A simple and fast carrier recovery algorithm for high-order QAM

We propose a new carrier recovery algorithm for high-order quadrature amplitude modulation (QAM). The proposed solution relies on two phase detectors, combined with a novel track and hold algorithm for faster frequency acquisition. Compared to previous works, a tenfold improvement or better is achieved in terms of acquisition speed, while keeping a low residual phase noise.     

A simple fast adaptive zero tracking algorithm

This paper presents and investigates a simple and fast zero tracking algorithm for adaptive array processing. With this algorithm, the complex zeroes of the array directional pattern are repetitively updated one at a time by using the LMS algorithm to minimize the output power. Since only one zero is adjusted at any instant, the complexity required to implement the new algorithm is almost the same as that of using the LMS algorithm directly. However, unlike the latter algorithm, the convergence behaviour of the new algorithm is significantly faster and is almost independent of the external noise environment.     

A three-dimensional DFT algorithm using the fast Hartley transform

A three-dimensional (3-D) Discrete Fourier Transform (DFT) algorithm for real data using the one-dimensional Fast Hartley Transform (FHT) is introduced. It requires the same number of one-dimensional transforms as a direct FFT approach but is simpler and retains the speed advantage that is characteristic of the Hartley approach. The method utilizes a decomposition of the cas function kernel of the Hartley transform to obtain a temporary transform, which is then corrected by some additions to yield the 3-D DFT. A Fortran subroutine is available on request.     

A simple, fast adaptive algorithm for broad-band null steeringarrays

A simple algorithm for adaptively steering the broadband null in a two-element power inversion array which uses a tapped delay line filter as the processing element is presented and investigated. By performing a simple signal transformation, the algorithm constrains some of the filter weights so that a variable length delay line is approximated in the maximally flat sense. By using the least mean square (LMS) algorithm to adjust the weights controlling the length and gain of the delay line, a broadband null is then adaptively formed to track and reject the broadband jammer. As studied analytically and by using simulation results, the convergence behavior of the algorithm is fast and depends only on the tolerable level of misadjustment noise. Its implementation complexity is comparable to that of using the LMS algorithm directly     

MEI系数的快速算法

不变性测试方程法已被证明是解决电磁问题的一种有效方法。目前电大尺寸问题中ＭＥＩ系数的计算已成为一个瓶颈。提出了一个快速算法用于加速ＭＥＩ系数的计算,它使用快速多极子方法计算测试子的散射场,使得ＭＥＩ系数的计算速度从Ｏ（Ｎ＾２）变为Ｏ（Ｎ＾１．５Ｌｏｇ２Ｎ）。     

电大尺寸多柱体电磁散射问题的一种快速混合算法--MEI+FMM

本文提出了一种改进的快速迭代ＭＥＩ（不变性测试方程）算法用于分析电气大尺寸多柱体的散射问题,在此算法中我们首次将快速多极子技术（ＦＭＭ）用于加速多柱体之间多次散射场的计算。应用本算法计算了柱体周长为几千波长的多柱体散射场。实际计算结果显示,一方法与原有的直接计算方法具有几乎同样的精度,而速度提高了两个数量级。     

一种简单的自适应快收敛LSP环路预防算法

本文首先分析了基于ATM的MPLS网络必须首先解决的环路控制问题，在总结现有环路预防方法的基础上，通过分析环路预防所要达到的最终目标和目标实现过程中的约束条件，导出了在不同条件下使用不同策略的自适应快收敛LSP环路预防新方法，该算法能够“记忆”并充分利用过去环路预防中的经验，结合不同的网络资源状况自适应调整检测量，仿真结果表明，该方法达到了预期目标，且实施简单。     

一种基于视点的大规模三维地形实时渲染算法

针对大规模三维地形的实时渲染问题,提出一种基于顶点法向量的模型简化算法。渲染过程中利用视图体的投影方式快速裁剪数据块,丢弃与视图体相离的数据块,将部分可见和完全可见的数据块全部加载到内存,根据视点到节点的距离和地形的粗糙程度构造了节点分辨率评价函数,最后采用加点的方法消除裂缝。仿真结果表明,该算法能有效减少渲染地形所需的三角形数目和时间,且对地形的逼真度影响较小。     

计算电大尺寸目标物理光学散射场的快速算法

针对电大尺寸目标高频散射场的仿真,采用物理光学（physics optics,PO）算法来求解.由于PO积分为高振荡积分,传统的数值求积方法非常耗时,文中提出了数值最速下降路径（numerical steepest descent path method,NSDP）算法来计算.首先,通过对振幅函数和相位函数二次拉格朗日函数插值,得到二次曲面片上PO积分标准形式.其次,通过变换积分路径,将高振荡PO积分转化为最速下降路径上的积分,大大减少了计算复杂度.NSDP算法进一步将PO积分转变为驻相点、谐振点和顶点的贡献,具有鲜明的物理意义.数值算例证明了NSDP算法具有精度误差可控和频率无关的特性.     

