A Total-Power Radiometer Front End in a 0.25- μm  BiCMOS Technology With Low 1/f  -Corner

This paper describes the analysis, design, and characterization of a high-sensitivity millimeter-wave total-power radiometer front-end integrated into a 0.25-μm SiGe:C BiCMOS technology. This prototype is composed of a two cascode stage low-noise amplifier (LNA) and a voltage-driven common-emitter square-law detector. The LNA is interfaced to the detector through a low transformation ratio (i.e., high-impedance node) to achieve an efficient wideband signal transfer. The front end achieves both a low 1/f -noise corner and a low noise-equivalent power (NEP) by combining a large area, high resistive value load resistor together with a minimum size heterojunction bipolar transistor. At 56 GHz and optimum bias, the prototype provides a 61-MV/W responsivity which combined with a 194-nV/√Hz white noise level result in a 3.2-fW/√Hz NEP when the input power is modulated with a frequency above the 30-Hz flicker noise corner. The achieved 3-dB NEP bandwidth is 6 GHz.