Miniaturized Monopole Wideband Antenna with Tunable Notch for WLAN/WiMAX Applications

A tunable notched band small monopole antenna is studied and investigated in this chapter. The rejected band was achieved by introducing an additional inner crescent shape along with an outer shape over the surface of the substrate. By placing a small capacitor (varactor) between the inner and outer arches, the center frequency of each notch can be individually shifted downward. The antenna exhibits a wide impedance bandwidth from 1.5 to 5 GHz with good impedance matching (VSWR ≤2) and a tunable range of band rejection frequency (center frequency from 2.38 to 3.87 GHz). To validate the theoretical results, the antenna is fabricated and tested. Simulated and measured results are presented and show a wideband impedance bandwidth with a reconfigurable notched band, stable radiation patterns, and constant gain.