A sigmoid function is used to define a smooth profile for possible use in septum designs. In addition, Particle Swarm Optimization (PSO) is used to optimize the sigmoid-profiled septum polarizer. PSO is applied to a sigmoid septum as well as a stepped septum, and the performance of both designs is further compared. Both septum designs are selected to be optimized for a 25% bandwidth, and the impedance matching and axial ratio is analyzed. Furthermore, the reflector antenna system is investigated utilizing the optimized septum horns as a feed for a 15λ parabolic reflector antenna. A directivity of approximately 32 dB is attained for both parabolic reflector antenna systems.