Ultra Low Noise Amplifiers for Future Radio Astronomy Observatories

UoM administered thesis: Phd

  • Authors:
  • Daniel White


In recent years, two distinct engineering challenges have been identified for Low Noise Amplifiers (LNAs) utilised in radio astronomy front-end receivers. There has been a sharp increase in the number of receiving elements being used in observatories, and an increased desire to utilise LNAs further into the millimeter/submillimeter region. These challenges have been met by using sophisticated High Electron Mobility Transistors (HEMTs) based on Indium Phosphide (InP) and Gallium Arsenide (GaAs) technologies. Advances in HEMT technology have resulted in amplifiers operating further towards the THz region, extending the high frequency performance of HEMT based LNAs. However, there are applications that prohibit the use of these technologies. Radio observatories consisting of vast quantities of receiving elements introduce the need for a high performance, low noise technology using a cost-effective commercial solution. This thesis describes the development of MMIC LNAs suitable for use in modern radio astronomy observatories. A commercially available 100 nm GaAs pHEMT process has been used to develop LNAs for the projected high frequency upgrades to the Square Kilometer Array (SKA). Two MMICs operating over the bandwidth of 13.6 - 24 GHz achieve simulated noise figures of 1 and 1.2 dB with forward transmission (S21) in excess of 24 dB. These MMICs show promising results with the capacity to be fabricated and deployed in vast quantities. At room temperature, a fully assembled LNA exhibits gain in excess of 21.5 dB with noise figure between 1.77 - 2.60 dB. When cryogenically cooled to 20 K physical temperature, the LNA exhibits gain in excess of 19.7 dB and noise figure between 0.80 - 2.05 dB. Two state-of-the-art low noise performance technologies have been used to develop MMICs operating across the frequency range of 125 - 211 GHz. Two cryogenic MMICs have been designed using a 35 nm InP HEMT process, achieving simulated noise temperatures between 4 --- 6 times the quantum limit with S21 in excess of 16 dB. An experimental 25 nm InP HEMT process has been used to develop a MMIC with simulated room temperature noise figure of 3 dB, and S21 in excess of 30 dB. This will be the first demonstration of a MMIC LNA developed using this process. These MMICs will contribute to a project exploring the possibility of combining bands 4 and 5 of the Atacama Large Millimeter/submillimeter Array (ALMA) into a single, ultra wideband HEMT LNA receiver.


Original languageEnglish
Awarding Institution
Award date1 Aug 2020