A Wide Band Adaptive All Digital Phase Locked Loop With Self Jitter Measurement And Calibration

The expanding growth of mobile products and services has led to various wireless communication standards that employ different spectrum bands and protocols to provide data, voice or video communication services. Software deffned radio and cognitive radio are emerging techniques that can dynamically integrate various standards to provide seamless global coverage, including global roaming across geographical regions, and interfacing with different wireless networks. In software deffned radio and cognitive radio, one of the most critical RF blocks that need to exhibit frequency agility is the phase lock loop (PLL) frequency synthesizer. In order to access various standards, the frequency synthesizer needs to have wide frequency tuning range, fast tuning speed, and low phase noise and frequency spur. The traditional analog charge pump frequency synthesizer circuit design is becoming diffcult due to the continuous down-scalings of transistor feature size and power supply voltage. The goal of this project was to develop an all digital phase locked loop (ADPLL) as the alternative solution technique in RF transceivers by taking advantage of digital circuitry\u27s characteristic features of good scalability, robustness against process variation and high noise margin. The targeted frequency bands for our ADPLL design included 880MHz-960MHz, 1.92GHz-2.17GHz, 2.3GHz-2.7GHz, 3.3GHz-3.8GHz and 5.15GHz-5.85GHz that are used by wireless communication standards such as GSM, UMTS, bluetooth, WiMAX and Wi-Fi etc. This project started with the system level model development for characterizing ADPLL phase noise, fractional spur and locking speed. Then an on-chip jitter detector and parameter adapter was designed for ADPLL to perform self-tuning and self-calibration to accomplish high frequency purity and fast frequency locking in each frequency band. A novel wide band DCO is presented for multi-band wireless application. The proposed wide band adaptive ADPLL was implemented in the IBM 0.13µm CMOS technology. The phase noise performance, the frequency locking speed as well as the tuning range of the digitally controlled oscillator was assessed and agrees well with the theoretical analysis

High Performance Local Oscillator Design for Next Generation Wireless Communication

Local Oscillator (LO) is an essential building block in modern wireless radios. In modern wireless radios, LO often serves as a reference of the carrier signal to modulate or demod- ulate the outgoing or incoming data. The LO signal should be a clean and stable source, such that the frequency or timing information of the carrier reference can be well-defined. However, as radio architecture evolves, the importance of LO path design has become much more important than before. Of late, many radio architecture innovations have exploited sophisticated LO generation schemes to meet the ever-increasing demands of wireless radio performances. The focus of this thesis is to address challenges in the LO path design for next-generation high performance wireless radios. These challenges include (1) Congested spectrum at low radio frequency (RF) below 5GHz (2) Continuing miniaturization of integrated wireless radio, and (3) Fiber-fast (>10Gb/s) mm-wave wireless communication. The thesis begins with a brief introduction of the aforementioned challenges followed by a discussion of the opportunities projected to overcome these challenges. To address the challenge of congested spectrum at frequency below 5GHz, novel ra- dio architectures such as cognitive radio, software-defined radio, and full-duplex radio have drawn significant research interest. Cognitive radio is a radio architecture that opportunisti- cally utilize the unused spectrum in an environment to maximize spectrum usage efficiency. Energy-efficient spectrum sensing is the key to implementing cognitive radio. To enable energy-efficient spectrum sensing, a fast-hopping frequency synthesizer is an essential build- ing block to swiftly sweep the carrier frequency of the radio across the available spectrum. Chapter 2 of this thesis further highlights the challenges and trade-offs of the current LO gen- eration scheme for possible use in sweeping LO-based spectrum analysis. It follows by intro- duction of the proposed fast-hopping LO architecture, its implementation and measurement results of the validated prototype. Chapter 3 proposes an embedded phase-shifting LO-path design for wideband RF self-interference cancellation for full-duplex radio. It demonstrates a synergistic design between the LO path and signal to perform self-interference cancellation. To address the challenge of continuing miniaturization of integrated wireless radio, ring oscillator-based frequency synthesizer is an attractive candidate due to its compactness. Chapter 4 discussed the difficulty associated with implementing a Phase-Locked Loop (PLL) with ultra-small form-factor. It further proposes the concept sub-sampling PLL with time- based loop filter to address these challenges. A 65nm CMOS prototype and its measurement result are presented for validation of the concept. In shifting from RF to mm-wave frequencies, the performance of wireless communication links is boosted by significant bandwidth and data-rate expansion. However, the demand for data-rate improvement is out-pacing the innovation of radio architectures. A >10Gb/s mm-wave wireless communication at 60GHz is required by emerging applications such as virtual-reality (VR) headsets, inter-rack data transmission at data center, and Ultra-High- Definition (UHD) TV home entertainment systems. Channel-bonding is considered to be a promising technique for achieving >10Gb/s wireless communication at 60GHz. Chapter 5 discusses the fundamental radio implementation challenges associated with channel-bonding for 60GHz wireless communication and the pros and cons of prior arts that attempted to address these challenges. It is followed by a discussion of the proposed 60GHz channel- bonding receiver, which utilizes only a single PLL and enables both contiguous and non- contiguous channel-bonding schemes. Finally, Chapter 6 presents the conclusion of this thesis

