Fast modular multiplications based on precomputations with lessmemory

A fast modular multiplication method based on precomputation is proposed for use in public-key cryptosystems. The proposed method can compute the Montgomery reduction TR¹ mod N only through additions. Furthermore, this is 6.4 times faster than the Montgomery method implemented in modular reduction with a 512 bit modulus when 2.1 MB of memory is used. This memory size is also only 1/4 of that required in the method proposed by Takenaka et al     

Fast coupled adaptation for sparse impulse responses using a partial haar transform

This work presents a novel scheme for identifying the impulse response of a sparse channel. The scheme consists of two adaptive filters operating sequentially. The first adaptive filter adapts using a partial Haar transform of the input and yields an estimate of the location of the peak of the sparse impulse response. The second adaptive filter is then centered about this estimate. Both filters are short in comparison to the delay uncertainty of the unknown channel. The principle advantage of this scheme is that two short adaptive filters can be used instead of one long adaptive filter, resulting in faster overall convergence and reduced computational complexity and storage. The scheme is analyzed in detail for a least mean squares (LMS) LMS-LMS type of structure, although it can be implemented using any combination of adaptive algorithms. Monte Carlo simulations are shown to be in good agreement with the theoretical model for the behavior of the peak estimating filter as well as for the mean square error (MSE) behavior of the second filter.     

The impulse responses of a half-plane

Simple expressions are presented for the fields diffracted by a metallic half-plane when illuminated by an impulsive plane cylindrical or spherical (scalar or vector) wave.     

Fast,compact and symmetric modular exponentiation architecture by common-multiplicand Montgomery modular multiplications

In this paper, the primitive common-multiplicand Montgomery modular multiplication is developed for modular exponentiation. Together with Montgomery powering ladder, a fast, compact and symmetric modular exponentiation architecture is proposed for hardware implementation. The architecture consists of one group of processing elements along the central line and two symmetric groups of accumulation units on two sides. The central elements perform modular reductions, while the symmetric units on both sides accumulate the modular multiplication results. A feedforwarding architecture is employed to decrease the latency between processing elements, in parallel with the word-based accumulation units, which are also pipelined. Meanwhile, due to the symmetric architecture and Montgomery powering ladder, the modular exponentiation is immune from fault and simple power attacks. Implemented in FPGA platform, the performance of our proposed design outperforms most results so far in the literature.     

Fast and flexible CRC calculation

An algorithm for software or hardware implementation is presented, allowing fast computation of cyclic redundancy checks with arbitrary polynomials and a high flexibility, such as updating of checksums after modifying data block parts with a known old checksum.     

Calculating step and impulse responses of networks

An economical method is given for calculating the step response, impulse response and derivatives of the impulse response of a network from a single partial-fraction expansion of the transfer function.     

Spiking filtering of all-pass filter impulse responses

We described spiking filtering of all-pass filter impulse responses. We established a rule about the optimum delay and obtained the optimum spiking filter. We also showed that this result can be successfully applied to additional filtering to increase the resolution even further.     

Main properties of filters’ finite impulse responses

Analogue filters’ finite impulse responses in time and frequency domains are considered as prototypes of digital ones. Main properties which should be taken into consideration during design of stable filtering systems are discussed.     

Fast calculation of the Choi-Williams time-frequency distribution

The method presented allows faster calculation of any time-frequency distribution with a kernel that can be formulated in the time-lag plane. Specific examples are the Wigner and Choi-Williams distributions. The Choi-Williams distribution (CWD) uses an exponential kernel in the generalized class of bilinear time-frequency distributions to achieve a reduction in the cross-term components of the distribution. Matrix manipulations provide an intuitive approach and, when combined with parallel processing, improve the processing speed to allow real-time calculations of the CWD. The use of an outer product matrix with a weighting matrix is particularly useful when evaluating different weighting parameters. For any given signal, the outer product matrix needs to be calculated just once. The various weighting matrices can be stored and used with any signal when needed. Parallel processing architectures allow implementation of the algorithm with speeds that are appropriate for real-time, running window calculations     

一种无乘法的整数DCT快速实现方法

提出了一种无乘法的整数离散余弦变换(DCT)的实现方法:首先将蝶形运算的浮点数放大为整数,将浮点运算转化成定点的整数运算,然后根据蝶形运算的特点,将蝶形中的乘法转化为基于数值移位和累加的运算过程,从而得到一种通用的快速DCT实现方法.     

