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Micropower Circuits for Bidirectional Wireless Telemetry in Neural Recording Applications
Abstract
State-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-μm 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 μW; the power consumption of the transmitter is measured to be 465 μW 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 dBm at a distance of one meter.
... Since first discovered by Nikola Tesla in 1914 [1], and subsequently reported by Heinrich Hertz and Oliver Lodge [2], Wireless Power Transfer (WPT) has become a focal point of numerous research interests and an alternative power transmission mechanism in mobile computing [3], [4], wireless charging of biomedical body implants [5]- [7] and Electric Vehicle (EV) [8]. This breakthrough in WPT research can be attributed to improved performance of power electronic components and the discovery of wide band gap power semiconductors, capable of operating at high switching frequencies with minimal losses [4]. ...
... Since first discovered by Nikola Tesla in 1914 [1], and subsequently reported by Heinrich Hertz and Oliver Lodge [2], Wireless Power Transfer (WPT) has become a focal point of numerous research interests and an alternative power transmission mechanism in mobile computing [3], [4], wireless charging of biomedical body implants [5]- [7] and Electric Vehicle (EV) [8]. This breakthrough in WPT research can be attributed to improved performance of power electronic components and the discovery of wide band gap power semiconductors, capable of operating at high switching frequencies with minimal losses [4]. As part of the development in wireless charging technology, frantic ...
With increasing penetration of wireless charging technologies comes an ever-rising demand for wireless power transfer (WPT) structures that demonstrate high power transfer and power transfer efficiency (PTE), especially over wide transfer distance. The concern with reliability in adopting wireless charging technologies in consumer and industrial applications (including mobile chargers and dynamic
wireless charging of electric vehicles, EVs) stems from fluctuating output power and low power transfer efficiency (PTE). Moreover, the inherently high resonant frequency of existing metamaterial (MM)- based WPT designs imposes a high switching stress on power semiconductors and passive components, resulting in high power dissipation, especially in high power applications. This manuscript presents a critical survey of recent studies and developments in MM-based WPT systems. First, the fundamental
concepts and classification of WPT technologies based on magnetic resonant coupling (MRC), inductive coupling etc. are discussed. Going forward, key MM design considerations, including resonance operating frequencies, effective permittivity (ϵr), effective permeability (µr), numerical modeling, equivalent circuit representations, and 3D fabrication technologies are widely analyzed and critiqued. Additionally, the
performance enhancing effect of integrating different MM designs with existing WPT systems are explicitly discussed. Finally, the technical challenges associated with the resonant operating frequencies of MM, miniaturization of MM design footprint, and 3D prototyping are investigated while also presenting potential
... Since first discovered by Nikola Tesla in 1914 [1], and subsequently reported by Heinrich Hertz and Oliver Lodge [2], Wireless Power Transfer (WPT) has become a focal point of numerous research interests and an alternative power transmission mechanism in mobile computing [3], [4], wireless charging of biomedical body implants [5]- [7] and Electric Vehicle (EV) [8]. This breakthrough in WPT research can be attributed to improved performance of power electronic components and the discovery of wide band gap power semiconductors, capable of operating at high switching frequencies with minimal losses [4]. ...
... Since first discovered by Nikola Tesla in 1914 [1], and subsequently reported by Heinrich Hertz and Oliver Lodge [2], Wireless Power Transfer (WPT) has become a focal point of numerous research interests and an alternative power transmission mechanism in mobile computing [3], [4], wireless charging of biomedical body implants [5]- [7] and Electric Vehicle (EV) [8]. This breakthrough in WPT research can be attributed to improved performance of power electronic components and the discovery of wide band gap power semiconductors, capable of operating at high switching frequencies with minimal losses [4]. As part of the development in wireless charging technology, frantic ...
With increasing penetration of wireless charging technologies comes an ever-rising demand for wireless power transfer (WPT) structures that demonstrate high power transfer and power transfer efficiency (PTE), especially over wide transfer distance. The concern with reliability in adopting wireless charging technologies in consumer and industrial applications (including mobile chargers and dynamic wireless charging of electric vehicles, EVs) stems from fluctuating output power and low power transfer efficiency (PTE). Moreover, the inherently high resonant frequency of existing metamaterial (MM)-based WPT designs imposes a high switching stress on power semiconductors and passive components, resulting in high power dissipation, especially in high power applications. This manuscript presents a critical survey of recent studies and developments in MM-based WPT systems. First, the fundamental concepts and classification of WPT technologies based on magnetic resonant coupling (MRC), inductive coupling etc. are discussed. Going forward, key MM design considerations, including resonance operating frequencies, effective permittivity (
), effective permeability (
), numerical modeling, equivalent circuit representations, and 3D fabrication technologies are widely analyzed and critiqued. Additionally, the performance enhancing effect of integrating different MM designs with existing WPT systems are explicitly discussed. Finally, the technical challenges associated with the resonant operating frequencies of MM, miniaturization of MM design footprint, and 3D prototyping are investigated while also presenting potential solutions.
... Neihart and Harrison [9] have spoken about the neural chronicle frameworks that need gadgets considering bidirectional information move. These gadgets should be little and low power as they are placed near to the cerebrum. ...
... These gadgets should be little and low power as they are placed near to the cerebrum. Utilizing a parasitic radio wire under 2 mm long, a power level was estimated to be 59.73 dB m away off of one meter [9]. Kevric and Subasi [10] explain about three popular signal processing techniques (empirical mode decomposition, discrete wavelet transforms, and wavelet packet decomposition) were analyzed for the decomposition of electroencephalography (EEG) signals in the BCI system for a classification task. ...
p>Real-time brain internet of thing (IoT) frameworks are expensive. But, creating a cheaper framework has been quickened incredibly by the superior investigation that's being done on virtual brain. The passing of an imperative individual on a mystery mission is considered delicate data and must be taken care of with as much security as conceivable. By guaranteeing this discreteness, the time taken for the message of their passing to reach the pertinent specialist is expanded to up to a few days. The time taken to provide the message is as well. These days, the advancements in equipment expanding the capacities of the virtual brain and of the wearable brain IoT sensors have made the advancement of various unused program systems conceivable for engineers to make valuable applications that combine the human brain with IoT. Different tactile pathways are too empowered for communications of the human brain with bigger measured data. The fundamental point of this extend is to transfer secret records onto the clouds safely.</p
... Fig. 12 (b), (c), and (d) present far-field EM links and inductive links used to obtain bidirectional data transmission and power transfer. In Fig. 12 (b), they transmit simple command data and power from an external device to implanted devices, and the implanted device sends sensor data to the external devices using an RF link [113], [210]. In Fig. 12 (c), the inductive coupling transmits only power, and data is passed through the RF link [211], [212]. ...
... Recent trends were also introduced, concerning transmission range and misalignment issues with the maximum PTE in free space. To extend the transmission range, self-resonant coupling, relay, and DCRS can be applied, and misalignment error can be compensated by robust structures, using arrays or metamaterials, while electrical [208], [209], (b) inductive coupling (power, uplink), high frequency (downlink) [112], [210], (c) inductive coupling (power), high frequency (uplink, downlink) [211], [212], (d) three carrier signal: inductive coupling -low frequency (power), inductive coupling -medium frequency (downlink), high frequency (uplink) [213]. parameter tuning can be utilized for impedance matching. ...
Near-field magnetic wireless systems have distinct advantages over their conventional far-field counterparts in water-rich environments, such as underwater, underground, and in biological tissues, due to lower power absorption. This paper presents a comprehensive review of near-field magnetic wireless power transfer (WPT) and communication technologies in a variety of applications from general free-space systems, to implantable biomedical devices we find of particular interest. To implement a fully wirelessly-powered implantable system, both high-efficiency power transfer and high-rate data communication are essential. This paper first presents the history and the fundamentals of near-field WPT and communication in free-space systems, followed by technical details for their specific use in implantable biomedical devices. Finally, this paper reviews recent advances in simultaneous wireless information and power transfer (SWIPT) and highlights their applications in implantable biomedical systems. The knowledge reviewed in the paper could provide intuition in the design of various wireless and mobile systems such as wireless body area networks, small-cell 5G cellular, as well as in-body biomedical applications, especially for efficient power and data management and higher security.
... Implantable Medical Devices (IMDs) have dramatically advanced and improved healthcare systems in recent decades. IMDs are widely used in remote patient monitoring applications, such as capsule endoscopy [1], retinal prostheses [2], neural recording [3], glucose monitoring [4], etc. As shown in Fig.1, to enable wireless communication between these devices and external equipment to the human body without direct physical contact, a robust implantable antenna is required. ...
