Modulation Techniques for Biomedical Implanted Devices and Their Challenges

Implanted medical devices are very important electronic devices because of their usefulness in monitoring and diagnosis, safety and comfort for patients. Since 1950s, remarkable efforts have been undertaken for the development of bio-medical implanted and wireless telemetry bio-devices. Issues such as design of suitable modulation methods, use of power and monitoring devices, transfer energy from external to internal parts with high efficiency and high data rates and low power consumption all play an important role in the development of implantable devices. This paper provides a comprehensive survey on various modulation and demodulation techniques such as amplitude shift keying (ASK), frequency shift keying (FSK) and phase shift keying (PSK) of the existing wireless implanted devices. The details of specifications, including carrier frequency, CMOS size, data rate, power consumption and supply, chip area and application of the various modulation schemes of the implanted devices are investigated and summarized in the tables along with the corresponding key references. Current challenges and problems of the typical modulation applications of these technologies are illustrated with a brief suggestions and discussion for the progress of implanted device research in the future. It is observed that the prime requisites for the good quality of the implanted devices and their reliability are the energy transformation, data rate, CMOS size, power consumption and operation frequency. This review will hopefully lead to increasing efforts towards the development of low powered, high efficient, high data rate and reliable implanted devices

An ultra-low-power area-efficient non-coherent binary phase-shift keying demodulator for implantable biomedical microsystems

A novel non-coherent, low-power, area-efficient binary phase-shift keying demodulator for wireless implantable biomedical microsystems is proposed. The received data and synchronized clock signal are detected using a delayed digitized format of the input signal. The proposed technique does not require any kind of oscillator circuit, and due to the synchronization of all circuit signals, the proposed demodulator can work in a wide range of biomedical data telemetry common frequencies in different process/temperature corners. The presented circuit has been designed and post-layout-simulated in a standard 0.18 µm CMOS technology and occupies 17 × 27 µm2 of active area. Post-layout simulation results indicate that with a 1.8 V power supply, power consumption of the designed circuit is 8.5 µW at a data rate of 20 Mbps. The presented demodulation scheme was also implemented on a proof-of-concept circuit board for verifying its functionality

Investigation of high bandwith biodevices for transcutaneous wireless telemetry

PhD ThesisBIODEVICE implants for telemetry are increasingly applied today in various areas applications. There are many examples such as; telemedicine, biotelemetry, health care, treatments for chronic diseases, epilepsy and blindness, all of which are using a wireless infrastructure environment. They use microelectronics technology for diagnostics or monitoring signals such as Electroencephalography or Electromyography. Conceptually the biodevices are defined as one of these technologies combined with transcutaneous wireless implant telemetry (TWIT). A wireless inductive coupling link is a common way for transferring the RF power and data, to communicate between a reader and a battery-less implant. Demand for higher data rate for the acquisition data returned from the body is increasing, and requires an efficient modulator to achieve high transfer rate and low power consumption. In such applications, Quadrature Phase Shift Keying (QPSK) modulation has advantages over other schemes, and double the symbol rate with respect to Binary Phase Shift Keying (BPSK) over the same spectrum band. In contrast to analogue modulators for generating QPSK signals, where the circuit complexity and power dissipation are unsuitable for medical purposes, a digital approach has advantages. Eventually a simple design can be achieved by mixing the hardware and software to minimize size and power consumption for implantable telemetry applications. This work proposes a new approach to digital modulator techniques, applied to transcutaneous implantable telemetry applications; inherently increasing the data rate and simplifying the hardware design. A novel design for a QPSK VHDL modulator to convey a high data rate is demonstrated. Essentially, CPLD/FPGA technology is used to generate hardware from VHDL code, and implement the device which performs the modulation. This improves the data transmission rate between the reader and biodevice. This type of modulator provides digital synthesis and the flexibility to reconfigure and upgrade with the two most often languages used being VHDL and Verilog (IEEE Standard) being used as hardware structure description languages. The second objective of this thesis is to improve the wireless coupling power (WCP). An efficient power amplifier was developed and a new algorithm developed for auto-power control design at the reader unit, which monitors the implant device and keeps the device working within the safety regulation power limits (SAR). The proposed system design has also been modeled and simulated with MATLAB/Simulink to validate the modulator and examine the performance of the proposed modulator in relation to its specifications.Higher Education Ministry in Liby

A Class-E Inductive Powering Link with Backward Data Communications for Implantable Sensor Systems

The design and implementation of a wireless power and data transfer system based on inductive coupling, having the potential to be used in numerous implantable bio-medical sensors and systems, is presented. The system consists of an external (primary) unit and an internal (secondary) unit. The external unit incorporates a high-efficiency switch-mode Class-E amplifier operating at ~200 kHz for driving the primary coil. The secondary unit consists of a parallel resonant coil followed by the power recovery circuitry. Means for backward data communication from the internal to the external unit over the same pair of coils has been realized using a simple FSK-based modulation scheme incorporated into the internal unit. FSK demodulation and associated filtering are integrated with the base inductive powering system. Prototype system test results indicate the inductive link efficiency can exceed 80% under optimum operating conditions with the overall power transfer efficiency of approximately 30%. The communication system is capable of transmitting up to 10kbps of data with the FSK carrier frequency (i.e., middle-frequency) being only 120kHz. The complete system functions reliably over an inter-coil distances exceeding 2.5cm with a 5V dc supply

An Ultra-Miniaturised CMOS Clock and Data Recovery System for Wireless ASK Transmission

