In this paper, a method for representing electromagnetic emissions from a printed circuit board (PCB) using an equivalent dipole model deduced from near-field scanning is proposed. The basic idea is to replace the PCB with a set of infinitesimal dipoles that generate the same radiated fields. Parameters of the equivalent dipoles are determined by directly fitting to the measured magnetic near fields. In closed-environment simulations, the equivalent method is extended to a dipole-dielectric conducting plane model to account for the interactions between the PCB and enclosure by including the basic physical features of the PCB. The electromagnetic emissions can then be predicted by solving the equivalent model with numerical methods, thereby, significantly reducing the simulation time and storage costs. A basic test board and a more complex practical telemetry PCB are modeled in different configurations and compared with measurements and full-field simulations, confirming the validity and efficiency of the model.

Modeling Electromagnetic Emissions From Printed Circuit Boards in Closed Environments Using Equivalent Dipoles

In this paper, an efficient method for the numerical simulation of near- and far-field propagation of stochastic electromagnetic (EM) fields is presented. The method is based on the transformation of field correlation dyadics using Green's functions or the field transfer functions computed for deterministic fields. The method accounts for arbitrary correlations between the noise radiation sources and allows to compute the spatial distribution of the spectral energy density of noisy electromagnetic sources. The introduced methodology can be combined with available electromagnetic modeling tools. It is shown that the method of moments can be applied to solve noisy electromagnetic field problems by network methods applying correlation matrix techniques. Examples demonstrating the strong influence of the correlation between the sources on the spatial distribution of the radiated noise field are presented.

Modeling of Noisy EM Field Propagation Using Correlation Information

This paper presents an automated procedure to determine the electric or magnetic near-field profile of electronic systems and devices in a given plane. It combines sequential sampling to determine the optimal coordinates of near-field scan points at arbitrary coordinates in the scanning plane. The effectiveness of the approach is illustrated by applying it to both a simulated and a measured printed circuit board example.

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Automated Near-Field Scanning Algorithm for the EMC Analysis of Electronic Devices

Electromagnetic interference (EMI) source reconstruction typically requires accurate measurements of both near-field magnitude and phase information. In some cases, an accurate phase measurement may not be practically feasible. A phase-retrieval method based on phaseless and single-plane near-field scanning is presented in this paper. By using an interpolation technique, the original data of field magnitude used for reconstruction can be divided into two groups: the sampling and interpolation groups. Subsequently, iteration algorithm together with the singular value decomposition method is employed to reconstruct the equivalent dipole model of the EMI source. Both numerical example and measurement example are given to verify the effectiveness of the proposed algorithm. The major advantage of the proposed method is that it can save a half scanning time and still produces a valid EMI source model. It also shows an ability to reduce some measurement errors.

An Iterative Approach for EMI Source Reconstruction Based on Phaseless and Single-Plane Near-Field Scanning

A new approach is proposed for modeling electromagnetic emissions of a printed circuit board (PCB) based on amplitude-only near-field measurement data. Magnetic dipoles placed over the top layer of the PCB are introduced as the equivalent of actual radiated sources. A restarted optimization procedure based on a differential evolution algorithm is developed to determine the parameters of the dipoles (number, position, and moment components) via minimizing the difference between the measured magnetic near field and that radiated by the dipoles. These equivalent dipoles can be used to predict the radiated emissions of the PCB once being determined. The proposed approach does not need the phase of the measured near fields, and its computational complexity is very low. Numerical results are presented to demonstrate the validity and efficiency of the proposed approach.

An Effective and Efficient Approach for Radiated Emission Prediction Based on Amplitude-Only Near-Field Measurements

A method for modeling electromagnetic emissions from printed circuits with equivalent dipole sources is presented. An optimization procedure based on the genetic algorithm is used to determine the number of equivalent dipoles and their parameters by fitting to the measured near fields. Prediction of emissions from the PCB can then be obtained by computing from the equivalent model without reference to the details of the PCB.

A genetic algorithm based method for modeling equivalent emission sources of printed circuits from near-field measurements

Since the publication of IEC 61000-4-20, the gigahertz transverse electromagnetic (GTEM) cell has gained popularity in radiated emission and immunity electromagnetic compatibility tests. Various numerical methods such as finite-difference time-domain, finite element method, and method of moments have been used to model the GTEM cell in the pursuit of getting to know the characteristic of the GTEM cell with varying degrees of verification. In this paper, the time-domain transmission line model will be used to model the GTEM cell. The advantages of this method include high accuracy and the ability to model different materials. Thus, the GTEM is realistically modeled including radio absorbing material (RAM) and lumped terminations. In addition, the model of a realistic device under test (DUT) was also included in the GTEM model. The DUT consists of a standard sized box with an aperture, placed in different orientations inside the GTEM for power and phase measurements. The particular features of this paper are: 1) the inclusion of a realistic numerical model of RAM, 2) the inclusion of a realistic DUT model, 3) systematic verification of the model against measurements, and 4) the method of phase measurement in a GTEM cell. Good agreement between the experimental results and simulations is obtained.

A Complete Model for Simulating Magnitude and Phase of Emissions from a DUT Placed Inside a GTEM Cell

A method for characterising and modelling the noisy electromagnetic fields from complex circuit boards using a simplified representation of correlated dipoles is investigated. It is shown how the equivalent dipole model can be constructed from the time domain measurements of the near fields. This equivalent model can then be used to accurately reproduce the emissions from the circuit board in both the near and far field. However, it is found that there are many challenges to such an approach as such a technique will require a large measurement data set to be acquired which may be very time consuming and the solution can be ill conditioned.

Characterisation of noisy electromagnetic fields from Circuits using the Correlation of equivalent sources

The positioning of electromagnetic (EM) sources on the complex plane, though a mathematical construct, is often applied in solving EM problems with directive confined (collimated) propagation characteristics. Equivalent dipole modeling, which finds its application in characterizing various current sources can be computationally expensive for large structures. Here, the complex localization of equivalent source points combined with the particle swarm optimization is used to improve the performance of the equivalent dipole modeling.

A. Nothofer

Papers

Modeling Electromagnetic Emissions From Printed Circuit Boards in Closed Environments Using Equivalent Dipoles

A genetic algorithm based method for modeling equivalent emission sources of printed circuits from near-field measurements

A Complete Model for Simulating Magnitude and Phase of Emissions from a DUT Placed Inside a GTEM Cell

Characterisation of noisy electromagnetic fields from Circuits using the Correlation of equivalent sources

Complex Locations of Equivalent Dipoles for Improved Characterization of Radiated Emissions