Design of Wideband Quadruple-Ridged Flared Horn Feeds for Future Radio Telescopes

Balanced excitations are required to achieve ultra wideband performance with the novel reflector antenna feeds consisting of pair(s) of interleaved spiral, log-periodical or other travelling-wave structures, which are currently being developed for radio astronomic instruments [1]–[3]. This excitation is commonly realized by using a balun interfacing the balanced antenna to single-ended amplifiers. However, practical designs of such passive networks are often bulky and lead to power dissipation losses. Power dissipation reduces the antenna radiation efficiency and increases the system thermal noise temperature. Another limiting factor is that the ultra wideband balun design restricts the reference impedance for the optimum noise matching between the antennas and low-noise amplifiers (LNAs). To obviate these disadvantages, differential low-noise amplifiers (dLNA), which can be directly integrated at the antenna terminals, represent an interesting alternative solution