A Low-Power BFSK/OOK Transmitter for Wireless Sensors

In recent years, significant improvements in semiconductor technology have allowed consistent development of wireless chipsets in terms of functionality and form factor. This has opened up a broad range of applications for implantable wireless sensors and telemetry devices in multiple categories, such as military, industrial, and medical uses. The nature of these applications often requires the wireless sensors to be low-weight and energy-efficient to achieve long battery life. Among the various functions of these sensors, the communication block, used to transmit the gathered data, is typically the most power-hungry block. In typical wireless sensor networks, transmission range is below 10 meters and required radiated power is below 1 milliwatt. In such cases, power consumption of the frequency-synthesis circuits prior to the power amplifier of the transmitter becomes significant. Reducing this power consumption is currently the focus of various research endeavors. A popular method of achieving this goal is using a direct-modulation transmitter where the generated carrier is directly modulated with baseband data using simple modulation schemes. Among the different variations of direct-modulation transmitters, transmitters using unlocked digitally-controlled oscillators and transmitters with injection or resonator-locked oscillators are widely investigated because of their simple structure. These transmitters can achieve low-power and stable operation either with the help of recalibration or by sacrificing tuning capability. In contrast, phase-locked-loop-based (PLL) transmitters are less researched. The PLL uses a feedback loop to lock the carrier to a reference frequency with a programmable ratio and thus achieves good frequency stability and convenient tunability. This work focuses on PLL-based transmitters. The initial goal of this work is to reduce the power consumption of the oscillator and frequency divider, the two most power-consuming blocks in a PLL. Novel topologies for these two blocks are proposed which achieve ultra-low-power operation. Along with measured performance, mathematical analysis to derive rule-of-thumb design approaches are presented. Finally, the full transmitter is implemented using these blocks in a 130 nanometer CMOS process and is successfully tested for low-power operation

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

ULTRA LOW POWER FSK RECEIVER AND RF ENERGY HARVESTER

This thesis focuses on low power receiver design and energy harvesting techniques as methods for intelligently managing energy usage and energy sources. The goal is to build an inexhaustibly powered communication system that can be widely applied, such as through wireless sensor networks (WSNs). Low power circuit design and smart power management are techniques that are often used to extend the lifetime of such mobile devices. Both methods are utilized here to optimize power usage and sources. RF energy is a promising ambient energy source that is widely available in urban areas and which we investigate in detail. A harvester circuit is modeled and analyzed in detail at low power input. Based on the circuit analysis, a design procedure is given for a narrowband energy harvester. The antenna and harvester co-design methodology improves RF to DC energy conversion efficiency. The strategy of co-design of the antenna and the harvester creates opportunities to optimize the system power conversion efficiency. Previous surveys have found that ambient RF energy is spread broadly over the frequency domain; however, here it is demonstrated that it is theoretically impossible to harvest RF energy over a wide frequency band if the ambient RF energy source(s) are weak, owing to the voltage requirements. It is found that most of the ambient RF energy lies in a series of narrow bands. Two different versions of harvesters have been designed, fabricated, and tested. The simulated and measured results demonstrate a dual-band energy harvester that obtains over 9% efficiency for two different bands (900MHz and 1800MHz) at an input power as low as -19dBm. The DC output voltage of this harvester is over 1V, which can be used to recharge the battery to form an inexhaustibly powered communication system. A new phase locked loop based receiver architecture is developed to avoid the significant conversion losses associated with OOK architectures. This also helps to minimize power consumption. A new low power mixer circuit has also been designed, and a detailed analysis is provided. Based on the mixer, a low power phase locked loop (PLL) based receiver has been designed, fabricated and measured. A power management circuit and a low power transceiver system have also been co-designed to provide a system on chip solution. The low power voltage regulator is designed to handle a variety of battery voltage, environmental temperature, and load conditions. The whole system can work with a battery and an application specific integrated circuit (ASIC) as a sensor node of a WSN network

Design of 2MHz OOK transmitter/receiver for inductive power and data transmission for biomedical implant

