Design and circuit analysis of a single and dual band-notched UWB antenna using vertical stubs embedded in feedline

Within the frequency band designated by the FCC for UWB systems, there are other frequency bands that are also designated for use for other technologies like WLAN (5.15 - 5.35 GHz) and WiMAX (3.3-3.7 GHz). These systems can cause interference with UWB systems when operated at the same time. Therefore, an antenna operating in the UWB spectrum needs to have band-notch capabilities in order to mitigate interference resulting from nearby communication systems operating within the UWB frequency band. In this paper, the notched bands are achieved by using vertical stubs protruded from a microstrip feedline. The antenna is etched on a 25 × 30 mm² substrate. Two antenna structures are presented; one is designed to notch an intended narrowband from 3.3 - 3.6 GHz and the second is designed to include an additional band notch from 5.15 - 6 GHz. The simulations and measurements show that the proposed antennas achieve an ultra-wide bandwidth of 3-10.6 GHz with successful single and dual band-notches, good gain and good group delay rejection in the notch bands. Stable radiation patterns with low cross polarization are also realized across the operating bandwidth. A detailed analysis of how the filtering is also achieved using circuit theory is presented in this work as well.