A broadband, millimeter wave, asymmetrical Marchand balun in 180 nm SiGe BiCMOS technology

A silicon-compatible, broadband, millimeter wave Marchand balun operating at a center frequency of 65 GHz is presented. This balun is asymmetrical and broadside-coupled and exhibits excellent performance over a 30-90 GHz frequency range. The gain imbalance is -1.6 dB at 30 GHz, and +0.6 dB at 90 GHz, with a phase imbalance of ± 5.2 degrees, respectively. The balun exhibits good insertion loss and isolation over the frequency range of interest. To the authors´ knowledge, this is the widest bandwidth millimeter wave balun reported to date.