Upgrading of the L-P Band Cryogenic Receiver of the Sardinia Radio Telescope: A Feasibility Study

Abstract

The Sardinia Radio Telescope is a quasi-Gregorian system with a shaped 64 m diameter primary reflector and a 7.9 m diameter secondary reflector. It was designed to operate with high efficiency across the 0.3–116 GHz frequency range. The telescope is equipped with a cryogenic coaxial dual-frequency L-P band receiver, which covers a portion of the P-band (305–410 MHz) and the L-band (1300–1800 MHz). Although this receiver has been used for years in its original design, with satisfactory results, it presents some parts that could be upgraded in order to improve the performances of the system. With the passing of time and with technology advances, the presence of unwanted human-made signals in the area around the telescope, known as radio frequency interferences, has grown exponentially. In addition, the technology of the receiver electronic control system became obsolete and it could be replaced with next-generation electronic boards, which offer better performances both service reliability and low generation of unwanted radio frequency signals. In this paper, a feasibility study for improving the L-P band receiver is discussed, taking into account the mitigation of the main radio frequency interferences. With this study, it is possible to have a sensitive instrument that can be used for scientific research at low frequencies (P- and L-bands), which are usually populated by signals from civil and military mobile communications, TV broadcasting and remote sensing applications.

Radio Frequency Interference Measurements to Determine the New Frequency Sub-Bands of the Coaxial L-P Cryogenic Receiver of the Sardinia Radio Telescope

“…Consequently, the monitoring and mitigation of RFI represents one of the most important aspects to consider for the optimal functioning of a radio telescope. With regards to the monitoring operations, dedicated measurement campaigns are periodically necessary [7][8][9].…”

“…Typically, the RFI survey can be performed using fixed stations, such as the telescope itself or a dedicated ad hoc system for RFI detection, and mobile laboratories [9]. Regarding the RFI mitigation, it can be carried out by interventions on the receiver hardware components or by developing dedicated software [8].…”

“…Regarding the RFI mitigation, it can be carried out by interventions on the receiver hardware components or by developing dedicated software [8]. In the first option, the design of the signal acquisition chain can be revised by adding microwave filters with a focus on rejecting the unwanted signals with the highest levels of amplitude, which can saturate the active components (i.e., the low noise amplifiers) of the receiving chain [9,10]. In the case of the development of dedicated software for RFI mitigation, several works are available in the literature [11][12][13].…”

“…9.245151 • E), at an altitude of about 650 m above sea level. The technical characteristics of the telescope and its radio receivers are described in detail in [9,[20][21][22][23]. One of its radio receivers is the cryogenic coaxial dual-frequency L-P band receiver, which is installed on the primary focus and covers the nominal bands of 305-410 MHz and 1300-1800 MHz simultaneously.…”

“…Although this receiver has been used for years with sufficient results in astronomy research, it presents some modules that could be improved in terms of performance and sensitivity. A detailed description of this receiver and a feasibility study of its upgrade are presented in [9].…”