Piezoelectric thin films for bulk acoustic wave resonator applications:from processing to microwave filters

Bandpass filters for microwave frequencies realized with thin film bulk acoustic wave resonators (FBAR) are a promising alternative to current dielectric or surface acoustic wave filters for use in mobile telecommunication applications. With equivalent performance, FBAR filters are significantly smaller than dielectric filters and allow for a larger power operation than SAW filters. In addition, FBARs offer the possibility of on-chip integration, which will result in substantial volume and cost reduction. The first passive FBAR devices are now appearing on the market. They mainly cover needs in miniaturized RF-filters for the new bands around 2 GHz. A FBAR is essentially a thin piezoelectric plate sandwiched between two electrodes and acoustically isolated from the environment for energy trapping purposes. If the isolation is effectuated by an acoustic Bragg reflector, one speaks of solidly mounted resonators (SMR). Piezoelectric aluminum nitride (AlN) thin films are predominantly used in the emerging FBAR technology because AlN exhibits a sufficient electromechanical coupling coefficient kt2 , low acoustic losses at microwave frequencies, a low temperature coefficient of frequency, and its chemical composition is compatible with CMOS requirements. This thesis has two research directions. In the first part, FBAR structures based on AlN thin films were investigated for applications at X-band frequencies (7.2-8.5 GHz), i.e. operating at much higher frequencies than the ones used for present products. The goal was to identify property limitations related to such high frequencies, and to demonstrate to industry high performing SMR filters at 8 GHz. In the second part, a new material for FBAR devices was studied. The motivation is that AlN allows for a restricted filter bandwidth only, limited by its coupling factor of maximal 7%. Monocrystalline KNbO3 appears as an ideal alternative with its high coupling factor kt2 of 47%, and relatively large sound velocity of 8125m/s for longitudinal waves along the [101] direction. Piezoelectricity of KNbO3 films grown on electrodes has never been characterized. Single crystal results indicate that the optimal film texture would be (101). In this thesis, the growth of KNbO3 films on Pt electrodes was studied with the goal to achieve this texture uniformly, and to characterize piezoelectric properties. X-band FBAR's were first studied with numerical simulations based on a one-dimensional theory of the thickness-extensional bulk acoustic wave (BAW). Thickness, acoustic properties and electrical conductivity of the electrodes have a large impact on the resonator characteristics. There are conflicting requirements with respect to optimum acoustic and electrical properties of the electrode materials. An optimum thickness was calculated for 8GHz FBARs that use Pt bottom and Al top electrodes. The characteristics of ladder filters have been calculated based on the impedances of single resonators. The adjustable filter parameters, i.e. the areas of series and shunt resonators, frequency de-tuning between series and parallel resonators, and number of π-sections were screened for a process window offering maximum filter bandwidth with lowest ripple and low insertion loss for a given out-of-band rejection. An important result of the numerical simulations was that the bandwidth of ladder filters can be doubled by de-tuning the series and parallel resonators by more (1.3 times) than the difference of resonance and anti-resonance frequency. This also leads to a flatter passband while keeping the ripples below ±0.2dB. Solidly mounted