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The modeling of electrical characteristics of connections is an important stage of the design phase of a structure. Indeed, they have an impact on the current density distributions inside conductors as well as on the current distributions when several components are connected in parallel. In the case of a return plane in the studied structure as for power electronics converters or railway applications, the model of connections has to be improved in order to represent the physics better. For the first application field, the cooling system itself can be a ground plane, and for the second one, the earth has to be modeled. This paper presents different ways to take into account a return plane while modeling the electrical equivalent circuit of connections above it. It starts with the simplest one, the image method, and continues with the use of a complex skin depth result of solving the Carson integral. Index Terms--Electromagnetic interference (EMI) modeling, equivalent impedance, finite-element method (FEM), partial-element equivalent circuit (PEEC) method, railway system, transmission line modeling.

A systematic procedure to determine the parameters of a previously proposed low- to high-frequency induction motor model is presented. An analysis of the high-frequency behavior with regard to the impact of magnetic core selection, parasitic interturn and winding-to-frame capacitors, and skin effects of windings is investigated in greater detail for the proposed universal model of an induction motor. The model is universal in the sense that it is derived by extending the low-frequency standard T-equivalent circuit (IEEE Standard 112) to include high-frequency effects under both common- and differential-mode domains and can be used for transient reflected-wave studies and electromagnetic interference emissions in motor drive systems. A test-based method and an analytical approach, which are useful in application and design stages, respectively, are presented to determine the frequency characteristics of the induction motor. Findings of the investigation were verified experimentally with results presented in this paper. Index Terms--Electromagnetic interference (EMI), high-frequency model, induction motor, reflected wave, transient overvoltage.

This paper presents an accurate analysis of the effects produced by electrostatic discharge (ESD) inside a metallic enclosure, representing the metallic shield of an apparatus. The considered discharges are either directly generated inside the cavity or guided into the enclosure through a transmission line. The model, which makes use of a modal approach for the calculation of the electromagnetic (EM) field inside the cavity, evaluates the disturbance induced by the different kinds of ESDs on a victim line. The results both in the frequency and time domain have been validated by experimental measurements and highlight the effects of the resonant nature of the structure on the intensity and the duration of the disturbance. Index Terms--Electrostatic discharge (ESD), resonant structures.

A blind adaptive algorithm dubbed BA-FRESH (frequency shift) filtering is proposed. The proposed algorithm utilizes signal cyclostationarity to derive the desired signal from spectrally overlapping interference. Simulation results show that the BA-FRESH filter can separate desired signals from spectrally overlapping interference by determining only the cycle frequencies of the signals. In addition, the filter converges to the same optimum value as the least-mean-square-FRESH filter but is superior in the sense that it does not require knowledge of the statistics of the signal as well as a copy of the signal.

This paper presents upper bounds on the bit-error rate (BER) of optimum combining in wireless systems with multiple cochannel interferers in a Rayleigh fading environment. We present closed-form expressions for the upper bound on the bit-error rate with optimum combining, for any number of antennas and interferers, with coherent detection of BPSK and QAM signals, and differential detection of DPSK. We also present bounds on the performance gain of optimum combining over maximal ratio combining. These bounds are asymptotically tight with decreasing BER, and results show that the asymptotic gain is within 2 dB of the gain as determined by computer simulation for a variety of cases at [10.sup.-3] BER. The closed-form expressions for the bound permit rapid calculation of the improvement with optimum combining for any number of interferers and antennas, as compared with the CPU hours previously required by Monte Carlo simulation. Thus these bounds allow calculation of the performance of optimum combining under a variety of conditions where it was not possible previously, including analysis of the outage probability with shadow fading and the combined effect of adaptive arrays and dynamic channel assignment in mobile radio systems. Index Terms - Bit-error rate, optimum combining, Rayleigh fading, smart antennas.

This paper considers the use of spatio-temporal adaptive array processing in over-the-horizon radar (OTHR) and airborne radar applications in order to remove nonstationary multipath interference, known as 'hot clutter.' Since the spatio-temporal properties of hot clutter cannot be assumed constant over the coherent processing interval (CPI), conventional adaptive techniques fail to provide effective hot-clutter mitigation without simultaneously degrading the properties of the backscattered radar signals, known as 'cold clutter.' The approach presented incorporates multiple 'stochastic' (data-dependent) constraints to achieve effective hot-clutter suppression, while maintaining distortionless output cold-clutter post-processing stationarity.

A new method was developed for the modeling and time-domain simulation of transmission line systems exposed to external fields. The approach was tested by applying it to various line systems with different external fields. Results showed that the approach can accurately model the effect of external fields and is robust enough to be compatible with almost any line model and circuit simulator.

