Large angular electronic beam steering antenna for space application

In order to replace a large phased array, antenna subsystems usually combine a large reflector, a small phased array, and an arrangement of small reflectors, which form a large image of the array over the main reflector aperture. This way one can get a large-aperture electronically steerable antenna, using only a small phased array. The basic idea of such an antenna is to use the two offset fed paraboloidal reflectors in such a way that the off-axis aberrations tend to cancel each other. The implementation of a correcting lens in the common focal plane is proposed. The objective is to enlarge the off-axis aberration matching domain, so that the scanning capability is increased (15 beamwidth/40 beamwidth). As an application, a Ka-band mission is discussed for a 3-m-diameter antenna (26 GHz) with a field of view of +or-10 degrees as required for the Data Relay Satellite. It is confirmed that the scanning limitation of the offset fed Gregorian antenna has been relaxed from approximately 15 beamwidth to 40 beamwidth by the use of a corrective lens implemented in the common focal area.<>