Design and Implementation of a Low‐Power Wireless Respiration Monitoring Sensor

Wireless devices for monitoring of respiration activities can play a major role in advancing modern home-based health care applications. Existing methods for respiration monitoring require special algorithms and high precision filters to eliminate noise and other motion artifacts. These necessitate additional power consuming circuitry for further signal conditioning. This dissertation is particularly focused on a novel approach of respiration monitoring based on a PVDF-based pyroelectric transducer. Low-power, low-noise, and fully integrated charge amplifiers are designed to serve as the front-end amplifier of the sensor to efficiently convert the charge generated by the transducer into a proportional voltage signal. To transmit the respiration data wirelessly, a lowpower transmitter design is crucial. This energy constraint motivates the exploration of the design of a duty-cycled transmitter, where the radio is designed to be turned off most of the time and turned on only for a short duration of time. Due to its inherent duty-cycled nature, impulse radio ultra-wideband (IR-UWB) transmitter is an ideal candidate for the implementation of a duty-cycled radio. To achieve better energy efficiency and longer battery lifetime a low-power low-complexity OOK (on-off keying) based impulse radio ultra-wideband (IR-UWB) transmitter is designed and implemented using standard CMOS process. Initial simulation and test results exhibit a promising advancement towards the development of an energy-efficient wireless sensor for monitoring of respiration activities

The Design of Low Power Ultra-Wideband Transceiver

Ph.DDOCTOR OF PHILOSOPH

Crystal-Less RF Communication Integrated Circuits for Wireless Sensor Networks.

The evolution of computing devices has changed daily life significantly over the past decades, and it is still advancing towards pervasive and ubiquitous networks. At each step, the volume shrinks by 2-3 orders of magnitude while the functionality and computing power remains constant or increases. Wireless sensor networks (WSN) are perceived as the next big step of computing technology for a variety of applications, including environmental sensing, health monitoring, un-obtrusive surveillance and invisible labeling. With thin-film micro-battery technology and CMOS scaling, we can now envision complete sensor nodes with cubic-mm form factors. As node volume reduces, external components like a crystal frequency reference, which does not scale with frequency or process, becomes one of the bottlenecks of realizing cubic-mm WSN node devices. This dissertation covers several aspects of the energy and integration challenges associated with cubic-mm WSN nodes without crystal references. Several new compact and low-power RF circuits for the synchronization and communication of WSN nodes are proposed and discussed. A 60GHz antenna-referenced frequency-locked loop (FLL) using an on-chip patch antenna as both the radiator and the frequency reference has been demonstrated for RF synchronization. The FLL, targeting communication of non-coherent energy detection systems, provides adequate frequency accuracy without crystal references. A 10GHz ultra-wideband (UWB) crystal-less transmitter with an on-chip monopole antenna has also been demonstrated. It operates over the supply voltage range of a micro-battery; generate tunable pulse durations and center frequencies, and lives on an on-chip local decoupling capacitor only. A 1MHz temperature-compensated relaxation oscillator is also proposed in the dissertation for baseband data synchronization. With the modified RC network of the conventional relaxation oscillator, the transfer function of the network has a transmission zero, introducing an additional degree-of-freedom for temperature compensation design. Finally, a 60GHz transmit/receive (T/R) switch-less antenna front-end using an on-chip patch antenna is presented, which has an in-band isolation inherited from the standing wave pattern without implementing a T/R switch. The research projects have explored the circuit design techniques and system integration for cubic-mm energy-constrained devices, achieving both long lifetimes and small volumes for WSN applications.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/99763/1/kkhuang_1.pd

