Multi-focal transmission acoustic phase holograms in contactless ultrasonic power transfer systems

Using a pre-designed, simple, and cost-effective acoustic hologram alongside a single ultrasonic transducer, as an acoustic source/transmitter, enables new capabilities in multi-focal focusing, acoustic patterning, and contactless ultrasonic power transfer (UPT), to selectively charge sensors/receivers. In this work, different multi-focal holograms are designed that cover single-to four-focus acoustic patterning for UPT purposes. The holograms are numerically designed to create multi-focal pressure patterns in a target plane where an array of receivers are placed. The incident sound wave from a transmitter, after passing through the hologram, is manipulated, hence, the output field is the desired pressure field, which excites the receivers located at the pre-determined focal points more significantly. Proof-of-concept experiments are also performed for a five-element receiver setup, using a two-focus hologram, to selectively power two specific receivers. The experiments indicate a significant electrical average power output enhancement ratio of 23.4 from the targeted receivers, compared to untargeted ones, which proves the functionality of the designed multi-focal holograms in arbitrarily patterning the con tactless transfer of ultrasonic power.

Automated summary

This paper proposes a method using acoustic holograms and a single ultrasonic transducer to achieve multi-focal focusing and acoustic patterning for selective charging of sensors/receivers. Numerically designed holograms are used to generate multi-focal pressure patterns in a target plane, resulting in significant excitation of receivers located at the focal points. Experimental results show a significant enhancement in power output for the targeted receivers.