Abstract: A spatial power combiner includes a circularly corrugated horn 26, a meniscus lens 28, an amplifier array 16, and a layer of microwave absorbing material 34 on a housing interior 32. The lens 28 receives polarized microwave radiation from the horn 26 and collimates it, renders it in phase and with nearly uniformly amplitude, and distributes it across the lens aperture. The amplifier array 16 amplifies the radiation and re-radiates it, orthogonally polarized, to the lens 28, which focuses it back down the horn 26. An array of parasitic micropatches 24 between the lens 28 and amplifier array 16 provides impedance matching. A quarter-wave anti-reflecting coating 30 covers both surfaces of the lens 28. The microwave absorbing material 34 reduces or prevents resonance of higher order modes.