omnidirectional pattern

This paper presents a novel omnidirectional circularly polarized antenna with simple and low cost configuration designed by a combination of tilted semi loops antenna for unmanned aerial vehicle such as drone and quadcopter. Length of each semi loop is one wavelength that has been repeated around antenna axis with a specific angle. The 90° phase difference between two equally orthogonal polarized components is inherently provided by semi-loops and without the need for exciting semi-loops 90° out of phase. Symmetric configuration antenna yields in circular polarization in both the azimuthal and elevation plane. The measured results show that the 10-dB impedance bandwidth is 390MHz (range from 2.1GHz to 2.5GHz) at frequency of 2.45GHz and axial ratio bandwidth for less than 3dB is 400MHz (range from 2.1GHz to 2.5GHz). Also this antenna has a right hand circular polarization whose difference between the measured left hand circular polarization and the right and circular polarization gain is about 20 dB. The right hand circular polarized gain is about 1.5dBi.