resonators and filters were fabricated using an acoustic multilayer reflector consisting of AlN and SiO2 λ/4 layers. All films were sputter deposited in a high vacuum sputter cluster system with 4 process chambers. The films were patterned using standard photolithography and dry etching processes. The SMR exhibited a strong and spurious-free resonance at 8GHz with a high quality factor of 360 and electromechanical coupling coefficient of 6.0%. The temperature coefficient of frequency was -18ppm/K, and the voltage coefficient of frequency was -72ppm/V. Passband ladder filters with T- and π-topology consisting of 3 to 14 SMR were successfully demonstrated with a center frequency of 8GHz. These filters were optimized for maximum bandwidth and exhibited an insertion loss of 5.5dB, a rejection of 32dB, a 0.2dB bandwidth of 99MHz (1.3%), and a 3dB bandwidth of 224MHz (2.9%). There was good correspondence between measured and simulated filter and resonator characteristics. For perfect agreement, parasitic elements needed to be taken into account. These were a series resistance of 5Ω and a parallel conductance of 2mS in case of single resonators. The series resistance can be explained with resistive losses in the electrodes, whereas the parallel conduction was due to conduction along the surface. For π-filters, an additional series inductance of 100pH was needed to obtain a satisfactory fit. This inductance increased the out-of band rejection and insertion loss. Besides the group delay variation, all industrial specifications were met. KNbO3 was in-situ sputter deposited at 500 to 600°C using a rf magnetron source. A dedicated sputter chamber with load-lock and oxygen resistant substrate heater was built for this purpose. The high volatility of potassium oxide requires a potassium enrichment of the target. Targets with several excess concentrations (in the form of K2CO3) were studied. Stoichiometric KNbO3 films were obtained with targets containing 25 and 40% excess K. Zero and 10% excess yielded K deficient films, whereas 100% and 200% excess K led to highly unstable targets with K accumulation on the target surface, resulting in K rich second phases. The potassium-to-niobium ratio in the films depends strongly on sputter pressure and substrate temperature. Dense films, nucleated with cubic {100} texture, were obtained on platinized silicon substrates with a 10nm thick IrO2 seed layer at substrate temperatures of 520°C. At lower temperatures the films were amorphous, and at higher temperatures the films were composed of individual and facetted KNbO3 grains. The cubic high-temperature {100} texture results in a mixed (101)/(010) texture in the orthorhombic room temperature phase. The measured relative permitivity of 420 indicates that both orientations are equally present. Micro-Raman confirms the orthorhombic line splitting. Piezoelectrical and ferroelectrical activity were verified by means of a piezoelectric sensitive atomic force microscope. A very large piezoelectric activity was observed on some of the grains, and the polarization could be switched on most of the grains. However, the average d33,f = e33/c33, as measured by means of laser interferometry, showed a modest value of 24pm/V. The effective coupling factor is derived as kt2=2.8%, which is small relative to the theoretical value of 47%. The high dielectric constant and the absence of piezoelectric activity along the [010] direction are responsible for the reduction of the kt2 factor. Film roughness, complexity of deposition process and open poling issue make KNbO3 integration into BAW devices a difficult task

High Performance Optical Transmitter Ffr Next Generation Supercomputing and Data Communication