In this work a 2 MHz on-off keying (OOK) transmitter/receiver for inductive power and data transmission for biomedical implant system is presented. Inductive link, driven by a Class E power amplifier (PA) is the most PA used to transfer data and power to the internal part of biomedical implant system. Proposed transmitter consists of a digital control oscillator (DCO) and a class E PA which uses OOK modulation to transfer both data and power to a biomedical implant. In proposing OOK transmitter when the transmitter sends binary value “0” the DCO and PA are turned off. With this architecture and 2 MHz carrier wave we have implemented a wireless data and power transfer link which can transmit data with data rate 1Mbps and bit error rate (BER) of 10-5. The efficiency of power transfer is 42% with a 12.7 uH transmitter coil and a 2.4 uH receiver coil and the power delivered to the load is about 104.7 mW. Proposed transmitter is designed for output power 4.1V. OOK receiver consists of an OOK demodulator, powered by rectified and regulated 5V p-p RF signal across the receiver coil. The supply voltage of proposed voltage regulator is 5 V with 9mV/V line regulation of. All circuits proposed in this paper were designed and simulated using Cadence in 0.18 um CMOS process

System-on-Package Low-Power Telemetry and Signal Conditioning unit for Biomedical Applications

Recent advancements in healthcare monitoring equipments and wireless communication technologies have led to the integration of specialized medical technology with the pervasive wireless networks. Intensive research has been focused on the development of medical wireless networks (MWN) for telemedicine and smart home care services. Wireless technology also shows potential promises in surgical applications. Unlike conventional surgery, an expert surgeon can perform the surgery from a remote location using robot manipulators and monitor the status of the real surgery through wireless communication link. To provide this service each surgical tool must be facilitated with smart electronics to accrue data and transmit the data successfully to the monitoring unit through wireless network. To avoid unwieldy wires between the smart surgical tool and monitoring units and to reap the benefit of excellent features of wireless technology, each smart surgical tool must incorporate a low-power wireless transmitter. Low-power transmitter with high efficiency is essential for short range wireless communication. Unlike conventional transmitters used for cellular communication, injection-locked transmitter shows greater promises in short range wireless communication. The core block of an injection-locked transmitter is an injection-locked oscillator. Therefore, this research work is directed towards the development of a low-voltage low-power injection-locked oscillator which will facilitate the development of a low-power injection-locked transmitter for MWN applications. Structure of oscillator and types of injection are two crucial design criteria for low-power injection-locked oscillator design. Compared to other injection structures, body-level injection offers low-voltage and low-power operation. Again, conventional NMOS/PMOS-only cross-coupled LC oscillator can work with low supply voltage but the power consumption is relatively high. To overcome this problem, a self-cascode LC oscillator structure has been used which provides both low-voltage and low-power operation. Body terminal coupling is used with this structure to achieve injection-locking. Simulation results show that the self-cascode structure consumes much less power compared to that of the conventional structure for the same output swing while exhibiting better phase noise performance. Usage of PMOS devices and body bias control not only reduces the flicker noise and power consumption but also eliminates the requirements of expensive fabrication process for body terminal access

Ultra-Wideband CMOS Transceiver Front-End for Bio-Medical Radar Sensing

Since the Federal Communication Commission released the unlicensed 3.1-10.6 GHz frequency band for commercial use in early 2002, the ultra wideband (UWB) has developed from an emerging technology into a mainstream research area. The UWB technology, which utilizes wide spectrum, opens a new era of possibility for practical applications in radar sensing, one of which is the human vital sign monitoring. The aim of this thesis is to study and research the possibility of a new generation humanrespiration monitoring sensor using UWB radar technology and to develop a new prototype of UWB radar sensor for system-on-chip solutions in CMOS technology. In this thesis, a lowpower Gaussian impulse UWB mono-static radar transceiver architecture is presented. The UWB Gaussian pulse transmitter and receiver are implemented and fabricated using 90nm CMOS technology. Since the energy of low order Gaussian pulse is mostly condensed at lower frequency, in order to transmit the pulse in a very efficient way, higher order Gaussian derivative pulses are desired as the baseband signal. This motivates the advancement of the design into UWB high-order pulse transmitter. Both the Gaussian impulse UWB transmitter and Gaussian higher-order impulse UWB transmitter take the low-power and high-speed advantage of digital circuit to generate different waveforms. The measurement results are analyzed and discussed. This thesis also presents a low-power UWB mono-static radar transceiver architecture exploiting the full benefit of UWB bandwidth in radar sensing applications. The transceiver includes a full UWB band transmitter, an UWB receiver front-end, and an on-chip diplexer. The non-coherent UWB transmitter generates pulse modulated baseband signals at different carrier frequencies within the designated 3-10 GHz band using a digitally controlled pulse generator. The test shows the proposed radar transceiver can detect the human respiration pattern within 50 cm distance. The applications of this UWB radar sensing solution in commercialized standard CMOS technology include constant breathing pattern monitoring for gated radiation therapy, realtime monitoring of patients, and any other breathing monitoring. The research paves the way to wireless technology integration with health care and bio-sensor network

