Deep Brain Focusing Using Time-Reversing Metasurface Assisted by PEC Walls

We introduce a metasurface system for high-precision deep brain focusing. This system involves a single (flat) metasurface and four PEC walls forming together a scattering cavity around the head of the subject, where the PEC walls improve the resolution of the focusing from scattering diversity enhancement. The aperture field producing the desired focusing effect is obtained by time-reversing the field radiated by a dipole target model in a full-wave simulator and the metasurface producing this aperture field is synthesized by the susceptibility tensor - Generalized Sheet Transition Condition (GSTC) method. This proof-of-concept system is demonstrated by full-wave simulations, and recommendations are provided for improving the quality of the focusing results in more sophisticated designs.