A novel technique to the solution of transient electromagnetic scattering from thin wires

Previous approaches to the problem of transient scattering by conducting bodies have utilized the well-known marching-on-in-time solution procedures. However, these procedures are very dependent on discretization techniques and in many cases lead to instabilities as time progresses. Moreover, the accuracy of the solution procedure cannot be verified easily and usually there is no error estimation. Recently an alternate approach to the solution of transient scattering by thin wires was presented based on the conjugate gradient (CG) method. In this procedure, space and time are discretized independently into subintervals and the error is minimized iteratively. Unfortunately, this procedure is very slow, not easily extendable to other geometries, and moreover, some of the advantages of marching-on-in-time are lost. In this paper, again the conjugate gradient method is applied to solve the above problem, but this time, reducing the error to a desired value at each time step. Since the error is reduced at each time step, marching-on-in-time can still be done without error accumulation as time progresses. Computationally, this procedure is as fast as conventional marching-on-in-time. Thus, this new method retains all the advantages of marching-on-in-time and yet does not introduce instabilities in the late time. It is also possible to apply this procedure to other geometries. Details of the solution procedure along with numerical results are also presented.     

Some thoughts about transient radiation by straight thin wires

The paper discusses, from a physical point of view, several basic features related to the transient radiation of electromagnetic waves by straight thin-wire antennas     

Calculation of the SEM parameters from the transient response of a thin wire

The problem of determining the singularity expansion method (SEM) parameters from transient thin-wire data is examined. A computer code is used to generate response data. The SEM parameters are computed from these data. For noisy data, it is shown that the parameter values can be improved by averaging.     

Generation of transient response of nonlinear bipolar transistor circuits from device fabrication data

Dynamic models of double diffused bipolar transistors are generated from device fabrication data. The models consist of interconnections of two- and three-terminal resistors and capacitors whose characteristics are expressed in the form of tabulated values describing piecewise-linear surfaces. A circuit analysis program based on a piecewise-linear approach, simulates the time responses of circuits in which the transistors are imbedded. DC and small-signal AC analyses are also obtained. The computer program package thus yields overall circuit responses with fabrication data as input.     

The tapered antenna and its application to the junction problem for thin wires

When electrically thin conductors of different cross sectional size meet, the continuity of current is assured by Kirchhoff's current law. Additional conditions must be imposed on the derivatives of the currents or the charges per unit length. The nature of the required conditions is determined from an analysis of the tapered antenna.     

Large signal turn-on response of the junction transistors including nonlinear effects

The large-signal transient behavior of transistors must be considered as nonlinear phenomena. In this paper, the nonlinearity of the transient behavior of transistors in the active region are considered, and the charge control method is extended to include this nonlinearity. Using a one-dimensional homogeneous-base transistor model, the current variation of small-signal time constants in the charge control concept are analyzed in terms of emitter efficiency, surface recombination, and generated field in the base region. From the results of the small signal analysis, the large-signal time constants have been defined as a function of injection ratio. From the charge control equation founded on the large-signal time constants, the rise time is calculated including the current variations of time constants and voltage variation of junction capacitance. The results of the analysis are also verified by experimental measurements.     

A bibliography of transient effects in the resonant elastic response of matter to an intense light pulse

Selected phenomena associated with the interaction of coherent radiation (such as laser pulses) and matter are briefly described from a unified point of view. An extensive list of references is provided.     

Interimpurity light absorption in thin wires of III-V-type semiconductors

A study has been performed of interimpurity light absorption in weakly doped thin wires of III–V type semiconductors with Kane charge-carrier dispersion law with the one-dimensional random distribution of the impurities taken into account. The dependence of the absorption curve is analyzed: the location of the absorption maxima corresponding to transitions from the acceptor ground level to the ground level and first excited level of the donor as well as their edges and half-widths are found. It is shown that the nonparabolicity of the charge-carrier dispersion law leading to transitions between the impurity ground states causes an abrupt detachment of this absorption line from the remaining lines. Fiz. Tekh. Poluprovodn. 32, 108–110 (January 1998)     

Calculation of transient response

Given the rational algebraic function X(s) = an?1Sn?1+an?2Sn?2+?+a1s+a0/sn+bn?1sn?1+?+b1s+b0 it is shown that the corresponding time function is expressed simply by the linear combination x(t) = an?1qn?1(t)+an?2qn?2(t) +? +a1q1(t) + a0q0(t) where functions qt(t) are the last column elements of the transition matrix M(t) = exp (At).     

