A technique for approximating the location of surface- and leaky-wave poles for a lossy dielectric slab

An approximation technique for locating the surface- and leaky-wave poles for a lossy dielectric slab is presented. The problem is reduced to the simultaneous solution of two transcendental equations (for each of the perfect magnetic conductor (PMC) and perfect electric conductor (PEC) cases) which is shown to yield a simple approximate solution for the poles, and which can subsequently be refined using numerical optimization. The technique yields both surface-wave and leaky-wave poles, and results are presented for a typical example to demonstrate the approach. The greatest approximation accuracy was observed for surface-wave and leaky-wave poles well removed from the spectral gap. For poles either within or in close proximity to the spectral gap, an alternative iterative technique is proposed. Expressions for the number of proper plus improper surface-wave poles in a given problem are also derived.     

Application of the matrix pencil method for estimating the SEM(singularity expansion method) poles of source-free transient responsesfrom multiple look directions

The matrix pencil method has been utilized for estimating the natural resonances from different transient responses recorded along multiple look directions as a function of time after the incident field has passed the structure. The novelty of this article is that a single estimate for all the poles are done utilizing multiple transient waveforms emanating from the structure along multiple look directions. The SEM poles are independent of the angle at which the transient response is recorded. The only difference between the various waveforms are that the residues at the various poles are of different magnitudes. Some of the residues may even be zero for some of the poles indicating that the contribution from certain SEM poles may not be significant along that look direction. Here all the waveforms are utilized providing a single estimate for the poles without performing an arithmetic mean of the various waveforms     

一种雷达目标极点提取方法及极点特性的分析

散射物体复自然谐振频率(极点)是目标识别可以利用的一个重要特征。使用传统求解极点的方法,通常得到的极点数目比较多,并且存在TE、TM两种模式。因此,对极点的规律分析较多的是对其模式变化趋势的分析。这些特性对于极点的实际应用没有太大的意义。本文从频率矩量法得到的散射数据出发,提出了一种波形拟合的极点提取方法。以有限长柱和椭球为例。分析了极点与入射波模式、目标姿态的关系,得到有实际指导意义的结论。     

Selection of Contributing Natural Poles for the Characterization of Perfectly Conducting Targets in Resonance Region

In the resonance region, the radar scattering response of any target can be modeled by natural poles, with the formalism of the singularity expansion method. The mapping of poles gives useful information for the discrimination of radar targets. In this paper, we show that a reduced number of natural poles is sufficient to characterize such objects. Furthermore, we propose a procedure for selecting the poles that actually contribute to the scattering response. Results are presented for various perfectly conducting (PC) canonical targets and for a PC complex shape target.     

目标电磁散射极点的不变性特征分析

对频域磁场积分方程在离散化的基础上进行了矢量分析，发现离散化后的矩阵方程中含有频率因子的算子矩阵仅包含了反映散射体形状的矢量信息，从而得出极点的分布只依赖于目标的外部形状信息这一结论；然后利用FDTD进行了仿真研究，从不同姿态角(散射方向)的后时响应数据中提取了极点，结果保持了较好的一致，进一步证实了目标姿态角的改变不会影响极点的分布这一特征。     

Extensions of the method of poles for code construction

The method of poles is a method introduced by Franaszek (1969) for constructing a rate-1:1 finite-state code from k-ary data into a constrained channel of finite type whose capacity is strictly greater than log(k). The method is based on the computation of a set of states called poles. With each pole is associated a set of paths going from this pole to others. Each set verifies an entropy condition. The code produced by the method of poles has a sliding-block decoder if each set of paths satisfies moreover an optimization condition based on the sum of the path lengths of the set. We give a new optimization condition which guarantees the sliding-block window decoding property and has a lower computational complexity than the previous one. We also extend the method of poles to the more general case of sofic constrained channels.     

Fast method of channel equalisation for speech signals and itsimplementation on a DSP

Blind equalisation of a speech signal that has been passed over a linear filter can be achieved by estimating the poles of the signal and separating the stationary poles due to the filter from the time varying poles due to the speech. However, identification of the position of the stationary poles, conventionally done by pole clustering, is unreliable and slow. A new algorithm for the identification of stationary poles is presented which is more accurate and faster than clustering     

任意形状导体目标的极点求解

从理论上求解极点,频域矩量法结合围线积分是通用且准确的方法,但由于计算量大而一直用于处理旋转对称目标的求解.本文提出Chebyshev多项式展开格林函数的方法,把频率因子从电场积分方程中分离出来,实现了多频点矩量法的快速计算,解决了任意形状导体目标极点的求解问题.最后对围线积分方法进行适当改进,并求解了三种目标的极点.     

