Physics-Based Prediction of Atmospheric Transfer Characteristics at Terahertz Frequencies

The amplitude and phase distortions of radar echo signal will cause the emergence of undesirable ghost scattering points, which degrade the quality of terahertz (THz) radar images. In this paper, a physics-based procedure is presented to predict the atmospheric attenuation and dispersion characteristics at THz frequencies, which is mainly based on the line-by-line calculation method with a specific modification in phase-shift prediction. The line-by-line parameters provided by the high-resolution transmission spectroscopic database and atmospheric condition parameters obtained from the Air Force Geophysics Laboratory reference atmospheric constituent profiles are adopted to predict the atmospheric transmittance and the phase shift for specific transfer paths. The results are compared with measured data to demonstrate the accuracy, while the proposed procedure is used to analyze the impacts of atmospheric transfer characteristics on radar imaging via the high-resolution range profile simulation. The signal distortion is interpreted in terms of paired echoes to illustrate the importance of frequency band selection for high-resolution imagery at THz frequencies.