Ultrawideband Tree-Like Biconical Antenna With Radiation Null Mitigation for Stable Gain and Radiation Pattern

This work presents a novel biconical antenna producing stable gain and radiation patterns in an ultrawide operating bandwidth. Conventional biconical antennas have ultrawide bandwidths, but their gains and radiation patterns vary significantly as their electrical sizes become large at high operating frequencies. Our analysis shows that radiation nulls in the elevation plane are the major cause of unstable radiation patterns because they split radiation beams. A tree-like biconical antenna is designed with a continuous flare angle to mitigate the azimuthal radiation null and retain a stable azimuthal gain. In addition, the biconical antenna is designed with a curved waistline to mitigate radiation nulls at large elevation angles and further suppress gain variation. Measured results show that the proposed antenna has a bandwidth of 157% (0.6 GHz to 5 GHz). Stable radiation patterns are produced in the operating bandwidth with a stable gain varying between 1.1 dBi and 2.3 dBi. The antenna is promising for providing uniform signal coverage and measurement in an ultrawide bandwidth due to its stable radiation characteristics.