... As a result, healthcare offices and hospitals are required to have advanced equipment to be able to handle the increasing number of requirements of patients [1]. The integrated circuit (IC) technology used within biomedical implants is growing exponentially [2][3][4]. From another perspective, Internet of Things (IoT) systems will be fruitful in emerging applications that are based on radio frequency (RF) designs. IoT systems include computer, Internet, and mobile communication technologies [5]. ...
Continuous monitoring and treatment of various diseases with biomedical technologies and wearable electronics has become significantly important. The healthcare area is an important, evolving field that, among other things, requires electronic and micro-electromechanical technologies. Designed circuits and smart devices can lead to reduced hospitalization time and hospitals equipped with high-quality equipment. Some of these devices can also be implanted inside the body. Recently, various implanted electronic devices for monitoring and diagnosing diseases have been presented. These instruments require communication links through wireless technologies. In the transmitters of these devices, power amplifiers are the most important components and their performance plays important roles. This paper is devoted to collecting and providing a comprehensive review on the various designed implanted amplifiers for advanced biomedical applications. The reported amplifiers vary with respect to the class/type of amplifier, implemented CMOS technology, frequency band, output power, and the overall efficiency of the designs. The purpose of the authors is to provide a general view of the available solutions, and any researcher can obtain suitable circuit designs that can be selected for their problem by reading this survey.
... Conventional wireless power transfer methods for implants utilize coils for inductive coupling [8][9][10][11][12][13]. This has been implemented for the charging function in several FDAapproved neurostimulators. ...
A resonator coupler for subcutaneous implants has been developed with a new impedance matching pattern added to the conventional loop antenna. The tuning element of a concentric metal pad contributes distributed capacitance and inductance to the planar inductive loop and improves resonance significantly. It provides a better qualify factor for resonant coupling and a much lower reflection coefficient for the implant electronics. Practical constraints are taken into account for designs including the requirement of operation within a regulated frequency band and the limited thickness for a monolithic implant. In this work, two designs targeting to operate in the two industrial, scientific, and medical (ISM) bands at 903 MHz and 2.45 GHz are considered. The tuning metal pad improves their resonances significantly, compared to the conventional loop designs. Since it is difficult to tune the implant antenna after implantation, the effects of tissue depth variations due to the individual’s surgery and the appropriate implant depths are investigated. Simulations conducted with the dielectric properties of human skin documented in the literature are compared to measurements done with hydrated ground pork as phantoms. Experiments and simulations are conducted to explain the discrepancies in frequency shifts due to the uses of pork phantoms. The design method is thus validated for uses on human skin. A noninvasive localization method to identify the implant under the skin has been examined and demonstrated by both simulations and measurements. It can efficiently locate the subcutaneous implant based on the high quality-factor resonance owing to the tuning elements in both implant and transmitter couplers. The planar resonant coupler for wireless power transfer shows good performance and promise in subcutaneous applications for implants.
... For short term experimentation it is quite possible for sufficient transcutaneous power to be provided, a good example of this being in the three-month implantation testing of the Utah Array [69]. For long-term implantation however power needs can vary considerably [70,71]. ...
The subject of wireless power has been of great fascination since antiquity. First proposed in modern times by Nikola Tesla, it has intrigued and challenged the academic world. While there have been many attempts to describe this work, the mathematical explanation of wireless power can be traced to J. Clerk Maxwell’s original equations and the behavior of wireless power in the circuit is due to Joseph Larmor’s fundamental works on the dynamics of the field concept. Once you experience the unlimited nature of wireless power, it captures your imagination. One can build devices big and small at a range of frequencies, from small implants to industrial and robotic applications.
... In order to be able to extend the battery life of the external unit and relax the RF transmission efficiency, one must master the low power design [10]. In paper [32], a total power consumption less than 1 mW was reported for the internal unit. Most current systems use discrete components to achieve the back telemetry power supply. ...
The present paper discusses the climatic effects of humidity and temperature on cochlear implant functioning and the quality of the electrical sound signal. MATLAB Simulink simulations were prepared, offering insights into signal behavior under such climatic parameter changes. A simulation setup of the cochlear implant was developed, where a source type selection was used to change between a voice recording and a “chirp” sound. In addition, a DC blocking filter was applied to the input signal. A simulation code, with the application of the climatic influence via the air attenuation function, was developed. Thereby, the attenuation of temperature and humidity in the sound atmospheric circulation of the input signal, at T = 0 °C and RH = 0% and at T = 36 °C and RH = 40% was graphically represented. The results of the electrical pulse generator for each of the eight channels, with the IIR filter, Gaussian noise, temperature variation, humidity influence, and control of denoise block activity, were thus obtained.
... High throughput and low dormancy investigation of mind information will require fast databases and programming interfaces agreeable to enormous scope diagram examination. [1]N. M. Neihart and R. R. Hasrrison IEEE Internet Computing, vol. ...
The confidential and secure information of the user’s death storage cannot reach to the particular person or it takes minimum a day or hours to back up all the messages and information. There is lack of time efficiency to reveal all the messages. Here introducing a new concept called BCI (Brain Computer Interface) which is used to connect the human brain and computer. Since it is a BCI technique it consists of both hardware and software. In hardware the major role plays by EEG (Electroenceplogram) sensor, it is to check whether the brain is active or not. On the software side, the cloud is created for storing the information. An individual who want to share the information to his/her favorite or particular person can type the message and save the information in the cloud with his/her mail id and phone number which an individual want to convey. The wearable sensor have to wear like a band, as it may not affect the human brain or human body since it has the low frequency range of 7Hz or below 7Hz. Once the individual is death the stored information in the cloud can sent to that registered mail id and phone number without any delay. The time efficiency is very fast.
... band. 1-5 Some common implantable devices that are already in use are: functional electrical stimulators (FES), 6 cochlear implant, 7 blood glucose monitor, 8 retinal implant, 9 pacemakers, 10 neural recording, 11 and body temperature monitoring. 12 The element used to send and receive the signals wirelessly from the body implantable device is known as implantable antenna. ...
A superstrate loaded body implantable microstrip patch antenna working on Medical Implant Communications Service (MICS) (402‐405 MHz) band for biotelemetry applications is proposed. A 0.64‐mm thick high‐dielectric material Rogers RO Duroid 3010 is used both as substrate and superstrate of dielectric constant 10.2. Shorting pin is used to make compact antenna with footprint of 13.3 × 14.6 mm². Appreciable bandwidth of 40% is covered by antenna with return loss of −30.95. In‐silico testing inside skin, brain and three layered tissue models is done to test functionality of antenna in homogeneous as well as inhomogeneous tissue environment. For validation of results the fabricated antenna is successfully tested inside in‐vitro solution of homogeneous skin mimicking liquid.
... The Fig. 3 shows the graphical representation of the frequency vs Neural dust side dimension (b) and the Ultrasonic power efficiency vs Operating frequency (a) here in the above graph shows clearly that electrical activity of neurons is most commonly measured by electrical potential across the cellular membrane 29,30,31,32,33,34 . Anyhow this method is not so widely useful because of the drawbacks such as implantable recordings, electrical activity, and the measurements which are taken outside the membrane cells 35,36,37,38,39,40 . ...
In the past few years many researches have been dedicated towards Neural dust sensor such as Deep Brain Simulation (DBS), Brain Machine interface (BMI), Ultrasonic backscattering system and so on. Mainly the Brain-Machine Interface is considered as the neural interface system that can be usable for a lifetime and to increase the life span of the sensor with the implementation of wireless electromagnetic neural interface. By implementing all this to detect the blood clot in human brain and to reduce the blood clot using ultrasonic waves and further other implementation in medical field. And, Neural Dust sensor is considered as the central nervous system of a particular system. This study aims to provide a review on usage of neural dust sensor in medical diagnosis.
... 4 Devices operating at radio frequency power higher than 10 mW are the only ones that can reach more than 80% rectification efficiency. 4 However, for applications such as bionic implants [5][6][7][8] or nanoscale sensors of weak low frequency signals that involve low power levels of several microwatts or less, Schottky devices exhibit low sensitivity (typically up to $4 mV/lW) 9 that reduces the rectification efficiency to values below 1% at submicrowatt levels. 4 Nanoscale magnetic tunnel junctions (MTJs) provide an alternate approach to achieve signal rectification of low power signals. ...
Rectification is an important stage in electronic circuits for any wireless radio frequency power transfer application. Currently, Schottky diodes are widely used as rectifiers; however, they are inefficient at low power levels of microwatts or less (providing maximum sensitivities around 4 mV/μW). Nanoscale magnetic tunnel junctions can serve as alternative rectifiers by utilizing the so-called spin-torque diode effect, demonstrating a much higher rectification sensitivity (200 mV/μW) compared to Schottky diodes. However, for this mechanism to work, the signal frequency must match the ferromagnetic resonance frequency, which typically lies in the gigahertz range. For signals in the megahertz range or lower, Schottky diodes remain the only option for rectification. Here, we demonstrate a mechanism based on thermally activated adiabatic stochastic resonance in magnetic tunnel junctions to produce low frequency (up to tens of megahertz) signal rectification at low input power (submicrowatt), with a sensitivity of up to 35 mV/μW—higher than state-of-the-art Schottky diode rectifiers at this frequency and power range. These findings suggest magnetic tunnel junctions as potential alternatives to Schottky diodes for low frequency and low power applications.
