Adaptive polarization for spacecraft communications systems

Communications antennas on spacecraft are usually circularly polarized. As the spacecraft maneuvers, its antenna and the ground station antenna may not point directly at each other. Antennas not properly aligned for optimal power transfer usually create a polarization mismatch and a loss in transferred power. In this paper, a scheme for compensating for polarization mismatch is considered using crossed dipoles. One of the crossed dipole´s amplitude and phase is adjusted using numerical optimization, and the Numerical Electromagnetic Code generates the electromagnetic response. Optimizing only for circular polarization produces losses in radiated power that offset the polarization correction. The polarization optimization may improve power transferred when the spacing between the orthogonal dipoles is increased. The next step modified the optimization process to consider power transferred. With this improvement, the power transferred always increased up to a maximum of 2.0 dB at θ = 80°. Using adaptive crossed dipoles at the transmitter and receiver was also considered and further improved the model.