Les environnements intelligents et l’homme connecté semble être la prochaine évolution des télécommunications sans fil. En effet, le développement des nouvelles bandes de fréquence millimétriques permettront de créer des communications haut débit et de nouveaux types d’environnements, les Wireless Body Environment Networks, où les utilisateurs auront la possibilité d’interagir avec l’environnement. Pour développer ces environnements, il est nécessaire d’étudier les mécanismes de propagation et les canaux de communication sans fil autour du corps humain. Cette thèse analyse les canaux de propagation pour les réseaux corporels à 60 GHz et plus particulièrement trois scenarios: (i) la propagation entre une station de base externe et un noeud placé à proximité du corps (off-body) ; (ii) la propagation entre deux noeuds portés sur le corps (on-body) ; (iii) la communication entre une station de base externe et un noeud tenu porté par la main de l’utilisateur (near-body). Un modèle de canal numérique est proposé et implémenté pour modéliser la propagation off-body en environnement intérieur. Le modèle est basé sur le standard IEEE 802.11ad et une solution de la diffraction d’une onde plane incidente sur un modèle cylindrique du corps humain. Le modèle est développé pour deux polarisations orthogonales et les performances d’une communication WiGig sont étudiées via le bit error rate. La propagation on-body est étudiée pour deux différentes configurations: avec et sans ligne de vue directe. Ces scenarios mènent à des solutions analytiques différentes: l’équation de Norton et l’onde rampante. Ces solutions sont obtenues en utilisant des modèles de corps simplifiés et ont été validées expérimentalement. De plus, une méthode permettant d’améliorer le bilan de liaison entre deux dispositifs portés sur le corps en utilisant des plaques métalliques réduisant les pertes de propagation. Cette technique a été illustrée théoriquement en utilisant les équations de Millington. Une campagne de mesure a été effectuée sur un modèle de corps plat ayant les propriétés électriques de la peau humaine. Il a été montré que cette méthode permet d’augmenter le bilan de liaison de 20 dB. La région near-body s’étendant de 5 à 30 cm du corps humain est étudiée. Il s’agit de la région correspondant à la portée de main. Un algorithme numérique est proposé pour modéliser la présence d’un utilisateur dans un environnement intérieur. Un modèle statistique a aussi été proposé. Il a été montré que la distribution spatiale du champ suit une Two-Wave Diffuse Power distribution. / The smart environments and the connected human seems to be the future of wireless communications. The development of new frequency bands in the millimeter range will allow us to create high data rate communications which will led to the Wireless Body Environment Networks. In this kind of scenarios, it is expected that the user and the environment will interact. In order to develop such new applications, it is necessary to first study the propagation mechanisms and then, the communication channel underlying body centric environments. This thesis treats of channel models for 60 GHz Body Area Networks and more particularly of three kinds of scenarios: (i) the communication between an external base station and a worn node (off-body); (ii) the communication between two worn nodes (on-body); the communication between an external base station and a hand-held device (near-body). An indoor off-body channel model is numerically proposed and implemented. The model is based on the IEEE 802.11ad indoor standard channel at 60 GHz and a fast computation solution of the scattering of a plane wave by a circular cylinder. The model is developed for two orthogonal polarizations and the communications performances are studied. The on-body propagation is studied for two different configurations: line-of-sight and non-line-of-sight communications on the body. These scenarios led to different solutions for the channel knowing as, respectively, Norton’s equations and creeping formulations. These solutions are obtained using simplified geometries which has been experimentally validated. Further, in order to improve the propagation on the human body, a technique using metallic plates has been proposed. This technique has been theoretically studied using Milligton’s equations and experimentally assessed on a flat phantom with the properties of the human skin. The proposed method allows to save up to 20 dB. Finally, the near-body communication scenario has been introduced and studied. The near-body region is extended from 5 to 30 cm away of the user body which corresponds to the arm’s reach and models a handheld device. A numerical algorithm has been proposed to model indoor near-body environments. Also, a special has been given to statistical body shadowing. It has been shown that the fading follows a Two-Wave Diffuse Power distribution.