... 27 In the past years, researchers have been resorting to the ultralow power consumption integrated circuit (IC) technology to overcome these challenges. 16,28,29 Muller et al. 17 developed a 64-channel fully implantable wireless micro-ECoG array which incorporated a specially designed low power IC with microfabricated parylene electrodes. The IC, powered by an external inductive coil, was very promising and exhibited a low power consumption of 225 μW and a footprint of 2.4 mm × 2.4 mm. ...
Wireless implantable neural interfaces can record high-resolution neuropotentials without constraining patient movement. Existing wireless systems often require intracranial wires to connect implanted electrodes to an external head-stage or / and deploy application specific integrated circuit (ASIC), that is battery-powered or externally power-transferred, raising safety concerns such as infection, electronics failure, or heat-induced tissue damage. This work presents a biocompatible, flexible, implantable neural recorder capable of wireless acquisition of neuropotentials without wires, batteries, energy harvesting units, or active electronics. The recorder, fabricated on a thin polyimide substrate, features a small footprint of 9 mm x 8 mm x 0.3 mm, and is comprised of passive electronic components. The absence of active electronics on the device leads to near zero power consumption, inherently avoiding the catastrophic failure of active electronics. We performed both in-vitro validation in tissue-simulating phantom and in-vivo validation in an epileptic rat. The fully-passive wireless recorder was implanted under rat scalp to measure neuropotentials from its contact electrodes. The implanted wireless recorder demonstrated its capability to capture low voltage neuropotentials, including somatosensory evoked potentials (SSEP) and interictal epileptiform discharges (IED). Wirelessly recorded SSEP and IED signals were directly compared to those from wired electrodes to demonstrate the efficacy of the wireless data. In addition, a CNN (Convoluted Neural Network)-based machine learning algorithm successfully achieved IED signal recognition accuracy as high as 100% and 91% in wired and wireless IED data, respectively. These results strongly support the fully-passive wireless neural recorder’s capability to measure neuropotentials as low as tens of microvolts. With further improvement, the recorder system presented in this work may find wide applications in future brain machine interface (BMI) system.
... Implantable medical devices (IMDs) have increasingly caught the attention of the scientific community due to their wireless capabilities of detecting bio-medical information and transmitting health data much more flexibly and conveniently than traditional wired sensors placed exterior to the body [1][2][3]. These devices have been widely adopted in many applications including neural recording [4], glucose monitoring [5], and intracranial pressure monitoring [6], etc. ...
A novel miniaturized single-fed circularly-polarized (CP) microstrip patch antenna operating in the Industrial, Scientific, Medical (ISM) band of 2.40–2.48 GHz, is comprehensively proposed for implantable wireless communications. By employing reactive loading in the arrow-shaped slotted patch to form slow wave effect and embedding V-shaped slots into patch to lengthen the current path, the proposed implantable antenna is minimized with the overall dimensions of 9.2 mm × 9.2 mm × 1.27 mm. The radiation patterns of the proposed antenna illustrate the performance of left-handed circular polarization. The simulated results show that an impedance bandwidth of 7.2% (2.39–2.57 GHz) and an axial ratio bandwidth of 3.7% (2.39–2.48 GHz) at the ISM band are achieved, respectively. Ex vivo measured results are in good agreement with the corresponding simulated ones.
... Telemetry through noisy environments has traditionally deployed OOK modulation for its high signal-to-noise ratio [24]. However, implantable device applications from subcutaneous and further depths have been shown to present design challenges, for example, leading to data recovery on-chip [38] or a specialized nonlinear modulation protocol [39]. ...
We report a wireless energy harvesting and telemetry storage system in 180 nm CMOS technology, demonstrated in situ in rat carcass. The implantable device has dimensions 13 mm × 15 mm and stores 87.5 mJ, providing a self-powering time of 8.5 s transmitting through tissue. We utilize an all-solid-state flexible supercapacitor of breakdown voltage 0.8 V and capacitance 400 mF to harvest incoming wireless power, followed by a boost converter CMOS that drives an active wireless transmitter at 1.5 V at 2.4 GHz in the industrial, scientific, and medical (ISM) band. The DC/DC converter component and switching frequency selection were guided by genetic algorithm analysis and use digital feedback to control the pulse width modulation (PWM), which slowly modifies the duty cycle to control output voltage fluctuations. This implantable medical device system presents the roadmap for batteryless energy harvesting in vivo and in clinical environments, exhibiting the highest operating storage density of 450 μJ/mm² reported to date.
... Despite the fact that a wireless connection is not a requirement for physiological parameter monitoring with implanted sensors, the issue mentioned above is one of the main motivations for this trend to use wireless technology in modern biomedical implanted systems [7 Examples of physiological data collection platforms with wireless connectivity include a wide range of biomedical applications. Coosemans et al. [8], for example, have described a system for continuous wireless intracavitary pressure monitoring of the bladder, while other authors have assembled neural prosthetic devices [9][10]. ...
Computer systems and personal health
applications. There is a primary research area that makes a
difference in wireless sensor network (WSN) technologies to
improve the quality of life. The current development of WBAN
and IWBAN systems provides advantages and disadvantages
and a snapshot for future work. The role of WBAN technology
in the maintenance and quality care of WBAN technology is
described in the article because of the increasing population
density of the elderly, which is increasing day by day, without
needing sickness or diseases that cause chronic illnesses. The
article is an example of the latest technologies related to designs
such as reliability, scalability, energy efficiency and security, as
well as an analysis of the diversity and disadvantages of these
systems.
... It is difficult to implant an integrated circuit and battery due to size and biocompatibility issues. This means that the power needs to be supplied from outside the body, through inductive coupling or energy harvesting [2,3]. Another consideration is that even at moderate levels any heat generated may cause necrosis, hence the devices need to consume as little power as possible. ...
The performance requirement of an operational trans-conductance amplifier (OTA) for the high gain and low power neural recording frontend has been addressed in this paper. A novel split differential pair technique is proposed to improve the gain of the OTA without any additional bias current requirements. The design demonstrates a significant performance enhancement when compared to existing techniques, such as gain-boosting and recycling. A qualitative and quantitative treatment is presented to explore the impact of the split ratio on the performance parameters of gain, bandwidth, and linearity. A prototype implemented in TSMC 65 nm CMOS technology achieved 68 dB open loop-gain (13 dB higher than the conventional circuit) and a 17 kHz 3-dB bandwidth. A linearity of − 62 dB has been achieved with 7 mV pk–pk signal at the input. The circuit operates from a 1 V supply and draws 0.6 uA static current. The prototype occupies 3300 um² silicon area.
... Two methods have been proposed to transmit and receive electromagnetic signals between implantable and external devices at present. One method is employing the same coils to realize information transfer and WPT at the same frequency [18]- [20]. The biggest drawback of this method is a limited channel capacity due to its low frequency and high-Q coil, practically achievable data-rate is limited to 1-2 Mb/s [2], which may be a bottleneck for some applications. ...
This paper presents an ultracompact design of biomedical implantable devices with integrated wireless power transfer (WPT) and RF transmission capabilities for implantable medical applications. By reusing the spiral coil in an implantable device, both RF transmission and WPT are realized without the performance degradation of both functions in ultracompact size. The complete theory of WPT based on magnetic resonant coupling is discussed and the design methodology of an integrated structure is presented in detail, which can guide the design effectively. A system with an external power transmitter and implantable structure is fabricated to validate the proposed approach. The experimental results show that the implantable structure can receive power wirelessly at 39.86 MHz with power transfer efficiency of 47.2% and can also simultaneously radiate at 2.45 GHz with an impedance bandwidth of 10.8% and a gain of −15.71 dBi in the desired direction. Furthermore, sensitivity analyses are carried out with the help of experiment and simulation. The results reveal that the system has strong tolerance to the nonideal conditions. Additionally, the specific absorption rate distribution is evaluated in the light of strict IEEE standards. The results reveal that the implantable structure can receive up to 115 mW power from an external transmitter and radiate 6.4 dB·m of power safely.
... Further research carried out on neural recording systems particularly those that are non-electrical is not covered in this article. In addition, the reader can consult with other published work which provide detailed information on neural recording circuits and methodologies (Neihart and Harrison 2005, Kipke et al 2008, Fan et al 2011, Gosselin 2011, Kuan et al 2015, Ng et al 2016. ...
