A compact, transformer-based 60 GHz SPDT RF switch utilizing diode-connected SiGe HBTs

This work describes the design of a compact 60 GHz SPDT RF switch utilizing diode-connected SiGe HBTs. At mm-wave frequencies, SiGe HBTs demonstrate better Roff/Ron ratios than CMOS and can be used to improve switch performance. A switch topology using a transformer is developed to create a SPDT with a small foot print of 190 μm × 225 μm. The transformer design is discussed and a methodology is presented to optimize the matching components of the switch. The switch is fabricated on a 180 nm SiGe BiCMOS technology platform featuring HBTs with an fT/fmax of 240/260 GHz. The switch achieves 2.7 dB insertion loss and 14 dB isolation at 60 GHz with a P1dB and IIP3 of 13.8 dBm and 23.8 dBm, respectively. This represents a 20% improvement in insertion loss in comparison to a similar 90 nm CMOS switch at 50 GHz. It is also shown that the proposed switch can help enable built-in-self-test (BIST) functionality for transmit-receive modules.