A Null-Filled Axisymmetric Secant-Square-Shaped Beam Antenna for Unmanned Aerial Vehicles

In this letter, an antenna with a null-filled axisymmetric secant-square-shaped beam for the unmanned aerial vehicle is proposed. The proposed antenna consists of four monopoles with sequentially rotated feed and a coupling-fed grooved circular patch. The radiation power ratio of the monopoles and the patch is used to shape the axisymmetric beam. The effect of the ground is also investigated to operate positively on beam shaping. A prototype was fabricated to validate the method and the performance of the proposed antenna. The gain curves of the proposed antenna coincide well with the secant-squared (sec
²
) curve from
θ
= 0° to
θ
= 60° in all azimuthal angles with root mean square error (RMSE) below 1.35 dB in 5.5–5.7 GHz.