Hyper-resolution indoor channel impulse responses: multipathcomponents and k-factors

A hyper-resolution method has been used to estimate the wideband indoor channel impulse response at 1.3 GHz in a variety of environments within a building. The number of multipath components N and the Ricean k-factor have been investigated. The effect of the presence of people has also been monitored. The results show that if a 30 dB impulse response dynamic range threshold is considered. A value of N less than 7 is applicable to all cases for >90% of the time. It is also shown that the k-factor can be reliably estimated using only the three strongest components     

快速计算平面分层介质的闭式格林函数

使用离散复镜像方法(DCIM)快速得到平面分层介质的空间域的闭式格林函数,避免了费时的索末菲尔德积分.给出闭式格林函数在矩量法中的应用,为研究微带天线的性能提供了一种数值方法.数值结果表明离散复镜像方法能够快速、准确地计算平面分层介质的闭式格林函数.     

Blind deconvolution of symmetric noncausal impulse responses usingtwo-sided linear prediction

Considers the problem of estimating the time-symmetric, noncausal impulse response of a linear time-invariant system from measurements of the response of the system to an unknown input signal, which is assumed to be a realization of a white random process. The symmetric impulse response is modeled by a two-sided AR or ARMA system model. The two-sided AR coefficients are estimated using a two-step procedure. First, an estimate of an unconstrained parameter vector is computed by solving a close-to-Toeplitz-plus-Hankel system of equations using previously developed fast algorithms. Then, the polynomial square root of the result is obtained by solving a constrained least-squares problem which has a simple solution. Unlike previous methods, this approach requires no iterative procedure. However, it may lead to an unstable model in some extreme cases. Simulation results illustrate the performance of the proposed methods     

Fast transmission line coupling calculation using a convolutiontechnique

A fast method for the calculation of the mutual coupling between transmission lines is presented. The method is based on using the convolution of the incident field and the current induced by a Dirac impulse type field. Only first-order coupling between the lines is taken into account. This means that only the current induced by the source line is taken into account and all currents resulting from induction by this induced current are discarded. The technique is orders of magnitude faster than traditional moment method techniques because no large matrix equations need to be solved     

计算超薄多层介质诱饵温度的快速算法

基于超薄多层介质诱饵温度沿壁厚方向相同的假设,根据质量与能量守恒原理并结合多层介质材料的热物性及厚度参数,推导了多层介质等效为单层介质材料的热物性参数.考虑了热传导、太阳和地球对空间自旋及三轴稳定目标的加热、目标外表面辐射散热和内壁面元间的辐射换热,根据节点网络法建立了传热差分方程,并利用Gauss-Seidel迭代法...     

偶极子天线电流分布的快速分层算法

分层算法(Hierarchical method)是一种电磁场积分方程的加速计算方法,通过一种层次式数据结构替代边界元法生成的稠密系数矩阵,使线性方程组的迭代求解中每一次矩阵-向量乘法运算次数减少到O(n),目前已经应用到集成电路互连线3D电容参数提取中.利用快速分层算法对偶极天线上电流分布和功率增益进行了计算,与矩量法(MoM)的比较显示:在类似精度下,采用分层算法显著地节省了计算时间.     

Fast calculation of co-occurrence matrix parameters for image segmentation

Image segmentation methods based only on grey level information are not suitable for pictures in which regions exhibit almost the same average grey level and differ only for local variations or texture. By extending these methods to textural features, better results are expected. Among textural features, those extracted from co-occurrence matrices are quite effective. A fast algorithm for the calculation of these parameters for windows centred on each pixel of the image is presented.<>     

Triangle impulse response (TIR) calculation for lossy transmission line simulation

Triangle impulse responses (TIRs) for lossy transmission lines are accurately calculated using both an inverse fast Fourier transform algorithm and an accelerated inverse Laplace transform algorithm. Frequency dependent transmission line parameters, i.e., R, L, G, and C, are employed to model the skin effect and the frequency dependent electrical properties of the substrate material. The calculated TIR can be further used to carry out time domain simulations for a large number of lossy transmission lines. Frequency dependent line parameters, R, L, G, and C should be used in specific cases to assure the causality of signal waveform, the accuracy of the time delay, and the amplitude of the waveform evaluations in the time domain.     

Obtaining transfer functions with zero steady-state error from impulse responses

A technique is presented for obtaining approximations to the transfer function of a plant (by modelling the plant's impulse response by a linear combination of orthonormal functions) so that the steady-state responses of the plant and its approximation are the same for constant input. An example is given.     

Electromagnetic-field impulse responses of insulated and noninsulated cylinders embedded in seawater

Infinitely long insulated and noninsulated cylinders embedded in seawater and excited by an electric dipole are considered. The impulse responses and profile characteristics of the cylinders are obtained.