In this paper, a novel approach for the implementation of scattering theory is proposed in order to evaluate the electromagnetic effects of lightning return stroke on complex wire structures. An electric field integral equation (EFIE) in time domain is employed to describe the electromagnetic transients from lightning. The proposed approach is applied to single-phase three-phase as well as Y-shaped transmission line located above a perfectly conducting ground. The simulation results reproduce accurately experimental data available in the literature. The proposed method provides new possibilities in estimation of lightning indirect effects on complex networks as an example 'radial transmission systems tapped from main switching substations' are investigated. Index Terms - Coupling, EFIE, LEMP, lightning, MoM.

RF noise immunity is becoming a serious problem for integrated circuits (IC's). We have found a frequency-domain simulator [harmonic balance (HB)] to be useful for analyzing the undesired IC behavior, especially the dc output shift under the large RF injection. The simulator has the following advantages in comparison with a conventional time-domain simulator such as SPICE: 1) dc output shifts can be simulated in a very short time using a conventional bipolar transistor model and 2) steady-state current or voltage waveforms at each node in an IC are directly and easily obtained. This paper describes the methods and results of the dc shifts analysis of a bipolar transistor or a differential amplifier using the HB simulator. Index Terms - Bipolar transistor, dc shift, differential amplifier, frequency-domain analysis, harmonic balance, injection, RF, simulation, undesired behavior.

A quasi-static approach for evaluating inductive and capacitive coupling and radiated noise in the standard electromagnetic compatibility (EMC) measurement conditions has been developed. Multilayer structures are analyzed considering a quasi-static Green's function formulation. Variational approaches have been followed to compute inductive and capacitive parasitics. Electric and magnetic multipolar expansions are used for a fast computation of near- and far-field radiated noise in a large broad band. The approach has been validated considering different cases ranging from simple circuits to realistic switched-mode power supplies and some of the validation cases are presented. The main advantages of this method is the short central processing unit (CPU) time it requires to provide reliable results for EMC analysis and design purposes. Index Terms - Circuit modeling, parasitics, quasi-static approach, radiated fields.

This brief is concerned with the two-dimensional (2-D) digital notch filter design problem. First, the outer product expansion is used to reduce the 2-D notch filter design problem to two pairs of one-dimensional (1-D) filter design problems. Then, we develop a simple algebraic method for the design of two pairs of 1-D IIR filter design. This approach not only has closed form transfer function but also satisfies bounded input/output (BIBO) stability condition. Finally, one example is included to illustrate the proposed design method, and the 2-D IIR notch filter is applied to eliminate the sinusoidal interference superimposed on an image. Index Terms - 2-D IIR notch filter, interference removal.

The recently developed Locally Optimum Bayes Detection (LOBD) framework for nonadditive non-Gaussian noise is applied to a particular additive and signal-dependent noise model where the noise components are correlated. Under the proposed observation model, performance of the LOB detectors is compared with that of well-known conventional receivers.

This paper presents a numerical modeling method developed for evaluating electromagnetic (EM) interference on the equipment inside a telecommunication exchange caused by a direct lightning stroke to a telecommunication tower close (i.e., a few meters) to the exchange building. Considering two different bonding configurations, EM interference is evaluated by calculating the electrical parameters: the EM fields, voltages, and currents. A special Method of Moment (MOM) wire-grid procedure using 'dipole' and 'loop' type basis and test functions was used as a numerical tool. A simple model was also developed for simulating the equipment mechanical structures which modify the field distribution inside the building. The voltages and currents induced on shielded cables were evaluated by means of a mixed technique, where the MOM procedure is combined with a SPICE analysis. Numerical modeling was used for two different situations: to simulate some experimental tests carried out in the field, where a 1.6 kA lightning current of a pulse generator was injected on the top of the 25 m high telecommunication tower close to a small exchange building; and to calculate the same parameters when a real lightning current strikes the telecommunication tower.

This paper deals with a numerical modelling of the interferences produced by electrostatic discharges that reach the surface of metallic boxes containing electronic circuits and flow toward the ground connections. The wave-form of the interfering current assumed is taken from the draft of the CENELEC ESD Standard. The distribution of the current density into the enclosure during the electrostatic discharge event is deduced by means of a scalar magnetic potential approach in the frequency domain, and by a consequent finite difference discretization. The passages from the frequency domain to the time domain and forward are made using the discrete Fourier transform. This formulation of the problem allows the simulation grid to be reduced to only the metallic enclosure, saving time either in preparation of the input data or in the numerical computation. The electromagnetic interferences radiated by the enclosure during the electrostatic discharge event are directly computed by multipole expansion of the resulting current density distribution.

