Design of a band-notched planar monopole antenna using genetic algorithm optimization

Genetic algorithm (GA) optimization is applied to the design of planar monopole antennas, which exhibit both ultrawideband (UWB) operation and a narrow-band frequency notch. Such an antenna is useful in applications involving wide-band communications where it is desired to mitigate interference with other radio systems colocated with the operating band. It is demonstrated in this paper that traditional band-notched planar monopole antennas exhibit asymmetry in radiation patterns within the notch band such that the attenuation provided by the antenna varies as a function of azimuth angle, which lowers the effective bandwidth of the notch. A GA optimizer, which uses of a weighted sum cost function related to impedance matching and radiation patterns at frequencies within both the wide operating band and narrow notch band, is used to improve the performance of the band-notch planar monopole antenna. A two-dimensional (2-D) matrix chromosome is used in the GA to represent a wide-range on planar element shapes. It is shown that the GA generates antenna designs that exhibit equal wideband performance as traditional band-notched designs, but have improved azimuth plane radiation pattern symmetry, which widens the effective notch bandwidth. The GA-generated antenna design is measured and compared with simulation.