平面微波光子晶体表面波带隙的直线法分析

运用直线法对一种以微带基片为载体的平面微波光子晶体进行了分析.详细介绍了直线法分析过程,并对直线法中阻抗矩阵的提取方式作出了改进.在不同的周期边界条件下,通过对由直线法所得的特征方程的求解,得出所对应的本征频点,从而求得整个平面微波光子晶体的表面波色散图,标明表面波带隙所在.文中分别对矩形贴片型以及环形贴片型光子晶体进行了分析.     

半圆形隧道中导行波特征方程的近似求解

当半圆形隧道中存在一根导线时,根据场的唯一性原理,该导线产生的场与圆形隧道中该导线与其镜象产生的场的叠加等效,虽然可用Newton法或抛物线法求其特征方程,但求解过于复杂,根据镜象电流的特点,推导了半圆形隧道导行波的简单算法.计算结果得到,在频率较高时,近似结果和精确结果基本相同.近似求解方法对矿井通信的研究有指导意义.     

多模阶跃光纤纤芯传导模式的快速求解

在多模光纤模式色散求解、光纤耦合模理论分析以及锥形光纤的模式演化等过程中,都涉及到多模阶跃光纤纤芯传导模式的特征方程的求解,计算量很大,从而直接影响整体的计算效率。分析了牛顿迭代法及其收敛速度的优势。求解弱导近似下的标量模式特征方程时,利用第一类贝塞尔函数的零点确定其解区间,再结合牛顿迭代法在区间内快速求解特征方程。将此求解过程引入矢量模式特征方程求解中,并结合上下边界截弦的方式快速判断特征方程尾根与首根的存在性问题。将此方法的计算结果与OptiFiber软件的计算结果作对比,画出光纤的模式色散曲线,验证了该快速求解方法的正确性。     

等离子体圆柱波导的频率相关性

通过给出的等离子体圆柱波导的精确特征方程,讨论了特征方程的特征值对频率的依赖。并且对特征值与厚度因子(α)的关系进行讨论,给出了在α1时的特征方程,该方程计算简便。进一步运用α1时的特征方程的解,提出了一种求解严格特征方程之特征值的近似方法。     

波纹圆波导特征值的渐近解

波纹波导的特征方程是一个超越方程,求解的过程相当繁琐,Dragone[2,3]提出了一种求解波纹圆波导特征方程的方法,本文首次推导了波纹圆波导中HEmn、EHmn和E02模的渐近级数表达式,简化了波纹波导特征方程求解,有利于波纹圆锥喇叭的设计.     

手征负折射率包层光纤的模式特性研究

对手征负折射率包层光纤的导模和表面波模的特性进行了理论研究,导出了模式特征方程,给出了3种不同参数情形下的模式的色散曲线、能流分布和归一化功率随归一化频率的变化关系曲线,并且与负折射率介质光纤和一般手征光纤的模式特性进行了比较.结果发现,其存在两个单模区,在某些频段,表面波模的能流和功率在一般介质的纤芯内为负而在手征负...     

一维非线性光子晶体中电磁波传播的理论分析

考虑具有金属包层结构的一维非线性光子晶体,应用Maxwell经典电磁理论,建立了电磁波传播特性的理论分析模型,得到了其电磁场的全波解。根据电磁场在包层边界应满足的基本关系,建立了描述其带隙结构的特征方程,给出了特征方程迭代求解的算法描述,为电磁波传播特性数值仿真分析提供了理论基础。     

脉位调制式声表面波射频标签的回波时延估计

脉冲位置调制式声表面波(SAW)标签利用较少的反射脉冲实现高效编码,正逐渐取代开关键控编码成为声表面波射频标签的主流编码方式.反射回波之间的时延估计精度成为该方式编码容量和解码的核心.该文提出了一种利用计算回波包络二次相关的高精度估计回波脉冲时延的方法.研究了插值算法对相关峰值估计的影响.通过实际声表面波标签回波信号的实际测试和对照实验,证实了该方法的有效性.     

规则圆柱螺旋薄带特征方程的数值解

本文对规则圆柱螺旋薄带的特征方程进行了严格的数值求解.计算结果表明,与近似解或经验公式相比较,数值解与实验的一致性为最好.     

高阻抗表面型PBG结构贴片天线的设计

将高阻抗表面型光子带隙材料用于微带贴片天线的设计,利用其频率带隙抑制天线中激励的表面波.求解辐射方向图,并与常规微带贴片天线相比较,证实了在表面波的影响比较显著的情况下,光子带隙材料的引入可以有效地抑制表面波的传播,从而改善原有天线的性能.仿真结果表明:PBG天线的增益比原贴片天线提高了约0.53 dB.     

