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2022 Vol. 31, No. 1

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A Review of Implant Intra-Body Communication
Maoyuan Li, Yong Song, Xu Zhang, Yu Chen, Chenqiong Tang
2022, 31(1): 1-29. doi:10.15918/j.jbit1004-0579.2021.076
Abstract:
With an extending life expectancy and demand for medical healthcare, there are widespread and stringent requirements of implantable medical devices (IMDs) development for diagnostics, treatments, and therapies by emerging technologies. One of the primary targets for the IMDs is evolving a reliable, speed, and accurate communication method to provide proactive wellness management and thereby achieve early detection, disease prevention, and even treatments. Intra-body communication (IBC) is a potential technology envisioning a sensors/actuators network within a human body, which uses the conductive properties of a body and is categorized in the standardized IEEE 802.15.06 protocol. In the present review, the current state-of-art of implant intra-body communication has been surveyed. Based on the propagation mechanisms over investigated IBC spectrum (i.e., 0.1 MHz –100 MHz), the capacitive and galvanic coupling IBC is considered, where the subfields regarding modeling method (including circuit, numerical, analytical, and filter model), measurement details (including the effect of the electrode, cable, impedance, and instrument), clinical application (including cardiac pacemaker and wireless endoscope), transceiver design (including discrete component and CMOS technology) and media access control (MAC) layer design have been introduced or discussed. Furthermore, the open challenges and issues have been explored as an anticipated inspiration for future development.
Comparative Study on Galvanic-Coupled Intrabody Channel Characteristic Measurement Methods
Yangrong Wen, Fengjie Lin, Yueming Gao, Sio Hang Pun, Mang I Vai, Min Du
2022, 31(1): 30-38. doi:10.15918/j.jbit1004-0579.2021.080
Abstract:
The galvanic-coupled intrabody communication (GCIBC) uses the human body as the channel for data transmission. The signal flow through different paths within different measurement schemes, resulting in distinct deviations in the experimental results. This method completely uses human body channel to transmit low-power signals, and has good anti-interference performance. However, for a long time, the channel research of GCIBC has not determined a set of recognized and accurate measurement methods and standards. However, few researcher analyze the differences and principles between different measurement methods. This paper aims at three commonly used measurement methods. Abstract the equivalent schematic diagrams of three measurement schemes: direct measurement, using high-precision differential probe and using balun. The signal return paths generated by three measurement methods are analyzed, the impedance matching and energy transmission efficiency are compared. According to the analysis, the empirical expressions in different cases are listed. The mechanism between the channel measurement results generated by the set experimental configuration and the comparison experiment is clarified. The comparison experiment with complete floating measurement is carried out as a reference to verify the proposed opinion. The measurement error caused by different experimental configurations is verified. This study can provide a reference opinions for the experimental error analysis of GCIBC research in the future, and provide suggestions for the selection of experimental configuration.
A 2Mbps Human Body Communication Transceiver Based on Body Antenna Effect
Huajie Tang, Pengfei Ao, kun Wang, Yuhang Liu, Jingzhen Li, Abhishek Kandwal, Zedong Nie
2022, 31(1): 39-52. doi:10.15918/j.jbit1004-0579.2021.083
Abstract:
This paper presents a human body communication (HBC) transceiver for wireless body network applications. The transceiver employs on frequency shift keying (FSK) modulation and operates in 40 MHz–60 MHz which is the resonant frequency of the human body as an antenna. It achieves high performance and stability through establish passive microstrip line and via models and active device-models. The proposed transceiver is designed and fabricated by FR4 printed circuit board (PCB) process, the transceiver has the ability of configurable data rate up to 2 Mbps and it achieves –86 dBm receiving sensitivity at 2 Mbps data rate. Meanwhile, the transceiver output power dynamics range is 34 dB. Furthermore, with a visual interaction interface, the transceiver can be agility use in a variety of scenarios. Its measurements are verified on human body. The result shows that the transceiver has ability to send data from person to person by relying on human body antenna radiation. The transceiver shows great prospect in wireless body area networks (WBAN) for telemedicine and emergency communication.
Design of Wireless Power Transfer with High Efficiency for Biomedical Implants
Qingya Li, Zhiwei Zhang, Jingna Mao
2022, 31(1): 53-60. doi:10.15918/j.jbit1004-0579.2021.082
Abstract:
Wireless power transfer (WPT) technology is a popular choice for biomedical implant devices. The demands of higher efficiency and smaller implantation size are hard to compromise in previous studies. In the present work, an implantable magnetic coupling resonant WPT system integrated with a metasurface element working at 430 MHz is presented. Similar planar copper coil components for the transmitting and receiving structures are used to construct the primary system, and then the metasurface element is integrated to constitute the whole WPT system. The effects of the distances between the transmitting coil and skin surface, between the skin surface, and receiving coil are discussed. The results show that the efficiency will be enhanced by 38–50 dB integrating with the metasurface.