Objective:
Electrical brain stimulation provides therapeutic benefits for patients with drug-resistant neurological disorders. It, however, has restricted access to cell-type selectivity which limits its treatment effectiveness. Optogenetics, in contrast, enables precise targeting of a specific cell type which can address the issue with electrical brain stimulation. It, nonetheless, disregards real-time brain responses in delivering optimized stimulation to target cells. Closed-loop optogenetics, on the other hand, senses the difference between normal and abnormal states of the brain, and modulates stimulation parameters to achieve the desired stimulation outcome. Current review articles on closed-loop optogenetics have focused on its theoretical aspects and potential benefits. A review of the recent progress in miniaturized closed-loop optogenetic stimulation devices is thus needed.
Approach:
This paper presents a comprehensive study on the existing miniaturized closed-loop optogenetic stimulation devices and their internal components.
Main results:
Hardware components of closed-loop optogenetic stimulation devices including electrode, light-guiding mechanism, optical source, neural recorder, and optical stimulator are discussed. Next, software modules of closed-loop optogenetic stimulation devices including feature extraction, classification, control, and stimulation parameter modulation are described. Then, the existing devices are categorized into open-loop and closed-loop groups, and the combined operation of their neural recorder, optical stimulator, and control approach is discussed. Finally, the challenges in the design and implementation of closed-loop optogenetic stimulation devices are presented, suggestions on how to tackle these challenges are given, and future directions for closed-loop optogenetics are stated.
Significance:
A generic architecture for closed-loop optogenetic stimulation devices involving both hardware and software perspectives is devised. A comprehensive investigation into the most current miniaturized and tetherless closed-loop optogenetic stimulation devices is given. A detailed comparison of the closed-loop optogenetic stimulation devices is presented.
... For short term experimentation it is quite possible for sufficient transcutaneous power to be provided, a good example of this being in the 3 month implantation testing of the Utah Array [70]. For long-term implantation however power needs can vary considerably [71,72]. ...
The work involves investigation of a type of wireless power system wherein its analysis will yield the construction of a prototype modeled as a singular technological artifact. It is through exploration of the artifact that forms the intellectual basis for not only its prototypical forms, but suggestive of variant forms not yet discovered. Through the process it is greatly clarified the role of the artifact, its most suitable application given the constraints on the delivery problem, and optimization strategies to improve it. In order to improve maturity and contribute to a body of knowledge, this document proposes research utilizing mid-field region, efficient inductive-transfer for the purposes of removing wired connections and electrical contacts. While the description seems enough to state the purpose of this work, it does not convey the compromises of having to redraw the lines of demarcation between near and far-field in the traditional method of broadcasting. Two striking scenarios are addressed in this thesis: Firstly, the mathematical explanation of wireless power is due to J.C. Maxwell's original equations, secondly, the behavior of wireless power in the circuit is due to Joseph Larmor's fundamental works on the dynamics of the field concept. A model of propagation will be presented which matches observations in experiments. A modified model of the dipole will be presented to address the phenomena observed in the theory and experiments. Two distinct sets of experiments will test the concept of single and two coupled-modes. In a more esoteric context of the zero and first-order magnetic field, the suggestion of a third coupled-mode is presented. Through the remaking of wireless power in this context, it is the intention of the author to show the reader that those things lost to history, bound to a path of complete obscurity, are once again innovative and useful ideas.
In this paper, a miniaturized skin implantable biocompatible microstrip antenna is proposed for biotelemetry applications at 2.4–2.48 GHz. The volume of the antenna is 42.68 mm3 with dimensions 8.2 × 6.94 × 0.75 mm3. Rogers RO Duroid 3010 of 0.25 mm thickness is used for designing the proposed biocompatible antenna. This material is also used as a superstrate to cover the antenna from both sides to provide safety to patients. Further, specific absorption rate (SAR) is analyzed and found 552 W/Kg and 73.2 W/Kg for 1 g- and 10 g-averaged tissue, respectively, at an operating frequency of 2.45 GHz, which makes it biocompatible. An appreciable volume factor of 9371.8 is achieved with a good percentage bandwidth of 16.1%. In-silico, in-vitro and ex-vivo testing is performed for the proper validation of the proposed antenna. The antenna is found to be functional at ISM band, which makes it best suitable for implantable devices.
The use of magnetic metasurfaces in Wireless Power Transfer systems is becoming a popular research topic: they have proven to be a valid approach to increase the performances (in terms of power transfer) and improve the overall EMC properties in terms of field emissions. In this contribution, the authors investigate the susceptibility of such systems in case of an impinging Electromagnetic Interference (that might also be intentional), evaluating different parameters for a selected set of the system's components. In particular, the worst‐case scenarios of voltage peak, energy and sharpness (where appliable) at the transmitting and receiving ports and at each capacitor of the metasurface are calculated. The results obtained for a specific system practically implemented in the lab, show that the metasurface does not necessarily decreases susceptibility towards EMI and it can be itself the most critical component. The identification of the key and critical parameters allows us to provide an insight on how metamaterials used as shielding devices should be properly designed.
Background:
It is unclear whether neural response telemetric (NRT) thresholds are related to lexical tonal language performance after cochlear implants (CIs). We explored the factors associated with changes in NRT thresholds and postoperative performance of CI patients.
Methods:
Patients receiving Nucleus 24 CIs in our hospital from November 2010 were enrolled. We analyzed medical records and NRT thresholds. Mandarin speech and tone identification were measured in CI patients for at least 1 year postoperatively.
Results:
Seventy-two patients with an average age of 16.1 years received CIs. The postoperative NRT threshold was lower than the intraoperative threshold. The NRT threshold was higher in the early activation than the late activation group (mapping within 21 days vs. > 21 days postoperatively, respectively). Lower intraoperative NRT thresholds and curved electrodes were significantly associated with lower postoperative NRT thresholds. In multiple linear regression analysis, only postoperative NRT thresholds significantly affected speech and tone perception, including word recognition scores, tone perception, and comprehension of easy and difficult sentences (all p < 0.05). Other clinical parameters, including age, gender, implant type, and activation timing, were not significantly associated with clinical tone or speech outcomes.
Conclusion:
Curved electrode arrays were associated with lower postoperative NRT thresholds. A lower postoperative NRT threshold might predict better performance of Mandarin-speaking CI patients. Future studies should evaluate factors that affect both postoperative NRT thresholds and lexical tonal language performance.
The high level of corruptions, lack of trust, insincerity and the pervert mode of operation in the oil sector over a long period of time in the country has become worrisome that needs the high level of technology to alleviate this problem to a barest minimum. This paper presents an automatic transmission development and measures of the amount of petrol and other fractions of crude oil generated in a refinery each day to transmit the result to separate users using wireless technology. The machine combines a telemeter with a hall-effect flux sensor, which helps produce the output pulses in proportion to the fluid flow rates, in which fluids are transferred via sensor and rotor blades that are rotated in the generation of pulses. The sensor is then combined with the fluid line and pinwheel, the Hall Effect Sensor for output signals. The Peripheral Interface Controller (PIC) microcontroller is sent a signal from the flow sensor to a Global System for Mobile Communication (GSM) module that links the UART port to the mobile telephone. The data analyzed, converted were sent to Liquid Crystal Display (LCD) to show the flow rate and volume. The site technician or personnel at the base station could easily calculate the product entering the calibrated reservoir and receiving it as SMS. The report will allow the country's people who have access to GSM to know how much oil is generated in Nigeria in each day. After getting the value of fluid generated via SMS from the GSM module, the personnel at the base station then manually upload the data to the firm website; thus, everyone in the country can get access to the information. The website is built such that the different stations can upload their data if the admin gives them a password and user name. This will alleviate the levels of corruption, indecency, and crime in the oil sector. The device is approximately 98 percent reliable and cost-effective.
A typical battery charging process consists of a constant-current (CC) charging phase which is followed and completed by a constant-voltage charging phase. Moreover, replacing the CC charging by constant-power (CP) charging can eliminate thermal problems and enhance the cycle life of the battery. This work aims to maximize the system efficiency of a single-stage inductive power transfer (IPT) charger by minimizing the overall losses using a CP charging scheme. The single-stage CP IPT charger employs series-series compensation and adopts an active rectifier on the secondary side. Based on a time-domain model, the conditions of zero voltage switching (ZVS) and minimum circulating reactive power are derived. Then, the power losses in the magnetic coupler, inverter and active rectifier are analyzed and optimized under CP output condition. Combining the conditions of ZVS, minimum circulating reactive power, and minimum overall losses, we propose a novel optimal control strategy to maintain CP output and maximum efficiency throughout the charging process. In addition, the proportional integral controller is not needed. Finally, a 120-W experimental prototype is built to verify the performance of the proposed control strategy. Experimental results demonstrate high precision CP output and an efficiency of around 87.5
for the proposed single-stage inductive power transfer battery charger.
