Ultra-Low Noise L-Band Cryogenic Astronomical Receiver for FAST Telescope

TL;DR

This paper introduces an ultra-low noise cryogenic L-band receiver for the FAST telescope, achieving exceptional sensitivity and system noise temperature below 9 K through innovative design and integration of key microwave components.

Contribution

The paper presents a novel cryogenic Coupling-LNA with integrated coupling functions and low noise, optimized for the FAST telescope's L-band receiver, with improved performance over existing designs.

Findings

System noise temperature below 9 K

Cryogenic environment maintained at 15 K and 55 K

Antenna efficiency above 75%

Abstract

This paper presents an ultra-low noise L-band radio astronomical cryogenic receiver for FAST telescope. The development of key low noise microwave parts of Coupling-LNA and conical quad-ridge OMT and reasonable system integration achieve outstanding performance of receiver.It covers the frequency range of 1.2 GHz to 1.8 GHz. Novel cryogenic Coupling-LNAs with low noise, large return loss, high dynamic range and the function of coupling calibration signals are developed for the proposed receiver.Amplification and coupling function circuits are integrated as a single Coupling-LNA with full noise temperature of 4 K at the physical temperature of 15 K. And its return loss is more than 18 dB, and output 1 dB compression power is +5 dBm. A cryogenic dewar is fabricated to provide 55 K and 15 K cryogenic environment for OMT and Coupling-LNAs, respectively. The receiver's system noise temperature is below 9 K referred to feed aperture plane. Benefiting from optimal design and precise mechanical treatment, good scattering performance of OMT and equalized radiation patterns of horn are achieved with an antenna efficiency above 75%.