An Investigation of Body-Coupled Power Transfer for Multiple Implants.

This paper investigates the RF-induced heating for multiple adjacent orthopedic implants under MRI at 1.5T and 3T exposure. When multiple implants are closely spaced to each other, the interactions between the implants may affect the RF-induced heating. Traditional RF-induced heating labeling is often only applicable to configurations of an individual implant, and is not applicable for multi-implant configurations. Therefore, the aim of this study is to evaluate the effects of multiple orthopedic implants on RF-induced heating and to propose potential appropriate instructions for safe scanning of multi-implantable orthopedic implants. Typical plate and nail implants were used as examples. The effects of implant configuration, relative positions, and number of implants were investigated. Numerical simulations were conducted using full-wave electromagnetic simulation software. Experimental measurements at 1.5 T were performed to validate the numerical results. Numerical results indicate that, due to device interaction, the RF-induced heating of multiple medical implants can be significantly different from that of a single implant. The measured temperature rise for multiple devices could be 2.7 times larger than that of a single implant. Our results confirm that RF-induced heating of multiple implants can be quite different, and do not follow simple superposition of the results from single devices. Instructions for safe scanning of individual orthopedic devices would not be applicable to multi-implant configurations.

The contact impedance of electrodes determines how much current can be injected into the ground for a given voltage. If the ground is very resistive, capacitive electrodes may be an alternative to galvanic coupling. The impedance of capacitive electrodes is often estimated with the assumption that the halfspace is an ideal conductor. Over resistive ground at high frequencies, however, the contact impedance will depend on the electrical properties, i.e. electrical conductivity and permittivity, of the subsurface. Here, we review existing equations for the resistance of a galvanically coupled, spherical electrode in a fullspace, and extend the theory to the general case of a sphere in a spherically layered fullspace. We then develop a method to calculate the impedance of a spherical disc over a homogeneous halfspace.

Intra-body communication (IBC) is a recent and emerging wireless communication technology, which treats the human body as a transmission medium for transmitting and receiving the electrical signals. Pioneer IBC researchers have proposed two types of methods, which are galvanic coupling and capacitive coupling. This paper compares and evaluates a binary frequency-shift keying (BFSK) modulation signal using galvanic and capacitive coupling via IBC for foot plantar pressure sensors. The results of the experiment would guide us as to which method of IBC is more suitable for the specific application. The communication system is designed for foot pressure measurement to analyze pressure distribution during everyday life activities. The research targets IBC operating in the band of 1MHz to 100MHz, and based on the empirical evidence; for this particular application, galvanic coupling shows more promising performances in power, total harmonic distortion and signal-to-noise ratio measurements.

Human Body Communication (HBC) technique uses human body as communication channel for transferring various physiological data. Like humans, plants are also composed of different types of tissues with highly specialized functions. For feasibility study of electrical signal transmission through plant body; two pair of electrodes viz. one pair for the transmitter and one pair for the receiver involving stem of full Mangifera Indica plant by using capacitive coupling has been setup. The signal transmission through the different parts of stem of different thickness has been analyzed in time domain at 100 kHz. Different channel lengths have been used for capacitive coupling and different electrode distance has been used for galvanic coupling under similar environmental conditions at room temperature. Effect of positioning the ground electrode in both longitudinal and transverse directions with respect to signal electrode in galvanic coupling has also been investigated and reported in this paper.

Implanted devices have important applications in biomedical monitoring, diagnosis and treatment, where intra-body communication (IBC) has a decent prospect in wireless implant communication technology by using the conductive properties of the human body to transmit a signal. Most of the investigations on implant IBC are focused on galvanic coupling type. Capacitive coupling IBC device seems hard to implant, because the ground electrode of it seemingly has to be exposed to air. Zhang etal. previously proposed an implantable capacitive coupling electrode, which can be totally implanted into the human body [1], but it lacks an overall characteristic investigation. In this paper, a comparable investigation of characteristics for implant intra-body communication based on galvanic and capacitive coupling is conducted. The human arm models are established by finite element method. Meanwhile, aiming to improve the accuracy of the model, electrode polarization impedance (EPI) is incorporated into the model, and the influences of electrode polarization impedance on simulation results are also analyzed. Subsequently, the corresponding measurements using porcine are conducted. We confirm good capacitive coupling communication performances can be achieved. Moreover, some important conclusions have been included by contrastive analysis, which can be used to optimize implant intra-body communication devices performance and provide some hints for practical IBC design. The conclusions also indicate that the implant IBC has promising prospect in healthcare and other related fields.

