Since the distance from the ground to the septum of a mTEM cell is electrically
short, the mTEM field can be described using the cavity model of
Chapter 4. A scan, performed above the IC, very close to the
surface of the IC, enables the extraction of the excitation currents. The source currents
with the coupling factors, together with the cavity model, enable the simulation of the
mTEM cell measurement result.
A mTEM cell measurement requires the production of a test board. With the prediction
of the mTEM cell measurement results from field scan data, this costly test board is
not necessary, because the scan measurement can be performed on an application board.
There will be some deviations to the mTEM cell measurement with a test board, because
the currents on the IC also depend on the external PCB layout and there will be
differences between the test and the application board. However, this is not a drawback,
but an advantage, because the simulation based on the application board near field
measurement will provide an even better view into the cavity coupling of the intended
application.
C. Poschalko: The Simulation of Emission from Printed Circuit Boards under a Metallic Cover
