Quality Factor Optimization of Inductive Antennas for Implantable Pressure Sensors

IEEE Transactions on Biomedical Circuits and Systems, 2000

An approach based on multi-layer spiral inductors to remotely power implantable sensors is investigated. As compared to single-layer inductors having the same area, multi-layer printed inductors enable a higher efficiency (up to 35% higher) and voltage gain (almost one order of magnitude higher). A system conceived to be embedded into a skin patch is designed to verify the performance. The system is able to transmit up to 15 mW over a distance of 6 mm and up to 1.17 mW where a 17 mm beef sirloin is placed between the inductors. Furthermore, the system performs downlink communication (up to 100 kbps) and uplink communication based on the backscattering technique (up to 66.6 kbps). Long-range communication is achieved by means of a bluetooth module.

IEEE Transactions on Biomedical Engineering, 2006

A versatile orthogonal-coil radio frequency (RF) probe suitable for detecting the resonant frequency of miniature implantable passive sensors has been designed and tested. The probe sensitivity has been tested using printed-circuit spiral inductors of various sizes (3-15 mm) in series with discrete surface-mount capacitors designed to resonate over a range of frequencies (50-200 MHz). Close agreement between theoretical calculations and experimental results has been obtained. An equation is derived for transmit/receive (T/R) isolation that agrees with experimental measurements over the frequency range 1-500 MHz. The probe includes an additional coil to compensate for the effect of eddy currents in the human body on the probe. T/R isolation of at least 90 dB over the frequency range 1-100 MHz can be achieved when the probe is placed in close proximity to the human body.

International Journal of Electrical and Computer Engineering (IJECE), 2019

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 (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 2 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 = 300Ω, 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.

2014 Global Summit on Computer & Information Technology (GSCIT), 2014

Electronic biomedical implantable devices need powering to perform. Among the main reported approaches, inductive links are the most commonly used method for remote powering of such devices. Power efficiency is the most important characteristic to be considered when designing inductive links to transfer energy to implantable devices. The maximum power efficiency is obtained for maximum coupling and quality factors of the coils and is generally limited as the coupling between the inductors is usually very small. This paper is dealing with geometry optimization of inductively coupled printed spiral coils for the powering of a given implant system. For this aim, simple mathematical models that approximate coil parameters and link efficiency are derived, and using these models two different approaches are used to provide optimal coil geometries for a maximum efficiency of the link. First an iterative design procedure is implemented then genetic based algorithm optimisation is derived to find the optimal coil geometries of the used coil structure. Theoretical results are verified by simulation using HFSS software. A comparative analysis confirmed the effectiveness of the genetic algorithm based approach to provide the optimal coil geometries.

Engineering and Technology Journal

The efficiency of a WPT system greatly depends on both the geometry and operating frequency of the transmitting and receiving structures. Genetic optimizations algorithms are presented to prepare the proposed design parameters using MATLAB to optimize the link efficiency. Single and double layer PSCs are optimally designed with minimal proximity losses effect. In this paper, we used the benefit of a double layer technique to miniaturize the receiver PCS size. The proposed single layer (10×10) mm2 and double layer (8×8) mm2 PSCs are validated and simulated using HFSS 15.03 software at a frequency of 13.56MHz in both cases of the air, and human biological skin tissue as intermediate material between the transmitter and receiver PSCs. The calculated and simulated results of both proposed receiver PSCs are compared for both cases of intermediate materials for their efficiency behaviors. The results show that in the case of biological tissue, the deterioration in PTE using 8mm double lay...

Progress In Electromagnetics Research C, 2018

In this paper, we present a hybrid system consisting of a novel microstrip antenna that can be designed to resonate at various frequencies within the ultra-high frequency (UHF) band (e.g., 415 MHz, 905 MHz, and 1300 MHz), combined with a pair of high frequency (HF) coils (13.56 MHz). The system is designed to be fabricated on an FR4 substrate layer, and it provides a compact solution for simultaneous wireless power transfer (WPT) and multi-band wireless communication, to be utilized in implanted medical devices. The external antenna/coil combination (EX) will be located outside the body on the skin layer. The EX has 79.6 mm-diameter. The implanted hybrid combination (IM) has 31.5 mm-diameter. The antenna is designed such that by varying the position of a shorting pin the resonance frequency can be changed among three frequencies; therefore, the same design can be used for various applications. The system was designed using numerical simulation tools, and then it was fabricated and measured. The design was optimized while the performance of the system was numerically simulated at various depths inside a layered body model. Furthermore, the insertion loss (S 21) and transmission efficiency (η) for both antenna and coil pairs at different depths were studied through simulation and measurements. The system provides a good solution for the combination of power transfer and multi-band data communication.