Intra-body communication (IBC) is a recent wireless communication technology which uses the human body as the signal propagation medium. While recent studies have shown a degradation of transmission signals for IBC transmissions between limb segments, these degradations have yet to be quantified with respect to relative limb positions. In this paper we report in vivo experiments towards understanding signal attenuation in both capacitive and galvanic coupled IBC methods due to limb joint effects. We examine the impact of elbow joint flexion and extension on signal transmission. Results show that in both IBC methods, the signal attenuation is larger when the angle between forearm and upper arm increases. The maximum attenuation difference was 4.2 dB and 4.7 dB in the capacitive coupling and galvanic coupling methods respectively when the joint angle changed from 45 to 180 degrees and the linear distance between transmitter and receiver electrodes was 15 cm. Capacitive coupling was more sensitive to limb joint position, but galvanic coupling was more dependent on body composition (intra subject variability).

Modeling of intrabody communication (IBC) entails the understanding of the interaction between electromagnetic fields and living tissues. At the same time, an accurate model can provide practical hints toward the deployment of an efficient and secure communication channel for body sensor networks. In the literature, two main IBC coupling techniques have been proposed: galvanic and capacitive coupling. Nevertheless, models that are able to emulate both coupling approaches have not been reported so far. In this paper, a simple model based on a distributed parameter structure with the flexibility to adapt to both galvanic and capacitive coupling has been proposed. In addition, experimental results for both coupling methods were acquired by means of two harmonized measurement setups. The model simulations have been subsequently compared with the experimental data, not only to show their validity but also to revise the practical frequency operation range for both techniques. Finally, the model, along with the experimental results, has also allowed us to provide some practical rules to optimally tackle IBC design.

Intra-body communication (IBC) is a communication system that uses human body as a signal transmission medium. From previous research, two coupling methods of IBC were concluded which are capacitive coupling and galvanic coupling. This paper investigates the effect of human movement on IBC using the galvanic coupling method. Because the human movement is control by the limb joint, the knee flexion angle during gait cycle was used to examine the influence of human movement on galvanic coupling IBC. The gait cycle is a cycle of people walking that start from one foot touch the ground till that foot touch the ground again. Frequency range from 300 kHz to 200MHz was swept in order to investigate the signal transmission loss and the result was focused on operating frequency 70MHz to 90MHz. Results show that the transmission loss varies when the knee flexion angle increased. The highest loss of signal at frequency range between 70MHz to 90 MHz was 69dB when the knee flexion angle is 50° and the minimum loss was 51dB during the flexion angle is 5°.

Devices for long-term measurement of the electrocardiogram (ECG) provide means to detect sporadic cardiac arrhythmiae such as atrial fibrillation. While ECG devices with galvanic coupling between body and electrodes have a limited wearing time due to drying out and can cause skin irritation, capacitive coupling is not limited in these respects and can thus increase wearing comfort and measurement time of ECG monitoring systems. For integration into daily life, however, robustness against physical activity is a crucial requirement for such devices. We here evaluate the effect of body motion on ECG signal quality for a recently proposed device.The ECG was measured in seven subjects during phases of movement of different parts of the body and compared to a commercial reference ECG device with galvanic coupling. Data quality was assessed in terms of sensitivity and precision of R-peak detection with the established Pan-Tompkins algorithm.The signals were corrupted by both high-frequency disturbances as well as strong baseline variations, which lead to 33% of R-peaks being missed in average. These disturbances were most pronounced during full-body movement as well as tension of the chest muscles, whereas signal quality was hardly affected during leg movement. During moderate activity, precision ranged between 92% and 70%. Of the false negative classifications 43% in average were due to baseline variations causing sensor overload. Furthermore, a strong inter-subject variation was observed.It is argued that the observed motion artifacts, particularly strong baseline variations, are due to changes in contact impedance of the measurement electrodes. In order to provide usability of the capacitive ECG device in daily life, these asymmetries in contact impedance have to be counteracted, particularly by flexible electrode design.

General drive power supply can not meet the requirements of high-voltage isolation under high-voltage and high-frequency (HV-HF) conditions, and the larger coupling capacitance of general power supply will bring common-mode noise. In this paper, a 10kV isolation power supply with 1.55pF low coupling capacitance and multiple output is designed. The power supply adopts LCL-T resonant circuit to produce a 100kHz current source. The current transformer is used to isolate the power supply, which realizes high voltage isolation and small coupling capacitance. The number of output circuits is changed by increasing or decreasing the magnetic core.