A -5 dBm 400MHz OOK Transmitter for Wireless Medical Application

A 400 MHz high efficiency transmitter forwireless medical application is presented in this paper. Transmitter architecture with high-energy efficiencies isproposed to achieve high data rate with low powerconsumption. In the on-off keying transmitters, the oscillatorand power amplifier are turned off when the transmittersends 0 data. The proposed class-e power amplifier has highefficiency for low level output power. The proposed on-offkeying transmitter consumes 1.52 mw at -5 dBm output by 40Mbps data rate and energy consumption 38 pJ/bit. Theproposed transmitter has been designed in 0.18µm CMOStechnology

Wireless wire - ultra-low-power and high-data-rate wireless communication systems

With the rapid development of communication technologies, wireless personal-area communication systems gain momentum and become increasingly important. When the market gets gradually saturated and the technology becomes much more mature, new demands on higher throughput push the wireless communication further into the high-frequency and high-data-rate direction. For example, in the IEEE 802.15.3c standard, a 60-GHz physical layer is specified, which occupies the unlicensed 57 to 64 GHz band and supports gigabit links for applications such as wireless downloading and data streaming. Along with the progress, however, both wireless protocols and physical systems and devices start to become very complex. Due to the limited cut-off frequency of the technology and high parasitic and noise levels at high frequency bands, the power consumption of these systems, especially of the RF front-ends, increases significantly. The reason behind this is that RF performance does not scale with technology at the same rate as digital baseband circuits. Based on the challenges encountered, the wireless-wire system is proposed for the millimeter wave high-data-rate communication. In this system, beamsteering directional communication front-ends are used, which confine the RF power within a narrow beam and increase the level of the equivalent isotropic radiation power by a factor equal to the number of antenna elements. Since extra gain is obtained from the antenna beamsteering, less front-end gain is required, which will reduce the power consumption accordingly. Besides, the narrow beam also reduces the interference level to other nodes. In order to minimize the system average power consumption, an ultra-low power asynchronous duty-cycled wake-up receiver is added to listen to the channel and control the communication modes. The main receiver is switched on by the wake-up receiver only when the communication is identified while in other cases it will always be in sleep mode with virtually no power consumed. Before transmitting the payload, the event-triggered transmitter will send a wake-up beacon to the wake-up receiver. As long as the wake-up beacon is longer than one cycle of the wake-up receiver, it can be captured and identified. Furthermore, by adopting a frequency-sweeping injection locking oscillator, the wake-up receiver is able to achieve good sensitivity, low latency and wide bandwidth simultaneously. In this way, high-data-rate communication can be achieved with ultra-low average power consumption. System power optimization is achieved by optimizing the antenna number, data rate, modulation scheme, transceiver architecture, and transceiver circuitries with regards to particular application scenarios. Cross-layer power optimization is performed as well. In order to verify the most critical elements of this new approach, a W-band injection-locked oscillator and the wake-up receiver have been designed and implemented in standard TSMC 65-nm CMOS technology. It can be seen from the measurement results that the wake-up receiver is able to achieve about -60 dBm sensitivity, 10 mW peak power consumption and 8.5 µs worst-case latency simultaneously. When applying a duty-cycling scheme, the average power of the wake-up receiver becomes lower than 10 µW if the event frequency is 1000 times/day, which matches battery-based or energy harvesting-based wireless applications. A 4-path phased-array main receiver is simulated working with 1 Gbps data rate and on-off-keying modulation. The average power consumption is 10 µW with 10 Gb communication data per day

Récepteur Sans-Fil à Basse Consommation et à Modulation Mixte FSK-ASK pour les Dispositifs Médicaux

