Dual stop band frequency selective surface for C and WLAN band applications

A miniaturized unit cell design of Frequency Selective Surface (FSS) to produce stop band characteristics for two bands is presented. The presented unit cell structure is showing the band filtering characteristics for dual frequency band specifically C-band for satellite communication and Wireless Local Area Network (WLAN). The designed FSS structure is comprised of I shaped and modified I shaped metallic strips. The distinct unit cells of suggested are investigated for band filtering characteristics and finally integrated on a single unit cell for dual-band filtering applications. The I shaped and modified I shaped unit cell is producing band filtering properties at center frequencies like 4 GHz and 5.5 GHz respectively. The presented FSS design is modeled on an FR-4 substrate with dielectric constant of 4.4 and the dimension of the unit cell is 10 × 10 × 1.6 mm³. The fabricated FSS structure is simulated and measured for its characteristics verification like S₁₁ and S₂₁ and it has been found a satisfactory agreement in simulated and measured results.     

加载频率选择表面的特性研究

采用加载技术对普通频率选择表面进行了改进,同时使用周期矩量法对它的特性进行了分析.仿真结果表明,通过不同的加载可以实现不同频段的工作,特别是在保持尺寸不变时使谐振频率大幅降低,为频率选择表面的发展提供了新的方向.制作了实际的电路,测量结果和仿真结果基本吻合.     

Electromagnetic Modeling of Quasi‐Square Open Metallic Ring Frequency Selective Surface Using Wave Concept Iterative Procedure

The wave concept iterative procedure (WCIP) is used to analyze a quasi‐square open metallic ring frequency selective surface (FSS). The quasi‐square open metallic ring FSS is dual‐polarized. When the incident plane wave is polarized in a direction parallel to the FSS’ coupled parallel strips, it shows two rejecting bands. Moreover, another rejecting band can be obtained if the source plane wave is perpendicularly polarized with respect to the FSS’ coupled parallel strips. The three resonant frequencies are inversely proportional to the length of the FSS’ coupled strips to provide an easy fine tuning of the FSS structure. The simulated results obtained using WCIP are compared to the measured results, and a good agreement is reported.     

A universal frequency reuse scheme in LTE‐A heterogeneous networks

Effective inter‐cell interference mitigation has been extensively studied because of its outstanding cell‐edge signal quality improvement capability. Conventional static inter‐cell interference coordination strategies, including fractional frequency reuse and soft frequency reuse, have received much attention owing to their effectiveness in mitigating interference and low complexity in implementation. However, they are less effective when dealing with dense uneven traffic distributions and dynamic traffic demands and thus incur low spectrum utilization in some cells and spectrum shortage in others. This paper proposes a universal frequency reuse scheme in a two‐layer Long Term Evolution‐Advanced heterogeneous network to ensure good throughput for all user equipment (UE), especially UEs at cell edge. The proposed scheme allows each cell to use all the spectrum resources, limited by an orderly regulation of all sub‐bands. This scheme minimizes the potential occurrence probability of inter‐cell co‐sub‐band interference through an intra‐cell sub‐band resource management. Furthermore, a graph‐theoretic based sub‐band allocation algorithm is developed to optimize UE throughput performance, especially for the cell‐edge low signal to interference noise ratio UEs. A comprehensive performance comparison among different frequency reuse schemes is conducted by considering performance metrics, including cell‐edge throughput, average throughput, and signal to interference noise ratio cumulative distribution function. Simulation result shows that the universal frequency reuse scheme outperforms other two schemes significantly. Copyright © 2016 John Wiley & Sons, Ltd.     

基于电容加载的圆环缝隙频率选择表面研究

 介绍了一种新型小型化频率选择表面（FSS）,在圆环缝隙周期单元表面加载电容以缩小FSS尺寸,并引入法拉第笼结构以消除单元间的干扰. 对这种加载FSS进行了数值仿真和分析,提出了一种适用于1~4GHz频段的电容加载FSS谐振频率经验计算式,并在此基础上设计研制了谐振频率为2.45GHz的加载FSS,其物理尺寸仅为传统FSS的百分之三十四,仿真和实测结果表明该FSS具有谐振频率稳定、对入射波入射角不敏感、对TE、TM极化一致性好等优点.     

Miniaturised bandpass frequency selective surface with lumped components

A miniaturised frequency selective surface (FSS) loaded with lumped components is presented. The FSS uses inductors and capacitors to provide a bandpass response with a simulated unit cell size of /apl lambda//115 with a 23 dB bandwidth of 23.9%. This is the first reported use of the combination of capacitors and inductors to provide miniaturisation to this extent. Measurements are presented to validate the technique, showing an FSS resonating at 945 MHz with 21.9% bandwidth and a unit cell size of λ/18.     

