A Low Jitter Wideband Fractional-N Subsampling Phase Locked Loop (SSPLL)

Frequency synthesizers have become a crucial building block in the evolution of modern communication systems and consumer electronics. The spectral purity performance of frequency synthesizers limits the achievable data-rate and presents a noise-power tradeoff. For communication standards such as LTE where the channel spacing is a few kHz, the synthesizers must provide high frequencies with sufficiently wide frequency tuning range and fine frequency resolutions. Such stringent performance must be met with a limited power and small chip area. In this thesis a wideband fractional-N frequency synthesizer based on a subsampling phase locked loop (SSPLL) is presented. The proposed synthesizer which has a frequency resolution less than 100Hz employs a digital fractional controller (DFC) and a 10-bit digital-to-time converter (DTC) to delay the rising edges of the reference clock to achieve fractional phase lock. For fast convergence of the delay calibration, a novel two-step delay correlation loop (DCL) is employed. Furthermore, to provide optimum settling and jitter performance, the loop transfer characteristics during frequency acquisition and phase-lock are decoupled using a dual input loop filter (DILF). The fractional-N sub-sampling PLL (FNSSPLL) is implemented in a TSMC 40nm CMOS technology and occupies a total active area of 0.41mm^2. The PLL operates over frequency range of 2.8 GHz to 4.3 GHz (42% tuning range) while consuming 9.18mW from a 1.1V supply. The integrated jitter performance is better than 390 fs across all fractional frequency channel. The worst case fractional spur of -48.3 dBc occurs at a 650 kHz offset for a 3.75GHz fractional channel. The in-band phase noise measured at a 200 kHz offset is -112.5 dBc/Hz

Optical Lattice Clock with Spin-1/2 Ytterbium Atoms

An optical lattice clock probes a spectrally narrow electronic transition in an ensemble of optically trapped, laser-cooled atoms, for use as a time and frequency standard. To date, several lattice clocks have been demonstrated with superior stability and accuracy compared to primary frequency standards based on microwave transitions. Yet, the question of which atomic system (including the element and isotope) performs best as a lattice clock remains unsettled. This thesis describes the first detailed investigation of an optical lattice clock using a spin-1/2 isotope of the ytterbium atom. A spin-1/2 system possesses several advantages over higher-spin systems, including a simplified level structure (allowing for straightforward manipulation of the nuclear spin state) and the absence of any tensor light shift from the confining optical lattice. Moreover, the ytterbium atom (Yb) stands among the leading lattice clock candidates, offering a high-performance optical clock with some degree of experimental simplicity. The frequency stability of the Yb clock is highlighted by resolving an ultra-narrow clock spectrum with a full-width at half-maximum of 1 Hz, corresponding to a record quality factor Q = ν0/Δν = 5 × 1014. Moreover, this system can be highly accurate, which is demonstrated by characterizing the Yb clock frequency at the 3 × 10−16 level of fractional uncertainty, with further progress toward a ten-fold improvement also presented. To reach this low level of uncertainty required careful consideration of important systematic errors, including the identification of the Stark-canceling wavelength, where the clock’s sensitivity to the lattice intensity is minimized, a precise determination of the static polarizability of the clock transition, and the measurement and control of atom-atom collisions

Ultra Low-Power Frequency Synthesizers for Duty Cycled IoT radios

Internet of Things (IoT), which is one of the main talking points in the electronics industry today, consists of a number of highly miniaturized sensors and actuators which sense the physical environment around us and communicate that information to a central information hub for further processing. This agglomeration of miniaturized sensors helps the system to be deployed in previously impossible arenas such as healthcare (Body Area Networks - BAN), industrial automation, real-time monitoring environmental parameters and so on; thereby greatly improving the quality of life. Since the IoT devices are usually untethered, their energy sources are limited (typically battery powered or energy scavenging) and hence have to consume very low power. Today's IoT systems employ radios that use communication protocols like Bluetooth Smart; which means that they communicate at data rates of a few hundred kb/s to a few Mb/s while consuming around a few mW of power. Even though the power dissipation of these radios have been decreasing steadily over the years, they seem to have reached a lower limit in the recent times. Hence, there is a need to explore other avenues to further reduce this dissipation so as to further improve the energy autonomy of the IoT node. Duty cycling has emerged as a promising alternative in this sense since it involves radios transmitting very short bursts of data at high rates and being asleep the rest of the time. In addition, high data rates proffer the added advantage of reducing network congestion which has become a major problem in IoT owing to the increase in the number of sensor nodes as well as the volume of data they send. But, as the average power (energy) dissipated decreases due to duty cycling, the energy overhead associated with the start-up phase of the radio becomes comparable with the former. Therefore, in order to take full advantage of duty cycling, the radio should be capable of being turned ON/OFF almost instantaneously. Furthermore, the radio of the future should also be able to support easy frequency hopping to improve the system efficiency from an interference point of view. In other words, in addition to high data rate capability, the next generation radios must also be highly agile and have a low energy overhead. All these factors viz. data rate, agility and overhead are mainly dependent on the radio's frequency synthesizer and therefore emphasis needs to be laid on developing new synthesizer architectures which are also amenable to technology scaling. This thesis deals with the evolution of one such all-digital frequency synthesizer; with each step dealing with one of the aforementioned issues. In order to reduce the energy overhead of the synthesizer, FBAR resonators (which are a class of MEMS resonators) are used as the frequency reference instead of a traditional quartz crystal. The FBAR resonators aid the design of fast-startup oscillators as opposed to the long latency associated with the start-up of the crystal oscillator. In addition, the frequency stability of the FBAR lends itself to open-loop architecture which can support very high data rates. Another advantage of the open-loop architecture is the frequency agility which aids easy channel switching for multi-hop architectures, as demonstrated in this thesis

