Improved COST 231-WI Model for Irregular Built-Up Areas

The estimation of the field levels generated by radio base stations set in urban environment is still urgent need and a relevant issue for the compliance to national regulations and for propagation concerns. This work copes with the estimation of electromagnetic field generated by UHF base stations in peculiar urban scenarios. To account for irregular geometries and to deal with the propagation in hilly town, the COST 231-Walfisch-Ikegami model is modified and rephrased in order to evaluate the path loss at distances greater than 20 meters from the base station in such peculiar urban environments. Measurements were carried out in the small urban and irregular built-up areas of Dorgali (NU), Cala Gonone (NU) and Lunamatrona (CA), Italy, to validate the model

Advantages of using a C-band phased array feed as a receiver in the Sardinia radio telescope for space debris monitoring

The population of space debris is continuously growing and it represents a potential problem for satellites and spacecraft. In fact, new collisions could exponentially rise the number of debris and so the level of threat represented by these objects. To prevent new collisions, the monitoring of space environment is necessary. For this reason, radar measurements are relevant, in particular to observe Space Debris in Low Earth Orbit. In recent years, the Sardinia Radio Telescope, a fully steerable wheel-and-track 64-m antenna, located in Sardinia (Italy), has been used as a receiver in a Pband bi-static radar for space debris monitoring purposes. In this paper the authors investigate the advantages of using a Phased Array Feed in C-band for space debris monitoring (e.g. improved sensitivity and gain, detection of the object trajectory allowed by multiple beams, improvement of the orbit determination of known and unknown debris), as a receiver of the Sardinia Radio Telescope compared to the already used mono-beam P-band receiver

Adaptation of an IRAM W-Band SIS Receiver to the INAF Sardinia Radio Telescope: A Feasibility Study and Preliminary Tests

Radio telescopes are used by astronomers to observe the naturally occurring radio waves generated by planets, interstellar molecular clouds, galaxies, and other cosmic objects. These telescopes are equipped with radio receivers that cover a portion of the radio frequency (RF) and millimetre-wave spectra. The Sardinia Radio Telescope (SRT) is an Italian instrument designed to operate between 300 MHz and 116 GHz. Currently, the SRT maximum observational frequency is 26.5 GHz. A feasibility study and preliminary tests were performed with the goal of equipping the SRT with a W-band (84–116 GHz) mono-feed radio receiver, whose results are presented in this paper. In particular, we describe the adaptation to the SRT of an 84–116 GHz cryogenic receiver developed by the Institute de Radio Astronomie Millimétrique (IRAM) for the Plateau de Bure Interferometer (PdBI) antennas. The receiver was upgraded by INAF with a new electronic control system for the remote control from the SRT control room, with a new local oscillator (LO), and with a new refrigeration system. Our feasibility study includes the design of new receiver optics. The single side band (SSB) receiver noise temperature measured in the laboratory, Trec ≈ 66 K at 86 GHz, is considered sufficiently low to carry out the characterisation of the SRT active surface and metrology system in the 3 mm band

Preliminary Characterization of the Digitally Formed Beams of PHAROS2 Phased Array Feed

We describe the beamforming strategy and the preliminary laboratory characterization results of the beam pattern synthesized by the PHAROS2 Phased Array Feed (PAF), a 4-8 GHz PAF with digital beamformer for radio astronomy application. The PAF is based on an array of 10×11 dual-polarization Vivaldi antennas cryogenically cooled at 20 K along with low noise amplification modules (LNAs) cascaded with a multi-channel Warm Section (WS) receiver. We present the beamforming and test procedures used to, respectively digitally synthesize and characterize the PHAROS2 antenna array beam pattern at 6 GHz. The tests of the array were carried out at room temperature by directly connecting 24 antenna elements to the WS and iTPM digital beamformer in a laboratory measurement setup

