Microwave and millimeter-wave characterization of conductive ink film in rectangular waveguide

An accurate approach to characterize the sheet impedance of thin conductive ink in rectangular waveguide is reported. This method allows retrieval of the sheet impedance without prior characterization of the supporting dielectric substrate. The ink sample is positioned between two waveguide flanges, introducing a discontinuous gap. The effect of the physical discontinuity can be removed by an additional measurement of the sample without ink layer. We have examined the extraction accuracy of the proposed method within the operating band of the waveguide, and also for various substrate thicknesses. Experimental results demonstrate the applicability of the proposed approach for sheet impedance measurements of ink films on both thin or thick (up to about quarter wavelength) substrates.