RCS reduction of a conducting cone-cylinder using an active method

This paper presents an active method for reducing the radar cross section (rcs) of a perfectly conducting cone-cylinder. The active elements are four microstrip patch antennas located symmetrically along the conecylinder axis. These elements radiate a field which permit the total scattered field in the direction of the receiver to be close to zero. In each time step, the hoarded system should determine some parameters of the incident wave: the incident direction, its frequency, amplitude, and phase. Then when antennas are fed with currents of suitable amplitude and phase, they radiate an electromagnetic field in the direction of the receiver that has the same amplitude but is opposite in phase compared to the scattered field, without feeding patches. Then the total field vanishes in the direction of the receiver.     

The RCS of a microstrip antenna on an in-plane biased ferritesubstrate

The numerical solutions for the RCS of a microstrip patch on an in-plane biased ferrite substrate are presented. The peaks in the RCS can be moved with respect to frequency by changing the magnetic bias field. We consider a monostatic RCS with various incident angles and examine all four elements of the cross-section matrix. For the case of an unmagnetized ferrite substrate the cross-polarized RCS components are zero. When the ferrite is magnetized, the cross-polarized RCS components become as significant as do the copolarized RCS components. It is also shown that a loaded patch has the effect of significantly reducing RCS at resonances. The analysis used is based on a full-wave moment method with the exact spectral-domain Green's function     

Analysis of an inhomogeneous bulk "S-shaped" negative differential conductivity element in a circuit containing reactive elements

This paper analyzes the time and space evolution of the current density distribution in an inhomogeneous bulk "S-shaped" negative differential conductivity (SNDC) element and the response of the surrounding lumped element circuit. The SNDC element, in series with a package inductance, is in parallel with a package capacitance, the loop being in series with a load resistance and a battery. First the presence of isothermal current density filamentation in SNDC elements is demonstrated. By approximating the SNDC element as an appropriate conductive voltage curve in series with an appropriate intrinsic inductance, it is next shown that various modes of behavior (switching, relaxation oscillations, and a bias induced transition between the two) can all occur in the same SNDC element for appropriate values of the circuit parameters. A major aspect of the circuit theory is that it transforms directly between S and N shaped NDC elements when the important reactive components are identified in each case (duals). The techniques used are applicable to all SNDC elements, such as p-n-p-n and p-i-n diodes, and Ovonic threshold switches; emphasis is placed on the latter.     

Reliability evaluation of a repairable network with limited capacity and structural redundancy

A repairable network with limited capacity is considered. Every link and node of a network can be presented by a structural component consisting of an individual element or a group of elements with different kinds of structural redundancy. Repairs of failed elements are carried out in the process of network operation. The number of elements that are serviced by a repair centre is usually greater than the number of repair units in this centre—so called limited repair. Therefore, a queue of failed elements may arise in the repair centre, which causes statistical interdependence of elements and components of the network. A method and models for computing steady-state availability, mean time to failure (MTTF) and mean time to repair (MTTR) of the repairable network with structural redundancy and limited capacity are presented. The proposed method and models are implemented in the application program package used for reliability evaluation of computer networks and distributed systems.     

Sloshing suppression control of liquid transfer systems considering a 3-D transfer path

In plants in many industries, there exist a lot of transfer systems with vibration mechanisms. While transfer without residual vibration is usually demanded in these plants, this requirement necessitates large numbers of sensors and complicated models for control design. Therefore, This work presents a trajectory control design method to suppress residual vibration in transfer systems without the need to directly measure vibration. The proposed method consists of two parts. First, the frequency characteristics of the controller, comprised of control elements with simple structures such as a notch filter and a low-pass filter, are shaped as needed to suppress vibration. Next, various parameters of the control elements are determined by solving an optimization problem with penalty terms expressed by the constraints of both the time and frequency domains. The proposed method is applied to a liquid container transfer system, with special consideration given to the suppression of sloshing (liquid vibration) as well as to the maintenance of a high-speed transfer on the container's three-dimensional transfer path. The obtained controller demonstrates good performance for all demands. The effectiveness of the control design method is shown by experiments.     

Simple determination of all capacitances for a set of parallelmicrostrip lines

A fast and moderately accurate method to describe the complicated dependence on design and process parameters of coupling capacitances between a set of parallel lines is presented in this paper. It involves only one circuit-dependent parameter at a time. This is accomplished by calculating the capacitance coefficient matrix through inversion of a potential coefficient matrix with much simpler dependence on geometry. Self elements are approximately independent of the presence of other lines, and mutual elements do not depend on linewidths or interfering lines as long as the ground is sufficiently far away. The potential coefficients are derived by inverting one- or two-line capacitance matrices that are either theoretically calculated or determined by measurements on integrated circuit (IC) test structures. Look-up tables for a specific IC process can then be constructed with only linewidth as the parameter for self potential elements and distance between line centers as parameter for mutual potential elements. General algorithms have been derived for microstrip on one or two layers of dielectric     

