In this paper, a simple method to obtain the equivalent radiation emitting sources of an electronic circuit using the near-field scanning method is presented. The model is based on a set of elemental dipoles that substitutes the electronic circuit and radiates the same magnetic field. Two different approaches are presented: a set of electric dipoles and a set of magnetic dipoles. In order to build the model, both the magnitude and phase of the magnetic field are required. These measurements are carried out using the "near-field scanning method," and two procedures are presented: using the vector network analyzer and the spectrum analyzer. Finally, the model is applied to two different cases: to obtain the radiated near-field of a component (microcontroller) and to obtain the field of a complete electronic board.

Modeling Magnetic Radiations of Electronic Circuits Using Near-Field Scanning Method

A completely automatic near-field mapping system has been developed within the Research Institute for Electronic Embedded Systems (IRSEEM) in order to determine the electromagnetic field created by electronic systems and components. This test bench uses a 3-D positioning system of the probe to make accurate measurements. This paper presents some applications of the near-field techniques in EMC investigations. In the first part, near-field measurements are used to locate precisely the electromagnetic sources of a limiter device. In the second part, we present an equivalent model of the radiated emission of an integrated circuit. In the last part, the near-field test bench is used to characterize faults in a cable.

Applications of the Near-Field Techniques in EMC Investigations

In this paper, an improved dipole-moment model for characterizing near-field coupling and far-field radiation from an IC based on near-field scanning is proposed. An array of electric and magnetic dipole moments is used to reproduce the field distributions in a scanning plane above an IC. These dipole moments can then be used as noise sources for the IC. In order to ensure the accurate prediction of the near-field coupling from the IC, the regularization technique and the truncated singular-value decomposition method are investigated in this paper, together with the conventional least-squares method, to reconstruct the dipole moments from the near-field scanning data. A simple example is used to demonstrate the approach. The improved dipole-moment model is particularly useful for addressing radio-frequency interference issues where near-field noise coupling needs to be accurately analyzed.

https://scholarsmine.mst.edu/cgi/viewcontent.cgi?article=3074&context=doctoral_dissertations

An Improved Dipole-Moment Model Based on Near-Field Scanning for Characterizing Near-Field Coupling and Far-Field Radiation From an IC

A procedure is developed to predict electromagnetic interference from electronic products using near-field scan data. Measured near-field data are used to define equivalent electric and magnetic current sources characterizing the electromagnetic emissions from an electronic circuit. Reconciliation of the equivalent sources is performed to allow the sources to be accurately applied within full-wave numerical modeling tools like finite-difference time domain (FDTD). Results show that the radiated fields must typically be represented by both electric and magnetic current sources if scattering and multiple-reflections from nearby objects are to be taken into account. The accuracy of the approach is demonstrated by predicting the fields generated by a microstrip trace within and outside of a slotted enclosure, and by predicting the fields generated by the microstrip trace close to a long wire. Values predicted from near-field scan data match those from full-wave simulations or measurements within 6 dB.

Prediction of Radiated Emissions Using Near-Field Measurements

As the first part of a study that aims to propose tools to take into account some electromagnetic compatibility aspects, we have developed a model to predict the electric and magnetic fields emitted by a device. This model is based on a set of equivalent sources (electric and magnetic dipoles) obtained from the cartographies of the tangential components of electric and magnetic near fields. One of its features is to be suitable for a commercial electromagnetic simulation tool based on a finite element method. This paper presents the process of modeling and the measurement and calibration procedure to obtain electromagnetic fields necessary for the model; the validation and the integration of the model into a commercial electromagnetic simulator are then performed on a Wilkinson power divider.

Simple Electromagnetic Modeling Procedure: From Near-Field Measurements to Commercial Electromagnetic Simulation Tool

Near-field scanning has often been used to measure and characterize magnetic fields surrounding individual integrated circuits (IC) and high speed digital electronic circuits. The paper describes the use of near-field scanning data, performed in a typical laboratory bench top environment, to predict radiated electromagnetic interference (EMI) in a typical product environment. The product environment may include enclosures and apertures. The approach begins by acquiring sufficient near-field scanning data to allow representation of an unintentional radiating source by an equivalent surface current distribution. The equivalent current distribution is used as a source in numerical full wave modeling. The agreement between direct full wave simulation results and full wave simulation results using equivalent sources works well under certain assumptions.

/pdf/using-near-field-scanning-to-predict-radiated-fields-1mev2f07nc.pdf

Using near-field scanning to predict radiated fields

The finite-difference time-domain (FDTD) method is a robust technique for calculating electromagnetic fields, but practical problems, involving complex or large geometries, can require a long time to calculate on any one single-processor computer. One computer with many processors or many single-processor computers can reduce the computation time. However, some FDTD cell types, e.g., PML cells, require more computation time than others. Thus, the size and shape of the individual process allocations can significantly influence the computation time. This paper addresses these load balancing issues with static and quasi-dynamic approaches. The message-passing interface (MPI) library is applied to a three-dimensional (3D) FDTD code. Timing results including speedup and efficiency, are presented for trials run on a cluster of sixteen processing nodes and one server node. Two examples are shown in this paper, a power bus with 16 decoupling capacitors and a five layer power distribution network. In such models, the problem size and complexity make modeling with a serial code impractical and time consuming for engineering. Models with several million cells take days to run, but proper implementation, including load balancing, can reduce this execution time to hours on a sufficiently powerful cluster.

/pdf/static-and-quasi-dynamic-load-balancing-in-parallel-fdtd-fgdm5o7sm4.pdf

Static and quasi-dynamic load balancing in parallel FDTD codes for signal integrity, power integrity, and packaging applications

The calculation of crosstalk on printed circuit boards (PCBs) can be critical to board design. Where coupling occurs between parallel sections, transmission line theory is sufficient. However, if the dominant sections are not parallel, a full-wave method, like PEEC can be used. In this paper a dynamic Green's function is utilized for the PEEC coefficient calculations. This paper includes a discussion of how analytic expressions for quasi-static PEEC calculations can be reused in the dynamic Green's function calculations, removing the need to derive new integration formulas. In addition, a subgridding approach is utilized to increase the integration accuracy.

Crosstalk analysis for nonparallel transmission lines using PEEC with a dynamic Green's function formulation

In electromagnetic modeling, agreement between modeling and measurements is a common goal. There are questions that define every model. What is to be modeled? How is it going to be modeled? At what scale is it to be modeled? Through sample results and discussion, this paper addresses some general and some specific elements of model veracity. Through determination, numerical models can certainly be pushed to match any measured results. However, in the end the question that this paper addresses is not necessarily "How good can this model be?" as it is "Is this model good enough?".

M.A. Cracraft

Papers

Using near-field scanning to predict radiated fields

Static and quasi-dynamic load balancing in parallel FDTD codes for signal integrity, power integrity, and packaging applications

Crosstalk analysis for nonparallel transmission lines using PEEC with a dynamic Green's function formulation

Modeling issues for full-wave numerical EMI simulation