Atmospheric Attenuation of 400 GHz Radiation Due to Water Vapor

We present an experimental study of electromagnetic losses resulting from atmospheric attenuation due to water vapor on 400 GHz radiation. A hermetically sealed, high quality factor quasi-optical resonator system permits the precise control of the atmospheric water vapor content, and allows for measurement of electromagnetic losses. The empirically determined losses are compared with predictions by various different electromagnetic attenuation models. Close agreement is demonstrated with four of the models, while another differs by more than an order of magnitude at higher values of water content.