Analysis and Design of Multiple Narrow Reflectionless Notched Bands Integrated UWB Monopole Antenna

This work proposes a ultrawideband (UWB) monopole antenna with multiple integrated narrow reflectionless notched bands (RNBs). A multi-mode resonant slot is etched in the monopole radiator to generate high-impedance open-circuit characteristic at the antenna feeding point. Multiple coupled and embedded absorptive stubs are integrated into the microstrip feed line to dissipate the input notched-band energy, enabling RNBs characteristics. A single RNB antenna is initially analyzed and designed to demonstrate the operating mechanisms of the resonant slot and coupled absorptive stubs, as well as the conditions for RNB. Then, a triple RNBs antenna is designed based on the conceptual circuit model of multiple RNBs to inhibit the interference from 3.5 GHz (WiMAX), 5.5 GHz (WLAN) and 7.4 GHz (Satellite communications). All the results validate the mechanism and indicate that the proposed antenna can significantly reduce the radiation efficiency and the realized peak gain in the multiple narrow notched bands while maintaining the reflection coefficient below -10 dB from 3-10 GHz.