Low-profile omnidirectional circularly polarized antenna based on substrate integrated waveguide technology

Abstract

A substrate integrated waveguide (SIW) circularly polarized (CP) antenna with omnidirectional radiation in the azimuthal plane is proposed. The antenna consists of five identical end-fire CP antenna elements in a pentagonal array configuration, which is loaded on a circular substrate. Each element contains an H-plane horn antenna in SIW structure and a printed dipole antenna. Five parasitic curve elements are introduced to improve the omnidirectional property of the antenna. Combined with complementary dipoles theory and SIW technology, prototype antenna is designed, fabricated and measured. With a low profile of 0.024λ0, the antenna has a 10-dB return-loss impedance bandwidth of 4.08% (2.4∼2.5 GHz) and a 3-dB axial-ratio (AR) bandwidth of 5.76% (2.36∼2.50 GHz). The antenna works well in the 2.45 GHz ISM band, with good cross-polarization and excellent omnidirectional property.