Broadband and low-loss Ruthroff-type transmission line transformer in integrated passive devices technology

Two broadband, low-loss Ruthroff-type transmission line transformers (TLTs) that are implemented in integrated passive devices (IPD) technology and intended for use in IEEE 802.11b/g WLAN systems are presented in this paper. The TLTs are realized by spiral broadside-coupled lines with proper characteristic impedances to optimize the insertion loss and bandwidth. The measured minimum insertion losses of 1∶4 and 1∶9 TLTs are 0.5 dB at 2.2 GHz and 0.57 dB at 2.4 GHz, respectively. The correspondent 1-dB bandwidths of these TLTs are 175% and 140%. The chip areas of the TLTs are 0.27 mm² and 0.34 mm².