High speed optical interconnects consuming low power at affordable prices are always a major area of research focus. For the backbone network infrastructure, the need for more bandwidth driven by streaming video and other data intensive applications such as cloud computing has been steadily pushing the link speed to the 40Gb/s and 100Gb/s domain. However, high power consumption, low link density and high cost seriously prevent traditional optical transceiver from being the next generation of optical link technology. For short reach communications, such as interconnects in supercomputers, the issues related to the existing electrical links become a major bottleneck for the next generation of High Performance Computing (HPC). Both applications are seeking for an innovative solution of optical links to tackle those current issues. In order to target the next generation of supercomputers and data communication, we propose to develop a high performance optical transmitter by utilizing CISCO Systems®\u27s proprietary CMOS photonic technology. The research seeks to achieve the following outcomes: 1. Reduction of power consumption due to optical interconnects to less than 5pJ/bit without the need for Ring Resonators or DWDM and less than 300fJ/bit for short distance data bus applications. 2. Enable the increase in performance (computing speed) from Peta-Flop to Exa-Flops without the proportional increase in cost or power consumption that would be prohibitive to next generation system architectures by means of increasing the maximum data transmission rate over a single fiber. 3. Explore advanced modulation schemes such as PAM-16 (Pulse-Amplitude-Modulation with 16 levels) to increase the spectrum efficiency while keeping the same or less power figure. This research will focus on the improvement of both the electrical IC and optical IC for the optical transmitter. An accurate circuit model of the optical device is created to speed up the performance optimization and enable co-simulation of electrical driver. Circuit architectures are chosen to minimize the power consumption without sacrificing the speed and noise immunity. As a result, a silicon photonic based optical transmitter employing 1V supply, featuring 20Gb/s data rate is fabricated. The system consists of an electrical driver in 40nm CMOS and an optical MZI modulator with an RF length of less than 0.5mm in 0.13&mu m SOI CMOS. Two modulation schemes are successfully demonstrated: On-Off Keying (OOK) and Pulse-Amplitude-Modulation-N (PAM-N N=4, 16). Both versions demonstrate signal integrity, interface density, and scalability that fit into the next generation data communication and exa-scale computing. Modulation power at 20Gb/s data rate for OOK and PAM-16 of 4pJ/bit and 0.25pJ/bit are achieved for the first time of an MZI type optical modulator, respectively

Ferroelectric-on-Silicon Switchable Bulk Acoustic Wave Resonators and Filters for RF Applications.

Todays’ multi-band mobile phones’ RF front ends require separate transceivers for each frequency band. Future wireless mobile devices are expected to accommodate a larger number of frequency bands; therefore using the existing transceiver configurations becomes prohibitive. One of the key RF components in wireless devices is the image reject and band-selection filter. Today’s multi-band mobile phones use bulk acoustic wave (BAW) filters in conjunction with solid-state or MEMS-based RF switches for selecting the frequency band of operation. This approach results in very complex circuits. As number of frequency bands increases, ferroelectric BST, operating at its paraelectric phase, has recently been utilized in designing intrinsically switchable BAW resonators and filters due to its voltage induced piezoelectricity. The intrinsically switchable BAW resonators and filters are suitable for designing compact multiband and frequency agile transceivers as they can be switched on and off by simply controlling the dc bias voltage across the ferroelectric layer instead of using separate MEMS or solid-state based RF switches. In this thesis, composite ferroelectric resonators are studied to improve the Q of intrinsically switchable BAW resonators. Intrinsically switchable BAW resonators with record Q values based on ferroelectric-on-silicon composite structures have been demonstrated. In addition, two types of intrinsically switchable BAW filters using ferroelectric-on-silicon composite structure: electrically connected filters and laterally coupled acoustic filters are studied. In the first part of this thesis, the design, fabrication and measurement results for high-Q composite film bulk acoustic resonators (FBARs) are discussed. Subsequently, an intrinsically switchable electrically connected filter based on ferroelectric-on-silicon composite FBARs is presented. Finally, an intrinsically switchable laterally coupled acoustic filter with a ferroelectric-on-silicon composite structure is presented. The reported laterally coupled acoustic filter represents the first demonstration of a BST based intrinsically switchable acoustically coupled filter.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/107289/1/siss_1.pd

