Equivalent Circuit Modeling of Broadband Antennas using Vector Fitting and Particle Swarm Optimization

In this paper, the vector fitting was introduced for the robust rational function approximation of broadband antennas. The constrained PSO was then proposed to optimize the sample locations to find the best passive rational function model. The application of the technique to two broadband antennas resulted in RMS errors of 4% and 1%, respectively. However, the method does not guarantee that a passive function can always be found, even though the technique is very successful in all of the antennas tried so far