Analysis of a cylindrical antenna containing an aperture coupledload

In this paper we present the basis for the analysis of shielded tuning networks coupled to wire antenna elements. The structure analyzed comprises three conducting cylindrical tubes that form an aperture-fed circular coaxial waveguide. Two methods are presented for formulating and solving integral equations for the structure. The first method is based on the mixed potential electric field integral equation enforced on the three cylindrical tubes, and the second is based on aperture theory. An end correction capacitance is used to adjust the reflection coefficient in the eigenmode expressions of the aperture method. The data obtained by the two methods are in close agreement. Differences in actual currents and equivalent currents obtained from solutions are discussed and reconciled     

基于AutoCAD自动建模技术的任意形状导体电容MoM计算

该文首先研究了任意形状导体的AutoCAD自动建模,得出了基于三角形面片的任意形状导体表面的模型.接着着重研究了利用矩量法求解任意形状导体的理论基础,推导出了任意三角形自作用单元的解析公式以及互作用单元的数值解。最后,给出了一些二维,三维的任意导体的数值结果,并且给出了这些数值结果的Richardson外推值,计算结果与文献以及精确解都吻合的比较好,从而说明了该方法的有效性和准确性。     

Simulation model for a silicon Hall sensor in an absolute digital position detection system

The performance of a digital position detection system with silicon Hall sensors for the detection of coded absolute position data has been investigated. The position information is fixed in one single track as a maximum length sequence of bits by means of longitudinal saturation recording in a hard-magnetic layer. The Hall elements are positioned with their surface parallel to the hard-magnetic layer.An efficient computer simulation model has been realized which calculates the response of a Hall element in the fringing field. The computed results are compared with experimental data on Hall elements which were realised using MOS-IC technology. The simulation model appeared to be sufficiently accurate for a first-order estimation of the performance of an absolute position detection system on the basis of silicon Hall elements. The resolution which can be realized depends strongly on the noise level in the elements and will be of the order of a few hundred μm.     

Reliability evaluation of a communication system considering a multistate model

The methods most often suggested for reliability evaluation of communication systems/flow networks consider two states, namely the good state and the bad state. This paper considers multistate modelling of the network elements. The states which permit a flow less than the maximum assigned capacity are assumed as parallel and mutually exclusive elements in the network. A method is proposed for reliability evaluation of a communication network considering multistate modelling of the network elements. The proposed method has been implemented on a computer and results obtained using the proposed method are compared with the existing methods for the two state model conditions.     

Application of the Monopulse Technique to a Planar Array of Nonlinearly Loaded Straight-Wire Coupled Antennas

The radiation and reception characteristics of a planar array of straight-wire coupled antennas are analyzed by a numerical method in the time domain. The numerical method allows us to calculate some significant magnitudes in an array of coupled wire antennas, such as the frequency dependence of the self- and mutual impedances between antennas. The antennas are fed by a time-varying Gaussian pulse, and they are loaded with various nonlinear elements to exert some control over the radiation field. The results are used to show how the monopulse technique with the slope pattern promises a much higher accuracy of angle measurement for a target.     

Plane-wave expansion for arrays of arbitrarily oriented piecewise linear elements and its application in determining the impedance of a single linear antenna in a lossy half-space

An infinite array of arbitrarily oriented identical elements with arbitrary identical currents is considered. The field from this array is expanded into plane inhomogeneous waves, and the mutual impedance between the array elements and an exterior arbitrarily oriented element is derived. The formulation is particularly useful when the array is located adjacent to a dielectric interface. Numerical examples are given and the relationship to earlier formulations pointed out. It is further shown that the impedance of a single element can be obtained as the average of the scan impedance taken over the entire hemisphere (called the array scanning method (ASM)). This technique has a clear physical interpretation which greatly facilitates its uses, which include the moment method solutions of wire antennas as applied to the Sommerfeld integral. Numerical evaluation is straightforward when the dipole is in the lossy half-space, and the utility of the method is demonstrated by the presentation of results for the input impedance of dipoles in a variety of half-space environments. Solution is by Galerkin's method with a piecewise sinusoidal expansion for the current. Computer time is proportional tod^{-1}, wheredis the distance of the dipole to the interface. For conducting media and low frequencies an approximation is made to reduce computation time. The moment method solution of a dipole buried at a depth as small as 1/150000 wavelength in the earth is presented.     

Implementation of uniform and simultaneous ART for 3-D reconstruction in an X-ray imaging system

The authors propose a 3-D volume reconstruction method using X-ray images with a calibration method to implement it in an X-ray imaging system. Previously the authors have proposed an advanced 3-D reconstruction algorithm based on an algebraic reconstruction technique (ART), called a uniform and simultaneous ART (USART). In practice, however, there are two main issues in implementing it in a realised X-ray imaging system. The first one is the huge computation time and memory required in achieving 3-D volume, which is a common limitation in most ART methods. The second issue is the system calibration for determining the geometry of the X-ray imaging conditions needed for the ART method. These two critical problems are addressed. A fast computing model of USART is proposed, where spherical voxel elements are employed in computation to reduce the computation time and memory. Then, a calibration method is proposed to identify the X-ray imaging geometry based on a cone beam projection model. For this purpose, a set of X-ray images of a reference grid pattern is used and the X-ray source positions are determined from the analysis of the image features, the centres of the grid points in the X-ray images. The validity of the proposed 3-D reconstruction method is investigated using a series of experiments.     

