| Name: TJayadev Ashok |
| Affiliation: Raman Research Institute |
| Conference ID: ASI2026_766 |
| Title: High Accuracy in-situ Antenna reflection coefficient measurement system for the SARAS experiment |
| Abstract Type: Poster |
| Abstract Category: Facilities, Technologies and Data science |
| Author(s) and Co-Author(s) with Affiliation: Thiyyannoor Jayadev Ashok(Raman Research Institute, Bangalore-560080, India), Somashekhar R(Raman Research Institute, Bangalore-560080, India), Dr Saurabh Singh(Raman Research Institute, Bangalore-560080, India), Adarsh Kumar Dash(Raman Research Institute, Bangalore-560080, India), Kasthuri S(Raman Research Institute, Bangalore-560080, India) |
| Abstract: The primary objective of the SARAS (Shaped Antenna measurement of the background RAdio Spectrum) experiment is to detect the global sky-averaged 21 cm emissions from the epoch of reionization (EoR). The hyperfine spin-flip transition of neutral hydrogen produces photons of frequency 1.42 GHz. These photons are redshifted into the 40 to 200 MHz band and may be observed by specially designed radiometers. The signal presents itself as a spectral feature and its detection would provide insight into the physics of the early universe. However, the signal is several orders of magnitude weaker than foregrounds from galactic synchrotron emissions in the same band. Moreover, the band is also heavily contaminated by RFI (Radio Frequency Interference) making detection challenging. The SARAS antenna is designed to have spectrally smooth properties (Beam and Reflection Coefficient) to maximize signal discernability. However, at the levels of sensitivity desired, even slight variations in the system transfer function can hinder signal detection prospects. Hence to further enhance instrument sensitivity, an architecture for high accuracy, in-situ measurement of the antenna’s reflection coefficient has been developed. The designed system features novel broadband noise injection, simultaneous measurement of injected and reflected waves to account for gain drifts, optical isolation between receiver and digitizer to avoid standing waves, and precision-load based calibration for characterizing the measurement system itself. A modular prototype system was built and tuned until a required sensitivity of 1 part in 10^5 was achieved. After validation of the architecture, the entire RF chain was miniaturized and integrated onto a PCB. This system was also tested and has achieved the desired level of sensitivity. In this talk I will be presenting the detailed architecture of this system and the results obtained so far. |
