Multiband Circularly Polarized Cavity-Backed Crossed Dipole Antenna

In this paper, novel designs of miniaturized and multiband circularly polarized (CP) cavity-backed crossed dipole antennas are proposed. Single-band and dual-band LC resonators are placed along both the arms of double-sided printed dipoles to realize dual-band and tri-band operations, respectively. Identical pairs of loaded dipoles are placed in crossed configuration to achieve dual-band and tri-band CP operations using vacant printed ring. Cavity-backed reflector is further employed to get enhancement in the 10-dB impedance bandwidth (IBW) and 3-dB axial ratio bandwidth (ARBW) along with unidirectional radiation pattern and wide 3-dB axial ratio beamwidth in the operating bands. Measured results confirm that the proposed dual-band cavity-backed crossed dipole antenna exhibits CP operation bandwidths (AR <; 3 dB and S₁₁ <; -10 dB) of 7.50% and 26.15%, with center frequencies at 1.87 and 2.83 GHz, respectively. The corresponding CP operating bandwidths for the tri-band cavity-backed crossed dipole antenna are 1.24%, 9.55%, and 14.95% centered at 1.61, 2.20, and 2.81 GHz, respectively. The proposed dual-band and tri-band antennas can be used in DCS/PCS/Global Star/UMTS/WLAN applications.