Abstract

The Indian Institute of Astrophysics operates a low frequency (< 150 MHz) radioheliograph for dedicated observations of the solar corona at the Gauribidanur radio observatory (≈ 77°E 14°N) located about 100 km north of Bangalore¹ (Ramesh et al. 1998; Ramesh 2011). The basic receiving element in the radioheliograph (called the Gauribidanur RAdioheliograPH, GRAPH) is a log-periodic dipole (LPD). The array has 384 of them arranged in a ‘T’ configuration. The arms of the ‘T’ are in the east-west and north-south directions. The LPDs in the each of the above two arms are subdivided into 32 groups. RF signal from the 64 antenna groups in the array are presently correlated using a 4096-channel correlator system comprising of discrete digital circuit elements (Ramesh et al. 2006). Taking advantage of the developments in the field of signal processing, a FPGA based digital backend system is being developed for the GRAPH. To this date, a prototype 8-channel system has been designed and fabricated. All possible correlations between signals from 8 dierent antenna groups can be performed with this system either online or oine.