TM scattering by an impedance sheet extension of a paraboliccylinder

An integral equation and method of moments (MM) solution are presented for the two-dimensional (2-D) problem of transverse magnetic (TM) scattering by an impedance-sheet extension of a perfectly conducting parabolic cylinder. An integral equation is formulated for a dielectric cylinder of general cross section in the presence of a perfectly conducting parabolic cylinder. It is then shown that the solution for a general dielectric cylinder considerably simplifies for the special case of TM scattering by a thin multilayered dielectric strip that can be represented as an impedance sheet. The solution is termed an MM/Green's function solution, where the unknowns in the integral equation are the electric surface currents flowing in the impedance sheet; the presence of the parabolic cylinder is accounted for by including its Green's function in the kernel of the integral equation. The MM solution is briefly reviewed, and expressions for the elements in the matrix equation and the scattered fields are given. Sample numerical results are provided     

Broadbanding of a Planar Antenna with Three Frequency Bands and Its Application

This paper describes a line element planar antenna with three frequency bands. To obtain broadband characteristics, a modified planar antenna that has semielliptical elements based on the characteristics of a line element planar antenna is proposed and analyzed by the finite difference time domain method. Return loss characteristics are discussed as functions of the eccentricity values of semi‐ellipse at each element. The broadbanding of the modified planar antenna is implemented based on the results. The planar antenna with three systems (an 800 MHz band cellular phone, a third‐generation cellular phone, and a 2.4 GHz band wireless LAN system) is considered as an application example.     

A method for calculating the transient time of a multi-stage thermoelectric cooler

The transient time τ of a cascade thermoelectric cooler is calculated. The method applied does not involve the solution of the heat equations with partial derivatives for semiconductor elements. The transient time τ of a two-stage thermopile was obtained in analytical form as a solution of the quadratic equation whose coefficients depend on semiconductor thermoelectric parameters, the specific heat of the thermopile materials, and the sizes of different parts of the cooler. For a thermopile with an arbitrary number of stages N, the calculation was reduced to the standard problem of finding the eigenvalues of two symmetrical matrices of order N. The calculated values of τ for specific two-stage thermopiles are in satisfactory agreement with the experimental data.     

Features of formation of the patterns of a monopulse active phased array antenna with a dome lens

A method for the control of the transmission coefficients of antenna elements of a system comprising an active phased array antenna (APAA) and a dome lens, which ensures formation of a deep boresight null of the elevation difference pattern, is proposed. The effect of the control method on the characteristics of receiving monopulse channels of the APAA depending on the intrinsic noise of antenna elements is analyzed. The results of the well-known theory of reception of a nonplane wave by an antenna with continuous aperture are extended to the case of an array antenna.     

用MOM-UTD混合方法计算共形天线阵单元间的互耦

采用矩量法(MOM)结合一致性绕射理论(UTD)来计算共形天线阵单元间的互耦。这种混合方法通过UTD来修正MOM中的广义阻抗矩阵将理想导体曲面对天线的影响考虑在内。克服了单独采用这两种方法的缺点。既减少了计算量又达到了一定的精度。计算结果与文献中已有的结果吻合得相当好。     

Sweeping-TXRF: a nondestructive technique for the entire surface characterization of metal contaminations on semiconductor wafers

We propose a new mode of total reflection X-ray fluorescence (TXRF) analysis called "Sweeping-TXRF" for the characterization of wafer surface contaminations in semiconductor manufacturing. Essentially, Sweeping-TXRF is the mapping of an entire surface with a very short data acquisition time for each individual spot. Sweeping-TXRF provides three-dimensional views for individual elements on a wafer in a very short period of time, a method that had never before been achieved by traditional methods. Dedicated software for this method was developed and tested, and the results are quite promising for routine contamination characterization.     

Optimal Characteristics of an Arbitrary Receive Antenna

Several fundamental questions about the operation of receiving antennas are addressed, such as “Why does a receiving antenna scatter an incident field?” and “Under what conditions does a receive antenna capture all of the available incident power?” A new method is described by which the received power can be maximized for an arbitrary receiving antenna. The technique is first illustrated for two-dimensional infinite receiving arrays of electric and/or magnetic dipole elements, which result in simple plane waves for the scattered (re-radiated) fields. Optimal results (for maximum received power) are derived for several cases, and it is established that half the available incident power may be received by an array of electric (or magnetic) elements in free space, and that all available incident power may be received by an array that combines electric and magnetic elements, or one that incorporates a ground plane. Next, an arbitrary finite three-dimensional antenna enclosed by a mathematical spherical surface is treated using spherical vector wave functions. It is shown that half the available incident power can be received by such an antenna consisting of either TM or TE only elements, while all available incident power can be received when both TM and TE elements are used. It is also shown that the absorption efficiency for any optimal arbitrary antenna is 50%.