A high isolation CMOS switch for loopback built-in self-test in a millimeter-wave transceiver

The seamless integration of CMOS transceivers in digital CMOS processes enhances on-chip testability, thus reducing manufacturing cost. Built-in-self-test (BIST) using loopback is a cost-effective method for testing a transceiver. A high-isolation single-pole single-throw (SPST) switch is designed and fabricated in a 45nm CMOS process to create the loopback path. The measured isolation is better than 30 dB in the 70-87 GHz range with maximum isolation of 42 dB. This is the highest reported isolation in a CMOS switch at this frequency. The insertion loss is 12 dB at 80 GHz, which is sufficiently low for the loopback operation.