Micromachined Magnetoelastic Sensors and Actuators for Biomedical Devices and Other Applications.

Magnetoelastic materials exhibit coupling between material strain and magnetization; this coupling provides the basis for a number of wireless transducers. This thesis extends past work on microfabricated magnetoelastic sensors in three ways. First, a new class of strain sensors based on the ΔE effect are presented. Two sensor types are described – single and differential. The single sensor has an active area of 7×2 mm2 and operates at a resonant frequency of 230.8 kHz with a sensitivity of 13×103 ppm/mstrain and a dynamic range of 0.05-1.05 mstrain. The differential sensor includes a strain-independent 2×0.5 mm2 reference resonator in addition to a 2.5×0.5 mm2 sensing element. The sensor resonance is at 266.4 kHz and reference resonance is at 492.75 kHz. The differential sensor has a dynamic range of 0-1.85 mstrain, a sensitivity of 12.5×103¬¬ ppm/mstrain, and is temperature compensated in the 23-60°C range. Second, fluidic actuation by resonant magnetoelastic devices is presented. This transduction is performed in the context of an implantable device, specifically the Ahmed glaucoma drainage device (AGDD). Aspherical 3D wireless magnetoelastic actuators with small form factors and low surface profiles are integrated with the AGDD; the fluid flow generated by the actuators is intended to limit cellular adhesion to the implant surface that ultimately leads to implant encapsulation and failure. The actuators measure 10.3×5.6 mm2 with resonant frequencies varying from 520 Hz to 4.7 kHz for the different actuator designs. Flow velocities up to 266 μm/s are recorded at a wireless activation range of 25-30 mm, with peak actuator vibration amplitudes of 1.5 μm. Finally, detection techniques for improving the measurement performance of wireless magnetoelastic systems are presented. The techniques focus on decoupling of the excitation magnetic signal from the sensor response to improve measurement sensitivity and noise immunity. Three domains – temporal, frequency, and spatial – are investigated for signal feedthrough. Quantitative results are presented for temporal and frequency domain decoupling. Temporal decoupling is used to measure strain sensors with resonant frequencies in the 125 kHz range, whereas frequency domain decoupling is implemented to measure 44 kHz magnetoelastic resonators.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/116647/1/venkatp_1.pd

