Very Low-Profile Top-Loaded UWB Coupled Sectorial Loops Antenna

In this letter, we present a new very low-profile monopole-type antenna. The proposed antenna height is <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$0.053\lambda_{0}$</tex> </formula> , where <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\lambda_{0}$</tex> </formula> is the minimum operating wavelength and operates over 148% relative bandwidth. The antenna is based on the principle of top-loading of coupled sectorial loop antenna (CSLA). Introducing a series capacitive gap in the top-loading plate and the CSLA fins allows for achieving ultrawideband operation and very low antenna height simultaneously. The proposed structure is also relatively easy and cost-effective to fabricate using standard printed circuit board (PCB) fabrication technology. A parametric study is presented to show the effect of the different dimensions on the antenna performance. A prototype antenna is fabricated and measured. The measurements and simulation results show good agreement and indicate that a <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\hbox{VSWR}}&lt;2$</tex></formula> over 0.9–6 GHz can be accomplished. It is also shown that the radiation pattern has omnidirectional characteristics over more than two octaves.