Feasibility Study of a W-Band Multibeam Heterodyne Receiver for the Gregorian Focus of the Sardinia Radio Telescope

Abstract

We report on the feasibility study of a W-band multibeam heterodyne receiver for the Sardinia Radio Telescope (SRT), a general purpose fully steerable 64-m diameter antenna located on the Sardinia island, Italy, managed by INAF ("Istituto Nazionale di Astrofisica," Italy). The W-band front-end is placed at the telescope Gregorian focal plane and will detect radio astronomy molecular spectral lines and broadband emission in the 3 mm atmospheric window. The goal specification of the receiver is a 4×4 focal plane array operating in dual-linear polarization with a front-end consisting of feed-horns placed in cascade with waveguide Orthomode Transducers (OMTs) and LNAs (Low Noise Amplifiers) cryogenically cooled at ≈20 K. The instantaneous FoV (Field of View) of the telescope is limited by the shaping of the 64-m primary and 7.9-m secondary mirrors. The cryogenic modules are designed to fit in the usable area of the focal plane and provide high-quality beam patterns with high antenna efficiency across the 70-116 GHz Radio Frequency (RF) band. The FoV covered by the 4×4 array is 2.15×2.15 arcmin 2 , unfilled, with separation between contiguous elements of 43 arcsec. Dual-sideband separation (2SB) down-conversion mixers are placed at the cryostat output and arranged in four four-pixel down-conversion modules with 4-12 GHz Intermediate Frequency (IF) bands (both Upper Side Band and Lower Side Band selectable for any pixel and polarization). The receiver utilizes a mechanical derotator to track the parallactic angle.

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

“…Recently, with the focus to maximize the scientific research results and extend them to high frequencies (up to 116 GHz) not yet covered by SRT, INAF has expressed an interest in upgrading its telescope. For these reasons, an Italian National Operational Program (PON) funding [35] has been allocated to INAF by the Italian Ministry of University and Research, with the aim to install four new receivers on the telescope at high frequencies, such as the Q-band (33-50 GHz) and W-band (70-116 GHz) [35,36]. The works relating to the PON project imposed the temporary dismantling of the old receivers, including the coaxial L-P cryogenic receiver, and a consequent stop on the SRT scientific observations.…”

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

“…In the new receivers developed for the PON project [25][26][27], a new electronic board, named Gain Attenuation Intelligent Amplifier (GAIA), is used for the remote control [26]. This board can be considered for the receiver upgrade feasibility study, in order to align the L-P band receiver technology with the PON new receivers.…”

“…This board can be considered for the receiver upgrade feasibility study, in order to align the L-P band receiver technology with the PON new receivers. The board is based on a microcontroller (model ATMega2560 from Microchip Atmel [50,51]) and on digital potentiometers (model AD5231 from Analog Devices [52]) designed for biasing, remote monitoring and control of the gate and the drain voltages (V g and V d , respectively) of cryogenic LNAs [26]. The GAIA board [26,53] offers ultra-stable biasing of the P-and L-band cryogenic LNAs.…”

“…The board is based on a microcontroller (model ATMega2560 from Microchip Atmel [50,51]) and on digital potentiometers (model AD5231 from Analog Devices [52]) designed for biasing, remote monitoring and control of the gate and the drain voltages (V g and V d , respectively) of cryogenic LNAs [26]. The GAIA board [26,53] offers ultra-stable biasing of the P-and L-band cryogenic LNAs. GAIA is equipped with a network module based on chip model W5100 from Wiznet [54] for the Ethernet communication.…”

“…With the aim of maximizing the scientific research results and extending them to new high frequencies (up to 116 GHz) not yet covered by SRT, INAF has recently expressed an interest to upgrade the telescope. For these reasons, a National Operational Program (PON) funding [25] has been allocated to INAF by the Italian Ministry of University and Research, with the aim to install on the telescope four new receivers that operate in Q-band (33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50) and W-band (70-116 GHz) [25][26][27]. The works relating to the PON project have imposed a stop on the SRT operations and, consequently, the temporary dismantling of the old receivers (P-band, L-band, C-band and K-band [9], respectively).…”