A Tri-mode Horn Feed for Gravitationally Balanced Back-to-Back Reflector Antennas

The concept of tri-mode feeds was used to lower the cross-polarization level in far-field pattern of offset parabolic reflector antennas. First, the complex mode coefficients of a tri-mode horn are optimized by using particle swarm optimization (PSO) technique. Using optimized complex mode coefficients, the performance of the reflector is simulated to verify the effectiveness of the method. The horn is then designed to provide the calculated optimum mode coefficients. The performance of the reflector is then simulated when it is fed by the designed horn and the results are compared with PSO optimized horn case. In addition, a simulation was performed to evaluate the bandwidth in which the horn can lower the level of cross polarization for at least 10 dB. The acceptable level of cross polarization verifies the possibility of utilizing these gravitationally balanced back-to-back reflectors fed by matched feed horns for narrowband applications in future spaceborne antenna missions requiring spinning platforms