Linearly and circularly polarized reflectarray antennas with 4-arm archimedean spiral lattice

Abstract

In this paper, linearly and circularly polarized reflectarray antennas with 4-arm Archimedean spiral lattice (LP-RAASL and CP-RAASL) have been designed and simulated. A perforated unit-cell element for the reflectarray is developed to cover about 360o phase variation range. The designed element has same phase response for vertical, horizontal and circular polarizations depending on the polarization of the incident wavefront. The 4-arm Archimedean spiral shape is used as a filled pattern for the positioning of the unit-cell elements of the reflectarray. The proposed reflectarray has a circular aperture with a radius of 370 mm, consisting of 400 unit-cell elements. The circular horn antenna is placed at 370 mm from the reflectarray surface. The analysis and design of the unit cell and the reflectarray antenna are carried out using the finite integration technique and the results are compared with that calculated using the finite element method for verification. The radiation characteristics of linearly-polarized reflectarray for focused beam at φ=0o, and θ=0, ±15o, ± 30o, ±45o, ±60o, and e=±75o have been investigated. The frequency bandwidth and the beamwidth of the reflectarray are increased by using modified LP-RAASL Two different methods for unit-cell element arrangements are considered. The 1-dB gain bandwidth is increased to 7.24 %. A circularly-polarized CP-RAASL for single beam and broad beam radiation characteristics have been introduced. The array produces CP in the axial direction and covers a range of 4.2 GHz.