Complex permittivity estimation from free space RCS measurement

Non-destructive and non-contacting estimation of the complex permittivity of the solid materials has been proposed using the monostatic RCS measurement from the specular reflection surface. In order to isolate the surface reflection contribution from the total scattering response, time gating method is utilized. The frequency domain RCS is measured first at a certain frequency band, and the corresponding time domain result is calculated via inverse Fourier Transformation. After identifying the surface reflection contribution and selecting it with a certain time width, Fourier transformation is used to obtain the desired surface response in the frequency domain. These RCS results are then utilized to estimate the surface reflection coefficients and their permittivities. The proposed method has been tested to evaluate the permittivities of cubic granite and synthetic phantom material, and the results are compared with those obtained by a coaxial probe method. Good agreement has been found between them and the validity of our method has been confirmed.