Development of receiving APAA using DBF for HAPS to provide IMT-2000 service system

High altitude platform station (HAPS) would be located at 20 km above sea level and has a multibeam antenna system. In the multibeam antenna system using the same frequency in all beams, we need a strict radiation beam pattern to reduce the interference between beams and into other services. We analyze the required minimum errors of amplitude and phase distribution on each channel because they affect the sidelobe level in the radiation beam pattern. The statistical simulation results investigated in this paper reveal that the active phased array antenna (APAA) system based on the digital beamforming (DBF) technology is an efficient solution for the HAPS payload. We introduce a prototype of a receiving DBF APAA with 19 elements, and demonstrate the characteristics in IMT-2000 frequency bands.