Hyoungsuk Yoo

Biotelemetry and Wireless Powering for Leadless Pacemaker Systems

In this letter, we address the telemetry and wireless powering problems associated with the recently invented leadless pacemaker. To overcome the telemetry problem, we propose a conformal spiral type Implantable antenna at Medical Implanted Communication Service (MICS) band. In addition, we also apply the recently proposed midfield wireless power transfer (WPT) technique at 1.5 GHz to avoid the bulky energy storage component. We simulate and experimentally measure the performance of the implantable antenna by using porcine heart tissue. Our research shows that, the implantable antenna and wireless power transfer scheme can be implemented in a leadless pacemaker without any significant coupling between them.

A Multiband Antenna Associating Wireless Monitoring and Nonleaky Wireless Power Transfer System for Biomedical Implants

This paper presents a multiband conformal antenna for implantable as well as ingestible devices. The proposed antenna has the following three bands: medical implanted communication service (MICS: 402–405 MHz), the midfield band (1.45–1.6 GHz), and the industrial, scientific, and medical band (ISM: 2.4–2.45 GHz) for telemetry or wireless monitoring, wireless power transfer (WPT), and power conservation, respectively. A T-shaped ground slot is used to tune the antenna, and this antenna is wrapped inside a printed 3-D capsule prototype to demonstrate its applicability in different biomedical devices. Initially, the performance of the proposed antenna was measured in an American Society for Testing and Materials phantom containing a porcine heart in the MICS band for an implantable case. Furthermore, to stretch the scope of the suggested antenna to ingestible devices, the antenna performance was simulated and measured using a minced pork muscle in the ISM band. A modified version of the midfield power transfer method was incorporated to replicate the idea of WPT within the implantable 3-D printed capsule. Moreover, a near-field plate (NFP) was employed to control the leakage of power from the WPT transmitter. From the simulation and measurements, we found that use of a ground slot in the implantable antenna can improve antenna performance and can also reduce the specific absorption rate. Furthermore, by including the NFP with the midfield WPT transmitter system, unidirectional wireless power can be obtained and WPT efficiency can be increased.

Multi-Band Antenna System for Skin Implant

In this letter, two skin-implantable biotelemetry devices are presented along with an antenna system that operates on five bands, including the Medical Implant Communication Service (MICS) (402-405 MHz) and the Industrial, Scientific, and Medical (ISM) (433.1-434.8 MHz, 868.0-868.6 MHz, 902-928 MHz, 2400.0-2483.5 MHz) bands. A link budget analysis was used to configure an algorithm for effective device operation. These devices contain space for storage batteries, controlling electronics, and bio-sensors, along with a planar inverted-F antenna (PIFA), and have total volume of 617 and 510 mm3 respectively. These devices were primarily designed and simulated in different environments with FDTD software. In addition, the performance of the antenna system was evaluated from measurements made inside a skin-mimicking semi-solid homogeneous phantom. This research shows that multi-channel communication will enhance the diversity of biotelemetry devices.

shimming with SAR reduction in high-field MRI

In high-field magnetic resonance imaging systems, parallel excitation with a multi-channel transmitter and receiver has been widely investigated to mitigate inhomogeneity. Multi-channel RF coils employed in the parallel imaging may alleviate the non-uniformity in the field and each element can be independently controlled by adjusting the phase and amplitude of the excitation. In this paper, convex optimization for each coil elements to homogenize and to reduce E fields is proposed. Improved homogeneity and reduced specific absorption rate over the whole field of view is achieved.

A Wideband Circularly Polarized Conformal Endoscopic Antenna System for High-Speed Data Transfer

