Showing papers by "Jianqing Wang published in 2017"

Motion artefact removals for wearable ECG using stationary wavelet transform.

Abstract: Wearable Electrocardiogram (ECG) is attracting much attention in daily healthcare applications. From the viewpoint of long-term use, it is desired that the electrodes are non-contact with the human body. In this study, the authors propose an algorithm using the stationary wavelet transform (SWT) to remove motion artefact superimposed on ECG signal when using non-contact capacitively coupling electrodes. The authors evaluate the effect on motion artefact removal of this algorithm by applying it to various ECG signals with motion artefacts superimposed. As a result, the correlation coefficients of ECG signals with respect to the clean ones have been improved from 0.71 to 0.88 on median before and after motion artefact removal, which demonstrates the validity of the proposed SWT-based algorithm.

Performance Evaluation of an Ultra-Wideband Transmit Diversity in a Living Animal Experiment

Abstract: To realize implant communications with a high data rate, ultra-wideband (UWB) transmission has gathered a lot of attention as a promising candidate. However, due to high operation frequency, the UWB communication link suffers from large attenuation. This represents the difficulty to achieve reliable communications. To mitigate such a problem, spatial diversity techniques have been proposed in the literature, where some of them work without any frequency extension. In contrast, the implant side diversity technique has been rarely discussed because of the difficulty in miniaturizing the size of the transmitter antenna. In this paper, we designed a UWB transmitter diversity antenna and evaluated its performance numerically and experimentally. First, we analyzed the antenna performance using a finite-difference time-domain simulation and physical experiment in a liquid phantom. Thereafter, we measured the path loss performance in an implant communication link using a liquid phantom and a living porcine subject. Finally, we evaluated the impact of the implant side polarization diversity system with the developed antenna on the communication performance. Based on the measured isolation between the polarization channels, our measurements show that a signal-to-noise power ratio improvement of 7 dB can be in principle achieved with a predicted outage rate of 0.01 and a range of 15 cm in typical body environments.

No adverse effects detected for simultaneous whole-body exposure to multiple-frequency radiofrequency electromagnetic fields for rats in the intrauterine and pre- and post-weaning periods

Abstract: In everyday life, people are exposed to radiofrequency (RF) electromagnetic fields (EMFs) with multiple frequencies. To evaluate the possible adverse effects of multifrequency RF EMFs, we performed an experiment in which pregnant rats and their delivered offspring were simultaneously exposed to eight different communication signal EMFs (two of 800 MHz band, two of 2 GHz band, one of 2.4 GHz band, two of 2.5 GHz band and one of 5.2 GHz band). Thirty six pregnant Sprague-Dawley (SD) 10-week-old rats were divided into three groups of 12 rats: one control (sham exposure) group and two experimental (low- and high-level RF EMF exposure) groups. The whole body of the mother rats was exposed to the RF EMFs for 20 h per day from Gestational Day 7 to weaning, and F1 offspring rats (46-48 F1 pups per group) were then exposed up to 6 weeks of age also for 20 h per day. The parameters evaluated included the growth, gestational condition and organ weights of the dams; the survival rates, development, growth, physical and functional development, memory function, and reproductive ability of the F1 offspring; and the embryotoxicity and teratogenicity in the F2 rats. No abnormal findings were observed in the dams or F1 offspring exposed to the RF EMFs or to the F2 offspring for any of the parameters evaluated. Thus, under the conditions of the present experiment, simultaneous whole-body exposure to eight different communication signal EMFs at frequencies between 800 MHz and 5.2 GHz did not show any adverse effects on pregnancy or on the development of rats.

