Modeling the cavity and slot modes of a shielding enclosure
A metallic shielding enclosure with a thin slot excited by a vertical wire is modeled in FEKO and the delivered power is computed to identify the various cavity and slot modes for this structure. The FEKO results are favorably compared to published simulated and measured results.
Problem description
The geometry consists of a 30 x 22 x 14cm metallic enclosure with a 12 x 0.2cm rectangular slot. The enclosure is excited by a vertical wire running from the top to the bottom of the cavity which is fed at the top by a 50 Ohm coaxial cable and loaded with a 47 Ohm load at the bottom.
FEKO model
In FEKO the enclosure is modeled as a cuboid with infinitely thin PEC walls with the thin slot aperture cut out. The feed wire is excited with a voltage source at the top and loaded at the bottom.
Figure 1. Geometry of the shielding enclosure (top face removed to show internal detail - thin slot aperture and feed wire).
Simulation results
The power delivered by the source to the structure (the power dissipated in the 47 Ohm load as well as the power radiated into free space) was computed from 700 MHz to 1.6 GHz. This identifies the various cavity and slot modes. The results compare very well with the simulated and measured results reported in the reference [1].
Figure 2. Delivered power computed by FEKO showing the resonances of the cavity and slot modes.
[1] M. Li, J. Nuebel, J. L. Drewniak, R. E. DuBroff, T. H. Hubing, and T. P. VanDoren, “EMI from cavity modes of shielding enclosures-FDTD modeling and measurements,” IEEE Trans. Electromagn. Compat., vol. 42, pp. 29–38, Feb. 2000.
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