Linear lumped loads in the FDTD method using piecewise linear recursive convolution method

This letter gives a new algorithm to include linear lumped elements into finite difference time domain algorithm. The proposed method can efficiently account for two-terminal networks made of several lumped elements. The piecewise linear recursive convolution (PLRC) technique is used to implement lumped loads into Yee cells. Using this method, it is possible to simulate equivalent circuits of terminations for microstrip structures, integrated circuits, or digital devices. The advantage of the PLRC technique is addressed and simulation results validating this method are presented.     

State-space FDTD implementation of anisotropic perfectly matched layer

New formulations based on the state-space approach are presented for implementing the anisotropic perfectly matched layer into the finite difference time domain (FDTD) algorithm. The formulations are simple and independent from the material properties of the FDTD computational domain. Numerical tests are included to validate the proposed formulations.     

磁化等离子体覆盖二维导体目标FDTD分析

采用z变换方法把FDTD推广应用于二维各向异性色散介质－磁化等离子体中,该算法同时解决了电磁波在各向异性和频率色散介质中传播的问题,给出了各向异性磁化等离子体中FDTD迭代公式.计算了各向异性磁化等离子体涂敷Von Karman型导体柱前后其单站RCS的变化情况,分析了等离子体参数对其RCS的影响.结果表明恰当地选择等离子体参数能有效地减少目标的RCS.     

An FDTD formulation for dispersive media using a current density

A novel finite-difference time-domain (FDTD) formulation for dispersive media called the JE convolution (JEC) method is derived using the convolution relationship between the current density J and the electric field E. The high accuracy of the JEC method is confirmed by computing the reflection and transmission coefficients for a nonmagnetized plasma slab in one dimension. It is found that the new method has an accuracy comparable to the auxiliary differential equation (ADE) while having the same computational efficiency as the less accurate recursive convolution (RC) method. Numerical simulations also show that the JEC method exhibits significantly higher accuracy than the RC method in modeling wave attenuation inside the plasma     

Digital filtering technique for the FDTD implementation of the anisotropic perfectly matched layer

A new algorithm is presented for the finite difference time domain (FDTD) implementation of the anisotropic perfectly matched layer (PML) using the digital signal processing. The algorithm is based on modeling the anisotropic PML region as a set of infinite-impulse response (IIR) digital filters. The advantage of the proposed method is that it allows direct FDTD implementation of Maxwell's equations in the PML region. In addition, the formulations are implemented using D and B fields rather than E and H, and this allows the PML to be independent from the material properties of the FDTD computational domains. Numerical tests have been carried out in two dimensions to validate the formulations.     

碰撞等离子体的高阶FDTD算法

给出了电磁波在均匀、碰撞等离子体中传播的四阶时间和四阶空间FDTD算法.该算法比Yee氏FDTD算法每一个网格每一维增加一个存储单元,与常规的二阶等离子体FDTD算法相同.由于采用四阶时间和四阶空间近似,因此该算法能有效地减小数字色散误差,其频带宽度比二阶算法的频带宽度更宽.为了验证该高阶算法的正确性,对均匀、碰撞等离子体平板的电磁波反射系数进行了计算,并与解析结果、二阶FDTD计算结果进行了比较,证明了该算法的高效和精确.     

Piecewise linear implementation of nonlinear dynamical systems: from theory to practice

It is shown how to implement by a mixed-signal circuit a continuous-time dynamical system. The chosen case study is the Hindmarsh-Rose model of a biological neuron, but the design strategy can be applied to a large class of continuous-time nonlinear dynamical systems. The system nonlinearities are first approximated by using piecewise-linear functions and then digitally implemented on a field programmable gate array. The linear part of the system is completely analogue and is implemented by using operational amplifiers. Measurement results show that the circuit can reproduce the main dynamics of a biologically plausible neuron.     

Z-transform-based FDTD algorithm for anisotropic perfectly matched layer

An efficient method based on the Z-transform theory and the D-H anisotropic perfectly matched layer formulations is presented for truncating general FDTD grids. The formulations are simple and independent of the material properties of the FDTD domain. Numerical examples for radiation and guided-wave problems are included to validate the proposed formulations.     

Piecewise linear CAD model for avalanche photodetectors

A simple CAD model for avalanche photodetectors (APD) is developed. The model is based on a piecewise linear (PWL) approximation of the responsivity curve of the APD which may be obtained either from theoretical considerations or from terminal measurements. The model takes into account nonlinear effects in the design of APD optical receivers.     

Piecewise linear detection for direct superposition modulation

Considering high-order digital modulation schemes, the bottleneck in consumer products is the detector rather than the modulator. The complexity of the optimal a posteriori probability (APP) detector increases exponentially with respect to the number of modulated bits per data symbol. Thus, it is necessary to develop low-complexity detection algorithms with an APP-like performance, especially when performing iterative detection, for example in conjunction with bit interleaved coded modulation. We show that a special case of superposition modulation, dubbed Direct Superposition Modulation (DSM), is particularly suitable for complexity reduction at the receiver side. As opposed to square QAM, DSM achieves capacity without active signal shaping. The main contribution is a low-cost detection algorithm for DSM, which enables iterative detection by taking a priori information into account. This algorithm exploits the approximate piecewise linear behavior of the soft outputs of an APP detector over the entire range of detector input values. A theoretical analysis and simulation results demonstrate that at least max-log APP performance can be reached, while the complexity is significantly reduced compared to classical APP detection.     

