Inductive-coupling Link Research Articles

A Cycle by Cycle FSK Demodulator With High Sensitivity of 1% Frequency Modulation Index for Implantable Medical Devices

This paper presents a cycle by cycle Frequency Shift Keying (FSK) demodulator, able to demodulate a FSK signal with 1% frequency modulation index (MI), in a single cycle. Based on the proposed demodulation scheme, a high rate data transmission link can be established through a high-Q inductive coupling link, breaking the basic tradeoff between the power transfer efficiency (PTE) and data rate in single carrier wireless power and data transfer systems. Designed and simulated with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18\mu m$ </tex-math></inline-formula> CMOS process, the proposed FSK demodulator, detects successfully a 5Mbps data with a carrier frequency of 5MHz. A test chip is fabricated in 180nm CMOS technology. Measurement results shows that the demodulator is able to demodulate the cycle-by-cycle modulated FSK signals with low modulation index of 2.5%, with a BER of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.24\times 10^{-5}$ </tex-math></inline-formula> .

Efficient Underwater Sensor Data Recovery Method for Real-Time Communication Subsurface Mooring System

Marine submerged buoys can effectively obtain various parameters of seawater, which plays an important role in the research of marine physical phenomena, marine environmental changes, and climate change. However, traditional self-contained submerged buoys usually work underwater at a depth of about 100 m, and the observation data cannot be obtained before their recovery, which cannot satisfy the needs of real-time data acquisition for marine scientific research. To solve this problem, this paper proposes a real-time communication subsurface mooring system that consists of a satellite communication buoy (SCB), conductivity–temperature–depth sensors (CTD), and an inductive coupling mooring cable. The underwater inductive coupling link collects the data from the underwater sensors and transmit it to the SCB. Then, the data will be transmitted to the station receiver via satellite communication module integrated into the SCB. In order to ensure a high success rate of data recovery, the stress analysis and hydrodynamic simulation of the SCB were carried out in this paper. The results show that the SCB maintained a relatively stable attitude in the 3–4 sea state. The attitude data obtained from the subsequent sea trial was consistent with the simulation results, and the success rate of satellite communication during this period was more than 95%. In this paper, a modular embedded hardware circuit was designed to meet the functional requirements of the subsurface mooring system. An efficient data recovery strategy was also developed, which ensured that the average power consumption of the system was low and the success rate of data recovery is not less than 90% when operating in the severe sea state for a long time. The system underwent sea trials in the South China Sea for more than 3 months from the end of 2021 to the beginning of 2022. It transmitted more than 2034 sets of seawater profile temperature, salinity, and depth data in real-time, with a success rate of over 91% of the total sample data. The CTD data returned in real-time from our system is consistent with the data of the HYCOM and World Ocean Atlas (WOA), and a cyclonic mesoscale eddy was detected in the operation area.

Analysis of Four Coils by Inductive Powering Links for Powering Bio-implantable Sensor

The inductive coupling link technique is popularly used for transmitting power in many biomedical applications, where it helps in transferring power to numerous implanted biomedical devices like a wireless pressure sensor system. It has also been noted that the inductive coupling variables significantly affect the coupling efficiency. In this study, the researchers have investigated the inductive coupling link variables for 3 transmitter coils and one receiver coil. They used a resonant frequency of 27 MHz as the operating frequency, based on the Industrial, Scientific and Medical (ISM) band. The experimental results indicated that the Voltage gain (i.e., Vgain) value of the inductive links was dependent on the Coupling Factor (K) existing between every coil and load resistance (i.e., Rload). It was also noted that the value of the Voltage gain increased with an increase in the implanted resistance, based on a constant coupling factor. Furthermore, the simulation results indicated that if the Rload=1000, the Vgain value would be maximal, whereas if Rload = 200Ω, the Vgain value would be minimal and ≈ 5V.These results indicated that the operating system could satisfy all the requirements for powering the implanted sensor biodevices.

Optimization of Bio-Implantable Power Transmission Efficiency Based on Input Impedance

Recently, the inductive coupling link is the most robust method for powering implanted biomedical devices, such as micro-system stimulators, cochlear implants, and retinal implants. This research provides a novel theoretical and mathematical analysis to optimize the inductive coupling link efficiency driven by efficient proposed class-E power amplifiers using high and optimum input impedance. The design of the coupling link is based on two pairs of aligned, single-layer, planar spiral circular coils with a proposed geometric dimension, operating at a resonant frequency of 13.56 MHz. Both transmitter and receiver coils are small in size. Implanted device resistance varies from 200 Ω to 500 Ω with 50 Ω of stepes. When the conventional load resistance of power amplifiers is 50 Ω, the efficiency is 45%; when the optimum resonant load is 41.89 Ω with a coupling coefficient of 0.087, the efficiency increases to 49%. The efficiency optimization is reached by calculating the matching network for the external LC tank of the transmitter coil. The proposed design may be suitable for active implantable devices.

