Investigation of Near-Field Wireless Power Transfer in the Presence of Lossy Dielectric Materials

We derive an analytic upper bound in power transfer efficiency (PTE) for wireless power transfer between a pair of antennas separated by a spherical material shell. The formulation is based on the free space PTE bound derived previously, and incorporates an additional pair of incoming and outgoing spherical waves within the shell. The derived PTE bounds are verified using numerical simulation via FEKO and show good agreement for both TM mode and TE mode radiators. Using the derived theory, lossy dielectric material effects on wireless power transfer are studied. Power transfer measurements through walls are also reported and compared with the theory.