Gigahertz Transverse Electromagnetic Research Articles

An Advanced Correlation Algorithm between GTEM and OATS for Radiated Emission Tests

This paper proposes an algorithm to improve the correlation between giga-hertz transverse electromagnetic (GTEM) cell and open area test site (OATS). It is based on the dipole modeling process of an unknown source object in a GTEM cell and on the evaluation of the approximate far field equations correlated with measured GTEM powers at output port of the GTEM cell. In this algorithm, the relative phase differences between dipole moments play an important part in modeling the test object as a set of dipoles and offer stable calculation of emission values. The radiated emission test using this algorithm requires fifteen orientations of equipment under test, but the increased orientations as compared with the previous method have little effect on the time needed for testing. Radiation from a notebook computer has been tested for statistical analysis of the correlation between GTEM data and OATS data. The emission test results of the notebook computer show that the mean, the standard deviation, and the correlation coefficient are −0.62, 1.99, and +0.85, respectively. These figures indicate that this algorithm provides improved accuracy in the measurement of electromagnetic emissions over the previous method.

FDTD evaluation of scattering by metallic objects in GTEM cells

The finite difference time domain (FDTD) technique, developed in a polar coordinate system, is used to analyse the scattering by metallic objects in a gigahertz transverse electromagnetic (GTEM) cell. The advantage of using the FDTD method is the noticeable mathematical simplification, with respect to the analytical approach, which allows one to treat general structures and electrical characteristics without further analytical effort, and use of computer resources. The analysis has been carried out both at discrete frequencies, to compare our results with those in the literature, and with pulse sources to extract, by means of a discrete Fourier transform, the frequency domain behaviour of the system. The measurements inside the GTEM cell show a good correlation with those made in anechoic chambers.