An emission simulation of a device has also to consider ICs and active components. This
requires IC emission models which can be efficiently integrated into the emission
modeling technique of the device. The evolution of IC standard modeling methods for RF
emission in Table 2.2 was presented by [3] in
May 2008.

According to Table 2.2, there are currently no IC standard
modeling methods available for the frequency range above 3GHz.
The table indicates that
a solution for radiated emission IC modeling exists below 3GHz. This method models the
radiated field of an IC by dipoles placed along the interconnects of the lead frame. The
dipole moments are modeled by the interconnect currents from a network simulation with an
ICEM model [51]. Therefore, the modeling method requires only simulations, but
no measurements.
Although a comparison of results from this method with threedimensional full wave
simulation demonstrated good agreements for canonical structures, a comparison of IC
model results with measurements showed some significant deviations of about 6dB
[52]. The main reasons for the deviations were reported by [52]
to be inaccuracies of the utilized geometrical package model and uncertainties of the
currents on the package. There are currently no results with increased accuracy from this
modeling approach in the literature.
Another approach for modeling the near field of an IC has been presented by
[6]. This method models the package with the threedimensional
full wave simulation program HFSS^{®} and introduces excitation ports at
the chip side and on the PCB side of the package. The ports are excited by frequency
domain excitations, obtained by FFT of time domain network simulations with an ICEM
model. A good agreement of simulation results to measurement results has been achieved by
this method on a 16bit microcontroller with a 144pin TQFP package.
Both methods of [6] and [52] require
threedimensional full wave simulation for the consideration of an enclosure. They do not
provide an explicit relation from the IC model sources to the common mode coupling from
the IC to the enclosure. This makes optimization inefficient and prevents an integration
into the cavity device model developed in the course of this dissertation and predictive
simulations of mTEM measurement results.
The common mode coupling is also the coupling mechanism from an IC to a mTEM cell,
which is evident, because the magnetic and the electric common mode coupling moments of
an IC can be obtained by mTEM measurements [53]. Main standardized EMC
measurements for ICs are based on mTEM cells [54]. This indicates the
significance of the common mode coupling. The coupling of the IC to the mTEM cell is
also modeled in [6]. However, the results of this modeling show
deviations from the measurement results above 300MHz and the modeling is carried out by
using lumped coupling capacitors which have no relation to the previously mentioned near
field model.
This work models the common mode coupling from a trace on a PCB to the parallelplane
cavity field between the PCB ground plane and a metallic enclosure cover by an analytical
formulation.
Only the vertical current segments of the trace couple to the cavity. Therefore, the
coupling can be described by the currents on the two trace ends (source and load
positions), which are obtained from a network simulation of the trace, the load, and the
source. The common mode coupling of an IC can be modeled by the same approach. The
currents on the IC package can be obtained by network simulation with an ICEM model, as
already presented by [6] and [52]. With these
currents on the vertical elements of the package, the common mode coupling can be modeled
accurately up to high cavity resonance frequencies in the GHz range. The model provides
explicit information about the influence of every individual geometric package part on
the overall common mode coupling of the device. This information enables efficient EMC
optimization of both the package geometry and the part placement inside an enclosure.
C. Poschalko: The Simulation of Emission from Printed Circuit Boards under a Metallic Cover