High-power transmission line transformer design for plasma generators

Efficient and novel design method to implement high-power transmission line transformers (TLTs) that can be used as output balun for plasma generators is presented. The novelty in the presented method involves: the construction of the balun using transmission lines (TLs) in the form of microstrip configuration, which gives higher power handling capacity with larger amount of current and high breakdown voltage, accurate formulation including magnetic design of the balun, such as core selection, flux density, operational current, voltage, and number of turns, and implementation of the balun for radio frequency amplifier section of the plasma generator for the first time. The presented method also integrates Dowell's formulation into microstrip type design and shows that when TLs with rectangular cross sections, such as copper strips, are used for winding, thermal profile of the balun improves since its conductor loss is reduced. Design charts based on analytical formulation to design high-power TLTs are presented. High-power TLT is then constructed, measured, and implemented for 2-MHz plasma generator. All the measurement results, including thermal profile of the TLT and power amplifier performance of the plasma generator at the center frequency, 2 MHz, when the new type of TLT is implemented have been given. It has been shown that the TLT using the design technique presented in this paper can be used as output balun for plasma generators and meet all the requirements of plasma applications.