Electromagnetic interference of wireless power transfer system on wearable electrocardiogram

Abstract: The increasing ageing population is leading to a wide-scale demand for health-state monitoring by a wireless body area network (BAN). Wireless BAN needs each vital sensor to act as a wearable device for collecting blood pressure, electrocardiogram (ECG), electroencephalogram and so on in daily life. On the other hand, wireless power transfer is also getting into our daily life because of its convenience, which suggests a potential electromagnetic interference (EMI) problem on the wearable devices in healthcare and medical BAN. In this study, the authors quantitatively evaluated the EMI on wearable ECG for 6.8 MHz wireless power transfer system. They employed electromagnetic field analysis technique to derive the common-mode voltage between the human body with a wearable ECG and the ground plane, and circuit simulation or measurement to derive the interference voltage at the wearable ECG output. The result first time gave a quantitative evaluation for EMI of wireless power transfer on wearable ECG. The approach is also available to be applied to EMI evaluation of other wearable devices in healthcare or medical applications.

Common-mode noise cancellation circuit for wearable ECG.

Abstract: Wearable electrocardiogram (ECG) is attracting much attention for monitoring heart diseases in healthcare and medical applications. However, an imbalance usually exists between the contact resistances of sensing electrodes, so that a common mode noise caused by external electromagnetic field can be converted into the ECG detection circuit as a differential mode interference voltage. In this study, after explaining the mechanism of how the common mode noise is converted to a differential mode interference voltage, the authors propose a circuit with cadmium sulphide photo-resistors for cancelling the imbalance between the contact resistances and confirm its validity by simulation experiment. As a result, the authors found that the interference voltage generated at the wearable ECG can be effectively reduced to a sufficient small level.

Motion artifact removal for wearable ECG using stationary wavelet multi-resolution analysis

Abstract: Wearable electrocardiogram (ECG) is attracting much attention in daily healthcare applications. From the view-point of long-term use, it is desired that the electrodes are non-contact with the human body. In this study, we propose an algorithm using the stationary wavelet transform (SWT) to remove motion artifact superimposed on ECG signal when using non-contact capacitively coupling electrodes. In addition, we confirmed that the proposed algorithm performed well on the ECG signals including a premature ventricular contraction (PVC) using MIT-BIH Arrhythmia Database. As a result, the correlation coefficients of ECG signals with respect to the clean ones have been improved from 0.61 to 0.84 on median before and after motion artifact removal, which demonstrates the validity of the proposed SWT-based algorithm.

Throughput evaluation on multilevel modulation with local frequency offset spatial diversity for 400 MHz band implant communications

Abstract: One of promising applications for implant communications is a wireless capsule endoscope, which can realise a high quality of medical and healthcare services. However, the regulation of medical implant communication service (MICS) band often employed by the wireless capsule endoscope prevents reliable and high-speed transmission due to its narrowband limitation. In this study, the authors introduce several multilevel modulation schemes with local frequency offset diversity reception into the implant communications to improve the communication reliability and the data rate without any frequency bandwidth extension. Then, the authors evaluate the throughput performances for the proposed multilevel modulation with spatial diversity reception based on propagation characteristics of implant wireless signals derived by a finite difference time domain analysis. Consequently, the computer simulation results demonstrate that the proposed implant communication system can accomplish maximum communication distance of 20 cm ensuring excellently high throughput of 1.5 Mbps under the MICS bandwidth limitation of 300 kHz in a realistic implant communication scenario.

A Three-Dimensional EM-Based Implant Device Localization Method Improved by Genetic Algorithm

Abstract: These years, implant devices has been attracting great attention. Wireless capsule endoscope is one good example of the implant devices. Nowadays, the implant devices are usually used to just examine one’s diseases. However, in the near future, they may be used not only for the examination but also to treatment of a disease. To realize the next generation capsule endoscope, it is strongly required to add location information to the implant device. Such localization techniques enable us to control the movement of the implant device or to improve the treatment efficiency. Localization techniques has been studied widely, which often use radio frequency (RF) signals from the device. When we use this technique, there is a problem that we need a burdensome pre-measurements before the localization. To avoid such a burdensome pre-measurement, we turn our eyes on electromagnetic (EM) imaging which estimates the internal structure of an subject. The imaging can realize an examination without any burdensome pre-measurements, however, the EM imaging with high resolution will need huge computational complexity. To solve the problem, we applied genetic algorithm (GA) into the EM imaging-based localization method. Furthermore, we evaluated the localization performance of the proposed GA-based method compared with the conventional RF-based methods through computer simulations using a simple human body model. In addition, we show a possibility of using the EM imaging as an promising implant device localization method without any burdensome pre-measurement.