A Modeling Method of the IBC System Based on the Composite Fading Channel
Maoyuan Li, Xu Zhang, Yong Song, Yu Chen, Wu Ren
2022, 31(1): 61-70. doi:10.15918/j.jbit1004-0579.2021.075
Abstract:
Intra-body communication (IBC) is a novel short-range non-RF(radio frequency) wireless communication technique specified by the IEEE 802.15.6 using the human body as a transmission medium. In this work, a new modeling method of the IBC system based on the composite fading channel is proposed, where the cascaded filter is used to express the composite fading channel and the modulation method in transmitter and receiver. The composite fading channel combines with the average attenuation, group delay, multipath effect, and shadowing effect. The modulation is adopted orthogonal frequency division multiplexing (OFDM), and thereby the constellation, cyclic prefix, bit error rate, and pilot mode are determined. As a result, the whole process and multi-parameter simulation of IBC system can be achieved. It provides a theoretical foundation for the system design of the intra-body communication and will promote its application to the wireless body area network (WBAN).
A Comparative Study of the Electrodes Gels’ Electrical Properties in the Measurement Issues of Intrabody Communication
Fengjie Lin, Ziliang Wei, Jiejie Yang, Yangrong Wen, Yueming Gao, Sio Hang Pun, Mang I Vai, Min Du
2022, 31(1): 71-80. doi:10.15918/j.jbit1004-0579.2021.085
Abstract:
Intrabody communication (IBC) technology is becoming progressively more standardized due to its low power consumption and high security features incorporated into the third physical layer of the IEEE 802.15.6 standard. Even then, there are still many challenges in normalizing the measurement issues of IBC. A major concern that should not be overlooked is the electrodes in the IBC, especially the popular use of gel electrodes. In the channel measurements, gel electrodes are commonly employed to improve the signal-to-noise ratio and prevent electrodes from falling off. In this paper, a comparative study of the electrical properties of gel was investigated during the measurement of human channel characteristics and to clarify the differences of them. Firstly, the basis of electrostatic field pole plate measurements and electromagnetic theory were introduced to interpretate how the relative permittivity and conductivity of different gels will influence the measurement results. Then the in vivo experiments with different gel or dry electrodes were performed to compare the differences induced by the gel. The results indicate that the influence of the gel on the human channel measurement is mainly concentrated below 400 kHz (the attenuation is reduced by 16.7 dB on average), and the stability of the permittivity and conductivity of the gel has a direct impact on the stability of its measurement of the human channel. This result may provide a meaningful reference for the standardization of electrode usage in IBC.
A Novel Flexible Antenna at Very High Frequency Band for On-Body Applications
Abhishek Kandwal, Huajie Tang, Pengfei Ao, Kun Wang, Jingzhen Li, Yuhang Liu, Tobore Igbe, Zedong Nie
2022, 31(1): 81-90. doi:10.15918/j.jbit1004-0579.2021.077
Abstract:
This paper proposes a novel flexible antenna design operating at very high frequency (VHF) band for on-body applications such as human body communication (HBC). The antenna consists of back-to-back E-shaped fractal and complimentary structures designed over a thin flexible substrate. The overall design working on the principle of fractal geometries and capacitive coupling is highly beneficial to achieve better antenna characteristics even at low frequencies around 35 MHz–45 MHz that are being used for HBC application. The proposed antenna obtained a large bandwidth of around 10.0 MHz in air and a bandwidth of around 8.0 MHz during on-body operation. The antenna has been tested in three different scenarios viz. air, on-body single antenna and on-body communication using two antennas. The insertion loss is reduced to a minimum in all three scenarios, which is quite beneficial for better signal transmission. The size miniaturization with high flexibility in such low frequencies has also been achieved in the paper that makes the proposed design suitable for human body communication applications.
