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First state-of-the-art cryogenic low-noise amplifiers arrive for SKA-Mid
from Contact 17
Above: NRC Herzberg Astronomy and Astrophysics Research Centre staff Dr Frank Jiang, Dominic Garcia and Dr Deisy Formiga Mamedes testing LNAs for SKA-Mid.
BY NRC HERZBERG ASTRONOMY AND ASTROPHYSICS RESEARCH CENTRE
Astronomical signals received by the SKA antennas are extremely faint, meaning they must be highly amplified while limiting the amount of unwanted noise introduced by the system itself. The SKAO requires state-of-the-art low-noise amplifiers (LNAs) to perform this critical function.
The National Research Council of Canada (NRC) is Canada’s representative in the SKAO. One part of its contribution to the project is supplying hundreds of cryogenic LNAs that will be integrated into the SKA-Mid array Band 2 receivers, with two LNAs fitted in each receiver.
“Our LNAs are known for their exceptional performance,” says Adam Densmore, Team Leader of the Radio Instrumentation Team at the NRC’s Herzberg Astronomy and Astrophysics Research Centre.
“We have demonstrated some of the lowest-noise amplifiers reported and we are constantly refining our designs and processes to meet the future demands of radio astronomy.”
For the frequency range covered by Band 2, the sensitive radio receiver equipment must be kept exceptionally cold, as heat generated by electronics and from the environment adds “thermal noise” to the astronomical signals, drowning them out. The LNAs are housed inside the Band 2 receiver, which is cooled by a compressed helium system supplied by the UK’s Oxford Cryosystems and South Africa’s EMSS.
“In Band 2, each SKA-Mid dish must be able to pick up extremely faint signals that are over a million times weaker than what a typical mobile phone tower transmits,” says Jayashree Roy, SKAO Signal Processing Engineer. “To achieve this, the dish system must keep its own noise as low as possible. A high-quality low-noise amplifier is crucial; without it, distant astronomical signals would be obscured in the background noise, making it difficult to extract any meaningful information,” she adds.
An astronomical challenge
“The biggest challenge was to achieve ultra-low noise. The LNAs add less than 2 kelvin of noise across the entire operating band, which is a record low while maintaining high gain stability. This is critical for correct calibration of astronomical observations at cryogenic temperatures,” explains Frank Jiang, a Senior Research Officer at the NRC who led the development of the LNAs.
The semiconductor chips in the NRC’s LNAs are cryogenically cooled to just 15 kelvin (-258°C), which allows them to achieve the high gain and lowest noise performance. However, the extreme cold introduces other challenges.
“We try to use commercial components as much as possible, but they must be carefully chosen to ensure that they can withstand the extremely low operating temperature,” explains Jiang. “We rigorously qualify each component in our cryogenic chamber before implementing them into our LNA designs.”
Additionally, to ensure that the LNAs can be manufactured in high volumes while still meeting the performance and quality standards required, the team needed a design that was as tolerant as possible to the inherent fluctuations in the component characteristics at extremely low temperatures.
A combination of exceptional expertise and ultraspecialised facilities had the NRC well positioned to tackle the challenge of meeting the requirements of the LNAs for the SKA-Mid Band 2 receivers.
The NRC delivered the first batch of its LNAs to SKA-Mid in November 2024. To meet the SKAO’s schedule, the team built the first 20 LNAs in-house at the Dominion Astrophysical Observatory in Victoria, Canada, and outsourced the remainder to Ontario-based Nanowave Technologies Inc. (Nanowave), which has already completed production of more than 60 additional LNAs passing all requirements.
Nanowave designs and manufactures radio frequency components and subsystems for the space, aerospace and defence industries and has a proven track record of delivering cryogenic LNAs for radio astronomy.
Working together since 1997, the NRC and Nanowave produced the cryogenic LNAs for the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, as well as for the SKA precursor MeerKAT radio telescope in South Africa. Working on these projects with the NRC helped Nanowave develop the expertise to successfully expand into new markets.
“Our collaboration is an excellent example of how NRC-developed technology enables Canadian companies to compete in markets where technological innovation and manufacturing expertise result in internationally competitive advantages,” says Nanowave CEO Justin Miller.
LNAs are essential components for both the SKA-Mid and SKA-Low telescopes. Alongside those being produced for SKAMid in South Africa by the NRC for the Band 2 receiver, Sweden’s Low Noise Factory is producing LNAs for the Band 1 receiver. For SKA-Low, the UK company Kasdon Electronics (under subcontract from Italy’s Sirio Antenne) is providing the LNAs which will enable the very faintest low-frequency signals to be amplified.