Codebook‐Based Precoding for SDMA‐OFDMA with Spectrum Sharing

This paper focuses on codebook‐based precoding for space‐division multiple access/orthogonal frequency‐division multiple access (SDMA‐OFDMA) systems aiming to guarantee high throughput for their users as well as to mitigate interference to fixed satellite service (FSS). A systematic design of SDMA codebook for subband‐based OFDMA is proposed, which forms multiple orthogonal beams with common spatial null in the direction of a victim FSS earth station (ES). The design enables both transmitter and receiver to independently construct identical codebook by sharing only on the direction angle of an FSS ES, which takes fewer overhead bits than Gram‐Schmidt process, a general method satisfying our design criterion. A system‐level throughput evaluation shows that the proposed precoding provides superior performance over existing spectrum sharing method, that is, subband deactivation. The spectrum sharing analysis shows that the proposed precoding, even with an estimation error of the direction angles of an FSS ES, causes lower interference than existing precoding, knockdown precoding.     

Dual-Band Capacitive Loaded Frequency Selective Surfaces With Close Band Spacing

In this letter, a novel miniaturized dual-band capacitive loaded frequency selective surface (FSS) is presented, in which each periodic cell consist of two neighboring capacitive loaded ring slot resonator with the same dimension. To eliminate the undesired coupling between unit cells, the unit cell is placed in a Faraday cage structure created by arrays of metallic substrate vias. An S-band dual-band FSS with such structures is designed and fabricated, both simulated and measured results show that the proposed FSS provides high transmission with close band spacing at 2.5 and 3.5 GHz, and there is no other resonance frequency up to 15 GHz. Furthermore, the FSS dimension is miniaturized to $0.082lambda$ ($lambda$ refer to the resonant wavelength of 2.5 GHz). Also, it is not sensitive to the angle of oblique incidence wave. The design and discussion about dual-band FSS loading with lumped elements is presented for the first time.      

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。     

Performance analysis of a reuse partitioning technique for multi‐channel cellular systems supporting elastic services

For multi‐cell systems employing intra‐cell orthogonal communication channels, inter‐cell interference mitigation techniques are expected to be one of the key radio resource management functions. In this paper we propose and analyze a simple reuse partitioning technique (with random and coordinated resource block allocation in neighbor cells) that is able to reduce inter‐cell interference. We propose a model that is able to take into account that sessions dynamically enter and leave the system. Rigid sessions require a class‐specific fixed number of resource blocks, while elastic sessions can enter the system if a minimum number of resources are allocated to them. In this rather general setting (and using the example of a system employing frequency division for multiple access) we analyze the system performance in terms of the expected number of channel collisions, the session‐blocking probabilities, the signal‐to‐interference‐and‐noise ratio (SINR) and packet error rate performance. We present numerical results on the various trade‐offs between these measures (including the trade‐off between the reuse factor and the SINR performance) that provide insight into the behavior of multi‐channel cellular systems and help dimensionalize the parameters of a reuse partitioned system. Copyright © 2008 John Wiley & Sons, Ltd.     

27~29.5 GHz频段IMT-2020(5G)系统对卫星固定业务系统干扰分析研究

基于WRC-19 1.13议题研究框架和国内6 GHz以上第五代（the 5th Generation,5G）移动通信候选频段的兼容性分析要求,针对27~29.5 GHz频段国际移动通信-2020（International Mobile Telecommunications-2020,IMT-2020）系统对卫星固定业务（Fixed Satellite Service,FSS）系统的干扰进行研究.采用集总干扰评估方法,比较了FSS静止轨道卫星经度分别在东经59°、85°、113°时,IMT-2020（5G）系统基站对FSS上行链路的干扰情况.此外,还针对IMT-2020（5G）基站采用不同阵列配置进行了兼容性仿真研究.研究表明,在该频段IMT-2020（5G）系统不会对FSS产生有害干扰,特别是在IMT-2020（5G）基站采用大规模天线阵列的情况下.研究结果可为未来27~29.5 GHz频段IMT-2020（5G）系统频率规划实际部署及保护FSS系统提供技术依据.     

Frequency Selective Surface Based Bandpass Filter for THz Communication System

In this work, a band pass filter based on frequency selective surface (FSS) is presented. The resonance of the FSS is achieved by perforating slot type ring structure on an Aluminum layer. To ensure adequate mechanical strength, this structure is again supported by a dielectric layer. The physical dimensions of the FSS, i.e. ring radius, slot width, cell dimension and width of the layers all are responsible for the resonance behavior. In its electrical equivalent circuit, these dimensions act as inductor and capacitor. The center frequency of the designed filter is at 0.16?THz with a ?3?dB bandwidth of 18?GHz. This filter can be utilized as a part of any THz communication system to achieve application specific frequency discrimination. The simulation has been carried by using commercial software-CST Microwave Studio. The performance of the fabricated FSS is evaluated by Microwave Vector Network Analyzer.     