The Wireless Power Transmission on the Wrist-to-Forehead Path Based on the Body Channel
Cheng Han, Linghui Kong, Qingya Li, Shan Yu, Zhiwei Zhang, Jingna Mao
2022, 31(1): 91-100. doi:10.15918/j.jbit1004-0579.2021.084
Abstract:
The body channel based wireless power transfer (BC-WPT) method utilizes the human body as the medium to transfer power for bioelectronics, which can achieve a lower transmission loss due to its higher conductivity. However, except for the channel length, different on-body locations of the transmitter and receiver also influence the power supply performance. This paper focuses on the wrist-to-forehead path to show the potential of BC-WPT for the brain bioelectronics such as the brain computer interface device. The channel characteristics from 10 MHz to 60 MHz are measured by a vector network analyzer (VNA) and a prototype BC-WPT system with different copper electrodes and the lowest power loss locates between –22 dB and –33 dB. Furthermore, the minimum path loss limit is simulated in Advanced Design System (ADS) software and the lowest optimum path loss can reach nearly –13 dB. Finally, a rectifier circuit is also built at the receiver side to harvest d.c. voltage. The results show that the open-circuit voltage (OCV) can reach 1.75 V with the transmitter of 50 $ \text{Ω} $ output impedance supplying 5 $ {V}_{{\rm{pp}}} $ sine voltage at 60 MHz when adopting 1 cm-diameter circular electrodes.
High-Precision Vital Signs Detection Method Based on Spectrum Refinement and Extended DCMA
Mingxu Xiang, Wu Ren, Weiming Li, Zhenghui Xue
2022, 31(1): 101-111. doi:10.15918/j.jbit1004-0579.2021.081
Abstract:
In this paper, the spectral estimation algorithm is extended to the detection of human vital signs by mm-wave frequency modulated continuous wave (FMCW) radar, and a comprehensive algorithm based on spectrum refinement and the extended differentiate and cross multiply algorithm (DCMA) has been proposed. Firstly, the improved DFT algorithm is used to accurately obtain the distance window of human body. Secondly, phase ambiguity in phase extraction is avoided based on extended DCMA algorithm. Then, the spectrum range of refinement is determined according to the peak position of the spectrum, and the respiratory and heartbeat frequency information is obtained by using chirp z-transform (CZT) algorithm to perform local spectrum refinement. For verification, this paper has simulated the radar echo signal modulated by the simulated cardiopulmonary signal according to the proposed algorithm. By recovering the simulated cardiopulmonary signal, the high-precision respiratory and heartbeat frequency have been obtained. The results show that the proposed algorithm can effectively restore human breathing and heartbeat signals, and the relative error of frequency estimation is basically kept below 1.5%.
Workers’ Cerebrocortical Activity in Hot and Humid Condition: An Electroencephalogram Study
Yixuan Wei, Yifei Xu, Shu Wang, Longzhe Jin, Tianqi Ding
2022, 31(1): 112-122. doi:10.15918/j.jbit1004-0579.2021.072
Abstract:
Hyperthermal environments can harm workers’ health and safety. However, it is difficult to include effective protection into standards because heat-related impacts vary significantly according to individual workers and multiple factors. Studies suggested obvious relationship between environment condition and bio-electricity signal, including electroencephalogram (EEG) signal. We used a detector with 64 electrodes to perform dedicated EEG measurements of nine individual subjects to analyze human cerebral activity under hyperthermal (35℃, 80% RH) and standard conditions (25℃, 30% RH). Amplitude changes of the frequency wavebands were analyzed using statistical analysis. Seven participants showed increasing beta activity due to high temperature and high humidity in the primary somatosensory cortex (electrode C3) and the temporopolar region (electrode FT 8). The amplitude value of alpha wave is increased from 0.194 to 0.213 while the amplitude value of beta wave is increased from 0.144 to 0.160. Value is decreased due to hyperthermal environment for most people. The results of this study could be used to inform the development of wearable equipment to monitor the health of on-site workers, which is fundamental to improve worker safety and wellbeing.
A Time-Frequency Associated MUSIC Algorithm Research on Human Target Detection by Through-Wall Radar
Xianyu Dong, Wu Ren, Zhenghui Xue, Xuetian Wang, Weiming Li
2022, 31(1): 123-130. doi:10.15918/j.jbit1004-0579.2021.087
Abstract:
In this paper, a time-frequency associated multiple signal classification (MUSIC) algorithm which is suitable for through-wall detection is proposed. The technology of detecting human targets by through-wall radar can be used to monitor the status and the location information of human targets behind the wall. However, the detection is out of order when classical MUSIC algorithm is applied to estimate the direction of arrival. In order to solve the problem, a time-frequency associated MUSIC algorithm suitable for through-wall detection and based on S-band stepped frequency continuous wave (SFCW) radar is researched. By associating inverse fast Fourier transform (IFFT) algorithm with MUSIC algorithm, the power enhancement of the target signal is completed according to the distance calculation results in the time domain. Then convert the signal to the frequency domain for direction of arrival (DOA) estimation. The simulations of two-dimensional human target detection in free space and the processing of measured data are completed. By comparing the processing results of the two algorithms on the measured data, accuracy of DOA estimation of proposed algorithm is more than 75%, which is 50% higher than classical MUSIC algorithm. It is verified that the distance and angle of human target can be effectively detected via proposed algorithm.
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