Wideband Circularly Polarized Array Antennas With Sequential-Rotation Polarization Grid and Simplified Full-SIW Feeding Networks

Two wideband circularly polarized (CP) antenna arrays are proposed, based on sequential rotation (SQR) arranged polarization grid and specially designed wideband full-substrate integrated waveguide (SIW) SQR feeding network. First, as the CP array element, an SIW-excited log-periodic dipole array (LPDA) loaded with an inhomogeneous polarization grid is designed. Then, the element with the grid is extended into a 2×2-element SQR array, and a wideband planar SIW-feeding cavity is used to provide the full-SIW array feeding. The SQR configuration is simplified by exploring the symmetric property of the LPDA dipole elements for 180° phase shift. Finally, in order to solve the high sidelobe problem existing in the first array design, another full-SIW array configuration with a new 3-D SIW-feeding cavity for the purpose of element spacing reduction is proposed. Another SQR network simplification method is studied here in favor of the 3-D SIW-feeding cavity, in which the out-of-phase power division property of the SIW E-plane junction is explored. With this configuration, a much lower sidelobe result is obtained by the second array. The measured results indicate that both arrays have advantages of wide CP working bandwidth (37%), high efficiencies (~80%), and also wide 3 dB gain bandwidth (39%).