Ultra-Wideband Transceiver Design And Optimization

University of Minnesota Ph.D. dissertation. July 2015. Major: Electrical Engineering. Advisor: Ramesh Harjani. 1 computer file (PDF); xiii, 128 pages.The technology landscape has quickly changed over the last few years. Developments in personal area networks, IC technology, DSP processing and bio-medical devices have enabled the integration of short range communication into low cost personal health care solutions. Newer technologies and solutions are being developed to cater to the personal operating space(POS) and body area networks(BAN). Health care is driving towards using multiple sensor and therapeutic nodes inside the POS. Technology has enabled remote patient care where the patient has low cost on-body wearables that allow the patient/physician to access vital signs without the patient physically visiting the clinic. Big semiconductor giants want to move into the wearable health monitor space. Along with the developments in fitness based health wearables, there has been a lot of interest towards developing BAN devices catering to the 'mission-critical' wearables and implants. Hearing aids, EKG monitors, neurostimulators are some examples. This work explores the use of the 802.15 ulta wideband (UWB) standard for designing a radio to operate in the a wireless sensor network in the BAN. The specific application targeted is a hearing aid. However, the design in this work is capable of working in a low power low range application with the ability to have multiple data rates ranging from a few kHz to 10's of MHz. The first radio designed by Marconi using spark-gap transmitters was an impulse radio (IR). The IR UWB technology boasts of low power, low cost, high data rates, multiple channels, simultaneous networking, the ability to carry information through obstacles that more limited bandwidths cannot, and also potentially lower complexity hardware design. The inherent timing accuracy associated with the technology gives UWB transmissions immunity to multipath fading and are hence make them more suitable for a cluttered indoor environment. The key difference with the traditional narrowband transceiver is that instead of using continuous wave (CW) transmission, impulses in time are used. The timing accuracy associated with these impulses require synchronization in time, rather than synchronization in frequency for carrier-based CW systems. A complete fully integrated system is presented in thesis. This work presents a low-power noncoherent IR UWB transceiver operating at 5GHz in 0.13um CMOS. A fully-digital transmitter generates a shaped output pulse of 1GHz 3-dB bandwidth. DLLs provide a PVT-tolerant time-step resolution of 1ns over the entire symbol period and regulate the pulse generator center frequency. The transmitter outputs -31dBm (0.88pJ/pulse at 1Mpulse/s) with a dynamic (energy) efficiency of 16pJ/pulse. The transmit out pulse is FCC part 15 compliant over process voltage and temperature (PVT) variations. The transmitter is semi-compliant with IEEE 802.15.6 and IEEE 802.15.4 standards and will become completely compliant with minor modifications. The receiver presented in this work is a non-coherent energy detect IR UWB receiver. The receiver has an on-chip transformer preceding the LNA, which is followed by a super-regenerative amplifier (SRA), envelope detector, sample-and-holds, and a bank of comparators. The design is SRA based energy-detection receiver. Measured results show a receiver efficiency of 0.32nJ/bit at 20.8Mb/s and operation with inputs as low as -70dBm. The SRA based energy-detection receiver utilizes early/late detection for a two-step baseband synchronization algorithm. An integrated solution to the issue of synchronization is also proposed. The system proposed is capable of synchronization and tracking control. The system in this work utilizes early/late detection for a two-step baseband synchronization algorithm. The algorithm is implemented in Matlab and the time to synchronization is observed to be between 250us to a few couple of ms. Measurements have also been made using the receiver and manually implementing the algorithm. This work addresses all aspects time synchronization in an IR transceiver. The initial mismatch is addressed by two methods. Beyond the initial synchronization, the system presented in this system is also capable of tracking. This would mean that once the transceiver has been synchronized, the timing generation would continue to track the phase and the frequency changes depending upon crystal drift over time or movement between the receiver and the transmitter. A test was also performed on the complete transceiver system with two radios talking to each other over a highly attenuated wired channel

Ultra Wideband

Ultra wideband (UWB) has advanced and merged as a technology, and many more people are aware of the potential for this exciting technology. The current UWB field is changing rapidly with new techniques and ideas where several issues are involved in developing the systems. Among UWB system design, the UWB RF transceiver and UWB antenna are the key components. Recently, a considerable amount of researches has been devoted to the development of the UWB RF transceiver and antenna for its enabling high data transmission rates and low power consumption. Our book attempts to present current and emerging trends in-research and development of UWB systems as well as future expectations

Advances in Integrated Circuit Design and Implementation for New Generation of Wireless Transceivers

