Theory, Design, and Verification of Dual-Circularly Polarized Dual-Beam Arrays With Independent Control of Polarization: A Generalization of Sequential Rotation Arrays

In this article, the theory, design, and validation of planar array antennas capable of producing dual-circularly-polarized (dual-CP) dual-beam radiation with a single feeding network are reported. Importantly, the properties of the formed CP beams with different handedness can be independently controlled. Such a capability is achieved by exploiting both the in-plane rotation-induced Berry phase and excitation phase for all the linearly polarized array elements, which can be regarded as a generalization of the well-known sequential rotation arrays. Microstrip patch arrays with such single-feed dual-CP dual-beam functionalities can be synthesized through a straightforward analytical approach that accurately predicts the radiation patterns for both right- and left-handed CP beams. The proposed technique and design methodology were verified by two proof-of-concept microstrip arrays consisting of 8x8 linearly polarized circular patch elements operating in the K-band, one with uniform excitation amplitudes and the other with tapered excitations for sidelobe suppression. Both arrays were fabricated and measured, experimentally achieving a joint S-11 < -10 dB, axial ratio < 3 dB, and 3 dB gain bandwidth of more than 22.5%/20.0% and 16.7%/15.8%, respectively, for the right- and left-handed CP beams. Within this broad operational band, the beam squinting is on average within +/- 3 degrees. The proposed dual-CP dual-beam arrays have fully planarized structures, low profiles, wide operational bandwidths, and high polarization purity, making them useful candidates for applications including satellite communications, point-to-multipoint communications, and so on.