A Reconfigurable Beamsteering Antenna Array at 28 GHz Using a Corporate-fed 3-Bit Phase Shifter

A 3-bit beam steerable antenna array based on a microstrip line is designed and implemented at 28 GHz for millimetre-wave application. The antenna consists of an 8-element tightly stacked aperture and a switchable feeding network. The latter consists of a one-to-eight-way uniform microstrip corporate-fed power divider and is separated from the radiating element by a ground plane. To achieve coupled feeding, the ground plane has two rows of slots under each antenna element. A switching mechanism was implemented on the microstrip line to realize 3-bit periodic phase shifting for beamsteering. By sampling 8 feed points with a separation distance of λ/8, a 3-bit phase shifter was constructed with phases of 0º, -45º, -90º, -135º, -180º, -225º, -270º, and -315º. Continuous beamsteering was achieved from -50º to +50º by switching eight different sampling states, both in numerical calculation and in simulation. The design was verified by fabricating and testing three different prototype configurations at 28 GHz. The measured prototypes showed an excellent match with the simulation results. Notably, the maximum measured gain was found to be 13.44 dBi with a gain threshold of 10 dBi within the steering range (viz. 100º).