Characterization of Radar Absorbing Materials at 75 GHz - 90 GHz using Free-Space System

In this paper, we present a focused beam free-space measurement methodology for characterizing radar absorbing materials in the W-band. The measurements are obtained in the transmission mode using a PNA network analyzer with millimeter wave frequency extenders to provide four S-parameters over the W-band from 75 to 90 GHz. Good agreement is achieved between the calculated and the measured S-parameters of the sample under test that validates the extraction algorithm. The extracted complex relative permittivity results are compared with the commercial data.