RÉSUMÉ Les émetteurs-récepteurs radiofréquences (RF) offrent le lien de communications le plus commun afin de mettre au point des dispositifs médicaux implantables dédiés aux interfaces homme-machines. La surveillance en continu des paramètres biologiques des patients nécessite un module de communication sans-fil capable de garantir un échange de données rapide, en temps réel, à faible puissance tout en étant implémenté dans un espace physique réduit. La consommation de puissance des dispositifs implantables joue un rôle important dans les durées de vie des batteries qui nécessitent une chirurgie pour leur remplacement, à moins qu’une technique de transfert de puissance sans-fil soit utilisée pour recharger la batterie ou alimenter l’implant a travers les tissus humains. Dans ce projet, nous avons conçu, implémenté et testé un récepteur RF à faible puissance et haut-débit de données opérant entre 902 et 928 MHz qui est la bande industrielle-scientifiquemédicale (Industrial, Scientific and Medical) d’Amérique du Nord. Ce récepteur fait partie d’un système de communication bidirectionnel dédié à l’interface sans-fil des dispositifs électroniques implantables et bénéficie d’une nouvelle technique de conversion de modulation par déplacement de fréquence (FSK) en Modulation par déplacement d’amplitude (ASK). Toutes les phases de conception et d’implémentation de la topologie adoptée pour les récepteurs RF sont survolées et discutées dans cette thèse. Les différents étages de circuits sont conçus selon une étude analytique fondée de la modulation FSK et ASK utilisées, ce qui permettra une amélioration des performances notamment le débit de transmission des données et la consommation de puissance. Tous les circuits sont réalisés de façon à ce que la consommation totale et la surface de silicium à réserver soient le minimum possible. Un oscillateur avec verrouillage par injection (Injection-Looked Oscillator - ILO) de faible puissance est réalisé pour assurer la conversion des signaux ASK en FSK. Une combinaison des avantages des deux architectures de modulation d’amplitude et de fréquence, pour les circuits d’émetteurrécepteur sans fil, a été réalisé avec le système proposé. Un module incluant un récepteur de réveil (Wake up) est ajouté afin d’optimiser la consommation totale du circuit en mettant tous les blocs à l’arrêt. Nous avons réalisé un récepteur de réveil RF compact et à faible coût, permettant de très faible niveaux de consommation d’énergie, une bonne sensibilité et une meilleure tolérance aux interférences. Le design est basé sur une topologie homodyne à détection d’enveloppe permettant une transposition directe du signal RF modulé en amplitude en un signal en bande de base. Cette architecture nécessite une architecture peu encombrante à intégrer qui élimine le problème des fréquences image pour la même topologie avec une modulation de fréquence.---------- ABSTRACT ISM band transceiver using a wake-up bloc for wireless body area networks (WBANs) wearable and implantable medical devices is proposed. The system achieves exceptionally low-power consumption and allows a high-data rate by combining the advantages of Frequency-Shift-Keying (FSK) and Amplitude-Shift- Keying (ASK) modulation techniques. The transceiver employs FSK modulation at a data rate of 8 Mbit/s to establish RF link among the medical device and a control unit. Transmitter (Tx) includes a new efficient FSK modulation scheme which offer up to 20 Mb/s of data-rate and dissipates around 0.084 nJ/b. The design of the proposed oscillator achieves variable frequency from 300 kHz to 8 MHz by adjusting the transistors geometry, the on-chip control signal and the tuning capacitors. In the transmitter path, the high-quality LOs Inand Quadrature-phase (I and Q) outputs are produced using a very low-power fully integrated integer-N frequency synthesizer. The architecture of the receiver is inspired from the super-regenerative receiver (SRR) topology which can be used to design a transceiver that is suitable for ASK modulation. In fact, this architecture is based mainly on envelope detection scheme which remove the need to process the carrier phase to reduce the complexity of integrated design. It has been shown too, that the envelope detection scheme is more robust to phase noise than the coherent scheme. The integrated receiver uses on a new FSK-to-ASK conversion technique. The conversion feature that we adopt in the main receiver design is based on the fact that the incident frequency of converter could be differentiated by the amplitude of output signal, which conducts to the frequency-to-amplitude conversion. Thanks to the injection locking oscillator (ILO). the new design of converter is located between the LNA as first part and the envelope detector as second part to benefit from the injection-locking isolation. On-Off-keying (OOK) fully passive wake-up circuit (WuRx) with energy harvesting from Radio Frequency (RF) link is used to optimize the power issipation of the RF transceiver in order to meet the low power requirement. The WuRx operates at the ISM 902–928 MHz. A high efficiency differential rectifier behaves as voltage multiplier. It generates the envelope of the input signal and provides the supply voltage for the rest of blocks including a low-power comparator and reference generators