User’s everyday outgrowing demand for high-data and high performance mobile devices pushes industry and researchers into more sophisticated systems to fulfill those expectations. Besides new modulation techniques and new system designs, significant improvement is required in the transceiver building blocks to handle higher data rates with reasonable power efficiency. In this research the challenges and solution to improve the performance of wireless communication transceivers is addressed. The building block that determines the efficiency and battery life of the entire mobile handset is the power amplifier. Modulations with large peak to average power ratio severely degrade efficiency in the conventional fixed-biased power amplifiers (PAs). To address this challenge, a novel PA is proposed with an adaptive load for the PA to improve efficiency. A nonlinearity cancellation technique is also proposed to improve linearity of the PA to satisfy the EVM and ACLR specifications. Ultra wide-band (UWB) systems are attractive due to their ability for high data rate, and low power consumption. In spite of the limitation assigned by the FCC, the coexistence of UWB and NB systems are still an unsolved challenge. One of the systems that is majorly affected by the UWB signal, is the 802.11a system (5 GHz Wi-Fi). A new analog solution is proposed to minimize the interference level caused by the impulse Radio UWB transmitter to nearby narrowband receivers. An efficient 400 Mpulse/s IR-UWB transmitter is implemented that generates an analog UWB pulse with in-band notch that covers the majority of the UWB spectrum. The challenge in receiver (RX) design is the over increasing out of blockers in applications such as cognitive and software defined radios, which are required to tolerate stronger out-of-band (OB) blockers. A novel RX is proposed with a shunt N-path high-Q filter at the LNA input to attenuate OB-blockers. To further improve the linearity, a novel baseband blocker filtering techniques is proposed. A new TIA has been designed to maintain the good linearity performance for blockers at large frequency offsets. As a result, a +22 dBm IIP3 with 3.5 dB NF is achieved. Another challenge in the RX design is the tough NF and linearity requirements for high performance systems such as carrier aggregation. To improve the NF, an extra gain stage is added after the LNA. An N-path high-Q band-pass filter is employed at the LNA output together with baseband blocker filtering technique to attenuate out-of-band blockers and improve the linearity. A noise-cancellation technique based on the frequency translation has been employed to improve the NF. As a result, a 1.8dB NF with +5 dBm IIP3 is achieved. In addition, a new approach has been proposed to reject out of band blockers in carrier aggregation scenarios. The proposed solution also provides carrier to carrier isolation compared to typical solution for carrier aggregation

Digital ADCs and ultra-wideband RF circuits for energy constrained wireless applications by Denis Clarke Daly.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 173-183).Ongoing advances in semiconductor technology have enabled a multitude of portable, low power devices like cellular phones and wireless sensors. Most recently, as transistor device geometries reach the nanometer scale, transistor characteristics have changed so dramatically that many traditional circuits and architectures are no longer optimal and/or feasible. As a solution, much research has focused on developing 'highly digital' circuits and architectures that are tolerant of the increased leakage, variation and degraded voltage headrooms associated with advanced CMOS processes. This thesis presents several highly digital, mixed-signal circuits and architectures designed for energy constrained wireless applications. First, as a case study, a highly digital, voltage scalable flash ADC is presented. The flash ADC, implemented in 0.18 [mu]m CMOS, leverages redundancy and calibration to achieve robust operation at supply voltages from 0.2 V to 0.9 V. Next, the thesis expands in scope to describe a pulsed, noncoherent ultra-wideband transceiver chipset, implemented in 90 nm CMOS and operating in the 3-to-5 GHz band. The all-digital transmitter employs capacitive combining and pulse shaping in the power amplifier to meet the FCC spectral mask without any off-chip filters. The noncoherent receiver system-on-chip achieves both energy efficiency and high performance by employing simple amplifier and ADC structures combined with extensive digital calibration. Finally, the transceiver chipset is integrated in a complete system for wireless insect flight control.(cont.) Through the use of a flexible PCB and 3D die stacking, the total weight of the electronics is kept to 1 g, within the carrying capacity of an adult Manduca sexta moth. Preliminary wireless flight control of a moth in a wind tunnel is demonstrated.Ph.D

Design exploration and measurement benchmark of integrated-circuits based on graphene field-effect-transistors : towards wireless nanotransceivers

