Electrical and Computer Engineering, Department of
http://hdl.handle.net/1974/768
2017-12-18T05:08:21ZPhase Noise Characterization of a Mode-Locked Quantum-Dot Coherent Optical Frequency Comb Source Laser
http://hdl.handle.net/1974/23758
Phase Noise Characterization of a Mode-Locked Quantum-Dot Coherent Optical Frequency Comb Source Laser
Zanette, Kristian
Modern coherent optical communication systems transmit 100 Gb/s dual-polarization quadrature phase shift keying (DP-QPSK) signals on each of the 100 channels in a dense wavelength division multiplexing (DWDM) system. Each of these channels require an individual optical carrier frequency to be generated from a discrete high-performance tunable laser. These arrays of discrete lasers are an expensive component in the transmitter of an optical communication channel. Thus, recent research has investigated an alternative laser source - optical frequency combs (OFCs). OFCs generate numerous spectral modes, referred to as comb lines, from a single photonic device. Each of these comb lines can be used as an optical carrier frequency for a channel in a DWDM system. Thus, the implementation of an OFC as a laser source for coherent optical communications minimizes the number of laser modules in a DWDM system leading to a drastic reduction in system cost and complexity. Additionally, OFCs exhibit an intrinsic coherence among each comb line across the spectrum. This coherence implies that the phase noise exhibited by each comb line in the OFC is related which allows for effective methods of phase noise compensation. Consequently, OFCs are heavily under research and development.
In this research, a prototype 25 GHz quantum-dot coherent optical frequency comb source laser is characterized in both the time and frequency domains. The output of the comb source laser is extensively observed and the optical and electrical spectra, spectral flatness, relative intensity noise, phase noise, linewidth and timing jitter are measured. These preliminary results led to the development of a coherent phase noise detection scheme capable of recovering time domain phase noise trajectories for pairs of comb lines. The detection scheme allowed the coherence exhibited by the comb source to be quantified using a correlation coefficient which compared recovered phase noise trajectories for pairs of comb lines. Additionally, the statistical properties of the recovered phase noise trajectories are explored which enables experimental quantification of the relative contribution of amplified spontaneous emission (ASE) noise and timing jitter for each mode. Experimental results are shown to align with theoretical descriptions of phase noise in mode-locked lasers.
MHz Resonant DC-DC Converters with First Cycle Control
http://hdl.handle.net/1974/23749
MHz Resonant DC-DC Converters with First Cycle Control
Mousavian, Seyedhossein
Faster dynamic response and higher power density are the major achievements obtained by increasing the switching frequency of power supplies. However, switching frequencies are limited by topology, control, semiconductor materials, and packaging methods.
To address these issues, the thesis first proposes a new quasi-resonant converter topology reduces the switching components’ voltage stress to half, and nearly eliminates the switching losses in quasi-resonant converters specifically under on-off control strategy.
The second major thesis achievement is the introduction of the first cycle control method that enhances the performance of the so-called ‘on-off’ control method. This method suffers from overvoltage stress and the hard-switching power losses in on-off transients. The proposed first cycle control method substantially alleviates the voltage stress and switching losses. This achievement makes better use of the switches, and paves the way to further increase the on-off rate.
Final contribution is the proposed (ZVT) cell that is introduced to have a fully ZVS on-off control. Simple structure, low number of components, and avoidance of inductive components in the cell are advantages of the circuit. Higher modulation frequency, lower input and output filter sizes, and faster dynamic responses are the benefits of this method. The zero voltage switching operation of all semiconductor components allows the designer to increase the modulation frequency without any significant drop in the overall efficiency.
Recursive Bayesian Filtering Through a Mixture of Gaussian and Discrete Particles
http://hdl.handle.net/1974/23734
Recursive Bayesian Filtering Through a Mixture of Gaussian and Discrete Particles
Manzar, Ahmad
Conventional solutions to nonlinear filtering problems fall into two categories, deterministic and stochastic approaches. While the former is heavily used due to low computational demand, approximation error is tied to their initialization, which causes difficulty during long term application. The latter circumvents this but at the cost of a significant increase in computation. An extremely popular stochastic filter termed the particle filter is especially notorious for this. However its superior performance (over the conventional nonlinear filters) and generality of use makes it ideal in environments where high nonlinearity plagues the state-space model. Estimation error and computational complexity for the particle filter are both related to the number of particles utilized. Yet, many researchers have observed that particles in the vicinity of one another, perhaps because they represent the same state, might be redundant. A new type of filter is proposed where particles in addition to a (linearized) Gaussian component are tracked. This can be seen as a parallel solution to the estimation problem, each component can be separately filtered and constituent outputs summed up to form the filtering distribution. This new filter is then used in two classical scenarios used to benchmark nonlinear filters.
Digital Control Techniques for High Fidelity Haptic Simulation Systems
http://hdl.handle.net/1974/23630
Digital Control Techniques for High Fidelity Haptic Simulation Systems
Cleveland, Daniel
Haptic simulation systems allow human users to kinesthetically interact with virtual environment models through a robotic mechanism known as a haptic interface. The sampled-data nature of haptic interfaces limits the range of virtual environment dynamics that can be stably rendered in a haptic simulation system which limits the available performance of haptic systems. A method of increasing the range of stably implementable virtual environment dynamics, and the focus of this thesis, is through the investigation of different discrete virtual environment implementations. The passivity and uncoupled stability criteria are considered the most stringent conditions on the stability of haptic simulations systems. In this thesis, seven different discretizations of a spring-damper virtual environment are derived and studied using the passivity and uncoupled stability criteria. Traditionally, position-sampling is the method by which feedback is acquired from a haptic system, however, in this thesis the effects of sampling velocity and that of sampling both position and velocity are studied. As well, a single degree-of-freedom haptic device was developed with analog circuitry to implement velocity-sampled and position and velocity-sampled haptic simulation systems. Results indicate that a zero-order-hold position-sampled implementation may provide a larger range of implementable dynamics than the benchmark, backward difference. It was found that the sampled-PV implementation shows great potential to increase the range of implementable dynamics over existing position-sampled implementations.