A free-space method for measurement of complex permittivity of double-layer dielectric materials at microwave frequencies

Abstract

Two methods for the calculation of complex permittivity of double-layer dielectric materials measured by a spot-focusing free-space measurement system have been developed. Standard materials have been used to test these methods and further works will be carried out on SiO 2 wafer. The dielectric constants obtained were close to the published values. The two methods developed are Transmission Method and Metal-Backed Method. The S 11 , S 21 , and S 22 are measured for Transmission Method, while only S 11 is measured for Metal-Backed Method. In both methods, the samples are sandwiched between two Teflon plates which are quarter wavelength at mid-band frequency. Results are reported in the frequency range of 18–26GHz.