A Multifunctional Full-Polarization Reconfigurable 28 GHz Staggered Butterfly 1-D-Beam Steering Antenna

A novel multifunctional staggered $8\,\,\times12$ Butterfly phased array antenna is proposed at Ka-band (28 GHz) for 5G communications with key features of full-polarization reconfigurability, flexible radiation pattern, and wide-angle 1-D-beam steering performance. The unit cell of the proposed array is a two Butterfly radiating antennas separated by $2\lambda \text{g}$ ( $\lambda \text{g}\,\,=$ effective wavelength) with two ports, where each Butterfly is a sequentially rotated series-fed microstrip patch antennas. Full-polarization reconfiguration (right-hand circular polarization (RHCP), left-hand circular polarization (LHCP), Linear-X, and Linear-Y polarization) is achieved by suitable excitation of the ports to realize increased system capacity. Flexible radiation pattern with dynamic 3 dB gain-beamwidth from 16° to 90° is achieved to realize a variable cellular range, angle, and gain requirements. The proposed staggered planar array configuration reduces the spacing between the adjacent series-fed linear array to $0.45\lambda _{0}$ , where $\lambda _{0}$ is the free-space wavelength at 28 GHz. The proposed array size of $8\,\,\times12$ Butterfly provides beam steering up to ±63° without any grating lobes. Analytical study using a periodic leaky-wave antenna (LWA) theory is included to provide insights into the radiation characteristics of the Butterfly series-fed linear array antenna. The beam steering characteristics were verified by using measured patterns of the individual branches and by applying the computed array factor. The full-polarization reconfiguration and flexible radiation patterns with sidelobe reduction are implemented and experimentally verified with a 16-channel Analog Devices ADMV4821 RFIC Ka-band beamformer.