Abstract
This paper describes the design and measured performance of the band 2 (L-band, 950 MHz–1760 MHz) cryogenic receiver front-end of the Square Kilometre Array (SKA) radio telescope dish array. The system comprises a wide flare-angle axially corrugated conical horn, a dual linearly polarized orthogonal mode transduce, a noise injection directional coupler, and two amplification stages. Its compact design and cryogenic cooling allow for a very low receiver noise temperature, and it presents another step in the continuous improvement of the noise temperature performance. A Gifford–McMahon cooler physically cools the OMT with its integrated directional coupler to around 70 K, and the first stage low-noise amplifier to about 15 K. A bespoke measurement setup was designed to measure the system’s performance. The measured receiver noise is about 6 K across the frequency band.
Highlights
Receiving sensitivity, arguably the most important metric for astronomical radio telescopes, is defined as the ratio of effective aperture area to system noise temperature (Ae∕Tsys)
We describe the design of the critical components in the Square Kilometer Array (SKA) L-band receiver front-end’s signal chain, as well as its measured performance using a bespoke measurement setup
6.2 Measurement Results A prototype receiver front-end was measured in a laboratory, in an radio frequency interference (RFI) shielded tent with a shielding effectiveness of 80 dB
Summary
Arguably the most important metric for astronomical radio telescopes, is defined as the ratio of effective aperture area to system noise temperature (Ae∕Tsys). Over this frequency range, the antenna temperature is about 8 K to 6 K (lowest to highest frequency) with the reflector system’s main beam pointing to zenith, and increases by about 1 K while tipping to 60 deg from zenith. We describe the design of the critical components in the SKA L-band receiver front-end’s signal chain (shown in Fig. 1), as well as its measured performance using a bespoke measurement setup. This system has a measured receiver temperature below 6.5 K and an expected system temperature of below 14 K when mounted on the SKA reflector system and pointing to zenith.
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