A SPICE Model of Transmission Lines Transformer (TLT)

摘要

Transmission line transformers (TLT) are widely used in antennas and RF broadband matching circuits. There are many constructive types, the balun is one of them, however this paper focus on the simpler inverting TLT. The classical theory for TLT uses two different approaches to model the low frequency and high frequency operation. The limit between the low frequency lumped circuit model and the high frequency distributed model (single transmission line) is sometimes unclear. The paper present a model for the TLT as an assembly of two coupled symmetrical lossless lines with common return. The aim of the paper is to analytically and experimentally validate such an approach, and then, based on this analysis, to find a SPICE model for the TLT which can be used across the whole frequency range, taking into account the influence of the core.