一种可参数化快速FNT的FPGA实现

讨论了一种基于FPGA的快速FNT算法的实现方案，同时对FNT算法的应用进行了初步的探讨。设计采用与FFT算法中类似的基4时序抽取方法，采用双端口内置RAM及数据串入串出的流水线工作方式。本设计可通过调配参数实现64点及256点的FNT变换，并可同时并行完成两组FNT变换。已经成功应用于数字签名算法中GF(p)域多项式模乘的实现，并使用Xilinx公司Virtex2系列xc2v1000器件下载验证通过了64点的FNT变换。     

一种高效的FFT处理器地址快速生成方法

地址产生器是FFT处理器的主要组成部分,地址快速生成和旋转因子读取次数是它的两个重要指标,但很少有算法能够将其统一起来。本文采取了一种新的操作数地址生成顺序并构造了一种新的FFT循环级数表示方法,基于操作数地址的位倒序方式,提出了一种兼有地址简单快速生成与避免重复读取旋转因子特点的可变长地址生成方法,解决了以往地址产生时生成速度与旋转因子重复读取之间的矛盾,实现了快速和降低系统功耗的统一。     

一种FFT和CZT联合的快速高精度频率估计算法

频率估计在通信信号侦察中占有重要地位,CZT算法以其直接、快速、经济的特点适用于当前对频率估计快速、高精度的要求.分析了CZT算法的特点,提出一种联合FFT和CZT的快速高精度算法.通过比较该算法与直接进行FFT计算的运算量,证明了联合算法的优点,并通过MATLAB仿真加以验证.     

利用基于浮动模板的预修正快速傅里叶 变换方法快速求解三维介质体积分方程

利用预修正快速傅里叶变换方法结合矩量法快速求解三维介质散射问题的体积分方程,并引入一种新的模板拓扑结构,将投影及插值模板由固定改为浮动,以减少直接计算和预修正的近区未知量个数。数值计算结果表明,基于浮动模板的预修正快速傅里叶变换方法可以显著减少需要进行预修正的近区未知量个数,从而减少算法的存储需求和计算时间。     

雷达信号载频精确估计的一种方法

介绍了几种常用的雷达载频估计方法,分析了Rife法估计载频的性能,对Rife法在低信噪比条件下偏差较大的不足之处进行了改进,并给出了其计算机仿真结果.     

一种计算MDCT的快速算法

提出了一种计算ＭＤＣＴ的快速算法，并分析了算法的计算复杂度。与利用ＦＦＴ计算的算法相比，本算法的计算复杂度降低了约一半。最后给出该算法的计算机仿真结果。     

一种基于FPGA的FFT阵列处理器

提出一种新的FFT信号处理器的实现方法 ,使用抽取算法在基于FPGA的FFT硬件处理IP上实现并行大点数快速傅立叶变换 ,由于采用专用FFT硬件处理与DSP相结合的处理结构 ,使处理速度大幅度提高。理论和仿真分析论证了该方法的有效性     

一种异步快速傅立叶变换处理器设计

针对一种异步实现结构的异步快速傅立叶变换处理器,给出了处理器中异步加法器的电路和异步乘法器的结构．该异步快速傅立叶变换处理器采用本地的握手信号代替了传统的整体时钟．通过对一个8点的异步快速傅立叶变换处理器电路仿真,得到该处理器的平均响应时间为31．15ns,仅为最差响应时间42．85ns的72．7％．由此可见,异步快速傅立叶变换处理器在性能方面较同步处理器存在优势。     

一种多卫星信号参数的快速盲估计方法

针对电子侦察领域中单通道多卫星信号处理这一新兴课题,提出了一种多信号盲多参数快速估计算法.该算法在检测到卫星信号的前提下,先进行信号个数的盲估计.在对目前存在的各种信号参数估计方法进行充分分析、研究的基础上,进而提出了一种通用的盲多参数快速估计方法,并对其中的滤波器群延迟等关键问题进行了深入分析.计算机仿真表明,与其它算法相比,该算法具有较好的多参数盲估计能力,且通用性和实时性强,能适应单通道多卫星信号的情况.     

一种由全息图制作相息图的方法

将全息图通过高分辨率扫描仪扫入计算机,根据全息图的频域特性,对它进行一维傅 立叶变换,频域滤波去载频,再逆傅立叶变换,求出全息面上的物光信息,从而实现三维场景相息图的制作。由于采用了一维快速傅立叶变换(1DFFT) ,大大提高了相息图的制作速度。     

一种非组合的电磁目标快速识别算法

针对电磁目标识别算法中辐射源组合的本质是避免同一辐射源的多个可能识别结果同时参与一个目标识别模板的匹配置信度计算的问题,提出了一种非组合的快速电磁目标识别方法。依据目标平台与辐射源的搭载关系,建立辐射源识别和平台识别的两级识别体系,基于两点和三点模板匹配法对辐射源进行识别,然后使用非组合的快速模板匹配法对目标平台属性进行识别。仿真实验表明使用该方法计算目标的识别置信度简单易行,可用于实际工程中电磁目标的识别。     

A fast convergent method in electromagnetic inverse scattering

The authors present a fast convergent technique of the Born iterative method for nonlinear two-dimensional lossless object profile inversion using time-domain data. The magnitudes of the scattered fields at different frequencies are weighted according to the properties of the object. It is shown that the technique can speed up the convergence of the Born iterative method     

A fast computational method for near field capacitive couplings

The near-field capacitive couplings are analyzed by using a hybrid method incorporating the finite difference method and the method of moment. A dielectric post is used as the model for analysis. Results from the formerly developed technique of synthetic asymptote are used for comparison. The speed of computation of the developed method is extremely fast.     