Collective analog bioelectronic computation

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 677-710).In this thesis, I present two examples of fast-and-highly-parallel analog computation inspired by architectures in biology. The first example, an RF cochlea, maps the partial differential equations that describe fluid-membrane-hair-cell wave propagation in the biological cochlea to an equivalent inductor-capacitor-transistor integrated circuit. It allows ultra-broadband spectrum analysis of RF signals to be performed in a rapid low-power fashion, thus enabling applications for universal or software radio. The second example exploits detailed similarities between the equations that describe chemical-reaction dynamics and the equations that describe subthreshold current flow in transistors to create fast-and-highly-parallel integrated-circuit models of protein-protein and gene-protein networks inside a cell. Due to a natural mapping between the Poisson statistics of molecular flows in a chemical reaction and Poisson statistics of electronic current flow in a transistor, stochastic effects are automatically incorporated into the circuit architecture, allowing highly computationally intensive stochastic simulations of large-scale biochemical reaction networks to be performed rapidly. I show that the exponentially tapered transmission-line architecture of the mammalian cochlea performs constant-fractional-bandwidth spectrum analysis with O(N) expenditure of both analysis time and hardware, where N is the number of analyzed frequency bins. This is the best known performance of any spectrum-analysis architecture, including the constant-resolution Fast Fourier Transform (FFT), which scales as O(N logN), or a constant-fractional-bandwidth filterbank, which scales as O (N2).(cont.) The RF cochlea uses this bio-inspired architecture to perform real-time, on-chip spectrum analysis at radio frequencies. I demonstrate two cochlea chips, implemented in standard 0.13m CMOS technology, that decompose the RF spectrum from 600MHz to 8GHz into 50 log-spaced channels, consume < 300mW of power, and possess 70dB of dynamic range. The real-time spectrum analysis capabilities of my chips make them uniquely suitable for ultra-broadband universal or software radio receivers of the future. I show that the protein-protein and gene-protein chips that I have built are particularly suitable for simulation, parameter discovery and sensitivity analysis of interaction networks in cell biology, such as signaling, metabolic, and gene regulation pathways. Importantly, the chips carry out massively parallel computations, resulting in simulation times that are independent of model complexity, i.e., O(1). They also automatically model stochastic effects, which are of importance in many biological systems, but are numerically stiff and simulate slowly on digital computers. Currently, non-fundamental data-acquisition limitations show that my proof-of-concept chips simulate small-scale biochemical reaction networks at least 100 times faster than modern desktop machines. It should be possible to get 103 to 106 simulation speedups of genome-scale and organ-scale intracellular and extracellular biochemical reaction networks with improved versions of my chips. Such chips could be important both as analysis tools in systems biology and design tools in synthetic biology.by Soumyajit Mandal.Ph.D

Design and analysis techniques for nano-joule ADCs and sampling linearity

Two aspects of ADC system performance are addressed in this work. First, the combination of the ADC and its associated reference are co-designed for an energy constrained remote sensing system. Second, sampling linearity is mathematically analyzed as a function of frequency to provide enhanced understanding into an ADC's requisite sampling network. Low energy analog design techniques for emerging systems powered by energy scavenging are demonstrated in the context of an analog-to-digital converter system. It is composed of a variable gain sample-and-hold amplifier, a low voltage reference, a 1.5 bit per stage 9-b cyclic ADC, clock generation, reference buffers, and control logic. A novel Class-AB current mirror amplifier together with correlated level shifting enable wide swing and enhanced gain operation at low supply voltages while reducing current draw. The use of subthreshold MOSFETs instead of bipolar junction transistors allows the use of traditional bandgap circuit techniques to be employed for a 530 mV reference that is less than a diode voltage drop. Operating from a 750 mV supply voltage and 20.48 kSPS, the ADC and reference consume 9.5μA and 1.5μA, respectively. The measured 7.9-bit ENOB results in an FoM of 2.24 pJ/step. The total energy consumption is 535 pJ per conversion for the entire system. A novel model predicts tracking nonlinearity (NL) in the form of harmonic distortion (HD) for weakly NL (i.e. SFDR>30dBc) first order open-loop sampling circuits. The mechanisms for the NL are exponential settling, amplitude modulation, phase modulation and discrete-time modulation. The model demonstrates that HD typically increases at 20 dB per decade over most standard operating ranges and is a function of input frequency, sampling bandwidth, input amplitude, the sample rate and component nonlinearity. Application of the model is reduced to the equivalent of frequency-independent nonlinearity analysis over this range, requiring only a Taylor series expansion of the NL time constant. Design insight is given for common MOS switch types, revealing a high correlation between HD and bandwidth. The first method to quantify the trade-off between thermal noise (SNR) and linearity (SFDR) for sampling circuits is presented. Measured HD2, HD3, HD4, and HD5 versus frequency at multiple sample rates of a Sample and Hold test chip fabricated in a 0.25μm 1P5M CMOS process and Spectre simulation results support the findings. The results broadly apply to switched capacitor circuits in general and sampling circuits specifically, regardless of technology

Performance limits in optical communications due to fiber nonlinearity

In this paper, we review the historical evolution of predictions of the performance of optical communication systems. We will describe how such predictions were made from the outset of research in laser based optical communications and how they have evolved to their present form, accurately predicting the performance of coherently detected communication systems

Space programs summary no. 37-62, volume 2 for the period 1 January - 28 February 1970. The Deep Space Network

Deep Space Network operations revie

Mu2e Technical Design Report

The Mu2e experiment at Fermilab will search for charged lepton flavor violation via the coherent conversion process mu- N --> e- N with a sensitivity approximately four orders of magnitude better than the current world's best limits for this process. The experiment's sensitivity offers discovery potential over a wide array of new physics models and probes mass scales well beyond the reach of the LHC. We describe herein the preliminary design of the proposed Mu2e experiment. This document was created in partial fulfillment of the requirements necessary to obtain DOE CD-2 approval.Comment: compressed file, 888 pages, 621 figures, 126 tables; full resolution available at http://mu2e.fnal.gov; corrected typo in background summary, Table 3.