A wideband 4-bit coded reflectarray antenna based on orthogonal multi-resonant log-periodic dipole pairs

A wideband 4-bit coded reflectarray antenna based on orthogonal multi-resonant log-periodic dipole pairs is proposed in this paper. The proposed reflection element employs a compact annular configuration by bending conventional log-periodic dipoles into arc-shaped segments arranged in four orthogonal quadrants. This geometry effectively excites multiple resonances through orthogonal coupling, achieving a phase range of 420° with excellent linearity across 6–9 GHz. The element is implemented on a single-layer polytetrafluoroethylene (PTFE) substrate backed by a metallic ground, with an additional air layer introduced to suppress phase fluctuations and enhance bandwidth stability. A prototype 11 × 11 reflectarray employing 4-bit phase quantization was designed, fabricated, and experimentally verified. The array is fed by a log-periodic dipole antenna to ensure phase consistency and broadband illumination. The measurement results show that from 7.0 GHz to 8.1 GHz, |S11| is less than −10 dB. The 3-dB gain bandwidth is 30% (6.3–8.5 GHz), with a peak gain of 21.1 dBi at 7.6 GHz and an aperture efficiency of 41%. The proposed design provides a compact, easily fabricated, and broadband solution suitable for next-generation communication and sensing systems.