A broadband and high-efficiency Ruthroff 1:9 transmission-line transformer using coupled microstrip lines

A Ruthroff type spiral un-to-un Transmission - Line Transformer (TLT) with step-up impedance transformation ratio of 1:9 is presented. This TLT is fabricated in microstrip lines technology and covers a chip area of 0.79 mm × 0.84 mm. The simulated minimum insertion loss is 0.29 dB at 5.4 GHz, and the correspondent bandwidth of this TLT is 2.1 GHz (when the return loss exceeds 10 dB).