News: Microelectronics
29 December 2025
Fraunhofer IAF and Max Planck Institute for Radio Astronomy provide low-noise amplifiers for ALMA radio telescope array
As one of the world’s most powerful radio telescope facilities, the Atacama Large Millimeter/Submillimeter Array (ALMA) at 5000m above sea level on the Chajnantor Plateau in the Chilean Andes observes dark and distant regions of the universe by measuring the millimeter and submillimeter radiation emitted by cold molecular clouds (interstellar gas clouds with a temperature of only a few tens of Kelvin, in which stars form when the density and temperature are right) in order to better understand how stars, planets, galaxies and life are formed.
ALMA has a total of 66 individual parabolic antennas with diameters of 12m or 7m, each equipped with high-frequency receivers for ten wavelength ranges (ALMA bands) between 6mm and 8.6mm (35–50GHz) and 0.3mm and 0.4mm (787–950GHz) in the electromagnetic spectrum. For Band 2, which covers wavelengths from 2.6mm to 4.5mm (67–116GHz), Germany’s Fraunhofer Institute for Applied Solid State Physics IAF in Freiburg and the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn have now provided 145 low-noise amplifiers (LNAs). So, all ALMA bands are now fully equipped for the first time.
Picture: ALMA Band 2 high-frequency receiver (© NOVA/ESO).
With ALMA’s Band 2, researchers hope to gain a better understanding of the cold interstellar medium (a mixture of dust, gas, radiation and magnetic fields from which stars are formed). Complex organic molecules in nearby galaxies, which are considered precursors to biological building blocks, as well as planet-forming disks, will also be studied in greater detail thanks to the improved measurement capabilities.
Unique average noise temperature of 22K enables highly sensitive measurements in Band 2 of the ALMA telescopes
“The performance of receivers depends largely on the performance of the first high-frequency amplifiers installed in them,” says Dr Fabian Thome, head of the subproject at Fraunhofer IAF. “Our technology is characterized by an average noise temperature of 22K, which is unmatched worldwide.” With the new LNAs, signals can be amplified more than 300-fold in the first step. “This enables the ALMA receivers to measure millimeter and submillimeter radiation from the depths of the universe much more precisely and obtain better data,” he adds. “We are incredibly proud that our LNA technology is helping us to better understand the origins of stars and entire galaxies.”
Development, production and qualification of InGaAs mHEMT LNAs for ALMA
At the heart of the LNAs for ALMA’s Band 2 are monolithic microwave integrated circuits (MMICs) based on indium gallium arsenide (InGaAs) metamorphic high-electron-mobility transistors (mHEMTs) developed by Fraunhofer IAF. The technology enables LNAs with particularly low noise temperatures, which significantly increases the sensitivity of the receivers. Low-noise amplifiers improve the quality of incoming signals by amplifying the signal while causing as little disruptive background noise as possible.
Fraunhofer IAF and MPIfR were jointly commissioned by the European Southern Observatory (ESO), which operates ALMA in cooperation with other international institutions. Fraunhofer IAF was responsible for the specific design of the MMICs, their manufacturing, their testing at room temperature and the selection of the chips. MPIfR took over the modules’ complex assembly and qualification, including cryogenic test measurements at 15K for use in the ALMA Band 2 receivers matching ESO specifications.
Location and operation of ALMA
ALMA is jointly operated by ESO, the US National Science Foundation (NSF) and the Japanese National Institutes of Natural Sciences (NINS) in cooperation with the Republic of Chile. ALMA is supported by ESO on behalf of its member countries (Belgium, Denmark, Germany, Finland, France, Great Britain, Ireland, Italy, the Netherlands, Austria, Poland, Portugal, Spain, Sweden, Switzerland, the Czech Republic, and the host country Chile), by the NSF in collaboration with the Canadian National Research Council (NRC), the Taiwanese National Science Council (NSC) and NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
Fraunhofer IAF low-noise amplifiers used aboard ESA’s Arctic Weather Satellite
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