Feed horns have always held a fascination for me, just make a bit of shaped metal and you can control electromagnetic radiation.  In my opinion, a great super power to have!  However, when you put several feed horns together you can create something even more powerful and informative. 

A feed horn is a type of horn antenna, which means it is formed by flaring the sides of metal waveguide into a horn like shape thus creating a controlled beam of radio waves.  A monopulse system is one that sends out multiple overlapping beams at the same time.  Typically, a monopulse antenna is an antenna array which is symmetrical about boresight.