Low-power FM transmitter for use in neural recording applications

Journal ArticleWe present a low power FM transmitter for use in neural recording telemetry. The transmitter consists of a low noise biopotential amplifier and a voltage controlled oscillator used to transmit the amplified neural signals at a frequency of 433 MHz. The circuit is powered through a transcutaneous, inductive link. The power consumption of the transmitter is measured to be 465 μW. Using a 1/8-wavelength monopole antenna, a received power level was measured to be -54.5 dBm at a distance of one meter

Micropower circuits for bidirectional wireless telemetry in neural recording applications

Journal ArticleState-of-the art neural recording systems require electronics allowing for transcutaneous, bidirectional data transfer. As these circuits will be implanted near the brain, they must be small and low power. We have developed micropower integrated circuits for recovering clock and data signals over a transcutaneous power link. The data recovery circuit produces a digital data signal from an ac power waveform that has been amplitude modulated. We have also developed an FM transmitter with the lowest power dissipation reported for biosignal telemetry. The FM transmitter consists of a low-noise biopotential amplifier and a voltage controlled oscillator used to transmit amplified neural signals at a frequency near 433 MHz. All circuits were fabricated in a standard 0.5- m CMOS VLSI process. The resulting chip is powered through a wireless inductive link. The power consumption of the clock and data recovery circuits is measured to be 129 W; the power consumption of the transmitter is measured to be 465 W when using an external surface mount inductor. Using a parasitic antenna less than 2 mm long, a received power level was measured to be 59 73 dBmat a distance of one meter

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

Design of Wireless Power Transfer and Data Telemetry System for Biomedical Applications

With the advancement of biomedical instrumentation technologies sensor based remote healthcare monitoring system is gaining more attention day by day. In this system wearable and implantable sensors are placed outside or inside of the human body. Certain sensors are needed to be placed inside the human body to acquire the information on the vital physiological phenomena such as glucose, lactate, pH, oxygen, etc. These implantable sensors have associated circuits for sensor signal processing and data transmission. Powering the circuit is always a crucial design issue. Batteries cannot be used in implantable sensors which can come in contact with the blood resulting in serious health risks. An alternate approach is to supply power wirelessly for tether-less and battery- less operation of the circuits.Inductive power transfer is the most common method of wireless power transfer to the implantable sensors. For good inductive coupling, the inductors should have high inductance and high quality factor. But the physical dimensions of the implanted inductors cannot be large due to a number of biomedical constraints. Therefore, there is a need for small sized and high inductance, high quality factor inductors for implantable sensor applications. In this work, design of a multi-spiral solenoidal printed circuit board (PCB) inductor for biomedical application is presented. The targeted frequency for power transfer is 13.56 MHz which is within the license-free industrial, scientific and medical (ISM) band. A figure of merit based optimization technique has been utilized to optimize the PCB inductors. Similar principal is applied to design on-chip inductor which could be a potential solution for further miniaturization of the implantable system. For layered human tissue the optimum frequency of power transfer is 1 GHz for smaller coil size. For this reason, design and optimization of multi-spiral solenoidal integrated inductors for 1 GHz frequency is proposed. Finally, it is demonstrated that the proposed inductors exhibit a better overall performance in comparison with the conventional inductors for biomedical applications

Master of Science

thesisFully integrated, implantable, and wireless neural interface systems typically re-quire a forward data link in addition to the telemetry link that transmits data from the chip. One popular way to create this forward data link is to amplitude modulate the magnetic fi eld of the inductive link that provides the device with wireless power. However, the limitations of these channels when loaded with a recti fier and amplitude modulated have not previously been characterized, and this lack of understanding caused previous versions of the Integrated Neural Interface (INI) to have forward data communication issues, which needed to be corrected for the next generation of the device, INIR8. This thesis first develops an analytical method of characterizing this sort of wireless channel. It then shows measurement data that verifies the validity of the model in the desired region of operation. The available bandwidth as determined by this analytical method, and confirmed by simulation, is insufficient for many applications. Therefore, the next subject of this thesis is to increase the data rate beyond what the bandwidth of the system can intrinsically support by using an equalization technique. This technique is shown to support very robust data recovery under a variety of operating conditions and to data rates much higher than otherwise possible. Another way to improve the reliability of data recovery is to develop a robust digital control system with error detection capabilities. This was done for INIR8, and works very reliably. The end result of this eff ort is a very robust forward data communication in INIR8, as well as a new analytical method for characterizing inductively coupled channels with certain loads and modulation techniques

Inductively Coupled CMOS Power Receiver For Embedded Microsensors

Inductively coupled power transfer can extend the lifetime of embedded microsensors that save costs, energy, and lives. To expand the microsensors' functionality, the transferred power needs to be maximized. Plus, the power receiver needs to handle wide coupling variations in real applications. Therefore, the objective of this research is to design a power receiver that outputs the highest power for the widest coupling range. This research proposes a switched resonant half-bridge power stage that adjusts both energy transfer frequency and duration so the output power is maximally high. A maximum power point (MPP) theory is also developed to predict the optimal settings of the power stage with 98.6% accuracy. Finally, this research addresses the system integration challenges such as synchronization and over-voltage protection. The fabricated self-synchronized prototype outputs up to 89% of the available power across 0.067%~7.9% coupling range. The output power (in percentage of available power) and coupling range are 1.3× and 13× higher than the comparable state of the arts.Ph.D

Remote Powering and Communication of Implantable Biosensors Through Inductive Link

