Investigation of Resonator BWO-Based Spectroscopy of the Atmosphere in the THz Region

This paper intends to give a code about atmospheric propagation effects affecting terahertz (THz) communication system. The main focus is on attenuation caused by atmospheric gases with the radiation transmission theory and the empirical continuum absorption based on the HITRAN database. Theoretical aspects about them are presented, emphasizing on those which deserve special attention as frequency increases. Laboratory measurements of the absorption spectra of laboratory air and major atmospheric gases mixed with water vapor in the 250 - 350 GHz frequency range at atmospheric pressure and room temperature on a basis of backward wave oscillators (BWOs) are obtained. The results of experiments are compared with the calculations. It is found that the water vapor transmittance is greater than the calculation. Data of these measurements agree with the results of analysis of atmospheric spectra with in statistical accuracy of experiments. Accurate measurements are also needed for further studies of the physics of the molecules and their interactions. The investigation makes it significant for enhancing accuracy of models of radiation propagation in the atmosphere.