A Novel Compact Wideband Planar Inverted-F Fishbone Antenna With Load-Bearing Capacity and Its Application in CP Arrays

A novel compact wideband load-bearing planar inverted-F fishbone antenna (PIFFA) element and a circularly polarized (CP) unit based on PIFFA are proposed. The main radiator of the PIFFA is a folded fishbone structure with dimensions of
$0.14\lambda _{0} \times 0.19\lambda _{0} \times 0.15\lambda _{0}$
, which is excited by a monopole. It works in hybrid mode dominated by odd mode, which realizes directional radiation. The PIFFA has an available bandwidth of 1.29–2.46 GHz (62.4%) and a gain ranging from 3.98 to 5.76 dBi. Four PIFFA elements are rotationally symmetric arranged around the center and construct the compact CP unit. The measured operating bandwidth of the CP unit is 1.18–1.91 GHz (47.2%) and the gain ranges from 6.2 to 8.6 dBi. It is noted that the CP unit can bear the load of 1000 kg/cm2 without clear performance deterioration. In addition, four CP units are extended to form a linear 1-D array with broadside dual circular-polarization beam scanning capability. The 1-D array achieves a CP scanning range of ±61° at 1.25 GHz in the experiment. These results demonstrate that antennas designed with a folded fishbone structure have excellent performance and practical value, making them suitable for a wide range of high-speed wireless communication systems.