基于GPU的FDTD麦克斯韦方程快速求解

采用图形处理器(GPU)为主计算核心,应用时域有限差分法(FDTD)实现电磁学中麦克斯韦方程组的快速求解。通过对FDTD求解麦克斯韦旋度方程的直接时间域的分析,给出FDTD的仿真算法。根据GPU能高效地提高FDTD的仿真速度,解决FDTD仿真算法中的计算量庞大问题。利用GPU在FDTD计算中的处理能力,实现了更长的脉冲持续时间和庞大的模型求解与仿真,在适当的时间内完成了超大量的仿真计算。根据在CPU和FDTD上的实际计算结果表明,基于GPU的FDTD仿真算法具有高精度和高效率等特点。     

基于FDTD的机载短波天线辐射特性分析

机载天线辐射特性的研究对于机载天线的设计与布局具有重要的意义。机载天线在机身的影响下会改变其原有辐射特性,针对上述问题采用时域有限差分法(FDTD)对机载短波天线的辐射特性进行了分析,并应用FDTD对某型号机载短波天线进行了仿真:使用软件建立整机模型,应用自适应网格对其进行了剖分,设置了PML吸收边界,添加激励并计算得出增益方向图,最后将仿真结果与实测结果进行了比较,二者在天线工作频带内吻合,验证了FDTD对机载天线辐射特性进行分析的有效性与实用性。     

时域天线阵的测试及其结果分析

将时域天线组成阵列是改善超宽带雷达技术性能一条行之有效的途径;研究时域天线阵辐射或接收的波形变换和畸变规律．是十分必要的;利用虚拟仪器技术,采用1．abView软件平台,使用模块化设计思想．实现一套慕于示波器和转台协调工作的时域天线阵自动测试系统的设计;通过对灭线阵测试结果进行分析,并与FDTD的仿真结果进行对比,得出关于时域天线阵有价值的结论。     

金属物体影响下探地雷达接收信号的分析

探地雷达工作时收发天线一般是并排放置的.与此不同,本文提出了一种新的应用模型并且应用时域有限差分(FDTD)方法和自适应滤波方法时接收天线接收到的信号成份进行了分析,以利于后期数据解译.     

一种提高FDTD近远场变换计算效率的方法

时域有限差分(FDTD)法中的时域近远场变换法计算天线远场辐射特性的优点是通过一次计算可以得到全频域的结果,缺点是数据存储量大、计算速度慢。文献R.Pascaud、S.Wang和G.Carat介绍了一种基于二维空间数据压缩的时域近远场变换方法,此方法可以大大减少数据存储量从而减少近远场变换时间。基于减少数据量的考虑,本文提出一种基于时域抽样法的近远场变换算法以提高近远场变换计算效率。为验证新算法的有效性,分别用经典算法和时域抽样法对七单元八木天线远场辐射特进行计算,结果表明本算法可有效减少数据存储量,提高近远场变换效率。     

基于CUDA架构的三维CPML-FDTD并行方法

为解决时域有限差分（FDTD）算法应用于电大尺寸目标仿真的巨大耗时问题,应用FDTD算法的并行特性和通用图形处理器（GPGPU）技术,实现了一种基于计算统一设备架构（CUDA）的三维FDTD并行计算方法,采用了时域卷积完全匹配层（CPML）吸收边界条件模拟开域空间,对不同网格数目标仿真计算。进一步结合FDTD算法和CUDA的特点进行了优化,当计算空间元胞数在十万数量级及以上时,优化前后GPU运算相对于同时期的CPU分别可获得10和25倍以上的加速,结果表明该方法较适合用于实际电磁问题的仿真。     

时域有限差分法仿真等离子体

时域有限差分(FDTD)算法被广泛地用于模拟电磁场的传播。给出了电磁波在非磁化等离子体中传播稳定条件,并给出了非磁化色散等离子体的FDTD方法,同时对结果进行了分析。     

三维FDTD众核算法的设计与实现

在电磁学中,时域有限差分算法(FDTD)能够精确地模拟空间中电磁场的变化,在电介质器件设计领域得到了广泛的应用。众核(many-core)处理器片上计算资源丰富,对于计算密集型课题有较好的适应性。通过对麦克斯韦方程FDTD仿真算法的分析,并根据众核处理器的特性,实现了FDTD算法的众核并行。实验结果表明,FDTD算法在众核处理器平台上具有较好的计算效率,能够很好地发挥众核结构的优势。     

