Design of Switchable Hairpin Band Pass Filters for Low Frequency Radio Astronomy

In this paper, we present a novel switched band pass filter bank designed using hairpin line topology. This new filter bank design is implemented to facilitate narrow bandwidth mode observations for the upgraded GMRT (uGMRT), as well as providing an option for filtering out strong radio frequency interference that may come up in some parts of the wideband system. Radio Astronomy today requires wideband frequency coverage for achieving higher sensitivity and frequency agility for varied nature of astrophysical observations. As part of a major upgrade, the Giant Metrewave Radio Telescope (GMRT) is going through an increase in the bandwidth coverage from 50 to 1500 MHz, with a maximum instantaneous bandwidth of 400 MHz for increasing the sensitivity of the telescope. As a part of this upgrade, the existing front-end receiver electronics is being modified by introducing wideband low noise amplifiers, octaveband polarizers with low insertion loss, low loss wideband directional couplers for noise injection, wideband filters and high dynamic range broadband post-amplifiers.