Compact Wideband Multi-Section Quarter-Wave-Like Transformers with Unequal Electrical Lengths

This paper proposes quarter-wave-like transformers (QWLTs) with unequal electrical lengths to miniaturize multi-section quarter wave transformers (QWTs) and to enhance the bandwidth. The proposed method extends a study of the approximate theory of small reflections (ATSR) for QWLTs called the extended approximate theory of small reflections (EATSR). The total input reflection coefficient is observed in the frequency range of interest. Results of the EATSR for both two-and three-section unit cells with 25% physical size reduction prove that their impedance bandwidths are broader than those of the standard multi-section QWTs and the ATSR for QWLTs.