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The coexistence issue between ultra-wideband (UWB) radio communication systems and narrow-band wireless LAN systems is investigated by experiments and simulations. The work is divided in two parts. In this Part II, either impulse radio or multiband orthogonal frequency-division multiplex systems are assumed to be the disturbance source, while narrow-band wireless systems based on IEEE 802.11a/b are assumed to be the victims. The electromagnetic interference produced by a UWB disturbance source to the WiFi victim systems is experimentally evaluated by radiated measurements in a semianechoic chamber. Then, an innovative conducted coupling test is proposed to simplify the measurements while maintaining satisfactory accuracy. A simulation method is also proposed to help designers of wireless communication systems. The bit error ratio and packet error ratio are measured to evaluate the level of interference between different radio systems. Some tests are carried out for typical operational conditions of radio systems. Index Terms--Coexistence between wireless systems, conducted test, electromagnetic compatibility (EMC) measurements, interferences of digital radio systems, time-domain measurements, ultra-wideband (UWB) radio characterization.

The correct modeling and measurement of ultrawideband (UWB) radio signal are a critical issue to evaluate the electromagnetic (EM) emission of any communication system based on this technology. In this paper (Part I), UWB radio communication systems based on impulse radio (IR) and multiband orthogonal frequency division multiplex (MB-OFDM) technologies are characterized by simulations and experiments in both frequency and time domains. The EM characteristics of UWB radio are measured by different methods (conducted and radiative) and in different environments (anechoic and reverberation chambers). Index Terms--coexistence between wireless systems, electromagnetic compatibility (EMC) measurements, time-domain (TD) measurements, ultra-wideband (UWB) devices.

A numerical study is proposed to investigate the effects of different RF sources on the specific absorption rate (SAR) and maximum temperature increase in the human eye at different frequencies. In particular, a new model of the human head is presented and compared with an anatomical model of the visible human. The high resolution (0.5 mm) of the proposed model allows to consider more eye tissues than previous studies distinguishing the sclera from the retina and choroid. New values of blood perfusion and metabolic rate of these tissues are derived. A plane-wave field is considered as far-field exposure, while realistic models of mobile phone and dipole antennas are used as primary sources for near-field exposure. The obtained results show that the distributions of the SAR and temperature increase depend on the frequency, position, and kind of sources. Finally, attention is paid to the maximum temperature increase in the lens for the SAR values prescribed by the Commission on Non-Ionizing Radiation Protection. To this aim, a scaling approach is proposed, and significant values of temperature increase are found (about 0.3 [degrees]C for general public exposure and about 1.5 [degrees]C for occupational exposure) for the most critical cases of near-field exposures. Index Terms--Cellular phones, finite difference method, human exposure to electromagnetic fields (EMF), human eye modeling, numerical dosimetry, thermal simulation.

An experimental procedure to detect and localize defects in shielded cables is presented. First, time-domain measurements are carried out by injecting a short rise time pulse in the input section of the shielded cable. Then, the clean algorithm is applied to the measurement results to identify possible damages in the cable line. The localization of the cable section with defects is finally obtained in a very simple way due to the adopted method of measurement in time domain using a ultrawide-band pulser with a very fast rise time. The proposed method is validated by detecting and localizing known defects purposely introduced in test cables. Index Terms--Clean algorithm (CA), defect localization in cables, shielded cable, time-domain (TD) measurement, time-domain reflectometry (TDR), ultrawide-band (UWB) signal.

A numerical method is proposed to model transients in a shielded cable embedded in a three-dimensional field domain by using the finite-difference time-domain (FDTD) method. The coaxial shielded cable is assumed to be a multiconductor transmission line (MTL). The in cell voltage and the current on the external shield surface are calculated by a full-wave method, while the core current and the core-to-shield voltage are analyzed by assuming the validity of the quasi-TEM propagation mode inside the shield. The internal and external shield surfaces are coupled by the transfer admittance and by the transfer impedance of the cable shield. The solution is obtained by the FDTD method combining the MTL equations with the field equations. The proposed time-domain method takes into account the frequency-dependent parameters of the cable conductors by recursive convolution techniques. The validation of the procedure is performed in simple test configurations. Index Terms--Electromagnetic compatibility/interference (EMC/EMI), finite-difference time-domain (FDTD) method, multiconductor transmission lines (MTL), shielded cables.

An original finite-element approach is presented to calculate the capacitance matrix of a uniform multiconductor wire line. The examined two-dimensional (2-D) domain is discretized by nodal-based triangular elements where the Laplace equation is solved. A new procedure is developed to take into account the presence of the wires, which are assumed to be located in the vertex nodes of the FEM mesh. Through the proposed procedure, the physical dimensions of the wire cross sections are considered modifying the terms of the local stiffness matrix in the finite elements surrounding the wires. A further modification of the local FEM matrices allows to consider the logarithmic variation of the electrical potential around the wires. The procedure is efficient from a numerical point of view since it avoids the fine discretization of the nonconductive region surrounding the wire while achieving a good numerical accuracy. Numerical examples are given and compared with the analytical solutions for canonical configurations, including wires with dielectric cover. Index Terms - Electrostatics, FEM, MTL, per-unit-length parameters.

This paper describes a new procedure for the numerical computation of the electric field and current density distributions in a dc electrostatic precipitator in the presence of dust, taking into account the particle-size distribution. Poisson's and continuity equations are numerically solved by supposing that the coronating conductors satisfy Kaptzov's assumption on the emitter surfaces. Two iterative numerical procedures, both based on the finite element method (FEM), are implemented for evaluating, respectively, the unknown ionic charge density and the particle charge density distributions. The V-I characteristic and the precipitation efficiencies for the individual particle-size classes, calculated with reference to the pilot precipitator installed by ENEL (Italian Electricity Board) at its Marghera (Venice) coal-fired power station, are found to be very close to those measured experimentally.

Analytical solution of lossless field-excited multiconductor transmission lines is presented. The equivalent circuit of a multiconductor transmission line with distributed sources is reduced to a simple lumped parameter circuit with independent voltage sources at both the ends of the transmission line. The transient source waveforms are analytically estimated for exponential time dependence of the external field, as EMP, ESD, and lightning. The method is suitable for a direct implementation in computer-aided circuit analysis codes and enables a very fast analysis for any load condition. Some numerical results are presented for single conductor and multiconductor lines excited by an EMP plane-wave field.

Impedance network boundary conditions (INBC's) are implemented in the finite-difference time-domain (FDTD) method to analyze the electromagnetic field around penetrable shield structures. The shield region is eliminated from the computational domain and the INBC's are applied on the new boundary surfaces, i.e., shield surfaces, to take into account the field discontinuity produced by the shield. The INBC's represent an important extension of the well-known surface impedance boundary conditions (SIBC's) since the INBC's model accurately the coupling of the electromagnetic fields through penetrable shields and lead to a significant reduction of the number of the FDTD unknowns. The INBC expressions are given analytically in both frequency and time domains, and the INBC implementation in a FDTD code is discussed. The proposed INBC-FDTD method is numerically efficient because the resulting convolution integrals are recursively solved. Furthermore, approximate time-constant INBC's are proposed which are valid for many practical applications. The analysis of transient electromagnetic fields around penetrable conductive shields in simple test configurations are presented and compared with the analytical solutions. Index Terms--EMC, FDTD method, impedance network boundary conditions (INBC's), recursive convolution techniques, shielding, surface impedance boundary conditions (SIBC's).