Real-time Brain IoT Systems are costly. But, developing a cheaper system has been accelerated greatly by the better research that is being done on Virtual Brain. The death of an important person on a secret mission is consider sensitive information and must be handled with as much security as possible. By ensuring this discreteness, the time taken for the message of their death to reach the relevant authority is increased to up to a few days. The time taken to deliver the message is too much. These days, the improvements in hardware increasing the abilities of the Virtual brain and of the wearable Brain IoT sensors have made the development of numerous new software frameworks possible for the developers to create useful applications that combine the human brain with IoT. Multiple sensory pathways are also enabled for communications of the human brain with larger sized data.The main aim of this project is to upload confidential documents onto the clouds securely as possible. Knowledge on how every individual thinks and recalls memory is found by the Virtual cerebrum undertaking. Both of the mentioned fields have been accelerated greatly in terms of development by these researches. This will in turn drive the need of an energy-efficient technology that supports the wider demands of the IoT. The brain activity extraction in IoT has been surveyed thoroughly in this project. This includes IoT models based on Electroencephalogram (EEG), machine learning and the current active platforms. The main findings of our survey highlights three major trends of development in the virtual brain development system, viz, IoT, EEGand cloud computing.Since the human body has a the low frequency range of 7Hz or below 7Hz, it cannot be detected by the EEG sensor. So, the wearable EEG sensor has a band that goes around the head. Once the individual is dead, the confidential information that is securely stored in the cloud can be sent to the mail id that was pre-registered by the user without any delay. This system is very time efficient.
In this article, we demonstrate the near electric field reduction ability of spiral resonators arrays (SRAs) in resonant inductive wireless power transfer (WPT) applications. In particular, we show that a suitably designed planar SRA, placed in the proximity of the driver loop, can significantly decrease the electric field level at the operative frequency, thus reducing the potentially dangerous radiation (i.e., the specific absorption rate) in the case of human exposure. In addition, due to the thin structure of the SRAs, the system is able to enhance the performance with respect to a conventional simple driver–receiver system for a fixed working distance. A systematic study has been performed through electromagnetic simulations to evaluate the optimum number of array unit cells to eventually achieve a compromise between efficiency enhancement and electric field shielding on a two-coil system, selected as a test case. Finally, the numerical results have been confirmed through measurements conducted on fabricated prototypes of the proposed WPT configurations. The introduced solution can be remarkably useful in all the WPT applications requiring a close interaction with human operators where exposure is a concern, such as automotive applications, biomedical implants, and rechargeable devices.
In this paper, the design of a simple rectangular ring slot, co-planar waveguide (CPW) fed, implantable antenna is proposed. By corner perturbation and the introduction of metallic patterns on the superstrate of the antenna, circular polarization (CP) has been achieved. The 10 mm × 10 mm × 0.4 mm dimensions have made the antenna compact and suitable for implantable biomedical application around 2.45 GHz industrial, scientific, and medical (ISM) band. Measurement setup comprising pork slab has been established and the in-vitro analysis of the antenna prototype is carried out by inserting the prototype into it. An axial ratio bandwidth of 10.6% has been achieved for the proposed simple implantable CP antenna.
In this article, we introduce a novel array-based system for inductive wireless power transfer (WPT) applications and a procedure for its design, which can be interpreted as a generalization of the traditional three-coil systems where the intermediate passive resonant coil (i.e., the transmitter) is replaced with an array of nonresonant concentric loops. We demonstrate that the new WPT array system provides flexibility with respect to the characteristic parameters of the inductive link (i.e., efficiency and gain), thus allowing for their optimal tradeoff depending on the specific WPT application: this is achieved by controlling the current amplitude flowing in each element of the array through the addition of an appropriately selected reactive load. Furthermore, we demonstrate that it is possible to obtain, with the WPT array, focused magnetic field distributions, leading to a potential reduction in the receiver dimensions. Such configuration can be made effectively equivalent to a traditional three-coil system in terms of physical dimensions and performance, through the addition of an appropriate reactance to each loop of the array. To demonstrate the validity and usefulness of the proposed system and design procedure, we first performed extensive numerical simulations of a traditional three-coil system and compared its performance with different array configurations. We then fabricated and experimentally characterized several prototypes, observing an excellent agreement between the measurements and simulations. The innovative features of the proposed design can be extremely useful in many WPT applications requiring a fine optimization in efficiency, gain, and field distribution.
We present a compact, magnetically dispersive engineered surface for resonant inductive Wireless Power Transfer (WPT) that significantly enhances the performance of an inductive link, increasing the efficiency and/or working distance. The proposed metasurface measures 6 cm × 6 cm × 0.1 cm, achieving a greatly reduced thickness over a 3D metamaterial, especially relative to the long wavelength at the chosen operating frequency of 5.77 MHz, which is in the range of typical wireless biomedical implants. Such feature is obtained by virtue of an extremely compact connected double-spiral unit cell, which provides high inductance values despite the small size. We prove through numerical simulations that the proposed metasurface considerably lowers the electric field level with respect to traditional 2 or 3-coil WPT systems, while maintaining the same magnetic field level at the receiver. In addition, we conducted efficiency measurements on a fabricated prototype, confirming the performance of our design. The excellent efficiency enhancement, combined with the resulting low electric field, makes the proposed metasurface an attractive solution for a number of WPT applications, especially where the exposure in terms of Specific Absorption Rate (i.e. SAR) is one of the major concerns, such as in biomedical implants and rechargeable devices.
In this paper the design of a simple rectangular ring slot, co-planar waveguide (CPW) fed, implantable antenna is proposed. By corner perturbation and the introduction of metallic patterns on the superstrate of the antenna, circular polarization (CP) has been achieved. The 10 mm × 10 mm × 0.4 mm dimensions have made the antenna compact and suitable for implantable biomedical application around 2.45 GHz Industrial, Scientific and Medical (ISM) band. Measurement setup comprising of pork slab has been established and the in-vitro analysis of the antenna prototype is carried out by inserting the prototype into it. An axial ratio bandwidth of 10.6% has been achieved for the proposed simple implantable CP antenna.
The brain–machine interface (BMI) is a new area of research and it is still in the development stage. The key component for the brain–machine interface is internal and external antennas. In this paper, we propose an implantable antenna for wireless brain signal sensing and monitoring using an inhomogeneous multi-layer model of the human head. A model with seven layers composed of skin, bone, fat, dura, cerebro spinal fluid (CSF), grey matter, and white matter was adopted for our multi-layer model. The antenna was embedded below the bone and above the dura of the head phantom. Artificial tissue emulating (ATE) materials were fabricated in semi-solid form and measurement was carried out to check the permittivity and loss tangent of each semi-solid ATE. Implanted antennas for wireless brain signal monitoring data must be compact, lightweight, and biocompatible. The proposed antenna was designed with Taconic RF-35 as the substrate with an overall size of
. The proposed antenna has a −10 dB reflection bandwidth of 2.42-2.50 GHz and a gain of −25 dBi at the broadside direction. The top and bottom insulators with a thickness of 0.5 mm each were also designed with a Taconic RF-35 substrate. A good agreement between simulated and measured results was achieved for the proposed antenna for both in free space and inside of head phantom.
High-quality neural recording lays the foundation of neuroscience research. The last two decades have witnessed remarkable advances in neural recording front-end design. However, there are two challenges remaining: the increasing bandwidth requirement for modern high-density microelectrode arrays, and the high dynamic range requirement in advanced low voltage and low power systems. This work investigates novel circuit and system designs to address these challenges. This chapter first introduces the characteristics of neural signals, summarizes the design specifications, reviews prior work, and analyzes the key design trade-offs. The design of a general–purpose low-noise neural amplifier is presented, followed by a novel pre-whitening front-end. The pre-whitening amplifier design takes advantage of neural signal’s frequency characteristic. It significantly reduces the dynamic range requirement of the neural amplifier and the ADC resolution without sacrificing the signal quality. A 10-bit SAR ADC is designed for neural signal digitization. In addition, compressed sensing is used to reduce the wireless data rate. Compressed sensing is a signal processing technique that enables sub-Nyquist sampling and near lossless reconstruction of a signal with sparsity in a certain domain, including neural signals. The proposed system has been successfully used in animal experiments for long-term recording, which will be presented in this chapter.
We present a dual-band approach for HF wireless power delivery and UHF backscatter communication in implanted biomedical devices. A testbed is described including a custom implant device as well as an external system based around the USRP B210 software defined radio (SDR) platform. The implant integrates a BPSK backscatter uplink rate of 5 Mbps, with an HF WPT link delivering 1.33 mW at an efficiency of 17%. The implant is 25 mm in diameter and 2.8 mm thick, including the printed circuit substrate, dual-band antenna, all circuitry, and biocompatible silicone encapsulation. It supports up to 10 neural and 4 electromyogram (EMG) channels with a sampling rate of 26.10 kHz for the neural channels and 1.628 kHz for the EMG channels. The communication link is shown to have 0% packet error rate at an implant depth of up to 2.5 cm.
