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

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 TRANSCEIVER DESIGN FOR IMPLANTABLE MEDICAL DEVICES

Master'sMASTER OF ENGINEERIN

Wireless power and data transmission to high-performance implantable medical devices

Novel techniques for high-performance wireless power transmission and data interfacing with implantable medical devices (IMDs) were proposed. Several system- and circuit-level techniques were developed towards the design of a novel wireless data and power transmission link for a multi-channel inductively-powered wireless implantable neural-recording and stimulation system. Such wireless data and power transmission techniques have promising prospects for use in IMDs such as biosensors and neural recording/stimulation devices, neural interfacing experiments in enriched environments, radio-frequency identification (RFID), smartcards, near-field communication (NFC), wireless sensors, and charging mobile devices and electric vehicles. The contributions in wireless power transfer are the development of an RFID-based closed-loop power transmission system, a high-performance 3-coil link with optimal design procedure, circuit-based theoretical foundation for magnetic-resonance-based power transmission using multiple coils, a figure-of-merit for designing high-performance inductive links, a low-power and adaptive power management and data transceiver ASIC to be used as a general-purpose power module for wireless electrophysiology experiments, and a Q-modulated inductive link for automatic load matching. In wireless data transfer, the contributions are the development of a new modulation technique called pulse-delay modulation for low-power and wideband near-field data communication and a pulse-width-modulation impulse-radio ultra-wideband transceiver for low-power and wideband far-field data transmission.Ph.D

A Wireless, High-Voltage Compliant, and Energy-Efficient Visual Intracortical Microstimulator

RÉSUMÉ L’objectif général de ce projet de recherche est la conception, la mise en oeuvre et la validation d’une interface sans fil intracorticale implantable en technologie CMOS avancée pour aider les personnes ayant une déficience visuelle. Les défis majeurs de cette recherche sont de répondre à la conformité à haute tension nécessaire à travers l’interface d’électrode-tissu (IET), augmenter la flexibilité dans la microstimulation et la surveillance multicanale, minimiser le budget de puissance pour un dispositif biomédical implantable, réduire la taille de l’implant et améliorer le taux de transmission sans fil des données. Par conséquent, nous présentons dans cette thèse un système de microstimulation intracorticale multi-puce basée sur une nouvelle architecture pour la transmission des données sans fil et le transfert de l’énergie se servant de couplages inductifs et capacitifs. Une première puce, un générateur de stimuli (SG) éconergétique, et une autre qui est un amplificateur de haute impédance se connectant au réseau de microélectrodes de l’étage de sortie. Les 4 canaux de générateurs de stimuli produisent des impulsions rectangulaires, demi-sinus (DS), plateau-sinus (PS) et autres types d’impulsions de courant à haut rendement énergétique. Le SG comporte un contrôleur de faible puissance, des convertisseurs numérique-analogiques (DAC) opérant en mode courant, générateurs multi-forme d’ondes et miroirs de courants alimentés sous 1.2 et 3.3V se servant pour l’interface entre les deux technologies utilisées. Le courant de stimulation du SG varie entre 2.32 et 220μA pour chaque canal. La deuxième puce (pilote de microélectrodes (MED)), une interface entre le SG et de l’arrangement de microélectrodes (MEA), fournit quatre niveaux différents de courant avec la valeur maximale de 400μA par entrée et 100μA par canal de sortie simultanément pour 8 à 16 sites de stimulation à travers les microélectrodes, connectés soit en configuration bipolaire ou monopolaire. Cette étage de sortie est hautement configurable et capable de délivrer une tension élevée pour satisfaire les conditions de l’interface à travers l’impédance de IET par rapport aux systèmes précédemment rapportés. Les valeurs nominales de plus grandes tensions d’alimentation sont de ±10V. La sortie de tension mesurée est conformément 10V/phase (anodique ou cathodique) pour les tensions d’alimentation spécifiées. L’incrémentation de tensions d’alimentation à ±13V permet de produire un courant de stimulation de 220μA par canal de sortie permettant d’élever la tension de sortie jusqu’au 20V par phase. Cet étage de sortie regroupe un commutateur haute tension pour interfacer une matrice des miroirs de courant (3.3V /20V), un registre à décalage de 32-bits à entrée sérielle, sortie parallèle, et un circuit dédié pour bloquer des états interdits.----------ABSTRACT The general objective of this research project is the design, implementation and validation of an implantable wireless intracortical interface in advanced CMOS technology to aid the visually impaired people. The major challenges in this research are to meet the required highvoltage compliance across electrode-tissue interface (ETI), increase lexibility in multichannel microstimulation and monitoring, minimize power budget for an implantable biomedical device, reduce the implant size, and enhance the data rate in wireless transmission. Therefore, we present in this thesis a multi-chip intracortical microstimulation system based on a novel architecture for wireless data and power transmission comprising inductive and capacitive couplings. The first chip is an energy-efficient stimuli generator (SG) and the second one is a highimpedance microelectrode array driver output-stage. The 4-channel stimuli-generator produces rectangular, half-sine (HS), plateau-sine (PS), and other types of energy-efficient current pulse. The SG is featured with low-power controller, current mode source- and sinkdigital- to-analog converters (DACs), multi-waveform generators, and 1.2V/3.3V interface current mirrors. The stimulation current per channel of the SG ranges from 2.32 to 220μA per channel. The second chip (microelectrode driver (MED)), an interface between the SG and the microelectrode array (MEA), supplies four different current levels with the maximum value of 400μA per input and 100μA per output channel. These currents can be delivered simultaneously to 8 to 16 stimulation sites through microelectrodes, connected either in bipolar or monopolar configuration. This output stage is highly-configurable and able to deliver higher compliance voltage across ETI impedance compared to previously reported designs. The nominal values of largest supply voltages are ±10V. The measured output compliance voltage is 10V/phase (anodic or cathodic) for the specified supply voltages. Increment of supply voltages to ±13V allows 220μA stimulation current per output channel enhancing the output compliance voltage up to 20V per phase. This output-stage is featured with a high-voltage switch-matrix, 3.3V/20V current mirrors, an on-chip 32-bit serial-in parallel-out shift register, and the forbidden state logic building blocks. The SG and MED chips have been designed and fabricated in IBM 0.13μm CMOS and Teledyne DALSA 0.8μm 5V/20V CMOS/DMOS technologies with silicon areas occupied by them 1.75 x 1.75mm2 and 4 x 4mm2 respectively. The measured DC power budgets consumed by low-and mid-voltage microchips are 2.56 and 2.1mW consecutively

