Parallel Rectangular Open Slots Structure in Multiband Printed Antenna Design

Three parallel rectangular open slots (PROSs), etched on the ground plate of the printed antennas, is presented for multiband applications. By employing the differential evolution (DE) algorithm to optimize the size and position of the PROSs, the reflection coefficient less than
$-10~\hbox{dB}$
at the global positioning system (GPS), Wireless-Fidelity (Wi-Fi) and worldwide interoperability for microwave access (WiMAX) bands, can be achieved without using the trial and error method. To evaluate performance of the proposed PROSs structure, a triple-band antenna (Ant I) is fabricated and measured together with a four-band antenna (Ant II). The measured results, which agree well with the simulated ones, show good impedance matching and nearly omnidirectional radiation patterns for each antenna.