ETS-Lindgren 5411 GTEM! Test Cell - Manual (Page 9)

Introduction
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1.0 Introduction
The ETS-Lindgren Gigahertz Transverse Electromagnetic (GTEM!™) Cell is
a precision electromagnetic compatibility (EMC) test instrument primarily
intended for use as an EMC radiated immunity and radiated emissions test
facility. It is intended for installation in a corporate, laboratory, or industrial
environment, where its unique characteristics allow for the performance of fast
and efficient EMC radiated tests at a convenient location, without interference
from the ambient electromagnetic environment.
The GTEM! is a pyramidal tapered, dual-terminated section of 50-ohm
transmission line. The cell is flared to create a test volume within which the
Equipment Under Test (EUT) is placed. At the input, a normal 50-ohm coaxial
line is physically transformed to a rectangular cross section with an aspect ratio
of 3:2 horizontal to vertical. The center conductor, known as the septum, is a flat,
wide conductor which, when driven by a signal generator, produces a reasonably
sized region of a nominally uniform electric field distribution beneath it. This
region of nominally uniform field is the test volume for radiated immunity
(susceptibility) testing. By the theory of reciprocity, radiated emissions testing is
also conducted in the test volume. To increase the usable test volume, the
septum is located well above the horizontal centerline of the cross section, while
maintaining constant characteristic impedance and uniform field distribution. The
septum is terminated in a resistive array having a total value of 50 ohms for
matching the impedance of the source. Test volume fields, either applied to an
immunity test item or produced by the EUT during emissions testing, are
terminated in RF absorber. The shape of the test volume is a tapered wedge.
The fields generated by application of an RF voltage to the input of the
GTEM! propagate with a spherical wave front from the apex of the GTEM! to the
termination.
Standard Configuration
B
LANK
F
EED
-T
HROUGH
P
ANEL
A blank, 304-mm square, removable panel can be installed in the GTEM! wall to
accommodate additional cable entries. Separate blank removable panels are
available and are interchangeable.
I
NTERNAL
EUT M
ANIPULATOR
A multi-position EUT manipulator is available for the GTEM! to assist in locating
the EUT for radiated emissions testing.