Initial results for automated computational modeling ofpatient-specific electromagnetic hyperthermia

Developments in finite-difference time-domain (FD-TD) computational modeling of Maxwell's equations, super-computer technology, and computed tomography (CT) imagery open the possibility of accurate numerical simulation of electromagnetic (EM) wave interactions with specific, complex, biological tissue structures. One application of this technology is in the area of treatment planning for EM hyperthermia. In this paper, we report the first highly automated CT image segmentation and interpolation scheme applied to model patient-specific EM hyperthermia. This novel system is based on sophisticated tools from the artificial intelligence, computer vision, and computer graphics disciplines. It permits CT-based patient-specific hyperthermia models to be constructed without tedious manual contouring on digitizing pads or CRT screens. The system permits in principle near real-time assistance in hyperthermia treatment planning. We apply this system to interpret actual patient CT data, reconstructing a 3-D model of the human thigh from a collection of 29 serial CT images at 10 mm intervals. Then, using FD-TD, we obtain 2-D and 3-D models of EM hyperthermia of this thigh due to a waveguide applicator. We find that different results are obtained from the 2-D and 3-D models, and conclude that full 3-D tissue models are required for future clinical usage.     

复合材料结构等效电磁参数均匀化方法

依据周期结构复合材料等效电磁参数的均匀化方法,推导了此类结构等效电磁参数的有限元计算公式;并对介质框和介质方柱周期结构复合材料的等效介电常数进行了有限元求解,给出了这两类周期结构等效电磁参数的高精度拟合公式。数值算例表明这种有限元均匀化方法是可靠高效的,能够为周期结构复合材料的等效电磁参数预测和设计提供均匀化计算方法。     

系统矩阵表示的电磁场时域计算方法

为了进一步提高电磁场数值计算效率,把数字信号处理技术和计算电磁学的时域有限差分方法相结合,按照信号与系统理论的概念把求解区域看作一个线性系统,从有源区域的麦克斯韦方程组对称形式出发,推导了离散的时域差分方程组,给出了电磁场求解区域的系统矩阵表达形式.分析了求解差分方程组迭代过程的系统框图,以满足数字信号处理的形式要求.对空域上的微分算子进行矩阵分解,把无条件稳定的电磁场时域离散方程组,通过时间交错迭代格式来处理,给出无条件稳定的方程组的系统矩阵形式,实现电磁波传播过程的模拟.最后,通过一维高斯脉冲的传播、低通滤波器以及紧凑型带阻滤波器的仿真,验证了这种系统矩阵方法的有效性.     

Loop-tree implementation of the adaptive integral method (AIM) for numerically-stable, broadband, fast electromagnetic modeling

The adaptive integral method (AIM) is implemented in conjunction with the loop-tree (LT) decomposition of the electric current density in the method of moments approximation of the electric field integral equation. The representation of the unknown currents in terms of its solenoidal and irrotational components allows for accurate, broadband electromagnetic (EM) simulation without low-frequency numerical instability problems, while scaling of computational complexity and memory storage with the size of the problem are of the same order as in the conventional AIM algorithm. The proposed algorithm is built as an extension to the conventional AIM formulation that utilizes roof-top expansion functions, thus providing direct and easy way for the development of the new stable formulation when the roof-top based AIM is available. A new preconditioning strategy utilizing near interactions in the system which are typically available in the implementation of fast solvers is proposed and tested. The discussed preconditioner can be used with both roof-top and LT formulations of AIM and other fast algorithms. The resulting AIM implementation is validated through its application to the broadband, EM analysis of large microstrip antennas and planar interconnect structures.     

一种有效的雷达信号快速识别方法

针对多种调制类型的雷达信号快速侦察识别成功率较低的问题,提出了基于瞬时频率特征提取的雷达信号快速识别新算法.首先,由短时傅里叶变换(STFT)得到信号每一部分的瞬时频率特征;其次,对得到的瞬时频率进行两次归一化分别得到各自特征值;最后,用层次决策方法对雷达信号进行分类识别.仿真实验结果证明该方法能有效识别各种雷达信号,在信噪比高于-3 dB时,各种脉内调制的识别成功率都达到90%以上.     

The fast multipole method (FMM) for electromagnetic scatteringproblems

The fast multipole method (FMM) developed by V. Rokhlin (1990) to efficiently solve acoustic scattering problems is modified and adapted to the second-kind-integral-equation formulation of electromagnetic scattering problems in two dimensions. The present implementation treats the exterior Dirichlet problem for two-dimensional, closed, conducting objects of arbitrary geometry. The FMM reduces the operation count for solving the second-kind integral equation from O(n³) for Gaussian elimination to O(n^4/3) per conjugate-gradient iteration, where n is the number of sample points on the boundary of the scatterer. A sample technique for accelerating convergence of the iterative method, termed complexifying k, the wavenumber, is also presented. This has the effect of bounding the condition number of the discrete system; consequently, the operation count of the entire FMM (all iterations) becomes O(n^4/3). Computational results for moderate values of ka, where a is the characteristic size of the scatterer, are given     

A fast higher-order time-domain finite element-boundary integral method for 3-D electromagnetic scattering analysis

A novel hybrid time-domain finite element-boundary integral method for analyzing three-dimensional (3-D) electromagnetic scattering phenomena is presented. The method couples finite element and boundary integral field representations in a way that results in a sparse system matrix and solutions that are devoid of spurious modes. To accurately represent the unknown fields, the scheme employs higher-order vector basis functions defined on curvilinear tetrahedral elements. To handle problems involving electrically large objects, the multilevel plane-wave time-domain algorithm is used to accelerate the evaluation of the boundary integrals. Numerical results demonstrate the accuracy and versatility of the proposed scheme.