Low-Profile, Quasi-Omnidirectional Substrate Integrated Waveguide (SIW) Multihorn Antenna

A low-profile, quasi-omnidirectional substrate integrated waveguide (SIW) multihorn antenna is proposed for small nonmetallic unmanned aerial vehicle (UAV) applications. The proposed antenna consists of four H-plane horn antennas and four matching vias. The four H-plane horn antennas are integrated in a single rectangular substrate using the SIW technology and are located concentrically toward the four edges of the substrate. Four shorting vias are designed to match the horn antennas without increasing the antenna size. The proposed antenna is fed by a probe at the center of the substrate. The antenna is vertically polarized and has a very low profile (0.028λ 0 ). The radiation pattern of the antenna is quasi-omnidirectional on the horizontal plane. A prototype with a dimension of 95.5 × 95.5 × 3.5 mm 2 (0.76λ 0 × 0.76λ 0 × 0.028λ 0 ) is designed, fabricated, and measured. The antenna achieves an impedance bandwidth of 2.1% from 2.39 to 2.44 GHz. The antenna does not need a ground plane. Thus, it is a good candidate for small nonmetallic UAV applications.