Dual Circularly Polarized Spherical Phased-Array Antenna for Spacecraft Application

Design aspects of an active spherical phased-array antenna (SPAA) operating in dual circularly polarized (CP) mode are discussed here. Dual CP configuration with good cross-polarized isolation enables frequency reuse using polarization diversity. This design also implements sharing of the resources like amplifiers and phase shifters in an optimal way to reduce mass, power requirement, and cost of the antenna. The antenna is hemispherical in shape and maintains required effective isotropic radiated power (EIRP) over a hemispherical coverage area. Detailed analysis including the effect of failure of a few of the elements of the array and the measured results of the antenna at X-band are discussed here. This antenna has been used for transmission of payload data from a low Earth orbit satellite of ISRO.