Search

One of the important safety aspects regarding electromagnetic fields is their coupling with medical implants in the human body. In this article, an adult model (Ella), with different medical implants, was exposed to a leaked magnetic field from a wireless power transfer (WPT) system in an electric vehicle, operating at a frequency of 85 kHz, with transferred powers of 3.7, 7.7, 11, and 22 kW. The induced electric field ( E -field) in the human model, standing close to the vehicle and sitting inside the vehicle, was evaluated with a prosthetic hip implant, an interlocking nail implant, an InterStim neurostimulator implant, a traditional pacemaker implant, and a leadless pacemaker implant. The results indicated that medical implants influenced the maximum magnitude of the induced E -field and its distribution inside the body. A notable enhancement in the E -field was observed around the implants. In worst-case scenarios, the effects of implant shape and size were investigated. The highest induced E -field (12.68 V/m) was observed with the interlocking nail of length 340 mm for standing posture, which exceeded the prescribed limit of 11.5 V/m in the International Commission on Non-Ionizing Radiation Protection guidelines. The presence of a medical implant in the body likely limits the transferred power of the WPT system, depending on the implant type, size, location, and the body posture.

Advancement in the technology of leadless cardiac pacemakers (LCPs) has led to ultracompact designs of implantable antennas. In this study, a small-sized antenna for integration with an LCP, which can be operated in the industrial, scientific, and medical (ISM) band of 2.4 GHz, is developed. The proposed antenna was constructed in a spiral shape to provide superior miniaturization, less sensitivity to body tissue variation, and low specific absorption rate (SAR) values, and avoid fabrication complexities due to its small size. The antenna with a footprint of $3 \times 4\,\,\times0.5$ mm3 was constructed on a high dielectric material, namely, Rogers RT/duroid 6010. To the best of the authors’ knowledge, this is the smallest footprint with enhanced performance when compared to previous reports related to implantable antennas. In addition, the antenna was integrated with a 3-D printed LCP having dummy electronics and experimentally validated in saline solution and minced pork. The antenna sustained good impedance matching at the ISM band with a measured bandwidth of 21.88% and 15.46% with the device and without the device, respectively. Due to the smooth electric field (surface currents) over the patch, the antenna system had 270.28 and 31.04 W/kg peak SAR for 1 and 10 g of tissues, respectively, with a maximum peak gain of −25.95 dBi. We also discussed the effects of a coaxial cable and the antenna orientation on its performance. From the measured received signal strength, a stable biotelemetric link can be established between the implant and external controlling device up to a distance of 2 m.

The integration of sub-6-GHz and millimeter-wave (mm-wave) bands has become an important issue for future fifth generation (5G) wireless communications owing to their large frequency ratios. This paper proposes a compact-size dual-function antenna operating at 3.5 GHz and the mm-wave band (28 GHz) for 5G mobile applications using a frequency reconfigurability technique. The proposed antenna comprises a microstrip patch linked with a meandered radiating structure through a radio frequency PIN diode to achieve frequency reconfigurability between the two bands. A significant size reduction up to 15.3 $\text {mm} \times 7.2\,\,\text {mm} \times 0.508$ mm for the proposed antenna was achieved using a meandered line structure and truncated ground plane. To enhance the functionality, $8 \times 8$ multiple-input multiple-output (MIMO) with possible long- and short-edge antenna placement configurations were demonstrated. The system exhibited satisfactory MIMO characteristics with wide decoupling −10 dB bandwidths of 7.4% and 4.8% at the low- and high-frequency bands, respectively, without utilizing any external decoupling structure. The simulated results were validated using fabricated prototypes, and good agreement was observed. Additionally, a safety analysis based on the specific absorption rate and power density at the prescribed frequency bands was conducted using a realistic human model, and the results were found to be in accordance with the safety guidelines. Owing to the integration of sub-6-GHz and mm-wave bands in a single compact structure with a large frequency ratio and good MIMO performance, the proposed antenna system is suitable for future 5G mobile handheld devices.

Numerical dosimetry with regards to a resonance-based wireless power transfer (RBWPT) system for charging electric vehicles (EVs) has been conducted. The RBWPT system operating at 13.56 MHz frequency with a transferred power of 5.3 kW is placed below the center of the vehicle body. Specific absorption rate (SAR) in anatomically-based human models Duke and Ella with and without a medical implant is evaluated using four exposure scenarios (i.e., Duke and Ella models sitting in the EV without an implant, the Ella model: With an InterStim neurostimulator implant, having a prosthetic hip implant, or having a cardiac pacemaker implant). The results indicate that change in radio frequency (RF) energy absorption occurs when conductive implants are placed in the near field of an RF source. Enhancement of the SAR close to the implants is predicted. The peak averaged SAR over 10 g of tissues exceeds the standard limiting value posed by international guidelines except for the leadless pacemaker, which is in compliance with the prescribed limits. However, the temperature increase never exceeds the localized temperature rise limit of 2 °C. Compliance with the recommended limits of SAR in the worst-case exposure scenario is likely to limit the transferred power.

This communication presents a metamaterial (MTM)-loaded compact dual-band circularly polarized antenna system suitable for multiple bio-telemetric applications. The proposed antenna system operates in the industrial, scientific, and medical (ISM) bands with center frequencies: 915 MHz (902–928 MHz) and 2450 MHz (2400–2480 MHz). The integration of an MTM structure with epsilon-very-large property on the superstrate layer of the antenna produces significant gain enhancement and strong circular polarization (CP) behavior at both the operating frequencies. The key features of the proposed antenna system are its compact size (7 mm $\times 6$ mm $\times $ 0.254 mm), dual-band CP characteristics, significantly high gain values (−17.1 and −9.81 dBi in the lower and upper bands, respectively), and slot-less ground plane that reduces the complexity and backscatter radiation. The performance of the MTM-loaded antenna system is validated experimentally. The antenna is fabricated and integrated with dummy electronics and batteries and is enclosed in a 3-D printed device. The hermetically sealed device is tested in minced pork muscle to validate the simulation results. The measured impedance bandwidths of 35.8% and 17.8% are obtained in the lower and upper ISM bands, respectively. The specific absorption rate of the antenna system is evaluated at both frequencies in different tissues. Additionally, to determine the wireless communication range, the link margin is estimated at data rates of 100 kbps and 1 Mbps.

In the present research article, a modified analytical method is applied to solve time-fractional telegraph equations. The Caputo-operator is used to express the derivative of fractional-order. The present method is the combination of two well-known methods namely Mohan transformation method and Adomian decomposition method. The validity of the proposed technique is confirmed through illustrative examples. It is observed that the obtained solutions have strong contact with the exact solution of the examples. Moreover, it is investigated that the present method has the desired degree of accuracy and provided the graphs closed form solutions of all targeted examples. The graphs have verified the convergence analysis of fractional-order solutions to integer-order solution. In conclusion, the suggested method is simple, straightforward and an effective technique to solve fractional-order partial differential equations.

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 mm3 (7 mm $\times6.5$ mm $\times0.377$ mm). A significant size reduction for the antenna is achieved by using a spiral-shaped 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.