A Spike-Latency Transceiver With Tunable Pulse Control for Low-Energy Wireless 3-D Integration

Wireless 3-D integration using inductive coupling links (ICLs) has recently gained attention as a low-cost alternative to through-silicon vias (TSVs) for interconnecting stacked silicon tiers. However, 3-D integration using ICLs is often criticized for its inferior energy efficiency compared with conventional approaches. To address this challenge, in this article, we present a low-energy ICL transceiver that combines a spike-latency encoding scheme (to reduce the number of energy-expensive analog transmit pulses by encoding data in the time domain) and a tunable current driver (to minimize the transmit energy depending on the given integration scenario). The proposed transceiver is modeled mathematically, simulated in 0.35- $\mu \text{m}$ , 65-nm, and 28-nm CMOS technologies and experimentally validated in a two-tier 3-D stacked silicon test chip. Silicon evaluation of the proposed modulation approach demonstrates an energy of 7.4 pJ/bit, representing a reduction >13% when compared with previously reported schemes (or 7.4% when also considering the additional energy overheads of peripheral clock timing control circuits). The simulated results show even greater energy savings (up to 28%) at more advanced technology nodes. Combined with the adaptive current driver, this results in a $7.7\times $ improvement in energy per bit compared with the state-of-the-art implementations across the same communication distance, marking an important progression toward cost and energy-efficient 3-D integration.

An integrated low-power Binary-PAM based wireless telemetry circuit for implantable cardiac pacemakers

A low-power wireless telemetry circuit integrated in an analog front-end (AFE) chip for implantable cardiac pacemakers is presented in this paper. With an on-chip telemetry circuit, the electrocardiogram (ECG) data can be transmitted directly from the AFE chip to a programmer outside the human body. Such a direct-memory-access (DMA) scheme improves data transmission efficiency and saves the overall power consumption. The proposed telemetry system employs a near-field inductive-coupling link with oscillating frequency of 128 ​kHz and a binary pulse-amplitude-modulation (PAM) strategy to achieve higher reliability. It consumes lower power and reach a longer communication distance when compared to conventional on-off-keying (OOK) modulation method. In order to further reduce the power consumption, pulse width adjustment technique is adopted in the transmitter. Also, edge detection and window detection techniques are employed in the receiver, making it more robust and immune to noise, disturbance and clock skew. The AFE chip is implemented using a 0.35-μm CMOS technology and the telemetry circuit occupies an active area of 1150umX350 ​μm. Measurement results show that the proposed wireless communication circuit can operate under a power supply range of 2.0–2.8 ​V, and achieves a maximum communication distance of 12 ​cm with current consumption lower than 26 ​μA and bit error rate less than 10−5.

Design and Optimization of Inductively Coupled Spiral Square Coils for Bio-Implantable Micro-System Device

Due to the development of biomedical microsystems technologies, the use of wireless power transfer systems in biomedical application has become very largely used for powering the implanted devices. The wireless power transfer by inductive resonance coupling link, is a technic for powering implantable medical devices&lt;strong&gt; &lt;/strong&gt;(IMDs) between the external and implanted circuits. In this paper we describe the design of an inductive resonance coupling link using for powering small bio-implanted devices such as implantable bio-microsystem, peacemaker and cochlear implants. We present the reduced design and an optimization of small size obtained spiral coils of a 9.5 mm&lt;sup&gt;2&lt;/sup&gt; implantable device with an operating frequency of 13.56 MHz according to the industrial scientific-medical (ISM). The model of the inductive coupling link based on spiral square coils design is developed using the theoretical analysis and optimization geometry of an inductive link. For a mutual distance between the two coils at 10mm, the power transfer efficiency is about 79% with , coupling coefficient of 0.075 and a mutual inductance value of 2µH. In comparison with previous works, the results obtained in this work showed better performance such as the weak inter coils distance, the hight efficiency power transfer and geometry.

