Measuring permittivity of the dielectric sheet by two kinds of microwave cavities

The formulas were derived for the calculation of the permittivity of dielectric measured in TE 109 mode rectangular cavity and TE 011 mode cylindrical cavity. A testing system based on scalar network analyzer was adopted to measure the same sheet dielectric by the two cavities above respectively. The testing software based on LABVIEW was developed. The results showed that the measuring error was less than 3.8% and repeatability error was than 1.1% by perturbation method in rectangular cavity, while those are 0.4% and 0.3%, by using cylindrical cavity. The automatic measurement of permittivity of dielectric sheet can be achieved by perturbation method in cylindrical cavity.