Fundamental Trade-Offs Between Power and Data Transfer in Inductive Links for Biomedical Implants

Area of Science:

• Wireless Power Transfer
• Near-Field Communication
• Electromagnetics

Background:

• Simultaneous power and data transfer (SPDT) is crucial for many wireless applications.
• Near-field inductive links face fundamental trade-offs between power transfer efficiency (PTE) and spectral efficiency.
• Optimizing this trade-off is challenging due to varying link parameters like distance and coupling.

Purpose of the Study:

• To investigate the trade-offs between PTE and spectral efficiency in near-field inductive links.
• To develop a method for real-time adaptation to optimize the power-data transfer balance.
• To demonstrate a prototype system capable of autonomous optimization.

Main Methods:

• Mathematical analysis to model the relationship between PTE, channel capacity, and link parameters (coupling coefficient k, load resistance).
• Development of a real-time adaptation strategy using load resistance and modulation type.
• Implementation of a prototype using an ultrasound transducer to measure coil-coil distance (d).

Main Results:

• The optimal power-data trade-off is highly dependent on the coupling coefficient (k), which decreases with axial distance (d).
• A prototype demonstrated autonomous optimization of data rate (up to ~50 Mbps) and PTE (up to ~25%) for distances between 4-15 mm.
• The system operates at a center frequency of 13.56 MHz.

Conclusions:

• Real-time adaptation of link parameters enables dynamic optimization of SPDT.
• The demonstrated prototype validates the proposed approach for efficient wireless power and data transfer.
• This research offers a pathway to improved performance in applications requiring simultaneous wireless power and data transmission.