MILLIMETRE-WAVE LOW NOISE AMPLIFIERS FOR THE ALMA TELESCOPE

UoM administered thesis: Phd

  • Authors:
  • David Cuadrado Calle

Abstract

The Atacama Large Millimetre/submillimetre Array (ALMA) is a recently completed interferometric telescope located in the Atacama desert of Chile, at an elevation of 5000 m. It consists of 66 antennas which are furnished with highly-advanced cryogenic front-end receivers in ten frequency bands, ranging from 31 GHz to 950 GHz. These receivers are far superior to any other existing system, and are allowing the scientic community to perform observations in the millimetre and submillimetre ranges with unprecedented sensitivity. ALMA utilises Low Noise Ampliers (LNAs) as core receiver technology from 31 GHz to 90 GHz, and Superconductor-Insulator-Superconductor (SIS) mixers from 84 GHz to the telescope's upper observation limit at 950 GHz. However, recent advancements in transistor technology, such as the 35 nm Indium Phosphide (InP) HEMT, allow for the development of LNAs with exceptional performance properties that challenge the hegemony of SIS mixers as leading detectors, at frequencies as high as 116 GHz and beyond. This allows ALMA bands 2 (67-90 GHz) and 3 (84-116 GHz) to be combined into a single ultra-broadband LNA-based instrument of great interest for future radio astronomy. This thesis describes the design, fabrication, assembly and characterisation of the first LNAs suitable for operation in the combined ALMA band 2+3 (67-116 GHz) range. The best LNAs presented here show a noise temperature less than 250 K from 72 GHz to 104 GHz at room temperature, and less than 28 K from 70 GHz to 110 GHz at cryogenic ambient temperature of 20 K. This is believed to be the lowest broadband noise temperature ever reported in the literature in the 70-110 GHz frequency range, typically designated as W-band. Moreover, the LNAs presented in this work are also suitable for future radio telescopes with broadband receivers in the W-band frequency range, such as the ngVLA or LLAMA, and non-astronomical applications such as automotive radars or millimetre wave imagers.

Details

Original languageEnglish
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Award date31 Dec 2017