A Study on Improvement of the Accuracy in the Ellipsometry Method for Complex Permittivities of Materials in Millimeter-Wave Region

Abstract

The ellipsometry method is well known as one of methods to measure a refractive index in optical region. This method is extended to a measurement for complex permittivities of materials at a millimeter-wave frequency. This method has little limitation on a sample size because of the free space method. The uncertainty on the measurement of phases in reflection doesn’t occur because this method is based on a scalar measurement. But a large uncertainty due to a free-space method was realized. Only 2nd order Fourier coefficients are obtained in an ideal case. But measured data contained higher order coefficients up to the 6th, because all reflected electromagnetic power could not be received by a horn antenna. We propose an effective method to extract Fourier coefficients only corresponding to ellipsometry parameters. Complex permittivitie of a lossy material in millimeter-wave region can be measured in high accuracy by the improved ellipsometry method.