Vivaldi阵列天线.首先采用周期边界条件分析无限大阵列中的单元特性, 利用等效传输线原理和广义散射参数矩阵来设计优化加载在Vivaldi阵列上方的介质宽角匹配层.然后, 在所加载的双层介质匹配层表面直接印制FSS结构使阵列扫描特性得到极大改善.仿真和实测结果表明, 一维Vivaldi阵列中心单元在7~12 GHz的有源驻波比均小于2.5, 在8~10 GHz波束扫描范围能够达到±60°.仿真结果还表明:采用双层FSS结构的Vivaldi阵列与未加载匹配层的Vivaldi阵列相比, 在7~11.5 GHz增益有2~4 dB的提高; 同时在扫描至±60°时, FSS结构的加载使得阵列在对应扫描角下的交叉极化下降了5~10 dB.     

FSS 天线罩的RCS 测量与分析*

FSS在天线RCS减缩方面起了重要作用。针对一种锥形的带通FSS天线罩,设计了RCS测量载体,为了凸显FSS天线罩的透波特性和低于通带处的带外隐身性能,用双面角反射器模拟天线舱内天线系统产生的强散射,对FSS天线罩的传输特性和RCS性能进行了测量。结果表明,FSS天线罩在通带内有较好的透波特性,通带内的频点f0处RCS与测量载体的RCS曲线有相似形状,呈现出介质罩的透波特性。FSS天线罩在低于通带频点f1处透波特性衰减至约-15d B,通过统计鼻锥前向-60°~+60°范围内的RCS均值,FSS天线罩的RCS与载体相比较,RCS减缩均值达到-20d B左右,具有明显的减缩效果。     

具有寄生通带抑制的E波段双工器

通过精密机加工技术制造了一种具有寄生通带抑制的E波段波导双工器。其仿真性能在71~76 GHz,81~86 GHz通带内插入损耗小于1 dB,通带隔离度大于60 dB;在142~152 GHz,162~172 GHz二倍频通带内抑制大于20 dB。实测结果显示该双工器通带内插入损耗最差为0.7 dB;通带隔离度优于60 dB;二倍频处抑制大于20 dB。仿真设计与实测结果高度吻合。该双工器的优异性能确保其适用于5 G通信E波段回传网络中。     

太赫兹波段复合型FSS带通滤波器的分析与设计

利用谱域法对频率选择表面 (frequency selective surface,FSS) 结构进行理论分析,设计了中心频率为0.338 THz工作在大气通信窗口的复合型FSS带通滤波器。该滤波器是对圆环槽单元滤波器进行改进,增加了三极子单元,通过研究结构参数对滤波性能的影响关系,进行结构优化。实验表明,该滤波器综合滤波性能更好,3 dB带宽可以达到69.5 GHz,回波损耗小于-13.46 dB,带内插入损耗小于0.45 dB,带内纹波低到0.1 dB,且通带平坦,有较好的带外抑制和矩形系数,边带比较陡峭。同时该滤波器在不同极化波和相同极化波不同入射角度入射时都有很好的频率稳定性,能有效地用于太赫兹通信。     

新型差分三通带滤波器设计

基于T型支节加载均匀阻抗谐振器,设计了一款新型小型化差分三通带滤波器,并对该滤波器进行了改进设计。所设计滤波器的三个通带中心频率分别为2,6.4,9.2 GHz。-3 dB相对带宽分别为20%(1.85~2.25 GHz)、7%(6.21~6.71 GHz)、5%(8.98~9.44 GHz),通带内插入损耗小于1.5 dB。为了实现良好的共模抑制,在该滤波器中心对称处增加了开路支节,高频处的共模抑制得到显著提高。该滤波器结构简单,能够实现良好的性能,仿真结果与理论分析一致。     

A Method for Computing the 2-D Stability Margin Based on a New Stability Test for 2-D Systems

In this paper, a new method to compute the stability margin of 2-D (two-dimensional) discrete systems is considered. The method is based on a recently proposed 2-D stability test by the author. Illustrative examples are also included.     

Stability Of Non-Fullerene Electron Acceptors and Their Photovoltaic Devices

Non-fullerene electron acceptors (NFAs) are recognized as “rising star” in recent years in the organic solar cells (OSCs) community. In contrast to the traditional fullerene electron acceptors, NFAs promise superior feasibility in molecular design with tunable optoelectronic properties, experiencing unprecedented development in the last 5 years with maximum achievable power conversion efficiencies over 18% are acquired in NFA based OSCs. Nevertheless, the stability of NFAs and their OSCs is still problematic and not well understood, and is regarded as the bottleneck toward the commercialization of NFA based OSCs. In this review, recent advances and current understanding of the stability of NFAs and their corresponding OSCs are presented. Specifically, three key factors, including chemical-, photon-, and thermal-, induced degradations in NFAs are analyzed and summarized, with approaches to enhance the stability suggested. This is followed by the discussion of shelf and operational stability of NFA based OSCs, with highlights of operational stabilities in inert, ambient, indoor, and outdoor conditions. It is envisaged that operational lifetime of over 20 years in real world is achievable via the joint efforts from material design, morphology control, interfacial engineering, and encapsulation technology.     

