Effect of the size of the specimen on reflection coefficient in the free-space method

In this paper, the effect of the size of specimens on reflection coefficients in the free-space method is investigated to clarify the measurable size of a specimen. Square acrylic and Teflon plates were used as specimens. From the experimental results, it is estimated that the size of the specimen needs at least a wavelength in this method. In the case of measurement with a size below a wavelength, it is suggested that correcting the reflection of the reference makes it possible to measure the reflection coefficient. Furthermore, with a comparison between measured and calculated data it is validated that the FDTD method is effective for the analysis on the reflection characteristics of a small size specimen.