This doctoral thesis approaches the design requirements for future high / ultra-high data rate (from 100 Mbps to 100 Gbps) nanotransceivers (nanoTRx) applied to wireless nanonetworks which imply short/ultra-short distance ranges (3 cm ¿ 3 m). It explores graphene field-effect-transistors (GFET), by simulation against measurement benchmarks, as a potential solution for implementing large-signal high-frequency circuits, by virtue of graphene¿s one-atom thickness and high carrier-mobility extraordinary properties. Finally, the thesis discusses the challenges faced by GFETs, such as zero-bandgap and high metal-graphene contact-resistance, to be able to propose improvements for achieving the initial proposed goals. Chemical-Vapour-Deposition (CVD) GFET fabrication is considered, which is very promising for large-scale manufacturing (CMOS process compatible), and for that fast-computing large-signal compact modeling for complex circuit design is analysed in depth and optimized, and consequently a set of diverse large-signal static and dynamic GFET circuits are simulated and benchmarked against available measurements assessing the accuracy of the proposed models and deriving scaling prospects. An optimization of the current-to-voltage (I-V) characteristic of a GFET compact model, based upon drift-diffusion carrier transport, is presented. The improved accuracy at the Dirac point extends the model usability for GFETs when scaling parameters such as voltage supply (Vdd), gate length (L), dielectric thickness (tox) and carrier mobility (¿) for large-signal design exploration in circuits. The model accuracy is demonstrated through parameters fitting to measurements taken from CVD GFETs fabricated in the University of Siegen and Technical University of Milan. The script has been written in a standard behavioural language (Verilog-A), and extensively run in a commercial analog circuit simulator (Cadence environment) demonstrating its robustness. Besides a simple capacitance-to-voltage model (C-V), a small-signal parasitic capacitance model fitted to dynamic measurements for self-aligned CVD GFETs available in the literature is added, enabling to forecast maximum-frequency-of-oscillation (fmax) trends for future scaling. A design-oriented characterization of complementary inverter circuits (INV) based on GFETs is presented as well. Our proposed compact model is benchmarked at the circuit level against another compact model based on a virtual-source approach. Furthermore, a benchmark between simulations and measurements of already fabricated CVD GFET INVs is performed, and performance trends when scaling are derived. The same process is repeated for a more complex circuit, namely GFET ring-oscillators (RO). The transient regime simulations yield performance metrics in terms of oscillation frequency (fosc) and dynamic voltage range (¿Vosc), and consequently, against these metrics, a comprehensive design space exploration covering as input design variables parameters as tox, L, and Vdd is carried out. Being aware of the lack of voltage amplification shown by existing GFETs, the design exploration of a cascode amplifier (CAS) targeted to increase voltage gain (Av) by decreasing its output conductance (go) is presented. GFET CAS are simulated to provide design guidelines, they are accordingly fabricated and consequently measured. Performance metrics are provided in terms of go, transconductance (gm) and hence Av. Against these metrics, a quantitative comparison between CAS and GFETs is performed and conclusions are derived. Finally, conclusions on GFETs suitability for future nanoTRX are elaborated. The derived publications come from international collaborations with the Royal Institute of Technology (KTH) in Sweden from 2012 to 2014, and the University of Siegen in Germany from 2014 to 2016.Esta tesis doctoral trata de identificar los requisitos de diseño para nano-ransceptores (nanoTRx) con datos de alta velocidad (de 100 Mbps a 100 Gbps) aplicados a nano-redes inal ámbricas que implican rangos de alcance cortos u ultra-cortos (3 cm - 3 m ); explora FETs de grafeno (GFET), mediante simulaciones y mediciones, como una solución potencial para la implementación de circuitos de alta frecuencia de gran señal, gracias a las extraordinarias propiedades del grafeno como su espesor de un solo átomo y sus portadores de alta movilidad; y finalmente, se discuten los desafíos a los que se enfrentan los GFETs, como la falta de banda prohibida y la alta resistencia de contacto, para lograr proponer alternativas y poder alcanzar los objetivos iniciales propuestos. Las publicaciones derivadas provienen de Colaboraciones internacionales con el KTH en Suecia de 2012 a 2014, y la UniSiegen en Alemania de 2014 a 2016. Se introducen la técnica CVD como un proceso de fabricación de GFETs a gran escala, compatible con tecnología CMOS, muy prometedor; y el modelado compacto de gran señal y computación veloz para el diseño de circuitos complejos es optimizados y analizado en profundidad, Consecuentemente circuitos de gran señal (estáticos y dinámicos) basados en GFET son simulados y comparados con las mediciones disponibles para evaluar la precisi ón de los modelos propuestos y derivar prospecciones de escalado. Se propone una optimización de la característica corriente-voltaje (I-V) de un modelo compacto GFET, basado en el transporte de portadores difusi ón-deriva. La precisión mejorada en el punto de Dirac extiende la usabilidad del modelo para GFETs cuando se dimensionan parámetros para la exploración en diseños de circuitos de gran señal, tales como el voltaje de alimentación (Vdd), la longitud de puerta (L), el espesor diel éctrico (tOX) y la movilidad de portadores (U). La precisión del modelo se demuestra a través de parámetros que se ajustan a mediciones tomadas a partir de CVD GFETs fabricados en la UniSiegen y en el PoliMi. El programa se ha escrito en Verilog-A y se ejecuta extensivamente en un simulador de circuitos anal ógico comercial donde se demuestra su robustez. Además, se lleva a cabo la parametrización de un modelo capacidad-voltaje (C-V) que se ajusta a las mediciones de alta frecuencia de CVD GFETs disponibles en la literatura científica, lo que permite la predicción de la fMAX para el escalado de futuros GFETs. También se presenta una caracterización orientada al diseño de circuitos inversores complementarios (INV) basados en GFETs. Nuestro modelo compacto propuesto se compara a nivel de circuito con otro modelo compacto basado en fuentevirtual. A continuación, se lleva a cabo una comparación a nivel circuito entre las simulaciones y las medidas de INVs ya fabricados basados en CVD GFET, y se obtienen las tendencias de comportamiento al escalarlos. Se repite el mismo proceso para un circuito más complejo, los llamados osciladores-en-anillo GFET (RO). Las simulaciones basadas en transitorios producen métricas de rendimiento en términos de frecuencia de oscilación (fosc) y rango dinámico de voltaje (Vosc), por lo tanto, contra estas métricas, se lleva a cabo una exploración exhaustiva de diseño que abarca Parámetros de variables de diseño como tOX, L y Vdd. Al ser conscientes de la falta de amplificación de voltaje mostrada por los GFETs existentes, se presenta la exploración de diseño de un amplificador cascodo (CAS) diseñado para incrementar la amplificación de voltaje (Av) disminuyendo su conductancia de salida (go). Los GFET CAS son simulados para proporcionar guías de diseño, luego fabricadas y finalmente medidas. Se proporcionan métricas de rendimiento en términos de go, gm, y consecuentemente Av. Frente a estas métricas, se realiza una comparación cuantitativa entre CAS y GFETs y se derivan las conclusiones. Finalmente, se elaboran las conclusiones sobre la idoneidad de los GFET para futuros nanoTR

