Investigation of material effects on near-field wireless power transfer

We derive an analytic power transfer efficiency bound for wireless power transfer in the radiating near-field region when a transmitting antenna is surrounded by a finite thickness material shell and a receiving antenna is outside the shell. The derived formulas for both TM and TE mode radiators show good agreement with full-wave simulation. Using the derived theory, lossy dielectric material effects on wireless power transfer are studied for both TM and TE mode radiators. Power transfer measurement through an exterior concrete wall is also reported and compared with the theory.