A simple formula for the ground resistance calculation

Simple approximate formulas for the ground resistance and the potential distribution that have quite good accuracy are presented. The use of these formulas can simplify and make faster the calculation of ground path coupling     

快速计算电大尺寸目标双站电磁散射的方法

提出利用等效边缘电磁流方法快速计算复杂形体电大尺寸目标的双站ＲＣＳ。该方法运算速度快,考虑了边缘绕射和遮挡,计算精度高。在计算尖锥柱等典型散射体的ＲＣＳ的基础上,计算了一导弹模型在不同方位角下的双站ＲＣＳ,证实了本方法的可行性。     

A fast algorithm for repair-depot reliability-evaluation

The repair-depot (where failed items are replaced with spares and scheduled for repair) system-reliability (RDSR) is the probability that spares are immediately available to replace failed units during the time period of interest, and it is calculated in terms of the constant failure rate for parts under consideration, the number of spare units on-hand (s), and projected repair completion dates for (n-1) units in the repair process, n⩾2. Linton et al. (1995) show an expression for RDSR in terms of n nested sums, where the upper limit of each sum is a function of s. This paper derives a restructured expression (LKYH algorithm) for computing RDSR, and shows that the nested-sum form for RDSR uses O(sⁿ) mathematical operations, while LKYH requires only O(s) mathematical operations. Numerical examples illustrate the increase in efficiency of LKYH; e.g., when n=s=10, the execution time for computing RDSR on a 486/66-computer is reduced from 198 seconds for the multiple-sum form to less than 1 second for LKYH     

A fast algorithm for computing the response of a linear system to a large number of inputs

A method is presented which saves computation time when determining the response of an arbitrary linear time-invariant system, where several input-output responses are desired. The method is based on an assumption that the system input is band-limited.     

一种简单快速的GPS信号捕获方法

结合一般的GPS信号捕获算法,提出了一种更为简单快速的GPS信号捕获方法。此方法在1 023个码片时间约1 ms,可以完成一颗卫星在一个多普勒频移下的全码捕获检测。FPGA仿真表明,与传统的捕获方法相比,所提方法减少了资源消耗与时间消耗,同时保证了能在一个C/A码周期内获取一个多普勒频移下的C/A码相位,捕获更简单快速。     

A new architecture for the fast Viterbi algorithm

A novel architecture design to speed up the Viterbi algorithm is proposed. By increasing the number of states in the trellis, the serial operation of a traditional add-compare-select unit is transformed into a parallel operation, thus achieving a substantial speed increase. The proposed architecture would increase the speed by 33% at the expense of a fairly modest increase in area, thus becoming an attractive approach in high-speed applications. A simple example is shown to illustrate the proposed algorithm in maximum-likelihood sequence detector. A comparative synthesis is made to compare the proposed architecture with other approaches, and synthesis simulations confirm the projection of the throughput gain. Also, the proposed algorithm is extended to the block-processing architecture, and we show that an additional 50% speedup is achieved.     

A fast algorithm for the linear canonical transform

In recent years there has been a renewed interest in finding fast algorithms to compute accurately the linear canonical transform (LCT) of a given function. This is driven by the large number of applications of the LCT in optics and signal processing. The well-known integral transforms: Fourier, fractional Fourier, bilateral Laplace and Fresnel transforms are special cases of the LCT. In this paper we obtain an O(NlogN) algorithm to compute the LCT by using a chirp-FFT-chirp transformation yielded by a convergent quadrature formula for the fractional Fourier transform. This formula gives a unitary discrete LCT in closed form. In the case of the fractional Fourier transform the algorithm computes this transform for arbitrary complex values inside the unitary circle and not only at the boundary. This chirp-FFT-chirp transform approximates the ordinary Fourier transform more precisely than just the FFT, since it comes from a convergent procedure for non-periodic functions.     

A simple and fast probabilistic algorithm for computing square roots modulo a prime number (Corresp.)

A probabilistic polynomial-time algorithm for computing the square root of a numberx in {bf Z}/P{bf Z}, whereP = 2^{S}Q + 1(Qodd,s > 0)is a prime number, is described. In contrast to the Adleman, Manders, and Miller algorithm, this algorithm gets faster as s grows. As with the Berlekamp-Rabin algorithm, the expected running time of the algorithm is independent ofx. However, the algorithm presented here is considerably faster for values ofsgreater than2.     

大型工件单目结构光三维扫描方法

针对大型工件,提出了一种基于单目线结构光三维扫描的方法。通过引入线结构光平面建立了视觉传感器数学模型和多项式模型,并使用高精密手动平移台控制平行线靶标在6个固定位置的移动对相机和光平面进行标定,提高标定的精度和准确度。同时对测量工件部分精准定位有效区域,减小程序运算量。该扫描方法可直接构建传感器的测量坐标系,过程简单,速度较快。通过对大尺寸铝合金铸件进行扫描测试,选取了合适的扫描速度v=1.25 mm/s,在满足精度的前提下提升了工业应用的效率。实验结果证明,此种方法能够有效准确的对物体表面进行重构,平均误差小于0.1 mm,具有较高的精度。     

A fast computer algorithm for switching converters

This paper presents a fast general computer algorithm for an analysis of switching converters including various types of resonant converters. The algorithm deals not only with the analysis of steady-state characteristics, but also with the analysis of dynamic characteristics. Frequency responses are derived very quickly, and stability characteristics are clarified. This paper also introduces an actual simulator program that was developed based on the algorithm. This simulator is so compact that it runs fully on a personal computer. The validity of the algorithm is confirmed by comparing simulation and experimental results     

A fast filtering algorithm for image enhancement

A filtering algorithm for fast image enhancement is described. The algorithm tries to make the minimum modification on the original image structures while it performs noise smoothing at a given filtering level. The filtered image is a weighted combination of four subimages obtained from low-pass filtering the original image along four major directions. The weighting on each subimage is controlled by the differences between these subimages and the original image The resulting image is then nonsymmetrically sharpened to enhance the image structure boundaries, The overall effect of this filtering structure is effective adaptive noise reduction and edge enhancement with an efficient implementation using array processors. The high regularity and parallelism of the algorithm also makes it suitable for its efficient implementation using very large scale integrated (VLSI) circuits or multiprocessor systems. The performance of the algorithm in effectively reducing image noise and preserving/enhancing important image structures is discussed and demonstrated using several MR images from a low-field-strength MR imaging system.