Measurement of the shielding properties of composite materials: comparison of the dual TEM and noncontact probe methods

A comparative study has been made of the use of a noncontact probe method and the dual TEM cell method for the measurement of the surface impedance of composite materials. The results show that the values of surface impedance obtained by the two methods are in substantial agreement when the samples are pseudo-isotropic. Very different results are obtained by the two methods, however, when the samples are anisotropic because the two techniques induce a different flow of current (circular in the case of the noncontact probe method and laminar in the case of the dual TEM method). Comparison of the results from the two methods has shed light on the structure of carbon composite materials.