Showing papers by "Jianqing Wang published in 2021"

Field Uniformity Assessment of a Reverberation Chamber for a Large-Scale Animal Study

Abstract: An exposure system was designed and implemented for the purpose of joint large-scale animal experiments conducted in Korea and Japan using a reverberation chamber (RC) in both countries. Prior to the start of the animal experiments, the parameters S21, electric field (E-field) uniformity, and Q factor were evaluated to confirm the performance of the developed chambers. The E-field uniformity, which is the most important performance factor of an RC, was evaluated at 900 MHz on 150 measurement values taken at 150 points in a loaded chamber with 80 live rats and in an empty chamber. The conditions of the loaded chamber with the rats are almost the same as the actual experimental environment and in which the rats, watering systems, animal bedding, cages, and cage racks were included. Two mean body weights of 330 and 470 g for the 80 rats were considered. The E-field uniformity was within the mean ± 1.0 dB and mean ± 2.3 dB under the empty and the rat-loaded conditions, respectively.

Path Loss Analysis and Transceiver Development for Human Body Communication-Based Signal Transmission for Wearable Robot Control

Abstract: Human body communication (HBC) technology is attracting a lot of attention for monitoring vital data and controlling wearable robot In this paper, we focused on electroencephalogram (EEG) signal transmission from head to wrist in the 10–60 MHz HBC band This is based on an idea to transmit an EEG signal to control a wearable robot First, we clarified the basic transmission mechanism and characteristics using a highly simplified human body model Next, we performed a detailed path loss analysis by finite difference time domain simulation using an anatomical human body model with various postures Based on the analysis results, we identified the optimum transmitter position on the head and developed an impulse radio transceiver for verifying the feasibility of the technique The results show that the developed transceiver can provide a data rate of 10 Mbps and the bit error rate can be kept below 10−3 for transmitting the EEG signals from the head to the wrist Experimental validation with a bio-equivalent gel phantom also demonstrated high feasibility of transmitting the EEG signals along the human arm

Localization Method for Implant Devices Using Electromagnetic Scattering Based on Sparse Reconstruction

Abstract: Herein, we propose a localization method for implant devices using electromagnetic scattering based on sparse reconstruction. We define the product of the total electric field and the complex relative permittivity as a new unknown variable, which is expected to be sparse. Computer simulations are conducted to validate the sparsity of the estimated variable, and localization errors are evaluated to confirm the performance improvement using the sparsity-based localization method. The result confirmed the excellent localization performance, particularly below 17 MHz, even under low signal-to-noise power ratios.

Directive Antenna Design at 2.4 GHz on Foot Surface for Wanderer Location Identification

Abstract: A directional patch array antenna was designed for wanderer location identification. The antenna was used for foot-mounted BLE beacons at 2.4 GHz band. Its directional performance was evaluated by simulation and it was found that the antenna can sweep diagonally upward from 7° to 35°.

Non-Contact Heart-Rate Measurement Method Using Both Transmitted Wave Extraction and Wavelet Transform

Abstract: Continuous monitoring of heart-rate is expected to lead to early detection of physical discomfort. In this study, we propose a non-contact heart-rate measurement method which can be used in an environment such as driver heart-rate monitoring with body movement. The method is based on the electric field strength transmitted through the human body that changes with the diastole and systole of the heart. Unlike conventional displacement detection of the skin surface, we attempted to capture changes in the internal structure of the human body by irradiating the human body with microwaves and acquiring microwaves that pass through the heart. We first estimated the electric field strength transmitted through the heart using three receiving sensors to reduce the body movement effect. Then we decomposed the estimated transmitted electric field using stationary wavelet transform to eliminate significant distortion due to body movement. As a result, we achieved an estimation accuracy of heart-rate as high as 98% in a verification experiment with normal body movement.

A New Wide-Area Monitoring System of Electromagnetic Fields Around Megawatt-Class Amplifiers for Ion Cyclotron Range of Frequency Heating at a Fusion Test Facility

Abstract: Nuclear fusion research requires the production of high-temperature plasma. One of the plasma heating methods is the use of radio frequency (RF) waves. The RF wave heating system uses a high-power amplifier, which poses a concern about the leakage electromagnetic fields. Therefore, a new wide-area multipoint electromagnetic monitoring system using personal RF monitors has been developed. The developed monitoring system was applied to the megawatt-class amplifiers for the “ion cyclotron range of frequency” (ICRF) heating system in the frequency range of ion cyclotron resonance from 30 to 40 MHz. As a result, the leakage magnetic field was less than the measurement sensitivity during the plasma experiment, in which the leakage electric field was detected with sufficient sensitivity. The leakage electric field becomes larger as the RF forward power increases, and thus the electric field would be radiated through the stub and/or high voltage supply line connected to the anode of tetrode in the ICRF amplifier. The electric field around the ICRF amplifiers did not exceed the reference level of International Commission on Non-Ionizing Radiation Protection (ICNIRP). The developed wide-area multipoint monitoring system will be useful for monitoring the leakage RF electromagnetic fields around the ICRF heating system at the future fusion devices.

Design and evaluation of directional antenna for shoe-mounted sensor for position identification of elderly wanderer

Abstract: Monitoring system with Bluetooth low energy (BLE) beacons is promising for position identification of elderly wanderers. BLE beacons can be mounted in shoes for convenience, and a shoe-mounted directional antenna is expected to efficiently radiate the beacon signals to the data server of the monitoring system. In this paper, a directional array antenna with planar or curved structure was designed on the shoe surface for this purpose. The antenna was designed to sweep diagonally upward from 10° to 50°, and the simulated and measured S11 performances revealed reasonable agreement. The antenna was assumed to be used in an urban environment, and a directional patch array antenna with dielectric lens was also designed to receive beacon signals by mounting it on utility poles. According to a feasibility experiment result of elderly wanderer position identification, the designed directional antenna can provide an almost 100% position identification rate if a wanderer is within 20 m from a smart phone user.