Ultra-Low-Power Sensors and Receivers for IoT Applications

The combination of ultra-low power analog front-ends and CMOS-compatible transducers enable new applications, such as environmental monitors, household appliances, health trackers, etc. that are seamlessly integrated into our daily lives. Furthermore, wireless connectivity allows many of these sensors to operate both independently and collectively. These techniques collectively fulfil the recent surge of internet-of-things (IoT) applications that have the potential to fundamentally change daily life for millions of people.In this dissertation, the circuit and system design of wireless receivers and sensors is presented that explores the challenges of implementing long lifespan, high accuracy, and large coverage range IoT sensor networks. The first is a wake-up receiver (WuRX), which continuously monitors the RF environment to wake up a higher-power radio upon detection of a predetermined RF signature. This work both improves sensitivity and reduces power over prior art through a multi-faceted design featuring an impedance transformation network with large passive voltage gain, an active envelope detector with high input impedance to facilitate large passive voltage gain, a low-power precision comparator, and a low-leakage digital baseband correlator.Although pushing the prior WuRX performance boundary by orders of magnitude, the first work shows moderate sensitivity, inferior temperature robustness, and large area with external lumped components. Thus, the second work shows a miniaturized WuRX that is temperature-compensated, yet still consumes only nano-watt power and millimeter area while operating at 9 GHz. To further reduce the area, a global common-mode feedback is utilized across the envelope detector and baseband amplifier that eliminates the need for off-chip ac-coupling components. Multiple temperature-compensation techniques are proposed to maintain constant bandwidth of the signal path and constant clock frequency. Both WuRXs operate at 0.4 V supply, consume near-zero power and achieve ~-70 dBm sensitivity.Lastly, the first reported CMOS 2-in-1 relative humidity and temperature sensor is presented. A unified analog front-end interfaces on-chip transducers and converts the inputs into a frequency vis a high-linearity frequency-locked loop. An incomplete-settling switched-capacitor-based Wheatstone bridge is proposed to sense the inputs in a power-efficient fashion

RF MEMS reference oscillators platform for wireless communications

A complete platform for RF MEMS reference oscillator is built to replace bulky quartz from mobile devices, thus reducing size and cost. The design targets LTE transceivers. A low phase noise 76.8 MHz reference oscillator is designed using material temperature compensated AlN-on-silicon resonator. The thesis proposes a system combining piezoelectric resonator with low loading CMOS cross coupled series resonance oscillator to reach state-of-the-art LTE phase noise specifications. The designed resonator is a two port fundamental width extensional mode resonator. The resonator characterized by high unloaded quality factor in vacuum is designed with low temperature coefficient of frequency (TCF) using as compensation material which enhances the TCF from - 3000 ppm to 105 ppm across temperature ranges of -40˚C to 85˚C. By using a series resonant CMOS oscillator, phase noise of -123 dBc/Hz at 1 kHz, and -162 dBc/Hz at 1MHz offset is achieved. The oscillator’s integrated RMS jitter is 106 fs (10 kHz–20 MHz), consuming 850 μA, with startup time is 250μs, achieving a Figure-of-merit (FOM) of 216 dB. Electronic frequency compensation is presented to further enhance the frequency stability of the oscillator. Initial frequency offset of 8000 ppm and temperature drift errors are combined and further addressed electronically. A simple digital compensation circuitry generates a compensation word as an input to 21 bit MASH 1 -1-1 sigma delta modulator incorporated in RF LTE fractional N-PLL for frequency compensation. Temperature is sensed using low power BJT band-gap front end circuitry with 12 bit temperature to digital converter characterized by a resolution of 0.075˚C. The smart temperature sensor consumes only 4.6 μA. 700 MHz band LTE signal proved to have the stringent phase noise and frequency resolution specifications among all LTE bands. For this band, the achieved jitter value is 1.29 ps and the output frequency stability is 0.5 ppm over temperature ranges from -40˚C to 85˚C. The system is built on 32nm CMOS technology using 1.8V IO device

Ultra Low Power Circuits for Internet of Things and Deep Learning Accelerator Design with In-Memory Computing

Collecting data from environment and converting gathered data into information is the key idea of Internet of Things (IoT). Miniaturized sensing devices enable the idea for many applications including health monitoring, industrial sensing, and so on. Sensing devices typically have small form factor and thus, low battery capacity, but at the same time, require long life time for continuous monitoring and least frequent battery replacement. This thesis introduces three analog circuit design techniques featuring ultra-low power consumption for such requirements: (1) An ultra-low power resistor-less current reference circuit, (2) A 110nW resistive frequency locked on-chip oscillator as a timing reference, (3) A resonant current-mode wireless power receiver and battery charger for implantable systems. Raw data can be efficiently transformed into useful information using deep learning. However deep learning requires tremendous amount of computation by its nature, and thus, an energy efficient deep learning hardware is highly demanded to fully utilize this algorithm in various applications. This thesis also presents a pulse-width based computation concept which utilizes in-memory computing of SRAM.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144173/1/myungjun_1.pd

