Voltage gain optimization of transmission line transformers

Laboratoire de Génie Électrique, Université de Pau, Hélioparc Pau Pyrénées, 64053 Pau Cedex 9, France

Corresponding author: laurent.pecastaing@univ-pau.fr

Received: 19 July 2002
Revised: 12 December 2002
Accepted: 24 January 2003
Published online: 14 May 2003

Abstract

Transmission Line Transformers (TLT) based on the use of ferrite beads are presented. This work aims at optimising the performance of the voltage gain and the compactness of the TLT according to the position, the type and the number of ferrites used. The ferrites have been selected taking into account two main parameters: the maximum currents flowing through the outer conductor of the lines of a TLT without ferrite beads and the current frequencies. The function of these ferrites is to decrease the effect of parasitic short-circuit transmission lines between the outer conductors of the coaxial cables of the TLT. Voltages and secondary currents are measured on each cable. The voltage gain achieved reaches the optimum theoretical value thanks to the use of ferrites for a 2, 4 and 10-stage transmission line transformer. Each cable is shorter than 1.5 meter in length which provides an unquestionable advantage of compactness.