Controlling Antenna Sidelobe Radiation to Mitigate Ku-Band LEO-to-GEO Satellite Interference

Abstract

Low-Earth orbiting (LEO) satellites now can provide broadband service anywhere in the world, but they must share the radio spectrum with geosynchronous Earth-orbiting (GEO) satellites. The United Nations International Telecommunications Union (ITU) and the U.S. Federal Communications Commission (FCC) require that operators of LEO satellite systems avoid interfering with GEO satellite systems even though both use the same bands within the radio spectrum. Such interference can occur when a LEO satellite passes through an area between a GEO earth station and its intended GEO satellite. This is called an in-line event. LEO satellites that have beam steering capability can steer their main beams to avoid interfering with GEO earth stations, but even when they do this, LEO satellite antenna side lobes can still cause unacceptable interference. We describe here how these side lobes can be controlled to avoid such interference, and we develop estimates of maximum side lobe levels that must be maintained in currently deployed and future LEO satellite constellations.