Convoluted dipole array elements

Convoluting the conductors of dipole frequency selective surfaces (FSS) while retaining the unit cell dimensions produces a major reduction in the resonant frequency and in the sensitivity of the reflection band to angle of incidence. The separation of this band from the onset of grating responses is correspondingly increased.<>     

利用频率选择表面改善微波吸收材料S波段的吸波性能

研究了如何利用金属周期性频率选择表面(FSS)的频率特性来改善微波吸收材料S波段的吸波性能。利用频率选择表面的等效电路和传输线理论分析了FSS和吸波材料涂层双层结构的微波反射特性。采用基于有限元方法的电磁波全波分析软件设计并仿真分析了FSS的结构和尺寸,实际制作了FSS和吸波材料涂层双层结构,测量了微波反射性能。理论分析和实验研究表明,利用FSS可以明显改善吸波材料涂层S波段的吸波性能,展宽涂层的吸波带宽,从而改善吸波材料的低频吸波性能。     

平面波展开结合矩量法分析频率选择表面

为了快速分析频率选择表面（FSS）,利用天线阵列理论,引入FSS单元之间互导纳的概念,得到互导纳方程。当FSS阵列无限大时,可以应用Floquet定理简化该方程,同时对方程中某些收敛较慢的项进行平面渡展开,利用矩量法求解。采用该思路我们计算了几种多层FSS及多频FSS,并和实测结果进行对比,得到了较满意的结果。不仅如此,该方法相对其他的单一数值方法具有速度快、收敛好的特点。     

Polarisation independent bandpass FSS

The spectral transmittance of a frequency selective surface (FSS), which consists of two free-standing arrays of short-circuited nested annular slots, is presented. The FSS was designed to provide a minimum of 20 dB isolation between the frequency bands 316.5-325.5 and 349.5-358.5 GHz when the filter operates in the TE and TM planes at 45deg incidence. Experimental results, which are in close agreement with the computed transmission coefficients, show that the maximum insertion loss is 0.9 dB, and the minimum cross-polar discrimination is at least 21 dB in the passbands. The FSS yields virtually identical spectral responses in the two polarisation planes over the frequency range 315-359 GHz.     

一种X波段小型化可调谐FSS设计

频率选择表面（frequency selective surface,FSS）的研究中,小型化设计一直是研究的热点内容之一,小型化单元结构可以很好地增加FSS的稳定性.文章利用液晶材料给出一种基于三层互耦结构的可调谐FSS单元的设计,为了将每个单元的金属结构连接起来,添加了集总元件来馈电.结果表明,该结构单元尺寸相当于工作波长的1/16,连续可调谐范围可达11.3%.本文所设计结构具有小型化和可调谐的特性,为FSS的设计提供了新的设计思路,具有一定的理论指导意义和实用价值.     

Cooperative communications for LTE‐advanced—relay and CoMP

The Long Term Evolution‐Advanced (LTE‐A) system is currently under development to allow for significantly higher spectral efficiency and data throughput than the LTE systems. In a wireless system based on orthogonal frequency division multiplexing with frequency reuse factor one, the achievable cell spectral efficiency is often limited by the inter‐cell interference or coverage shortage of base stations. In LTE‐A, coordinated multi‐point transmission/reception (a.k.a. multi‐cell MIMO or base station cooperation) and relaying technologies are being introduced to clear these major performance hurdles. In this paper, cooperative communication technologies being discussed in LTE‐A systems are presented, together with considerations on system design. Copyright © 2012 John Wiley & Sons, Ltd.     

圆型厚屏频率选择表面的特性研究

相对于薄屏频率选择表面而言,厚屏频率选择表面可以通过高精度机械加工手段直接利用金属屏获得,加工方法简单。同时,厚屏频率选择表面具有更高的Q 值和较少的介质匹配问题。在设计了一种圆形厚屏频率选择表面的基础上,通过时域有限差分法进行了数值仿真,研究了单元尺寸、单元周期和屏厚度等参数对其传输特性的影响,并通过机械加工方法进行了样件的微波暗室测试对比。结果表明:随着单元周期和屏厚度的增加,工作带宽和中心频点降低;随着单元尺寸的增加,工作带宽增加,但中心频点降低。仿真结果与测试结果规律相一致。     

Analysis and synthesis of multiband dual polarized parallel metallic strips FSS with a ring using WCIP method

In this paper parallel metallic strips FSSs with a ring are introduced and analyzed by the WCIP method for their simple modeling characterized by independent resonant frequencies due to its non-coupled metallic elements. Two FSS structures are manufactured and measured. A FSSs synthesis approach is presented and the curves relating the desired resonant frequencies to the FSS metallic elements lengths responsible of theses frequencies are plotted. To test the synthesis, approach the two manufactured FSSs frequency responses are taken as the desired ones and the proposed synthesis approach is used to determine the metallic strips and the ring lengths for the FSSs unit cell. WCIP results are compared to measurements and a good agreement is observed. For complex pattern FSS the resonant frequencies sources are not always easy to be determined. Thus an equivalent FSS based on metallic strips and a ring can be used maintaining the same frequency response in the limit of the proposed approach. The synthesis approach is used to determine its equivalent FSS structure of a published complex FSS pattern. WCIP method and HFSS software results of the equivalent FSS are compared to published measurements and a good agreement is recorded.