sonnetsoftware.com

Inductive power transfer is the most common method for transferring power to implantable sensors inside human body. For good inductive coupling, the inductors should have high inductance and high quality factor. But the physical dimension of the receiver inductor cannot be large due to biomedical constraints. Therefore, there is a need for small size and high inductance, high quality factor inductors for implantable sensor applications. In this work, design of a multi-spiral solenoidal inductor for biomedical application is presented. The inductors are simulated and optimized for targeted application using a commercial electromagnetic tool, Sonnet. Parametric study of the multi-spiral inductor is investigated in terms of number of layers, metal spacing, and metal width. Finally, it is demonstrated that the proposed multi-spiral solenoidal inductor exhibits a better overall performance in comparison with the conventional spiral inductors for biomedical applications.

This paper presents a miniature wireless energy transfer system design for implantable pressure sensor used for health monitoring applications. The implantable pressure sensor can be wirelessly powered through strongly coupled magnetic resonance based wireless energy transfer system. The wireless power transfer system has been built up by using a power transmitting circuit which will be placed outside the body and a receiving unit connected to the implantable pressure sensor to be kept inside the body. Experimentally, it has been found that the wireless power transfer from the transmitting coil to the implantable receiving coil depends on the operating frequency, separation distance between the coils and configuration of the coils. It has been found that maximum wireless power transfer occurs from the transmitting unit to the implantable receiving unit at the operating resonant frequency of the system. At the resonant frequency of 562 kHz and optimum load of 40 Ω, a maximum power of 0.186 W and energy transfer efficiency of 26% have been achieved wirelessly with a separation distance of 3 cm between the transmitter and receiver resonators. Electromagnetic simulation has also been carried out using the different forms of transmitting and receiving coils in order to obtain a strong magnetic coupled wireless energy transfer system, which plays an important role in the energy transfer efficiency.

International Journal of Antennas and Propagation

Minimally invasive approach to intracranial pressure monitoring is desired for long-term diagnostics. The monitored pressure is transmitted outside the skull through an implant antenna. We present a new miniature (6 mm × 5 mm) coplanar implant antenna and its integration on a sensor platform to establish a far-field data link for the sensor readout at distances of 0.5 to 1 meter. The implant antenna was developed using full-wave electromagnetic simulator and measured in a liquid phantom mimicking the dielectric properties of the human head. It achieved impedance reflection coefficient better than −10 dB from 2.38 GHz to 2.54 GHz which covers the targeted industrial, scientific, and medical band. Experiments resulted in an acceptable peak gain of approximately −23 dBi. The implant antenna was submerged in the liquid phantom and interfaced to a 0.5 mW voltage controlled oscillator. To verify the implant antenna performance as a part of the ICP monitoring system, we recorded the radiat...

Microelectronic Engineering, 2014

A micro-fabrication process is proposed to realize high-thickness spiral inductors for the remote powering of implantable biosensors through inductive link. The process is suitable for different substrates, such as silicon and Pyrex, and enables the fabrication of the receiving inductor directly on the implantable system. The use of Ordyl Alpha960 is explored to achieve high-thickness structures. Ordyl is a dry film, negative photoresist that enables high-thickness mold (starting from 60 lm) with a single-layer deposition. Copper spiral inductors with a trace thickness of 60 lm are fabricated on silicon and tested. These inductors can receive up to 8.7 mW, with a link efficiency of 25%, over a distance of 6 mm from the transmitter. Tested within a real setup, these inductors enable bidirectional data communication with the external transmitter. Downlink communication (ASK) is successfully tested at 100 kbps. Uplink communication (LSK) is successfully tested at 66.6 kbps.

