The Coaxial L-P Cryogenic Receiver of the Sardinia Radio Telescope

Giuseppe Valente,Pietro Bolli,Giorgio Montisci,Alessandro Orfei,Renzo Nesti,Alessandro Cattani,Pasqualino Marongiu,Sergio Mariotti,Juri Roda,Alessandro Navarrini,Tonino Pisanu

doi:10.1109/access.2021.3139744

Abstract

The design and characterization of the coaxial dual-band L-P radio astronomical receiver for the prime focus of the Sardinia radio telescope are presented. The main feature of this receiver is to allow simultaneous radio astronomical observations in the P (305 – 410 MHz) and L (1.3 – 1.8 GHz) frequency bands. This functionality, which has been requested by the Pulsar research group at the National Institute for Astrophysics to estimate, among the others, the ionospheric dispersion in Pulsar observation, is currently missing in any other radio astronomical facility throughout the world. Also, single band operation is ensured by the proposed design both in linear and circular polarization, making this L-P receiver an ideal instrument for a wide range of radio astronomical and space applications. Some components of the receiver chain have been housed inside a cryostat and refrigerated at 20 K to reduce the noise temperature, resulting in a good performance compared to the receivers of other large radio telescopes. Several challenging issues have been faced in the design, mainly due to the large dimension and weight of the overall structure to be mounted in the prime focus position. Moreover, the design of the cryostat was constrained by the limited space available in the direction of the optical axis inside the focal cabin of the radio telescope, requiring a compact and light realization of the components of the receiver chain. This called for a home-made design of several devices, requiring a strong collaborative effort by researchers, engineers, and astronomers.

Highlights

The Sardinia Radio Telescope (SRT) is a general-purpose fully steerable 64-meter diameter radio telescope designed to operate with high efficiency across the 0.3-116 GHz frequency range [1,2,3,4]
For each passive component of the receiver chain, the equivalent noise temperature has been computed by wherein TREFi is the physical temperature of the component and NFi its noise figure
The estimated values of the system noise temperature of the receiver reported in Table VI and VII have been assessed by measurements, for both receivers (P-band and L-band) and both polarization channels (Horizontal and Vertical)

Summary

INTRODUCTION

The Sardinia Radio Telescope (SRT) is a general-purpose fully steerable 64-meter diameter radio telescope designed to operate with high efficiency across the 0.3-116 GHz frequency range [1,2,3,4]. Beam-wave guide foci (F3&F4 and F5&F6) with F/D 1.38 and 2.81, respectively, frequency range 1.4 GHz 35 GHz. In this work we will describe the development, design, and realization of the cryogenic coaxial dual-frequency L-P band receiver of the SRT, which has been installed on the primary focus (F1) of the antenna and allows concurrent observations in the P and L frequency bands, as well as observations in a single band (either P-band or L-band). In this work we will describe the development, design, and realization of the cryogenic coaxial dual-frequency L-P band receiver of the SRT, which has been installed on the primary focus (F1) of the antenna and allows concurrent observations in the P and L frequency bands, as well as observations in a single band (either P-band or L-band) This receiver operates in both linear and circular polarization, allowing observation of a wide range of radio astronomical phenomena. In the following subsections we will describe in detail the design and the architecture of the blocks a), b), and c) listed above

ARCHITECTURE OF THE COAXIAL FEED

L BAND RECEIVER CRYOGENIC RF PATH

THERMAL DESIGN OF THE CRYOSTAT

EVALUATION OF THE RECEIVER SYSTEM TEMPERATURE

COUPLING BETWEEN THE COAXIAL FEED AND THE SARDINIA RADIO TELESCOPE

CONCLUSION