Low-Power Wireless Data Transfer System for Stimulation in an Intracortical Visual Prosthesis

Abstract

There is a growing interest to improve the quality of life of blind people. An implanted intracortical prosthesis could be the last resort in many cases of visual impairment. Technology at this moment is at a stage that implementation is at sight. Making the data communication to and from the implanted electrodes wireless is beneficial to avoid infection and to ease mobility. Here, we focus on the stimulation side, or downlink, for which we propose a low-power non-coherent digital demodulator on the implanted receiver. The experimentally demonstrated downlink is on a scaled-down version at a 1 MHz carrier frequency showing a data rate of 125 kbps. This provides proof of principle for the system with a 12 MHz carrier frequency and a data rate of 4 Mbps, which consumes under 1 mW at the receiver side in integrated circuit (IC) simulation. Due to its digital architecture, the system is easily adjustable to an ISM frequency band with its power consumption scaling linearly with the carrier frequency. The tested system uses off-the-shelf coils, which gave sufficient bandwidth, while staying within safe SAR limits. The digital receiver achieved a reduction in power consumption by skipping clock cycles of redundant bits. The system shows a promising pathway to a low-power wireless-enabled visual prosthesis.

Sub-Milliwatt Transceiver IC for Transcutaneous Communication of an Intracortical Visual Prosthesis

“…Similarly to the transmitter design for uplink, the requirements for downlink can be met by taking a system approach aimed at designing a low-power implementation. This involves using low frequency (<100 MHz), an inductive link, phase shift keying (PSK), and a nearly digital receiver with non-coherent demodulation after sampling and by means of edge detection, as introduced in [19,33,34]. The sampling of the received signal makes it possible for a non-coherent demodulation in the BPSK signal by using only edge detection, as described in [35].…”

“…A similar concept was presented in [35], but in our case, the data rate to carrier frequency ratio is not 100% due to practical bandwidth limitations and losses in inductive links. Inductive coils that are designed for transmission and reception create a bandwidth for which the BPSK signal is communicated, and this is band limited by design which leads to about 5-70% data rate to carrier frequency ratio in practice [34]. We aim to be within this range, as delivering a sufficient data rate is the main priority, and because the carrier frequency can be scaled appropriately.…”

“…A count-up number of N = 16 was used to improve flexibility of adjusting the timing range, which corresponds to the most-significant bit of the 5-bit counter in the reset generator. More details on the components and principle of operation can be found in our previous works in [21,34].…”

“…Typical coil sizes range from 15 mm to 40 mm in diameter depending on the size desired. The coupled inductive link from the coils acts as a low-power voltage transformer, boosting the voltage around resonance frequency it is designed for [34]. Typical coil dimensions range from 10 mm to 50 mm in diameter to ensure that the coil self-resonance frequency is much higher than our operating frequency.…”

Design and Implementation of High Performance PPSK demodulator in Biomedical Implant

“…These devices are active implants that require energy sources like solar, infrared & wireless energy transfer for functioning (13) . In implanted system, power (14,15) is the major concern in the https://www.indjst.org/ system design. Due to the lifetime limitation, the battery is not the optimal choice in the implanted device.…”