2020/06/01 by B. S. Girish, K. S. Srivani, Ravi Subrahmanyan +6 · 1 citation
Physics and Astronomy · #Antenna (radio) #Astrophysics and Star Formation Studies #COSMIC cancer database #Dark Ages #Digital radio #Digital signal processing #Fermi Gamma-ray Space Telescope #Radio Astronomy Observations and Technology #Radiometer #Redshift #Reionization #Spectrometer #Superconducting and THz Device Technology #astro-ph.IM
paper · pdf · doi:10.1142/s2251171720500063
published as Journal of Astronomical Instrumentation Vol. 09, No. 02, 2050006 (2020) · 16 pages, 8 figures
openalex publication_date 2020/06/01 · openalex created_date 2020/06/19 · arxiv created 2021/04/01 · arxiv updated 2021/04/02 · openalex updated_date 2026/08/05
In the currently accepted model for cosmic baryon evolution, Cosmic Dawn (CD) and the Epoch of Reionization (EoR) are significant times when first light from the first luminous objects emerged, transformed and subsequently ionized the primordial gas. The 21[Formula: see text]cm (1420[Formula: see text]MHz) hyperfine transition of neutral hydrogen, redshifted from these cosmic times to a frequency range of 40[Formula: see text]MHz to 200[Formula: see text]MHz, has been recognized as an important probe of the physics of CD/EoR. The global 21[Formula: see text]cm signal is predicted to be a spectral distortion of a few 10’s to a few 100’s of mK, which is expected to be present in the cosmic radio background as a trace additive component. Shaped Antenna measurement of the background RAdio Spectrum (SARAS) is a spectral radiometer purpose designed to detect the weak 21[Formula: see text]cm signal from CD/EoR. An important subsystem of the radiometer, the digital correlation spectrometer, is developed around a high-speed digital signal processing platform called pSPEC. pSPEC is built around two quad 10-bit analog-to-digital converters (EV10AQ190) and a Virtex 6 (XC6VLX240T) field programmable gate array, with provision for multiple Gigabit Ethernet and 4.5[Formula: see text]Gbps fiber-optic interfaces. Here, we describe the system design of the digital spectrometer, the pSPEC board, and the adaptation of pSPEC to implement a high spectral resolution (61[Formula: see text]kHz), high dynamic range ([Formula: see text]:1) correlation spectrometer covering the entire CD/EoR band. As the SARAS radiometer is required to be deployed in remote locations where terrestrial radio frequency interference (RFI) is a minimum, the spectrometer is designed to be compact, portable and operating off internal batteries. The paper includes an evaluation of the spectrometer’s susceptibility to RFI and capability to detect signals from CD/EoR.