An Ultra-wide Bandwidth Low-frequency Radio Astronomical Cryogenic Receiver for FAST Telescope

This paper presents an ultra-wide bandwidth(UWB)low-frequency radio astronomical cryogenic receiver for the Five-hundred-meter Aperture Spherical radio Telescope(FAST).It covers 6.6:1 bandwidth from 0.5 to 3.3 GHz.The receiver consists of a Quad-Ridged Flared Horn(QRFH),a cryogenic microwave unit,an optical transceiver and a warm microwave and frequency mixing unit.A QRFH with a concentric-loaded dielectric spear is developed:the average return losses are larger than 20 d B;the average ports polarization isolation is 43.87 d B;the average dish efficiency is higher than 65%.Many UWB cryogenic low loss components are developed for the fabrication of a cryogenic microwave unit.The average noise temperature lower than 14.2 K and 22.5 K are achieved as referred to the input ports of cryogenic Dewar and the output of horn,respectively.Compared to other similar advanced UWB receivers,such as Parkes 0.7-4.2 GHz(6:1 bandwidth)receiver and FAST 0.27-1.62 GHz(6:1 bandwidth)receiver,wider relative bandwidth of the proposed receiver is achieved and it is a new attempt to expand the bandwidth of UWB low-frequency receiver.