In this paper, a conformal wideband circularly polarized (CP) antenna is presented for endoscopic capsule application over the 915-MHz Industrial, Scientific, and Medical (902–928 MHz) band. The thickness of the antenna is only 0.2 mm, which can be wrapped inside a capsule’s inner wall. By cutting meandered slots on the patch, using open-end slots on the ground, and utilizing two long arms, the proposed antenna obtains a significant size reduction. In the conformal form, the antenna volume measures only 66.7 mm3. A single-layer homogeneous muscle phantom box is used for the initial design and optimization with parametric studies. The effect of the internal components inside a capsule is discussed in analyzing the antenna’s performance and to realize a more practical scenario. In addition, a realistic human body model in a Remcom XFdtd simulation environment is considered to evaluate the antenna characteristics and CP purity, and to specify the specific absorption rate limit in different organs along the gastrointestinal tract. The performance of the proposed antenna is experimentally validated by using a minced pork muscle phantom and by using an American Society for Testing and Materials phantom immersed in a liquid solution. For measurements, a new technique applying a printed 3-D capsule is devised. From simulations and measurements, we found that the impedance bandwidth of the proposed antenna is more than 20% and with a maximum simulated axial ratio bandwidth of around 29.2% in homogeneous tissue. Finally, a wireless communication link at a data rate of 78 Mb/s is calculated by employing link-budget analysis.

Wireless power transfer to a pacemaker by using metamaterials and Yagi-Uda antenna concept

Wireless power transfer (WPT) to medical implants allows clinicians to avoid using bulky energy storage components. In this paper, we address WPT systems for a pacemaker (PM). A resonant inductive coupling method was employed in the WPT system by introducing a spiral transmitter (Tx) coil and a spiral receiver (Rx) coil. Here, we introduced the concept of the Yagi-Uda antenna by using metamaterials (MTMs) in order to increase WPT efficiency in the Medical Implanted Communication Service (MICS). Based on the simulation results in a realistic model of the human body, we were able to design a compact and efficient WPT system for PMs. Moreover, our simulation results showed that the Yagi-Uda antenna configuration can significantly increase WPT efficiency.

Miniaturized scalp-implantable antenna for wireless biotelemetry

In this study, we present a scalp implantable miniaturized biocompatible antenna at the medical implant communication service (MICS) band (402-405 MHz). The antenna dimension is only 26.4 mm3 (11 mm × 8 mm × 0.3 mm) which is an electrically small antenna. It provides a monopole like radiation pattern with radiation efficiency of 1.9%, -10dB impedance band-width of 42MHz and gain of -42.21 dB. These results are achieved when it is implanted in skin tissue of a human head model at 5mm depth. To reduce simulation time, initially the antenna was placed in a skin tissue simulating box of 5mm implant depth. For simulation in skin tissue box, Ansofts EM simulator HFSS and for human head implantation, SEMCAD X FDTD software was used.

Wireless power transfer and biotelemetry in a leadless pacemaker

In this paper, we address the telemetry and wireless powering problems associated with the recently invented leadless pacemaker. To overcome the telemetry problem, we propose a conformal spiral type Implantable antenna at Medical Implanted Communication Service (MICS) band. In addition, we also apply the recently proposed midfield wireless power transfer (WPT) technique at 1.5 GHz to avoid the bulky energy storage component. We simulate and experimentally measure the performance of the implantable antenna by using porcine heart tissue. Our research shows that, the implantable antenna and wireless power transfer scheme can be implemented in a leadless pacemaker without any significant coupling between them.

Broadband Tunable Third-Order IMD Cancellation Using Left-Handed Transmission-Line-Based Phase Shifter

We demonstrate a broadband tunable third-order intermodulation distortion (IMD) cancellation architecture using a left-handed transmission line (LHTL)-based phase shifter for a feedforward amplifier. The fabricated circuit reduces the third-order IMD of the main amplifier up to 17 dB after adjusting for any frequencies between 1.5 and 2.4 GHz when the frequency difference between the two tones is 2 MHz. In addition, the circuit maintains a spurious-free dynamic range that is greater than 55 dBc at the output. This effective broadband third-order IMD cancellation method is possible because of the broadband and linearly phase-tunable characteristics of the LHTL-based phase shifter.

A Method to Identify the Identification Eye Status for Drowsiness Monitoring System

This paper describes a method for detecting the pupil region and identification of the eye status for driver drowsiness detection system. This program detects a driver’s face and eyes using viola-jones face detection algorithm and extracts the pupil area by utilizing mean values of each row and column on the eye area. The proposed method uses binary images and the number of black pixels to identify the eye status. Experimental results showed that the accuracy of classification eye status(open/close) was above 90%.