Ultra Low Power FM-UWB Transceiver for High-Density Wireless Sensor Networks

The WiseSkin project aims to provide a non-invasive solution for restoration of a natural sense of touch to persons using prosthetic limbs. By embedding sensor nodes into the silicone coating of the prosthesis, which acts as a sensory skin, WiseSkin targets to provide improved gripping, manipulation and mobility for amputees. Flexibility, freedom of movement and comfort demand unobtrusive, highly miniaturized, low-power sensing capabilities built into the artificial skin, which is then integrated with a sensory feedback system. Wireless communication between the sensor nodes provides more flexibility, better scalability and robustness compared to wired solution, and is therefore a preferred approach for WiseSkin. Design of an RF transceiver tailored for the specific needs of WiseSkin is the topic of this work. The properties of FM ultra-wide band (FM-UWB) modulation make it a good candidate for High-Density Wireless Sensor Networks (HD-WSN). The proposed FM-UWB receivers take advantage of short range to reduce power consumption, and exploit robustness of this wideband modulation scheme. The LNA, identified as the biggest consumer, is removed and signal is directly converted to dc, where amplification and demodulation are performed. Owing to 500 MHz bandwidth, frequency offset and phase noise can be tolerated, and a low-power, free-running ring oscillator can be used to generate the LO signal. The receiver is referred to as an approximate zero-IF receiver. Two receiver architectures are studied. The first one performs quadrature downconversion, and owing to the demodulator linearity, provides the multi-user capability. In the second receiver, quadrature demodulation is replaced by the single-ended one. Due to the nature of the demodulator, sensitivity degrades, and multiple FM-UWB signals cannot be resolved, but the consumption is almost halved compared to the first receiver. The proposed approach is verified through two integrations, both in a standard 65 nm bulk CMOS process. In the first run, a standalone quadrature receiver was integrated. Power consumption of 423 uW was measured, while achieving -70 dBm sensitivity. Good narrow-band interference rejection and multiuser capability with up to 4 FM-UWB channels could be achieved. In the second run, a full transceiver is integrated, with both quadrature and single-ended receivers and a transmitter, all sharing a single IO pad, without the need for any external passive components or switches. The quadrature receiver, with on-chip baseband processing and multi-user support, in this case consumes 550 uW, with a sesensitivity of -68 dBm. The low power receiver consumes 267 uW, and provides -57 dBm sensitivity, at a single FM-UWB channel. The implemented trantransmitter transmits a 100 kb/s FM-UWB signal at -11.4 dBm, while drawing 583 uW from the 1 V supply. The on-chip clock recovery allows reference frequency offset up to 8000 ppm. Since state of the art on-chip RC oscillators can provide below 2100 ppm across the temperature range of interest, the implemented transceiver demonstrates the feasibility of a fully integrated FM-UWB radio with no need for a quartz reference or any external components. In addition, the transceiver can tolerate up to 3 dBm narrow-band interferer at 2.4 GHz. Such a strong signal can be used to remotely power the sensor nodes inside the artificial skin and enable a truly wirelessWiseSkin solution