Low-Power High Data-Rate Wireless Transmitter For Medical Implantable Devices

RÉSUMÉ Les émetteurs-récepteurs radiofréquences (RF) sont les circuits de communication les plus communs pour établir des interfaces home-machine dédiées aux dispositifs médicaux implantables. Par exemple, la surveillance continue de paramètres de santé des patients souffrant d'épilepsie nécessite un étage de communication sans-fil capable de garantir un transfert de données rapide, en temps réel, à faible puissance tout en étant implémenté dans un faible volume. La consommation de puissance des dispositifs implantables implique une durée de vie limitée de la batterie qui nécessite alors une chirurgie pour son remplacement, a moins qu’une technique de transfert de puissance sans-fil soit utilisée pour recharger la batterie ou alimenter l’implant a travers les tissus humains. Dans ce projet, nous avons conçu, implémenté et testé un émetteur RF à faible puissance et haut-débit de données opérant à 902-928 MHz de la bande fréquentielle industrielle-scientifique-médicale (ISM) d’Amérique du Nord. Cet émetteur fait partie d'un système de communication bidirectionnel dédié à l’interface sans-fil des dispositifs électroniques implantables et mettables et bénéficie d’une nouvelle approche de modulation par déplacement de fréquence (FSK). Les différentes étapes de conception et d’implémentation de l'architecture proposée pour l'émetteur sont discutées et analysées dans cette thèse. Les blocs de circuits sont réalisés suivant les équations dérivées de la modulation FSK proposée et qui mènera à l'amélioration du débit de données et de la consommation d'énergie. Chaque bloc est implémenté de manière à ce que la consommation d'énergie et la surface de silicium nécessaires soient réduites. L’étage de modulation et le circuit mélangeur ne nécessitent aucun courant continu grâce à leur structure passive.Parmi les circuits originaux, un oscillateur en quadrature contrôlé-en-tension (QVCO) de faible puissance est réalisé pour générer des signaux différentiels en quadrature, rail-à-rail avec deux gammes de fréquences principales de 0.3 à 11.5 MHz et de 3 à 40 MHz. L'étage de sortie énergivore est également amélioré et optimisé pour atteindre une efficacité de puissance de ~ 37%. L'émetteur proposé a été implémenté et fabriqué à la suite de simulations post-layout approfondies.----------ABSTRACT Wireless radio frequency (RF) transceivers are the most common communication front-ends used to realize the human-machine interfaces of medical devices. Continuous monitoring of body behaviour of patients suffering from Epilepsy, for example, requires a wireless communication front-end capable of maintaining a fast, real-time and low-power data communication while implemented in small size. Power budget limitation of the implantable and wearable medical devices obliges engineers to replace or recharge the battery cell through frequent medial surgeries or other power transfer techniques. In this project, a low-power and high data-rate RF transmitter (Tx) operating at North-American Industrial-Scientific-Medical (ISM) frequency band (902-928 MHz) is designed, implemented and tested. This transmitter is a part of a bi-directional transceiver dedicated to the wireless interface of implantable and wearable medical devices and benefits from a new efficient Frequency-Shift Keying (FSK) modulation scheme. Different design and implementation stages of the proposed transmitter architecture are discussed and analyzed in this thesis. The building blocks are realized according to the equations derived from the proposed FSK modulation, which results in improvement in data-rate and power consumption. Each block is implemented such that the power consumption and needed chip area are lowered while the modulation block and the mixer circuit require no DC current due to their passive structure. Among the original blocks, a low-power quadrature voltage-controlled oscillator (QVCO) is achieved to provide differential quadrature rail-to-rail signals with two main frequency ranges of 0.3-11.5 MHz and 3-40 MHz. The power-hungry output stage is also improved and optimized to achieve power efficiency of ~37%. The proposed transmitter was implemented and fabricated following deep characterisation by post-layout simulation. Both simulation and measurement results are discussed and compared with state-of-the-art transmitters showing the contribution of this work in this very popular research field. The Figure-Of-Merit (FOM) was improved, meaning mainly increasing the data-rate and lowering the power consumption of the circuit. The transmitter is implemented using 130 nm CMOS technology with 1.2 V supply voltage. A data-rate of 8 Mb/s was measured while consuming 1.4 mA and resulting in energy consumption of 0.21 nJ/b. The fabricated transmitter has small active silicon area of less than 0.25 mm2