Design of an RC Oscillator for Automotive Applications

Tato práce je zaměřena na návrh integrovaného relaxačního oscilátoru pro automobilové aplikace, které jsou charakteristické extrémními provozními podmínkami a vysokými požadavky na robustnost. Z dostupné literatury byla provedena rešerše, která umožnila postihnout nezbytný teoretický základ pro komparativní studii nedávno představených designů integrovaných oscilátorů a také pomohla navrhnout architekturu oscilátoru, která v implementaci zahrnuje princip IEF. Za účelem předpovězení negativních vlivů na výkon systému a optimálních parametrů bloků byly provedeny simulace vysokoúrovňového modelu. V práci je diskutována implementace jednotlivých bloků a prezentovány výsledky simulace kritických parametrů. Simulace navrženého oscilátoru prokázaly konzistenci konceptu IEF pro praktickou realizaci. Realizovaný systém však potřebuje další vylepšení.The thesis is aimed on the integrated relaxation oscillator design for automotive applications, that are characterized by harsh operation conditions and high robustness requirements. Literature research was conducted to acquire necessary theoretical basis for comparative study of the recently proposed integrated oscillator designs to choose the oscillator architecture utilizing integrated-error feedback for the implementation. High-level model simulations were conducted to predict negative influences on the system performance and to suggest blocks optimal parameters for the design. The implementation of the designed blocks was discussed, and simulation results of the critical parameters were presented. The designed oscillator simulations proved the consistency of the integrated-error feedback concept for practical realization. However, the designed system needs further improvements

Meteorological measurements, Satellite PL Quarterly report, 1 Jun. - 31 Aug. 1968

Development of balloon-borne miniature radio altimeter and investigation of multiple array infrared imaging from synchronous satellite

Ultra-low Power Circuits for Internet of Things (IOT)

Miniaturized sensor nodes offer an unprecedented opportunity for the semiconductor industry which led to a rapid development of the application space: the Internet of Things (IoT). IoT is a global infrastructure that interconnects physical and virtual things which have the potential to dramatically improve people's daily lives. One of key aspect that makes IoT special is that the internet is expanding into places that has been ever reachable as device form factor continue to decreases. Extremely small sensors can be placed on plants, animals, humans, and geologic features, and connected to the Internet. Several challenges, however, exist that could possibly slow the development of IoT. In this thesis, several circuit techniques as well as system level optimizations to meet the challenging power/energy requirement for the IoT design space are described. First, a fully-integrated temperature sensor for battery-operated, ultra-low power microsystems is presented. Sensor operation is based on temperature independent/dependent current sources that are used with oscillators and counters to generate a digital temperature code. Second, an ultra-low power oscillator designed for wake-up timers in compact wireless sensors is presented. The proposed topology separates the continuous comparator from the oscillation path and activates it only for short period when it is required. As a result, both low power tracking and generation of precise wake-up signal is made possible. Third, an 8-bit sub-ranging SAR ADC for biomedical applications is discussed that takes an advantage of signal characteristics. ADC uses a moving window and stores the previous MSBs voltage value on a series capacitor to achieve energy saving compared to a conventional approach while maintaining its accuracy. Finally, an ultra-low power acoustic sensing and object recognition microsystem that uses frequency domain feature extraction and classification is presented. By introducing ultra-low 8-bit SAR-ADC with 50fF input capacitance, power consumption of the frontend amplifier has been reduced to single digit nW-level. Also, serialized discrete Fourier transform (DFT) feature extraction is proposed in a digital back-end, replacing a high-power/area-consuming conventional FFT.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/137157/1/seojeong_1.pd

High brightness light sources for defence applications

This thesis contains the results of the work that was carried out between February 2009 and September 2012 in the area of high brightness light sources for defence applications. The work follows two main themes, namely nonlinearity in optical fibres and optical parametric oscillators (OPOs). Initially, the prospect of creating an ultrafast light source from solid core microstructured fibre via the phenomenon of modulation instability is discussed alongside supercontinuum generation and its value as a broad bandwidth source in countermeasures. What follows concerns OPOs in the infrared, both external (extracavity) and internal (intracavity) to a laser cavity, with the former is of benefit for high power applications, whereas the latter allows the OPO to operate more effectively at lower powers. The extracavity OPO section discusses a 2-stage conversion from 1064nm to 2128nm with the second stage design for conversion to ~5000nm, and the intracavity work is directed at both enabling a single frequency source for spectroscopy and examining the relationship between output coupling and the resonant OPO and laser fields

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