A 220–330 GHz Wideband, Low-Loss and Small Marchand Balun with Ground Shields in SiGe BiCMOS Technology

Nowadays, the realization of ultra-high-speed wireless communications using 300-GHz band is expected. Baluns are important components for 300-GHz-band circuits, and they are required to have wide bandwidth, low loss and small size. Passive baluns such as a rat-race balun and Marchand balun have good performance, and the Marchand balun can be smaller than a rat-race balun because the Marchand balun uses coupling lines. However, the size of the Marchand balun is determined by the ground shields in the terahertz band, and the optimum structure has not been clarified. In this work, we realize small Marchand balun with wide bandwidth and low loss by revealing the optimum distance between the signal lines and the ground shields. The proposed Marchand balun is fabricated using a 0.13 μm SiGe BiCMOS process. The proposed Marchand balun has a center frequency of 275 GHz, a bandwidth of 110 GHz, an insertion loss of 1.4 dB and an area of 0.008 mm2. It is shown that the proposed Marchand balun has the lowest loss and the smallest area compared to conventional millimeter-wave and 300-GHz-band baluns.