Nowadays there is an increasing interest in the field of implantable biosensors. The possibility of real-time monitoring of the human body from inside paves the way to a large number of applications and offers wide opportunities for the future. Within this scenario, the i-IronIC project aims to develop an implantable, low cost, health-care device for real-time monitoring of human metabolites. The contribution of this research work to the i-IronIC project consists of the design and realization of a complete platform to provide power, data communication and remote control to the implantable biosensor. High wearability of the transmitting unit, low invasivity of the implanted electronics, integration of the power management module within the sensor, and a reliable communication protocol with portable devices are the key points of this platform. The power is transmitted to the implanted sensor by exploiting an inductive link. Simulations have been performed to check the effects of several variables on the link performance. These simulations have finally confirmed the possibility to operate in the low megahertz range, where tissue absorption is minimum, even if a miniaturized receiving inductor is used. A wearable patch has been designed to transmit power through the body tissues by driving an external inductor. The same inductive link is used to achieve bidirectional data communication with the implanted device. The patch, named IronIC, is powered by lithium-ion polymer batteries and can be remotely controlled by means of a dedicated Android application running on smartphones and tablets. Long-range communication between the patch and portable devices is performed by means of Bluetooth protocol. Different typologies of receiving inductors have been designed to minimize the size of the implantable device and reduce the discomfort of the patience. Multi-layer, printed spiral inductors and microfabricated spiral inductors have been designed, fabricated and tested. Both the approaches involve a sensibly smaller size, as compared to classic “pancake” inductors used for remote powering. Furthermore, the second solution enables the realization of the receiving inductor directly on the silicon substrate hosting the sensor, thus involving a further miniaturization of the implanted device. An integrated power module has been designed and fabricated in 0.18 μm CMOS technology to perform power management and data communication with the external patch. The circuit, to be merged with the sensor readout circuit, consists of an half-wave voltage rectifier, a low-dropout regulator, an amplitude demodulator and a load modulator. The module receives the power from the implanted inductor and provides a stable voltage to the sensor readout circuit. Finally, the amplitude demodulator and the load modulator enable short-range communication with the patch

Asservissement de l'énergie inductive transmise aux implants électroniques

RÉSUMÉ Ce mémoire concerne le domaine d’alimentation énergétique des implants médicaux électroniques (IME). L’alimentation des IME par couplage inductif a toujours été appréciée pour sa biocompatibilité et sa capacité à transmettre une quantité d’énergie suffisante aux implants électroniques. Bien que cette méthode fût introduite il y a longtemps, plusieurs défis restent à relever. Le défi majeur est la sensibilité de l’efficacité du transfert d’énergie à la variation de certains paramètres du lien comme le facteur de couplage entre les bobines, la charge du côté récepteur et l’inductance des bobines. Une variation de l’un de ces paramètres est en mesure d’altérer la fréquence de résonance primaire et réduire en conséquence la quantité d’énergie transférée vers l’IME. Dans ce contexte, nous présentons une nouvelle technique pour compenser la variation des paramètres du lien inductif. Elle permet de maintenir l’état de résonance dans le transmetteur et d’assurer une meilleure transmission d’énergie en dépit de ces variations. Un transmetteur d’énergie inductive asservi est alors proposé. Ce système est transportable et est alimenté par des batteries rechargeables. Il est composé d’un transmetteur d’énergie inductive classique et d’une boucle d’asservissement. Le transmetteur classique émet un champ inductif (ou champ magnétique alternatif) grâce à un oscillateur à quartz, un amplificateur de puissance (AP) de classe E et un circuit résonant primaire constitué d’un condensateur et d’une bobine d’émission. La boucle d’asservissement, quant à elle, sert à compenser les variations des paramètres du lien capables d’altérer la fréquence de résonance du circuit primaire. La boucle comporte principalement un bloc de détection de la tension aux bornes de la bobine d’émission (image de la puissance à transférer vers l’IME) et un micro moteur pas-à-pas à haute résolution qui agit sur le condensateur de résonance primaire et indirectement sur la fréquence de résonance. Le système proposé utilise une fréquence de fonctionnement de 13,56 MHz réservée aux applications industrielles, scientifiques et médicales (ISM).----------ABSTRACT This Master thesis deals with energy transfer systems dedicated to electronic medical implants (EMI). Powering EMIs by inductive link has always been prized for its biocompatibility and ability to transmit appropriate energy to electronic implants. Although this method was introduced a long time ago, several challenges still remain. The main challenge is the sensitivity of the energy transfer efficiency to the variation of some link parameters, such as the coupling factor between the coils, the load on the receiver side, and the coils inductances. A variation of any of these parameters is able to alter the primary resonant frequency and consequently reduce the amount of energy transferred to the EMI. In this context, we present a new method to compensate for variations of the inductive link parameters. This method maintains the resonant state in the transmitter and therefore ensures better energy transmission despite these variations. A controlled inductive power transmitter is then proposed. This system is portable and is powered by rechargeable batteries. It is composed of a conventional inductive energy transmitter and a feedback loop. The conventional transmitter emits an inductive field (or AC magnetic field) using a crystal oscillator, a class E power amplifier (PA) and a resonant primary circuit. The control loop is in turn used to compensate for the variations of the link parameters which are able to alter the resonant frequency of the primary circuit. The loop includes mainly a primary coil voltage detector (for sensing the power transferred to the EMI) and a high resolution micro stepper motor which controls the resonant capacitor and indirectly the primary resonance frequency. The proposed system uses an operating frequency of 13.56 MHz reserved for industrial, scientific and medical (ISM) applications. This frequency offers as well a good compromise between compatibility with the biological environment and the transmission range. Given that the proposed system is located outside the human body and that the class E amplifier generates a fairly high power, the prototype was performed on a printed circuit board using commercial discrete components