In this study, we introduce a triple-band flexible implantable antenna that is tuned by using a ground slot in three specific bands, namely Medical Implanted Communication Service (MICS: 402-405 MHz) for telemetry, the midfield band (lower gigahertz: 1.45-1.6 GHz) for Wireless Power Transfer (WPT), and the Industrial, Scientific and Medical band (ISM: 2.4-2.45 GHz) for power conservation. This antenna is wrapped inside a printed 3D capsule prototype to show its applicability in different implantable or ingestible devices. The telemetry performance of the proposed antenna was simulated and measured by using a porcine heart. From the simulation and measurement, we found that use of a ground slot in the implantable antenna can improve the antenna performance and can also reduce the Specific Absorption Rate (SAR).
A miniature implantable medical device (IMD) needs a quality clock source for its communication and control circuits. Crystal device is hardly suitable for the in-body clock generator because of the device size limitation. In this paper, a new digital crystal-less clock generation scheme is presented. It uses a digitally controlled oscillator with coarse-fine-tuning structure as the clock source. As the current IMDs are commonly inductively-powered, a strong inductive power carrier is transferred into the in-body system. We propose to leverage the power carrier as the reference clock. We introduce a new all-digital frequency locked loop to track the power carrier frequency. This loop improves the frequency accuracy and stability of the in-body clock source against voltage variation and process variation. Results from post-layout simulation show that the frequency accuracy of the proposed clock source is 0.025%. The RMS and peak-to-peak period jitters of the output clock are 11.3 ps and 60 ps at a frequency of 2 MHz, respectively. The clock generator consumes 0.51 mW with a supply voltage of 1.8 V (required by analog circuits). The core silicon area of the clock generator is 0.036 μm 2 in the 0.18-μm CMOS process.
This paper presents a multiband conformal antenna for implantable as well as ingestible devices. The proposed antenna has the following three bands: medical implanted communication service (MICS: 402-405 MHz), the midfield band (1.45-1.6 GHz), and the industrial, scientific, and medical band (ISM: 2.4-2.45 GHz) for telemetry or wireless monitoring, wireless power transfer (WPT), and power conservation, respectively. A T-shaped ground slot is used to tune the antenna, and this antenna is wrapped inside a printed 3-D capsule prototype to demonstrate its applicability in different biomedical devices. Initially, the performance of the proposed antenna was measured in an American Society for Testing and Materials phantom containing a porcine heart in the MICS band for an implantable case. Furthermore, to stretch the scope of the suggested antenna to ingestible devices, the antenna performance was simulated and measured using a minced pork muscle in the ISM band. A modified version of the midfield power transfer method was incorporated to replicate the idea of WPT within the implantable 3-D printed capsule. Moreover, a near-field plate (NFP) was employed to control the leakage of power from the WPT transmitter. From the simulation and measurements, we found that use of a ground slot in the implantable antenna can improve antenna performance and can also reduce the specific absorption rate. Furthermore, by including the NFP with the midfield WPT transmitter system, unidirectional wireless power can be obtained and WPT efficiency can be increased.
Totally implantable wireless ultrasonic blood flowmeters provide direct-access chronic vessel monitoring in hard-to-reach places without using wired bedside monitors or imaging equipment. Although wireless implantable Doppler devices are accurate for most applications, device size and implant lifetime remain vastly underdeveloped. We review past and current approaches to miniaturization and implant lifetime extension for wireless implantable Doppler devices and propose approaches to reduce device size and maximize implant lifetime for the next generation of devices. Additionally, we review current and past approaches to accurate blood flow measurements. This review points toward relying on increased levels of monolithic customization and integration to reduce size. Meanwhile, recommendations to maximize implant lifetime should include alternative sources of power, such as transcutaneous wireless power, that stand to extend lifetime indefinitely. Coupling together the results will pave the way for ultra-miniaturized totally implantable wireless blood flow monitors for truly chronic implantation.
We study how the location of synaptic input influences the stablex firing states in coupled model neurons bursting rhythmically at the gamma frequencies (20-70 Hz). The model neuron consists of two compartments and generates one, two, three or four spikes in each burst depending on the intensity of input current and the maximum conductance of M-type potassium current. If the somata are connected by reciprocal excitatory synapses, we find strong correlations between the changes in the bursting mode and those in the stable phase-locked states of the coupled neurons. The stability of the in-phase phase-locked state (synchronously firing state) tends to change when the individual neurons change their bursting patterns. If, however, the synaptic connections are terminated on the dendritic compartments, no such correlated changes occur. In this case, the coupled bursting neurons do not show the in-phase phase-locked state in any bursting mode. These results indicate that synchronization behaviour of bursting neurons significantly depends on the synaptic location, unlike a coupled system of regular spiking neurons.
A novel microelectronic "pill" has been developed for in situ studies of the gastro-intestinal tract, combining microsensors and integrated circuits with system-level integration technology. The measurement parameters include real-time remote recording of temperature, pH, conductivity, and dissolved oxygen. The unit comprises an outer biocompatible capsule encasing four microsensors, a control chip, a discrete component radio transmitter, and two silver oxide cells (the latter providing an operating time of 40 h at the rated power consumption of 12.1 mW). The sensors were fabricated on two separate silicon chips located at the front end of the capsule. The robust nature of the pill makes it adaptable for use in a variety of environments related to biomedical and industrial applications.
This paper describes the design and implementation of fully integrated rectifiers in BiCMOS and standard CMOS technologies for rectifying an externally generated RF carrier signal in inductively powered wireless devices, such as biomedical implants, radio-frequency identification (RFID) tags, and smartcards to generate an on-chip dc supply. Various full-wave rectifier topologies and low-power circuit design techniques are employed to decrease substrate leakage current and parasitic components, reduce the possibility of latch-up, and improve power transmission efficiency and high-frequency performance of the rectifier block. These circuits are used in wireless neural stimulating microsystems, fabricated in two processes: the University of Michigan's 3-μm 1M/2P N-epi BiCMOS, and the AMI 1.5-μm 2M/2P N-well standard CMOS. The rectifier areas are 0.12-0.48 mm2 in the above processes and they are capable of delivering >25mW from a receiver coil to the implant circuitry. The performance of these integrated rectifiers has been tested and compared, using carrier signals in 0.1-10-MHz range.
In this retinal prosthesis project, a rehabilitative device is
designed to replace the functionality of defective photoreceptors in
patients suffering from retinitis pigmentosa (RP) and age-related
macular degeneration (AMD). The device consists of an extraocular and an
intraocular unit. The implantable component receives power and a data
signal via a telemetric inductive link between the two units. The
extraocular unit includes a video camera and video processing board, a
telemetry protocol encoder chip, and an RF amplifier and primary coil.
The intraocular unit consists of a secondary coil, a rectifier and
regulator, a retinal chip with a telemetry protocol decoder, a stimulus
signal generator, and an electrode array. This paper focuses on the
design, fabrication, and testing of a microchip which serves as the
telemetry protocol decoder and stimulus signal generator. It is
fabricated by MOSIS with 1.2-mm CMOS technology and was demonstrated to
provide the desired biphasic current stimulus pulses for an array of 100
retinal electrodes at video frame rates
1. A Neural Processor for Maze Solving.- 2 Resistive Fuses: Analog Hardware for Detecting Discontinuities in Early Vision.- 3 CMOS Integration of Herault-Jutten Cells for Separation of Sources.- 4 Circuit Models of Sensory Transduction in the Cochlea.- 5 Issues in Analog VLSI and MOS Techniques for Neural Computing.- 6 Design and Fabrication of VLSI Components for a General Purpose Analog Neural Computer.- 7 A Chip that Focuses an Image on Itself.- 8 A Foveated Retina-Like Sensor Using CCD Technology.- 9 Cooperative Stereo Matching Using Static and Dynamic Image Features.- 10 Adaptive Retina.
The local oscillator (LO) in a wireless transceiver satisfies many
exacting requirements. A variable frequency enables a phase-locked loop
(PLL) to servo the LO to a stable lower frequency reference, or to
correct frequency errors from measurements on the received signal. A low
phase noise ensures little interference with nearby channels. A large LO
voltage-swing means that it can drive a mixer with greater linearity.
