The study on the continuum absorption of THz wave in atmosphere

The rapid development of the communication technology and sensing applications calls for broader bandwidth and faster speed. The influence of atmosphere on the propagation character of THz wave can mainly fall into two categories: the scattering of the particles in the atmosphere and the absorption of atmosphere molecules which can be divided into two aspects: line-by-line and continuum absorption. The most controversial point is the calculation of continuum absorption. The specific attenuation of different humidity are calculated by AM model and the modified VVW line shape method and compared with that of ITU-R P.676-9. The continuum absorption of the AM model is calculated using the MT-CKD method, another method to calculate the continuum absorption is to introduce continuum-like terms of water vapor and dry air which is used in the modified VVW line shape method. The result shows a better agreement of the modified VVW line shape method than that of the AM model because the coefficient can be modified to fit the ITU-R P.676-9, and the difference between the AM model and the ITU-R P.676-9 is small, too. The best fit coefficients of modified VVW line shape method for different humidity are obtained. And the relation of the coefficients and the humidity can be expressed by two regressed equations, and the humidity modification is included in the new correction terms.