A multiplying interferometer for 1.3 GHz using two Yagi antennas

This note describes the small digital correlation interferometer, operating at 1.3 GHz, designed at the Istituto di Radioastronomia which is part of the National Institute for Astrophysics. It uses two Yagi–Uda antennas to collect the radio-astronomical signal, which is converted to a base band of 0–4 MHz utilizing rf and digital blocks, in the same manner as a normal scientific radio telescope. The correlation of the two signals is performed in real time and a commercial PC is used to collect and visualize the fringe pattern. It is possible to detect the strongest radio sources such as the Sun, Cassiopeia A, Taurus and Cygnus A. The interferometer designed is simple, affordable and is suitable as a demonstration/teaching tool.