A Broadband Single-Layer Reflectarray Antenna Based on Tightly Coupled Dipole

A novel broadband single-layer reflectarray antenna based on tightly coupled dipole is proposed in this paper. Each element consists of a tightly coupled dipole and a slot line. The phase compensation is realized by adjusting the length of the slot lines. Due to the strong coupling among neighboring elements, the unit cell is able to provide a linear phase response with sufficient phase variation range over a wide frequency range. Based on the proposed element, a reflectarray with 210 elements operating at 12-22 GHz is designed. The element distance is 3.2 mm, which is approximately 0.13λ of the lowest operating frequency. Within the designed frequency band, the radiation pattern of the reflectarray antenna is stable and the shape of main beam is not distorted or split. The simulated results show that the maximum gain at 21.5 GHz is about 21.3 dB and the maximum aperture efficiency at 21 GHz is about 46%. The cross-pol levels of the reflectarray are below -32 and -20 dB in the E- and H- planes, respectively.