1,721,126 research outputs found
On the use of irregular grids in the zeroth-order vector finite element - time domain (VFE-TD) method
No full textThis is an investigation regarding the use of zeroth-order vector finite elements. The mathematical formulation of the zeroth-order VFE-TD method is exposed to illustrate the solution of 2-D problems. In addition, a discussion about the optimum choice of different irregular trapezoidal and triangular grids is considered
Computer application of the EMC course at the University of Rome 'La Sapienza'
No full textSince 1990 an EMC course has been established for the Degree on Electrical Engineering at the University of Rome 'La Sapienza'. The EMC course is held during the fifth year and includes about 72 hours of lectures and 48 hours of computer applications and experimental test work. An overview of the computer applications developed during the EMC course at the University of Rome 'La Sapienza' is presented
FDTD modeling of impedance boundary conditions by equivalent LTI circuits
No full textA circuit-based implementation of the Leontovich impedance boundary condition (IBC) is proposed. The surface impedance of a lossy medium is approximated by a series of first-order rational functions using the vector-fitting technique. Thus, an equivalent analogical circuit with lumped linear time-invariant parameters is derived, which is simply analyzed in time domain without performing any convolution. The implementation of the equivalent circuit in the finite-difference time-domain method is detailed for different circuit configurations. Finally, the advantages of the proposed method are presented and compared with those of other numerical procedures for the solution of the IBC in time domain
Mitigation of the magnetic field generated by a wireless power transfer (WPT) system without reducing the WPT efficiency
No full textLocalization of UWB transmitters inside buildings and disaster rubble: A numerical investigation
No full textEMP-coupling to twisted-wire cables
No full textAn EMP (electromagnetic pulse) coupling to twisted-wire pair (TWP) cables above a ground reference plane is considered. The high-altitude EMP is represented by a plane wave. TWP cable is simulated in the frequency domain as a multiconductor uniform line excited by non-uniform electromagnetic fields. EMP-induced effects are computed by using an efficient matrix procedure based on the transmission line model (TLM). The transient waveforms for any terminal load conditions are obtained by an inverse discrete Fourier transformation. The theoretical procedure is applied for evaluating the EMP-induced effects on a TWP cable for different electric and geometric configurations. The results obtained by the procedure are compared with those computed for a parallel wire-line. The transient wire-to-ground voltages are very similar for TWP and parallel wire configurations. The wire-to-wire voltages and wire currents depend on the polarization and the incidence angles of the EMP plane-wave
EMP coupling to coaxial shielded cables
No full textA method for determining the effects induced within shielded cables by a high-altitude nuclear electromagnetic pulse (EMP), represented as a plane wave, is presented. The cable is regarded as a multiconductor line in which the EMP sources are impressed on the shield. An efficient matrix procedure permits simultaneous calculation of transient voltages and currents at any point on each conductor. This procedure, which is based on transmission-line theory, involves modal propagation and reflection matrix operators. The method of analysis permits fast calculation of voltage and current in the shield and inner conductor, whatever the terminal impedance may be. Comparison of the results obtained by applying the single and the multiconductor approaches reveals a few significant differences in the case of the braided-shield cables which become more important as lengths increase, as well as in given closing conditions
FD-TD analysis of nonuniform multiconductor lossy lines
No full textTransients in lossy multiconductor lines are analyzed by the Transmission Line Model (TLM) assuming a quasi-TEM propagation. Voltage and current waves propagation is described by integrodifferential equations with variable coefficients, where a convolution integral between the transient impedance and the time derivative of the current is used to model the skin effect in the conductors.The resulting equations system is solved by the Finite Difference-Time Domain (FD-TD) method. A new algorithm for the recursive calculation of the convolution integrals is proposed. Distributed nonuniformities, due to line parameters variation, and lumped nonuniformities, due to loads, junctions and discontinuities are considered
Induced fast transients in multiconductor shielded cables
No full textThe coupling of fast transient electromagnetic fields to lossy multiconductor shielded cables is considered. Calculation of the transient responses calls for the development of models simulating the cable, the incident field and the impressed sources. Accurate models are developed to simulate a multiconductor cable with a multilayer braided-shield and multiple parallel inner conductors or twisted-wire pairs. The incident field is the sum of the primary field, represented as a plane wave, and the wave reflected from the ground. The cable response is obtained in the frequency domain by means of an efficient matrix procedure, based on the transmission-line theory, which involves Thevenin-equivalent representation. The transient waveforms for any terminal load condition are computed by an inverse discrete Fourier transformation. The theoretical procedure is applied for evaluating transient voltages and currents induced by an EMP source on a bifilar twisted-wire line, with and without shield, above an aluminium or a ground plane
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