Bidirectional Half-Duplex Near Field Data Communication System for Biomedical Implantable Devices

This work aims at designing a bidirectional half-duplex near field data communication system for biomedical implantable devices (IMDs) in the category of retinal prostheses. The purpose of IMDs is to substitute sensory or motor functionalities that have been lost due to an injury or a disease and, therefore, they require reliable transfer of a large volume of data either from external artificial sensors to the implant or in the opposite direction. The system’s architecture is based on LSK (load-shift keying) modulated inductively coupled resonators and it is strongly biased towards downlink transmission, from the external unit to the implant. Moreover it is designed to work at a carrier frequency allocated inside the ISM radio band, preferably at 13.56 MHz. The implementation and simulation of the designed system, carried out with the aid of Cadence Virtuoso software, displays the limitations introduced by load-shift keying techniques in applications which require high data rate. Indeed, while LSK proves to be a reasonable choice for uplink transmission, minimizing power consumption in a direction of transmission for which data rate requirements are not that stringent, it becomes rapidly disadvantageous for downlink communication, since it evidently struggles to achieve the challenging data rate specification of 5 Mb/s. This result suggests that exploring alternative modulation techniques, at least for downlink transmission, may lead to enhancing the performance of the system in terms of data rate requirements.