This paper deals with an EMC analysis of a power converter. In particular, the phenomena and modeling of conducted noise emission caused by an SCR are described. Theoretical results in the time as well as frequency domain are discussed and compared to the time signal measured and its spectrum.

Target 'glint' (the difference between the phase-front gradient of the scattered field and the true target direction vector) is related to the analytic properties of the scattered field. The resulting model is used to reinterpret diversity methods for glint reduction and to more accurately specify system requirements. A relationship for estimating the best possible improvement in target bearing estimation is also developed.

Use of the general unsteady vortex-lattice method in an X-29 -like flowfield to model unsteady and steady aerodynamic interference reveals that simulation of the wakes of the upstream components is essential as the canard wakes negatively affect the lift from main wing. The vorticity shed effects attain maximum intensity when the shed vorticity convects across the main wing. The unsteady vortex-lattice method also helps model the interference effect and is feasible for modeling flowfields only when vortex bursting does not develop and lines of separation are distinct.

The increasing size of modern electricity supply systems, as well as the higher operating and short-circuit currents of the high voltage systems have been matched by an over-spreading network of earth return circuits (pipelines, cables, etc.) close to high-voltage installations, resulting in a closer inductive and, in the vicinity of earth electrodes, conductive coupling of both system types. The view of the acceptance or inadmissibility of these interferences resulting from the couplings requires the quantification of the physical effects. A computer-simulation leads to reliable forecasts with respect to system stresses and suitable countermeasures. A universally valid algorithm for the calculation of interference voltages and currents in networks of optional topology or with several exposures to power lines is presented and applied to practical problem cases. The algorithm developed is superior to existing models as it simulates uniformly both the inductive and the conductive effects on earth return circuits.

This article addresses the computer modeling and simulation of EMC problems of complex structures, using the NEC and ESP moment method codes. The rules and guidelines of modeling using the two codes are summarized. In addition, visualization and automation of the modeling process are made possible through an interface computer program GEOM developed at Arizona State University. Finally, the interference between two wire antennas mounted on a complex helicopter model is given as an example of using these codes in EMC applications.

The knowledge of the magnitude and of the spatial and temporal distributions of electric and magnetic fields radiated during the ignition of the plasma armature of arc-driven railguns, can be a useful tool for the correct design of the shielding and of the location of electronic apparatuses controlling the launchers. In this paper the electromagnetic fields radiated by a railgun during its operation are evaluated at different points around the launcher, The radiation is determined, assuming a temporal and spatial form of the current in the plasma arc, and integrating Maxwell equations directly in the time domain. In general the evaluation of the obtained electromagnetic fields expressions requires a numerical integration, while when it is possible to assume particular spatial and temporal form of the arc current, analytical expressions have been derived.

Three variations of the usual two-slit electron diffraction experiment--insertion of a solenoid, of a rotating superconductor, and of an electric line charge in a neutron diffraction experiment--are examined. Each is shown to lead to a shift in the interference pattern.

The effect the Earth magnetic field has on the electron beams present inside cathode ray tubes (CRTs) becomes more evident for larger tubes dominant in the high-definition television (HDTV) and computer displays. Consequently, the quality of an image formed on the screen deteriorates what can be visually perceived as the image distortion and degradation of the color purity. In this paper, we describe a computer suite developed for the design and numerical modeling of inner magnetic shielding assemblies employed to minimize this negative field-beam interaction for trinitron type tubes. Till now such assemblies were mostly designed by an expensive experimentation based on the 'cut and try' approach. By applying the 3-d finite element method, the actual magnetic characteristics of assembly parts formed magnetically by degaussing, the grille anisotropy and the frame bulkiness can be considered. Also, a set of design tools developed to evaluate the assembly shielding performance is described.

Non-linear distortion in the form of partial erasure is a primary impediment at high magnetic recording densities. This paper simplifies a decision-feedback tree-search receiver for combating partial erasure. Utilizing an internal flag and a pre-computed threshold lookup table, the proposed receiver requires no multiplications for its metric computation.

This paper develops a method to calculate the effects of sensitivity time control (STC) on interference, experienced by one radar, caused by another radar. The probability density function (PDF) of STC attenuation is determined by, and is related to the overall probability distribution that determines the probability of interference. This method is consistent with, and complementary to the method of calculating the effects of antenna-to-antenna coupling between the radars.

