Aplicação de um modulador PPSK em um sistema de biotelemetria com enlace indutivo de três bobinas

Abstract

Inductive links are widely used in biotelemetry systems since they simultaneously enable power transfer from a reading unit to an implantable unit, and data communication between these units. The early two-coil inductive links were applied extensively despite the relatively low power transfer efficiency (PTE). In order to increase the PTE, multi-coil inductive links were introduced. Data modulators based on Load Shift Keying (LSK) modulation technique are commonly employed for data transmission in the implant (uplink) due to the simplicity of the circuit. However, switching a load in the power circuit of the implant causes significant power loss. To overcome this drawback, a Passive Phase Shift Keying (PPSK) modulator has been developed and just applied in two-coil inductive links. The present work aims to demonstrate that a PPSK modulator can be applied in three-coil biotelemetry systems, combining the advantages of PPSK modulation and multi-coil link. This hypothesis was validated from a three-coil inductive link and assuming an embedded system as the implantable unit, which allowed the simulation of signal acquisition and uplink data communication. The practical system enabled a transmission data rate of 100 kbps for a distance between coils of 18 mm, and also was capable to provide a power of 30 mW to the embedded system.