Medicina Radio Astronomical Station

IRA - Institute of Radio Astronomy

INAF - National Institute for Astrophysics

Backend Design

The Electronics lab hosted the development of a new concept of "routing, conditioning and detecting" system for the RF signals called FS-TP (Focus Selector – Total Power Back-End).

In the beginning, it was designed to be installed in the Sardinia Radio Telescope BWG (Beam Wave Guide) Room in order to perform "only" the focus selection. Then, the FS-TP was equipped with both a Total Power square-law detector and analog-to-digital conversion to send the collected data (via ethernet) to the antenna control room.

The back-end input bandwidth is 2 GHz (100-2100 MHz). A filtering system allows the selection of sub-bands of different width: 0.1-0.35 GHz, 0.1-0.83 GHz, 0.1-1.3 GHz and 0.1-2.1 GHz.

As of today, the FS-TP Back-End is installed both in the Medicina and SRT radio telescopes. A new replica of the system is under construction for the Noto 32-m antenna.

Based on the results coming from the testing of this device built on microwave substrates PCB (printed circuit board), a new version of the FS-TP is under development. It will be upgradated adding a "polarimetric section". All next receivers will have on II° convertion board both these total power and polarimetric sections.

Tests carried out on this device, which is built on microwave substrates PCB (printed circuit board), provided insights leading to a new version of the FS-TP, at present in development. The device will be upgraded adding a "polarimetric section".

Multi-feed systems constitute a technological challenge, as they produce a huge number of signals. For example, in the Q-Band 19-feed receiver (under development), the number of signals that the back-end needs to manage will be composed by 19x2x8 sub bands (19 elements, 2 polarisations, 8 sub-bands), totalling to 304 polarimetric signals.

Moreover, in order to fully exploit the large bandwidth of modern receivers – up to 16 GHz – the new back-end design is based on splitting the signal first conversion in 8 sub-bands (for each polarisation). Using SMD (Surface Mounted Devices) components and PCB Boards, an important cost reduction will also be granted.

In the meanwhile a back-end for pulsar observations, to be installed on the SRT, is being completed in the Electronic labs. Its filtering system is based on 500-KHz filters and it is able to acquire Left and Right polarisations with a 500-MHz bandwidth. The minimum sample interval will be 50 microseconds.