复合负泊松比蜂窝超结构板低频减振特性研究

为实现低频宽带减振,将星型蜂窝与内凹六边形蜂窝组合,形成复合负泊松比蜂窝结构.利用多物理场软件COMSOL Multiphysics通过施加Floquet周期性边界条件获得了复合蜂窝元胞的色散曲线,并计算有限周期结构的传输特性,验证色散曲线中带隙的存在.设计并制备了复合蜂窝超结构板样件,通过试验分析其弹性波激励下的响应,验证有限元分析结果.以低频宽带为目标,利用遗传算法对结构参数进行优化,在1000~2000Hz打开了多条宽频带隙,可以为带隙设计提供有益指导.最后,将地铁实车测试获取的地板振动频谱作为激励,对超结构的减振性能进行了仿真测试,结果表明,复合蜂窝超结构板能够有效衰减列车地板1000~2000Hz的振动峰值.     

基于CN-FDTD的新颖DGS带阻滤波器特性研究

缺陷接地结构(DGS)作为频率选择表面(FSS)的一类,在电磁领域应用广泛。提出了一种新颖结构单元的DGS频率选择表面,可以用来实现带阻滤波器(BEF)。Crank-Nicolson FDTD(CN-FDTD)是一种无条件稳定的FDTD,在时间步长取值远大于Courant-Friedrich-Levy(CFL)稳定性条件时,CN-FDTD仍然稳定而且可靠。利用CN-FDTD对该结构进行了精确的数值计算,研究了参数l、参数g和周期单元数n对这种带阻滤波器滤波特性的影响。随着参数l的增大、参数g的减小和周期单元数n的增大,带阻滤波器的滤波特性越好。这些有益的结论能为这种新颖DGS带阻滤波器的分析和设计提供有力的指导。讨论了CN-FDTD的误差项,随着时间步长的增大,其误差也会显著增大。     

方形环贴片双模微带带通滤波器的设计

提出了一种用阶梯型阻抗方形环谐振器构成的双模微带滤波器,该滤波器引入一个方形切角作为微扰,并采用输入/输出与谐振器直接馈电的方式。该结构的滤波器在通带两侧均产生了传输零点,使阻带抑制性提高。使用电磁仿真软件HFSS对滤波器进行仿真优化,结果表明,双模带通滤波器的中心频率在2.2 GHz处,通带内的最小插损为-0.47 dB,3 dB相对带宽为18.2%,仿真结果与实测结果基本一致。     

耦合微带滤波器的快速成型设计

本文首先介绍了传统的耦合微带带通滤波器的设计方法,然后提出了基于ADS仿真软件快速设计微带滤波器的方法,设计中对原理图和版图多次进行参数优化,最后参数仿真效果达到指标要求。和传统滤波器的设计方法相比,该方法的运用降低了电路设计的工作量,缩小了产品设计周期,提升了器件的性能,它对实际工程中设计微带滤波器有着很大的实用价值。     

新型光子晶体THz滤波器

提出了一种新型基于光子晶体的太赫兹滤波器,该滤波器在线缺陷中设计了由三个点缺陷构成的谐振腔,能够实现双波长的高效滤波功能。文中使用平面波展开法(PWM)分析了正方晶格光子晶体的带隙结构,并利用时域有限差分法(FDTD)研究了滤波器的一些性能指标。仿真结果表明,该新型滤波器能够把频率为3.413 THz和3.222 THz的太赫兹波滤出,并且具有滤波带宽窄、体积小等优点。     

基于混合CPW和微带结构的超宽带滤波器

提出了一种新型的混合共面波导和微带结构的超宽带带通滤波器。通过将中间微带替换成交指耦合线,在下通带边缘产生一个传输零点,使得滤波器的选择性得到极大提升。此外,引入了耦合短路枝节以进一步提升其选择性和带外特性。实测结果表明,提出的滤波器具有不错的带内和带外性能。其具有陡峭的选择性,尺寸紧凑(0.49λg×0.47λg),插入损耗低,且上阻带宽。该滤波器的相对带宽达123%(2.75~11.55 GHz),回波损耗优于15 dB。并且,最终的加工实测结果和仿真结果基本一致。     

平行耦合微带带通滤波器的设计与仿真

随着5G等无线通信技术的发展和应用,无线通信设备的高性能、微型化、低成本、便于设计等亮点受到了越来越广泛的关注。滤波器是无线通信系统的重要构成部分之一,其性能的优劣很大程度上决定了通信系统的工作性能。平行耦合微带滤波器具有体积小、光刻处理简单、成本低、精度高、易于集成、工作频率范围宽等优点。基于平行耦合微带线理论,设计了一款微带带通滤波器。该滤波器通带范围:f=3.0~3.1 GHz,频率通带带内插损<1 dB。使用ADS2008微波仿真软件对其进行了仿真与优化。仿真结果表明:该方法与传统的设计方法相比,不但可以大量减少工作量,缩短设计周期,并且能提高器件的准确性与稳定性。     

