A Wideband Low Noise Flat Gain Amplifier for Interferometric Passive Microwave Imaging System

This paper proposes a two-stage broadband low noise amplifier for interferometric passive microwave imaging system using 0.15-μm GaAs pseudomorphic high electron mobility transistor (pHEMT) process. The first stage is designed for wideband input and noise matching using source degeneration. Frequency-controlled feedback amplifier is employed in the second stage to obtain flat gain across the bandwidth. Measurement results show that gain of the amplifier is larger than 18 dB from 3.6-9.4 GHz, and the gain flatness within 4-8 GHz is under ±0.6 dB. A minimum noise figure of 1.5 dB is obtained with input and output return loss both above 10 dB. The dimension of the chip is 1.5 × 0.8 m
²
.