Seminars and Defenses

Feb. 9, 10A, ENG471
Krishnanand Balasundaram • PHD INTERNAL THESIS DEFENSE
Morphologically Constrained Adaptive Signal Decomposition in Studying Ventricular Arrhythmias
Ventricular fibrillation (VF), a lethal form of ventricular arrhythmias (VA), originates from the lower chambers of the heart and is one of the major causes for sudden cardiac deaths (SCD). Since the duration from the onset of VF to SCD is only few minutes, it is difficult to study VF and it is even harder to perform invasive diagnosis or provide treatment within the short window of time. This dissertation proposes methods to extract meaningful information from VF electrograms and formulate associations to underlying structural and physiological properties of the cardiac tissue and clinical events of interest during VF. In other words, by analyzing clues in the electrograms during VF, the method can be used to infer the underlying anatomical and physiological properties of the cardiac tissue and certain clinical events of interest, which is otherwise not available without invasive procedures. The proposed methods will be of great assistance to cardiologists and cardiac electrophysiologist in the diagnosis and treatment planning of cardiac arrhythmias.
The proposed adaptive time-frequency (TF) signal decomposition was separated into two categories based on two purposes: (1) Time-specific event detection and (2) Time-averaged VA characterization. For the time-specific event detection (in this work rotor detection because rotors are believed to be drivers of VF), electrogram signal features related to the rotor event were identified with an adaptive TF decomposition and a modified criterion function. Using the proposed features and a LDA based classifier with LOO cross validation, overall classification accuracies of 80.77% and 79.41% were achieved in detecting rotor events and separating them from similar but not rotor events.
In the time-averaged ventricular arrhythmia characterization, previously established signal features were used to associate electrogram clues to the structural and physiological characteristics of the cardiac tissue. Using LCKSVD dictionary learning process, dictionaries of TF basis functions were generated to capture specific electric structures and physiological characteristics of the underlying cardiac tissue. The association of these characteristics with the extracted electrogram clues were validated using a cross-validation technique. The cross-validated results obtained were 71.09%, 60.30%, 71.74% and 65.73%, respectively, for the 4 characteristics.
Further to this, to automate and build a function-approximation model with non-linear separable capabilities to capture complex association of the heart characteristics and electrogram signal structures, neural network models were generated. The cross-validated accuracy for the models were 80.77%, 75.73%, 85.00%, 67.71%, 76.83% and 76.88% respectively for each of the developed models.
Jan. 15, 1P, ENG471
Inductive Magnetically Coupled Resonant Wireless Power Transmission System with Planar Coils for the Rezence Efficiency Standard, with a 90% Efficient Class-E Amplifier and Auto-Tuning Circuit Technique for Improved Efficiency
MCR-WPT has helped to increase the WPT distance which the PTU can transmit power efficiently to the PRU. This has enabled their rapid adoption in many applications. In this thesis propose new designs and design methodologies used to meet the Rezence standard for portable electronics, which based on magnetic resonant coupling WPT.
Class E PAs, which achieve 100% theoretical efficiency with simple circuit topology, are difficult to analytically design with equations provided. This thesis presents a HF Class-E PA design methodology that simplifies design. The methodology uses ideal Class-E design equations to generate ideal drain impedances, used to impedance match the power FET output for Class-E operation. A high efficiency Class-E PA was designed using a low cost power MOS by following this design flow.
The small size of these devices makes it difficult to design efficient MCR-WPT resonators. A new multi-layer MCR-WPT PSC design and design methodology is proposed which increases efficiency and decrease SRF of the coils. The design is a modified series stacked spiral inductors without vias, and can be stacked more than 2 layers, and the dielectric substrate changed to a higher permittivity material to improve efficiency and SRF. The design methodology takes advantage of the fast Momentum simulations to give good MCR-WPT system SRF and efficiency predictions.
Efficiency of MCR-WPT Tx and Rx resonators is reduced when the distance between the is less that the CCD due to the frequency splitting phenomenon. This thesis presents an auto-tuning circuit that automatically improve efficiency when the PRU is placed at the optimal region. The tuning is done by a binary counter and discrete capacitor array, and a maximum peak detection technique identifies the optimal tuning capacitance for maximum WPT efficiency.