At the investigated frequencies the human body is characterized by high losses, therefore electromagnetic fields propagating inside the body will be strongly attenuated. In order to estimate the maximum distance which can guarantee a reliable communication link, a Path Loss (PL) model is necessary to point out the entity of the attenuations which affect the propagation. In [7], a 3-D numerical model is set up in different commercial software to identify the path loss in homogeneous medium and validated with measurement. The possibility of electromagnetic (EM) communication is discussed in [8] on the basis of the fact that THz band can be used as the operation frequency range for future EM nano-transceivers because of the characteristics of the carbon nano-tube and graphene [9,10]; in addition, a path loss model for communication in the air with different vapor concentration is proposed
. However, there are few papers working on the in-body THz modelling. Recently, the modified Friis equation is used to calculate the total path loss, the sum of the spreading path loss and the absorption path loss, and validates the possibility of the application of the THz wave in nano-communication [11].