A millimeter-wave (mmW) frequency passive mixer for in-situ noise characterization in 110–170 GHz (D-band) is demonstrated using STMicroelectronics BiCMOS 55 nm technology. The circuit uses a gate-pumped MOS transistor with transmission lines filters, without any IF amplifier, allowing a direct noise characterization. This mixer is designed as a frequency down-converter, from D-band frequency to 1 GHz, enabling the noise power measure to fall within the baseband frequency of standard noise figure meter. In the 150 – 162 GHz band, the mixer exhibits conversion gain (CG) between −12.8 dB and −9.8 dB with a minimum noise figure (NF) of 10 dB for a 3.2 dBm LO power. The chip size is 1.1 × 0.4 mm2 including DC/RF pads.