Digital backend receiver for radio astronomy applications using FPGA

Abstract

The ability of an antenna array to work as a spatial filter for the targeted objects of observation in the sky has had a great impact on the ways and techniques in which observation and detection of EM waves have evolved over time. With increasing requirements and curiosity of the man, it is becoming very essential for us to be able to detect even the faintest of EM waves that are coming from the sky above. With limited resources and direct dependence of the gathering ability on the collecting area of the telescopes, it is not always easy for us to play with the size of the receivers. Rather, to better our resolution of observation, we can always make use of more than one antenna, with an increased effective collecting area and bettered resolution. This is where the concept of antenna arrays comes into the picture[2]. Not only the resolution which is enhanced, but it also makes our system well capable of spatially filtering the sky for the objects of our interest and blocking all the other interfering objects. The direction of orientation of our effective antenna radiation pattern can be precisely controlled by controlling the delay provided in the accumulation cycle of the incoming signals. This is the underlying concept of Beam Forming and Beam Steering. But it is not always as easy as it sounds. With the number of antennas increasing in the system, increases the amount and complexity of signal processing that we need to do. Even an error of a few nanoseconds can completely destroy the information we are trying to collect. Hence, to do this tedious processing, we incorporate a device known as Field Programmable Gate Array (FPGA). The FPGA serves to be the complete backend of our system, which handles the collection, accumulation, phase shifting, FFT and binning of our signals and finally transmits them into a PC to be presented in a readable format.