Cryogenic L-band GaAs HEMT LNA for the Square Kilometer Array

Abstract

Cryogenic low noise amplifiers (LNAs) are in high demand for highly sensitive receivers for radio astronomy. This paper describes the design and testing of an extremely low noise amplifier based on 3-stage GaAs HEMTs and a microwave integrated circuit. Utilizing computer-aided design techniques, lumped passive components were adapted to integrate with GaAs low noise transistors to optimize the noise and return losses. This LNA design achieved an extremely low noise temperature of averaging only 1.3 K, having $>40$ dB gain, and low input and output return losses $< -10$ dB, in a wide bandwidth from 900 MHz to 2000 MHz at a physical temperature of 15 K. It realized high gain and an excellent gain stability of Allan variance $< 2 \mathrm {x}10~^{\mathbf {-8}}$ at cryogenic temperatures and meets the stringent requirements of the Square Kilometer Array receivers.