Robust Stability of Multivariate Polynomials. Part 1: Small Coefficient Perturbations

This paper presents a detailed analysis of some classes of stable multivariate polynomials. The main aim of the analysis is to give conditions under which polynomials preserve stability when they are subjected to small coefficient variations. The maximal class of such polynomials is introduced. Some basic properties of polynomials from this class are obtained.     

Stability of Multivariate Polynomials,Part 4: Conic Sets

Robust stability of conic sets of multivariate polynomials is the main topic of the paper. Stability and semistability conditions for a cone starting at the origin are obtained along with stability conditions for a cone of the form p(s) + K, where p(s) is a given polynomial and K is a cone starting at the origin. Some new results on convex directions for mulivariate polynomials are also presented.     

Robust Schur Stability of Polynomials with Polynomial Parameter Dependency

The paper considers the robust Schur stability verification of polynomials with coefficients depending polynomially on parameters varying in given intervals. A new algorithm is presented which relies on the expansion of a multivariate polynomial into Bernstein polynomials and is based on the decomposition of the family of polynomials into its symmetric and antisymmetric parts. It is shown how the inspection of both polynomial families on the upper half of the unit circle can be reduced to the analysis of two related polynomial families on the real interval [–1,1]. Then the Bernstein expansion can be applied in order to check whether both polynomial families have a zero in this interval in common.     

A Note on the Internal Stability for 2-D Singular Discrete Systems

In this paper, the conjecture proposed by Zou and Campbell [Multidimensional Systems and Signal Processing, no. 11, 2000, pp. 321–338] on the internal stability for 2-D linear discrete systems is proven. It reveals that the internal stability is only dependent on the asymptotic property of the system states. This is very significant for the simplification of the definition of internal stability and hence to make it more comprehensible.     

Design consideration of the thermal and electro stability of multi-finger HBTs based on different device structures

The thermal and electro stability of multi-finger heterojunction bipolar transistors (HBTs) with different structures were analyzed and discussed simultaneously. The thermal stability of the devices with different layout struc-tures was assessed by the DC-Ⅳ test and thermal resistance calculation. Their electro stability' was assessed by the calculation of the stability factor K based on the S parameter of the HBT. It is found that HBTs with higher thermal stability are prone to lower electro stability. The trade-off relationship between the two types of stability was explained and discussed by using a compact K-factor analytic formula which is derived from the small signal equivalent circuit model of HBT. The electro stability of the device with a thermal ballasting resistor was also discussed, based on the analytic formula.     

基于不同器件结构的多指HBT热电稳定性研究

本文基于不同的器件结构同时对多指HBT器件的热稳定性和电稳定性进行了分析和讨论。通过直流测试、热阻计算以及基于S参数的稳定性因子K的计算,评估了两个不同版图结构的HBT器件的热稳定和电稳定特性,实验结果表明高热稳定性的器件具有低电学稳定性。引入一个基于小信号等效电路模型的K稳定因子公式对实验结果进行了合理解释。同时基于该公式,具有热镇流电阻结构的器件稳定性也进行了讨论。     

2.4GHz 0.35-μm CMOS全集成线性功率放大器设计

片上系统射频功率放大器是射频前端的重要单元.通过分析和对比各类功率放大器的特点,电路采用SMIC0.35-μm CMOS工艺设计2.4 GHz WLAN全集成线性功率放大器.论文中设计的功率放大器采用不同结构的两级放大,驱动级采用共源共栅A类结构组成,输出级采用共源级大MOSFET管组成.电路采用SMIC 0.35-μ...     

一种具有弱条件稳定的分裂式FDTD方法

近十几年来,时域有限差分算法(FDTD)得到了快速发展,然而该算法一直受稳定性条件(CFL)的限制.为突破这一限制一种具有弱条件稳定(WCS)的FDTD算法得到发展,提高了FDTD的计算效率,但陔方法存在精度不高的缺点.文中针对弱条件稳定FDTD方法精度不高这一弱点,提出了一种新的算法,该算法具有弱条件稳定性,且计算速度比ADI-FDTD方法有显著提高,并通过数值实验验证了该方法的准确性和有效性.