Partial-response (PR) signaling is used to model communications channels with intersymbol interference (ISI) such as the magnetic-recording channel and the copper-wire channel for digital subscriber lines. Coding for improving noise immunity in higher order partial-response channels, such as the "extended" class-4 channels denoted EPR4, [E.sup.2]PR4, [E.sup.3]PR4, has become an important subject as the linear densities in magnetic recording approach those at which these partial-response channels are the best models of real channels. In this paper, we consider partial-response channels for which ISI is so severe that the channels fail to achieve the matched-filter bound (MFB) for symbol error rate, assuming maximum-likelihood decoding. We show that their performance can be improved to the MFB by high-rate codes based on constrained systems, some of which may even simplify the Viterbi detectors relative to the uncoded channels. We present several examples of high-rate constrained codes for [E.sup.2]PR4 and [E.sup.3]PR4 channels and evaluate their performance by simulation. Index Terms - Constrained coding, magnetic recording, partial response.

This paper presents a general methodology for performance characterization of digital transmission systems in the presence of cochannel interference, as a function of the actual number of interferers (ranging from zero to infinity). Bit error probability in time-invariant channels and outage probability in time-varying quasi-stationary channels are discussed. More precisely, a general approach to an outage probability definition based on the concept of outage domain is introduced. This allows the discussion of the relation to the other definitions which have appeared in the literature and the proposal of some new more accurate methods for the evaluation of outage probability. A suitable comparison between exact evaluation, the well-known Gaussian approximation, and the other new approaches proposed in this paper, is carried out. To evaluate performance, bit error probability is suitably obtained for linearly modulated signals by adopting a semianalytical approach, and for nonlinear (e.g., continuous phase) modulation signals, by means of simulation. Finally, as an example, the different approaches to derive performance discussed in the paper have been applied to a linear microcellular scenario. Index Terms - Cochannel interference, digital communications, fading channels, mobile communications, wireless communications.

The performance of a minimum-noise-variance beamformer that utilizes a single electromagnetic vector sensor was investigated. The sensor is capable of measuring the complete electric and magnetic fields induced by electromagnetic signals at one point. Experimental results showed that the state of polarization of the interference under investigation ranges from completely polarized to unpolarized. Explicit expressions for the signal-to-interference-plus-noise ratio were obtained in terms of the parameters of interference, signal and noise.

We study the system capacity of cellular systems with time-division multiple access, slow time-frequency hopping (F-TDMA), and conventional single-user processing at the receivers. System capacity is formally defined as the maximum of the product of the number of users per cell times the user spectral efficiency for a given maximum outage probability. We adopt an information-theoretic definition of outage as the event that the mutual information of the block-interference channel resulting from a finite number of signal bursts spanned by the transmission of a user code word falls below the actual code rate, because of fading, shadowing, and interference. Starting from this definition, we develop a general framework which naturally takes into account many different aspects of F-TDMA cellular systems like channel reuse, channel utilization, waveform design, time-frequency hopping, voice activity exploitation, handoff, and power control strategies. Most importantly, our analysis does not rely on the choice of a particular coding scheme and can be applied to a very large class of systems in order to find guidelines for capacity-maximizing system design. A numerical example based on a typical urban mobile environment shows that there is a considerable capacity gap between actual F-TDMA systems and the limits predicted by our analysis. However, this gap can be filled by carefully designed "practical" systems, which make use of conventional single-user processing and simple coded modulation schemes. Index Terms - Block-interference and block-fading channels, cellular systems, information outage probability.

This paper deals with probabilistic modeling of the electromagnetic (EM) response of cables inside a complex cavity subjected to well overmoded EM penetration. Theoretical studies indicate that the field amplitudes and cable currents squared both should have a [Chi]-square distribution with two degrees of freedom, but our observations indicate that a log normal fit is empirically better unless the data, if experimentally obtained, is first passed through a carefully tailored trend-removing filter. If a cable model is driven by statistically simulated enclosure fields, similar extreme care must be taken with the numerical generation of these driving fields. The major innovation reported here is the development of an algorithm that models cable-drive fields simultaneously having a [Chi]-square power-flux distribution and the physically mandated local autocorrelation at a spatial point as frequency is swept or at a fixed frequency as the power flux sensor is moved around to map the cavity response. Nature is quite adept at creating a cable drive with these simultaneous attributes, but computer emulation had proved very exasperating. Our algorithm, as an unplanned bonus, also has the capability to transform random numbers from one distribution to another. For instance, one can input normally distributed power-flux values and obtain as the output [Chi] square or log normally distributed power-flux values. The reverse transformations are also allowed. Index Terms - Aperture leakage, cable coupling, [Chi]-square distribution, electric field, electromagnetic interference, electronic mode stirring, log-normal distribution, mode-stirred chambers, statistical electromagnetics.