Recent developments and technological advancements in wireless communication, MicroElectroMechanical Systems (MEMS) technology and integrated circuits has enabled low-power, intelligent, miniaturized, invasive/non-invasive micro and nano-technology sensor nodes strategically placed in or around the human body to be used in various applications, such as personal health monitoring. This exciting new area of research is called Wireless Body Area Networks (WBANs) and leverages the emerging IEEE 802.15.6 and IEEE 802.15.4j standards, specifically standardized for medical WBANs. The aim of WBANs is to simplify and improve speed, accuracy, and reliability of communication of sensors/actuators within, on, and in the immediate proximity of a human body. The vast scope of challenges associated with WBANs has led to numerous publications. In this paper, we survey the current state-of-art of WBANs based on the latest standards and publications. Open issues and challenges within each area are also explored as a source of inspiration towards future developments in WBANs.

Wireless Body Area Networks: A Survey

In recent years, indoor positioning has emerged as a critical function in many end-user applications; including military, civilian, disaster relief and peacekeeping missions. In comparison with outdoor environments, sensing location information in indoor environments requires a higher precision and is a more challenging task in part because various objects reflect and disperse signals. Ultra WideBand (UWB) is an emerging technology in the field of indoor positioning that has shown better performance compared to others. In order to set the stage for this work, we provide a survey of the state-of-the-art technologies in indoor positioning, followed by a detailed comparative analysis of UWB positioning technologies. We also provide an analysis of strengths, weaknesses, opportunities, and threats (SWOT) to analyze the present state of UWB positioning technologies. While SWOT is not a quantitative approach, it helps in assessing the real status and in revealing the potential of UWB positioning to effectively address the indoor positioning problem. Unlike previous studies, this paper presents new taxonomies, reviews some major recent advances, and argues for further exploration by the research community of this challenging problem space.

https://www.mdpi.com/1424-8220/16/5/707/pdf

Ultra Wideband Indoor Positioning Technologies: Analysis and Recent Advances.

A single-fed miniaturized circularly polarized microstrip patch antenna is designed and experimentally demonstrated for industrial-scientific-medical (2.4-2.48 GHz) biomedical applications. The proposed antenna is designed by utilizing the capacitive loading on the radiator. Compared with the initial topology of the proposed antenna, the so-called square patch antenna with a center-square slot, the proposed method has the advantage of good size reduction and good polarization purity. The footprint of the proposed antenna is 10×10×1.27 mm3. The simulated impedance, axial ratio, and radiation pattern are studied and compared in two simulation models: cubic skin phantom and Gustav voxel human body. The effect of different body phantoms is discussed to evaluate the sensitivity of the proposed antenna. The effect of coaxial cable is also discussed. Two typical approaches to address the biocompatibility issue for practical applications are reported as well. The simulated and measured impedance bandwidths in cubic skin phantom are 7.7% and 10.2%, respectively. The performance of the communication link between the implanted CP antenna and the external antenna is also presented.

Capacitively Loaded Circularly Polarized Implantable Patch Antenna for ISM Band Biomedical Applications

Design of effective wearable tags for UHF RFID applications involving persons is still an open challenge due to the strong interaction of the antenna with the human body which is responsible of impedance detuning and efficiency degradation. A new tag geometry combining folded conductors and tuning slots is here discussed through numerical analysis and extensive experimentation also including the integration of a passive motion detector. The achieved designs, having size comparable with a credit card, may be applied to any part of the body. The measured performance indicates a possible application of these body-worn tags for the continuous tracking of human movements in a conventional room.

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Modeling, Design and Experimentation of Wearable RFID Sensor Tag

A compact circularly polarized (CP) co-designed filtering antenna is reported. The device is based on a patch radiator seamlessly integrated with a bandpass filter composed of coupled stripline open-loop resonators, which are designed together as a system. In the proposed design, the patch functions simultaneously as the radiator and the last stage resonator of the filter, resulting in a low-profile integrated radiating and filtering module with a small overall form factor of $\mathbf{0.53{\lambda _0} \times 0.53{\lambda _0} \times 0.07{\lambda _0}}$ . It is shown that the filtering circuit not only ensures frequency selectivity but also provides impedance matching functionality, which serves to broaden both the impedance and axial ratio bandwidths. The designed filtering antenna was fabricated and measured, experimentally achieving an $\mathbf{{S_{11}} , an axial ratio of less than 3 dB and a gain higher than 5.2 dBi over a bandwidth from 3.77 to 4.26 GHz, i.e., around 12.2%, which makes it an excellent candidate for integration into a variety of wireless systems. A linearly polarized version of the integrated filtering antenna was also demonstrated. In addition, further full-wave simulations and experiments were carried out to verify that the designed CP filtering antenna maintains its properties even when mounted on different positions of the human body with various body gestures. The stable impedance and radiation properties also make it a suitable candidate as a wearable antenna for off-body wireless communications.

