Study of an Ultrawideband Monopole Antenna With a Band-Notched Open-Looped Resonator

A novel band-notched planar monopole ultrawideband (UWB) antenna is proposed. A notched band, located in the 5 GHz WLAN band, is created using a resonator at the center of a fork-shaped antenna. The resonator is composed of an open-looped resonator and two tapped lines. With the open-looped resonator, the antenna has a good band-notched performance and bandstop-filter-like response in the target band. A parametric study of the notched bandwidth is described that explored the antenna operating mechanism. Then, an equivalent circuit model illustrates the band-notched behaviors more clearly. The antenna input admittance calculated with the equivalent circuit model reasonably agrees with the HFSS simulated result. The proposed antenna also features flat gain frequency responses, small varied group delay and 15 to 35 dB gain suppression at the notched band. Accordingly, the band-notched antenna can effectively select target bands by adjusting these antenna parameters.