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Gait analysis is the systematic study of human walking. Clinical gait analysis is the process by which quantitative information is collected for the assessment and decision-making of any gait disorder. Although observational gait analysis is the therapist's primary clinical tool for describing the quality of a patient's walking pattern, it can be very unreliable. Modern gait analysis is facilitated through the use of specialized equipment. Currently, accurate gait analysis requires dedicated laboratories with complex settings and highly skilled operators. Wearable locomotion tracking systems are available, but they are not sufficiently accurate for clinical gait analysis. At the same time, wireless healthcare is evolving. Particularly, ultra wideband (UWB) is a promising technology that has the potential for accurate ranging and positioning in dense multi-path environments. Moreover, impulse-radio UWB (IR-UWB) is suitable for low-power and low-cost implementation, which makes it an attractive candidate for wearable, low-cost, and battery-powered health monitoring systems. The goal of this research is to propose and investigate a full-body wireless wearable human locomotion tracking system using UWB radios. Ultimately, the proposed system should be capable of distinguishing between normal and abnormal gait, making it suitable for accurate clinical gait analysis. / Ph. D.

The FCC allocated the spectrum of 402-405 MHz for MICS (Medical Implant Communication Services) applications in 1999. The regulations for MICS band apply to devices that support the diagnostic and/or therapeutic functions associated with implanted medical electronics. The implanted devices aid organs and control body functions of patients to support specific treatments, and monitor patients continuously so that necessary action can be taken in advance to avoid serious conditions. To enable to use MICS applications, several requirements must be satisfied. An implanted wireless device should have a small size, consume ultra-low power, and achieve the date rate of at least 200 kbps within 2 m distance. The major challenge is to realize ultra-low power devices. Thus the low-power design of the RF circuit is crucial for MICS applications as the power consumption of the wireless devices is mostly contributed by RF circuits. This thesis investigates low-power design of an LNA and a down-conversion mixer of a receiver for MICS applications. The key idea is to stack an LNA and a mixer, while the LNA operates in the normal super-threshold region and the mixer in the sub-threshold region. In addition, a gm-boosting technique with a capacitor cross-coupled at the LNA input stage is also adopted to achieve a low noise figure (NF) and high linearity, which is critical to the overall performance of the receiver. The mixer operating in the sub-threshold region significantly reduces power dissipation and relaxes the voltage headroom without sacrificing the LNA performance. The relaxed voltage headroom enables stack of the LNA and the mixer with a low supply voltage of 1.2 V. The proposed circuit is designed in 0.18 μm RF CMOS technology. The merged LNA and mixer consumes only 1.83 mW, and achieves 21.6 dB power gain. The NF of the block is 3.55 dB at 1 MHz IF, and the IIP3 is -6.08 dBm. / Master of Science

Wireless body area networks (WBANs) have tremendous potential to benefit from wireless communication technology and are expected to make sweeping changes in the future human health care and medical fields. While the prospects for WBAN products are high, meeting required device performance with a meager amount of power consumption poses significant design challenges. In order to address these issues, IEEE has recently developed a draft of IEEE 802.15.6 standard dedicated to low bit-rate short-range wireless communications on, in, or around the human body. Commercially available SoC (System-on-Chip) devices targeted for WBAN applications typically embed proprietary wireless transceivers. However, those devices usually do not meet the quality of service (QoS), low power, and/or noninterference necessary for WBAN applications, nor meet the IEEE standard specifications. This dissertation presents a design of low-power RF front-end conforming to the IEEE standard in Medical Communication Service (MICS) band of 402-405 MHz. First, we investigated IEEE 802.15.6 PHY specifications for narrow band WBAN applications. System performance analysis and simulation for an AWGN (additive white Gaussian noise) channel was conducted to obtain the BER (bit error rate) and the PER (packet error rate) as the figure of merit. Based on the system performance study, the link budget was derived as a groundwork for our RF front-end design. Next, we examined candidate RF front-end architectures suitable for MICS applications. Based on our study, we proposed to adopt a direct conversion transmitter and a low-IF receiver architecture for the RF front-end. An asynchronous wake-up receiver was also proposed, which is composed of a carrier sensing circuit and a serial code detector. Third, we proposed and implemented low-power building blocks of the proposed RF front-end. Two quadrature signal generation techniques were proposed and implemented for generation of quadrature frequency sources. The two quadrature voltage controlled oscillators (QVCOs) were designed using our proposed current-reuse VCO with two damping resistors. A stacked LNA and a down-conversion mixer were proposed for low supply and low power operation for the receiver front-end. A driver amplifier and an up-conversion mixer for the transmitter front-end were implemented. The proposed driver amplifier uses cascaded PMOS transistors to minimize the Miller effect and enhance the input/output isolation. The up-conversion mixer is based on a Gilbert cell with resistive loads. Simulation results and performance comparisons for each designed building block are presented. Finally, we present a case study on a direct VCO modulation transmitter and a super-regenerative receiver, which can also be suitable for an MICS transceiver. Several crucial building blocks including a digitally-controlled oscillator (DCO) and quench signal generators are proposed and implemented with a small number of external components. / Ph. D.