Advances in Intelligent Systems and Computing, 2021

This paper presents an analytical design approach for planar inductor-capacitor (LC) circuits for biomedical wireless power transfer (WPT) applications. This research makes use of the resonant inductive coupling between a transmitter and receiver coil in a series-parallel topology. The micro-electromechanical systems (MEMS)-based LC circuits are operated within a frequency range of 10-300 MHz. Several design cases are realized by varying the values of the number of turns, line width, and spacing width of the coil, while maintaining resonant frequency ranges circuits sizes that are compatible with biomedical applications and MEMS fabrication standards. In addition, the effects of such variations on the resonant frequency and quality factor are investigated. The findings of this paper present a simple approach to achieve different design requirements of planar LC circuits in WPT applications.

IEEE Transactions on Antennas and Propagation

In this communication, a multiband spiral-shaped implantable antenna for scalp implantation and leadless pacemaker systems is presented. The proposed antenna has the following operational bands: medical implanted communication service (MICS) (402-405 MHz), industrial, scientific, and medical (ISM) (433.1-434.8 MHz and 2400-2483.5 MHz), and midfield (1520-1693 MHz). The recommended antenna system consists of two implantable devices: a flat-type scalp implantable device and a capsule-type leadless pacemaker. In each device, the antenna is integrated with controlling electronic components and a battery. The proposed antenna has a compact size of 17.15 mm 3 (7 mm × 6.5 mm × 0.377 mm). A significant size reduction for the antenna is achieved by using a spiralshaped radiator with two symmetrical arms and introducing an open-end slot in the ground. The key features of the proposed antenna are its compact size, vialess ground plane, multibands, wide bandwidth, and satisfactory gain values compared to other implantable antennas. The maximum realized gain values of the proposed structure are −30.5, −30, −22.6, and −18.2 dBi at 402, 433, 1600, and 2450 MHz, respectively. The design and analysis of the antenna are carried out with simulators, based on the finite-element method (FEM) and the finite-difference time domain (FDTD). The performance of the antenna is experimentally validated using a saline solution and minced pork muscles. Moreover, the specific absorption rate (SAR) distributions at all frequencies induced by the implantable antenna are evaluated. In addition, a wireless communication link budget is calculated to specify the range for biotelemetry at data rates of 7 and 100 kb/s.

TEM Journal

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 t...

IEEE Transactions on Biomedical Circuits and Systems, 2000

The paper presents a compact planar antenna designed for wireless sensors intended for healthcare applications. Antenna performance is investigated with regards to various parameters governing the overall sensor operation. The study illustrates the importance of including full sensor details in determining and analysing the antenna performance. A globally optimized sensor antenna shows an increase in antenna gain by 2.8 dB and 29% higher radiation efficiency in comparison to a conventional printed strip antenna. The wearable sensor performance is demonstrated and effects on antenna radiated power, efficiency and front to back ratio of radiated energy are investigated both numerically and experimentally. Propagation characteristics of the body-worn sensor to on-body and off-body base units are also studied. It is demonstrated that the improved sensor antenna has an increase in transmitted and received power, consequently sensor coverage range is extended by approximately 25%.

IEEE Transactions on Circuits and Systems I: Regular Papers, 2013

Wireless power transfer provides a safe and robust way for powering biomedical implants, where high efficiency is of great importance. A new wireless power transfer technique using optimal resonant load transformation is presented with significantly improved efficiency at the cost of only one additional chip inductor component. The optimal resonant load condition for the maximized power transfer efficiency is explained. The proposed technique is implemented using printed spiral coils with discrete surface mount components at 13.56 MHz power carrier frequency. With an implantable coil having an area of 25 mm 10 mm and a thickness of 0.5 mm, the power transfer efficiency of 58% is achieved in the tissue environment at 10-mm distance from the external coil. Compared to previous works, the power efficiency is much higher and the structure is compact with planar integration, easy to tune, and suitable for batch production, as well as biocompatible owing to no incorporation of ferromagnetic core. Index Terms-Implantable biomedical devices, inductive power transmission, load transformation, resonant coupling, wireless power transfer.