双频共面波导天线设计

本文提出了一种基于共面波导结构的工作频率在2.45GHz和5.8GHz的双频带天线的设计。该天线采用了增加突出结构和边缘开槽的方法,通过时域有限差分法(FDTD)对共面波导尺寸的变化进行了仿真与优化,得出了共面波导结构对天线性能的影响,从而给出了相应的结构尺寸。并实际测量了天线的反射参数以及方向图,对比测量结果与仿真结果基本符合。最后本文对本次天线设计做出总结并对测量结果做了误差分析。     

高阶旋转体时域有限差分法

旋转体时域有限差分法(BOR FDTD)是模拟电磁波与旋转对称目标体相互作用的一种高效算法,但目前的BOR FDTD对时间和空间的差分精度均只有二阶.通过把电磁场各分量作泰勒展开,并结合麦克斯韦方程,提出了BOR FDTD的三种高阶算法.相对于目前的BOR FDTD,三种高阶算法均不增加存储量.通过模拟简谐波与介质球的相互作用并和理论值作比较,证实了高阶算法在提高计算精度方面的有效性.此外还分析了三种高阶算法的优、缺点,给出了关于高阶算法应用的建议.     

一种淘汰式无拍卖行的电子拍卖

在所有的封闭式电子拍卖中存在的一个共同的缺陷结点(tie)问题，即几个投标者同时投了最高价，由于存在着结点严重地影响了拍卖的效率。基于shamir的(t，n)门限体制提出了一种淘汰式无拍卖行的匿名电子拍卖，采用无拍卖行且每个投标者的标价在投标者之间分享实现标价的匿名性的同时，提出了一种淘汰式拍卖解决结点问题，从而使拍卖的效率得到了提高。     

单极天线的计算机仿真设计

aa输入阻抗,在PML边界条件采用指数差分的形式,减少了误差,与文献比较,获得比较好的结果。     

Wide‐bandwidth multifrequency circularly polarized monopole antenna for wireless communication applications

In this article, wideband circularly polarized monopole antennas with multiresonating frequencies are presented for Bluetooth, WLAN, WiMAX, and X‐band applications. The designed antennas have dimensions of 50 × 35 × 1.6 mm³. Two different substrates (FR4‐epoxy and PTFE) are used for fabricating the antennas. The antennas consist of corner truncated I‐shaped and C‐shaped strips excited by a 50 Ω microstrip feed line. The parametric analyses are performed with the help of Ansoft HFSS V.11 EM simulator. Both antennas have been fabricated and measured. The measured percentage bandwidth of the antenna made by FR4 substrate is 31.32% (centered at 1.66 GHz), and 64.85% (centered at 5.69 GHz). The percentage bandwidth of antenna made by PTFE substrate is 20.57% (centered 2.43 GHz) and 68.74% (centered at 7.39 GHz). In addition to that, there exists 3 dB AR bandwidth for LHCP of about 1050 MHz for 5.2 GHz WLAN‐band. The reflection coefficient, radiation patterns, and the gains of both the antennas are studied in detail. It is found that the measured and simulated results are in good agreement.     

Isolation enhancement between tightly spaced compact unidirectional patch‐antennas on multilayer EBG surfaces

In this article, ultracompact unidirectional patch antennas are used in different two‐antenna systems for biomedical applications at 5.2 GHz. Multilayer mushroom type electromagnetic bandgap (EBG) structures are designed as slow‐wave medium to reduce the size of the individual patch antennas to 0.1λ₀ by 0.18λ₀. Various techniques are investigated herein to improve antenna isolation for an enhanced Multiple‐Input Multiple‐Output (MIMO) performance. First, the coupling between 0.3λ₀‐spaced antennas is verified to occur dominantly through radiation and near‐field coupling between the patches rather than through substrate‐bound modes. Second, various configurations are proposed to suppress antenna coupling. These approaches include reorientation of the antennas and employment of parasitic radiators between the patches. A novel design is presented in which a unidirectional parasitic slot radiator on an EBG reflector is inserted between the antennas to decouple them. Measurement results confirm efficacy of these approaches in mitigating antenna coupling by more than 11 dB in the operating bandwidth of the antennas. The compact patch antennas maintain efficiency values of higher than 70%. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:30–38, 2015.     

