Article

Micropower Circuits for Bidirectional Wireless Telemetry in Neural Recording Applications

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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.

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... 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 ...
Article
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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 ...
Article
Full-text available
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\epsilon _{r} ), effective permeability ( μr\mu _{r} ), 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. ...
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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. ...
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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]. ...
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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. ...
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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]. ...
Book
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. ...
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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. ...
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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. ...
Article
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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 . ...
Conference Paper
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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. ...
Article
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. ...
Article
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. ...
Article
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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]. ...
Article
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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]. ...
Conference Paper
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. ...
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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. ...
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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. ...
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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]. ...
Thesis
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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.
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Conference Paper
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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.
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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.
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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).
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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.
Conference Paper
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.
Conference Paper
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.
Conference Paper
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.
Conference Paper
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.
Conference Paper
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
Conference Paper
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
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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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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
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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
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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
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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
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Int. Conf. IEEE Engineering in Medicine and Biology Society, Cancún, Mexico, Sep. 2003, pp. 3028–3031.
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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
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  • 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.