Modelling for far-field pathloss of body channel based on plane wave oblique incidence

Calculating the path loss of body channel is significant to link budget for implant communication. In this paper, we use the electromagnetic field boundary conditions of lossy media, reflection and transmission theorems and introduce the tangential equivalent wave impedance to derive the incidence angle, transmission angle, reflection coefficient, transmission coefficient, tangential equivalent wave impedance and the electromagnetic synthesis wave in each human tissue when a plane wave is obliquely incident to the human body, and therefore a far-field path loss model for the human channel based on the oblique incidence of a plane wave to a multi-layer lossy media is proposed. Then taking implant in muscle as an example, the electromagnetic field distribution and path loss of body channel are calculated when TM and TE waves are obliquely accident on human body at different angels and five common industrial communication frequencies. The results show that the reflection of the electromagnetic wave at the incident surface is the key factor affecting the path loss of body channel, and the total path loss is minimized when the frequency is around 1.4 GHz, and the TM wave performance is better than the TE wave, whose the total path loss remains basically the same when the incident angle is less than or equal to 30 degrees. Finally, an FEM-based model is built to validate the analytical model. It shows that both results have a pretty good agreement and the maximum error is only 0.039, which strongly proves the correctness and validation of proposed model.