Optimising the Performance of Wideband Low Noise Amplifiers for Radio Astronomy Applications

Abstract

State-of-the-art front-end receivers for radio astronomy require low noise receiver elements in order to provide the sensitivity needed to observe weak celestial signals. These faint signals are collected by a feed horn and amplified by Low Noise Amplifiers (LNAs) or Superconductor-Insulator-Superconductor (SIS) mixers at the front of the receiver. Until recent years, SIS mixers have dominated as the leading detector choice for low noise at high frequencies. Advancements in transistor technologies have allowed for the development of LNAs able to challenge the performance of SIS mixers for radio astronomy use at 100GHz and beyond. This thesis describes the design of a K-band (18-27 GHz) LNA using a commercially available GaAs pHEMT process from WIN semiconductors for operation in the e-MERLIN receiver system. The LNA presented shows a simulated room temperature (290K) noise performance of 101K across the band with an estimated cryogenic noise temperature of 14K and 29dB of gain. It also presents the design of two high frequency waveguide to microstrip transitions for use with MMIC LNAs for proposed wideband upgrades to the ALMA band 4 and 5 (125-211 GHz) and band 6 and 7 (211-373GHz) receivers. These transitions have a low simulated return loss, below 0.3dB and 0.75dB and insertion loss better than -9dB and -14dB respectively. The designs presented in this thesis have comparable performance to current state-of-the-art designs in the literature and provide excellent solutions for radio astronomy applications.

Date of Award	31 Jan 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Gary Fuller (Supervisor) & Danielle George (Supervisor)