Design of Single-Layer Circularly Polarized Reflectarray With Efficient Beam Scanning

This letter presents the design of wideband, low-cost, single-layer, ultrathin, beam-scanning circularly polarized reflectarray (CP-RA) antenna with high-radiation characteristics. To obtain efficient single and multiple CP beams, a subwavelength unit cell based on Pancharatnam-Berry (PB) geometrical phase was used to increase the beam scanning efficiency. PB unit cell with periodicity of 0.28 lambda(o) and ultrathin thickness of 0.11 lambda(o) is used to achieve the required phase correction across the reflectarray aperture to produce a collimated right-hand circularly polarized (RHCP) beam in the desired direction. The unit cell has three plasmonic resonances and the proposed CP-RA consists of 43 x 43 PB unit cells and occupies an area of 215 x 215 mm(2). Both simulation and experimental results show that the proposed CP-RA produces RHCP pencil-beam in the desired direction with a 1 dB gain bandwidth (BW) of 24.5% from 17 to 24.5 GHz, 3 dB gain BW of 46.15% from 15 to 24 GHz, peak aperture efficiency of 49.93%, 3 dB axial ratio (AR) of 46.15%. Furthermore, a beam scanning with 70 degrees (+/- 35 degrees) scanning angle is achieved with gain scanning loss of less than 3 dB and beam squint of less than 1.3 degrees within the whole frequency band and for all scanning angles.