Finally, in single-sideband applications, the LO must supply precise
quadrature phases. Low phase noise mandates use of a high-Q resonator to
tune the LO, although most RF resonators are usually not integrable on
ICs. Quadrature outputs are usually derived from RC phase-shift of a
single-phase LO output, but this is susceptible to component inaccuracy
and loss in LO amplitude. The authors present a 900 MHz oscillator
circuit implemented in 1 μm CMOS that affords modestly low-phase
noise, has variable frequency with large output swing, and provides
quadrature-phase outputs from two identical coupled oscillators,
connected in such a way that they exert a mutual squelch when their
relative phase is not in quadrature. The coupled oscillators synchronize
to exactly the same frequency, in spite of mismatches in their resonant
circuits
Integrated circuits for use in a wireless microsystem used in neural recording are described. The implantable microsystem will be powered and transmit digitized data using RF telemetry. Recorded neural signals are amplified, multiplexed, digitized using a 2nd order sigma-delta modulator, and then transmitted to the outside world by an on-chip transmitter. The circuit is designed using a standard 1.5 μm CMOS process. Several circuit blocks have been designed, fabricated and show to operate as expected.
Magnetic transcutaneous coupling is frequently used for power and data transfer to implanted electronic devices. The proposed development of MicroImplants, small enough to be injected through a hypodermic needle suggest the need for a high-efficiency magnetic transcutaneous link. This paper describes the use of a multifrequency transmitter coil driver based upon the Class E topology. The development of a "high-Q approximation" which simplifies the design procedure is presented. A closed-loop controller to compensate for transmitter and receiver variations, and a method of data modulation, using synchronous frequency shifting are described. The closed-loop Class E circuit shows great promise, especially for circuits with unusually low coefficients of coupling. Currents of several amperes, at radio frequencies, can easily and efficiently be obtained.
The analysis and design of an optoelectronic transceiver for bidirectional communication between a live laboratory animal and a fixed measurement instrument are presented. The transceiver is based on diffuse infrared radiation and operates even without direct sight of transmitter and receiver. The communication channel is first analyzed in terms of parameters such as attenuation, bandwidth, and S/N ratio. Multiplexing and modulation schemes are considered and the design of circuits used in the miniaturized battery-operated mobile unit are discussed. Examples of experimental in vivo measurements of brain metabolites are presented.
This paper describes a 3-D microelectrode array for the chronic recording of single-unit activity in the central nervous system. The array is formed by a microassembly of planar silicon multishank microprobes, which are precisely positioned in a micromachined platform that resides on the surface of the cortex. Interconnects between the probes and the platform are formed using electroplated nickel lead transfers, implemented using automated computer control. All dimensions are controlled to +/- 1 micron and sank/probe separations as small as 100 microns are possible. Four-probe 16-shank prototype arrays have been tested chronically in guinea pig cortex. After three months in vivo, no significant tissue reaction has been observed surrounding these structures when they remain free to move with the brain, with normal appearing tissue between shanks spaced at 150 microns to 200 microns intervals. The array structure is compatible with the use of signal processing circuitry both on the probes and on the platform. A platform-based signal processing system has been designed to interface with several active probes, providing direct analog access to the recording sites, performing on-chip analog-to-digital conversion of neural activity, and providing simple binary-output recognition of single-unit spike events using a user-input threshold voltage.
We have developed a three-dimensional silicon electrode array which provides 100 separate channels for neural recording in cortex. The device is manufactured using silicon micromachining techniques, and we have conducted acute recording experiments in cat striate cortex to evaluate the recording capabilities of the array. In a series of five acute experiments, 58.6% of the electrodes in the array were found to be capable of recording visually evoked responses. In the most recent acute study, the average signal-to-noise ratio for recordings obtained from 56 of the electrodes in the array was calculated to be 5.5:1. Using standard window discrimination techniques, an average of 3.4 separable spikes were identified for each of these electrodes. In order to compare the two-dimensional mapping capabilities of the array with those derived from other technologies, orientation preference and ocular dominance maps were generated for each of the evoked responses. Histological evaluation of the implant site indicates some localized tissue insult, but this is likely due to the perfusion procedure since high signal-to-noise ratio neural responses were recorded. The recording capabilities of the Utah Intracortical Electrode Array in combination with the large number of electrodes available for recording make the array a tool well suited for investigations into the parallel processing mechanisms in cortex.
This paper describes a low-cost, self-oscillating, detuning-in-sensitive, class-E driver for transcutaneous power and data transmission to implantable microsystems. A voltage feedback scheme using a fast comparator for zero-crossing detection and a CMOS start-up circuit were used to stabilize the class-E operation for various transmitter coil inductance values. This technique solves the common problem of mismatch between the switching frequency of the driving device and the resonant frequency of the load network, which can cause excessive power loss and damage to the active device. Data is transmitted by AM modulation of the carrier through switching the power supply between two levels. The transmitter uses a 9-V supply, consumes 212 mA, operates at 3.9 MHz, and has an efficiency of 71%. The efficiency is stable (< 2% change) against 13% variations in the inductance value of a pancake shaped transmitter coil. Index Terms-Biomedical microsystems, class-E transmitter, implantable electronics, inductive powering, transcutaneous links.
A two-channel FM biopotential recording system fabricated on a foldable, lightweight, polyimide substrate is presented. Each channel consists of a biopotential amplifier followed by a Colpitts oscillator with operating frequency tunable in the 88-108 MHz commercial FM band. The overall system measures 10 mm X 10 mm X 3 mm, weighs 0.74 g, uses two 1.5-V batteries, dissipates about 2 mW, and has a transmission range of 2 m. Using this system, electromyogram signals have been recorded from the dorsal ventral muscle and the dorsal longitudinal muscle of a giant sphinx moth (manduca sexta).
A radio frequency (RF) telemetry system with a shape memory alloy microelectrode was designed and fabricated. The total size and weight are 15 mm x 8 mm and 0.1 g, respectively. Since the telemeter is small and light enough to be loaded on a small animal such as an insect, the system can be used for the neural recording of a freely moving insect. The RF-telemeter can transmit signals by frequency modulation transmission at 80-90 MHz. The transmitted signals can be received up to about 16 meters away from the telemeter with a high signal-to-noise ratio. The neural activity can be detected without attenuation by using an instrumentation amplifier with its input impedance set to 2 Mohms at 1 kHz. The telemeter was loaded on a cockroach and the neural activity during a free-walk was successfully measured through this telemetry system.
Despite the success of implantable batteries as commonly used in pacemakers, implantable neural prosthetic devices typically have power requirements that exceed the capability of reasonably-sized implantable batteries. Therefore, transcutaneous magnetic coupling remains the method of choice for powering implanted neural prostheses. Using the same inductive link for transfer of power and bidirectional telemetry is an attractive solution to powering and communicating with implanted devices thus avoiding percutaneous plugs, wires, or conduits. The Class-E power oscillator has been identified as a highly-efficient transmitter circuit for use as a means of transferring power to an implant. Although the high-Q nature of this topology makes rapid modulation difficult, it is feasible to use synchronous frequency-shift-keyed (FSK) modulation of the Class-E circuit thereby combining an efficient power transmitter with a highspeed data link. Using this method, the transmitter can be modulated on a cycle-by-cycle basis with little to no additional power loss. Within an implanted device, demodulation of the FSK transmitted carrier can be accomplished using a novel demodulation circuit.
Wireless telemetry of bioelectric signals, specifically neural recordings, is desirable in many research and clinical applications. These include, but are not limited to: telemetry and recording of neural activity in laboratory animals, telemetry of EEG, telemetry of short-term implanted electrode arrays for epilepsy medical diagnosis, functional electrical stimulation (FES) systems, and implantable neuroprosthetic devices for sensory and command control. The present use of either head-mounted connectors attached to wires in lab animals, or transcutaneous leads for cortical monitoring in clinical patients, is often a major restriction in the effectiveness and duration of the recording process. We report on a fully-integrated design for a 16-channel neural amplifier array combined with a UHF-FM transmitter that would allow near co-location of the amplifier and electrodes as well as eliminate troublesome signal interconnecting wires to remote recording equipment. The power required by the integrated biotelemetry system is sufficiently low to allow transcutaneous power transfer to one or more of these devices via a magnetically-coupled link.
This paper considers design of a miniature transmitter operating with near-field inductive coupling, in the context of embedded electronic systems in medical diagnosis, environmental monitoring, and other industrial applications. Recent developments in system-on-chip and lab-on-a-chip technologies made the implementation of such miniaturized systems feasible, and pose an interesting set of problems with respect to low-power, short-range wireless communications. The design of a compact transmitter with a magnetic antenna is discussed and some early results are presented.