Design and Optimization of Inductive-Coupling Links for 3-D-ICs

Recent research in the field of 3-D system integration has looked to the use of inductive-coupling links (ICLs) to provide vertical connectivity without incurring the inflated fabrication and testing costs associated with through-silicon vias. For power-efficient ICL design, optimization of the utilized physical inductor geometries is essential, but currently must be performed manually in a process that can take several hours. As a result, the generation of optimized inductor designs poses a significant challenge. In this paper, we address this challenge in three main contributions: 1) a novel, nonuniform planar inductor layout that exhibits enhanced performance when compared with conventional uniform inductors; 2) a rapid solver for evaluating inductor layouts; and 3) a high-speed optimization algorithm for determining best performing coil pairs. These three contributions are combined as a CAD tool for optimization of ICLs for 3-D-ICs (COIL-3-D). Results demonstrate that COIL-3-D achieves an average accuracy within 7.8% of finite-element tools consuming a small fraction of the time ( $1.5\times 10^{-3}$ %), significantly ameliorating the design of ICL-based 3-D-ICs. We also demonstrate that using COIL-3-D to optimize ICL inductor layouts can yield significant performance (up to 41.5% bandwidth improvement) and power (up to 8.1% power improvement) benefits, when compared with layouts used in prior ICL implementations. For these reasons, this paper unlocks new potential for low-cost, power-efficient 3-D integration using ICLs.

Resonant Configuration Topology Exploration for Inductive Link Power Transfer

This paper investigates the performance of circuit topology used in wireless power applications to optimize the level of maximum efficiency. We analyse the series and the parallel resonant topologies for use in an inductive coupling link to derive power transfer efficiency expressions verified using MATLAB. We look into the two topologies into the link under resonant conditions for selectively supplying the device with power. The results are obtained analytically which are verified subsequently by MATLAB simulation. We then analyse the links to see how maximum power transfer efficiency for a given pair of coils can be achieved. The topology at a given tuning frequency is used for powering a selected resistive load. The method is presented using a given pair of coils simulated and the results agree well with the theoretical explanation and derivations.

Suggested Methods to Solve the Coils Misalignment for the Biomedical Implants

One of the major problems of the inductive coupling link in the biomedical implantable devices is the misalignment between coils. This paper produces two simple suggested methods to avoid and reduce the misalignment between two coils. The first one is to split the implanted coil into two identical coils with 450 μH of inductance where the external coil was equal to them in inductance ~ 900μH. The results show that the received powers are constant and compensated by one of the coils, which provides a stable power at the implant. The second proposed suggestion is to use two separated identical coils situated in the center angles outside the human skin. The transmitting RF power of the both coils has a same resonance frequency and received with a single small implant coil, which sums the received RF signals where the amplitudes are double. The mathematical analysis of the second suggestion is introduced.

Near-Field Inductive-Coupling Link to Power a Three-Dimensional Millimeter-Size Antenna for Brain Implantable Medical Devices.

Near-field inductive-coupling link can establish a reliable power source to a batteryless implantable medical device based on Faraday's law of induction. In this paper, the design, modeling, and experimental verification of an inductive-coupling link between an off-body loop antenna and a 0.9 three-dimensional (3-D) bowtie brain implantable antenna is presented. To ensure reliability of the design, the implantable antenna is embedded in the cerebral spinal fluid of a realistic human head model. Exposure, temperature, and propagation simulations of the near electromagnetic fields in a frequency-dispersive head model were carried out to comply with the IEEE safety standards. Concertedly, a fabrication process for the implantable antenna is proposed, which can be extended to devise and miniaturize different 3-D geometric shapes. The performance of the proposed inductive link was tested in a biological environment; in vitro measurements of the fabricated prototypes were carried in a pig's head and piglet. The measurements of the link gain demonstrated in the pig's head and in piglet. The in vitro measurement results showed that the proposed 3-D implantable antenna is suitable for integration with a miniaturized batteryless brain implantable medical device (BIMD).

An Inductively Coupled Power and Data Link with Self-referenced ASK Demodulator and Wide-range LDO for Bio-implantable Devices

This paper describes a neural stimulation system that employs an inductive coupling link to transfer power and data wirelessly. For the reliable data and power delivery, a self–referenced amplitudeshift keying (ASK) demodulator and a wide-range voltage regulator are suggested and implemented in the proposed stimulator system. The prototype fabricated in 0.35 um BCD process successfully transferred 1.2 Kbps data bi-directionally while supplying 4.5 mW power to internal MCU and stimulation block.

