Abstract
In this article, the least-squares support vector machines (LS-SVM) technique is used in a finite-difference time-domain method to extrapolate the time domain responses. The particle swarm optimization method is used to optimise the hyperparameter of the LS-SVM algorithm, which should be tried again and again randomly. By modelling the novel microstrip circulator, we can eliminate some of the instabilities that arise in late times in the time domain. The frequency-dependent scattering parameters of the microstrip circulator are calculated over a wide band of frequencies with this hybrid method. The numerical results have a good agreement with the measurement.