Improved the multiple signal classification algorithm to estimate the complex relative permittivity of material based on the reflection measurement in free-space at X-band

This paper aims to improve the multiple signal classification (MUSIC) algorithm to estimate the complex relative permittivity of a metal-backed planar material sample placed in a free-space based on reflection measurement at X-band. The measurement system consists of a pyramidal horn antena operating at X-band and the material sample with the thickness is changed.