Miniaturized Resonant Power Conversion for Implanted Medical Devices

The design of a millimetre-sized power converter is proposed which is based on coil coupling that could be integrated into the neural or cardiac implantable medical device (IMD) to provide isolated power or energy transmission by harvesting it from external transmitter device. A special step-up case of transformer coupling to a millimetre-sized receiver coil by a comparatively larger transmitter coil is examined. This paper is expected to increase research efforts to develop the battery-less IMD’s with reduced size, low power, high efficiency, and improved reliability and feasibility. Based on our work, we believe that the inductive coupling link with low loss ferrite material is the suitable method to be used to power the batteryless devices. The converter produces the targeted output power of more than 400 $\mu \text{W}$ with 1 mm3 size of the coil at 2 MHz.

Multipath relaying effects in multiple-node resonant inductive coupling wireless power transfer

Resonant Inductive Coupling Wireless Power Transfer (RIC-WPT)is a key technology to provide an efficient wireless power channel to consumer electronics, biomedical implants and wireless sensor networks. Due to its non radiative nature, RIC Wireless Power Transfer has been considered safe for humans when adhered to magnetic health radiation safety regulations (Christ et al., 2013), unveiling a large range of potential applications in which this technology could be used. However, current deployments are limited to point-to-point links and do not explore the capabilities of Multi-Node RIC-WPT Systems. In such a system, the multi-path relaying effect between different nodes could effectively improve the performance of the link in terms of power transferred to the load and power transfer efficiency. However, depending on the impedance and resonant frequency of the nodes that generate the multi-path effect, these nodes could also act as interfering objects, therefore (a) making the transmitter and/or receiver act as a pass-band filter and (b) losing part of the transmitter magnetic field through coupling to the interfering node. In this paper, a circuit-based analytical model that predicts the behavior of a Multi-Node Resonant Inductive Coupling link is proposed and used to perform a design-space exploration of the multi-path relaying effect in RIC Wireless Power Transfer Systems.

Simple compensation for lateral misalignments in resonant inductive coupling links

This Letter describes a simple compensation method to reduce the transfer efficiency variation in a resonant inductive coupling (RIC) wireless power transfer link subject to lateral misalignment. The technique is based on impedance matching an RIC link such that the link operates at either over-coupling or critical coupling within the extents of lateral misalignment. Applying the method in a test scenario led to a reduction in the range of obtained transfer efficiency values, from 45% of peak value in a conventional arrangement, to 5%. The proposed method has a potential for application in the design of free-positioning planar wireless chargers.

Investigations on Capacitor Compensation Topologies Effects of Different Inductive Coupling Links Configurations

&lt;p&gt;This paper presents investigations on capacitor compensation topologies with different inductive coupling links for loosely coupled inductive power transfer (IPT) system. In general, the main constraint of the loosely coupled IPT system is power losses due to the large leakage inductances. Therefore, to overcome the aforementioned problem, in this work, capacitor compensation is proposed to be used by adding an external capacitor to the system. By using this approach, the resonant inductive coupling can be achieved efficiently and hence the efficiency of the system is also increased significantly. This paper analyzes the performance of two different compensation topologies, which are primary series-secondary series (SS) and primary series- secondary parallel (SP) topology. The performance of such topologies is evaluated through the experimental results at 1MHz operating frequency for different types of inductive coupling. From the results, SS topology produces a high power transfer but SP topology gives better efficiency.&lt;/p&gt;

Dry-contact microelectrode membranes for wireless detection of electrical phenotypes in neonatal mouse hearts.

Continuous monitoring of aberrant electrical rhythms during heart injury and repair requires prolonged data acquisition. We hereby developed a wearable microelectrode membrane that could be adherent to the chest of neonatal mice for in situ wireless recording of electrocardiogram (ECG) signals. The novel dry-contact membrane with a meshed parylene-C pad adjacent to the microelectrodes and the expandable meandrous strips allowed for varying size of the neonates. The performance was evaluated at the system level; specifically, the ECG signals (μV) acquired from the microelectrodes underwent two-stage amplification, band-pass filtering, and optical data transmission by an infrared Light Emitting Diode (LED) to the data-receiving unit. The circuitry was prototyped on a printed circuit board (PCB), consuming less than 300μW, and was completely powered by an inductive coupling link. Distinct P waves, QRS complexes, and T waves of ECG signals were demonstrated from the non-pharmacologically sedated neonates at ~600 beats per minutes. Thus, we demonstrate the feasibility of both real-time and wireless monitoring cardiac rhythms in a neonatal mouse (17-20mm and <1g) via dry-contact microelectrode membrane; thus, providing a basis for diagnosing aberrant electrical conduction in animal models of cardiac injury and repair.

