Development of Bio-Implanted Micro-System With Self-Recovery Ask Demodulator for Transcutaneous Applications

Abstract

This paper deals with the development of bio-implanted micro-system with low-power and high data rate based on amplitude shift keying (ASK) modulation technique to stimulate nerves and muscles. The modified system is operated by a low-frequency band 13.56 MHz according to the industrial-scientific-medical (ISM) bands to avoid the biological tissue damage. The data rate on the demodulator side is from 1 Mb/s and up to 1.5 Mb/s depending of generating binary signal (T BIT = 1 μs or 0.5 μs) with modulation index of 13% and modulation rate 7.3%, 9% and 11%, respectively. The proposed inductive coupling link achieves 73% of link efficiency. The modified rectifier with self-threshold voltage cancellation techniques and voltage regulator without thermal protection circuit and without passive elements occupies small area that is modified to generate adequate and stable DC voltages of 1.8 V. A new ASK demodulator structure based on two comparators is developed to extract a synchronized demodulated signal with minimum error. Thereby no need for clock recovery circuit and delay-locked loops (DLL) circuits for data synchronization at 1 Mb/s and 1.250 Mb/s of speed. The system designed using OrCAD Pspice 16.2 is based on 0.35 μm technologies.

Unique Micro System Stimulator with High Data Rate and Efficient Power Recovery Circuit

“…This parasitic resistance having low impedance depending of the coils dimensions such as total length, thickness, permeability constant and relative permeability of the conductor and depth of skin [21,22]. The coefficient of coupling (K) must be 0 < K <1 [23] and calculated as given in (9)…”

“…The efficiency improvement of the rectifier is the most challenging part, especially in low power [24]. To improve the RF-DC MOSFET rectifies efficiency, the switching loss transistor (channel size) must be considered [9]. In the proposed embedded system, a half wave rectifier utilizing low-drop voltage with low-leakage CMOS diodes is developed by utilizing one NMOST and one capacitor.…”

“…Lastly, the implanted micro system's structural design operated at 13.56 MHz and with 1.8DC of voltage. This was used for powering a non-coherent ASK demodulator, which has self-data synchronisation and no clock recovery circuit to enable a (1-1.25) Mb/s transfer [9]. This structure utilised two comparators and one buffer for the extraction of the data that led to an increase in the power consumption and towards an enlargement in size.…”

Suggested Methods to Solve the Coils Misalignment for the Biomedical Implants

“…This method has several drawbacks due to the battery-limited lifetime, size and chemical side effects [3]. The inductive coupling link is the safer method that can be used to power the implanted devices for long-term period and during light patient mode [4]. The inductive link method consists of two parts; external part fixed outside the body and internal part integrated inside the human body [5].…”

“…The power and data transmissions are done by external and internal coils inductively as shown in Figure 1. In general, the transcutaneous Bio-implantable device which use the magnetic coupling for short communication, suffer from many problems, such as short-range, loss of coupling, attenuated power and coils misalignment [6]. The major problems of the inductive coupling link is the misalignment between coils, which causes low data rate and power transmission [7].…”