Wideband low-profile null-filled monopole antenna for aircraft flush-mount applications

A wideband low-profile null-filled monopole antenna for aircraft flush-mount applications is presented. The antenna consists of a semicircular monopole and a direct-fed dual loop in a flanged cylindrical cavity. The zenith null in the monopole radiation pattern is filled by horizontal currents of the dual loop. Measurement shows that the proposed antenna has a reflection coefficient of <;-10 dB over 4.53-7.43 GHz, 6.45 dBi maximum gain, -0.8 dBi filled null depth and a -3.7 dBi minimum horizontal gain at 6 GHz.