Experimental Clock Calibration\\on a Crystal-Free Mote-on-a-Chip

The elimination of the off-chip frequency reference, typically a crystal oscillator, would bring important benefits in terms of size, price and energy efficiency to IEEE802.15.4 compliant radios and systems-on-chip. The stability of on-chip oscillators is orders of magnitude worse than that of a crystal. It is known that as the temperature changes, they can drift more than 50 ppm/{\deg}C. This paper presents the result of an extensive experimental study. First, we propose mechanisms for crystal-free radios to be able to track an IEEE802.15.4 join proxy, calibrate the on-chip oscillators and maintain calibration against temperature changes. Then, we implement the resulting algorithms on a crystal-free platform and present the results of an experimental validation. We show that our approach is able to track a crystal-based IEEE802.15.4-compliant join proxy and maintain the requested radio frequency stability of +/-40 ppm, even when subject to temperature variation of 2{\deg}C/min.Comment: CNERT: Computer and Networking Experimental Research using Testbeds, in conjunction with IEEE INFOCOM 2019, April 29 - May 2, 2019, Paris, Franc

Millimeter-Scale and Energy-Efficient RF Wireless System

This dissertation focuses on energy-efficient RF wireless system with millimeter-scale dimension, expanding the potential use cases of millimeter-scale computing devices. It is challenging to develop RF wireless system in such constrained space. First, millimeter-sized antennae are electrically-small, resulting in low antenna efficiency. Second, their energy source is very limited due to the small battery and/or energy harvester. Third, it is required to eliminate most or all off-chip devices to further reduce system dimension. In this dissertation, these challenges are explored and analyzed, and new methods are proposed to solve them. Three prototype RF systems were implemented for demonstration and verification. The first prototype is a 10 cubic-mm inductive-coupled radio system that can be implanted through a syringe, aimed at healthcare applications with constrained space. The second prototype is a 3x3x3 mm far-field 915MHz radio system with 20-meter NLOS range in indoor environment. The third prototype is a low-power BLE transmitter using 3.5x3.5 mm planar loop antenna, enabling millimeter-scale sensors to connect with ubiquitous IoT BLE-compliant devices. The work presented in this dissertation improves use cases of millimeter-scale computers by presenting new methods for improving energy efficiency of wireless radio system with extremely small dimensions. The impact is significant in the age of IoT when everything will be connected in daily life.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/147686/1/yaoshi_1.pd

RF Integrated Circuits for Energy Autonomous Sensor Nodes.

The exponential growth in the semiconductor industry has enabled computers to pervade our everyday lives, and as we move forward many of these computers will have form factors much smaller than a typical laptop or smartphone. Sensor nodes will soon be deployed ubiquitously, capable of capturing information of their surrounding environment. The next step is to connect all these different nodes together into an entire interconnected system. This “Internet of Things” (IoT) vision has incredible potential to change our lives commercially, societally, and personally. The backbone of IoT is the wireless sensor node, many of which will operate under very rigorous energy constraints with small batteries or no batteries at all. It has been shown that in sensor nodes, radio communication is one of the biggest bottlenecks to ultra-low power design. This research explores ways to reduce energy consumption in radios for wireless sensor networks, allowing them to run off harvested energy, while maintaining qualities that will allow them to function in a real world, multi-user environment. Three different prototypes have been designed demonstrating these techniques. The first is a sensitivity-reduced nanowatt wake-up radio which allows a sensor node to actively listen for packets even when the rest of the node is asleep. CDMA codes and interference rejection reduce the potential for energy-costly false wake-ups. The second prototype is a full transceiver for a body-worn EKG sensor node. This transceiver is designed to have low instantaneous power and is able to receive 802.15.6 Wireless Body Area Network compliant packets. It uses asymmetric communication including a wake-up receiver based on the previous design, UWB transmitter and a communication receiver. The communication receiver has 10 physical channels to avoid interference and demodulates coherent packets which is uncommon for low power radios, but dictated by the 802.15.6 standard. The third prototype is a long range transceiver capable of >1km communication range in the 433MHz band and able to interface with an existing commercial radio. A digitally assisted baseband demodulator was designed which enables the ability to perform bit-level as well as packet-level duty cycling which increases the radio's energy efficiency.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/110432/1/nerobert_1.pd

Ultra-Low Power Wake Up Receiver For Medical Implant Communications Service Transceiver

This thesis explores the specific requirements and challenges for the design of a dedicated wake-up receiver for medical implant communication services equipped with a novel “uncertain-IF†architecture combined with a high – Q filtering MEMS resonator and a free running CMOS ring oscillator as the RF LO. The receiver prototype, implements an IBM 0.18μm mixed-signal 7ML RF CMOS technology and achieves a sensitivity of -62 dBm at 404MHz while consuming \u3c100 μW from a 1 V supply

Multi-channel ultra-low-power receiver architecture for body area networks

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 85-91).In recently published integrated medical monitoring systems, a common thread is the high power consumption of the radio compared to the other system components. This observation is indicative of a natural place to attempt a reduction in system power. Narrowband receivers in-particular can enjoy significant power reduction by employing high-Q bulk acoustic resonators as channel select filters directly at RF, allowing down-stream analog processing to be simplified, resulting in better energy efficiency. But for communications in the ISM bands, it is important to employ multiple frequency channels to permit frequency-division-multiplexing and provide frequency diversity in the face of narrowband interferers. The high-Q nature of the resonators means that frequency tuning to other channels in the same band is nearly impossible; hence, a new architecture is required to address this challenge. A multi-channel ultra-low power OOK receiver for Body Area Networks (BANs) has been designed and tested. The receiver multiplexes three Film Bulk Acoustic Resonators (FBARs) to provide three channels of frequency discrimination, while at the same time offering competitive sensitivity and superior energy efficiency in this class of BAN receivers. The high-Q parallel resonance of each resonator determines the passband. The resonator's Q is on the order of 1000 and its center frequency is approximately 2.5 GHz, resulting in a -3 dB bandwidth of roughly 2.5 MHz with a very steep rolloff. Channels are selected by enabling the corresponding LNA and mixer pathway with switches, but a key benefit of this architecture is that the switches are not in series with the resonator and do not de-Q the resonance. The measured 1E-3 sensitivity is -64 dBm at 1 Mbps for an energy efficiency of 180 pJ/bit. The resonators are packaged beside the CMOS using wirebonds for the prototype.by Phillip Michel Nadeau.S.M

Low-Power High-Data-Rate Transmitter Design for Biomedical Application

Ph.DDOCTOR OF PHILOSOPH

Experimental Clock Calibration on a Crystal-Free Mote-on-a-Chip

International audienceThe elimination of the off-chip frequency reference,typically a crystal oscillator, would bring important benefits in terms of size, price and energy efficiency to IEEE802.15.4compliant radios and systems-on-chip. The stability of on-chip oscillators is orders of magnitude worse than that of a crystal.It is known that as the temperature changes, they can drift more than50ppm/◦C. This paper presents the result of an extensive experimental study. First, we propose mechanisms for crystal-free radios to be able to track an IEEE802.15.4 join proxy, calibrate the on-chip oscillators and maintain calibration against temperature changes. Then, we implement the resulting algorithms on a crystal-free platform and present the results of an experimental validation. We show that our approach is able to track a crystal-based IEEE802.15.4-compliant join proxy and maintain the requested radio frequency stability of±40ppm, even when subject to temperature variation of2◦C/min

LOW-POWER IMPULSE-RADIO ULTRA-WIDEBAND TECHNIQUES FOR BIOMEDICAL APPLICATIONS.

Ph.DDOCTOR OF PHILOSOPH