Analytical aspects of plane wave illuminated thin wires and slits

The paper deals with simple elementary approximations for the current and charge response on different straight wire structures, dipoles and short slits in the receiving case. After proof that transmission line equations are also valid for single wires without discontinuities, these equations are formulated including the incoming wave. They turn out have simple particular solutions that could be expected for the case, when the electric field is parallel to the wire, but holds true for the general case too. Satisfying the boundary condition at discontinuities (wire ends, lumped elements) gives rise to additional waves appearing as solutions of the homogeneous wave equation. The formulation of currents along and voltages across a slit, including an illuminating magnetic field at one side of the screen, leads again to transmission-line type equations and, consequently, to the inhomogeneous wave equation. As slits in screens are usually small in terms of wavelength, an approximative solution for the short slit will do. For this case, even closed-form expressions are possible for the magnetic near field     

Electromagnetic scattering from cylindrical arrays of infinitely long thin wires

Plane wave scattering by a cylindrical array of equally spaced infinitely long perfectly conducting thin wires is examined. The symmetry of the structure is exploited to derive a closed form expression for the currents excited on the wires, using the concept of circulant matrix and, alternatively, using a DFT (discrete Fourier transform) approach     

Quantitative analysis of effects causing nonlinear position response in position-sensitive photodetectors

Although it is theoretically possible to construct light-spot-position-sensitive photodetectors (PSD's) having perfect position-response linearity, in practice linearity is degraded by laterally inhomogeneous resistive layers, finite-conductive strips, and imperfect isolations. PSD's at 6 × 6 mm²having 0.5-percent nonlinearity have been fabricated, but before making larger PSD's with less nonlinearity, e.g., for use in silicon repeaters, a quantitative analysis of the causes of nonlinearity must be made. To this end, a computer model is developed. This model is described here, and the results of calculations performed with it are discussed. Nonlinearity caused by inhomogeneity is found to be less than 1/8 of the maximum relative change in resistive layer conductivity. It further appears that finite-conductive contact strips cause less than 0.05-percent nonlinearity if the contact strips are wide enough. Nonlinearity due to imperfect isolations is important only when n-n^-or p-p^-junctions are used. The calculations derived are found to be in good agreement with results given in the literature.     

On the transient response of emitter followers

Transient response of emitter followers is analyzed incorporating the effects of collector-base and load capacitances, gain-bandwidth product, excess delay, and base, collector, and load resistances. Basic considerations pertaining to transient response and instabilities are discussed, and numerical results are given for a wide range of circuit parameters.     

A unified theory of thin material wires [EM scattering]

The author presents an integral equation and method of moments (MM) solution to the problem of scattering by a thin material wire of circular cross section. In general the material wire has permittivity and permeability different from those of free space. The wire of radius a must be sufficiently thin so that k₀a ≪1, where k₀ is the free space wavenumber. However, there is no restriction on |k|a, where k is the wavenumber in the material wire. The method is referred to as unified in that it applies to thin material wires of arbitrary complex permittivity and permeability. Thus, a single or unified formulation applies to a low-density dielectric/ferrite wire or to a highly conducting metallic wire     

Simplified calculation of transient response

The transient response of a linear lumped-constant time-invariant network, which is excited by a driving force which has the ratio of two polynomials in the complex frequency p for its Laplace transform, can be tabulated easily using a simple linear difference equation. It is not necessary to know the location or multiplicity of the roots of the denominator, to expand in partial fractions, to use complex variables or contour integrals, or even to find the equation for the response. Any desired accuracy can be obtained easily. The new method uses simple algebra and real numbers only. It can be used to generate any mathematical function which has the ratio of two polynomials in p for its Laplace transform.