Exploiting antenna directivity in wireless NoC architectures

Wireless Network-on-Chip (WiNoC) is an emerging on-chip communication paradigm and a candidate solution for dealing with the scalability problems which affect current and next generation many-core architectures. In a WiNoC, the transceivers that allow the conversion between electrical and radio signals, account for a significant fraction of the total communication energy budget. In particular, the transmitting power for wireless communications is strongly affected by the orientation of the antennas. This paper studies the impact of antennas orientation on energy figures of a WiNoC architecture and performs a design space exploration for determining the optimal orientation of the antennas in such a way to minimize the communication energy consumption. Experiments have been carried out on state-of-the-art WiNoC topologies, on both synthetic and real traffic scenarios, and validated by means of a commercial field solver simulator. When the antennas are optimally oriented, up to 80% energy saving (as compared to the case in which antennas have all the same orientation) has been observed.     

移动Ad Hoc网络中应用智能天线的多址协议及其性能分析

对智能天线在移动Ad Hoc网络(MANET)中的应用进行研究．提出了自适应波束形成CSMA／CA(ABF—CSMA／CA)协议．该协议利用RTS／CTS对话实现信道预约；在RTs与CTS分组中设置了训练序列，收发节点的智能天线基于训练序列进行自适应波束形成以传输数据分组与ACK．提出改进的“虚拟载波监测”机制进行冲突避免(CA)．每个节点中设置两类网络分配矢量(NAV)，用一个oNAV记录邻节点以全向模式占用信道的时间，用多个bNAV分别记录各邻节点以波束形成模式传输分组的时间．推导了信道利用率的近似计算公式并进行了仿真，考察了节点传输距离、训练序列长度及天线模式切换时间对网络性能的影响．结果表明，ABF-CSMA／CA协议与智能天线的结合能有效实现信道的空分复用(SDMA)，显著提高整个网络的信道利用率．     

Design of conical DRH antennas for K and Ka frequency bands

Two conical double‐ridged horn (DRH) antennas for K and Ka frequency bands are presented. Detailed simulation and experimental investigations are conducted to understand their behaviors and optimize for broadband operation. The designed antennas were fabricated with 0.01 mm accuracy and satisfactory agreement of computer simulations and experimental results was obtained. The designed conical DRH antennas have voltage standing wave ratio (VSWR) less than 2.1 and 2.2 for the frequency ranges of 18–26.5 GHz (K band) and 26.5–40 GHz (Ka band), respectively. Meanwhile, the proposed antennas exhibit low cross‐polarization, low sidelobe level, and simultaneously achieve slant polarization as well as symmetrical radiation patterns in the entire operating bandwidth. An exponential impedance tapering is used at the flare section of the horns. Moreover, a new cavity back with a conical structure is used to improve the VSWR. Numerous simulations via Ansoft HFSS and CST Microwave Studio CAD tools have been made to optimize the VSWR performance of the designed antennas. Simulation results show that the VSWR of the proposed antennas is sensitive to the probe spacing from the ridge edge and the cavity back structure. The designed conical DRH antennas are most suitable as a feed for the reflectors of radar systems and satellite applications. Results for VSWR, far‐field E‐plane and H‐plane radiation patterns, and gain of the designed antennas are presented and discussed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Energy efficiency of massive MU-MIMO with limited antennas in downlink cellular networks

In this paper, we analyze and optimize the energy efficiency (EE) of multi-user (MU) multiple-input and multiple-output (MIMO) in downlink multi-cell networks. We first analyze the spectral efficiency (SE) of MU-MIMO systems with a huge number of base station (BS) antennas by using maximal ratio transmission (MRT) and zero-forcing (ZF) precoders in downlink cellular networks. In the analysis, we assume that the number of the BS antennas is huge but limited, which is different from the conventional analysis. Then, we use the analytical SE result and the EE definition to obtain the system EE expression and further analyze the effect of the number of BS antennas and the number of served users on system EE. Since the system EE on the numbers of BS antennas and the number of served users is approximately concave, the corresponding iterative optimization algorithms are proposed to achieve the maximum system EE. The computer simulation results show that the analytical results are accurate and each served user needs about 2 active BS antennas to obtain the maximum system EE when the channel state information is available at the transmitter.     

Analysis of microstrip antennas on finite chiral substrates

An approach is developed to analyze microstrip antennas on finite chiral substrates using the finite-element method (FEM). The perfectly matched layers (PMLs) in the chiral media is employed in this work. First, the characteristics of microstrip antennas on infinite conventional, ferrite, and chiral substrates are respectively analyzed in order to validate our analysis. Then microstrip antennas on finite chiral substrates are investigated as a comparison with those on infinite chiral substrates. Finally, the input impedances of microstrip antennas on infinite and finite chiral substrate are calculated. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 49–56, 2004.