Horn antenna, also known as microwave horns, are antenna modified by a waveguide and flared metal horn in a conical, square or rectangular shape. The horn apparatus allows the antenna to emit radio waves as a beam, increasing the directivity of the emissions. A horn antenna commonly operates at microwave and ultra-high frequencies exceeding 300 MHz, offering a degree of directivity, a broad bandwidth and a low standing wave ratio (VSWR). Applications of horn antenna include radiating RF in an anechoic chamber to perform radiated immunity EMC testing.