Status of the multibeam S band receiver for the Sardinia Radio Telescope

We describe the development status of the S-band (3-4.5 GHz) seven-beam cryogenic receiver for the primary focus of the Sardinia Radio Telescope (SRT). The main scientific goals for the SRT at S-band include the search for new pulsars, the evaluation of the pulsar dispersion for gravitational wave measurements, the mapping of galactic supernova remnants, and the study of magnetic field of galaxy clusters

Status of a C-band Phased Array Feed with RFSoC digital beamformer

In this paper, we describe the design and development status of a room-temperature C-band Phased Array Feed (PAF) demonstrator, based on Radio Frequency System-on-Chip (RFSoC) for radio astronomy application, to be installed on the Sardinia Radio Telescope. The instrument is optimized to work across the 4.75-6.00 GHz radio frequency (RF) band. The project of the front-end includes a compact RF module based on an 8×8 array of linear dual-polarization antenna elements integrated with Monolithic Microwave Integrated Circuit (MMIC) Low Noise Amplifiers (LNAs). In the preliminary version of the front-end project, which considers only one linear polarization, a subset of 32 elements are connected to the LNAs, while the rest of them are terminated to 50 Ohm matched loads. A dedicated signal acquisition chain of microwave components, based on two stages of filtering and signal conditioning, permits the injection of the 32 RF signals to the two commercial back-ends based on RFSoC digital boards. Each board is equipped with 16 inputs, with 1.25 GHz instantaneous bandwidth, and performs the frequency channelization, the partial and final beamforming of at least four independent beams (the number of beams may vary depending on the observation requirements). A general description of the front-end design, the back-end hardware, firmware and software development and an optimizer for the whole system performances evaluation, is presented

Architecture of C-band Phased Array Feed with RFSoC digital beamformer

We describe the architecture of a room-temperature C-band Phased Array Feed (PAF) demonstrator based on Radio Frequency System-on-Chip (RFSoC) for radio astronomy application. The instrument operates across the 4.75-6.00 GHz RF band (C-band). The RF section includes a compact module based on an 8×8 array of dual-polarization antennas integrated with MMIC (Monolithic Microwave Integrated Circuit) Low Noise Amplifiers (LNAs). A subset of 32 elements of one of the two polarization channels of the 128 antennas are connected to the LNAs, while the rest are terminated into internal loads. Following two stages of filtering and signal conditioning, the 32 RF signals are injected in two commercial RFSoC digital boards, each accepting 16 inputs with 1.25 GHz bandwidth, that will perform the frequency channelization, the partial and final beamforming of four independent beams with 1.25 GHz instantaneous bandwidth

Status of the High-Frequency Upgrade of the Sardinia Radio Telescope

The Sardinia Radio Telescope is going through a major upgrade aimed at observing the universe at up to 116 GHz. A budget of 18.700.000 E has been awarded to the Italian National Institute of Astrophysics to acquire new state-of-the-art receivers, back-end, and high-performance computing, to develop a sophisticated metrology system and to upgrade the infrastructure and laboratories. This contribution draws the status of the whole project at eight months from the end of the funding scheme planned for August 2022

The high-frequency upgrade of the Sardinia Radio Telescope

We present the status of the Sardinia Radio Telescope (SRT) and its forthcoming update planned in the next few years. The post-process scenario of the upgraded infrastructure will allow the national and international scientific community to use the SRT for the study of the Universe at high radio frequencies (up to 116 GHz), both in single dish and in interferometric mode. A telescope like SRT, operating at high frequencies, represents a unique resource for the scientific community. The telescope will be ideal for mapping quickly and with relatively high angular resolution extended radio emissions characterized by low surface brightness. It will also be essential for spectroscopic and polarimetric studies of both Galactic and extragalactic radio sources. With the use of the interferometric technique, SRT and the other Italian antennas (Medicina and Noto) will operate within the national and international radiotelescope network, allowing astronomers to obtain images of radio sources at very high angular resolution

Solar Observations with Single-Dish INAF Radio Telescopes: Continuum Imaging in the 18 - 26 GHz Range

We present a new solar radio imaging system implemented through the upgrade of the large single-dish telescopes of the Italian National Institute for Astrophysics (INAF), not originally conceived for solar observations