Ultrawideband Optimized Profile Monopole Antenna by Means of Simulated Annealing Algorithm and the Finite Element Method

Monopole antennas with an optimized profile are described. They are designed by means of a global optimization using the simulated annealing algorithm and the Finite Element Method. Two designs are presented. The first optimized profile monopole is designed to obtain the lowest return losses over the extremely high bandwidth that lies between 4 GHz and 20 GHz. Better than 17 dB return losses are obtained in all the bandwidth. This initial result is the basis for a more detailed work. The second antenna is designed to optimize return losses in the 2 to 11 GHz band. This frequency band has been chosen to cover the definition of ultrawideband (UWB). Return losses of less than 24 dB have been achieved in the whole band in the simulation step using an infinite ground plane. A prototype has been built, measured and resimulated. Return losses of less than 20 dB have been measured in the whole band using a finite ground plane. Results from the simulation of the prototype with the finite plane show an excellent agreement with measurements. A final parametric study of the optimization variables is carried out.