Automatic frequency controller for power amplifiers used in bio-implanted applications: issues and challenges.

With the development of communication technologies, the use of wireless systems in biomedical implanted devices has become very useful. Bio-implantable devices are electronic devices which are used for treatment and monitoring brain implants, pacemakers, cochlear implants, retinal implants and so on. The inductive coupling link is used to transmit power and data between the primary and secondary sides of the biomedical implanted system, in which efficient power amplifier is very much needed to ensure the best data transmission rates and low power losses. However, the efficiency of the implanted devices depends on the circuit design, controller, load variation, changes of radio frequency coil's mutual displacement and coupling coefficients. This paper provides a comprehensive survey on various power amplifier classes and their characteristics, efficiency and controller techniques that have been used in bio-implants. The automatic frequency controller used in biomedical implants such as gate drive switching control, closed loop power control, voltage controlled oscillator, capacitor control and microcontroller frequency control have been explained. Most of these techniques keep the resonance frequency stable in transcutaneous power transfer between the external coil and the coil implanted inside the body. Detailed information including carrier frequency, power efficiency, coils displacement, power consumption, supplied voltage and CMOS chip for the controllers techniques are investigated and summarized in the provided tables. From the rigorous review, it is observed that the existing automatic frequency controller technologies are more or less can capable of performing well in the implant devices; however, the systems are still not up to the mark. Accordingly, current challenges and problems of the typical automatic frequency controller techniques for power amplifiers are illustrated, with a brief suggestions and discussion section concerning the progress of implanted device research in the future. This review will hopefully lead to increasing efforts towards the development of low powered, highly efficient, high data rate and reliable automatic frequency controllers for implanted devices.

DEVELOPMENT OF BIO-IMPLANTED MICRO-SYSTEM WITH SELF-RECOVERY ASK DEMODULATOR FOR TRANSCUTANEOUS APPLICATIONS

This paper deals with the development of bio-implanted micro-system with low-power and high data rate based on amplitude shift keying (ASK) modulation technique to stimulate nerves and muscles. The modified system is operated by a low-frequency band 13.56 MHz according to the industrial-scientific-medical (ISM) bands to avoid the biological tissue damage. The data rate on the demodulator side is from 1 Mb/s and up to 1.5 Mb/s depending of generating binary signal (T BIT = 1 μs or 0.5 μs) with modulation index of 13% and modulation rate 7.3%, 9% and 11%, respectively. The proposed inductive coupling link achieves 73% of link efficiency. The modified rectifier with self-threshold voltage cancellation techniques and voltage regulator without thermal protection circuit and without passive elements occupies small area that is modified to generate adequate and stable DC voltages of 1.8 V. A new ASK demodulator structure based on two comparators is developed to extract a synchronized demodulated signal with minimum error. Thereby no need for clock recovery circuit and delay-locked loops (DLL) circuits for data synchronization at 1 Mb/s and 1.250 Mb/s of speed. The system designed using OrCAD Pspice 16.2 is based on 0.35 μm technologies.

Analysis and optimization of spiral circular inductive coupling link for bio-implanted applications on air and within human tissue.

The use of wireless communication using inductive links to transfer data and power to implantable microsystems to stimulate and monitor nerves and muscles is increasing. This paper deals with the development of the theoretical analysis and optimization of an inductive link based on coupling and on spiral circular coil geometry. The coil dimensions offer 22 mm of mutual distance in air. However, at 6 mm of distance, the coils offer a power transmission efficiency of 80% in the optimum case and 73% in the worst case via low input impedance, whereas, transmission efficiency is 45% and 32%, respectively, via high input impedance. The simulations were performed in air and with two types of simulated human biological tissues such as dry and wet-skin using a depth of 6 mm. The performance results expound that the combined magnitude of the electric field components surrounding the external coil is approximately 98% of that in air, and for an internal coil, it is approximately 50%, respectively. It can be seen that the gain surrounding coils is almost constant and confirms the omnidirectional pattern associated with such loop antennas which reduces the effect of non-alignment between the two coils. The results also show that the specific absorption rate (SAR) and power loss within the tissue are lower than that of the standard level. Thus, the tissue will not be damaged anymore.