Ultra-Wideband Transceiver with Error Correction for Cortical Interfaces in NanometerCMOS Process

This dissertation reports a high-speed wideband wireless transmission solution for the tight power constraints of cortical interface application. The proposed system deploysImpulse Radio Ultra-wideband (IR-UWB) technique to achieve very high-rate communication. However, impulse radio signals suffer from significant attenuation within the body,and power limitations force the use of very low-power receiver circuits which introduce additional noise and jitter. Moreover, the coils’ self-resonance has to be suppressed to minimize the pulse distortion and inter-symbol interference, adding significant attenuation. To compensate these losses, an Error correction code (ECC) layer is added for functioning reliably to the system. The performance evaluation is made by modeling a pair of physically fabricated coils, and the results show that the ECC is essential to obtain the system’s reliability. Furthermore, the gm/ID methodology, which is based on the complete exploration ofall inversion regions that the transistors are biased, is studied and explored for optimizingthe system at the circuit-level. Specific focuses are on the RF blocks: the low noise am-plifier (LNA) and the injection-locked voltage controlled oscillator (IL-VCO). Through the analytical deduction of the circuit’s features as the function of the gm/ID for each transistor, it is possible to select the optimum operating region for the circuit to achieve the target specification. Other circuit blocks, including the phase shifter, frequency divider,mixer, etc. are also described and analyzed. The prototype is fabricated in a 65-nm CMOS(Complementary Metal-Oxide-Semiconductor) process

High-performance wireless power and data transfer interface for implantable medical devices