The use of capacitive coupling has the potential of reducing the size and cost in the implementation of auxiliary power supplies. This is particularly advantageous in applications with medium-voltage (MV) ac feeders, where this arrangement can avert the use of a high-voltage transformer. The current standard for voltage control in this type of power supply is shunt regulation. This scheme maintains a low dc bus voltage, which increases the current demand through the input capacitors and, hence, decreases the power factor (PF). Switching regulation allows operation at a relatively high intermediate dc bus voltage that can improve the PF, in addition to providing galvanic isolation and achieving higher efficiencies. However, this type of regulation has not been thoroughly explored in the literature of capacitively coupled power supplies. This article presents a novel mathematical model to describe high-frequency switching dc-to-dc regulation in a power supply capacitively coupled to an MV input. The model is used in a case study for the design of a 50-W/12-V (dc) supply fed from a 1-kV (rms)/50-Hz ac input. The results of the design validate the model and demonstrate the advantages of the novel concept.

A capacitive power coupler has been devised using a hydrodynamic journal bearing assembly that facilitates sufficient coupling for kilowatt-scale non-contact power transfer to a rotating load. The capacitive coupler, combined with associated driving circuitry, is an efficient low maintenance solution for powering a variety of rotating or pivoting electrical loads in machines and automation. A hydrodynamic journal bearing capacitor assembly utilizing an ultra-thin cushion of lubricant as dielectric between concentric capacitor electrodes is presented. Hydrodynamic operation ensures high coupling capacitance, ease of manufacturability and eliminates brush and slip ring maintenance. The system's small size, weight, and simplicity are competitive with contemporary inductive wireless power transfer methods in this small gap application. Experimental results for a ~5nF prototype coupler operating at 840 kHz are presented.

In this paper, we propose a simple, but accurate propagation model through the skin based on a RGC distributed-parameter circuit that leads to the obtaining of simple and general attenuation expressions for both galvanic and capacitive coupling methods that could assist in the design of Intra-body Communications (IBC) systems. The objective of this model is to study the influence of the skin impedance in the propagation characteristics of a particular signal. In order to depict that skin impedance, the model is based on the major electro-physiological properties of the skin, which also allows a personalized model. Simulation results have been successfully compared with several published results, thus showing the tuning capability of the model to different experimental conditions.

ABSTRACTRenovation of water and central heating pipelines is a very costly and time‐consuming process; therefore, a way to prioritize the limited resources between different parts of the systems is very important. The risk for corrosion damage can be assessed from the resistivity of the ground, because the processes facilitating the metal oxidation also affect the resistivity. However, galvanic resistivity mapping is time consuming and work‐intensive in paved areas. To determine the resistivity in the vicinity of pipes two different resistivity methods were applied: electrical resistivity tomography using galvanic coupling, and the logistically easier and rapid electrostatic measurements using capacitive coupling. The two methods were tested in a series of experiments undertaken in the province of Scania in southern Sweden with the aim to acquire a better knowledge about the electrical resistivity of the soil surrounding the heating and water distribution pipes, in order to better assess the corrosivity of the environment. From the experiments it is shown that the electrical resistivity tomography and electrostatic methods mostly give comparable results for the shallow investigated depths in focus here, where differences might be caused by different sensitivities and noise characteristics. In the case of both methods, it is shown, with the help of modelling of the different expected ground models including the pipes, that the pipes only influence the data in cases of pipes of very large diameters or those buried at a very shallow depth, even without any protective surface coating. The missing influence of the pipes on the data makes the methods very applicable for knowing the resistivity of the soil surrounding the pipes and thus evaluation of corrosion risk.

The emerging intra-body communication (IBC) and networking system is a prospective component in advancing healthcare delivery and empowering the development of future medical monitoring systems. Using the human body as a transmission medium unfastened the research perspective towards Human Body Communication which has been introduced by the IEEE as a third physical layer. Generally, there are two approaches of HBC, namely, capacitive coupling and galvanic coupling. In this paper, the concept of galvanic coupling is adopted as a method for wireless transmission inside the human body. Then, the channel characteristics of the HBC based on the IEEE 802.15.6 standards are addressed where we focus on both the frequency response and the noise characterization. The results obtained are necessary for developing a realistic human-body channel model capable of estimating the performances of wearable systems using HBC technology.