Slotted Printed Monopole UWB Antennas with Tunable Rejection Bands for WLAN/WiMAX and X-Band Coexistence

Four versions of the compact hexagonal-shaped monopole printed antennas for UWB applications are presented. The first proposed antenna has an impedance bandwidth of 127.48% (3.1 GHz to 14 GHz), which satisfies the bandwidth for ultra-wideband communication systems. To reduce the foreseen co-channel interference with WLAN (5.2 GHz) and X-Band systems (10 GHz), the second and third antennas type were generated by embedding hexagonal slot on the top of the radiating patch. The integration of the half and full hexagonal slots created notched bands that potentially filtered out the sources of interference, but were static in nature. Therefore, a fourth antenna type with tunable-notched bands was designed by adding a varactor diode at an appropriate location within the slot. The fourth antenna type is a dual-notch that was electronically and simultaneously tuned from 3.2 GHz to 5.1 GHz and from 7.25 GHz up to 9.9 GHz by varying the bias voltages across the varactor. The prototypes of the four antenna versions were successfully fabricated and tested. The measured results have good agreement with the simulated results.