Transmittance and Monostatic Reflectivity of Radar Absorbing Materials for CATR

We present the transmittance and monostatic reflectivity of radar absorbing materials at 650 GHz at vertical polarization. The reflectivity is measured in plane-wave conditions provided with a radar cross section range. The reflectivities range from -70 dB with commercial absorber, TK THz RAM, to -50 dB with commonly available carpets. The reflectivity level of carpets is sufficiently low for use as absorber, and the applicability of carpet absorbers in antenna test range is proved with a full-scale antenna measurement campaign. The transmittance of carpets can be higher than that of commercial absorbers, and additional isolation is needed to achieve low enough transmittance.