D’importants progès ont été réalisés dans le développement des systèmes biomédicaux implantables grâce aux dernières avancées de la microélectronique et des technologies sans fil. Néanmoins, ces appareils restent difficiles à commercialier. Cette situation est due particulièrement à un manque de stratégies de design capable supporter les fonctionnalités exigées, aux limites de miniaturisation, ainsi qu’au manque d’interface sans fil à haut débit fiable et faible puissance capable de connecter les implants et les périphériques externes. Le nombre de sites de stimulation et/ou d’électrodes d’enregistrement retrouvés dans les dernières interfaces cerveau-ordinateur (IMC) ne cesse de croître afin d’augmenter la précision de contrôle, et d’améliorer notre compréhension des fonctions cérébrales. Ce nombre est appelé à atteindre un millier de site à court terme, ce qui exige des débits de données atteingnant facilement les 500 Mbps. Ceci étant dit, ces travaux visent à élaborer de nouvelles stratégies innovantes de conception de dispositifs biomédicaux implantables afin de repousser les limites mentionnées ci-dessus. On présente de nouvelles techniques faible puissance beaucoup plus performantes pour le transfert d’énergie et de données sans fil à haut débit ainsi que l’analyse et la réalisation de ces dernières grâce à des prototypes microélectroniques CMOS. Dans un premier temps, ces travaux exposent notre nouvelle structure multibobine inductive à résonance présentant une puissance sans fil distribuée uniformément pour alimenter des systèmes miniatures d’étude du cerveaux avec des models animaux en ilberté ainsi que des dispositifs médicaux implantbles sans fil qui se caractérisent par une capacité de positionnement libre. La structure propose un lien de résonance multibobines inductive, dont le résonateur principal est constitué d’une multitude de résonateurs identiques disposés dans une matrice de bobines carrées. Ces dernières sont connectées en parallèle afin de réaliser des surfaces de puissance (2D) ainsi qu’une chambre d’alimentation (3D). La chambre proposée utilise deux matrices de résonateurs de base, mises face à face et connectés en parallèle afin d’obtenir une distribution d’énergie uniforme en 3D. Chaque surface comprend neuf bobines superposées, connectées en parallèle et réailsées sur une carte de circuit imprimé deux couches FR4. La chambre dispose d’un mécanisme naturel de localisation de puissance qui facilite sa mise en oeuvre et son fonctionnement. En procédant ainsi, nous évitons la nécessité d’une détection active de l’emplacement de la charge et le contrôle d’alimentation. Notre approche permet à cette surface d’alimentation unique de fournir une efficacité de transfert de puissance (PTE) de 69% et une puissance délivrée à la charge (PDL) de 120 mW, pour une distance de séparation de 4 cm, tandis que le prototype de chambre complet fournit un PTE uniforme de 59% et un PDL de 100 mW en 3D, partout à l’intérieur de la chambre avec un volume de chambre de 27 × 27 × 16 cm3. Une étape critique avant d’utiliser un dispositif implantable chez les humains consiste à vérifier ses fonctionnalités sur des sujets animaux. Par conséquent, la chambre d’énergie sans fil conçue sera utilisée afin de caractériser les performances d’ une interface sans fil de transmisison de données dans un environnement réaliste in vivo avec positionement libre. Un émetteur-récepteur full-duplex (FDT) entièrement intégré qui se caractérise par sa faible puissance est conçu pour réaliser une interfaces bi-directionnelles (stimulation et enregistrement) avec des débits asymétriques: des taux de tramnsmission plus élevés sont nécessaires pour l’enregistrement électrophysiologique multicanal (signaux de liaison montante) alors que les taux moins élevés sont utilisés pour la stimulation (les signaux de liaison descendante). L’émetteur (TX) et le récepteur (RX) se partagent une seule antenne afin de réduire la taille de l’implant. L’émetteur utilise la radio ultra-large bande par impulsions (IR-UWB) basée sur l’approche edge combining et le RX utilise la bande ISM (Industrielle, Scientifique et Médicale) de fréquence central 2.4 GHz et la modulation on-off-keying (OOK). Une bonne isolation (> 20 dB) est obtenue entre le TX et le RX grâce à 1) la mise en forme les impulsions émises dans le spectre UWB non réglementée (3.1-7 GHz), et 2) le filtrage espace-efficace (évitant l’utilisation d’un circulateur ou d’un diplexeur) du spectre du lien de communication descendant directement au niveau de l’ amplificateur à faible bruit (LNA). L’émetteur UWB 3.1-7 GHz utilise un e modultion OOK ainsi qu’une modulation par déplacement de phase (BPSK) à seulement 10.8 pJ / bits. Le FDT proposé permet d’atteindre 500 Mbps de débit de données en lien montant et 100 Mbps de débit de données de lien descendant. Il est entièrement intégré dans un procédé TSMC CMOS 0.18 um standard et possède une taille totale de 0.8 mm2. La consommation totale d’énergie mesurée est de 10.4 mW (5 mW pour RX et 5.4 mW pour TX au taux de 500 Mbps).In recent years, there has been major progress on implantable biomedical systems that support most of the functionalities of wireless implantable devices. Nevertheless, these devices remain mostly restricted to be commercialized, in part due to weakness of a straightforward design to support the required functionalities, limitation on miniaturization, and lack of a reliable low-power high data rate interface between implants and external devices. This research provides novel strategies on the design of implantable biomedical devices that addresses these limitations by presenting analysis and techniques for wireless power transfer and efficient data transfer. The first part of this research includes our proposed novel resonance-based multicoil inductive power link structure with uniform power distribution to wirelessly power up smart animal research systems and implanted medical devices with high power efficiency and free positioning capability. The proposed structure consists of a multicoil resonance inductive link, which primary resonator array is made of several identical resonators enclosed in a scalable array of overlapping square coils that are connected in parallel and arranged in power surface (2D) and power chamber (3D) configurations. The proposed chamber uses two arrays of primary resonators, facing each other, and connected in parallel to achieve uniform power distribution in 3D. Each surface includes 9 overlapped coils connected in parallel and implemented into two layers of FR4 printed circuit board. The chamber features a natural power localization mechanism, which simplifies its implementation and eases its operation by avoiding the need for active detection of the load location and power control mechanisms. A single power surface based on the proposed approach can provide a power transfer efficiency (PTE) of 69% and a power delivered to the load (PDL) of 120 mW, for a separation distance of 4 cm, whereas the complete chamber prototype provides a uniform PTE of 59% and a PDL of 100 mW in 3D, everywhere inside the chamber with a chamber size of 27×27×16 cm3. The second part of this research includes our proposed novel, fully-integrated, low-power fullduplex transceiver (FDT) to support bi-directional neural interfacing applications (stimulating and recording) with asymmetric data rates: higher rates are required for recording (uplink signals) than stimulation (downlink signals). The transmitter (TX) and receiver (RX) share a single antenna to reduce implant size. The TX uses impulse radio ultra-wide band (IR-UWB) based on an edge combining approach, and the RX uses a novel 2.4-GHz on-off keying (OOK) receiver. Proper isolation (> 20 dB) between the TX and RX path is implemented 1) by shaping the transmitted pulses to fall within the unregulated UWB spectrum (3.1-7 GHz), and 2) by space-efficient filtering (avoiding a circulator or diplexer) of the downlink OOK spectrum in the RX low-noise amplifier (LNA). The UWB 3.1-7 GHz transmitter using OOK and binary phase shift keying (BPSK) modulations at only 10.8 pJ/bit. The proposed FDT provides dual band 500 Mbps TX uplink data rate and 100 Mbps RX downlink data rate. It is fully integrated on standard TSMC 0.18 nm CMOS within a total size of 0.8 mm2. The total power consumption measured 10.4 mW (5 mW for RX and 5.4 mW for TX at the rate of 500 Mbps)

