ARGOS Feed Design

The overarching objective for the ARGOS conceptual design study is to prepare fully for the subsequent rapid implementation of a leading-edge wide-field interferometer in Europe and ensure its optimal integration into the network of existing and future international astronomical facilities.

A custom feed design that can operate at 1-3 GHz has been designed to collect the signal from the reflectors at the required gain and beam levels, to collect as much energy as possible from the faint radio astronomy sources. That feed requires a high-end engineering as a hardware part, to avoid any losses in the efficiency of the RF-front-end, and therefore a breakthrough fabrication solution through 3D printing is described.

Due to the radio-telescope’s character that involves small diameter dishes, it was decided to avoid a custom design and fabrication for the dish reflector. Thus, the reflector should be purchased as product that is already in the market and satisfies ARGOS full scale telescope requirements, such as the operating frequency of 1-3 GHz, the 6-meter diameter and a cost-effective pricing in order to realize the low-cost requirement for the ARGOS radio-telescope, that can be easily scalable in the future. This task is described with an extended market survey about reflector antennas, with data from different products and companies. A 6-m reflector, requires also a durable mount, in order to point appropriately such a heavy-weight instrument at the radio sources in the sky, in outdoor environment and strong weather conditions (i.e. severe wind speeds).

Analysing the RF front-end of the telescope, the low noise amplifiers, and the filters should have a specific order in the signal path, and very specific gain levels to amplify the signal adequately and cut off the unwanted frequencies without importing additional noise to the system.

After several scenarios and investigations to create an optimal solution, a final solution has been provided from UPRC and MPIfR, to get the most out of the components. The final front-end RF chain, starts with the feed, which delivers two orthogonally separated polarizations. To avoid losses from cable lengths that could degrade the system performance, a low-noise amplifier is directly connected at each RF output port of the feed-horn. For calibration purposes, a Noise Source is included, which injects a reference signal into both RF downstream paths.

Then, two low-loss coaxial cables will carry the RF signal to an RFI shielded and weatherproofed housing that will be mounted at the back of the reflector. At this place, the housing cannot provide any additional blockage to the reflector, and will not struggle the mount, as it could done if more weight was applied at the feed point, far from the weight center. Inside the housing the RF signal processor, the RFSoC board, a time and reference generator and a power supply are hosted.

This collaborative effort provides a high-performance, low-loss front-end RF chain design that maximizes the capabilities of the chosen components. This design front-end RF chain lays the groundwork for exceptional signal reception and data acquisition for the ARGOS telescope antenna.