Srijittra Swaisaenyakorn

Localization of Wearable Ultrawideband Antennas for Motion Capture 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.

A Study of Factors Affecting Wrist Channel Characteristics for Walking Postures Using Motion Capture

The creation of a 3D animated human model (avatar) to be used in electromagnetic (EM) simulation software is described for low outage body area network application such as healthcare. Scanned surface data of a human model is combined with movement data from a Motion Capture system to simulate an on-body channel between two dual band metallic button antennas (DBMBAs) mounted on the wrist and chest and the wrist and hip during walking. An investigation of how different factors such as human geometry parameters, arm swing and wrist twisting can affect the body-centric channel during walking action is presented together with the relative significance of each of these factors on predicting body-centric channel gain.

Body gain study for animated human model in a body worn antenna system

This paper presents the study of body gain in a Body worn antenna system using both measurement and simulation. The simulation has been done in XFdtd, EM (electromagnetic) simulation software, using a 3D-surface scan of a test person. The gesture of the body and positions of antennas on the 3D body surface in the simulation were extracted from data obtained by a motion capture system while the actual measurement was taking place using the dual band metallic button antennas. Additional simulation is done on a standard model available in XFdtd to compare the quality of created 3D model from this research.

Evaluation of 3D animated human model from 3D scanner and motion capture to be used in electromagnetic simulator for body-centric system

Body-worn physiological sensors can facilitate ambulatory patient monitoring, particularly if communication between sensors is wireless; but the communication channel must be robust. This paper presents how a 3D animated human model is created using a 3D scanner and a motion capture system. Then this model is used in XFdtd, electromagnetic simulation software to obtain body worn channel properties. Three walking gestures from the created model, wearing dual band metallic button antennas, DBMBAs, were simulated and compared with the original measurements carried out on the real test human model. Furthermore, verification of the 3D animated model was achieved by comparing the simulation results of the main test model with measurements from 5 additional test models.

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

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.

Design of Flexible Passive Antenna Array on Kapton Substrate

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 5.8 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.

Comparison of 3D scanned human models for off-body communications using motion capture

Body area networks are complex to analyze as there are several channel mechanisms occurring simultaneously, i.e. environmental multipath together with body motion and close coupling between worn antennas and human tissue. Electromagnetic (EM) simulation is an important tool since not all studies can be done on a real human. In order to gain insight into off-body communication involving a worn antenna, this paper uses a 3D animated model obtained from a 3D surface scanner and a motion capture system for full wave simulation of channels at 2.45 and 5.5GHz. To evaluate if the model can represent body area radio channels in general, a comparison of S21 of the simulated model with measurements from 5 other models of similar height to the main test subject is presented.

Personal and body area network channels between Dual Band Button Antennas

This paper describes an assessment of space diversity for bodyworn Dual Band Metallic Button Antennas. The optimal combination of locations has been assessed according to the received signal envelope, cross-correlation coefficient and diversity gain for the ISM bands at 2.45 and 5.5GHz. Received signal envelopes were combined using the Selection, Maximum Ratio and Equal Gain combining algorithms. Results are taken with both vertical and horizontal polarizations for different body positions with respect to the transmitting antenna.

Characterization of ink-jet printed CPW on Kapton substrates at 60 GHz

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.

Conformal switched beam antenna

A cylindrical switched beam antenna making use of Kapton film and aperture-coupling is presented. The use of four elements controlled via a high frequency switching stage is proposed. Using very simple bias circuitry, switching can be achieved to provide four-way coverage at 0°, 90°, 180° and 270°. Elements consist of an aperture-coupled patch making use of thin film technology to provide an air substrate for increased efficiency and therefore gain. Four direction beam switching is performed using only three switches integrated into the structure. Simulated results of a single element are presented, followed by measured results of the fully fabricated structure.