Characterization of electric field distribution in a GTEM cell
Two of the most important measurements related to electromagnetic compatibility (EMC) are radiated emission and radiated immunity. These measurements must be performed in a facility which provides reliability and reproducibility. The Gigahertz Transverse Electromagnetic Mode (GTEM) cell is one...
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Format: | Thesis |
Language: | English English English |
Published: |
2004
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Online Access: | http://eprints.uthm.edu.my/7606/1/24p%20AIZAN%20UBIN.pdf http://eprints.uthm.edu.my/7606/2/AIZAN%20UBIN%20COPYRIGHT%20DECLARATION.pdf http://eprints.uthm.edu.my/7606/3/AIZAN%20UBIN%20WATERMARK.pdf |
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Summary: | Two of the most important measurements related to electromagnetic
compatibility (EMC) are radiated emission and radiated immunity. These measurements
must be performed in a facility which provides reliability and reproducibility. The
Gigahertz Transverse Electromagnetic Mode (GTEM) cell is one of the facilities for
EMC measurement due to its well defined electric and magnetic field distribution in
addition to being cost effective. The research undertaken in this project is to determine
the field distribution in the GTEM by using Finite Difference Time Domain (FDTD).
The results from the modeling are then compared with actual measurements and any
differences will be noted and explained. The field strength inside a GTEM cell is a
fl.lI1ction of the input power as well as location along the longitudinal axis or septum
height. Radiated immunity measurements require field uniformity (+6 dB according to
IEC 61000-4-3 standard) which depends on the design aspects of the GTEM such as
size, material and absorbing condition. The capability of the GTEM cell to provide the
unifo1111 field can be tested theoretically and experimentally. FDTD is a numerical
method that can be used to predict the electric field distribution in a GTEM cell. The
electric field distribution for frequencies at 100 MHz, 200 MHz, and 400 MHz were
calculated using the EZ-FDTD software. In this report, theoretical study on the field
strength and distribution in a GTEM cell is described. It is followed by making
measurements of the field based on the radiated immunity test setup. It is found that at
septum height 63 cm for frequency 100 MHz, the measured and simulated results are
very close. This is the location recommended by the manufacturer for the placement of
equipment under test (EUT) in radiated emission and radiated immunity test. The
difference varies from 0.01 dB to 4.91 dB. The difference between modeling and actual
measurement can be attributed to the input field distribution, inhomogeneous
characteristics of the septum and existence of standing wave. In the future, it is
recommended that other numerical methods such as Finite Element Method (FEM) and
Transmission Lines Method (TLM) be used and more accurate model and absorbing
boundary condition parameters be implemented. |
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