Angela Nothofer

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

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.

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

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 genetic algorithm based method for modeling equivalent emission sources of printed circuits from 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.

Complex Locations of Equivalent Dipoles for Improved Characterization of Radiated Emissions

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.

Measurement and simulation of near field emissions from microstrip lines

This paper presents results from measurements and simulations of near field scans above a microstrip line on a FR4 dielectric substrate. It is found that, through careful probe calibration, good agreement between measurement and simulation can be obtained up to 1 GHz. Above 1 GHz differences appear some due to physical features that are poorly quantified, particularly the dielectric loss associated with the FR4 substrate.

Modeling of electromagnetic emissions from a multilayer PCB

In this paper, the electromagnetic (EM) field from a multilayer PCB is characterized using an equivalent dipole model. Here, the moments for the dipoles are computed from the EM information extracted in the near field of the PCB. These dipoles are modeled together with their images over a finite ground plane. In addition, passive dipoles were included to emulate the effects of the induced currents at edges leading to diffraction.

Radiated emissions and experimental precautions of equipment with cables in GTEM cells

Any electric or electronic equipment sold within the European Union has to comply with the EC Directive on Electromagnetic Compatibility (EMC). To achieve compliance, the equipment must be tested for radiated/conducted emissions and immunity. A wide range of national and international testing methods and standards are in force such as the IEC 61000–40–20 [1]. However, standards in general lack of describing testing methods for equipment with cables. Since most devices and systems contain leads and cables; the current standards cannot be directly employed. In an effort to approach this crucial matter, we present the outcomes of measurements conducted on an EUT (metal box) with different cable bundle configurations, in conjunction with both, the correlation algorithm given in the standards and the repeatability concerns between different GTEM cells.

Optimisation of a simple equivalent dipole model to include edge effects

An approach that offers a simplified approximation for electromagnetic field (EM) emissions as a result of the finiteness of an EM scatterer is discussed. The scattering effects of a finite perfect electric conductor (PEC) which comprises reflection and diffraction are computed using the equivalent dipole model. The optimum placement of the equivalent dipoles is evaluated and shown that the solution is valid over a large frequency range or for time domain simulations.

Conducted emission analysis of electric nacelle anti ice system in aircraft

This paper describes the high frequency behaviour of an Electric Nacelle Anti Ice system (ENAI). In the high frequency range above 150kHz, conducted emissions have to be considered. A silicon-controlled rectifier (SCR) is the main source for conducted emissions. Simulation and measurements are implemented on the ENAI system for comparison and verification. Simulations were verified by measurements and were shown to be a good alternative to measurements to provide quick and reliable predictions, whilst interference in the measurement environment can cause errors.

Effects of phase differences in GTEM cell measurements

This paper presents the effect on radiated power measured at the GTEM output port if the phase between the radiating dipole moments of the EUT is altered in steps from -180 degree to +170 degree. In current practice it is often assumed that the phase difference between dipole moments does not change the power measured at the GTEM output port. The results from this work disprove this assumption. Results from experiments show a significant change in the measured power when the phase was altered. Simulations using time-domain transmission line method (TLM) performed using the procedures described in standards MIMIC the experimental results and the variation of power magnitude agrees with that of experiments. SuperNECTM was used to produce radiation patterns for different phases which are used to gain an insight into the impact of phase. The major outcomes of this work are (1) an insight into an assessment of the impact of phase on power measurement and (2) the expected errors and uncertainties due to phase differences when current procedures are applied.