A note on the method of poles for code construction

The method of poles is a method for constructing a rate 1:1 finite state code from K-ary data into a constrained channel S, where S is recognized by a given local automaton and S has capacity at least log(k). We characterize those automata to which the method of poles applies in the case where h(S)=log(k). The code produced by the method of poles has a sliding-block decoder. We also give an upper bound on the window length of the decoder that applies when h(S)⩾log(k)     

空间目标的联合矩阵束极点估计

极点作为谐振区雷达目标的最主要电磁特性,具有很大的空间目标识别前景。但是在使用频域观测数据提取目标极点时,存在虚假极点和估计精度问题。针对上述问题,首先通过加窗和截断改进了后时响应信号的获取流程,抑制了虚假极点影响;然后采用最小描述长度法（MDL）估计极点个数,避免了定阶错误引起的虚假极点;最后采用联合矩阵束法估计极点,有效减少了单角度数据估计极点时存在的遗漏极点和虚假极点问题。FEKO软件验证表明,所提算法具有更高的精度和抗噪能力。     

A Low-Pass Prototype Network Allowing the Placing of Integrated Poles at Real Frequencies

This paper details a procedure by which a number of attenuation poles can be placed at differing frequencies, giving an asymmetric or symmetrical response, the only restriction being that the network must be physically symmetrical. If a number of poles are placed on one side of the passband, this technique can be used to greatly increase the selectivity of a filter on this side, while maintaining an equiripple passband response. There are four possible arrangements for these filters. They can have even or odd degree with an even or odd number of integrated poles. Only three of these are realizable in a symmetrical network and these possibilities are dealt with individually. An example is given in the case of an odd-degree filter with an odd number of integrated poles placed at two frequencies on opposite sides of the passband.     

A discussion of various approaches to the identification/approximation problem

The identification/approximation of a linear system by poles and residues from a measured finite length input-output record of the system is discussed. The objective of this paper is to illustrate that several different formulations for characterizing the impulse response of a system yield the same set of poles.     

Reducing the number of multipliers in the parallel realization ofhalf-band elliptic IIR filters

It is shown in this correspondence that a halfband IIR filter with the poles on the imaginary axis can be derived by the bilinear transformation of an elliptic minimal Q-factors analog prototype. For an odd degree transfer function, the residues at the poles are real or imaginary. Consequently, in the parallel realization, the number of multipliers can be reduced by half     

Pole sensitivity of the quadratic optimal regulator

A matrix associated with the quadratic optimal linear regulator and containing, as elements, the performance-index matrices is used to derive sensitivity formulas for the closed-loop poles of the system. The dependence of these poles on the performance-index matrices is established for both continuous and discrete systems.     

Extraction of electromagnetic target poles from multiple scattered fields with damped Min-norm method

In this study, the estimation of complex natural resonance frequencies (target poles) by using damped minimum-norm (DMin-norm) method is presented. The method mainly utilizes from the scattered fields belonging to multiple aspect angle/polarization cases of a target in resonance scattering region. By employing DMin-norm algorithm, the proposed method constitutes a function from which target poles can be efficiently extracted as its roots. However, the method in its conventional form should be executed as many times as the number of scattered fields to collect sufficient number of resonance frequencies. Therefore, the method is further improved in terms of computational time to acquire target poles with a single process for multiple scattered data. The described method is applied to a dielectric sphere having high number of target poles and good agreement between estimated and theoretical poles is observed.     

The nondominant poles of a distributed-active low-pass network

Expressions are derived relating the nondominant pole locations of a distributed-active low-pass network to the dominant pole locations, and relating the Q of the nondominant poles to the Q of the dominant poles. It is shown that, in general, the effect of the nondominant poles is very small.     

Procedure for the generation of equiripple functions

Equiripple polynomials and rational functions find extensive use in the design of filters. An nth-order equiripple polynomial is obtained by the expansion of the function cos (n cos?1 ?). Equiripple rational functions with specified poles can be obtained using either the method of Darlington or that of Sharpe. In the letter, a different procedure is given that can be used to generate either equiripple polynomials or rational functions with specified poles and equiripple magnitude.     

A technique for extracting the poles and residues of a system directly from its transient response

A novel approach for systematically deriving the complex poles and residues of a structure from a set of time-domain data is presented. The method is based on Prony's algorithm which involves the inversion of two matrices and a solution of the zeros of annth degree polynomial,nbeing the number of desired poles. Two numerical examples are presented and several numerical advantages of this method are discussed.     

R半径DFT在系统盲辨识中的应用

针对通信侦察中系统盲辨识的实际应用要求,提出一种基于R半径DFT技术粗略检测全盲系统零极点的方法。构造系统输出信号的含有R半径参数的辅助信号,通过计算辅助信号的DFT实现对原信号不同半径上傅里叶变换的DFT采样,检测R-DFT平面的极值点得到线性系统零极点的粗辨识。该方法无需系统的任何先验信息,有利于通信侦察方的技术实现。仿真实验验证了算法的有效性和可行性。     

Hybrid torque modeling of spherical actuators with cylindrical-shaped magnet poles

A ball-joint-like three-degree-of-freedom (3-DOF) spherical actuator which features a ball-shaped rotor with multiple permanent magnet (PM) poles and a spherical-shell-like stator with air-core coils is proposed to achieve omni-directional smooth motion in only one joint. Unlike previous study in which dihedral-shaped PMs are employed as the rotor poles, this paper utilizes cylindrical-shaped PMs to facilitate the fabrication and reduce the system cost significantly. Torque output of the spherical actuator is formulated with a hybrid method, i.e., using both analytical and experimental methodologies. Specifically, the analytical torque model of spherical actuator with dihedral-shaped PM poles is derived. Then a research prototype with cylindrical-shaped PM poles is developed, and a torque measurement testbed is built up to conduct experiment on the prototype. As the torque variation trend of actuators using two different types of PM poles with respect to the rotor orientation is similar, parameters in the analytical model are adjusted to fit with the experimental measurements. The resulting torque model can be employed for real-time motion control of the actuator. The cylindrical-shaped PM poles also reduce the inertial moment of the rotor by 60%, which is favorable for achieving better dynamic performance of the spherical actuator.