• About
  • Policies
  • What is openaccess
  • Library
  • Contact
Advanced search
      View Item 
      •   BUIR Home
      • University Library
      • Bilkent Theses
      • Theses - Department of Electrical and Electronics Engineering
      • Dept. of Electrical and Electronics Engineering - Master's degree
      • View Item
      •   BUIR Home
      • University Library
      • Bilkent Theses
      • Theses - Department of Electrical and Electronics Engineering
      • Dept. of Electrical and Electronics Engineering - Master's degree
      • View Item
      JavaScript is disabled for your browser. Some features of this site may not work without it.

      Optimization of coupled Class-E RF power amplifiers for a transmit array system in 1.5T MRI

      Thumbnail
      View / Download
      7.2 Mb
      Author
      Aldemir, Muhammed Said
      Advisor
      Atalar, Ergin
      Date
      2020-02
      Publisher
      Bilkent University
      Language
      English
      Type
      Thesis
      Item Usage Stats
      142
      views
      115
      downloads
      Abstract
      Radio Frequency (RF) field is generated mostly by linear RF power amplifiers in Magnetic Resonance Imaging (MRI). These amplifiers have relatively low efficiency and are placed far from the transmit coil in MRI system room. Additional cooling systems and long transmission cables increase the cost of MRI hardware. Coupled Class-E on-coil RF amplifiers for a Transmit Array System is proposed instead of linear RF amplifiers. Class-E RF amplifier is a nonlinear switching amplifier which has 100% drain efficiency ideally. State-space models for single Class-E amplifier and coupled Class-E amplifiers are derived and steady-state operation of coupled Class-E amplifiers is investigated. The state-space models are verified with the simulation results of the Class-E amplifier. Effect of coupling between channels on the output characteristics of the transmit system is observed. Instead of implementing decoupling methods, coupling is maintained and optimization of circuit parameters for coupled Class-E amplifiers is proposed to achieve high drain efficiency and high output RF power. Output power of 600 W and overall drain efficiency higher than 90% are achieved by two coupled Class-E amplifiers even with high coupling levels in the state-space model. Power and efficiency measurements are done with coupled amplifiers and MRI experiments are performed in 1.5T Scimedix MRI Scanner. In conclusion, coupled Class-E RF power amplifiers can be operated as on-coil amplifiers in a Transmit Array system with high output characteristics by optimization of circuit parameters.
      Keywords
      RF power
      Class-E amplifier
      Coupling
      Transmit array system
      Permalink
      http://hdl.handle.net/11693/53323
      Collections
      • Dept. of Electrical and Electronics Engineering - Master's degree 594
      Show full item record

      Browse

      All of BUIRCommunities & CollectionsTitlesAuthorsAdvisorsBy Issue DateKeywordsTypeDepartmentsThis CollectionTitlesAuthorsAdvisorsBy Issue DateKeywordsTypeDepartments

      My Account

      Login

      Statistics

      View Usage StatisticsView Google Analytics Statistics

      Bilkent University

      If you have trouble accessing this page and need to request an alternate format, contact the site administrator. Phone: (312) 290 1771
      Copyright © Bilkent University - Library IT

      Contact Us | Send Feedback | Off-Campus Access | Admin | Privacy