基于枝节加载多模谐振器的电调微波滤波器设计

针对认知无线电技术对射频微波滤波器的新要求,提出了一种基于枝节加载多模谐振器的电调微波滤波器。该电调微波滤波器由一个枝节加载微带多模谐振器和变容二极管组成,实现了滤波器的小型化。在分析枝节加载微带多模谐振器的基础上,通过在微带谐振器两端和加载枝节上加载变容二极管的方法,设计了枝节加载的电调多模微带谐振器,并提出了复杂微带谐振器谐振特性的分析方法。采用源和负载耦合的方法在通带右边引入一传输零点。通过在源和负载端放置耦合线的方法,提高了滤波器的通带选择性。针对滤波器带外衰减小的问题,引入一种新型的频变馈电结构,改善了滤波器的带外衰减特性。通过优化仿真确定了电调滤波器的尺寸参数。仿真验证了该滤波器的特性,当变容二极管的可调范围为2pf-10pf时,滤波器的频率可调范围为2.10GHz-2.40GHz,频率变化范围为300MHz。     

基于ADS的微带线带通滤波器的设计与优化

利用ADS(Advanced Design System)设计平行耦合微带线带通滤波器,为了缩短设计周期,提高微带线带通滤波器的性能,采用ADS中的无源电路设计向导工具,设计出了一种中心频率为3.0 GHz、带宽为60 MHz的平行耦合微带线带通滤波器。参数优化后进行电路版图仿真。仿真结果表明,该设计设计周期较短、方法切实可行,设计出的带通滤波器满足各项指标要求。     

梳状线可调带通滤波器的设计与仿真

针对现有的微带可调滤波器中心频率调节范围较窄的问题,依据梳状滤波器的原理和变容二极管的特性,设计出一种梳状线可调带通滤波器,经ADS仿真可得其中心频率可调范围达到0．49～5．08GHz、相对带宽仅为6．1％～9．4％,该梳状线可调带通滤波器具有中心频率调节范围很宽、结构简单、易于实现、易于扩展等优点,在工程上具有一定的推广应用价值。     

Miniaturized rectangular waveguide filters

Two types of miniaturized rectangular waveguide filters are presented. Miniaturization is achieved using the slow‐wave effect of electromagnetic bandgap (EBG) surfaces and the left‐handed properties of split ring resonators (SRRs). The proposed EBG waveguide bandpass filter performs passband in the frequency range, which corresponds to the waveguide with the lower recommended operating band consequently enabling significant miniaturization of the structure. The SRR‐loaded bandstop filter makes use of the effect imposed by left‐handed medium (LHM), which is created by a combination of SRRs and wireline on the dielectric slab. Both filters are designed, simulated, and tested. Experimental results of the SRR‐loaded bandstop filter are presented to demonstrate feasibility of the proposed structures. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Microwave dual‐band bandstop filter with improved spurious resonance behavior

A design technique to improve the spurious resonance behavior of dual‐band bandstop filters is presented. A compact dual‐band bandstop filter with two stop bands that can be controlled independently with improved passband frequency response is designed. The operational bandwidth of the proposed compact dual‐band bandstop filter is increased by pushing the first spurious resonance from being about twice the resonance frequency to more than three times the resonance frequency. Stepped impedance open loop resonators with substantially increased outer‐edge width are used to improve the spurious resonance response. Both simulation and measured results are presented and good agreement is obtained between the results. The fabricated filter exhibits dual operating frequencies at 1460 MHz and 2640 MHz with 5.5% and 5% stopband fractional bandwidths, respectively. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 627–633, 2013.     

Investigations on fractal frequency selective diaphragms in rectangular waveguide

In this article, self‐similarity and space‐filling properties of fractal structures are explored as frequency selective diaphragms in rectangular waveguide, which can find applications in the design of compact, lightweight, and multiband waveguide filters with better out‐of‐band rejection ratio. Some self‐affine fractal structures, based on Sierpinski gasket and plus shape fractals, are proposed, and the effect of scaling factor on the location of transmission bands is investigated. Self‐similar structures like Hilbert curve, Koch curve, and Minkowski fractals are shown to be efficient in reducing resonant frequency of the diaphragm. Numerical results are presented along with the results obtained from HFSS, which show a good agreement. A typical application of the fractal diaphragm in the design of waveguide bandstop filter has also been demonstrated. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

