A GaAs LNA MMIC for a Correlation-Dicke Radiometer Internal-Body Temperature Sensor

A 3-stage low noise amplifier (LNA) of a correlation-Dicke radiometer for internal body thermometry at 1.4 GHz is presented. The MMIC LNA is designed using enhancement-mode 0.1um GaAs pseudomorphic high electron mobility transistor (pHEMT) technology. High gain and low noise figure (NF) is achieved with a 3-stage common-source structure with inductive degeneration. Interstage passive high-pass and low-pass filters improve the stability with minimal degradation of the NF. Two LNAs are placed side-by-side in a single 3mm × 3mm die for integration into a correlation radiometer circuit. The LNA is characterized and shows 45.2 dB of stable gain, and a 1.04 dB NF at 1.4 GHz, chosen as a quiet band suitable for biomedical sensing.