任意磁偏角磁化等离子体的PLRC—FDTD算法

把运用于处理各向同性媒质的分段线性递归卷积时域有限差分(PLRC-FDTD)方法进行拓展,用它处理任意磁偏角磁化等离子体的电磁问题,给出了该算法相应的递推计算公式,计算了任意磁偏角磁化等离子体平板对电磁波的反射系数和透射系数,算法结果与解析解相比吻合很好,从而验证了该算法用于任意磁偏角磁化等离子体的有效性和高精度.此外,当电磁波传播方向与外加磁场方向成任意取向时,反射系数和透射系数幅度的图像形状是相似的,都在等离子体频率处发生一个明显的突变.     

Algorithm for linear convolution using number theoretic transforms

A linear convolution of two N-point sequences is computed by using N-point Fermat number transforms, so that the convolution length is doubled for a given modulo Fermat number. The algorithm is also suitable for other convolutional algorithms of number theoretic transforms     

New recursive algorithm for solving linear algebraic equations

The authors present a new recursive algorithm for solving linear algebraic equations Ax=b. With this algorithm, the ith step recursion can find one solution of the first i equations; the unique solution of the total n equations could be found after the nth step recursion. Because of this recursive property, the algorithm can be used not only in solving ill-conditioned equations but also in recursive identification, signal processing and many other areas.<>     

JEC-FDTD for 2-D conducting cylinder coated by anisotropic magnetized plasma

The JE convolution finite-difference-time-domain (JEC-FDTD) method is extended to the anisotropic magnetized plasma which incorporates both anisotropy and frequency dispersion at the same time, enabling the transient solution of the electromagnetic wave propagation in anisotropic magnetized plasmas. Two-dimensional JEC-FDTD formulations for magnetized plasma are derived. The back scattering radar cross section (RCS) of a perfectly conducting cylinder coated by a layer of magnetized plasmas is calculated.     

A linear systolic array for recursive least squares

Classical systolic design procedures rely on linear or affine space-time transformations because of the well-understood properties of linear operations. In order to increase the efficiency of the final processor, various ad hoc manipulations applied to transformations that appeared to be nonlinear at the physical array level have been proposed. Folding is one of these possible transformations. The authors show that folding can actually be considered to be an overall linear procedure by artificially increasing the dimensionality of the dependence graph of the algorithm. A 1-D array for recursive least squares is also derived as an application of a systematic linear design procedure including folding     

An anisotropic perfectly matched layer-absorbing medium for thetruncation of FDTD lattices

A perfectly matched layer (PML) absorbing material composed of a uniaxial anisotropic material is presented for the truncation of finite-difference time-domain (FDTD) lattices. It is shown that the uniaxial PML material formulation is mathematically equivalent to the perfectly matched layer method published by Berenger (see J. Computat. Phys., Oct. 1994). However, unlike Berenger's technique, the uniaxial PML absorbing medium presented in this paper is based on a Maxwellian formulation. Numerical examples demonstrate that the FDTD implementation of the uniaxial PML medium is stable, equal in effectiveness as compared to Berenger's PML medium, while being more computationally efficient     

FDTD implementation for magnetoplasma medium using exponential time differencing

The electromagnetic propagation in dispersive magnetoplasma medium is modeled using the finite-difference time-domain (FDTD) method based on the exponential time differencing (ETD). The ETD schemes with first-order and second-order accuracy are presented. The ETD algorithm is accurate and efficient. The reflection and transmission coefficients of the magnetized slab for the right-hand circularly polarized wave are computed.     

实现MIMO系统串行干扰消除迫零检测的快速递归算法

针对贝尔实验室分层空时架构中串行干扰消除迫零检测复杂度较高的问题,提出了一种低复杂度快速递归算法,并给出该算法的快速实现方案及其复杂度分析。理论分析与仿真结果表明,与快速递归算法(FRA)相比,所提算法具有低复杂度、易于实现和低存储需求等优势,且其误码性能在实际条件下接近最优,因此具有较高的实用性和良好的应用前景。     

A recursive linear detection algorithm for asynchronous CDMAcommunication system

A recursive linear detection algorithm is proposed for the detection of signals from an asynchronous direct-sequence code-division multiple-access (DS-CDMA) communication system. This algorithm works for short as well as long codes. Under some reasonable conditions, this algorithm is proved to be stable and converges to the ideal decorrelating detector (IDD) with a sufficiently large memory length. The performance of the algorithm is analyzed in some detail. Upper and lower bounds for the bit-error probabilities are developed. It is demonstrated that the two bounds converge to the bit-error probabilities of the IDD as the large memory length increases. Simulation results show that the recursive detector proposed outperforms the truncated decorrelating detector with less memory and less computational complexity     

A recursive least squares implementation for LCMP beamforming underquadratic constraint

Quadratic constraints on the weight vector of an adaptive linearly constrained minimum power (LCMP) beamformer can improve robustness to pointing errors and to random perturbations in sensor parameters. We propose a technique for implementing a quadratic inequality constraint with recursive least squares (RLS) updating. A variable diagonal loading term is added at each step, where the amount of loading has a closed-form solution. Simulations under different scenarios demonstrate that this algorithm has better interference suppression than both the RLS beamformer with no quadratic constraint and the RLS beamformer using the scaled projection technique, as well as faster convergence than LMS beamformers