Characterization of loaded TEM-waveguides using time-domain reflectometry

Abstract

An approach is presented to characterize the load state of a TEM-waveguide using the local characteristic impedance Z/sub c/(z) derived from time-domain reflectometry (TDR) measurements. The field homogeneity and the field polarization can be estimated using the deviation from the intended Z/sub c/=50 /spl Omega/ of the empty TEM-waveguide. Considering wave propagation only in the TEM-mode an analytical relationship between load state and characteristic impedance is derived. Multiple reflections due to the nonuniformity of the loaded TEM-waveguide and higher order modes excited by the load are taken into account. Experimental results are presented using a GTEM-cell with several load states.