Ear-to-Ear On-Body Channel Model for Hearing Aid Applications

The deterministic ear-to-ear on-body channel is modeled by the use of a number of elliptically shaped paths. The semi-major axes of the elliptically shaped paths are adjusted such that they trace the outline of the head. The path gain converges when the number of paths is increased, such that the head is modeled more accurately, and the radiation pattern is sampled in more points. The model is able to take the on-body radiation pattern of the antenna, as well as arbitrary head contours into account. The model is validated by the use of measurements and Ansys HFSS simulations on the specific anthropomorphic mannequin (SAM) head. The model is used with a genetic algorithm in order to synthesize a radiation pattern that is optimal for use with the ear-to-ear on-body channel. The radiation pattern is synthesized in terms of the spherical wave expansion coefficients of the hypothetical small antenna. The variation in the ear-to-ear on-body path gain, due to perturbations of the shape of the nominal SAM head, is studied by the use of a Monte Carlo analysis. The analysis revealed that the path gain that is obtained with a single on-body radiation pattern may vary up to 25 dB.