Numerical analysis of surface wave on microstrip antenna with lossysubstrate

The key to analysing a guided surface wave is to solve its eigenvalue equation. When the medium is dissipative, the eigenvalue equation is a complex transcendental equation. The Kuhn algorithm is applied to work out the eigenvalue equation     

Time Delay Estimation Method Based on Canonical Correlation Analysis

The localization of sources has numerous applications. To find the position of sources, the relative delay between two or more received signals for the direct signal must be determined. The generalized cross-correlation method is the most popular technique; however, an approach based on eigenvalue decomposition (EVD) is another popular one that utilizes the eigenvector of the minimum eigenvalue. The performance of the eigenvalue decomposition (EVD) based method degrades in low SNR and reverberation, because it is difficult to select a single eigenvector for the minimum eigenvalue. In this paper, we propose a new adaptive algorithm based on Canonical Correlation Analysis (CCA) to extend the operation SNR to the lower SNR and reverberation. The proposed algorithm uses an eigenvector that corresponds to the maximum eigenvalue in the generalized eigenvalue equation (GEVD). The estimated eigenvector contains all required information for time delay estimation. We have performed simulations with uncorrelated, correlated noise and reverberation for several SNRs, to show that time delays can be more accurately estimated (especially for low SNR) a CCA based algorithm versus the adaptive EVD algorithm.     

任意截面波导特性的非正交频域有限差分研究

本文提出了一种求解波导本征问题的非正交频域有限差分(FD-FD)算法。该算法中的数值离散网格可与任意复杂边界形状吻合一致。文中通过所建立的本征方程对波导中各模式的截止频率进行了求解,数值结果与已有结果符合良好。     

求解Helmholtz方程的新型稀疏近似逆预条件算法

提出了一种新型预条件算法,用于对有限元法离散Helmholtz方程所产生的大型稀疏复对称且高度不定的线性系统进行高效迭代求解。该新型预条件子是在复拉普拉斯偏移算子的基础上结合改进的稀疏近似逆算法来得到。通过改善矢量有限元线性系统自身的谱特性,该预条件算法既可避免迭代中的不稳定情况,同时也能较大提高迭代求解效率。数值结果表明,与若干常用预条件算法相比,所提出的预条件算法更加有效。     

Ag-coated Long-period Fiber Grating

Based on coupled-mode theory, the eigenvalue equation of five-layered long-period fiber grating （LPFG） sensor with Ag film and gas-sensitive film overlays are firstly studied. The problem of resolving complex eigenvalue equation on five-layered LPFG is analyzed, and the method of resolution is also given. Then the eigenvalue equation of three-layered metal cladding LPFG is analyzed, and the complex transcendental equation is also discussed. The computing result shows that the coupling between the low order EH modes and the core mode is much stronger than that between the low-order HE modes and the core mode.     

Fusion spectrum sensing algorithm based on eigenvalues

Aiming at the problem of inefficient use of spectrum resources,a fusion spectrum sensing algorithm based on eigenvalues was proposed to effectively achieve dynamic spectrum sharing.The test statistics were constructed by employing the maximum eigenvalue,the trace and the geometric mean of all eigenvalues of the sample covariance matrix.The detection probability and false alarm probability of the proposed method were analyzed using the random matrix theory,and the analytical representation of the theoretical threshold was obtained.In addition,the parameter selection of the proposed algorithm was analyzed theoretically.Simulation results show that the proposed algorithm has better detection ability than the existing eigenvalue detection algorithm.     

Reply to “Comments on adaptive IIR filtering with monicnormalization”

Kim and Song (see IEEE Signal Processing Lett., vol.6, p.35-37, 1999) focused on the bias removal capability of the monic normalization equation error (MNEE) algorithm and showed in another paper (see IEEE Signal Processing Lett., vol.7, p.54-56, 2000) that the parameter estimated by the MNEE algorithm converges to the solution of the well-known eigenvalue equation presented by Regalia (1994), which is based on the unit-norm constraint. However, the convergence properties of the MNEE have not been fully understood. Some of its convergence issues were commented upon by Soderstrom (see vol.48, p.892-94, 2000). In the MNEE, there is a small bias of order O(μ). Under a certain condition, the MNEE may not be convergent. In this reply to Soserstrom's comments, we provide some remarks related to the above issues     

New computation method for characteristic modes

To compute the characteristic modes of a perfectly conducting object a new weighted eigenvalue equation is derived, using the magnetic-field integral equation. The method of moments is used to solve this eigenvalue equation, and a number of bodies of revolution are examined. The results are presented and compared with those of previous methods.     

螺旋-圆柱波导系统特征值的研究

本文给出了螺旋-圆柱波导系统的特征方程,首次求得了此结构的复根模,推导出了实根模、虚根模和复根模相互之间的分界条件,并给出了一些特征值曲线。最后,利用特征方程近似计算了一个螺旋-圆锥喇叭天线的远场辐射方向图,数值结果与实验进行了很好的比较。     

3-D numerical mode-matching (NMM) method for resistivitywell-logging tools

A three-dimensional (3-D) numerical mode-matching (NMM) method is presented for Poisson's equation in general inhomogeneons media. It reduces the original 3-D problem into a series of two-dimensional (2-D) eigenvalue problems plus a one-dimensional (1-D) layered medium problem, which can be modeled efficiently by a recursion procedure. The algorithm is tested for several 3-D inhomogeneous media and an excellent agreement between the NMM and analytical solutions is obtained for all test cases. We demonstrate some typical applications of the 3-D NMM algorithm in resistivity well logging, including invasion zones of noncircular shape, vertical and horizontal fractures, and horizontal wells. The solution procedure proposed is directly applicable to wave propagation in 3-D inhomogeneous media