Over the years, several clock and data recovery architectures have been proposed for wireless Amplitude Shift Keying (ASK) transmitted signals. State-of-the-art architectures mainly rely on synchronous phase-locked loop circuits or self- sampling systems, both resulting in large area consumption. This work presents a novel CMOS architecture for Clock and Data Recovery (CDR) in miniaturised and wirelessly powered implants. The proposed CDR architecture works at 433.92 MHz and includes: an ASK-demodulator, an on-chip oscillator, a power-on-reset, a control and a recovering block operating in feedback-loop. The ASK-demodulator works for a data rate as high as 6 Mbps and a modulation index in the range of 9-30%. A novel communication protocol is presented for a separated clock and data transmission. The entire CDR architecture occupies 17×89μm2 and consumes 15.01μW while operating with a clock rate of 6 Mbps

Remote Powering and Data Communication Over a Single Inductive Link for Implantable Medical Devices

RÉSUMÉ Les implants médicaux électroniques (Implantable Medical Devices - IMDs) sont notamment utilisés pour restaurer ou améliorer des fonctions perdues de certains organes. Ils sont capables de traiter des complications qui ne peuvent pas être guéries avec des médicaments ou par la chirurgie. Offrant des propriétés et des améliorations curatives sans précédent, les IMDs sont de plus en plus demandés par les médecins et les patients. En 2017, le marché mondial des IMD était évalué à 15,21 milliards de dollars. D’ici 2025, il devrait atteindre 30,42 mil-liards de dollars, soutenu par un taux de croissance annuel de 9,24% selon le nouveau rapport publié par Fior Markets. Cette expansion entraîne une augmentation des exigences pour as-surer des performances supérieures, des fonctionnalités supplémentaires et une durée de vie plus longue. Ces exigences ne peuvent être satisfaites qu’avec des techniques d’alimentation avancées, un débit de données élevé et une électronique miniaturisée robuste. Construire des systèmes capables de fournir toutes ces caractéristiques est l’objectif principal d’un grand nombre de chercheurs. Parmi plusieurs technologies sans fil, le lien inductif, qui consiste en une paire de bobines à couplage magnétique, est la technique sans fil la plus largement utilisée pour le transfert de puissance et de données. Cela est dû à sa simplicité, sa sécurité et sa capacité à transmettre à la fois de la puissance et des données de façon bidirectionnelle. Cependant, il existe encore un certain nombre de défis concernant la mise en œuvre d’un tel système de transfert d’énergie et de données sans fil (Wireless Power and Data Transfer - WPDT system). Un défi majeur est que les exigences pour une efficacité de transfert d’énergie élevée et pour une communication à haut débit sont contradictoires. En fait, la bande passante doit être élargie pour des débits de données élevés, mais réduite pour une transmission efficace de l’énergie. Un autre grand défi consiste à réaliser un démodulateur fonctionnant à haute vitesse avec une mise en œuvre simple et une consommation d’énergie ultra-faible. Dans ce projet, nous proposons et expérimentons un nouveau système WPDT dédié aux IMD permettant une communication à haute vitesse et une alimentation efficace tout en maintenant une faible consommation d’énergie, une petite surface de silicium et une mise en œuvre simple du récepteur. Le système proposé est basé sur un nouveau schéma de modulation appelé "Carrier Width Modulation (CWM)", ainsi que sur des circuits de modulation et de démodulation inédits. La modulation consiste en un coupe-circuit synchronisé du réservoir LC primaire pendant un ou deux cycles en fonction des données transmises.----------ABSTRACT Implantable Medical Devices (IMDs) are electronic implants notably used to restore or en-hance lost organ functions. They may treat complications that cannot be cured with medica-tion or through surgery. O˙ering unprecedented healing properties and enhancements, IMDs are increasingly requested by physicians and patients. In 2017, the worldwide IMD market was valued at USD 15,21 Billion. By 2025, it is expected to attain USD 30.42 Billion sus-tained by a compound annual growth rate of 9.24% according to a recent report published by Fior Markets. This expansion is bringing-up more demand for higher performance, additional features, and longer device lifespan and autonomy. These requirements can only be achieved with advanced power sources, high-data rates, and robust miniaturized electronics. Building systems able to provide all these characteristics is the main goal of many researchers. Among several wireless technologies, the inductive link, which consists of a magnetically-coupled pair of coils, is the most widely used wireless technique for both power and data transfer. This is due to its simplicity, safety, and ability to provide simultaneously both power and bidirectional data transfer to the implant. However there are still a number of challenges regarding the implementation of such Wireless Power and Data Transfer (WPDT) systems. One main challenge is that the requirements for high Power Transfer Eÿciency (PTE) and for high-data rate communication are contra-dictory. In fact, the bandwidth needs to be widened for high data rates, but narrowed for eÿcient power delivery. Another big challenge is to implement a high-speed demodulator with simple implementation and ultra-low power consumption. In this project, we propose and experiment a new WPDT system dedicated to IMDs allow-ing high-speed communication and eÿcient power delivery, while maintaining a low power consumption, small silicon area, and simple implementation of the receiver. The proposed system is based on a new Carrier Width Modulation (CWM) scheme, as well as novel modu-lation and demodulation circuits. The modulation consists of a synchronized opening of the primary LC tank for one or two cycles according to the transmitted data. Unlike conventional modulation techniques, the data rate of the proposed CWM modulation is not limited by the quality factors of the primary and secondary coils. On the other hand, the proposed CWM demodulator allows higher-speed demodulation and simple implementation, unlike conven-tional demodulators for a similar modulation scheme. It also o˙ers a wide range of data rates under any selected frequency from 10 to 31 MHz

A TRANSCEIVER DESIGN FOR IMPLANTABLE MEDICAL DEVICES

Master'sMASTER OF ENGINEERIN