A Planar Quasi-Magnetic–Electric Circularly Polarized Antenna

A new planar quasi-magnetic–electric circularly polarized (CP) antenna is proposed. The antenna has a simple planar structure with a small size and a single feed, and produces an omnidirectional CP radiation pattern. It is based on a quarter-wave shorted patch connected with two printed strips. The tangential electric field at the main open aperture of the shorted patch can be considered as an equivalent magnetic current, while the two strips contribute two electric currents. With a single feed, the proposed antenna exhibits an inherent phase difference of about 90° for the two kinds of currents, and therefore, a CP radiation is obtained. The antenna is designed and fabricated. Measured results show that the antenna has an impedance bandwidth of 4.3%. In the band of interest, the antenna generates a circular polarization and an omnidirectional pattern in the plane perpendicular to the magnetic and electric currents, with an average axial ratio below 1.5 dB and a gain between 2.4 and 3.3 dBi.