Interwound and concentric Ruthroff 1∶4 transmission-line transformers using coupled microstrip lines

The goal of this paper is to compare two configurations of Ruthroff un-to-un 1:4 TLT using coupled microstrip lines. Concentric and interwound Transmission line transformers were simulated by HFSS simulator. The simulated minimum insertion losses of the concentric and interwound TLTs are 0.27 dB at 5.4 GHz and 0.26 dB at 4.5 GHz, respectively. The correspondent bandwidths of these TLTs are 7.22 GHz and 3.59 GHz (when the return loss exceeds 10 dB). The chip areas of these TLTs are 1.26 mm × 0.76 mm and 1.18 mm × 0.68 mm.