An apparatus includes an aperture layer coupled to a polarizer layer. The aperture layer includes an antenna and a filter. A circuit layer is mechanically and thermally coupled to the aperture layer. The antenna includes a square horn antenna made of a polymer material. The filter includes a waveguide filter having a first and a second piece separately molded. The waveguide filter includes a folded-back waveguide coupled to the horn antenna at one end and to the circuit layer at another end.