Bandwidth limitations of TEM cells due to resonances.

The first eight to ten TEmnp resonances have been identified in one large (6.1 X 7.3 X 13.0 m) and one small (1.0 X 0.6 X 2.0 m) TEM cell. The resonant frequencies fit a new equivalent coaxial box model with the effective length of the box depending on the mode. Weakly propagating TEmn modes were also detected at frequencies above their respective first-resonance frequencies. A biological body or metal box at the center of the test zone interacts strongly with the TE10p and TE11p resonances, but not with the TE01p resonances. These interactions cause bandwidth limitations in the use of TEM cells for bioeffects dosimetry studies, EMC testing, and probe calibration work.