Robust Design With Increasing Device Variability In Sub-Micron Cmos And Beyond: A Bottom-Up Framework

My Ph.D. research develops a tiered systematic framework for designing process-independent and variability-tolerant integrated circuits. This bottom-up approach starts from designing self-compensated circuits as accurate building blocks, and moves up to sub-systems with negative feedback loop and full system-level calibration. a. Design methodology for self-compensated circuits My collaborators and I proposed a novel design methodology that offers designers intuitive insights to create new topologies that are self-compensated and intrinsically process-independent without external reference. It is the first systematic approaches to create "correct-by-design" low variation circuits, and can scale beyond sub-micron CMOS nodes and extend to emerging non-silicon nano-devices. We demonstrated this methodology with an addition-based current source in both 180nm and 90nm CMOS that has 2.5x improved process variation and 6.7x improved temperature sensitivity, and a GHz ring oscillator (RO) in 90nm CMOS with 65% reduction in frequency variation and 85ppm/oC temperature sensitivity. Compared to previous designs, our RO exhibits the lowest temperature sensitivity and process variation, while consuming the least amount of power in the GHz range. Another self-compensated low noise amplifiers (LNA) we designed also exhibits 3.5x improvement in both process and temperature variation and enhanced supply voltage regulation. As part of the efforts to improve the accuracy of the building blocks, I also demonstrated experimentally that due to "diversification effect", the upper bound of circuit accuracy can be better than the minimum tolerance of on-chip devices (MOSFET, R, C, and L), which allows circuit designers to achieve better accuracy with less chip area and power consumption. b. Negative feedback loop based sub-system I explored the feasibility of using high-accuracy DC blocks as low-variation "rulers-on-chip" to regulate high-speed high-variation blocks (e.g. GHz oscillators). In this way, the trade-off between speed (which can be translated to power) and variation can be effectively de-coupled. I demonstrated this proposed structure in an integrated GHz ring oscillators that achieve 2.6% frequency accuracy and 5x improved temperature sensitivity in 90nm CMOS. c. Power-efficient system-level calibration To enable full system-level calibration and further reduce power consumption in active feedback loops, I implemented a successive-approximation-based calibration scheme in a tunable GHz VCO for low power impulse radio in 65nm CMOS. Events such as power-up and temperature drifts are monitored by the circuits and used to trigger the need-based frequency calibration. With my proposed scheme and circuitry, the calibration can be performed under 135pJ and the oscillator can operate between 0.8 and 2GHz at merely 40[MICRO SIGN]W, which is ideal for extremely power-and-cost constraint applications such as implantable biomedical device and wireless sensor networks