Theoretical and experimental analyses on location/channel parameters estimation for implantable medical devices

Abstract: A maximum a posteriori (MAP) method to simultaneously estimate location and channel parameters for implantable medical devices is proposed. Achievable localisation accuracy is investigated and discussed based on theoretical and experimental evaluation. As for the theoretical analysis, the Cramer–Rao lower bound for the proposed MAP estimation is derived. Consequently, it is demonstrated that the proposed method achieves precious location estimation accuracy from both theoretical and experimental aspects.

Preliminary experimental validation of arrival direction detection system with two antennas for partial discharge noise

Abstract: For secure power transmission and reliable power distribution, it is necessary to detect power equipment failure immediately when it occurs. In order to properly accomplish the failure detection, we pay attention to the measurement of a partial discharge noise at the electrical power equipment because the partial discharge should be observed before the failure due to insulation deterioration. In this paper, we developed an arrival direction detection system with a two antennas for the partial discharge noise. In the developed system, the two-dimensional angle of arrival (AOA) of the partial discharge noise was estimated based on the phase difference between two received signals. We experimentally evaluated the accuracy of the AOA detection in two types of situations: anechoic chamber and outdoor environment, for an amplitude modulated signal as the first step to simulate a partial noise. The experimental results demonstrated that the detection error of AOA was below 10 degrees.

Measurement of ESD noise voltage induced on human body by considering it as an equivalent antenna

Abstract: In this study, we proposed a measurement method of charging voltage on the human body caused by ESD and measured the human body charging voltage under the IEC-specified ESD testing environment It is found that the human body charging voltage steeply rises, reaches the peak value at 20 ns, then converges to a constant value It reaches a maximum of about 400 V for a charging voltage of 8 kV Based on the measured ESD charging voltage on the human body, the ESD noise characteristics generated in wearable bio-sensors can be clarified

Two approaches for determining the whole-body average SAR in a reverberation chamber

Abstract: This paper aims to perform a comparison study of two approaches, two-step hybrid method and S-parameter measurement method, for determining the whole-body average-specific absorption rate (WBA-SAR) for rats in a reverberation chamber (RC). The two-step hybrid method incorporates finite-difference time-domain (FDTD) numerical solutions with electric field measurements in a RC-type exposure system; S-parameter measurement method is a totally experimental evaluation method to estimate the WBA-SAR in an RC. We first compare the WBA-SAR results derived in two rat-equivalent phantoms, then investigate the influence of measurement error on the relative error of WBA-SAR to clarify the validity and accuracy of these two approaches.

Indirect ESD testing for a myoelectric artificial hand

Abstract: In this study, we conducted an indirect electrostatic discharge (ESD) test for a myoelectric artificial hand using a pseudo myoelectric signal generator together with a bio-equivalent phantom. The indirect ESD test followed the IEC61000-4-2. Through a comparison of the ESD test results between the pseudo myoelectric signal generator and the real human body, we found a high similarity between them, which suggests the feasibility of employing the pseudo signal generator and the bio-equivalent phantom in an immunity test for wearable robotic equipment.

Non-contact measuring method for high-frequency impedance of load at the end of wire harness

Abstract: Request to non-contact measurement method of load impedance connected to a wire harness is increasing rapidly. A method using network analyzer together with two current probes were previously proposed for this purpose, but it is valid only to 30 MHz. In this study, we extended the above-mentioned non-contact measurement method to 100 MHz by applying transmission line theory to the wire harness. The validity of the newly proposed measurement method was confirmed experimentally, and as a result the load impedance was measured with an error within 10% up to 100 MHz.