  In this paper, we discussed the current experiments on the tunneling effect
of electromagnetic energy through narrow channels of $\epsilon$-near-zero(ENZ)
medium in the microwave range. Using the finite element method, we carried out
a full wave simulation of the two kinds of experimental configurations at
present. It was shown that the ability of the electromagnetic waves penetrating
into the ENZ medium is very necessary. The present experimental setups only
using metamaterial-filled narrow channel in the configuration of parallel plate
waveguides are unlikely to realize effective tunneling. Contrarily, the
artificial plasma medium emulated using hollow metallic waveguide can achieve
nearly perfect tunneling in a narrow channel without any transition section
around its cutoff frequency, which exceed the scope of original ENZ tunneling
theory and can be described by a simple equivalent circuit model.
