Miniaturized 40–60 GHz On-Chip Balun With Capacitive Loading Compensation

A millimeter-wave balun by using the broadside-coupled transmission lines and capacitive loading compensation is proposed and investigated. The balun is designed and verified by using a commercial SiGe BiCMOS technology. The measured results show that in the frequency range of 40-60 GHz, the amplitude mismatching and absolute phase error are less than 0.2 dB and 2.7°, respectively. The compact size of the balun is only 200 μm × 180 μm including grounding shield.