A Compact, Wideband Circularly Polarized Co-designed Filtering Antenna and Its Application for Wearable Devices With Low SAR

Many phantom models with detailed external and internal features have been introduced in recent years by researchers and are now provided with commercial electromagnetic simulators. Phantoms vary in size, resolution, internal structure and posture. Although some phantoms can be posed, it is not straightforward to recreate the exact positions of test subjects for validation purposes. This section focuses on creating a moving human model with postures closely corresponding to those used in measurements to be used for validation in EM software.

Antennas and Propagation for Body-Centric Wireless Communications

Accurate and precise motion tracking of limbs and human subjects has technological importance in various healthcare applications. The use of impulse radio-ultra wideband technology (IR-UWB) technology due its inherent properties is of recent interest for high-accuracy localization. This paper presents experimental investigations and analysis of indoor human body localization and tracking of limb movements in 3-D based on IR-UWB technology using compact and cost-effective body-worn antennas. The body-centric wireless channel characterization has been analyzed in detail using parameters such as path loss magnitude, number of multipath components, rms delay spread, signal amplitude, and Kurtosis with the main focus to differentiate between line-of-sight (LOS) and non-LOS situations. Fidelity of the received signal is also calculated for different activities and antenna positions to study the pulse preserving nature of the UWB antenna, when it is placed on the human body. The results reported in this paper have high localization accuracy with 90% in the range from 0.5 to 2.5 cm using simple and cost-effective techniques which is comparable to the results obtained by the standard optical motion capture system.

/pdf/impulse-radio-ultra-wideband-communications-for-localization-2q2stvp685.pdf

Impulse Radio Ultra-Wideband Communications for Localization and Tracking of Human Body and Limbs Movement for Healthcare Applications

This letter presents a study of human body localization using ultrawideband (UWB) technology. Various base-station configurations, time of arrival, and first peak detection algorithms are used to estimate the position of the body-worn antennas. Localization error as small as 1-2 cm has been achieved using eight base stations, which is comparable to the measurement accuracy obtained by a complex optical motion capture system to determine the absolute displacement error. The localization error obtained is better by a third in comparison to common commercial system based on UWB technology. The results demonstrate that cuboid-shape configuration with four base stations gives slightly low average percentage error (2%-3%) in comparison to Y-shape (4%). However, the Y-shape configuration is more compact and provides setting-up simplicity, which makes it convenient for various applications ranging from healthcare monitoring to entertainment technologies either laboratory-based or in-home.

/pdf/localization-of-wearable-ultrawideband-antennas-for-motion-13mj0fiao9.pdf

Localization of Wearable Ultrawideband Antennas for Motion Capture Applications

Recently, the RF/microwave electronic technology evolved with the consideration of plastic and organic substrates Such a technology offers two-folded benefits: in one side for lowering the fabrication cost and in another side for the possibility to bend electronic devices Such a technology is particularly interesting for the implementation of antenna system This paper is dealing with the design of flexible microstrip antenna 1:2 array Theoretical approach on the typically symmetrical antenna 1:2 array is proposed The design methodology of microstrip antenna combined with 1:2 T-power divider (T-PWD) is described Based on the transmission line theory, the S-parameter model of the antenna system with non-standard reference load is established Then, the microstrip antenna passive system is theoretical analysed in function of the physical dimensions of the designed structure The feasibility of the flexible antenna passive system is investigated with the proof-of-concept (POC) designed on Kapton substrate The POC prototype consisted of microstrip antenna 1:2 array is designed to operate at about 58 GHz Comparisons between the full wave simulated and measured return losses were performed Then, simulated radiation pattern highlights the efficiency of the fabricated prototype of passive antenna array

https://www.jpier.org/pierc/pierc63/11.15120906.pdf

Design of Flexible Passive Antenna Array on Kapton Substrate

© 2014 IEEE.This paper characterizes coplanar waveguide (CPW) lines formed by ink-jet printed conductors on flexible Kapton substrates at frequencies up to 60 GHz. It is shown that the lines have losses of approximately 1.5 dB/mm but that this relatively high loss is predominantly due to the loss tangent of the substrates and not the lower conductivity of the silver inks used in this implementation. On an Alumina sample the loss is shown to be 0.8 dB/mm for the same ink-jet printed lines. CST simulation has been used to verify the calculated results.

S. Swaisaenyakorn

Papers

Antennas and Propagation for Body-Centric Wireless Communications

Impulse Radio Ultra-Wideband Communications for Localization and Tracking of Human Body and Limbs Movement for Healthcare Applications

Localization of Wearable Ultrawideband Antennas for Motion Capture Applications

Design of Flexible Passive Antenna Array on Kapton Substrate

Characterization of Ink-Jet Printed CPW on Kapton Substrates At 60 GHz