Optimization of the Profile of a Planar Ultra Wide Band Monopole Antenna in Order to Minimize Return Losses

In this paper, a planar ultra wide band antenna designed to minimize return losses is presented. Low return losses over an extremely broad bandwidth are obtained performing a global optimization, implemented using the simulated annealing algorithm, over the profile of a planar monopole. To perform the required analysis in each optimization step, a versatile and fast tool was required. The finite element method along with the SFELP formulation was used to try to meet this criteria for the analysis tool. As a result, simulations showed that return losses of less than 14 dB have been achieved in the whole frequency band. Simulations were performed using an infinite ground plane to reduce computation effort and therefore optimization time. To validate the method, a prototype was built with the obtained data. Return losses of less than 13 dB were obtained in the whole band using a finite ground plane of near lambda in the low frequencies. Simulation results with the infinite ground plane show an excellent agreement with measurements.