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

This work proposes an ultrawideband (UWB) monopole antenna with multiple integrated narrow reflectionless notched bands (RNBs). A multimode resonant slot is etched in the monopole radiator to generate high-impedance open-circuit characteristics at the antenna feeding point. Multiple coupled and embedded absorptive stubs are integrated into the microstrip feed line to dissipate the input notched-band (NB) energy, enabling RNB 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 RNB antenna is designed based on the conceptual circuit model of multiple RNBs to inhibit the interference from 3.5 GHz [microwave access (WiMAX)], 5.5 GHz [wireless local area network (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 NBs while maintaining the reflection coefficient below −10 dB from 3 to 10 GHz.