A passive total power radiometer in 0.25 µm SiGe BiCMOS for millimeter-wave imaging

In this paper we present a high sensitivity total power radiometer front-end integrated in a 0.25 μm SiGe BiCMOS technology. The radiometer consists of a two-stage LNA co-integrated with a common-emitter square-law detector. Together these stages provide a peak responsivity of 61 MV/W and a 6 GHz system bandwidth around 56 GHz. An optimized non-50-Ohm impedance interface between the LNA and the detector results in an improved system responsivity and sensitivity. Furthermore, the use of a large area load resistor in the detector results in a sub-300 Hz noise corner. Combining the peak responsivity with the 194 nV/√Hz noise floor at the output results in a minimum NEP of 3.2 fW/√Hz at 300 Hz.