This thesis proposes an adaptive impedance matching, which involves the integration of an implanted antenna, a tunable matching network and a power amplifier in the lossy medium for the medical implant communication service (MICS) band (402 MHz to 405 MHz), as the opted frequency band where human body exhibits less conductivity and offers better wave penetration. However, it becomes challenging to design miniaturized capsule-sized antennas at this frequency due to the large wavelength size of the waveform. Therefore, the initial phase of the study is focused on a comprehensive investigation of the miniaturized implanted antennas and effective transmitting power in the lossy human heart tissue. Planar spiral antennas are chosen because of their adaptability in meandering and facilitate longer surface currents to achieve miniaturization. Moreover, various near-field effects of the implanted antenna are also presented and a circuit model is proposed to track its different behaviors while interacting with the complex tissue environment. Furthermore, due to its dependency on the surrounding complex environment, the resonance frequency of the implanted antenna is shifted which can result in the failure of the leadless pacemakers for medical devices. To mitigate this issue considering the miniaturized size of the medical device, a tunable L-matching network is incorporated between the power amplifier and the implanted antenna, where a simple voltage detection method is used to ensure that maximum power is delivered to the load and the power added efficiency of the power amplifier remains more than 48% after tuning the mismatch cases. The measurements are carried out in a liquid phantom and a maximum voltage is used to configure the best optimal combination of the matching network, so as a result a transmission coefficient is measured after the configuration owing to ensure that the adaptive impedance matching network is working in the background. The final results are compared in terms of reflection coefficient, transmission coefficient, and different insulation thicknesses.

Doctor of Philosophy / Department of Electrical and Computer Engineering / William B. Kuhn / Balasubramaniam Natarajan / Wireless body area networks (WBANs) are an important part of the developing internet of things (IOT). NASA currently uses space suits with wired sensors to collect limited biomedical data. Continuous monitoring and collecting more extensive body vital signs is important to assess astronaut health. This dissertation investigates wireless biomedical sensor systems that can be easily incorporated into future space suits to enable real time astronaut health monitoring. The focus of the work is on the radio-wave channel and associated antennas. We show that the space suit forms a unique propagation environment where the outer layers of the suit’s thermal micrometeoroid garment are largely radio opaque. This environment can be modeled as a coaxial one in which the body itself plays the role of the coax center conductor while the space suit shielding materials play the role of the outer shield. This model is then validated through simulations and experiments. Selecting the best frequency of operation is a complex mixture of requirements, including frequency allocations, attenuation in propagation, and antenna size. We investigate the propagation characteristics for various frequency bands from 315 MHz to 5.2 GHz. Signal attenuation is analyzed as a function of frequency for various communication pathways through 3D simulations and laboratory experiments. Small-scale radio channel results indicate that using lower frequency results in minimal path loss. On the other hand, measurements conducted on a full-scale model suggest that 433 MHz and 2400 MHz yield acceptable path loss values. Propagation between the left wrist and left ankle yielded the worst overall path loss, but signals were still above –100 dBm in raw measurements for a 0dBm transmission indicating that the intra-suit environment is conducive to wireless propagation. Our findings suggest that the UHF bands are best candidate bands since there is interplay between the body conductivity favoring lower frequencies, and the difficulty of coupling RF energy into and out of the channel using suitably sized antennas favoring higher frequencies. Finally, a new self-shielded folded bow-tie antenna is proposed that can be a promising choice for the general area of WBAN technologies as well as potential new space suit environments.