A Low-profile and Ultra-wideband Monocone Antenna with Shorted Top Hat Based on A Concave Curve

This manuscript presents a monocone antenna with the merits of ultra-wideband and low profile for wireless communication applications. Firstly, a curve, which is determined by the formula given by an exponential function, is used to express the side surface profile of the monocone antenna. And the parameters of the formula of the curve are analyzed in order to improve impedance matching of the antenna at higher frequency band. Furthermore, four shorting pins and a top hat etched with a ring slot and eight circular arc slots are loaded to move the working band towards lower band, then the band is further widened. The simulated results reveal that the proposed monocone antenna with a small height of only 0.06
$\lambda$
low can cover a very large band from 1.8 to 23.5 GHz with a relative bandwidth of 171.5% for VSWR less than 2.5. The antenna also maintains the gain of 2 dBi to 7 dBi over the whole frequency band. Compared with other antennas of the same height, the antenna can cover a larger bandwidth.