两种新型一维微带开口环PBG结构

本文在对一维光子带隙PBG(Photonic Bandgap)结构进行研究时,提出两种新型的开口环PBG结构,分别为圆形双开口环和方形双开口环两种结构。两种结构均为在接地板上刻蚀周期性的开口环得到。结果表明:圆形双开口环PBG结构简单易于实现,并且可以获得较宽的通带及较小的通带波纹。方形双开口环PBG结构具有良好的通带特性,并且可以有效地改善通带的平坦度,减小插损,适用于微波及毫米波集成电路。     

Micromachined tunable filter using fractal electromagnetic bandgap (EBG) structures

A tunable bandstop filter using fractal electromagnetic bandgap (EBG) structure is designed, simulated and fabricated. The uniform fractal EBG (U-FEBG) structure is realized by replacing the etched rectangular holes with a Minkowski loop generator. A new technique of doubly tapered fractal EBG (DT-FEBG) structure is designed by non-uniform Kaiser distribution on the fractal structures. The Kaiser distribution improves the pass band performance and generates two distant bandgaps. The tunable bandstop filter is tuned by micromachined capacitive bridges. The propagation characteristic of the periodic microelectromechanical system (MEMS) bridges is determined by the dispersion behavior. Different types of parametric analysis are applied to investigate the performance of the MEMS bridges. Surface micromachining fabrication process is employed on the high resistivity silicon substrate to fabricate the filter. The measurement results for the DT-FEBG structure show insertion loss of 1.2 dB and the stop-band rejection of 44 dB. The tuning range of the U-FEBG structure is 1.1 GHz with insertion loss of 1.7–2.5 dB.     

Dual‐band dielectric resonator bandstop filters

This article presents the design and implementation of a new asymmetric dual‐band bandstop filter using TE01δ mode dielectric resonator (DR) technology. The coupling matrix is generated by frequency transformation technique applied to advance filtering functions for direct‐coupled asymmetric dual‐band bandstop filter in cul‐de‐sac configuration. The proposed approach provides control of all the major parameters such as center frequencies, intercavity couplings, and input/output couplings of filter independently in both the designated bands. The dual‐band DR filters (2 × 2) pole, with return loss = 15 dB and percentage rejection bandwidth of 1.6 and 0.6% in two bands, at 9.96 and 10.15 GHz, respectively, are designed, built, and tested. The measured and simulated results are in good agreement over the desired band. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:282–288, 2015.     

Dual extended composite right/left‐handed transmission line metamaterial

The new concept of dual extended composite right/left‐handed transmission line (D‐ECRLH TL), with 2 right handed and 2 left handed frequency bands is presented. The D‐ECRLH TL and extended composite right/left handed transmission line are structurally dual. Therefore, the proposed TL shows the dual properties of the ECRLH TL. The D‐ECRLH indeed behaves as a dual‐band bandstop filter, in opposition to the ECRLH which is a dual‐band bandpass one. In contrast, the D‐ECRLH creates an unlimited LH bandwidth. In this article, the transmission parameters and the fundamental properties of the D‐ECRLH TL (dispersion and impedance diagrams) are investigated. The results show that the proposed structure is suitable to design the quad‐band microwave circuits and systems. A prototype of the proposed D‐ECRLH unit cell is realized by the microstrip technology. The good agreement between the measurement and simulation results confirms the realizability of the proposed structure.     

Reliability-based topology optimization using a standard response surface method for three-dimensional structures

In this paper, a reliability-based topology optimization (RBTO) for 3-D structures was performed using bi-directional evolutionary structural optimization (BESO) and the standard response surface method (SRSM). In order to get a stable optimal topology, the most recently-developed filter scheme was implemented with BESO, and SRSM was used to generate an approximate limit state function. These results were compared with the recently announced results of RBTO for 2-D structures, and the differences between the results for the 3-D and 2-D structures were examined. A cantilever beam and an MBB beam were selected as the numerical examples. The comparison showed that the optimal topologies of deterministic topology optimization (DTO) and RBTO for the 2-D and 3-D MBB beams, respectively, are very different. Specifically, the two-support member on the left hand side comes into being along the width for the 3-D case, but not for the 2-D case. This shows that RBTO for 3-D structures should be performed as part of the design process.     

Recent advances in microwave active filter design. Part 1: Low‐frequency techniques and noise optimization

This two‐part article presents a representative sample of recent advances in microwave active filter design. In part one, we discuss design techniques based on both analog and digital low‐frequency methods that have been adapted to microwaves. From circuits with analog origins, we present simulated results, with some experimental verification, for a frequency‐dependent negative resistance (FDNR) and active‐inductance MMIC bandpass filters. From circuits with digital origins, we present experimental results for recursive filters, including MMIC bandpass and bandstop structures as well as higher‐order cascaded sections. Part one concludes with a discussion of the noise‐wave formalism and experimental results for active‐recursive and tunable ring‐resonator filters with minimum noise figure. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 159–176, 2002.