There is a need among scientists and clinicians for low-noise, low-power biosignal amplifiers capable of amplifying signals in the mHz to kHz range while rejecting large dc offsets generated at the electrode-tissue interface. The advent of fully-implantable multielectrode arrays has created the need for fully-integrated micropower amplifiers. We designed and tested a novel bioamplifier that uses a MOS-bipolar pseudo-resistor to amplify signals down to the mHz range while rejecting large dc offsets. We derive the theoretical noise-power tradeoff limit - the noise efficiency factor - for this amplifier and demonstrate that our VLSI implementation approaches that limit. The resulting amplifier, built in a standard 1.5μm CMOS process, passes signals from 0.1mHz to 7.2kHz with an input-referred noise of 2.2μVrms and a power dissipation of 80μW while consuming 0.16mm2 of chip area.
A radio frequency (RF) telemetry system with a shape memory alloy
(SMA) microelectrode was designed and fabricated. The total size and
weight are respectively 15 mm×8 mm and 0.1 g, without a battery.
Since the telemeter is small and light enough to be loaded on a small
animal such as an insect with no restraint on motion, the system can be
used for the neural recording of a freely moving insect. The SMA
microelectrode, fabricated by using microelectromechanical systems
(MEMS) technologies, can be easily attached to a nerve by electrically
actuating the electrode structure, Moreover, it does not detach from the
nerve during the insect's motion due to its clipping structure. The
telemeter can transmit signals by frequency modulation (FM) transmission
at 80~90 MHz. The transmitted signals can be received up to about 16 m
away from the telemeter with a high S/N ratio. The neural activity can
be detected without attenuation by using an instrumentation amplifier
with its input impedance set to 2 MΩ at 1 kHz. The telemeter was
loaded on a cockroach and the neural activity during a free-walk is
measured through this telemetry system
The power consumption of an LC-tank oscillator is strongly
affected by the varactor quality factor, whether the inductor is on- or
off-chip. This paper proposes a new solution to realize high-Q, highly
tunable on-chip varactors in a standard CMOS process, achieving a
quality factor higher than 100 at 1 GHz, for a tuning ratio of 2. Other
solutions are described and their respective advantages compared, while
their characteristics are measured for a 0.5 μm process
Radio-frequency (RF) coils are used extensively in the design of implantable devices for transdermal power and data transmission. The practical issues of coil misalignments and configurations have not been investigated, and this paper presents a detailed theoretical analysis of misalignment effects in RF coil systems, including lateral and angular misalignments. Formulas are derived for the mutual inductance and, whenever possible, simplified upper bounds and lower bounds of the coupling coefficient are provided. A design procedure is established to maximize coil coupling for a given configuration, and a companion paper [1] discusses a circuit design technique to reduce the effects of misalignment on transmission efficiency.
A stable transcutaneous transmission of power and signal via two coupled coils with minimized dependence on the relative spacing of external and implanted coil is possible by employing "critical coupling" between implanted and external circuits. Optimizing coil geometries and preventing the RF output amplifier from saturating is necessary to approximately maintain critical coupling despite placement tolerances within a reasonable range. Based on these considerations a transcutaneous signal transmission system for an auditory prosthesis has been designed. This transmission system can also be used for several other stimulation purposes needing accurate control of stimulation parameters.
A CMOS integrated circuit for a noninvasive biological-signal telemetry system specified for use in medical and physiological studies of the influence of weightlessness in space is presented. The system can monitor multichannel (4 channels maximum) biological signals from multiple subjects (4 subjects maximum) in real time by using time multiplexing. A key technique so-called synchronized multiple-subject telemetry, to achieve multiple-subject telemetry has been proposed. This technique utilizes bidirectional optical transmissions with direct and scattered infrared lights between an observer and each of the subjects. An experimental CMOS IC to give a small light-weight low-power, and smart telemetry instrument for use on animals has been developed. This IC is for evaluating circuit blocks of the implantable monolithic telemetry instrument. The major circuit blocks include CMOS digital circuits for synchronization, subject selection and time multiplexing, analog circuits for pulse interval modulation, and other blocks such as a CMOS optical pulse receiver and an LED driver. A preliminary experimental multichannel telemetry from two subjects has been performed with the implemented IC chips, and the principal operation of the multiple-subject optical biotelemetry has been demonstrated.
Electromagnetic waves from the lower radio frequencies up through the optical spectrum can generate a myriad of effects and responses in biological specimens. Some of these effects can be harmful to man at high radiation intensities, producing burns, cataracts, chemical changes, etc. Biological effects have been reported at lower radiation intensities, but it is not now known if low-level effects are harmful. Even behavioral changes have been reported. Most of the effects are not harmful under controlled conditions, and can thereby be used for therapeutic purposes and to make useful diagnostic measurements. The problem of microwave penetration into the body with resultant internal power absorption is approached from both the theoretical and the experimental viewpoints. The results are discussed in terms of therapeutic warming of tissues and possible hazards caused by internal "hot spots." The absorption and scattering effects of light in biological tissues are reviewed. Molecular absorption peaks in the optical spectrum are useful for making molecular concentration measurements by spectroscopy. Much of the related work in the literature is summarized, some new results are presented, and several useful applications of wave energy and medical instruments are discussed.
There is a need among scientists and clinicians for low-noise low-power biosignal amplifiers capable of amplifying signals in the millihertz-to-kilohertz range while rejecting large dc offsets generated at the electrode-tissue interface. The advent of fully implantable multielectrode arrays has created the need for fully integrated micropower amplifiers. We designed and tested a novel bioamplifier that uses a MOS-bipolar pseudoresistor element to amplify low-frequency signals down to the millihertz range while rejecting large dc offsets. We derive the theoretical noise-power tradeoff limit - the noise efficiency factor - for this amplifier and demonstrate that our VLSI implementation approaches this limit by selectively operating MOS transistors in either weak or strong inversion. The resulting amplifier, built in a standard 1.5-μm CMOS process, passes signals from 0.025Hz to 7.2 kHz with an input-referred noise of 2.2 μVrms and a power dissipation of 80 μW while consuming 0.16 mm2 of chip area. Our design technique was also used to develop an electroencephalogram amplifier having a bandwidth of 30 Hz and a power dissipation of 0.9 μW while maintaining a similar noise-power tradeoff.
New applications such as wireless integrated network sensors
(WINS) require radio-frequency transceivers consuming very little power
compared to usual mainstream applications, while still working in the
ultra-high-frequency range. For this kind of application, the
LC-tank-based local oscillator remains a significant contributor to the
overall receiver power consumption. This statement motivates the
development of good on-chip varactors available in a standard process.
This paper describes and compares the available solutions to realize
high-Q, highly tunable varactors in a standard digital CMOS
submicrometer process. On this basis, quality factors in excess of 100
at 1 GHz, for a tuning ratio reaching two, have been measured using a
0.5-μm process
Electrical components for a fully implantable neural recording systemFully integrated wideband high-current rectifiers for inductively powered devices
- C Charles
- Univ Utah
- Elect
- Comput
- Eng
- M Prog
- K Ghovanloo
- Najafi
C. Charles, "Electrical components for a fully implantable neural recording system," Masters thesis, Univ. Utah, Elect. Comput. Eng. Prog., Salt Lake City, Utah, 2003. [13] M. Ghovanloo and K. Najafi, "Fully integrated wideband high-current rectifiers for inductively powered devices," IEEE J. Solid-State Circuits, vol. 39, no. 11, pp. 1976–1984, Nov. 2004.
A 900-MHz [24]Circuitry for a wireless microsystem for neural recording microprobes
- A Rofourgan
- J Rael
- M Rofourgan
- A H Abidi
- K Yu
- Najafi
A. Rofourgan, J. Rael, M. Rofourgan, and A. Abidi, "A 900-MHz [24] H. Yu and K. Najafi, "Circuitry for a wireless microsystem for neural recording microprobes," in Proc. 2001 Int. Conf. IEEE Engineering in Medicine and Biology Society, Istanbul, Turkey, Oct. 2001, pp. 761–764.
Semiconductor Devices: Physics and Technology Nathan M. Neihart (S'02) was born in Salt Lake City
- S M Sze
S. M. Sze, Semiconductor Devices: Physics and Technology. New York: Wiley, 2002. Nathan M. Neihart (S'02) was born in Salt Lake City, Utah, in 1979. He received both the B.S. and M.S. degrees in electrical engineering from the
- Int
- Conf
Int. Conf. IEEE Engineering in Medicine and Biology Society, Cancún,
Mexico, Sep. 2003, pp. 3028–3031.
- Int
- Conf
Int. Conf. IEEE Engineering in Medicine and Biology Society, Cancún,
Mexico, Sep. 2003, pp. 3028-3031.
A 900-MHz CMOS LC-oscillator with quadrature outputs
- A Rofourgan
- J Rael
- M Rofourgan
- A Abidi
A. Rofourgan, J. Rael, M. Rofourgan, and A. Abidi, "A 900-MHz
CMOS LC-oscillator with quadrature outputs," in ISSCC Dig. Tech.
Papers, San Francisco, CA, Feb. 1996, pp. 392-393.