Numerical and Experimental Investigation of Field Distribution in Waveguide Filled with Anisotropic Single Negative Metamaterial

A field distribution in a rectangular waveguide filled with anisotropic single-negative (SNG) metamaterial is analyzed theoretically, numerically and experimentally. A highly simplified scenario with ideal lossless, continuous (either mu-negative (MNG) or epsilon-negative (ENG)) filling material is used in theoretical analysis. The results show that distributions of magnitudes of E and H fields are similar to the associated distributions in ordinary waveguide (filled with double-positive (DPS) material) that operates above cut-off frequency. However, the crucial difference, responsible for recently demonstrated peculiar phenomenon of backward wave propagation below cut-off is a pattern of field lines of either H field (a case with MNG filling) or E field (a case with ENG filling). Numerical approach that dealt with realistic structures (double-ring-resonator-based MNG metamaterial and thin-wire-based ENG metamaterial) confirmed existence of backward-wave propagation. Two experimental waveguides filled with double-ring resonators (an MNG filling) and thin wires (an ENG filling) were successfully designed, manufactured and tested in 8 GHz band. The backward-wave propagation was verified by measurement of a phase distribution along a waveguide with the help of a small E field probe