The Resonant Body Transistor

With quality factors (Q) often exceeding 10,000, vibrating micromechanical resonators have emerged as leading candidates for on-chip versions of high-Q resonators used in wireless communications systems, sensor networks, and clocking sources in microprocessors. However, extending the frequency of MEMS resonators generally entails scaling of resonator dimensions leading to increased motional impedance. In this dissertation, I introduce a new transduction mechanism using dielectric materials to improve performance and increase frequency of silicon-based RF acoustic resonators. Traditionally, electrostatically transduced mechanical resonators have used air-gap capacitors for driving and sensing vibrations in the structure. To increase transduction efficiency, facilitate fabrication, and enable GHz frequencies of operation, it is desirable to replace air-gap transducers with dielectric films. In my doctoral work, I designed, fabricated, and demonstrated dielectrically transduced silicon bulk-mode resonators up to 6.2 GHz, marking the highest acoustic frequency measured in silicon to date. The concept of internal dielectric transduction is introduced, in which dielectric transducers are incorporated directly into the resonator body. With dielectric films positioned at points of maximum strain in the resonator, this transduction improves in efficiency with increasing frequency, enabling resonator scaling to previously unattainable frequencies. Using internal dielectric transduction, longitudinal-mode resonators exhibited the highest frequency-quality factor (f.Q) product in silicon to date at 5.1 x 10 exp(13) s exp(-1) . These resonators were measured by capacitively driving and sensing acoustic vibrations in the device. However, capacitive detection often requires 3-port scalar mixer measurement, complicating monolithic integration of the resonators with CMOS circuits. The internal dielectric bulk-mode resonators can be utilized in a 2-port configuration with capacitive drive and piezoresistive detection, in which carrier mobility is dynamically modulated by elastic waves in the resonator. Piezoresistive sensing of silicon-based dielectrically transduced resonators was demonstrated with 1.6% frequency tuning and control of piezoresistive transconductance gm by varying the current flowing through the device. Resonant frequency, determined by lithographically defined dimensions, was demonstrated over a wide frequency range. These degrees of freedom enable acoustic resonators spanning a large range of frequencies on a single chip, despite design restrictions of the CMOS process. As we scale to deep sub-micron (DSM) technology, transistor cut-off frequencies increase, enabling the design of CMOS circuits for RF and mm-wave applications greater than 60 GHz. However, DSM transistors have limited gain and integrated passives demonstrate low Q, resulting in poor efficiency. A successful transition into DSM CMOS requires enhanced-gain and high-Q components operating at microwave frequencies. In this work, a merged NEMS-CMOS device is introduced that can function as a building block to enhance the performance of RF circuits. The device, termed the Resonant Body Transistor (RBT), consists of a field effect transistor embedded in the body of a high-frequency NEMS resonator implementing internal dielectric transduction. The results of this work indicate improved resonator performance with increased frequency, providing a means of scaling MEMS resonators to previously unattainable frequencies in silicon. With the transduction methods developed in this work, a hybrid NEMSCMOS RBT enables low-power, narrow-bandwidth low noise amplifier design for transceivers and low phase-noise oscillator arrays for clock generation and temperature sensing in microprocessors

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

CMOS compatible solidly mounted resonator for air quality monitoring

Air pollution has become a growing concern around the world. Human exposure to hazardous air pollutants is associated with a range of health problems and increased mortality. An estimated 40,000 early deaths per year are caused by the exposure to air pollutants in the UK alone, which cost over £20 billion annually to individuals and health services1. In this work, novel solidly mounted resonator (SMR) devices were developed for integration in a low-cost, portable air quality monitor for the real-time monitoring of particulate matter and volatile organic compounds (VOCs). Finite element models of the SMRs were developed to aid their design and simulate the response of the sensors to particles and exposure to VOCs. For particle sensing, a SMR based unit was developed, working in a dual mode configuration. The unit was characterised inside an environmental chamber, together with commercial reference instruments, to particles of known size and composition. A detection limit of 20 μg/m3 was found (below the safe exposure limit). To target fine particles (<2.5 μm), a virtual impactor was incorporated into the system. For VOC detection, the SMR devices were functionalised with polymer coatings to detect acetone and toluene vapours (most common VOCs in air). A polymer drop-coating system was developed to complete this aim (polymer film thicknesses <100nm). An automated VOC test station was developed to characterise the SMR based sensors to low ppm concentrations of the target vapours (<200 ppm). The SMR devices demonstrated a limit of detection of 5 ppm to toluene and 50 ppm of acetone (well below the safe exposure limits). A novel CMOS based SMR device, suitable for volume production and monolithic integration, was designed with an integrated microheater and CMOS acoustic mirror. The heater was included to vary the temperature of the sensing area (to enhance the sensitivity of the SMR to a particular VOC through temperature modulation or to clear particles off the surface). The fabricated device (1.9 GHz) exhibited good performance