Development and Experimental Analysis of Wireless High Accuracy Ultra-Wideband Localization Systems for Indoor Medical Applications

This dissertation addresses several interesting and relevant problems in the field of wireless technologies applied to medical applications and specifically problems related to ultra-wideband high accuracy localization for use in the operating room. This research is cross disciplinary in nature and fundamentally builds upon microwave engineering, software engineering, systems engineering, and biomedical engineering. A good portion of this work has been published in peer reviewed microwave engineering and biomedical engineering conferences and journals. Wireless technologies in medicine are discussed with focus on ultra-wideband positioning in orthopedic surgical navigation. Characterization of the operating room as a medium for ultra-wideband signal transmission helps define system design requirements. A discussion of the first generation positioning system provides a context for understanding the overall system architecture of the second generation ultra-wideband positioning system outlined in this dissertation. A system-level simulation framework provides a method for rapid prototyping of ultra-wideband positioning systems which takes into account all facets of the system (analog, digital, channel, experimental setup). This provides a robust framework for optimizing overall system design in realistic propagation environments. A practical approach is taken to outline the development of the second generation ultra-wideband positioning system which includes an integrated tag design and real-time dynamic tracking of multiple tags. The tag and receiver designs are outlined as well as receiver-side digital signal processing, system-level design support for multi-tag tracking, and potential error sources observed in dynamic experiments including phase center error, clock jitter and drift, and geometric position dilution of precision. An experimental analysis of the multi-tag positioning system provides insight into overall system performance including the main sources of error. A five base station experiment shows the potential of redundant base stations in improving overall dynamic accuracy. Finally, the system performance in low signal-to-noise ratio and non-line-of-sight environments is analyzed by focusing on receiver-side digitally-implemented ranging algorithms including leading-edge detection and peak detection. These technologies are aimed at use in next-generation medical systems with many applications including surgical navigation, wireless telemetry, medical asset tracking, and in vivo wireless sensors