Abstract
This paper presents a passive phase-shift keying (PPSK) modulator for uplink data transmission for biomedical implants with simultaneous power and data transmission over a single 13.56 MHz inductive link. The PPSK modulator provides a data rate up to 1.35 Mbps with a modulation index between 3% and 38% for a variation of the coupling coefficient between 0.05 and 0.26. This modulation scheme is particularly suited for biomedical implants that have high power demand and low coupling coefficients. The PPSK modulator operates in conjunction with on-off-keying downlink communication. The same inductive link is used to provide up to 100 mW of power to a multi-channel stimulator. The majority of the system on the implant side was implemented as an application specific integrated circuit (ASIC), fabricated in 0.6- [Formula: see text] high voltage CMOS technology. The theory of PPSK modulation, simulated and measured performance evaluation, and comparison with other state-of-the-art impedance modulation techniques is presented. The measured bit error rate around critical coupling at 1.35 Mbps is below 6 ×10-8.
Highlights
I NDUCTIVELY powered implantable neural stimulators, such as cochlear implants [1], visual prostheses [2]–[5], spinal cord stimulators [6], [7], deep brain stimulators [8] and vestibular prostheses [9]–[12], are often equipped with back telemetry, over which the device operational parameters, such as electrode voltage, power supply level, humidity and temper-Manuscript received November 25, 2015; revised March 15, 2016 and April 24, 2016; accepted May 12, 2016
The passive phase-shift keying (PPSK) modulator was designed for use in an integrated stimulator for a vestibular prosthesis [12]
A power telemetry with an integrated PPSK modulator was implemented as part of an implantable stimulator for vestibular prosthesis
Summary
I NDUCTIVELY powered implantable neural stimulators, such as cochlear implants [1], visual prostheses [2]–[5], spinal cord stimulators [6], [7], deep brain stimulators [8] and vestibular prostheses [9]–[12], are often equipped with back telemetry, over which the device operational parameters, such as electrode voltage, power supply level, humidity and temper-. PPSK modulation uses superficially similar circuits to the conventional load impedance modulation, but imposes precise control on the timing of modulation to generate a fast transient response over the inductive link with a relatively high amplitude change. This modulation scheme is suitable for biomedical implants that require a high uplink bandwidth but. The PPSK modulator was designed for use in an integrated stimulator for a vestibular prosthesis [12] (which describes the multi-channel stimulators and the recording unit) It specifies a minimum data rate of 600 kbps and up to 100 mW of power for device operation.
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