Transmission Mechanism of Wearable Device for On-Body Wireless Communications

In order to analyze and investigate the transmission mechanism of the wearable device for on-body wireless communications, the high-frequency asymptotic representations for the scattered electromagnetic (EM) fields are derived and discussed in this paper. In considering the propagation characteristics of the wearable device attached to an arm, we approximate the arm as a dielectric circular cylinder. The eigenfunction solutions for the scattered fields by the dielectric circular cylinder when the EM wave is radiated from a dipole antenna are presented, and we transform the eigenfunction solutions into the high-frequency asymptotic representations. The measured field distribution, the calculated value using the finite-difference time-domain method, and the calculated value of the high-frequency asymptotic solution are compared with the calculated eigenfunction solution as a reference, and their validity and accuracy are confirmed. Finally, by examining the integrand of the eigenfunction solutions for the scattered field in detail, it is shown that the signal transmission channel could be mostly dealt with by the contribution of the propagating wave. However, in the case where the observation point is in the vicinity of the cylinder, the dominant signal transmission channel includes not only the contribution of the propagating wave but also the contribution of the quasistatic field.